Amphiura filiformis O.F. Muller 1776

Amphiura filiformis (O.F. Müller, 1776)

Material examined. Al Idrisi MV, TTR12, stn AT412, 2 ind. (DBUA 001071.01); Mercator MV, TTR15, stn AT569, 10 inds. (DBUA 001072.01); stn AT575, 18 inds. (DBUA 001072.02); stn AT576, 17 inds. (DBUA 001072.03); MSM01-03, stn 237, 2 inds. (DBUA 001073.01); stn 241, 37 inds. (DBUA 001073.02); stn 242, 24 inds. (DBUA 001073.03); stn 267, 2 inds. (DBUA 001073.04); stn 287, 3 inds. (DBUA 001073.05); Fiuza MV, TTR14, stn AT566, 5 inds.; West of Gibraltar Strait, TTR14, stn AT552, 1 ind. (DBUA 001074.02); Pen Duick Escarpment, TTR12, stn AT407, 1 ind. (DBUA 001071.02); TTR16, stn AT602, 1 ind. (DBUA 001075.01).

Ecology and distribution. Amphiura filiformis is a common, predominantly shallow-water species of the north-Eastern Atlantic. It is known to occur from Norway to West Africa and also in the Mediterranean Sea at depths up to 1665 m (Paterson 1985). This species is often found sympatric with A. chiajei. Both species live buried in fine muddy sand but, unlike its congener, A. filiformis feeds in the water current extending its arms vertically 3–4 cm above the sediment surface (Vopel et al. 2003). In the Gulf of Cadiz A. filiformis co-occurred with A. chiajei in Mercator MV (Fig. 7 B). The highest density of A. filiformis (72–144 ind.m -2) occurs in the crater where only one specimen of A. chiajei was collected; the latter reaches densities of 60 ind.m -2 on the flank where the density of A. filiformis drops to 68 ind.m -2. Amphiura filiformis has also a much wider distribution and has been recorded in two other mud volcanoes (Al Idrisi and Fíuza) and in association with carbonate chimneys and crusts at two other sites (West of Gibraltar and Pen Duick Escarpment) at depths between 230 and 556 m.