a1 Wellcome Marine Laboratory, University of Leeds, e Robin Hood's Bay, Yorkshire
Seventy-two holdfast samples of the kelp Laminaria hyperborea (Gunn.) Fosl., from fifteen approximately equidistant sites along the North-East coast of Britain, from St Abbs in Berwickshire to Flamborough Head, have been taken during the course of one spring-tide period. The nematode fauna of these samples (20,744 specimens of 61 species) has been examined and the data are presented in such a way as to facilitate comparison with previous work. The fauna in the North Sea is dominated by large enoploid species. Enoplus communis Bastian, Anticoma acuminata (Eberth), Thoracostoma coronatum (Eberth), Phanoderma albidum Bastian and Pontonema vulgaris (Bastian) are regularly abundant. The minor contribution of the family Monohysteridae indicates that silt is of little importance to the nematode fauna in exposed localities. The holdfast-dwelling nematodes are generally epigrowth feeders or omnivores, the latter exploiting the sediment-feeding niche apparently unavailable to specialized deposit feeders. Species with short body setae, body length above 1·5 mm, having smooth cuticles and possessing some visual mechanism are dominant. It is upheld that algal structure per se is of primary importance in determining the different nematode communities found to exist in algae of different growth forms, and to account for the similarity shown between the faunas inhabiting similar algal growth forms from widely separate geographical areas and differing levels on the shore. It is suggested that habitat-component generic keys might facilitate investigation of unknown regions.