Amphiura brevispina Marktanner-Turneretscher 1887

Amphiura brevispina Marktanner-Turneretscher, 1887

Amphiura brevispina Marktanner-Turneretscher, 1887: 301, pl. 12(14–15).— Koehler 1907b: 299.

Amphiura capensis.—Clark, A.M. 1976: 258–259 [Non Amphiura (Amphiura) capensis Ljungman, 1867].

Distribution. SPA (0–2 m).

Remarks. A.M. Clark (1976) identified small amphiurids collected from the coastal zone around Île Saint-Paul and Île Amsterdam as the South African species Amphiura capensis, apparently unaware that an earlier species A. brevispina Marktanner-Turneretscher, 1887 had been described from Île Saint-Paul on the Novara expedition in 1857 and later collected by the La Dive expedition in 1872 (Koehler 1907b). The two species are very similar, having oblong proximally divergent radial shields, 1/6 dd in length, small disc scales, often sparser near the oral shields, DAPs slightly wider than long, one small tentacle scale, spear-head-shaped oral shields and a small conical adoral shield spine (distal oral papilla). There are generally 4–5 small arm spines at 3–5 mm dd, the middle ones slightly flattened and truncate. Large 11 mm dd specimens of A. capensis from South Africa can have up to 7 arm spines (Olbers et al. 2019).

Amphiura capensis broods its young(Mortensen1933a)and presumably A.brevispina does as well.Consequently, the common ancestor of A. capensis-brevispina presumably rafted to SPA in kelp holdfasts or on wood. Interestingly, A. capensis has also been collected from the remote island of Tristan da Cunha in the South Atlantic (Mortensen 1941). Unfortunately, we do not have DNA data for these populations. However, phylogeographic data is available for the benthic egg-laying asteroid Parvulastra exigua (Lamarck) with a similar distribution (Hart et al. 2006; Waters & Roy 2004). Network analyses of COI sequences showed that Parvulastra specimens from Amsterdam Island were phylogenetically distinct from clades on the South African and Australian coasts (Hart et al. 2006; Waters & Roy 2004). Presumably, long distance rafting is an infrequent event allowing the island populations to diverge from their African source populations. Until there is genetic data for this Amphiura, the conservative approach is taken here of recognising A. brevispina as an endemic species of the SPA islands.

Except for the next species, the numerous other Amphiura specimens (<2.5 mm dd) collected by the MD50 expedition (Table 1) were small and damaged and not readily identifiable.