PARASITES AND SYMBIONTS OF WILD MUD CRABS SCYLLA-SERRATA (FORSKAL) OF POTENTIAL SIGNIFICANCE IN AQUACULTURE

A total of 130 wild mud crabs, Scylla serrata, from Moreton Bay, Queensland, were examined to determine if there were parasites or symbionts that could cause problems in aquaculture. Of 10 parasites and symbionts found, four were potential pathogens. The blood protozoan, Haematodinium sp. is similar to parasites that have killed crabs elsewhere. The ciliates, Epistylis sp. and Acineta sp., and the barnacle, Octolasmis cor, were common on the gills and may increase stress through respiratory distress. Both of the ciliates showed seasonality, with Epistylis.sp. abundant in summer and Acineta sp. abundant in winter. Haematodinium sp. was present at low prevalence throughout the year. The prevalence of Octolasmis cor was significantly higher in female crabs than in males. Mean intensity was positively correlated with crab size for O. cor and for the metacestode of Polypocephalus sp. The prevalence of Epistylis sp. and the barnacle, Chelonibia patula, varied with the moult stage of the crab.