Published online by Cambridge University Press: 11 May 2009
The distribution of 18 common epizoic species between clumps of Nemertesia antennina is examined with reference to their dispersal behaviour and, for selected epizoites, to the occurrence of other epizoic species. Dispersal of the tubicolous amphipods Ericthonius brasiliensis, Jassa falcata and Corophium sextoni and the caprellids Pseudoprotella phasma and Caprella linearis by a proportion of the adult animals, and by some animals after mating, was suggested. This behaviour may establish and perpetuate aggregations of these amphipods since brood-mates, and some of their descendants, remain on their natal hydroid clump. Five of the nine species considered that disperse as planktonic larvae have aggregated dispersions and for two of these species, Rissoa parva and Cingula semistriata, gregariousness of their larvae at settlement was considered an important influence on their distribution. Comparisons between the distributions of selected epizoic species suggest that in only a few cases, notably where branching bryozoans may give protection to potential prey species, is the distribution of one species influenced by the occurrence of another.