Ophiomyxa vivipara Studer, 1876

O’Hara, Timothy D. & Thuy, Ben, 2022, Biogeography and taxonomy of Ophiuroidea (Echinodermata) from the Îles Saint- Paul and Amsterdam in the southern Indian Ocean, Zootaxa 5124 (1), pp. 1-49 : 32

Ophiomyxa vivipara Studer, 1876

Fig. 13A–B

Ophiomyxa vivipara Studer, 1876: 462 .— Mortensen 1933a: 301–304, fig. 27–29.

Ophiomyxa vivipara var capensis Mortensen 1936: 242 .

Ophiomyxa vivipara capensis .— Olbers et al. 2019: 155–156, fig. 146–147.

Material examined. MD 50 CP7, MNHN IE.2009.1605 (6). MD 50 DC108, MNHN IE.2009.1606 (24). MD 50 CP145, MNHN IE.2009.1607 (3).

Distribution. S America (6–507 m), W Atlantic (94–156 m), S Africa (80–755 m), W Indian (373–1179 m), E Indo-W Pacific (385–888 m), S Australia (522–2170 m), New Zealand (150–1408 m). SPA (460–1680 m).

Remarks. The numerous MD 50 specimens ( Fig. 13A–B ) measure up to 11.8 mm dd and have the thin ovalto-trapezoid perforated unfragmented DAPs that cover the vertebrae that are diagnostic for the O. vivipara - O. serpentaria Lyman, 1883 complex of species (see Mortensen 1933c, fig. 1–2). Analysis of COI sequences ( O’Hara et al. 2014), showed that O. serpentaria specimens from the North Atlantic form a distinct clade to O. vivipara , as do populations from subtropical SW Australia and NE New Zealand, but O. vivipara sequences from the Falkland Islands, Tristan da Cunha, South Africa, Coral Seamount on the SW Indian Ridge, SE Australia, New Zealand and the Macquarie Ridge were not distinguishable. However, there are inter-population differences in life history. Specimens from off South America brood juveniles in their bursal sacs but specimens in other regions do not ( Mortensen 1933c, 1936; O’Hara et al. 2013). Mortensen (1936) suggested that the number of segments at the base of the arm that only have one arm spine was a way of distinguishing South American (one segment) from South African specimens (5–6 segments). However, in our experience this result is not consistent across all specimens from these regions. The current specimens have one arm spine only for the first segment, however, despite having mature gonads they show no sign of bursal viviparity.

Figures

FIGURE 13. (A–B) Ophiomyxa vivipara, MNHN IE.2009.1606, A: dorsal and B: ventral views. (C–D) Ophiactis abyssicola, MNHN IE.2009.1582, C: dorsal and D: ventral views. (E–I) Amphiura remota sp. nov., holotype, MNHN IE.2019.4748, E: dorsal outline, F: dorsal, G: ventral views, with H: an inset showing the denticulate disc scales. (I-J) MNHN IE.2009.1537 (non type), I: ventral view of four-rayed specimen, J: inset showing the lateral thorn at the arm spine tip.