Ophiomusa lymani

Ophiomusa lymani (W.C. Thomson, 1873)

Fig. 5A–G

Ophiomusium lymani Thomson, 1873: 174, figs. 32–33.— Lyman 1882: 90.— Mortensen 1933b: 394.— Vadon & Guille 1984: 584.— Paterson 1985: 147–148, fig. 58.— Guille & Vadon 1986: 169.— Alva & Vadon 1989: 843.— Rowe & Gates 1995: 434.

Ophiomusa lymani.— Hertz 1927b: 103–105.

Ophiomusa lymani.— Olbers et al. 2019: 72–74, fig. 50–51.

Material examined. MD 50 CP124, MNHN IE.2009.1617 (2). MD 50 DC137, MNHN IE.2009.1616 (2).

Distribution. Arctic (95–2448 m), NW Atlantic (595–3506 m), NE Atlantic (1011–4829 m), NW Pacific (110– 2310 m), NE Pacific (62–2904 m), W Atlantic (101–1965 m), E Atlantic (415–4088 m), W Indian (457–2312 m), E Indo-W Pacific (300–3343 m), E Pacific (730–2599 m), S America (700–3394 m), S Africa (1340–2780 m), S Australia (848–3050 m), New Zealand (495–3029 m). SPA (1340–2000 m).

Remarks. Unlike many other widespread bathyal complexes, Ophiomusa lymani has always been identified as a single species that has been reported from all oceans (450–4800 m) except the Arctic and subantarctic/Antarctic. It has been previously reported from across the southern Indian Ocean from South Africa (Olbers et al. 2019), around Madagascar (Guille & Vadon 1986), Reunion (Vadon & Guille 1984), the SPA (Hertz 1927b) and Southern Australia (Rowe & Gates 1995).

The specimens from CP124 are large, 23 and 25 mm dd (Fig. 5A–D), and display all the classic characters of O. lymani, including the numerous tiny arm spines (Fig. 5C), more than three ventral disc scales, and granulated radial shields and marginal disc scales. The specimens from stn DC137 are small, 4 mm dd (Fig. 5E–G). They are identified as juvenile O. lymani on the basis of having tumid primary disc plates (see Schoener 1967), granulated disc plates including radial shields which are mostly contiguous, only three arm spines, middle one becoming hooked distally, and oval tentacle scales, associated with VAPs. At this size they are reminiscent of the O. scalare Lyman, 1878b group of species with a ventral disc surface that is dominated by a large pentagonal scale next to the oral shields which separates two tumid scales along the margin. However, O. scalare generally has smaller circular tentacle scales, disc scales may be partially covered in skin but not granulated, and the three arm spines are closely clustered together. Ophiomusa ultima Hertz, 1927b from east Africa (238–977 m) and O. africanum Koehler, 1909 from Cabo Verde (219 m) have a narrower oral shield and an upper arm spine (or two) that is separated from the others. On O. ultima the 2nd set of tentacle pores become isolated from the VAP with size, perforating the LAP, until they gradually close over and the VAP reduces in size. Ophiomusa africanum is only known from the 7 mm dd holotype, which has the second set of tentacle pores emerging through the lateral arm plate and no associated VAP.