Ophiocten lymani

Ophiocten lymani (Studer, 1882)

Ophiochiton lymani.— Studer, 1882: 22–23, pl. 3(10a–e).

Ophiocten lymani.— Matsumoto 1915: 89.

? Ophiocten hastatum.— Hertz 1927b: 66–67 [Non Ophiocten hastatum Lyman, 1878].

Material examined. Gazelle stn, 35° 26.6´S, 79° 42.3´E, 2908 m, 6/4/1875, syntype, ZMB Ech2539 (1).

Distribution. SPA (? 158–2908 m).

Remarks. Studer (1882) described Ophiochiton lymani from two Gazelle stations in the SPA EEZ, to the SE (2669 m) and NE (2908 m) of the SPA plateau. No further specimens have been recorded under this name, and there are no specimens in the MD50 material. This species was subsequently determined to be an Ophiocten species, close to the deep-sea O. hastatum Lyman, 1878 (Hertz 1927a). Indeed, Hertz (1927b) named several small (4–8 mm) specimens of Ophiocten from the SPA material as O. hastatum Lyman, 1878 (although, collected from 158 and 1463 m, they are very shallow records for this species and need to be re-examined). Various regional species have been progressively synonymised with Ophiocten hastatum (Koehler 1922a; Paterson 1985; O’Hara 1990) to form a widespread species across all major oceans. However, genetic evidence presented in Christodoulou et al. (2019 supplementary data) shows that this taxon is a complex of species, and that many of these synonyms need to be re-evaluated.

Within this complex, O. lymani is most similar to the types of O. australis Baker, 1979 in having very reduced or absent arm comb papillae and a reddish colouration when alive. The ‘hastatum’ material collected from off SW South Africa also lacks arm comb papillae (Olbers et al. 2019 fig. 62) and its status requires further work. Ophiocten pallidum Lyman, 1878, from the abyssal Southern Ocean south of Australia, also has rudimentary or lacking arm combs but has three short subequal arm spines. Conversely, the type of O. hastatum was described from a separate biome (subantarctic waters off Marion Island, 2577 m) and has well developed arm comb and papillae on the dorsal arm plates, like O. ludwigi Koehler, 1908. However, these forms are very similar across a range of characters and until we get additional genetic data from specimens from the SPA and/or South Africa, both O. lymani and O. australis are recognised here as valid species that occur at southern temperate latitudes.