taxonID	type	description	language	source
03B887B7A466FFFAE983FBBBFDD99D41.taxon	description	(Fig. 2 a – c)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A466FFFAE983FBBBFDD99D41.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 150, stolonal colony up to 1 mm high, with two polyps, on Eudendrium scotti Puce, Cerrano & Bavestrello, 2002.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A466FFFAE983FBBBFDD99D41.taxon	discussion	Remarks. In spite of being scarce, our material perfectly agrees with the description of the syntypes examined by Peña Cantero (2015), including the slightly-capitate appearance of tentacles (Fig. 2 c), which has been considered as the diagnostic trait of the species (see Schuchert 2007). Cnidome consisting in microbasic euryteles [range 7.5 – 9 x 5.0 – 5.5 µm, mean 8.6 ± 0.5 x 5.2 ± 0.3 µm (n = 21)] and desmonemes [range 4.5 – 5.0 x 3.0 – 3.5 µm, mean 4.7 ± 0.4 x 3.3 ± 0.3 µm (n = 16)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A466FFFAE983FBBBFDD99D41.taxon	biology_ecology	Ecology and distribution. Previously found at depths between 231 (Peña Cantero 2017) and 527 m (Peña Cantero 2014 a); present material at 710 – 758 m. Hitherto considered as endemic of East Antarctica (Peña Cantero 2014 a); present finding, the fourth report of the species, and the first for both the Weddell Sea and West Antarctica, points to a circum-Antarctic distribution.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A466FFFBE983F97CFAEB9CB2.taxon	description	(Fig. 2 d – e)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A466FFFBE983F97CFAEB9CB2.taxon	materials_examined	Material examined. ANT XVII / 3: 111 - 9, one stem, c. 5 mm high, with gonophores; 111 - 19, some stems, up to 8 mm high, on Schizotricha unifurcata Allman, 1883 and Symplectoscyphus weddelli Peña Cantero, Svoboda & Vervoort, 2002, with gonophores; ANT XXI / 2: PS 65 / 39, some stems, up to 3 mm high, on Symplectoscyphus exochus Blanco, 1982; PS 65 / 248, some stems, up to 10 mm high, on Halecium incertus Naumov & Stepanjants, 1962, Stegella lobata (Vanhöffen, 1910) and Symplectoscyphus curvatus (Jäderholm, 1917), with gonophores; PS 65 / 280, few stems, up to 3 mm high; PS 65 / 336, one stem, c. 3 mm high, on Symplectoscyphus glacialis (Jäderholm, 1904).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A466FFFBE983F97CFAEB9CB2.taxon	discussion	Remarks. Despite being abundant and fertile, the material examined does not agree with any of the bougainvillids reported from Antarctic waters. It has great resemblance with the syntypes of Bougainvillia macloviana Lesson, 1830, re-described by Peña Cantero (2015), in colony and polyp shape, presence of pseudohydrotheca (Fig. 2 d), and type and size of nematocysts (see below). However, the present material has clearly identifiable fixed sporosacs (Fig. 2 e), with up to seven eggs, that arise from a large perisarc cup which rim is not well defined. In contrast, B. macloviana produces free medusae, and the gonophores originate from a welldefined, smaller, cup-shaped pedicel of perisarc (Peña Cantero 2015, p. 373). Cnidome composed by heteronemes [range 5.5 – 7.0 x 3.5 – 4.0 µm, mean 6.2 ± 0.4 x 3.6 ± 0.2 µm (n = 29)] and desmonemes [range 3.0 – 3.5 x 2.0 – 2.5 µm, mean 3.3 ± 0.3 x 2.3 ± 0.3 µm (n = 24)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A466FFFBE983F97CFAEB9CB2.taxon	biology_ecology	Ecology and distribution. Material examined collected at depths from 62 to 287 m off Cape Norvegia.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A464FFF8E983FF31FE239C10.taxon	description	(Fig. 2 f – i)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A464FFF8E983FF31FE239C10.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 31, some polyps, up to 4 mm high, on Oswaldella terranovae Peña Cantero & Vervoort, 1996 and Antarctoscyphus grandis (Blanco, 1977); 48 - 33, numerous polyps, up to 7 mm high, on Sc. unifurcata, O. terranovae and Tubularia sp. 2, with gonophores; 48 - 36, some polyps, up to 3 mm high, on O. terranovae, with gonophores; 48 - 50, several polyps, up to 10 mm high, on Schizotricha nana Peña Cantero, Svoboda & Vervoort, 1996 and Campanularia hicksoni Totton, 1930; 48 - 194, some polyps, up to 3 mm high, on C. hicksoni and Sc. nana, with gonophores; 48 - 220, numerous polyps, up to 5 mm high, on Sc. nana, Sy. exochus and Symplectoscyphus anae Peña Cantero, Svoboda & Vervoort, 2002, with gonophores; 48 - 222, several polyps, up to 4 mm high, on Eudendrium generale von Lendenfeld, 1885, with gonophores; 48 - 223, some polyps, up to 3 mm high, on Sc. nana; ANT XVII / 3: 111 - 5, some polyps, up to 5 mm high, on C. hicksoni and O. terranovae, with gonophores; 111 - 6, some polyps, up to 5 mm high, on Sy. exochus and C. hicksoni, with gonophores; 111 - 7, few polyps, up to 6 mm high, on O. terranovae and Tubularia longstaffi Hickson & Gravely, 1907, with gonophores; 111 - 9, numerous polyps, up to 15 mm high, on polychaete tube, A. grandis, E. generale, Zyzzyzus parvula (Hickson & Gravely, 1907), O. terranovae, Sy. weddelli, Sc. unifurcata and T. longstaffi, with gonophores; 111 - 18, numerous polyps, up to 5 mm high, on Billardia subrufa (Jäderholm, 1904), C. hicksoni, Halecium interpolatum Ritchie, 1907, O. terranovae, Sc. nana, Sy. weddelli and Tubularia sp. 1, with gonophores; ANT XXI / 2: PS 65 / 39, few polyps, up to 6 mm high, on Sy. exochus, with gonophores; PS 65 / 121, few polyps, up to 3 mm high, on Sc. nana; PS 65 / 248, some polyps, up to 2 mm high, on Sy. curvatus and octocoral; PS 65 / 276, numerous polyps, up to 5 mm high, on bryozoan, Staurotheca vanhoeffeni (Peña Cantero & García Carrascosa, 1994), Staurotheca glomulosa Peña Cantero, Svoboda & Vervoort, 1997 and Symplectoscyphus vanhoeffeni Totton, 1930, with gonophores; PS 65 / 278, some polyps, up to 5 mm high, on Antarctoscyphus elongatus (Jäderholm, 1904), Halecium secundum Jäderholm, 1904 and sponge; PS 65 / 279, few polyps, up to 3 mm high, on B. subrufa; PS 65 / 280, some polyps, up to 3 mm high, on bryozoan; PS 65 / 281, few polyps, up to 3 mm high, on O. terranovae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A464FFF8E983FF31FE239C10.taxon	discussion	Remarks. The analysis of some extraordinarily well preserved reproductive colonies allowed us to confirm the presence of a distinct pseudohydrotheca, as a thin layer of perisarc, reaching the base of tentacles, but not covering them (Fig. 2 g), as noticed by Hickson & Gravely (1907) in the original description, and by other authors (Naumov & Stepanjants 1972). In contrast, according to Peña Cantero (2015: 378), “ the perisarc sheet covering the polyp body is totally inconspicuous ” in the type material he examined. Sampling procedures could strongly damage or even remove this delicate structure, and this could be the reason, in this specific case, of discrepancies among different authors’ observations. Hickson & Gravely (1907) provided a detailed description of the gonophores of R. antarcticum (as Perigonimus antarcticus). However, these authors employed a terminology commonly used with reduced medusae (i. e. criptomedusoids or eumedusoids), therefore causing some misperception about the nature of the gonophore. According to the figures by Hickson & Gravely (1907) and our own observations while dissecting the gonophores (Fig. 2 h), the gonosome of R. antarcticum can be recognized as fixed sporosacs with confidence, in agreement with the diagnosis of the genus (Bouillon et al. 2006). Cnidome composed by microbasic euryteles [range 6.5 – 8.0 x 4.0 – 4.5 µm, mean 7.4 ± 0.5 x 4.4 ± 0.2 µm (n = 22)] and desmonemes [range 5.0 – 6.0 x 3.0 – 3.5 µm, mean 5.7 ± 0.3 x 3.3 ± 0.3 µm (n = 16)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A464FFF8E983FF31FE239C10.taxon	biology_ecology	Ecology and distribution. Previously found between the tidal level (Hickson & Gravely 1907, as Perigonimus antarcticus) and 450 m (Totton 1930, as Gravelya antarctica); present material was collected from 62 to 287 m. In agreement with Peña Cantero et al. (2013) and Peña Cantero (2014 a), a careful re-examination of the abundant records is needed in order to assign a pattern of distribution; for now, R. antarcticum can be tentatively considered as a species with an Antarctic-Kerguélen distribution. In spite of being a widely reported species in the whole Southern Ocean, its presence in the Weddell Sea sector had not been confirmed; the first evidence comes from the present study.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A465FFF9E983FECFFB4A98C4.taxon	description	(Fig. 3 g)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A465FFF9E983FECFFB4A98C4.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 31, one colony, c. 15 mm high, on O. terranovae and Tubularia sp. 1; 48 - 77, one colony, c. 15 mm high, with female gonophores; 48 - 197, one colony, c. 50 mm high; 48 - 276, one colony, 20 mm high, on B. subrufa; ANT XVII / 3: 111 - 19, one colony, c. 4 mm high, on H. interpolatum; ANT XXI / 2: PS 65 / 292, one colony, c. 7 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A465FFF9E983FECFFB4A98C4.taxon	discussion	Remarks. Non-reproductive material was attributed based on the cnidome, consisting of microbasic euryteles of only one size category [range 7.0 – 8.0 x 1.5 – 2.5 µm, mean 7.8 ± 0.3 x 2.3 ± 0.3 µm (n = 23)], in agreement with previous material examined by Peña Cantero & Gili (2006) and Peña Cantero & Vervoort (2009). In the material examined here, unlike previous reports of the species (e. g. Puce et al. 2002), the female gonophores originated from partially atrophied hydranths with a reduced number of tentacles (Fig. 3 g), probably due to the complete maturation of the gonozooid, as known to occur in other species of the genus, a process known as reproductive exhaustion (see Schuchert 2008 b).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A465FFF9E983FECFFB4A98C4.taxon	biology_ecology	Ecology and distribution. In Antarctic waters, the species is known from depths between 240 (Peña Cantero & Vervoort 2009) and 260 m (Peña Cantero & Gili 2006); material examined collected at depths between 64 and 598 m, considerably extending its bathymetric range. Species previously reported from off South Africa, Bouvet, the Bransfield Strait area and doubtfully from Peter I Island [cf. Peña Cantero & Vervoort (2009) and literature therein]. Present contribution constitutes the first evidence of E. antarcticum from the Weddell Sea.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A465FFF9E983FBEDFD8C9D72.taxon	description	(Fig. 3 h)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A465FFF9E983FBEDFD8C9D72.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 4, one colony, c. 35 mm high; 48 - 27, one colony, c. 40 mm high, on sponge; 48 - 31, some stems, up to 20 mm high, on Tubularia sp. 2 and O. terranovae, with female gonophores; 48 - 33, several stems, up to 10 mm high, on O. terranovae and Sc. nana; ANT XVII / 3: 111 - 9, one colony, 20 m high, on T. longstaffi, with female gonophores; 111 - 18, some stems, up to 22 mm high, on Sc. nana; ANT XXI / 2: PS 65 / 251, one colony, 10 mm high; PS 65 / 281, some stems, up to 40 mm high, on Sc. nana and Symplectoscyphus cumberlandicus (Jädherholm, 1905), with female gonophores. Cnidome composed by microbasic euryteles in two size classes: large [range 13.0 – 16.0 x 5.5 – 6.5 µm, mean 14.3 ± 1.2 x 6.1 ± 0.3 µm (n = 21)] and small [range 6.5 – 7.5 x 2.0 – 3.0 µm, mean 6.8 ± 0.4 x 2.5 ± 0.4 µm (n = 17)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A465FFF9E983FBEDFD8C9D72.taxon	biology_ecology	Ecology and distribution. Previously reported at depths between 10 (Puce et al. 2002) and 702 m (Peña Cantero 2009); present material from 62 to 241 m. Australian-Antarctic species reported from East Antarctic (Peña Cantero 2009) and the Scotia Arc (Soto Àngel & Peña Cantero 2015); present finding constitutes the first evidence of E. generale from the Weddell Sea.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A465FFF9E983F9BAFB129C8D.taxon	description	(Fig. 3 i, k)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A465FFF9E983F9BAFB129C8D.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 150, one colony, c. 80 mm high, on sponge, with male gonophores; 48 - 222, one stem, c. 25 mm, on Sy. weddelli, with female gonophores; ANT XXI / 2: PS 65 / 276, few stems, up to 6 mm, on St. vanhoeffeni.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A465FFF9E983F9BAFB129C8D.taxon	discussion	Remarks. Cnidome comprising large macrobasic euryteles [range 22.0 – 24.5 x 9.0 – 10.0 µm, mean 23.3 ± 1.1 x 9.2 ± 0.4 µm (n = 20)] and small microbasic euryteles [range 8.0 – 10.5 x 3.5 – 4.5 µm, mean 8.9 ± 0.8 x 4.2 ± 0.4 µm (n = 18)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A465FFF9E983F9BAFB129C8D.taxon	biology_ecology	Ecology and distribution. Species previously reported from depths between 10 (Puce et al. 2002) and 397 m (Peña Cantero 2017); present material between 234 and 758 m depth, considerable extending its bathymetric range. Circum-Antarctic species (Peña Cantero 2009), previously unreported from the Weddell Sea.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A462FFFEE983F9B8FB679CF0.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 197, one colony, c. 60 mm high; ANT XVII / 3: 111 - 7, one colony, c. 55 mm high, on O. terranovae; 111 - 18, some stems, on Sy. anae; ANT XXI / 2: PS 65 / 174, one colony, 6 mm high, on Oswaldella erratum Peña Cantero & Vervoort, 1997; PS 65 / 175, few stems, up to 5 mm high, on B. subrufa and S. lobata; PS 65 / 251, one colony, c. 2 mm high, on O. terranovae; PS 65 / 253, one colony, c. 5 mm high, on S. lobata; PS 65 / 259, one colony, c. 40 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A462FFFEE983F9B8FB679CF0.taxon	discussion	Remarks. The bad state of preservation and the infertile condition preclude a proper identification.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A462FFFEE983F9B8FB679CF0.taxon	biology_ecology	Ecology and distribution. Material collected at depths from 62 to 417 m off Cape Norvegia.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A463FFFFE983FF77FC50986D.taxon	description	(Fig. 3 j)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A463FFFFE983FF77FC50986D.taxon	materials_examined	Material examined. ANT XXI / 2: PS 65 / 248, one colony, c. 80 mm high, with male gonophores.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A463FFFFE983FF77FC50986D.taxon	discussion	Remarks. This species is characterized by having a strongly polysiphonic stem, up to 80 mm high, with smooth perisarc. Only 8 – 9 polyps remain in the material examined. Male gonophores are mono- or bichambered, up to nine per polyp (Fig. 3 j). The cnidome consists of microbasic euryteles of two size classes: the smaller [range 10.5 – 12.0 x 5.0 – 5.5 µm, mean 11.3 ± 0.5 x 5.1 ± 0.2 µm (n = 15)], abundant on tentacles, and the larger [range 32.0 – 35.5 x 16 – 18.0 µm, mean 33.5 ± 1.4 x 17.1 ± 0.6 µm (n = 16)] are scarce on the hypostome. The present material agrees, in the shape of the colony and the size of the nematocysts, with the material described as Eudendrium sp. 1 by Peña Cantero (2009) and reported anew by Peña Cantero (2014 a). As stated by this author, the material could be conspecific with Eudendrium cyathiferum Jäderholm, 1904, but the cnidome of Jäderholm’s species remains unknown and further investigations are needed regarding this issue.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A463FFFFE983FF77FC50986D.taxon	biology_ecology	Ecology and distribution. Material presumably belonging to this species reported at depths between 103 (Peña Cantero 2009, as Eudendrium sp.) and 699 m (Peña Cantero 2014 a, as Eudendrium sp. 1); present material at 286 – 287 m. Previously known from the Balleny Islands (Peña Cantero 2009) and Queen Mary Coast (Peña Cantero 2014 a), in East Antarctica. Present contribution constitutes the first evidence of the species from both the Weddell Sea and West Antarctica, pointing to circum-Antarctic distribution.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A463FFFFE983FC1BFE349CA9.taxon	description	(Fig. 3 a – f)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A463FFFFE983FC1BFE349CA9.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 33, some polyps, on H. interpolatum and O. terranovae, with developing gonophores; 48 - 36, numerous polyps, on O. terranovae, with developing gonophores; 48 - 39, several polyps, on dead octocoral, with developing gonophores; 48 - 210, numerous polyps, on O. terranovae, with developing gonophores; 48 - 220, several polyps, on Sc. nana, with developing gonophores; 48 - 264, several polyps, on dead octocoral, with developing gonophores; ANT XVII / 3: 111 - 5, numerous polyps, on O. terranovae, with mature gonophores; 111 - 7, numerous polyps, on dead octocoral, O. terranovae and T. longstaffi, with mature gonophores; 111 - 9, numerous polyps, on Sc. unifurcata and T. longstaffi, with mature gonophores; 111 - 18, numerous polyps, on O. terranovae, with mature gonophores; ANT XXI / 2: PS 65 / 248, few polyps, on Eudendrium sp. 2, with developing gonophores; PS 65 / 281, several polyps, on O. terranovae, with developing gonophores.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A463FFFFE983FC1BFE349CA9.taxon	discussion	Remarks. The material examined here entirely coincides with the re-description of the type-series of H. dendritica provided by Peña Cantero (2015), including the presence of erect stems, dwarf gonophores (Fig. 3 e), and dactylozooids (Fig. 3 f). Hydractinia dendritica seems to have different growing strategies depending on the substrate on which it develops, as it has already been reported for other congeneric (Schuchert 2008 a). In the material examined, some sections of the same colony (or whole colonies) develop sharp spines when gastrozooids and dactyolozooids are not yet developed or are proportionally less abundant (Fig. 3 c), while other portions (or colonies) are almost deprived of spines but have abundant gastrozooids, and some dactylozooids (c. one dactylozooid per 10 – 20 gastrozooids). The fully mature colony, where gonozooids carrying gonophores are found, have a sort of perisarcal wall joining spines, as a kind of “ room divider ”, which could act as an extra-protection for the reproductive polyps (Fig. 3 b, e). All this different growing morphologies can be observed in the same colony, and we suggest they correspond either to differences in the substrate used or to ontogenetic changes.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A463FFFFE983FC1BFE349CA9.taxon	biology_ecology	Ecology and distribution. The species had been found once, in McMurdo Sound (Ross Sea), at a depth of 18 m (Hickson & Gravely 1907); our material was collected from several locations in the Weddell Sea, at depths between 62 and 473 m, growing on different substrates (see Tab. 3). Present contribution constitutes the second report of the species, and the first evidence from both the Weddell Sea and West Antarctica, pointing to a circum- Antarctic distribution.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A460FFFCE983FF77FAC69AF9.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 34, few polyps, on O. terranovae; ANT XVII / 3: 111 - 9, few polyps, on Z. parvula; ANT XXI / 2: PS 65 / 251, few polyps, on S. lobata.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A460FFFCE983FF77FAC69AF9.taxon	discussion	Remarks. The scarce and non-reproductive state of the material examined prevent us from attributing a specific epithet.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A460FFFCE983FF77FAC69AF9.taxon	biology_ecology	Ecology and distribution. Material collected at depths from 62 to 146 m, in the vicinity of Cape Norvegia.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A460FFFCE983FD87FE739C38.taxon	description	(Fig. 4 a – i)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A460FFFCE983FD87FE739C38.taxon	materials_examined	Material examined. ANT XVII / 3: 111 - 5, few stems, up to 45 mm high, on O. terranovae; 111 - 7, some stems, up to 40 mm high, with developing gonophores; 111 - 9, some stems, up to 110 mm, with mature gonophores.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A460FFFCE983FD87FE739C38.taxon	discussion	Remarks. The specimens examined here concurs with all the diagnostic features mentioned in the redescription of the type material of T. longstaffi by Peña Cantero (2017): yellow stems, in entwined clusters, tube diameter increasing distally (Fig. 4 a), with transversal ridges; polyps large, up to 5 x 5 mm, with an oral crown of 29 – 37 tentacles and an aboral one of 12 – 19 tentacles; type and size of nematocysts, and gonophores as cryptomedusoids (Fig. 4 d, g – h). Additional knowledge regarding sexual dimorphism and early developmental stages is drawn from the present study. Male blastostyles elongate, c. 4 mm long and with up to 17 stalked gonophores as cryptomedusoids (Fig. 4 c). Gonophore maturity increasing distally: recently formed gonophores located proximally, spherical, c. 300 µm in diameter, and completely filled with spermatogenic tissue (reddish in preserved specimens); mid-term gonophores, c. 600 µm in diameter, filled for 2 / 3 to 3 / 4 with spermatogenic tissue, with 4 – 5 rudimentary tentacular bulbs and slightly protruded aperture (Fig. 4 c); fully grown male gonophores located distally, spherical, c. 1 mm in diameter, almost completely filled with whitish sperm cells between aperture and spermatogenic tissue, rudimentary tentacular bulbs difficult to appreciate at this stage (Fig. 4 d). Female blastostyles elongate, up to 7 mm long, and with up to 11 stalked gonophores as cryptomedusoids, fully matured ones scattered along the blastostyle (Fig. 4 f). Developing gonophores sphaerical, c. 250 – 600 µm; fully grown female gonophores oblong in lateral view, c. 1.5 mm wide x 1 mm high, with a digitiform process running on proximal section, with 4 – 5 rudimentary tentacular bulbs, and with up to four actinulae, of which 2 – 3 developing and 1 – 2 mature (Fig. 4 g – h). Actinula resembling a Tubularia polyp, with 10 elongate aboral tentacles and four short oral ones. Basal section dense, with two constrictions, one at the base of aboral tentacles, the other at the basal fourth, delimiting a disc. Basal disc with radial grooves, probably with adhesive function (Fig. 4 i). Cnidome composed by small stenoteles [range 9.0 – 11.0 x 7.0 – 8.5 µm, mean 10.1 ± 0.7 x 7.8 ± 0.6 µm (n = 18)], large stenoteles [range 14.0 – 15.5 x 10.0 – 12.5 µm, mean 14.4 ± 0.4 x 10.7 ± 0.7 µm (n = 17)], tear-shaped haplonemes [range 13.5 – 16.5 x 4.0 – 5.5 µm, mean 14.9 ± 1.1 x 4.9 ± 0.6 µm (n = 16)], rounded haplonemes [range 15.5 – 16.5 x 10.0 – 11.5 µm, mean 16.0 ± 0.5 x 10.9 ± 0.5 µm (n = 15)] and desmonemes [range 5.5 – 7.0 x 4.0 – 6.0 µm, mean 6.4 ± 0.6 x 4.8 ± 0.6 µm (n = 16)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A460FFFCE983FD87FE739C38.taxon	biology_ecology	Ecology and distribution. Tubularia longstaffi was only known from the Ross Sea (Hickson & Gravely 1907; Peña Cantero 2017), reported at depths between 222 and 630 m (Peña Cantero 2017); present material was collected at 62 – 67 m depth, in the vicinity of Cape Norvegia. This constitutes the third record of the species, and the first evidence from both the Weddell Sea and West Antarctica. We tentatively assign a circum-Antarctic distribution to T. longstaffi.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47EFFE2E983FD3AFD049C12.taxon	description	(Fig. 5 a – h)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47EFFE2E983FD3AFD049C12.taxon	materials_examined	Material examined. ANT XVII / 3: 111 - 9, numerous polyps, up to 45 mm high, on E. generale, H. interpolatum, Sc. unifurcata and T. longstaffi, with mature gonophores; 111 - 18, a single polyp, c. 1 mm high, on Lafoea dumosa (Fleming, 1820).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47EFFE2E983FD3AFD049C12.taxon	discussion	Remarks. As also mentioned by Svoboda & Stepanjants (2001), many juveniles have been observed sharing substrate with adults, pointing to a gregarious habit, and putatively restricted dispersal capabilities. Juvenile specimens, especially the youngest ones, have slightly capitate aboral tentacles (Fig. 5 a), which is in agreement with the genus diagnoses by Campos et al. (2007). Originally described from the Ross Sea as Lampra parvula Hickson & Gravely, 1907, the species has had a complicated taxonomical history, being re-allocated in several genera, even belonging to different families. It was considered as Corymorpha by Stepanjants (1972), and later re-allocated in Lampra by Stepanjants & Svoboda (1999). Svoboda & Stepanjants (2001) included it in the reestablished genus Monocaulus. Nowadays, after the revision of the genus Zyzzyzus by Campos et al. (2007), included within Tubulariidae, the species is considered as a member of this genus (Schuchert 2018). Svoboda & Stepanjants (2001) re-described the syntypes of Z. parvula and provided a detailed account on new material from the Weddell Sea. However, the authors pointed out, based on in situ photographs from the Weddell Sea (Svoboda & Stepanjants 2001: 57), that living specimens are white, but reddish-orange after preservation. We disagree with that assumption. In situ photographs by Brueggeman (1998) referable to Z. parvula show deep-red to brown polyps, with a pale-orange basal section, coloration similar to that found in preserved specimens. Therefore, those white specimens mentioned by Svoboda & Stepanjants (2001) could actually correspond to an undescribed species. Material examined here entirely agrees with the description given by Svoboda & Stepanjants (2001), as well as with the original description by Hickson & Gravely (1907). Unfortunately previous authors did not provide any information about the type and size of the nematocysts. Given that the present study constitutes the first account on the cnidome, it would be necessary to compare present data with the type series and the material studied by Svoboda & Stepanjants (2001) to put in order the existent information on the species. Cnidome comprising small stenoteles [range 10.0 – 11.5 x 8.0 – 9.5 µm, mean 10.9 ± 0.4 x 8.8 ± 0.4 µm (n = 19)], large stenoteles [range 15.0 – 16.0 x 10.0 – 10.5 µm, mean 15.4 ± 0.4 x 10.1 ± 0.2 µm (n = 14)] and desmonemes [range 6.0 – 6.5 x 5.0 – 6.0 µm, mean 6.2 ± 0.2 x 5.9 ± 0.3 µm (n = 15)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47EFFE2E983FD3AFD049C12.taxon	biology_ecology	Ecology and distribution. Previously reported at depths from 3 (Stepanjants 1979, as Corymorpha parvula) to 440 m (Svoboda & Stepanjants 2001, as Monocaulus parvula); present material from 62 to 105 m. Species with circum-Antarctic distribution (Stepanjants 1979).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47FFFE0E983F8C2FE7A9823.taxon	description	(Fig. 5 i – l)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47FFFE0E983F8C2FE7A9823.taxon	materials_examined	Material examined. ANT XVII / 3: 111 - 9, few polyps, up to 80 mm high, on gravel, with mature gonophores; ANT XXI / 2: PS 65 / 253, few polyps, up to 80 mm high, with developing gonophores; PS 65 / 280, few polyps, up to 140 mm high, with mature gonophores.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47FFFE0E983F8C2FE7A9823.taxon	discussion	Remarks. Similarly to Z. parvula, Corymorpha microrhiza was first described as Lampra microrhiza (Hickson & Gravely, 1907), and then allocated within Corymorpha by Stepanjants (1972), re-allocated within Lampra by Stepanjants & Svoboda (1999), and in Monocaulus by Svoboda & Stepanjants (2001). However, the species is now considered to belong to Corymorpha (Vervoort 2009). Svoboda & Stepanjants (2001) provided a detailed description of the syntypes and additional material from the Weddell Sea. Specimens examined here concur in every aspect, but for the presence of branched blastostyles, although exclusively observed in large and mature specimens (Fig. 5 j). The original description by Hickson & Gravely (1907) refers branched blastostyles, but Svoboda & Stepanjants (2001) were not able to determine this character in the type material. This discrepancy could be attributed either to putative sexual dimorphism or to the fact that the material examined by these authors was not completely developed. Cnidome information was not given in previous descriptions. Therefore, until the analysis of the cnidome in the type series, none of the records can be ascribed with confidence to C. microrhiza. Cnidome consisting of stenoteles [range 11.0 – 13.0 x 8.0 – 11.0 µm, mean 11.9 ± 0.8 x 9.9 ± 0.9 µm (n = 15)], rounded haplonemes [range 16.0 – 17.5 x 13.5 – 14.5 µm, mean 17.0 ± 0.5 x 14.1 ± 0.3 µm (n = 15)] and desmonemes [range 7.0 – 7.5 x 6.5 – 7.5 µm, mean 7.3 ± 0.3 x 7.1 ± 0.3 µm (n = 15)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47FFFE0E983F8C2FE7A9823.taxon	biology_ecology	Ecology and distribution. Species previously known from 237 to 629 m (Svoboda & Stepanjants 2001, as Monocaulus microrhiza); present material collected from 62 to 309 m. Little-recorded species, only known from the Ross Sea (Hickson & Gravely 1907, as Lampra microrhiza) and the Weddell Sea (Svoboda & Stepanjants 2001). Probably circum-Antarctic distribution (Svoboda & Stepanjants 2001). Present contribution represents the third record of the species.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47CFFE0E983FBD3FAB79D81.taxon	description	(Fig. 2 j)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47CFFE0E983FBD3FAB79D81.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 210, a single polyp, c. 3 mm high; ANT XXI / 2: PS 65 / 248, a single polyp, c. 2 mm high, on H. incertus.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47CFFE0E983FBD3FAB79D81.taxon	discussion	Remarks. Aside from Sarsia medelae Gili, López-González & Bouillon, 2006, a non-parasitic mesobiont inhabiting calcaxonian gorgonians in the Weddell Sea (Gili et al. 2006), very few reports of the family Corynidae exist for Antarctic waters, most of which could not be assigned to species level with enough solid grounds. Hickson & Gravely (1907) mentioned an undeterminable immature Corynidae from McMurdo Sound (Ross Sea). Later, Stepanjants (1979) reported Sarsia tubulosa (M. Sars, 1835) (as Coryne tubulosa) from the Davis Sea, although her Antarctic material was infertile. Recently, Peña Cantero et al. (2013) described the early formation of tetraradial canals on reared polyps under laboratory conditions, which let them to assign their material to genus Sarsia with confidence, although no species could be attributed. These authors pointed out that their material might be conspecific with those previous records mentioned above. Material examined here might be also conspecific, but the absence of gonophores precludes a proper assignment even at genus level. Further research is needed regarding the corynids from the Southern Ocean.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47CFFE0E983FBD3FAB79D81.taxon	biology_ecology	Ecology and distribution. Similar specimens were found at depths between three (Stepanjants 1979, as Coryne tubulosa) and 40 m (Peña Cantero et al. 2013, as Sarsia sp.); present material collected from 67 – 287 m. All the previous records of Sarsia sp. originate from East Antarctica (see Peña Cantero et al. 2013). Present finding constitutes the first evidence of this undetermined corynid from West Antarctica and the Weddell Sea.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47DFFE1E983FA1BFAEF9D9D.taxon	description	(Fig. 6 a – b)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47DFFE1E983FA1BFAEF9D9D.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 77, two stems, up to 110 mm high, on sponge and octocoral; 48 - 197, one colony, 60 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47DFFE1E983FA1BFAEF9D9D.taxon	biology_ecology	Ecology and distribution. Reported from 85 (Peña Cantero 2010, as Acryptolaria sp.) to 728 m (Peña Cantero 2014 a); present material collected between 341 and 416 m. Circum-Antarctic species (Peña Cantero 2014 a).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47DFFE1E983FF77FAEA9F9C.taxon	description	(Fig. 4 j – o)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47DFFE1E983FF77FAEA9F9C.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 31, a single polyp, c. 3 mm high, on O. terranovae; ANT XVII / 3: 111 - 9, numerous polyps, up to 5 mm high, on T. longstaffi and E. generale.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47DFFE1E983FF77FAEA9F9C.taxon	discussion	Remarks. According to Peña Cantero et al. (2013), Z. hicksoni is conspecific with Corynidae Species B Hickson & Gravely, 1907. The species was later described as Gemmaria hicksoni Stepanjants, 1972. As previously noted by Hickson & Gravely (1907), polyps examined here are provided with hydrorhizal filaments which anchor them to the substrate (Fig. 4 l). Additionally, we have observed some large specimens with linear clusters of 3 – 5 tentacles, being the central one larger (Fig. 4 n). These two characteristics are diagnostic features of the genus Monocoryne Broch, 1910 (Fam. Candelabridae Stechow, 1921) according to Stepanjants et al. (2003). Conversely, there are no Zanclea species with those characters (cf. Bouillon et al. 2006). According to Stepanjants et al. (2003), the tentacles of Monocoryne sp. Stepanjants, 1979 are irregularly distributed, and can be either solitary or arranged in groups of three, being one larger (Stepanjants et al. 2003: 104). Among the several polyps observed, some certainly resemble a zancleid (Fig. 4 k), while the largest ones have more affinities with Monocoryne (Fig. 4 n – o). Early-developing polyps are also present among the material examined (Fig. 4 j). The great morphological variability observed here, the very few available polyps examined by previous authors, and the lack of mediumsized specimens could be the reason why Stepanjants (1979) described two different species (i. e. Gemmaria hicksoni and Monocoryne sp.). Finally, the type and size of the nematocysts of Z. hicksoni obtained by Peña Cantero et al. (2013), of Monocoryne sp. by Stepanjants et al. (2003), and of the present material are almost identical. Therefore, Z. hicksoni might be conspecific with Monocoryne sp. described by Stepanjants (1979) and Stepanjants et al. (2003), with subsequent family and genus re-allocation. However, due to the reproductive structures of Z. hicksoni are still unknown, further evidence is needed to confirm its true identity. Cnidome composed by small stenoteles [range 8.5 – 11.0 x 6.5 – 8.0 µm, mean 9.6 ± 0.8 x 7.1 ± 0.4 µm (n = 15)], large stenoteles [range 13.0 – 17.0 x 11.0 – 14.0 µm, mean 14.9 ± 1.0 x 12.7 ± 0.7 µm (n = 15)], haplonemes (isorhiza) [range 14.0 – 18.0 x 4.5 – 7.0 µm, mean 16.7 ± 1.4 x 5.7 ± 0.7 µm (n = 14)] and desmonemes [range 5.0 – 8.5 x 4.5 – 5.5 µm, mean 6.9 ± 0.8 x 5.1 ± 0.3 µm (n = 17)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47DFFE1E983FF77FAEA9F9C.taxon	biology_ecology	Ecology and distribution. Previously found at depths from 12 (Peña Cantero et al. 2013) to 183 m (Hickson & Gravely 1907, as Corynidae Species B); present material was collected at 62 – 64 m. All previous records were restricted to East Antarctica (see Peña Cantero et al. 2013); present study confirms its occurrence in West Antarctica and constitutes the first record from the Weddell Sea, pointing to a circum-Antarctic distribution.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47DFFE7E983F89CFB869A1B.taxon	description	(Fig. 6 c – f)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47DFFE7E983F89CFB869A1B.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 5, numerous hydrothecae, on S. lobata, with coppinia; ANT XVII / 3: 111 - 9, several hydrothecae, on S. lobata, with coppinia; ANT XXI / 2: PS 65 / 276, numerous hydrothecae, on St. vanhoeffeni, with coppinia.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47DFFE7E983F89CFB869A1B.taxon	discussion	Remarks. Cnidome comprising large microbasic mastigophores [range 10.0 – 12.0 x 4.0 – 4.5 µm, mean 10.9 ± 0.8 x 4.1 ± 0.2 µm (n = 11)] and small microbasic euryteles [range 5.5 – 6.5 x 2.5 – 3.0 µm, mean 6.1 ± 0.3 x 2.8 ± 0.3 µm (n = 18)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47DFFE7E983F89CFB869A1B.taxon	biology_ecology	Ecology and distribution. Species previously reported in Antarctic waters at depths from 42 (Stepanjants 1979) to 1658 m (Peña Cantero in press); present material from 62 to 277 m. Species known from all over Antarctic waters (Peña Cantero et al. 2004) and South Africa (Millard 1964, 1975).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47BFFE7E983FBF4FDAE9D78.taxon	description	(Fig. 6 h)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47BFFE7E983FBF4FDAE9D78.taxon	materials_examined	Material examined. ANT XXI / 2: PS 65 / 39, some hydrothecae, on Sc. nana; PS 65 / 121, several hydrothecae, on Sc. nana and B. subrufa; PS 65 / 278, some hydrothecae, on A. elongatus.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47BFFE7E983FBF4FDAE9D78.taxon	discussion	Remarks. The size spectrum of both the hydrotheca and the nematocysts are in agreement with the description of the species (cf. Marques et al. 2011). However, the absence of coppinia precludes a proper identification. Cnidome composed exclusively of microbasic mastigophores [range 6.5 – 9.0 x 3.0 – 3.5 µm, mean 7.4 ± 0.7 x 3.2 ± 0.3 µm (n = 21)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47BFFE7E983FBF4FDAE9D78.taxon	biology_ecology	Ecology and distribution. Previously reported in Antarctic waters at a depth of 122 – 134 m [Peña Cantero & Gili 2006, as Filellum contortum (Nutting, 1905)]. Rare species only reported twice: from its type locality at Bouvet Island (Peña Cantero & Gili 2006) and from Gough Island, Tristan da Cunha archipelago, in the South Atlantic (Galea 2015). If confirmed, present record would constitute the first evidence of the species from both the Weddell Sea and High Antarctica.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47BFFE7E983FE57FC6C98B9.taxon	description	(Fig. 6 g)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47BFFE7E983FE57FC6C98B9.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 150, some hydrothecae, on E. scotti; 48 - 220, some hydrothecae, on Sy. exochus; 48 - 276, several hydrothecae, on Sc. nana; ANT XXI / 2: PS 65 / 166, numerous hydrothecae, on O. erratum; PS 65 / 274, numerous hydrothecae, on Staurotheca nonscripta Peña Cantero, Svoboda & Vervoort, 1997.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47BFFE7E983FE57FC6C98B9.taxon	discussion	Remarks. In spite of the absence of coppinia, the size of the hydrotheca and the size of the nematocysts perfectly agree with previous reports (Peña Cantero 2010, Peña Cantero et al. 2004, Soto Àngel & Peña Cantero 2015). However, in agreement with Peña Cantero et al. (1998), the identification of infertile material of Filellum is tentative. Cnidome consisting of large microbasic mastigophores [range 17.5 – 19.0 x 4.5 – 6.0 µm, mean 18.1 ± 0.6 x 5.4 ± 0.8 µm (n = 4)] and small microbasic euryteles [range 6.0 – 7.5 x 2.5 – 3.5 µm, mean 6.9 ± 0.4 x 2.8 ± 0.3 µm (n = 13)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47BFFE7E983FE57FC6C98B9.taxon	biology_ecology	Ecology and distribution. Previously known from 85 (Peña Cantero 2010) to 640 m (Peña Cantero et al. 2004); present material collected at depths from 236 to 758 m. Only known from Peter I Island (Peña Cantero 2010) and the Weddell Sea (Peña Cantero et al. 2004; material examined).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47BFFE4E983F9B6FB5E9991.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 4, some hydrothecae, on E. generale; 48 - 5, some hydrothecae, on sponge; 48 - 27, numerous hydrothecae, on E. generale, Halecium exaggeratum Peña Cantero, Boero & Piraino, 2013 and S. lobata; 48 - 44, several hydrothecae, on Halecium banzare Watson, 2008, S. lobata and Sy. exochus; 48 - 50, several hydrothecae, on C. hicksoni and Sc. nana; 48 - 77, numerous hydrothecae, on Halecium jaederholmi Vervoort, 1972; 48 - 168, some hydrothecae, on Sy. exochus; 48 - 194, numerous hydrothecae, on Sc. nana; 48 - 220, some hydrothecae, on C. hicksoni, H. interpolatum and Symplectoscyphus liouvillei (Billard, 1914); 48 - 222, numerous hydrothecae, on Sc. nana and Sy. weddelli; 48 - 223, numerous hydrothecae, on Sc. nana and Symplectoscyphus plectilis (Hickson & Gravely, 1907); 48 - 276, some hydrothecae, on Halecium cf. antarcticum and Sy. weddelli; ANT XVII / 3: 111 - 9, few hydrothecae, on R. antarcticum; 111 - 19, numerous hydrothecae, on H. interpolatum, L. dumosa, R. antarcticum, Sc. unifurcata, Sy. exochus, Symplectoscyphus naumovi Blanco, 1969 and Sy. weddelli; ANT XXI / 2: PS 65 / 39, numerous hydrothecae, on C. hicksoni, Sc. nana, St. glomulosa, S. lobata, Sy. exochus, Sy. glacialis and Sy. plectilis; PS 65 / 121, numerous hydrothecae, on Sy. glacialis, Sy. plectilis and the hydrorhiza of an undetermined hydroid; PS 65 / 132, numerous hydrothecae, on O. erratum; PS 65 / 166, several hydrothecae, on Sy. exochus; PS 65 / 174, several hydrothecae, on Sy. exochus; PS 65 / 175, numerous hydrothecae, on S. lobata and Sy. naumovi; PS 65 / 237, several hydrothecae, on Sy. exochus, Sy. glacialis and Sy. weddelli; PS 65 / 248, numerous hydrothecae, on H. incertus, Sy. curvatus, Sy. glacialis, Sy. plectilis and octocoral; PS 65 / 253, several hydrothecae, on S. lobata; PS 65 / 265, several hydrothecae, on Sy. glacialis; PS 65 / 274, some hydrothecae, on St. nonscripta and Sy. plectilis; PS 65 / 276, several hydrotheca on Sy. exochus and Sy. vanhoeffeni; PS 65 / 278, several hydrothecae, on H. secundum, L. dumosa and sponge; PS 65 / 292, numerous hydrothecae, on Staurotheca antarctica Hartlaub, 1904 and St. nonscripta.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47BFFE4E983F9B6FB5E9991.taxon	discussion	Remarks. Material included here comprises a huge amount of small-sized hydrothecae, with 100 - 150 µm in diameter of aperture, and provided with striae. The material could correspond, at least in part, to F. antarcticum. However, in agreement with Peña Cantero et al. (2004) and Marques et al. (2011), the small-sized Filellum from Antarctic waters are not identifiable in the absence of coppinia, and therefore it precludes a proper identification of material examined here.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A47BFFE4E983F9B6FB5E9991.taxon	biology_ecology	Ecology and distribution. Material examined was collected at depths between 62 and 598 m.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A478FFE4E983FC65FEC69DA0.taxon	description	(Fig. 6 i – j)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A478FFE4E983FC65FEC69DA0.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 50, one colony, up to 55 mm high; 48 - 194, one colony, up to 50 mm high; 48 - 276, one colony, up to 10 mm high, on Sc. nana; 48 - 297, one colony, up to 15 mm high, on B. subrufa and ascidian; ANT XVII / 3: 111 - 5, one colony, up to 35 mm high, on O. terranovae; 111 - 6, one colony, up to 40 mm high; 111 - 18, some stems, up to 40 mm high, on O. terranovae and polychaete tube; 111 - 19, one colony, up to 20 mm high, on Sc. unifurcata; ANT XXI / 2: PS 65 / 121, some stems, up to 40 mm high, on Sc. nana and Sy. curvatus; PS 65 / 278, one colony, up to 40 mm high, on H. secundum; PS 65 / 279, one colony, up to 10 mm high, on sponge.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A478FFE4E983FC65FEC69DA0.taxon	discussion	Remarks. Lafoea dumosa has been considered a cosmopolitan species with a wide range of variation in colony shape, pedicel length and hydrothecal morphology [see Schuchert (2001) for a detailed account on the taxonomic history of the species]. Some authors included Lafoea fruticosa (Sars, 1851) and Lafoea gracillima (Alder, 1856) within the synonymy of L. dumosa (e. g. Cornelius 1975; Peña Cantero et al. 2004). However, recent evidence have challenged these previous concepts. Schuchert (2001) found differences in nematocyst size between pedicellate and non-pedicellate colonies of L. dumosa, but some exceptions were noticed by the author. Moura et al. (2008) found two divergent lineages within L. dumosa, suggesting the existence of cryptic species. Finally, Calder (2012) tentatively considered L. fruticosa and L. gracillima as valid species waiting for further molecular work. Given that L. dumosa was originally described from Scotland bearing “ nearly sessile cups ” (Fleming 1828: 548; see also Cornelius 1975), the Antarctic representatives of Lafoea, often bearing long and twisted pedicels (figs 6 i – j), might belong to a different species. However, in the absence of further molecular evidence, this issue remains open.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A478FFE4E983FC65FEC69DA0.taxon	biology_ecology	Ecology and distribution. In Antarctic waters, reported from 12 (Stepanjants 1979, as Lafoea fruticosa) to 1157 m depth (Peña Cantero 2014 a); present material was collected between 65 – 417 m. Worldwide distributed, known from both East and West Antarctica (Peña Cantero et al. 2004), as well as the Scotia Arc (Soto Àngel & Peña Cantero 2015).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A478FFE5E983F8DEFF5B9BAA.taxon	description	(Fig. 6 k)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A478FFE5E983F8DEFF5B9BAA.taxon	materials_examined	Material examined. ANT XXI / 2: PS 65 / 280, stolonal colony, few hydrothecae, on bryozoan. Ecology and distribution. Previously found at depths from 40 (Stepanjants, 1979) to 460 m (Peña Cantero et al. 2004); present material collected at 191 – 228 m. Species with circum-Antarctic distribution (Peña Cantero et al. 2004).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A479FFE5E983FE5AFDF6984A.taxon	description	(Fig. 6 n)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A479FFE5E983FE5AFDF6984A.taxon	materials_examined	Material examined. ANT XV / 3: PS 65 / 77, few hydrothecae, on A. frigida.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A479FFE5E983FE5AFDF6984A.taxon	discussion	Remarks. In our material, the length of the hydrotheca is 1440 – 1600 µm, the diameter at the aperture is 411 – 431 mm, and the diameter at diaphragm 280 – 312 µm. The length of the pedicel is 115 µm. These measurements are considerably larger than those given by Peña Cantero et al. (2004), and therefore we are not entirely confident with its specific assignation.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A479FFE5E983FE5AFDF6984A.taxon	biology_ecology	Ecology and distribution. Known from depths between 92 (Peña Cantero 2008) and 722 m (Peña Cantero et al. 2004); present material came from depths between 340 and 360 m. Species with Antarctic-Patagonian distribution (Peña Cantero et al. 2004).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A479FFE5E983FBFAFA859E0E.taxon	description	(Fig. 7 a)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A479FFE5E983FBFAFA859E0E.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 77, few hydrothecae, on Halecium pseudodelicatulum Peña Cantero, 2014; ANT XVII / 3: 111 - 5, several hydrothecae, on L. dumosa and O. terranovae, with gonothecae; 111 - 9, numerous hydrothecae, on O. terranovae, T. longstaffi and polychaete tube; 111 - 18, numerous hydrothecae, on C. hicksoni, H. interpolatum, O. terranovae, Sc. nana and undeterminate hydrorhiza; ANT XXI / 2: PS 65 / 251, numerous hydrothecae, on O. terranovae; PS 65 / 281, several hydrothecae, on B. subrufa and Sy. cumberlandicus.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A479FFE5E983FBFAFA859E0E.taxon	biology_ecology	Ecology and distribution. Species reported at depths from five (Stepanjants 1979) to 701 m (Peña Cantero 2014 a); present material comes from 62 to 360 m. Pan-Antarctic species (Peña Cantero & Vervoort 2009).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A479FFEAE983F9E4FC8599FA.taxon	description	(Fig. 7 b – c)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A479FFEAE983F9E4FC8599FA.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 4, few hydrothecae, c. 4 mm high, on dead octocoral; 48 - 5, one colony, c. 90 mm high, with gonothecae, and few hydrothecae, up to 3 mm high, on Sc. unifurcata; 48 - 27, one colony, c. 60 mm high; 48 - 36, some stems, up to 20 mm high, on O. terranovae; 48 - 44, some stems, up to 40 mm high, on polychaete tube; 48 - 44, one colony, c. 75 mm high, with gonothecae; 48 - 50, one colony, c. 60 mm high, on dead octocoral; 48 - 63, one colony, c. 60 mm high, with gonothecae; 48 - 77, one colony, c. 80 mm high, and few hydrothecae, c. 3 mm high, on Sy. weddelli; 48 - 194, one hydrotheca, c. 5 mm high, on Sc. nana; 48 - 197, some stems, up to 20 mm high, on B. subrufa; 48 - 220, some stems, up to 120 mm high, on gravel and dead octocoral, with gonothecae; 48 - 276, few hydrothecae, up to 3 mm high, on Sc. nana; ANT XVII / 3: 111 - 9, one colony, c. 130 mm high, with gonothecae; 111 - 18, some hydrothecae, c. 6 mm high, on O. terranovae and Sc. nana; ANT XXI / 2: PS 65 / 39, some stems, up to 110 mm high, on Sc. nana, with gonothecae; PS 65 / 121, some stems, up to 70 mm high, on bryozoan, with gonothecae; PS 65 / 132, one colony, c. 75 mm high; PS 65 / 166, one hydrotheca, c. 2 mm high, on St. nonscripta; PS 65 / 175, some stems, up to 40 mm high, on B. subrufa and dead Oswaldella sp.; PS 65 / 237, one colony, c. 110 mm high, on Sc. nana, with gonothecae, and few hydrothecae, c. 2 mm high, on Sy. exochus; PS 65 / 248, some stems, up to 40 mm high, on octocoral and H. incertus; PS 65 / 253, one colony, c. 60 mm high, on polychaete tube, with gonothecae; PS 65 / 265, few stems, up to 5 mm high, on H. pseudodelicatulum; PS 65 / 276, one colony, c. 75 mm high, with gonothecae; PS 65 / 281, one colony, c. 90 mm high, on sponge, with developing gonothecae; PS 65 / 336, some stems, up to 30 mm high, on Sc. nana.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A479FFEAE983F9E4FC8599FA.taxon	discussion	Remarks. Specimens analyzed have been observed using a wide range of basibionts as substrate (see above). Large colonies are seen in many cases overgrowing the basibiont almost completely. Stegella lobata seems to behave as an aggressive epibiont species that uses its host to reach large size. This relationship can be described as parasitism sensu lato, in which the epibiont is detrimental to the host but is not metabolically dependent upon it (see Gili et al. 2006 and literature cited).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A479FFEAE983F9E4FC8599FA.taxon	biology_ecology	Ecology and distribution. Previously collected at depths from 10 (Naumov & Stepanjants 1972, as Stegella grandis) to 700 m (Naumov & Stepanjants 1962, as Stegella grandis); present material was obtained from 62 to 417 m. Circum-Antarctic species (Peña Cantero et al. 2004).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A476FFEAE983FC89FD379DC4.taxon	description	(Fig. 7 d)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A476FFEAE983FC89FD379DC4.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 27, several hydrothecae, on E. generale, H. exaggeratum, S. lobata, Sy. anae and Sy. glacialis; 48 - 33, several hydrothecae, on C. hicksoni and O. terranovae; 48 - 36, some hydrothecae, on O. terranovae; 48 - 39, several hydrothecae, on dead octocoral; 48 - 44, some hydrothecae, on A. elongatus, Sy. naumovi and bryozoan; 48 - 50, numerous hydrothecae, on C. hicksoni, H. secundum, Sc. nana and bryozoan; 48 - 63, some hydrothecae, on Staurotheca frigida Peña Cantero, Svoboda & Vervoort, 1997; 48 - 77, numerous hydrothecae, on H. jaederholmi; 48 - 82, numerous hydrothecae, on B. subrufa, Sy. glacialis and Staurotheca polarsterni Peña Cantero, Svoboda & Vervoort, 1997; 48 - 168, two hydrothecae, on Sy. weddelli; 48 - 220, numerous hydrothecae and erect stems, up to 2.5 mm high, on C. hicksoni, H. interpolatum, Sc. nana, Sy. exochus and Sy. plectilis; 48 - 276, several hydrothecae, on C. hicksoni, Halecium cf. antarcticum and Sc. nana; ANT XVII / 3: 111 - 7, several hydrothecae, on O. terranovae and Sy. cumberlandicus; 111 - 9, numerous hydrothecae, on A. grandis, E. generale, R. antarcticum and T. longstaffi; 111 - 19, some hydrothecae, on H. interpolatum and Tubularia sp. 1; ANT XXI / 2: PS 65 / 39, some hydrothecae, on Sc. nana, Sy. exochus and polychaete tube, with gonothecae; PS 65 / 121, few hydrothecae, on Antarctoscyphus spiralis (Hickson & Gravely, 1907); PS 65 / 132, some hydrothecae, on B. subrufa; PS 65 / 175, three hydrothecae, on A. elongatus; PS 65 / 237, several hydrothecae, on Halecium cf. antarcticum, Sc. nana and Sy. glacialis; PS 65 / 248, one hydrotheca, on indeterminate hydrorhiza; PS 65 / 274, several hydrothecae, on St. nonscripta; PS 65 / 278, few hydrothecae, on H. secundum and sponge; PS 65 / 281, some hydrothecae, on Sy. curvatus; PS 65 / 292, several hydrothecae, on dead octocoral and bryozoan; PS 65 / 336, some hydrothecae, on Staurotheca pachyclada (Jäderholm, 1904).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A476FFEAE983FC89FD379DC4.taxon	biology_ecology	Ecology and distribution. Species previously reported from the low tide (Billard 1914, as Campanulina belgicae) to 779 m depth (Peña Cantero 2014 a); present material was collected from 62 to 598 m. Probably a Pan- Antarctic species (Peña Cantero et al. 2013).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A476FFE9E983F87FFDF69822.taxon	description	(Fig. 7 e – h)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A476FFE9E983F87FFDF69822.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 33, numerous hydrothecae, up to 20 mm high, on O. terranovae, with developing gonothecae; 48 - 36, numerous hydrothecae, up to 25 mm high, on O. terranovae, with developing gonothecae; 48 - 50, numerous hydrothecae, up to 20 mm high, on Sc. nana, with developing gonothecae; 48 - 72, few hydrothecae, up to 15 mm high, on St. polarsterni; 48 - 210, numerous hydrothecae, up to 25 mm high, on O. terranovae, with developing gonothecae; 48 - 220, few hydrothecae, up to 25 mm high, on Sc. nana, with developing gonothecae; 48 - 276, few hydrothecae, up to 5 mm high, on Sc. nana; ANT XVII / 3: 111 - 5, numerous hydrothecae, up to 15 mm high, on O. terranovae, with gonothecae; 111 - 6, numerous hydrothecae, up to 15 mm high, on Hydrodendron arboreum (Allman, 1888), O. terranovae and Sy. exochus, with gonothecae; 111 - 7, numerous hydrothecae, up to 15 mm high, on O. terranovae, with gonothecae; 111 - 9, several hydrothecae, up to 15 mm high, on O. terranovae and T. longstaffi, with gonothecae; 111 - 18, few hydrothecae, up to 15 mm high, on Sc. nana; 111 - 19, few hydrothecae, up to 20 mm high, on St. glomulosa and Tubularia sp. 1; ANT XXI / 2: PS 65 / 39, few hydrothecae, up to 20 mm high, on Sc. nana and St. glomulosa, with gonothecae; PS 65 / 166, few hydrothecae, up to 20 mm high, on A. elongatus; PS 65 / 237, several hydrothecae, up to 15 mm high, on Sc. nana and Sy. exochus; PS 65 / 248, few hydrothecae, up to 15 mm high, on Sy. curvatus; PS 65 / 276, few hydrothecae, up to 25 mm high, on St. glomulosa; PS 65 / 281, some hydrothecae, up to 15 mm high, on O. terranovae, St. nonscripta and Sy. cumberlandicus.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A476FFE9E983F87FFDF69822.taxon	discussion	Remarks. According to Peña Cantero et al. (2004), C. hicksoni forms large hydrothecae (2335 – 2946 mm in length and 902 – 1417 mm in diameter at aperture). However, among the abundant material examined, some smaller hydrothecae (1000 – 1800 µm) have been observed. In this regard, Totton (1930), Blanco (1984) and Peña Cantero (2017) already noted a great variability in the size of the hydrotheca, but in opinion of Peña Cantero et al. (2004), Totton’s material could be composed of two different species. A detailed examination of the stolonal hydrorhiza let us confirm that some polyps with small hydrothecae (ca. 900 – 1000 µm) are joined through the same stolon to slightly larger ones (c. 1400 – 1500 µm), which in turn are united to medium-sized ones (c. 2000 µm), and so on. Furthermore, in a few occasions we observed the pioneer polyp with remnants of the planula attachment (see Fig. 7 g), and thus, the first polyp of the colony, confirming the smaller size of the hydrotheca (c. 950 µm in length). Focussing on the size of the nematocysts, previous studies reported nematocysts of 17 – 18.5 x 4 – 4.5 µm (Peña Cantero 2013), slightly larger in Peña Cantero (2014 a): 19 – 20 x 4.5 – 5 µm. In present study, the size distribution of large microbasic mastigophores suggests a positive correlation between length of hydrotheca and mean size of these nematocysts (Fig. 8). We consider that the small polyps studied here (accordingly provided with small hydrothecae) also belong to C. hicksoni, based on the following reasons: in some occasions, small polyps have been noticed joined to larger ones; most small polyps were recorded on the same basibiont than larger ones, although the connection could not be ascertained; the large microbasic mastigophores of the smallest polyps always included at least a few large nematocysts, regardless of the mean size (see Fig. 8). We hypothesized that this ontogenetic drift could be attributed to changes in the trophic ecology of the species: larger polyps probably eat larger preys, and could need larger nematocysts. This is similar to previous findings relating prey size and nematocyst size, although this studies focused on various planktonic cnidarians. Purcell (1984) observed that siphonophores species with larger nematocyst capture larger prey. She subsequently suggested that the presence of longer threads in larger nematocysts could make them more effective in entangling prey. On the other hand, Carrette et al. (2002) evidenced profound changes in the ratio of different types of nematocysts between small and large specimens of the cubomedusa Chironex fleckeri Southcott, 1956 that are, in turn, correlated with ontogenetic drifts in its diet. Further research is needed regarding this finding, and specific future experimental design will shed more light on this issue. Cnidome (in polyps within large hydrothecae) composed by large microbasic mastigophores [range 13.5 – 20.5 x 3.5 – 4.5 µm, mean 19.3 ± 1.4 x 4.5 ± 0.2 µm (n = 56)] and small microbasic mastigohpores [range 7.5 – 9.0 x 1.5 – 2.0 µm, mean 8.2 ± 0.4 x 1.6 ± 0.1 µm (n = 27)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A476FFE9E983F87FFDF69822.taxon	biology_ecology	Ecology and distribution. Species previously reported at depths between 10 (Peña Cantero et al. 2004) and 779 m (Peña Cantero 2014 a); material examined collected from 62 to 598 m. Species with circum-Antarctic distribution (Peña Cantero et al. 2004).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A475FFE9E983FC4AFEBC9C8B.taxon	description	(Fig. 7 i – j)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A475FFE9E983FC4AFEBC9C8B.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 27, few hydrothecae, up to 6 mm high, on Sy. anae; 48 - 36, several hydrothecae, up to 5 mm high, on O. terranovae; 48 - 220, several hydrothecae, up to 6 mm high, on H. interpolatum, Sc. nana, St. glomulosa and Sy. exochus, with developing gonothecae; 48 - 222, few hydrothecae, up to 6 mm high, on Sc. nana; 48 - 223, few hydrothecae, up to 6 mm high, on Sc. nana; ANT XVII / 3: 111 - 6, few hydrothecae, up to 6 mm high, on B. subrufa; ANT XXI / 2: PS 65 / 39, few hydrothecae, up to 5 mm high, on Sc. nana and Sy. glacialis; PS 65 / 174, few hydrothecae, up to 4 mm high, on O. erratum; PS 65 / 175, few hydrothecae, up to 5 mm high, on Sy. glacialis; PS 65 / 248, few hydrothecae, up to 6 mm high, on H. incertus and St. nonscripta; PS 65 / 274, few hydrothecae, up to 5 mm high, on St. nonscripta; PS 65 / 278, few hydrothecae, up to 5 mm high, on H. secundum; PS 65 / 280, some hydrothecae, up to 7 mm high, on Sy. glacialis; PS 65 / 281, few hydrothecae, up to 7 mm high, on O. terranovae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A475FFE9E983FC4AFEBC9C8B.taxon	discussion	Remarks. Material studied here is probably conspecific with Campanularia sp. reported from several localities in the Southern Ocean by Peña Cantero (2006, 2013, 2014 a, 2017), Peña Cantero & Gili (2006) and Peña Cantero et al. (2004, 2013). The material agrees in the shape and size of hydrothecae (850 – 950 µm in length and 350 – 450 µm in diameter at aperture), as well as in nematocyst size. The species, however, has never been found with gonothecae (see Peña Cantero 2017). Material examined from XV / 3 48 – 220 has developing gonothecae (Fig. 7 j), but unfortunately they cannot be completely characterized given its incomplete maturation. In contradistinction to the young specimens of C. hicksoni, whose hydrothecae concur in shape and size to that of Campanularia sp., the range of the nematocyst size obtained for the latter is narrower, and the largest nematocysts do not reach more than 10.5 µm in length (see below). For these reasons, we prefer keeping both species as separated entities until new evidence becomes available. Cnidome composed of large microbasic mastigophores [range 9.0 – 10.5 x 1.5 – 2.0 µm, mean 9.8 ± 0.5 x 1.7 ± 0.2 µm (n = 56)] and small microbasic mastigohpores [range 6.5 – 7.5 x 1.5 – 2.0 µm, mean 7.0 ± 0.4 x 1.5 ± 0.1 µm (n = 22)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A475FFE9E983FC4AFEBC9C8B.taxon	biology_ecology	Ecology and distribution. Previously known from 15 (Peña Cantero et al. 2013) to 728 m (Peña Cantero 2014 a); present material comes from depths between 68 to 291 m. Hitherto, it has been reported from the Weddell Sea (Peña Cantero et al. 2004) and off South Shetland Islands (Peña Cantero, 2006, 2013) in west Antarctica; from Queen Mary Coast (Peña Cantero 2014 a) and the Ross Sea (Peña Cantero 2017, Peña Cantero et al. 2013) in East Antarctica; and from Bouvet Island (Peña Cantero and Gili 2006). Thus, the species can be regarded as Circum- Antarctic.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983FECAFF5B9946.taxon	description	(Fig. 9 a)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983FECAFF5B9946.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 168, mass of stems, c. 20 mm high; ANT XXI / 2: PS 65 / 292, one colony, c. 30 mm high, with male gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983FECAFF5B9946.taxon	biology_ecology	Ecology and distribution. Species collected at depths between 55 (Peña Cantero & Vervoort 2003) and 866 m (Peña Cantero in press); present material from 228 to 598 m. Circum-Antarctic species (Peña Cantero & Vervoort 2003).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983FD63FEF398E1.taxon	description	(Fig. 9 b)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983FD63FEF398E1.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 276, several stems, c. 30 mm high, on gravel; ANT XXI / 2: PS 65 / 121, mass of stems, c. 120 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983FD63FEF398E1.taxon	biology_ecology	Ecology and distribution. Species reported at depths from 82 (Totton 1930) to 1235 m (Peña Cantero in press); present material collected between 268 and 417 m. Antarctic-Kerguélen distribution (Peña Cantero & Vervoort 2003).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983FC1DFDB79EC4.taxon	description	(Fig. 9 c – d)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983FC1DFDB79EC4.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 50, mass of stems, c. 40 mm high, with male gonothecae; 48 - 63, mass of stems, c. 25 mm high, with male gonothecae; 48 - 77, mass of stems, c. 20 mm high, with female gonothecae; 48 - 189, mass of stems, c. 25 mm high, with male gonothecae; 48 - 194, mass of stems, c. 30 mm high, with male gonothecae; 48 - 220, mass of stems, c. 30 mm high, with female gonothecae; 48 - 222, mass of stems, c. 40 mm high, with male gonothecae; ANT XXI / 2: PS 65 / 121, mass of stems, c. 35 mm high, with female gonothecae; PS 65 / 166, mass of stems, c. 25 mm high, with male gonothecae; PS 65 / 248, mass of stems, c. 40 mm high, with female gonothecae; PS 65 / 274, mass of stems, c. 40 mm high, with male gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983FC1DFDB79EC4.taxon	biology_ecology	Ecology and distribution. Species known from depths between 57 (Peña Cantero & Vervoort 2003) and 647 m (Soto Àngel & Peña Cantero 2015); present material collected from 234 to 360 m. Antarctic-Kerguélen species (Peña Cantero & Vervoort 2003).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983F9E2FE7E9CAA.taxon	description	(Fig. 9 e)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983F9E2FE7E9CAA.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 70, mass of stems, c. 80 mm high; 48 - 77, mass of stems, c. 75 mm high; 48 - 150, mass of stems, c. 60 mm high, on gravel, with female gonothecae; 48 - 189, mass of stems, c. 35 mm high, with female gonothecae; 48 - 220, mass of stems, c. 65 mm high, on gravel, with female gonothecae; ANT XVII / 3: 111 - 19, two colonies, c. 30 and 60 mm high, with male and female gonothecae respectively; ANT XXI / 2: PS 65 / 39, mass of stems, c. 80 mm high, with male gonothecae; PS 65 / 245, some stems, up to 40 mm high; PS 65 / 253, some stems, up to 20 mm high; PS 65 / 274, one colony, c. 18 mm high, on bryozoan; PS 65 / 276, few stems, c. 20 mm high, with female gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A472FFEEE983F9E2FE7E9CAA.taxon	biology_ecology	Ecology and distribution. Species collected at depths between 55 (Peña Cantero & Vervoort 2003) and 1157 (Peña Cantero 2014 a); present material from 112 to 758 m. Species with circum-Antarctic distribution (Peña Cantero & Vervoort 2003).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A473FFECE983F931FE7E9BAA.taxon	description	(Fig. 9 f)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A473FFECE983F931FE7E9BAA.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 58, few stems, c. 15 mm high; 48 - 77, some stems, up to 30 mm high; ANT XXI / 2: PS 65 / 166, some stems, up to 35 mm high; PS 65 / 248, mass of stems, c. 140 mm high, with male gonothecae; PS 65 / 265, some stems, up to 40 mm high; PS 65 / 274, some stems, up to 45 mm high; PS 65 / 280, some stems, up to 40 mm high; PS 65 / 292 mass of stems, c. 75 mm high, with male gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A473FFECE983F931FE7E9BAA.taxon	biology_ecology	Ecology and distribution. Species reported at depths between 15 (Peña Cantero & Vervoort 2003) and 728 m (Peña Cantero 2014 a); material examined collected from 191 to 598 m. Antarctic-Patagonian species (Peña Cantero & Vervoort 2003).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983F934FC049C90.taxon	description	(Fig. 10 a)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983F934FC049C90.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 72, one colony, c. 65 mm high, with developing gonothecae; ANT XXI / 2: PS 65 / 121, one colony, c. 50 mm high; PS 65 / 237, one colony, 11 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983F934FC049C90.taxon	biology_ecology	Ecology and distribution. Previously reported at depths from 18 (Peña Cantero et al. 2017) to 429 m (Peña Cantero 2008); material examined comes from 230 to 274 m. Circum-Antarctic species (Peña Cantero et al. 2017); present contribution constitutes the first evidence from the Weddell Sea.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983FEC7FE7E99FD.taxon	description	(Fig. 9 g – h)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983FEC7FE7E99FD.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 77, one colony, c. 50 mm high, with female gonothecae; 48 - 154, one colony, c. 45 mm high; 48 - 220, one colony, c. 25 mm high, with female gonothecae; 48 - 222, one colony, c. 25 mm high; ANT XXI / 2: PS 65 / 237, several stems, c. 130 mm high; PS 65 / 265, several stems, c. 125 mm high, on gravel, with female gonothecae; PS 65 / 336, one colony, c. 85 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983FEC7FE7E99FD.taxon	biology_ecology	Ecology and distribution. Previously found at depths from 42 (Stepanjants 1979, as Thuiaria juncea) to 1990 m (Peña Cantero in press); present material at 267 – 583 m. Species with a circum-Antarctic distribution (Peña Cantero & Vervoort 2003).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983FD39FB4B9F28.taxon	description	(Fig. 9 k)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983FD39FB4B9F28.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 63, one colony, c. 40 mm high; 48 - 70, one colony, c. 90 mm high; 48 - 72, several stems, c. 130 mm high; 48 - 77, one colony, c. 40 mm high; 48 - 82, one colony, c. 75 mm high, on stone; 48 - 97, numerous stems, up to 110 mm high; 48 - 150, numerous stems, up to 120 mm high, on gravel, with male gonothecae; 48 - 154, numerous stems, up to 140 mm high, with female gonothecae; 48 - 197, numerous stems, up to 100 mm high; ANT XXI / 2: PS 65 / 248, several stems, up to 80 mm high; PS 65 / 253, one colony, c. 75 mm high; PS 65 / 265, one colony, c. 130 mm high, with female gonothecae; PS 65 / 274, one colony, c. 85 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983FD39FB4B9F28.taxon	biology_ecology	Ecology and distribution. Previously collected at depths between 181 and 1030 m (Peña Cantero et al. 1997 b); present material from 230 to 758 m. Circum-Antarctic species (Peña Cantero et al. 1997 b).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983FB46FEDA9D7B.taxon	description	(Fig. 9 i – j)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983FB46FEDA9D7B.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 220, one colony, c. 65 mm high, on gravel; ANT XXI / 2: PS 65 / 248, one colony, c. 120 mm high; PS 65 / 259, one colony, c. 100 mm high, on gravel, with female gonothecae; PS 65 / 265, one colony, c. 230 mm high; PS 65 / 276, one colony, c. 110 mm high, on stone, with female gonothecae; PS 65 / 278, one colony, c. 70 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A470FFECE983FB46FEDA9D7B.taxon	biology_ecology	Ecology and distribution. Species collected at depths from 92 (Peña Cantero 2008) to 527 m (Peña Cantero 2014 a); present material at depths between 119 and 333 m. Circum-Antarctic distribution (Peña Cantero & García Carrascosa 1995).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A471FFD2E983F9B4FDE29BAA.taxon	description	(Fig. 10 b – d)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A471FFD2E983F9B4FDE29BAA.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 44, one colony, c. 50 mm high; 48 - 63, one colony, c. 70 mm high; 48 - 72, one colony, c. 15 mm high; 48 - 77, one colony, c. 75 mm high; ANT XVII / 3: 111 - 18, one colony, c. 35 mm high, on O. terranovae; ANT XXI / 2: PS 65 / 132, one colony, c. 85 mm high; PS 65 / 148, one colony, c. 55 mm high; PS 65 / 166, one colony, c. 65 mm high; PS 65 / 174, one colony, c. 105 mm high; PS 65 / 175, some stems, c. 60, 75 and 80 mm high; PS 65 / 237, one colony, c. 95 mm high, with developing gonothecae; PS 65 / 278, one colony, c. 65 mm high; PS 65 / 279, one colony, c. 100 mm high; PS 65 / 280, few stems, c. 10 mm high; PS 65 / 281, few stems, up to 15 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A471FFD2E983F9B4FDE29BAA.taxon	biology_ecology	Ecology and distribution. Species reported at depths between 10 (Naumov & Stepanjants 1972, as	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD2E983FEC7FCA29921.taxon	description	(Fig. 10 e – g)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD2E983FEC7FCA29921.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 31, one colony, c. 50 mm high, with developing gonothecae; ANT XVII / 3: 111 - 5, one colony, c. 45 mm high; 111 - 9, one colony, c. 60 mm high, with gonothecae; ANT XXI / 2: PS 65 / 121, one colony, c. 40 mm high, with gonothecae; PS 65 / 248, one colony, c. 35 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD2E983FEC7FCA29921.taxon	biology_ecology	Ecology and distribution. Previously reported at depths from 15 m (Naumov & Stepanjants 1972, as Sertularella biformis) to 1042 m (Peña Cantero et al. 2017); present material was collected between 62 and 287 m. Circum-Antarctic distribution (Peña Cantero et al. 1997).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD2E983FD5DFBAC9F4C.taxon	description	(Fig. 10 h – j)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD2E983FD5DFBAC9F4C.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 77, one colony, c. 45 mm high; 48 - 274, one colony, c. 75 mm high; 48 - 276, one colony, c. 25 mm high; 48 - 297, one colony, c. 20 mm high; ANT XXI / 2: PS 65 / 121, one colony, c. 80 mm high; PS 65 / 132, one colony, c. 65 mm high; PS 65 / 166, one colony, c. 10 mm high, on St. nonscripta; PS 65 / 253, three stems, c. 60, 70, 75 mm high; PS 65 / 265, one colony, c. 65 mm high, and few stems, up to 20 mm high, on St. polarsterni; PS 65 / 274, one colony, c. 75 mm high; PS 65 / 278, one colony, c. 30 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD2E983FD5DFBAC9F4C.taxon	biology_ecology	Ecology and distribution. Previously reported at depths from 6 (Naumov & Stepanjants 1972, as Sertularella spiralis) to 2143 m (Peña Cantero et al. 2017); our material comes from depths between 119 and 417 m. Species with a circum-Antarctic distribution (Stepanjants 1979, as Sertularella spiralis).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD2E983FB23FC129DC9.taxon	description	(Fig. 11 a, 12 a)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD2E983FB23FC129DC9.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 27, several stems, up to 30 mm high, on dead octocoral; 48 - 77, several stems, up to 40 mm high, on A. frigida and octocoral, with gonothecae; 48 - 197, one colony, up to 10 mm high, on St. polarsterni; 48 - 220, several stems, c. 40 mm high, with gonothecae; ANT XVII / 3: 111 - 18, several stems, up to 40 mm high, on undetermined hydrorhiza and O. terranovae, with gonothecae; ANT XXI / 2: PS 65 / 166, few stems, up to 9 mm high, on O. erratum; PS 65 / 174, one colony, up to 14 mm high, on A. elongatus; PS 65 / 237, one colony, up to 10 mm high, on S. lobata; PS 65 / 265, several stems, up to 35 mm high, on St. polarsterni; PS 65 / 276, few stems, up to 15 mm high; PS 65 / 278, some stems, up to 18 mm high; on B. subrufa and H. secundum; PS 65 / 280, few stems, up to 8 mm high; PS 65 / 281, several stems, up to 35 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD2E983FB23FC129DC9.taxon	biology_ecology	Ecology and distribution. Previously reported at depths between 20 (Naumov & Stepanjants 1972, as Symplectoscyphus curvatus) and 1658 m (Peña Cantero in press); material examined collected from 82 to 416 m. Species with circum-Antarctic distribution (Peña Cantero et al. 2002).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD3E983F8E4FE2A9B86.taxon	description	(Fig. 11 b, 12 b)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD3E983F8E4FE2A9B86.taxon	materials_examined	Material examined. ANT XVII / 3: 111 - 7, several stems, up to 35 mm high, on O. terranovae, with gonothecae; ANT XXI / 2: PS 65 / 281, some stems, up to 60 mm high, on O. terranovae and gravel, with developing gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44EFFD3E983F8E4FE2A9B86.taxon	biology_ecology	Ecology and distribution. Reported at depths from 8 (Naumov & Stepanjants 1972, as Sertularella cumberlandica) to 540 m (Peña Cantero 2012); present material collected at 67 – 82 m. Species widely distributed in Antarctic waters, with circum-Antarctic distribution (Peña Cantero et al. 2002), but previously not documented from the Weddell Sea.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44FFFD0E983F90CFB189BAA.taxon	description	(Fig. 11 c, 12 c)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44FFFD0E983F90CFB189BAA.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 44, several stems, up to 30 mm high, with gonothecae; 48 - 77, few stems, up to 5 mm high, on H. jaederholmi; 48 - 168, few stems, up to 66 mm high, with gonothecae; 48 - 222; several stems, up to 25 mm high, with gonothecae; ANT XXI / 2: PS 65 / 121, few stems, up to 30 mm high, on Sc. nana; PS 65 / 237, few stems, up to 9 mm high; PS 65 / 248, one colony, up to 45 mm high, on octocoral, with developing gonothecae; PS 65 / 281, few stems, up to 15 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44FFFD0E983F90CFB189BAA.taxon	biology_ecology	Ecology and distribution. Previously known from 49 (Peña Cantero 2008) to 2043 m (Peña Cantero 2012); present material found between 82 and 360 m. Circum-Antarctic species (Stepanjants 1979).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44CFFD1E983F956FD3199FA.taxon	description	(Fig. 11 d, 12 d)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44CFFD1E983F956FD3199FA.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 4, few stems, c. 9 mm high; 48 - 44, mass of stems, c. 40 mm high, with gonothecae and few stems, up to 14 mm high, on bryozoan; 48 - 58, mass of stems, c. 40 mm high, with developing gonothecae; 48 - 72, some stems, up to 10 mm high; 48 - 168, some stems, up to 25 mm high, on Sy. liouvillei; 48 - 189, some stems, up to 15 mm high; 48 - 220, mass of stems, c. 40 mm high, with gonothecae, and few stems, up to 30 mm high, on Sc. nana and Sy. anae; ANT XVII / 3: 111 - 6, mass of stems, c. 30 mm high; 111 - 9, some stems, up to 20 mm high, on T. longstaffi, with developing gonothecae; ANT XXI / 2: PS 65 / 39, mass of stems, c. 65 mm high, with gonothecae, and some stems, up to 15 mm high, on Sc. nana, with gonothecae; PS 65 / 121, several stems, up to 35 mm high, on St. dichotoma; PS 65 / 132, several stems, up to 20 mm high, on B. subrufa; PS 65 / 166, mass of stems, c. 40 mm high, with developing gonothecae; PS 65 / 174, several stems, up to 30 mm high, on B. subrufa, with gonothecae; PS 65 / 237, some stems, up to 25 mm high, on Sc. nana and S. lobata, and mass of stems, c. 40 mm high, with gonothecae; PS 65 / 248, few stems, up to 6 mm high; PS 65 / 253, mass of stems, up to 60 mm high, with gonothecae; PS 65 / 265, mass of stems, up to 30 mm high, and some stems, up to 12 mm high, on B. subrufa; PS 65 / 276, mass of stems, up to 40 mm high, with developing gonothecae; PS 65 / 278, few stems, up to 12 mm high; PS 65 / 279, mass of stems, c. 30 mm high, with developing gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44CFFD1E983F956FD3199FA.taxon	discussion	Remarks. Material devoid of reproductive structures is tentatively assigned to Sy. exochus. According to Peña Cantero (2017), the separation between Sy. exochus and Sy. glacialis in the absence of gonothecae is rather difficult because both species may develop very similar hydrothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44CFFD1E983F956FD3199FA.taxon	biology_ecology	Ecology and distribution. Species reported at depths between 15 (Vervoort 1972 b, as Symplectoscyphus glacialis) and 1958 m (Peña Cantero 2012); present material collected from 62 to 352 m. Species with circum- Antarctic distribution (Peña Cantero 2014 a).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44DFFD1E983FD37FC9A98B9.taxon	description	(Fig. 11 e)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44DFFD1E983FD37FC9A98B9.taxon	materials_examined	Material examined. ANT XXI / 2: PS 65 / 166, few stems, up to 15 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44DFFD1E983FD37FC9A98B9.taxon	biology_ecology	Ecology and distribution. Previously documented at depths from 86 [Broch 1948, as Sertularella (Symplectoscyphus) glacialis] to 402 m (Peña Cantero et al. 2002); present material collected between 253 and 338 m. West-Antarctic distribution (Peña Cantero et al. 2002).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44DFFD1E983FBF4FD0A9CC8.taxon	description	(Fig. 11 f, 12 e)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44DFFD1E983FBF4FD0A9CC8.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 27, few stems, up to 15 mm high; 48 - 44, few stems, up to 10 mm high, on polychaete tube; 48 - 50, some stems, up to 50 mm high, on St. frigida; 48 - 63, one colony, c. 30 mm high; 48 - 70, few stems, up to 6 mm high, on St. polarsterni; 48 - 77, several stems, up to 20 mm high, on octocoral and H. jaederholmi; 48 - 82, several stems, up to 30 mm high, on St. polarsterni; 48 - 97, few stems, up to 8 mm high, on St. polarsterni; 48 - 154, several stems, up to 17 mm high, on St. pachyclada and St. polarsterni; 48 - 189, some stems, up to 13 mm high, on St. frigida; 48 - 194, few stems, up to 25 mm high, on Sc. nana; 48 - 197, few stems, up to 3 mm high, on A. frigida; 48 - 220, some stems, up to 20 mm high, on Sc. nana and St. glomulosa; 48 - 222, few stems, up to 9 mm high, on Sc. nana; ANT XXI / 2: PS 65 / 39, some stems, up to 30 mm high, on St. glomulosa, S. lobata and Sy. exochus, with gonothecae; PS 65 / 121, few stems, up to 20 mm high, on S. lobata; PS 65 / 174, some stems, up to 17 mm high, on A. elongatus, O. erratum and Sy. weddelli; PS 65 / 175, few stems, up to 2 mm high, on B. subrufa; PS 65 / 237, several stems, up to 65 mm high; PS 65 / 248, some stems, up to 40 mm high, on dead octocoral and H. incertus; PS 65 / 253, few stems, up to 4 mm high, on St. polarsterni; PS 65 / 265, some stems, up to 35 mm high, on St. polarsterni and St. vanhoeffeni; PS 65 / 274, mass of stems, c. 40 mm high, with gonothecae, and several stems, up to 20 mm high, on St. frigida, St. nonscripta and St. polarsterni; PS 65 / 276, few stems, up to 8 mm high, on S. lobata and Sy. vanhoeffeni; PS 65 / 278, mass of stems, c. 20 mm high, and few stems, up to 5 mm high, on A. elongatus and H. secundum; PS 65 / 279, some stems, up to 13 mm high, on B. subrufa; PS 65 / 280, mass of stems, c. 30 mm high, on C. microrhiza, with developing gonothecae; PS 65 / 292, some stems, c. 15 mm high; PS 65 / 336, some stems, c. 20 mm high, on bryozoan.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44DFFD1E983FBF4FD0A9CC8.taxon	discussion	Remarks. Infertile material is tentatively assigned to Sy. glacialis because of the difficulty in separating it from Sy. exochus in the absence of gonothecae (see Peña Cantero 2017).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44DFFD1E983FBF4FD0A9CC8.taxon	biology_ecology	Ecology and distribution. Previously collected from 5 (Naumov & Stepanjants 1972, as Sertularella glacialis) to 1157 m (Peña Cantero 2014 a); material examined collected between 120 and 659 m. Pan-Antarctic distribution (Soto Àngel & Peña Cantero 2015).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983FF77FF5B9AB1.taxon	description	(Fig. 11 g, 12 f – g)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983FF77FF5B9AB1.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 168, one colony, c. 105 mm high, with gonothecae; 48 - 197, one colony, c. 20 mm high; 48 - 220, one colony, c. 45 mm high, with gonothecae; ANT XXI / 2: PS 65 / 174, one colony, c. 280 mm high, on gravel, with developing gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983FF77FF5B9AB1.taxon	biology_ecology	Ecology and distribution. Previously reported at depths between 65 (Peña Cantero 2008) and 536 m (Peña Cantero in press); present material collected from 228 to 416 m. Antarctic-Patagonian distribution (Peña Cantero 2017).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983FDCDFDCD9F28.taxon	description	(Fig. 11 h, 12 h)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983FDCDFDCD9F28.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 31, some stems, up to 17 mm high, on O. terranovae and Tubularia sp. 2, with gonothecae; 48 - 44, some stems, up to 40 mm high, on S. lobata, with gonothecae; 48 - 168, few stems, up to 5 mm high, on H. pseudodelicatulum; 48 - 194, some stems, up to 40 mm high, on Oswaldella tottoni Peña Cantero & Vervoort, 1996 and Sc. nana, with gonothecae; 48 - 220, some stems, up to 13 mm high, on Sc. nana; 48 - 276, some stems, up to 10 mm high, on Sc. nana; ANT XVII / 3: 111 - 5, some stems, up to 10 mm high, on O. terranovae, with gonothecae; 111 - 9, some stems, up to 13 mm high, on S. lobata; 111 - 19, some stems, up to 15 mm high, on Sc. unifurcata and Tubularia sp. 1; ANT XXI / 2: PS 65 / 39, some stems, up to 20 mm high, on Sc. nana and S. lobata, with gonothecae; PS 65 / 121, one colony, c. 10 mm high, with developing gonothecae; PS 65 / 175, some stems, up to 12 mm high, on Eudendrium sp. 1 and O. erratum; PS 65 / 237, some stems, up to 20 mm high, on Sc. unifurcata; PS 65 / 276, some stems, up to 10 mm high, on S. lobata; PS 65 / 281, some stems, up to 13 mm high, on Sc. nana.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983FDCDFDCD9F28.taxon	biology_ecology	Ecology and distribution. Species known from the tidal level (Blanco 1984, as Symplectoscyphus plectilis) to 1379 m (Peña Cantero & Ramil 2006); present material collected between 62 and 417 m. Circum-Antarctic distribution (Peña Cantero & Ramil 2006).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983FB46FC559EC2.taxon	description	(Fig. 11 i)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983FB46FC559EC2.taxon	materials_examined	Material examined. ANT XXI / 2: PS 65 / 259, few stems, c. 10 mm high; PS 65 / 276, few stems, c. 15 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983FB46FC559EC2.taxon	biology_ecology	Ecology and distribution. Species reported in Antarctic waters in only one occasion at a depth of 603 m in the Bellingshausen Sea, although it is widely distributed in the Southern Hemisphere (Peña Cantero 2012 and literature therein); material examined was collected at depths from 268 to 333 m. This finding constitutes the second report of the species in Antarctic waters and the first evidence for the Weddell Sea.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983F9EAFAFF9C8E.taxon	description	(Fig. 11 j, 12 i)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983F9EAFAFF9C8E.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 4, some stems, up to 12 mm high; 48 - 189, some stems, up to 20 mm high; 48 - 220, several stems, up to 25 mm high, on Sy. exochus, with gonothecae; 48 - 223, some stems, up to 12 mm high, on Sc. nana; ANT XVII / 3: 111 - 6, some stems, up to 6 mm high, on O. terranovae; ANT XXI / 2: PS 65 / 39, mass of stems, c. 30 mm high, with gonothecae, and numerous stems, up to 60 mm high, on C. hicksoni, Sc. nana, S. lobata, Sy. naumovi, with gonothecae; PS 65 / 121, some stems, up to 35 mm high, on Sc. nana, and mass of stems, c. 25 mm high; PS 65 / 245, mass of stems, c. 20 mm high, with developing gonothecae; PS 65 / 248, mass of stems, c. 50 mm high; PS 65 / 253, mass of stems, c. 30 mm high; PS 65 / 274, few stems, up to 10 mm high, on St. glomulosa and bryozoan; PS 65 / 276, mass of stems, c. 30 mm high, with gonothecae; PS 65 / 281, one stem, c. 3 mm high, on gravel.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44AFFD6E983F9EAFAFF9C8E.taxon	biology_ecology	Ecology and distribution. Species collected from 7 (Vervoort 1972 b) to 1958 m (Peña Cantero 2012); present material between 68 and 337 m. Circum-Antarctic distribution (Stepanjants 1979, as Sertularella plectilis).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD7E983FB24FE429EA0.taxon	description	(Fig. 6 l – m)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD7E983FB24FE429EA0.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 197, one colony, c. 45 mm high; 48 - 220, one colony, c. 65 mm high; ANT XXI / 2: PS 65 / 174, one colony, c. 60 mm high, PS 65 / 175, one colony, c. 130 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD7E983FB24FE429EA0.taxon	biology_ecology	Ecology and distribution. Species reported at depths from 63 (Peña Cantero & García Carrascosa 1993) to 1658 m (Peña Cantero in press); present material from 236 to 416 m. Species with Antarctic-Patagonian distribution (Stepanjants 1979).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD7E983FF77FC469AD5.taxon	description	(Fig. 11 k, 12 j)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD7E983FF77FC469AD5.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 5, one colony, c. 18 mm high, on sponge; 48 - 222, one colony, c. 16 mm high, with gonothecae; ANT XXI / 2: PS 65 / 276, one colony, c. 25 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD7E983FF77FC469AD5.taxon	biology_ecology	Ecology and distribution. Previously reported from depths between 6 (Naumov & Stepanjants 1972, as Sertularella vanhoeffeni) and 964 m (Peña Cantero 2014 a); material examined collected at 177 – 277 m. Species with circum-Antarctic distribution (Peña Cantero & García Carrascosa 1995).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD7E983FE11FCD09894.taxon	description	(Fig. 11 l, 12 k)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD7E983FE11FCD09894.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 168, mass of stems, c. 40 mm high, with developing gonothecae; 48 - 222, mass of stems, c. 50 mm high, with gonothecae; 48 - 276, few stems, up to 13 mm high, on Sc. nana; ANT XVII / 3: 111 - 7, some stems, up to 11 mm high, with gonothecae; 111 - 9, some stems, up to 13 mm high, with gonothecae; 111 - 18, some stems, up to 10 mm high, on O. terranovae; 111 - 19, some stems, up to 20 mm high, on Sc. unifurcata, with gonothecae; ANT XXI / 2: PS 65 / 39, some stems, up to 10 mm high; PS 65 / 121 few stems, up to 10 mm high, on O. tottoni and Sc. nana; PS 65 / 174, some stems, up to 35 mm high, with gonothecae; PS 65 / 237, some stems, up to 40 mm high, on sponge and Sc. nana; PS 65 / 276, mass of stems, c. 50 mm high, with developing gonothecae; PS 65 / 278, some stems, up to 15 mm high; PS 65 / 281, some stems, up to 15 mm high, on O. terranovae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD7E983FE11FCD09894.taxon	biology_ecology	Ecology and distribution. Species previously known from depths between 60 (Peña Cantero 2017) to 390 m (Peña Cantero et al. 2002); present material, was collected from 62 to 417 m depth. Circum-Antarctic species (Peña Cantero 2017) with few records, reported here for the third time.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD4E983F951FC809A63.taxon	description	(Fig. 13 a)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD4E983F951FC809A63.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 150, three stems, c. 70, 75 and 110 mm high; 48 - 237, some stems, up to 25 mm high, on Sc. nana; 48 - 276, two stems, 40 and 60 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD4E983F951FC809A63.taxon	discussion	Remarks. The great resemblance between Halecium antarcticum and H. pseudodelicatulum makes both species almost indistinguishable in the absence of gonothecae (see Peña Cantero 2014 b). The material examined here has been tentatively assigned to H. antarcticum based on the disposition of the hydrophore, pointing more outwards than in H. pseudodelicatulum (Fig. 13 a, j).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A44BFFD4E983F951FC809A63.taxon	biology_ecology	Ecology and distribution. Species reported from 45 (Watson 2008) to 1157 m (Peña Cantero 2014 a); present material was collected between 254 and 758 m. Species reported exclusively from East Antarctica (Peña Cantero 2014 b). Thus, if confirmed, present record will constitute the first evidence from the Weddell Sea as well as for West Antarctica, pointing to a circum-Antarctic distribution.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A448FFD5E983F8C8FC899B86.taxon	description	(Fig. 13 b – d)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A448FFD5E983F8C8FC899B86.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 44, one colony, c. 230 mm high, with male gonothecae; 48 - 50, one colony, c. 220 mm high, with male gonothecae; 48 - 70, few stems, up to 5 mm high, on B. subrufa; 48 - 222, one colony, c. 270 mm high, with gonothecae; ANT XXI / 2: PS 65 / 276, one colony, c. 18 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A448FFD5E983F8C8FC899B86.taxon	biology_ecology	Ecology and distribution. Species known from depths between 197 (Peña Cantero 2017) and 950 m (Peña Cantero in press); material examined from 227 to 288 m. Species with circum-Antarctic distribution (Peña Cantero 2014 b), reported here for the Weddell Sea for the first time.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A449FFD5E983FEA3FC5D9921.taxon	description	(Fig. 13 e)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A449FFD5E983FEA3FC5D9921.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 27, few stems, up to 20 mm high, on S. lobata; 48 - 77, few stems, up to 15 mm high, on sponge spicule.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A449FFD5E983FEA3FC5D9921.taxon	biology_ecology	Ecology and distribution. Species reported from 22 (Vervoort 1972 b, as Halecium delicatulum) to 350 m (Hartlaub 1904, as Halecium tenellum); present material at 191 – 360 m. Circum-Antarctic species (Peña Cantero et al. 2013). Present finding constitutes the first evidence for the Weddell Sea.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A449FFD5E983FD5DFA8F98B8.taxon	description	(Fig. 13 f – g, 14 a)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A449FFD5E983FD5DFA8F98B8.taxon	materials_examined	Material examined. ANT XXI / 2: PS 65 / 121, one colony, c. 220 mm high, on gravel, with female gonothecae; PS 65 / 248, one colony, c. 260 mm high, on stone, with female gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A449FFD5E983FD5DFA8F98B8.taxon	biology_ecology	Ecology and distribution. In Antarctic waters, reported at depths from 15 (Stepanjants 1979) to 527 m (Peña Cantero 2014 a); present material at 268 – 287 m. Species with Antarctic – Kerguélen distribution (Peña Cantero & Gili 2006). This new report constitutes the first evidence from both the Weddell Sea and West Antarctica.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A449FFD5E983FBF6FDCB9C36.taxon	description	(Fig. 13 h)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A449FFD5E983FBF6FDCB9C36.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 5, few stems, up to 2 mm high, on sponge; 48 - 27, few stems, up to 2 mm high, on Sy. glacialis; 48 - 31, few stems, up to 5 mm high, on O. terranovae; 48 - 33, few stems, up to 10 mm high, on O. terranovae; 48 - 34, few stems, up to 8 mm high, on O. terranovae; 48 - 36, several stems, up to 25 mm high, on O. terranovae, with male gonothecae; 48 - 77, some stems, up to 15 mm high, on St. polarsterni; 48 - 150, few stems, up to 10 mm high, on E. scotti and St. polarsterni; 48 - 220, numerous stems, up to 60 mm high, on Sc. nana, Sy. anae, Sy. exochus, Sy. naumovi, with gonothecae; 48 - 222, few stems, up to 2 mm high, on Sc. nana; 48 - 276, some stems, up to 10 mm high, on Sc. nana; ANT XVII / 3: 111 - 5, several stems, up to 30 mm high, on O. terranovae and polychaete tube, with gonothecae; 111 - 7, several stems, up to 20 mm high, on O. terranovae; 111 - 9, numerous stems, up to 40 mm high, on polychaete tube, H. arboreum, O. terranovae and T. longstaffi, with gonothecae; 111 - 18, several stems, up to 20 mm high, on O. terranovae and Sc. nana, with gonothecae; 111 - 19, several stems, up to 20 mm high, on Sy. weddelli and Tubularia sp. 1, with gonothecae; ANT XXI / 2: PS 65 / 39, several stems, up to 30 mm high, on C. hicksoni, Sc. nana, Sy. exochus and Sy. plectilis, with gonothecae; PS 65 / 121, few stems, up to 3 mm high, on S. lobata; PS 65 / 248, few stems, up to 2 mm high, on Sy. curvatus and Sy. plectilis; PS 65 / 253, some stems, up to 10 mm high, on St. polarsterni; PS 65 / 265, some stems, up to 15 mm high, on St. polarsterni and H. pseudodelicatulum; PS 65 / 276, one colony, c. 15 mm high; PS 65 / 278, several stems, up to 20 mm high, on O. terranovae, L. dumosa and Sy. weddelli; PS 65 / 281, few stems, up to 3 mm high, on O. terranovae and Sy. cumberlandicus.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A449FFD5E983FBF6FDCB9C36.taxon	biology_ecology	Ecology and distribution. Reported from three (Stepanjants 1979, as Halecium ovatum) to 728 m (Peña Cantero 2014 a); examined material from 62 to 758 m. Circum-Antarctic species (Peña Cantero 2014 b), reported here for the Weddell Sea for the first time.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A446FFDAE983F99AFAD59C1B.taxon	description	(Fig. 13 i)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A446FFDAE983F99AFAD59C1B.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 77, one colony, c. 100 mm high; ANT XVII / 3: 111 - 5, one colony, c. 45 mm high; ANT XXI / 2: PS 65 / 248, one colony, c. 40 mm high, on bryozoan.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A446FFDAE983F99AFAD59C1B.taxon	biology_ecology	Ecology and distribution. Previously reported at depths between 24 (Vervoort 1972 a) and 950 m (Peña Cantero in press); present material from 65 to 360 m. A probable Pan-Antarctic species (Peña Cantero 2014 b).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A447FFDBE983FF77FE3F9969.taxon	description	(Fig. 13 j – k)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A447FFDBE983FF77FE3F9969.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 77, one colony, c. 70 mm high; 48 - 168, one colony, c. 25 mm high, on dead octocoral; 48 - 194, one colony, c. 35 mm high, with gonothecae; 48 - 222, some stems, up to 7 mm high, on Sc. nana; ANT XXI / 2: PS 65 / 237, one colony, c. 20 mm high; PS 65 / 265, one colony, c. 35 mm high, with female gonothecae; PS 65 / 274, one colony, c. 80 mm high, on dead octocoral; PS 65 / 278, one colony, c. 35 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A447FFDBE983FF77FE3F9969.taxon	biology_ecology	Ecology and distribution. Previously collected at depths from 82 (Peña Cantero 2013, as Halecium delicatulum) to 240 m (Peña Cantero & Vervoort 2009, as Halecium delicatulum); present material from 119 to 360 m. Until now, valid records are restricted to West Antarctica (Peña Cantero 2014 b); reported here for the Weddell Sea for the first time.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A447FFDBE983FD85FADE9824.taxon	description	(Fig. 13 l)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A447FFDBE983FD85FADE9824.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 154, one colony, c. 150 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A447FFDBE983FD85FADE9824.taxon	biology_ecology	Ecology and distribution. Reported at depths from 96 (Peña Cantero 2009, as Halecium incertus) to 1019 m (Peña Cantero 2008, as Halecium incertus); material examined at 569 – 583 m. Circum-Antarctic species (Peña Cantero 2014 b) found in rare occasions; present finding constitutes a new addition for the Weddell Sea fauna.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A447FFDBE983FC42FD639CCA.taxon	description	(Fig. 14 b – c)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A447FFDBE983FC42FD639CCA.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 50, one colony, c. 70 mm high, with male gonothecae; 48 - 58, one colony, c. 65 mm high; ANT XXI / 2: PS 65 / 278, mass of stems, c. 140 mm high, with male gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A447FFDBE983FC42FD639CCA.taxon	discussion	Remarks. The species had not been found with gonothecae since its original description (Jäderholm 1904), and only male ones are known. Our material is provided with male gonothecae: 1.3 – 1.5 mm high, 380 µm in maximum diameter; very delicate, easily collapsible; cylindrical, truncated distally; with terminal, circular aperture (Fig. 14 c). Jäderholm (1904) mentioned a shallow distal furrow and a proximal sharp keel in the gonothecae. However, given the delicate consistency of the gonothecae, we regard Jäderholm’s observations as a probable artefact that occurred when mounting the microslides. Peña Cantero (2014 b) revised the holotype of Halecium brevithecum Watson, 2008, discussed the few differences between H. secundum and H. brevithecum, and noted that the latter was described from scarce, infertile material mounted in microslides, and that therefore cannot be completely characterized (Peña Cantero 2014 b: 253). According to him, the hydrothecal adcauline wall of H. brevithecum is completely adnate to the internode in the holotype. In the original description, Watson (2008) also indicated that the adcauline hydrothecal wall is adnate to the internode. However, she also pointed out that the adcauline wall of the hydrophore becomes free just below the hydrotheca. This imply that the hydrothecae might also be free. In this sense, a figure provided by her (Watson 2008: Fig. 4 c) apparently shows a free adcauline hydrothecal wall. It seems, therefore, that this character may vary among hydrothecae, as it has been documented for H. secundum (cf. Peña Cantero 2014 b). Peña Cantero (2014 b) also indicated that H. brevithecum can be distinguished from H. secundum by the distinctly longer first hydrothecate internode of the branches, the presence of reddish stems, and the perpendicular arrangement of the lower-order branches compared to previous ones. All these features have been clearly observed from the reproductive material of H. secundum. Being so, we consider Halecium brevithecum as a junior synonym of Jäderholm’s species.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A447FFDBE983FC42FD639CCA.taxon	biology_ecology	Ecology and distribution. Previously reported at depths between 40 (Peña Cantero et al. 2013) and 502 m (Watson 2008, as H. brevithecum); present material at 119 – 283 m. Circum-Antarctic species (Peña Cantero et al. 2013), with only three validated records and a fourth pending one (see Peña Cantero 2014 b), present finding constitutes the first evidence from the Weddell Sea.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A444FFD8E983FF77FD469849.taxon	description	(Fig. 14 d – g)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A444FFD8E983FF77FD469849.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 276, several polyps, on Sc. nana; ANT XXI / 2: PS 65 / 278, several polyps, on Sy. weddelli and sponge; PS 65 / 280, few polyps, on undetermined anthoathecata.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A444FFD8E983FF77FD469849.taxon	discussion	Remarks. Halecium tubatum was considered as species inquirenda by Peña Cantero (2014 b), who pointed out that the species could correspond to incipient stems of other haleciids such as H. interpolatum. However, the analysis of the cnidome has contributed to a better characterization of the species (see below), proving to be different from other congenerics previously documented in Antarctic waters (cf. Peña Cantero 2014 b). The species is considered here as valid, although mature specimens have not been found yet. We consider the two-three basal rings followed by a wavy internode (Fig. 14 e), the absence of diaphragm (Fig. 14 f), the presence of desmocytes (Fig. 14 f), and the greatly recurved hydrotheca (Fig. 14 f – g), coupled with the size of the nematocysts, as unequivocal diagnostic characters of the species. Cnidome composed of microbasic euryteles? [range 17.0 – 19.5 x 6.0 – 8.0 µm, mean 18.7 ± 0.6 x 7.2 ± 0.6 µm (n = 19)] and microbasic mastigophores [range 8.0 – 8.5 x 1.5 – 2.0 µm, mean 8.2 ± 0.2 x 1.6 ± 0.2 µm (n = 17)].	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A444FFD8E983FF77FD469849.taxon	biology_ecology	Ecology and distribution. Valid records of the species are restricted to the holotype, which was collected off Wilkes Land (East Antarctica) at a depth of 163 m (Watson 2008). Material examined here was found between 119 and 417 m depth. Present finding constitutes the first evidence of the species from both the Weddell Sea and West Antarctica, pointing to a circum-Antarctic distribution.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A444FFD8E983FBF7FDAA9D7D.taxon	description	(Fig. 14 h – j)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A444FFD8E983FBF7FDAA9D7D.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 36, one colony, up to 80 mm high; ANT XVII / 3: 111 - 5, one colony, c. 40 mm high; 111 - 6, several stems, c. 140 mm high, on stone, with gonothecae; 111 - 7, several stems, up to 120 mm high, and few stems, up to 6 mm high, on O. terranovae; 111 - 9, several stems, up to 110 mm high, with gonothecae; 111 - 18, one colony, c. 135 mm high, with gonothecae; 111 - 19, one colony, c. 20 mm high; ANT XXI / 2: PS 65 / 39, a few stems, up to 33 mm high; PS 65 / 278, one colony, c. 50 mm high; PS 65 / 279, few stems, up to 35 mm high, on sponge; PS 65 / 280, one colony, c. 20 mm high; PS 65 / 281, some stems c. 80 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A444FFD8E983FBF7FDAA9D7D.taxon	biology_ecology	Ecology and distribution. Species collected between 18 (Hickson & Gravely 1907, as Halecium arboreum) and 1370 m depth (Peña Cantero & Ramil 2006); present material at 62 – 175 m. Pan-Antarctic species widely distributed in Antarctic and sub-Antarctic waters (Peña Cantero & Ramil 2006). Documented in the Weddell Sea by means of remote operate vehicle (Dimmler et al. 2001), present contribution constitutes the first verifiable record from this Antarctic region.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A444FFD9E983F90BFE2F9AF9.taxon	description	(Fig. 10 k)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A444FFD9E983F90BFE2F9AF9.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 5, one stem, c. 12 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A444FFD9E983F90BFE2F9AF9.taxon	discussion	Remarks. The material examined does not agree with any other representatives of the genus previously reported from Antarctic and sub-Antarctic waters (Galea et al. 2017). It shares with the material described as Sertularella sp. by Peña Cantero (2008) the size of the hydrotheca, but differs in the shape and length of free part of the adcauline wall. By the shape and great size of the hydrotheca, the material examined closely resembles to Sertularella gayi (Lamouroux, 1821), previously known from South Africa (Ritchie 1909) and the Patagonian region (Blanco 1982 and literature cited), and Sertularella blanconae El Beshbeeshy, 2011, known from the Patagonian region (El Beshbeeshy 2011). However, the scarcity of the available material and the lack of gonosome prevent us for providing a proper identification.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A444FFD9E983F90BFE2F9AF9.taxon	biology_ecology	Ecology and distribution. Material examined comes from a depth of 177 m. Species previously unknown from Antarctic waters.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A445FFD9E983FD86FE7D98DE.taxon	description	(Fig. 15 a)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A445FFD9E983FD86FE7D98DE.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 33, one cormoid, c. 42 mm high, with corbulae; 48 - 34, three cormoids, up to 45 mm high, with corbulae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A445FFD9E983FD86FE7D98DE.taxon	discussion	Remarks. Recently described species, whose finding constituted the first evidence of the genus for any polar region and the first report of the family from Antarctic waters (see Soto Àngel & Peña Cantero 2017 b).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A445FFD9E983FD86FE7D98DE.taxon	biology_ecology	Ecology and distribution. Reported at depths from 62 to 116 m. Only known for now from the Cape Norvegia region, in the Weddell Sea.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A445FFD9E983FB6EFEEC9EC6.taxon	description	(Fig. 15 b – c)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A445FFD9E983FB6EFEEC9EC6.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 353, one colony, c. 90 mm high, with gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A445FFD9E983FB6EFEEC9EC6.taxon	biology_ecology	Ecology and distribution. Rare species, only reported twice: from its type locality in the Ross Sea at a depth of 180 m (Hickson & Gravely 1907, as Plumularia glacialis), and from the eastern part of the Weddell Sea, at a depth of 620 – 640 m (Peña Cantero et al. 1996); present material collected at 129 – 132 m. Probably a circum- Antarctic species. Present finding constitutes the third record of the species and the first evidence from the South Shetland Islands.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A445FFDEE983F9E3FEC59BAB.taxon	description	(Fig. 15 d – f)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A445FFDEE983F9E3FEC59BAB.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 50, several stems, up to 270 mm high, on gravel, with developing gonothecae; 48 - 194, several stems, up to 160 mm high, on gravel, with developing gonothecae; 48 - 220, several stems, up to 210 mm high, on gravel, with developing gonothecae; 48 - 222, few stems, up to 100 mm high, with developing gonothecae; 48 - 223, several stems, up to 130 mm high, with gonothecae; 48 - 276, several stems, up to 320 mm high, with gonothecae; ANT XVII / 3: 111 - 9, few stems, up to 125 mm high, with gonothecae; 111 - 18, few stems, up to 90 mm high, with gonothecae; ANT XXI / 2: PS 65 / 39, several stems, up to 200 mm high, with gonothecae; PS 65 / 121, several stems, up to 280 mm high, with gonothecae; PS 65 / 237, few stems, up to 140 mm high, on gravel, with gonothecae; PS 65 / 280, few stems, up to 80 mm high, with gonothecae; PS 65 / 281, few stems, up to 85 mm high; PS 65 / 336, few stems, up to 90 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A445FFDEE983F9E3FEC59BAB.taxon	biology_ecology	Ecology and distribution. Species collected at depths between 43 (Stepanjants 1972, as Schizotricha turqueti) and 1890 m (Peña Cantero & Vervoort 2005); present material from 62 to 417 m. Circum-Antarctic species (Peña Cantero et al. 1996).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A442FFDFE983F92AFB1599B2.taxon	description	(Fig. 15 g – j)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A442FFDFE983F92AFB1599B2.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 5, one stem, c. 30 mm high; 48 - 33, few stems, up to 80 mm high, with developing gonothecae; 48 - 63, one stem, c. 75 mm high; 48 - 197, few stems, up to 50 mm high; 48 - 220, few stems, up to 60 mm high, with developing gonothecae; 48 - 276, several stems, up to 80 mm high, with gonothecae; ANT XVII / 3: 111 - 9, one stem, c. 30 mm high; 111 - 19, several stems, up to 330 mm high, some on sponge, with gonothecae; ANT XXI / 2: PS 65 / 121, several stems, up to 100 mm high, with gonothecae; PS 65 / 132, few stems, up to 95 mm high; PS 65 / 274, few stems, up to 80 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A442FFDFE983F92AFB1599B2.taxon	discussion	Remarks. Some specimens differ from the re-description of the species provided by Peña Cantero et al. (1996) and the diagnoses of the species by Peña Cantero & Vervoort (2005). The materials from the stations ANT XV / 3 48 - 5, 48 - 63, 48 - 220, ANT XXI / 2 PS 65 / 121, PS 65 / 132 are unbranched, unlike our current knowledge of the species (see Peña Cantero & Vervoort 2005). However, according to the drawings provided by Allman (1883), the branching takes place in the very basal region of the colony. The fragmented condition of the material examined here could be masking this character. In the specimens mentioned above, there is a single nematotheca in the basal ahydrothecate internodes following hydrocladial apophyses (Fig. 15 h) (but two in the basal ahydrothecate internodes following caulinar apophyses), unlike previous descriptions of the species, which reported two nematothecae in basal ahydrothecate internodes. No differences in number of nematothecae among basal ahydrothecate internodes according to location were mentioned by previous authors. Additionally, some hydrocladial internodes are provided with two consecutive hydrothecae (Fig. 15 j), while a single one has been mentioned by previous contributions (e. g. Peña Cantero et al. 1996). This character variation has also been reported for Schizotricha turqueti Billard, 1906 (see Peña Cantero & Vervoort 2005). We have considered these observations as minor variations, and we assign all the material examined to Sc. unifurcata with confidence.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A442FFDFE983F92AFB1599B2.taxon	biology_ecology	Ecology and distribution. Previously reported at depths from 15 (Millard 1977) to 567 m (Stechow 1925); present material between 62 to 417 m. Antarctic-Kerguélen distribution (Peña Cantero 1998).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A443FFDFE983FC42FA269F06.taxon	description	(Fig. 16 k – l)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A443FFDFE983FC42FA269F06.taxon	materials_examined	Material examined. ANT XXI / 2: PS 65 / 278, one stem, c. 10 mm high, on H. arboreum.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A443FFDFE983FC42FA269F06.taxon	biology_ecology	Ecology and distribution. Previously found at depths between 126 (Peña Cantero 2008) and 440 m (Peña Cantero et al. 1997 a); present material at 119 – 120 m. West Antarctic distribution (Peña Cantero & Vervoort 2004).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A443FFDFE983FB23FE7E9D81.taxon	description	(Fig. 16 a – e)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A443FFDFE983FB23FE7E9D81.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 4, few stems, up to 80 mm high, on gravel, with developing gonothecae; 48 - 50, few stems, up to 100 mm high, with developing gonothecae; 48 - 58, few stems, up to 90 mm high, with developing gonothecae; 48 - 168, few stems, up to 60 mm high, with developing gonothecae; 48 - 197, few stems, up to 45 mm high; 48 - 222, few stems, up to 55 mm high, with developing gonothecae; 48 - 276, few stems, up to 95 mm high, with developing gonothecae; ANT XXI / 2: PS 65 / 39, few stems, up to 70 mm high, with gonothecae; PS 65 / 121, several stems, up to 100 mm high, with developing gonothecae; PS 65 / 132, several stems, up to 205 mm high, some on polychaete tube; PS 65 / 148, few stems, up to 75 mm high, on gravel; PS 65 / 166, several stems, up to 160 mm high; PS 65 / 174, several stems, up to 170 mm high; PS 65 / 175, several stems, up to 120 mm high; PS 65 / 237, several stems, up to 120 mm high, with gonothecae; PS 65 / 274, several stems, up to 150 mm high; PS 65 / 280, several stems, up to 140 mm high; PS 65 / 336, one stem, c. 20 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A443FFDFE983FB23FE7E9D81.taxon	biology_ecology	Ecology and distribution. Species previously found at depths between 55 (Peña Cantero & Vervoort 2004) and 696 m (Peña Cantero et al. 1997 a); present material between 166 and 417 m. West Antarctic distribution (Peña Cantero & Vervoort 2004).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A443FFDCE983F8A7FDE29A3E.taxon	description	(Fig. 16 f – j)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A443FFDCE983F8A7FDE29A3E.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 27, few stems, up to 55 mm high; 48 - 72, few stems, up to 50 mm high; 48 - 168, few stems, up to 60 mm high; 48 - 189, few stems, up to 55 mm high; 48 - 276, few stems, up to 20 mm high; ANT XXI / 2: PS 65 / 148, few stems, up to 75 mm high; PS 65 / 237, few stems, up to 30 mm high; PS 65 / 278, few stems, up to 70 mm high.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A443FFDCE983F8A7FDE29A3E.taxon	biology_ecology	Ecology and distribution. Species collected at depths between 80 (Peña Cantero et al. 1997 a) and 1157 m (Peña Cantero 2014 a); present material was collected at depths between 119 and 417 m. Circum-Antarctic distribution (Peña Cantero et al. 1997 a).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A440FFC2E983F8ABFBC19846.taxon	description	(Fig. 17 a – f)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A440FFC2E983F8ABFBC19846.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 27, several stems, up to 110 mm high; 48 - 31, few colonies, up to 80 mm high, some on stone; 48 - 33, several colonies, up to 170 mm high, some on stone; 48 - 34, one colony, up to 150 mm high, on sponge, with developing gonothecae; 48 - 36, few colonies, up to 120 mm high, with gonothecae; 48 - 50, several stems, up to 100 mm high; 48 - 63, several stems, up to 170 mm high; 48 - 210, several stems, up to 70 mm high, on stone and gravel, with developing gonothecae; 48 - 276, several stems, up to 110 mm high; ANT XVII / 3: 111 - 5, several stems, up to 130 mm high, on gravel, with gonothecae; 111 - 6, several stems, up to 100 mm high; 111 - 7, several stems, up to 120 mm high, with developing gonothecae; 111 - 9, few stems, up to 60 mm high, with gonothecae; 111 - 18, few colonies, up to 210 mm high, with gonothecae; ANT XXI / 2: PS 65 / 251, few colonies, up to 115 mm high, on gravel and stone; PS 65 / 278, few stems, up to 130 mm high; PS 65 / 281, few colonies, up to 110 mm high, with gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A440FFC2E983F8ABFBC19846.taxon	discussion	Remarks. [Note: Recently, Peña Cantero and González Molinero (2018) demonstrated that the ubiquitous Oswaldella stepanjantsae Peña Cantero, Svoboda & Vervoort, 1997 is a junior synonym of the uncommon Oswaldella terranovae Peña Cantero & Vervoort, 1996]. Among the abundant material examined, we found some small fragments with caulinar apophyses in spiral arrangement forming three longitudinal rows (Fig. 17 e). In one case, a transition between triseriate and biseriate arrangement has been observed. Hitherto, triseriate apophyses are extremely rare amongst members of the family Kirchenpaueriidae (cf. Peña Cantero 2007), only documented in a single Antarctic representative of the genus Oswaldella: Oswaldella laertesi Peña Cantero, 2007, in which the triseriate disposition is constant. The fragments studied are clearly referable to O. terranovae because up to six axillary nematophores have been observed on the caulinar apophyses, and the abcauline wall of the hydrotheca is clearly longer than its aperture (cf. Peña Cantero & Vervoort 2004, as Oswaldella stepanjantsae). Oswaldella laertesi has low hydrothecae, and up to four axillary nematophores (González Molinero and Peña Cantero 2015). Present study evidence that at least two species of Kirchenpaueriidae belonging to the genus Oswaldella present apophyses in a triseriate arrangement, although in O. terranovae the biseriate disposition is the rule. Present finding could point to a putative phylogenetic relationship between the two species.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A440FFC2E983F8ABFBC19846.taxon	biology_ecology	Ecology and distribution. Species collected at depths between 36 and 1890 m (Peña Cantero & Vervoort 2004, as Oswaldella stepanjantsae); present material between 62 and 417 m. As pointed out by Peña Cantero (2013, 2014 a, as O. stepanjantsae), and evidenced here, this species serve as basibiont for a great diversity of epibiotic hydrozoans, as well as other several taxa (cf. Tab. 3), thus constituting an important habitat former. Species with a circum-Antarctic distribution (Peña Cantero & González Molinero 2018).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A45EFFC2E983FC63FEF29E2D.taxon	description	(Fig. 17 g – m)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A45EFFC2E983FC63FEF29E2D.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 194, few stems, up to 120 mm high, with gonothecae; ANT XXI / 2: PS 65 / 121, several stems, up to 150 mm high, with gonothecae; PS 65 / 276, few stems, up to 120 mm high, with gonothecae.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A45EFFC2E983FC63FEF29E2D.taxon	discussion	Remarks. Only known with female gonothecae from its type locality in the Ross Sea (Peña Cantero & Vervoort 1996), although no sex was attributed by the authors. Material examined here let us confirm a patent sexual dimorphism (Fig. 17 m). Male gonotheca, 1.3 – 1.7 mm high x 0.7 – 0.8 mm maximum width, cylindrical with rounded end, fusiform in lateral view, with distal, circular aperture. Female gonotheca larger, 2.4 – 3.0 mm high x 1.2 mm maximum width, inverted cone-shaped, flattened in lateral view, with subterminal, oval aperture.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A45EFFC2E983FC63FEF29E2D.taxon	biology_ecology	Ecology and distribution. Species reported from depths between 256 (Peña Cantero & Vervoort 1996) and 400 m (Peña Cantero et al. 1997 a); present material from 244 to 277 m. Circum-Antarctic species (Peña Cantero & Vervoort 2004).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A45EFFC3E983F9DAFA849F02.taxon	description	(Fig. 7 k – m)	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A45EFFC3E983F9DAFA849F02.taxon	materials_examined	Material examined. ANT XV / 3: 48 - 4, one colony, c. 50 mm high; 48 - 5, some stems, up to 50 mm high, on Sc. unifurcata, S. lobata and sponge, with gonothecae; 48 - 27, one colony, c. 40 mm high, and some stems, up to 5 mm high, on E. generale; 48 - 44, some stems, up to 60 mm high, on S. lobata and polychaete tube, with gonothecae; 48 - 63, one colony, c. 10 mm high; 48 - 70, one colony, c. 90 mm high, with gonothecae; 48 - 72, several stems, up to 30 mm high, on sponge, with gonothecae; 48 - 77, one colony, c. 45 mm high; 48 - 82, one colony, c. 110 mm high, with developing gonothecae and few stems, up to 20 mm high, on St. polarsterni; 48 - 154, one colony, c. 60 mm high; 48 - 168, one colony, c. 130 mm high, with gonothecae; 48 - 194, one colony, c. 50 mm high; 48 - 197, several stems, up to 90 mm high, on dead octocoral, with gonothecae, and some stems, up to 11 mm high, on Eudendrium sp. 1; 48 - 222, one colony, c. 150 mm high; 48 - 276, one colony, c. 190 mm high, with gonothecae, on Sc. nana; 48 - 297, several stems, up to 45 mm high, on ascidian, with gonothecae; ANT XVII / 3: 111 - 5, some stems, up to 13 mm high, on O. terranovae; 111 - 6, one colony, c. 55 mm high, with gonothecae; 111 - 9, few stems, up to 35 mm high, on O. terranovae and S. lobata; 111 - 18, one colony, c. 65 mm high, with gonothecae, and numerous stems, up to 30 mm high, on O. terranovae, Sc. nana and polychaete tube, with gonothecae; ANT XXI / 2: PS 65 / 39, one colony, c. 20 mm high; PS 65 / 121, one colony, c. 30 mm high, and few stems, up to 10 mm high, on Sc. nana; PS 65 / 132, one colony, c. 82 mm high, on bryozoan, with gonothecae; PS 65 / 148, few stems, up to 8 mm high, on O. erratum; PS 65 / 166, one colony, c. 110 mm high, with gonothecae; PS 65 / 174, one colony, c. 90 mm high, on O. erratum, with gonothecae, and few stems, up to 90 mm high, with developing gonothecae; PS 65 / 175, numerous stems, up to 110 mm high, on O. erratum, octocoral, bryozoan and polychaete tube, with gonothecae; PS 65 / 237, several stems, up to 60 mm high, on Sc. nana, S. lobata and sponge, with gonothecae; PS 65 / 245, one colony, c. 50 mm high; PS 65 / 253, one colony, c. 40 mm high; PS 65 / 259, one colony, c. 75 mm high; PS 65 / 265, one colony, c. 120 mm high, with gonothecae, and few stems, up to 15 mm high, on St. polarsterni; PS 65 / 274, few stems, up to 12 mm high, on Sc. unifurcata and St. polarsterni; PS 65 / 276, few stems, up to 6 mm high, on S. lobata; PS 65 / 278, one colony, c. 60 mm high, and few stems, up to 10 mm high, on sponge; PS 65 / 279, one colony, c. 60 mm; PS 65 / 280, one colony, c. 20 mm high; PS 65 / 281, one colony, c. 140 mm high, on gravel and sponge, with gonothecae, and some stems, up to 25 mm high, on O. terranovae; PS 65 / 336, few stems, up to 10 mm high, on Sc. nana.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A45EFFC3E983F9DAFA849F02.taxon	discussion	Remarks. Similarly to the process described for S. lobata, several specimens have been observed using a wide range of basibionts as substrate (octocorals, hydroids or polychaete tubes, among others). Large colonies are seen in many cases growing on its basibiont until overgrowing entirely the host colony, which is completely indiscernible unless a cross section is done. We suggest that B. subrufa might behave as an aggressive epibiont species that uses a basibiont to reach large sizes, as it is known from the zoantharian Savalia savaglia (Bertoloni, 1819) (Zibrowius 1985). As mentioned above, the relationship can be categorized as parasitism sensu lato, in which the epibiont is detrimental to the host but is not metabolically dependent upon it (see Gili et al. 2006 and references therein). That assumption implies that B. subrufa should have a quicker growth rate than its host. The presence of horizontal growing by polysiphonic stems could enhance its colonizing efficiency. Further in vivo experiments are needed to test this hypothesis.	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
03B887B7A45EFFC3E983F9DAFA849F02.taxon	biology_ecology	Ecology and distribution. Species collected at depths between 25 (Stepanjants 1972) and 1030 m (Peña Cantero et al. 2004); present material from 62 – 583 m depth. Antarctic-Patagonian species (Peña Cantero et al. 2004).	en	Soto, Joan J., Peña, Álvaro L. (2019): Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica). Zootaxa 4570 (1): 1-78, DOI: 10.11646/zootaxa.4570.1.1
