Ophiura ljungmani

Ophiura ljungmani (Lyman, 1878b)

Fig. 3A–B

Ophioglypha ljungmani Lyman, 1878b: 71–72, pl. 3(77).

Ophiura ljungmani.— Martynov & Litvinova 2008: 80, fig. 1d.— Olbers et al. 2019: 87–88, fig. 64–65.— Stöhr & O’Hara 2021: 514–516, fig. 2f–h.

Ophiura (Ophiura) ljungmani.— Paterson 1985: 118–120 fig. 44.— Alva & Vadon 1989: 841, fig. 8a–b.

Material examined. MD 50 CP193, MNHN IE.2009.1623 (1).

Distribution. Arctic (310–2913 m), NW Atlantic (? 68–4707 m), NE Atlantic (789–4150 m), W Atlantic (? 46– 1965 m), E Atlantic (425–2550 m), S Africa (2688–3906 m). SPA (2800–3075 m).

Remarks. There is a lower bathyal species complex with one described species (O. ljungmani) in the North and South Atlantic (101–4700 m), including South Africa (2688–3906 m, Olbers et al. 2019), a second (O. spinicantha McKnight, 2003) off SE Australia, the Tasman Sea, and New Zealand (1650–4130 m), and a third (O. bathybia H.L. Clark, 1911) from Japan (Stöhr & O’Hara 2021). The first two species were separated by McKnight (2003) by the number of arm spines (two in O. spinicantha and three in O. ljungmani) but this depends on the definition of the elongated outer tentacle scale which is interpreted as a lower arm spine on O. ljungmani but as a tentacle scale by McKnight (2003). Perhaps the two species can be separated by the length of the upper arm spine, which is subequal to lower spines on O. spinicantha but two times as long in O. ljungmani. The upper arm spine is notably longer on the 9.5 mm dd MD 50 specimen, hence the identification as O. ljungmani. Both O. spinicantha and O. ljungmani can have long sparse disc spines and an opposing arm comb on the arm plates.

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TABLE 1. (Continued)

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TABLE 1. (Continued)

The massive bathymetric range reported for O. ljungmani (e.g., Paterson 1985) is suspect. Some of the shallowest Western Atlantic records are actually O. acervata (Lyman, 1869) or O. fallax Cherbonnier, 1959, which also have eland-horn shaped radial shields. Re-examination of some of the very shallow records of O. ljungmani from Mexican anchialine caves reported by Bribiesca-Contreras et al. (2013) and Márquez-Borrás et al. (2016) showed that they are O. fallax. Moreover, the Bribiesca-Contreras et al. (2013) record of O. sarsii (Lütken 1855) from Mexico (283 m) is an O. acervata. The three species differ in their arm comb, arm spine length and shape of the VAPs and DAPs. Ophiura acervata and O. fallax differ from O. ljungmani in having dimorphic arm comb papillae, which abruptly change from being short, square and contiguous on the lateral side of the arm to spine-like dorsally (see Cherbonnier 1959 fig. 7D). The upper arm spine on O. ljungmani is twice the length of the two lower ones but still only two-thirds the length of the segment. On O. acervata the arm spines are tiny, at most half segment long, with the middle one often a little shorter than the others. On O. fallax the upper arm spine is approximately a segment long with both the lower two just a little shorter. The DAPs on Ophiura acervata tend to become separated by mid-arm (see Benavides-Serrato et al. 2011) but are largely contiguous on the other two. Ophiura fallax lacks the pronounced distal point that occurs on the ventral arm plates of the other two species. It also has a strong mottled brown colouration on its dorsal side (see Márquez-Borrás et al. 2016).

Even with the removal of the coastal records, the bathymetric distribution of O. ljungmani is suspiciously large. Based on examples from other species complexes, future research may find separate genetic species at different depth ranges. The type locality of O. ljungmani is off Brazil in 640 m. The name Ophiura legata Lyman, 1878, currently considered a synonym of O. ljungmani, is available for a mid to lower bathyal species if required, as the type locality is from the NW Atlantic Ocean at 2511 m.