Cladorhiza mexicana Austin 2017, sp. nov.

Cladorhiza mexicana sp. nov.

Figs. 4–5, Table 1

Type material. Holotype: CASIZ Cat. No. 219700, MBARI D741-A1, Alarcon Rise, Gulf of California, Mexico, 23° 32' 40.7682" N, 108° 25' 52.7304" W, 2473 m, ROV Doc Ricketts dive 741 from R/ V Western Flyer. Date of collection April 5, 2015. Fixed in 95% ethanol.

Type locality. Alarcon Rise, Gulf of California, Mexico.

Etymology. The species name, mexicana, alludes to the country where the holotype was discovered.

Diagnosis. Crinorhiza form, parasol-shaped sponge, on long stalk and presumed basal holdfast. Three size classes of megasclere styles and three microsclere categories including tridentate unguiferate anisochelae, contort sigmancistras, and asymmetrical pseudoamphiasters.

Description. Holotype: Long, parasol-shaped sponge measuring 30 cm in total length with a stalk width of 1 mm. Parasol diameter of 2.6 cm with seventy-six long filaments, 3.3–4.2 cm in length, radiating out in all directions from the parasol edge. Spheroid top-knot on apical surface of parasol measures 9 mm in length and 7.3 mm in diameter with dense, small filaments radiating in all directions in lengths from 4–9 mm. On the stalk 6.9 cm below the parasol is an oocyte swelling, containing numerous visible oocytes, 2.5 cm in length and 3 mm at its widest dimension. Basal holdfast (presumed) broke off during collection. Creamy yellow in preserved state, bright white living specimen.

Spicules. Large style 1 length 3845 ± 268 µm, n=46, width 66.5 ± 7.3 µm, n=46; large style 2 length 2948 ± 298 µm, n=39, width 54.2 ± 8.9 µm, n=40; large style 3 length 1612.3 ± 319 µm, n=46, width 31.4 ± 7.4 µm, n=44; tridentate unguiferate anisochelae 34.5 ± 1.5 µm, n=67; pseudoamphiaster with 5 alae each side, alae slightly longer on one end 108.8 ± 6.4 µm, n=53; sigmancistra 51.2 ± 3.8 µm, n=58 and occur only in the apical surfaces and small filaments of the parasol.

Habitat and associated fauna. The holotype was collected from a pillow basalt with a thin sediment veneer in a heterogeneous habitat of pillow basalt interspersed with sedimentary deposits. The covering of sediment was thick enough to conceal the mode of basal attachment of the holotype, however, upon retrieval, the base of the specimen broke and we interpret this as evidence of basal holdfast attachment, as has been observed for other hard rock attached species. In addition, when rooted in the sediment with rhizoids, these sponges generally release quite easily and are retrieved intact by ROV manipulator or trawl. Other taxa observed in low abundance in the vicinity of the holotype include Actiniaria, Aldrovandia sp., Bonellidae, Galatheidae, Heteropolypus ritteri, Laetmogonidae, Lycenchelys sp., Megalodicopia hians, Ophidiidae, Peniagone sp., and Xenophyophoroidea.

Remarks. Of the 43 previously described species of Cladorhiza, very few have been described that have the parasol morphology of the species described herein. Those Cladorhiza species that are most similar include C. corona Lehnert et al., 2005, C. longipinna Ridley & Dendy, 1886, and C. mirabilis Ridley & Dendy, 1886. Cladorhiza corona is quite distinct and differs from C. mexicana sp. nov. both in having the ‘crown’ morphology and in lacking pseudoamphiasters. Cladorhiza longipinna differs morphologically and in its lack of pseudoamphiasters. Cladorhiza mirabilis was described from a specimen collected in the South Pacific and its description differs greatly both in size and spiculation. For example, Cladorhiza mirabilis has a longitudinal length (measured from end to end of parasol edge filament) of 6 mm, whereas this longitudinal length on C. mexicana is ~ 8.8 cm. Similar to C. mexicana sp. nov., C. mirabilis does have pseudoamphiasters but they are of a much larger size (230 µm in C. mirabilis vs. 109 µm in C. mexicana sp. nov.). Pseudoamphiasters in C. mirabilis also appear to be symmetrical with alae length on each end of the pseudoamphiasters being equal whereas they appear asymmetrical in C. mexicana sp. nov. owing to the difference in alae length on each side. In general, sigmas appear to be larger in C. mirabilis as well. Finally, C. mexicana sp. nov. was collected from basaltic pillow lavas and, presumably, was attached via a holdfast disc whereas C. mirabilis was retrieved from abyssal sediments and has root-like rhizoids as its point of attachment.