EPIBIONTS AND INTERMOLT DURATION IN THE CRAB BATHYNECTES-PIPERITUS

Crustacean carapaces act as semipermanent hard substrata and can provi de useful information on moulting and other biological characteristics of the host. The patterns of epibiosis on the portunid crab Bathynect es piperitus were studied from samples collected by trawling off south ern Namibia between September 1987 and December 1988. Four species wer e identified as epibionts of this crab: the hydroid Stegopoma plicatil e, the polychaete Spirorbis patagonicus, the pedunculate cirriped Poec ilasma kaempferi and the bryozoan Nolella annectens. The patterns of d istribution of the 4 epibionts were studied on the carapaces of 318 ad ult male crabs. The number of individuals or colonies of each epibiont species was noted within each of 4 carapace areas. The hydroid occurr ed preferentially on the anterior part (46.9 %) of the carapace, where as the cirriped was found most commonly on the posterior (45.7 %). The polychaete was more common on the inferior parts (53.1 %) as was the bryozoan (80.3 %). The relationships between the size of the crab and the number of polyps (hydranths), the number of colonies and the numbe r of gonothecae of S. plicatile were also analyzed, since these parame ters could give an estimate of the intermoult period of the host. Base d on the identification of 3 cohorts in both the hydroid and cirriped populations, and taking into account their probable age, a minimal tim e for the intermoult period can be defined. Recruitment and reproducti on of the hydroid show that the process of colonization is continuous on all sizes of adult crab.