Hebella ritchiei Vervoort, 1959

Gil, Marta & Ramil, Fran, 2025, Hydroids (Cnidaria, Hydrozoa) from Guinea Bissau, Zootaxa 5577 (1), pp. 1-89 : 24-26

Hebella ritchiei Vervoort, 1959

( Fig. 4A ; Table 1)

Hebella ritchiei Vervoort, 1959: 244–245 , fig. 17.— Vervoort, 1966: 123–124, fig. 26.

Lafoëa tenellula : Ritchie, 1911: 820–821, pl. LXXXVIII fig. 5.

Material examined. BISSAU-0810, stn BS191, 10º18'25"– 10º19'20"N, 16º08'47"– 16º08'47"W, 24–25 m, 3-XI-2008: 420 colonies (35 with gonothecae), of which 417 growing on unidentified hydroids, one on a worm tube, one on a bryozoan and one on a crustacean.

BISSAU-0810, stn BS194, 10º21'59"– 10º22'36"N, 16º13'23"– 16º14'03"W, 21–24 m, 3-XI-2008: 16 colonies (15 of them with gonothecae), all growing on unidentified hydroids.

BISSAU-0810, stn BS195, 10º22'44"– 10º23'22"N, 16º15'37"– 16º16'18"W, 29 m, 3-XI-2008: six colonies with gonothecae, all growing on unidentified hydroids.

Description. Colonies stolonal. Hydrothecae borne on short and slightly undulated pedicels, arising from a thin stolon, usually growing along the stems and hydrocladia of a syntheciid colony, and close to the hydrothecae of the host; long, almost cylindrical, tapering and rounded below, and there separated from the pedicel by a thin, transversely-set membrane; aperture distal, transverse, circular in apical view, with slightly everted margin, and usually with 2–3 renovations.

Gonothecae much bigger than the hydrothecae, exceedingly long, with almost parallel walls, gradually narrowing towards base, attached to stolon by a short, curved stalk. Aperture circular, closed by a membrane with a hemispherical depression ( Fig. 4A ).

Remarks. Our material is consistent with that described by Vervoort (1959) from the Republic of Guinea, and allows the description of the gonothecae of this species for the first time.

Hebella ritchiei is a species considered as doubtful by Boero et al. (1997) and a taxon inquirendum in WoRMS. This is evidently due to the morphology of its trophosome that is similar to that of other Hebella species, such as H. scandens ( Bale, 1888) or H. plana Ritchie, 1907 . However, the morphology of its gonotheca is completely different from that of the other species, allowing us to support the specific validity of this hydroid.

Currently, the status of the family Hebellidae is doubtful ( Calder & Faucci 2021). During the last decades, several life cycle and genetic studies have been carried out by different authors ( Migotto & Andrade 2000; Marques et al. 2006; Peña Cantero et al. 2010; Moura et al. 2012; Maronna et al. 2016), establishing that this family is polyphyletic and in need of a thorough revision.

Biology. Hebella ritchiei was found growing on Hincksella cylindrica ( Bale, 1888) ( Vervoort 1959) . Gonothecae were unknown.

In our material, almost all colonies were growing on unidentified hydroids; in addition, three colonies were collected from a worm tube, a bryozoan and a crustacean, respectively. Colonies with gonothecae, previously unknown in this species, were found in November.

Distribution. This species was recorded from Australia by Ritchie (1911, as Lafoea tenellula ) and the Republic of Guinea by Vervoort (1959). Its bathymetric distribution ranges from 30 ( Vervoort 1959) to 108 m ( Ritchie 1911).

Our colonies were collected at depths between 21–25 m.

Figures

FIGURE 4. A. Hebella ritchiei Vervoort, 1959 (stn BS195), colony with gonotheca growing on an unidentified hydroid. B–D. Hebella scandens (Bale, 1888) (stn BS191): hydrothecae (B–C); gonotheca (D). E–G. Hebella sp. (stn BS191); hydrothecae (E–F); nematocysts (G). Scales: a, 0.2 mm; b–f, 0.5 mm; g, 20 µm.