Distribution outside the British Isles

As noted previously, brittlestar beds are particularly common around the UK and Ireland, but examples are known from elsewhere. The Ophiothrix/Ophiocomina beds of the western English Channel extend to the French side (Allain, 1974; Holme 1984) as far as the Brittany coast (Hily, 1991). Dense populations of Ophiothrix fragilis have also been recorded from the Oosterschelde Estuary in the Netherlands (Leewis et al., 1994).

Beds of Ophiocomina nigra are known from the coast of Portugal (Saldanha, 1973) and from the Mediterranean of Algeria (Allain et al., 1978). The Mediterranean species Ophiothrix quinquemaculata was found at densities of up to 88 m-2 at 42 - 70 m depth at Banyuls-sur-Mer on the southern coast of France (Guille, 1964). In the Gulf of Trieste, Adriatic Sea, this species occurs on muddy and sandy substrata at densities of usually 50 - 250 m-2, with local aggregations up to 300 m-2 (Fedra et al., 1976). At these densities the brittlestars are the most abundant large epifauna in their communities, but are still relatively sparse compared with some of the populations recorded around the British Isles. Czihak (1954) found the small brittlestar Ophiactis virens at a very high density of 10,000 - 13,000 m-2 in a submarine cave in the Gulf of Naples.

Outside the north-eastern Atlantic area, the best-known example of a dense epifaunal brittlestar population is that studied by Aronson & Harms (1985) in Sweetings Pond, an inland salt water lake in the Bahamas. Here, the species Ophiothrix oerstedi was found at up to 434 individuals m-2, probably because predatory reef fish were absent from the lake. Aggregations of other species are also reported from the Antarctic and sub-Antarctic (Morison, 1979; Fratt & Dearborn, 1984), and from Japan and California (sources quoted in Warner & Woodley, 1975), but little is known of the beds in these areas.

Paleozoic-type epifaunal communities on soft substrata are relatively rare today in shallow, coastal waters but persist to a greater extent in the deep sea, to which groups such as the stalked crinoids are now confined. Brittlestars are an important element of the deep sea fauna (Gage & Tyler, 1991) although populations do not approach the densities recorded in shallower, more productive seas. For example, in Japan, Fujita & Ohta (1990) recorded Ophiura sarsii at densities of 30 to several hundred individuals m-2 at depths of 100 - 740 m. These beds were thought likely to extend around much of northern Japan in the 200 - 600 m depth range.

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