Distribution outside the British Isles

All of the sea pen species and the major megafaunal burrowers have distributions which extend beyond British and Irish waters. Aspects of the ecology of several megafaunal burrowers have been studied elsewhere, notably in the Mediterranean (eg. Dworschak, 1982; Pervesler & Dworschak, 1985; Ziebis et al., 1996), but there have been fewer community-level studies using SCUBA or underwater video. However, recent towed camera surveys have shown that heavily-burrowed muds exist in several areas of the Adriatic and Aegean Seas (Marrs et al., 1996), indicating the presence of megafaunal communities comparable to those known from British waters. In the Adriatic, crustacean burrowers include Nephrops norvegicus, Jaxea nocturna, Upogebia spp. and the mantis shrimp Squilla mantis (Atkinson et al., 1997). The fauna also includes a large echiuran worm, Maxmuelleria gigas (Atkinson et al., in press). In much deeper water (> 400m) in the Evoikos Gulf, Aegean Sea, the mud bottom is burrowed by Nephrops norvegicus, Calocaris macandreae, Callianassa subterranea and (probably) Maxmuelleria gigas (Marrs et al., 1996). Unusually, the burrowing community here also includes large numbers of another echiuran worm, Bonellia viridis, a species previously recorded only from hard substrata (Hughes et al., in press). These observations suggest that analogues to the ‘Sea pens and burrowing megafauna’ biotope complex will eventually be found to be widespread on suitable substrata in the Mediterranean area.

Thalassinidean mud-shrimps are common and diverse in coastal and continental shelf sediments throughout the world. They have been found to be important agents of bioturbation in tropical lagoons (Suchanek & Colin, 1986; Suchanek et al., 1986). Other groups of burrowing megafauna have been barely studied outside north-west Europe, but there is no reason to doubt that future work will result in the identification of new species (eg. Rogers & Nash, 1996) and confirm the importance of these animals within sediment biotopes worldwide.

Various species of sea pen are common elements of the benthic fauna throughout the world’s oceans, from shallow coastal waters to the deep sea (eg. Langton et al., 1990). The few detailed studies of their ecology refer to species found on the Pacific coast of North America (Birkeland, 1974; Kastendiek, 1976; Davis & Van Blaricom, 1978). Where relevant to the British species, these will be discussed in Chapters IV and V.

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