Diversity of nematode assemblages along a Mediterranean deep-sea transect

The diversity of nematode assemblages along a Mediterranean transect off Calvl, Corsica, Mediterranean Sea (depth range 160 to 1220 m) was very high There was no clear trend in species diversity station depth, and diversity at the station located on the continental shelf was not markedly lower than that at the deep-sea stat~ons However, diversity decreased with increasing depth into the sediment As with the macrofauna, nematode assemblages in the Mediterranean are less diverse than in the Bay of Blscay The lower diversity in the Mediterranean is explained by a slight dominance of some species, while no species are dominant in the Bay of Biscay Generlc (betweengenus) diversity was much hlgher than the average species diversity within genera, ~ndicating that the high overall specles diversity was not caused by large numbels of closely related CO-existing species Since species abundances are low, mate location for amphimictically reproducing species can imposc an important metabolic cost on the organism However, there ale no indications that parthenogenesis is important In deep-sea nematodes