Bitter crab disease studies: observations on seasonality, mortality, species susceptability and life history

Thesis (M.S.) University of Alaska Fairbanks, 1992Incidence and average intensity of Bitter Crab Disease (BCD) in Auke Bay Tanner crabs CChionoecetes bairdi) were significantly greater during June through September of both 1989 and 1990 then during October through May. BCD is a chronic but fatal disease; crabs did not develop immunity and often died from secondary bacterial and ciliate infections. Total mortality exceeded incidence and was not significantly different between summer and winter seasons or between years. BCD appears to be host specific: red king crabs (Paralithodes camtschaticus) and Dungeness crabs (Cancer maaister) did not contract BCD post-injection. BCD amoeboid stages consistently caused disease in Tanner crabs when injected into the hemocoel, while dinospore stages did not. Waterborne challenges did not cause disease. BCD parasites did not occur intracellularly, remaining within the hemal and vascular systems. Parasites exited the host via gills and possibly esophagus. The life cycle of BCD dinoflagellates outside their hosts remains incompletely described