Stephanohelia sp.

Pica, Daniela, Cairns, Stephen D., Puce, Stefania & Newman, William A., 2015, Southern hemisphere deep-water stylasterid corals including a new species, Errinalabrosa sp. n. (Cnidaria, Hydrozoa, Stylasteridae), with notes on some symbiotic scalpellids (Cirripedia, Thoracica, Scalpellidae), ZooKeys 472, pp. 1-25 : 3

Taxon classification Animalia Anthoathecata Stylasteridae

Stephanohelia sp. Figure 1

Material studied.

Three colonies of sample MNHN IK 2010-152: expedition MUSORSTOM 4 N/O Vauban, Sta. CP194, 18°53' S, 163°22' E, New Caledonia, 550 m depth 19 September 1985 (in ethanol).

Description.

Coral colonies arborescent, up to 8 cm long and 7 cm wide, with the basal branches up to 1.5 cm in diameter (Figure 1a). They are characterised by few main branches that are uniplanar around which several polychotomously tiny branches originate, formed by two to five branchlets (Figure 1b). The tiny branches are characterised by small abcauline spines (Figures 1b, c), up to 20 µm tall, mainly on the lateral edges. The branches are oval in cross-section. The tiny branches on both faces of the main branches are often anastomose, forming a gallery, which is caused by a commensal polychaete (Figure 1a). The colonies are attached to the substrate by an incrusting base. The colour of the coenosteum is white (Figure 1a). The coenosteal texture is linear-imbricate, composed of platelets irregular in shape and showing an alternating polarity (Figure 1d). The coenosteum is pierced by numerous coenosteal pores, 15-22-30 µm in diameter (Figure 1d). The strips are not well defined. The coenosteum is white.

Gastropores are circular, 100-175-230 µm in diameter, occurring exclusively at branching axils (Figure 1e). The gastropore tubes are cylindrical to conical in apical branches where they are less deep. The gastrostyle tips are visible on the coenosteum surface. The gastrostyles are robust and tree-like in shape without ridges and ornamented with multi-tipped spines (Figure 1f). The gastrostyles measure 96-170-205 µm in length and 50-80-100 µm in diameter (L:D=1.8-2.6). A ring palisade is not present. The dactylopores are flush with coenosteum and aligned on branch edges (Figure 1e). They are circular in shape and 40-60-95 µm in diameter. Dactylostyles are absent.

The female ampullae are round, superficial, 600-820-900 µm in diameter, and have a smooth surface (Figure 1g). They are distributed uniformly around the branches. Male ampullae are 400-510-600 µm in diameter and characterised by a round depression with a small central dome (Figure 1b). The domes vary in shape and have a highly perforate surface, usually with an apical pore (Figure 1b).

Remarks.

The characteristic shape of the colonies with polychotomous branching, the presence of the gastropores exclusively at branch axils, the large gastrostyles and the absence of the ring palisade and the dactylostyles are characteristic for Stephanohelia . This species differs from the type species, Stephanohelia praecipua , mainly in the gastrostyle shape. In fact, Stephanohelia praecipua has a gastrostyle characterised by a main basal shaft with a very expanded midsection and a slender tip. The scarcity of the analysed material is insufficient to enable the description of a new species.