Haliclona (Rhizoniera) pahua, Vicente & Rutkowski & Lavrov & Martineau & Timmers & Toonen, 2025

Vicente, Jan, Rutkowski, Emily, Lavrov, Dennis V., Martineau, Gabrielle, Timmers, Molly & Toonen, Robert J., 2025, Integrative taxonomy of introduced Haplosclerida and four new species from Hawaiʻi, Zootaxa 5566 (2), pp. 243-272 : 255-257

Haliclona (Rhizoniera) pahua sp. nov.

LSIDurn:lsid:zoobank.org:act: 9FFF3BF0-9722-44AA-9B71-2656F5198E68

( Fig. 6 , Table 3)

Haplosclerida sp. JV8; Vicente et al. 2022a, 2022b

Holotype. BPBM C1518 -ARMS in mesocosms at the Hawai‘i Institute of Marine Biology (HIMB), Moku o Loʻe ( Coconut Island ), Kāne‘ohe Bay , Oʻahu (21.4334 °N, - 157.7868 °W); 0.3 m, coll. Jan Vicente, 2017-08- 01 . Paratypes. BPBM C1517 , BPBM C1531 , ARMS in mesocosms at the Hawai‘i Institute of Marine Biology (HIMB), Moku o Loʻe ( Coconut Island ), Kāne‘ohe Bay , Oʻahu (21.4334 °N, - 157.7868 °W); 3 m, coll. Jan Vicente, 2017-09-27 and 2018-03-16 respectively .

Diagnosis. A soft, compressible solitary mound shaped Haliclona (Rhizoniera) with apical oscula, light brown in color, that has a skeleton exclusively composed of oxeas (75–151 x 3–5 µm) arranged in unispicular, anisotropic, ascending ladder-like reticulation and the absence of an ectosome.

Description ( Fig. 6a–c ). Thickly encrusting solitary, circular, mounds less than 1 cm in height and diameter. Surface is smooth but slightly hispid and somewhat punctate. Oscula are circular, 0.5–1 mm wide, and are flush with the surface. There is one osculum per sponge individual. Color of live specimens varies from light to darker shades of brown. Same color pattern is observed in the interior and exterior of the sponge. Consistency is compressible with delicate elasticity. Embryos measuring 150–165 µm in diameter were spotted deep in the choanosome of BPBM C1518 ( Fig 6d ).

Skeleton ( Fig. 6d–f ): Ectosome is not specialized. Choanosome is unispicular, mainly anisotropic where primary lines are connected irregularly by secondary lines (120–130 µm in length). There is some disorganization in areas of the choanosome where the skeleton is subisotropic with isodictyal reticulation. Continuous connection of primary and secondary lines results in an ascending ladder like pattern, of triangular (80–100 µm) or polygonal (140–160 µm) meshes (µm) visible from deep in the choanosome. Secondary lines are absent at the sponge surface resulting in a hispid projection of a single, or a bundle of up to three oxeas. Choanosomal spaces (220–370 µm in diameter) are present but rare. Scarce amounts of spongin is present throughout the choanosome and at the nodes. Small auxiliary oxeas are abundant.

Spicules ( Fig. 6g ; Table 3): Oxeas straight and curved at the center with hastate tips 75–129–151 x 3–4.1–5 µm.

Habitat and ecology. Specimens were collected from ARMS inside mesocosms supplied with unfiltered flow through seawater at the Hawai‘i Institute of Marine Biology (HIMB) in Moku o Loʻe (Coconut Island). During the same period specimens were absent from ARMS on a reef surrounded by a climax sponge community throughout a 2-year monitoring period (Sup. Fig. S 3 in Vicente et al., 2022a). Presence of embryos supports viviparous reproduction in this species.

Taxonomic remarks. The unispicular, anisotropic, choanosomal skeleton of the new species conforms to some of the characters defined for H. ( Reniera ), H. ( Haliclona ) and H. (Rhizoniera). Nevertheless, the connection of primary and secondary lines in the new species is irregular, discarding H. ( Haliclona ) as an ideal match, since species in this subgenus have a very regular, ladder like reticulation. Species belonging to H. ( Reniera ) have a more isotropic organization of oxeas rather than anisotropic and reticulation is also very regular. Therefore, all characters of the new species are preferably supported by the definition of H. (Rhizoniera) which includes species with an anisotropic, ladder-like choanosomal organization of oxeas, with primary lines connected irregularly by secondary lines and the usual absence of the ectosome.

There are currently no H. (Rhizoniera) spp. reported for the Northern or Central Pacific but the thick encrusting, morphology of the new species with oxeas measuring 75–151 x 3–5 µm match other congenerics. These include H. (Rhizoniera) australis ( Lendenfeld 1888) from Eastern Australia, H. (Rhizoniera) curacaoensis ( van Soest 1980) from the Caribbean, H. (Rhiz.) enamela de Laubenfels, 1930 from the Eastern Pacific, H. (Rhizoniera) fugidia Muricy et al., 2015 from Brazil, H. (Rhizoniera) manglarensi and H. (Rhizoniera) zanabriai ( Bispo et al., 2022) from Peru, and H. (Rhizoniera) viscosa ( Topsent 1888) from the Northeast Atlantic ( Table S2 ). Conversely, none of these species grow in the shape of a solitary mound with a single apical oscula, making this a diagnostic character for the new species.

Within unknown subgenera of Haliclona there are ~ 30 species worldwide which share oxea lengths between 75–151 μm or an average length of oxeas between 125–130 µm. Most of these species can be discarded as possible matches, based on their massive, branching, growth forms or mismatching color and the presence of multispiculated fibers. Among species sharing similar spicule lengths, growth morphology and color of unknown subgenera of Haliclona spp. are H. isodictyalis Bergquist, 1961 and H. sasajimensis Hoshino, 1981 . The new species still differs from these in the presence of the anisotropic ladder like arrangement of the choanosome which is absent in both species.

Distribution ( Fig. 2 ). Moku o Loʻe (Coconut Island), Kāne‘ohe Bay on the island of Oʻahu, Hawaiʻi.

Etymology. The given name is based on Lo‘e and Kahoe’s brother Pahu a selfish fisherman who was reluctant to share his catch even though his brother provided him with crops. We use the feminine pahua following the feminine gender of Haliclona and Article 31.2 of the International Code for Zoological Nomenclature (http://www. iczn.org/, accessed on October 16, 2023).

Figures

FIGURE 2. In situ growth variations of Haliclona (Gellius) loe sp. nov. a. holotype BPBM C1523 in situ; b. Embryos in the mesohyl of holotype BPBM C1523 indicated by white arrows. c. Six-month recruit of paratype BPBM 1533. d. paratype BPBP C1534. e. One year recruit of paratype BPBM C1549. f. paratype BPBM C1673. g. paratype BPBM C1672. Scale bars: a, 1 cm; b, 0.5 cm; c-g, 1 cm.

FIGURE 3. Skeletal architecture of Haliclona (Gellius) loe sp. nov. Perpendicular section through the ectosome and choanosome in a, holotype BPBM C1523; b, paratype BPBM C1549; c, paratype BPBM C1673; close up of the choanosome in d–e paratype BPBP C1534. Light microscopy images in f, oxeas of paratype BPBM 1533 SEM images in g, oxeas and h, sigmas of holotype BPBM C1523. Scale bars: a–b, 500 µm; c, 250 µm; d–e, 100 µm; f–g, 50 μm; h, 5 μm.

FIGURE 6. Haliclona (Rhizoniera) pahua sp. nov. a, holotype BPBM C1518 (in situ); b, paratype BPBM C1531 (in situ); c, paratype BPBM C1517 (in situ). d-e, perpendicular section through the ectosome and choanosome in holotype BPBM C1518 and in f, paratype BPBM C1531. SEM images of oxeas in g, holotype BPBM C1518. Multiple eggs or embryos in the choanosome are indicated by white arrow in (d). Scale bars: a-c, 0.5 cm; d, 1 mm; e-f, 500 µm; g, 50 µm.