Ophiomyces undetermined

Ophiomyces sp. juvenile

Fig. 4E

Material examined. MD 50 DC91, MNHN IE.2009.1577 (25). MD 50 DC137, MNHN IE.2009.1578 (1).

Comparative Material. Ophiomyces grandis Lyman, 1879: BSS/638 DP, Eastern Bass Strait, slope, 102 km SE of Cape Conran, Victoria, 38° 29.5´S, 149° 32.4´E, 1630 m, 16/11/1981, MV F52776 (1). IN2018_ V06 / 007, Deep west of Pedra, 44° 20.844´S, 146° 56.82´E to 44° 22.596´S, 146° 56.76´E, 1745 m, 24/11/2018, MV F272372 (5). IN2018_ V06 / 074, East Maatsuyker flat, 44° 12.858´S, 146° 16.02´E to 44° 13.02´S, 146° 15.48´E, 1501 m, 3/12/2018, MV F271968 (7).

Remarks. The MD50 material is small with the largest specimen only 4 mm dd (Fig. 4E). All are badly damaged. The species of Ophiomyces are often distinguished by the number and position of tentacle scales and oral papillae (Litvinova 2001; O’Hara 1990; Paterson 1985), which however, can be variable depending on the age and condition of the specimens. The MD 50 specimens have only the distal oral papillae widened at the tip into the classic “hockey stick” shape, which is characteristic of O. grandis Lyman, 1879. However, the configuration of tentacle scales (one to two on the VAP and two on the LAP of basal segments reducing to one large LAP scale by the eighth segment) and the radial row of sparse disc spines, is characteristic of the Indo-Pacific species O. delata Koehler, 1904.

The type locality of Ophiomyces grandis Lyman, 1879 is off Tristan da Cunha at 1828 m. The other records from the southern hemisphere (see material examined) are from depths of 1000–1840 m. North Atlantic records on the other hand are much shallower (124–802 m, e.g., Ordines et al. 2019) and may represent a distinct species.

Two of the other genera in the Ophiohelidae, Ophiotholia and Ophiohelus, have diagnostic umbrella-shaped spines on the arms. The only other recorded genus in the family is Ophiothauma H.L. Clark, 1938, known from only one specimen of O. heptactis H.L. Clark, 1938 from off Port Essington, Coburg Peninsula, Northern Australia. Re-examination of the specimen (MCZ 4917) shows that it is (incredibly) a misidentified seven armed specimen of Ophiocomella sexradia (Duncan 1887) with the arms bent back over the disc. It has the characters of O. sexradia including tooth papillae and other ophiocomid oral armature (sensu Hendler 2018), spines along the genital slit, granules and short spines on the disc, robust arm spines that are dorsally elongated, etc. Consequently, Ophiothauma is a synonym of Ophiocomella A.H. Clark, 1939 and O. heptactis a junior synonym of O. sexradia.