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Document Type

Book Chapter


Virginia Institute of Marine Science


Vincent Guillory, Harriet Perry, Steve VanderKooy (eds.)

Publication Date


Book Title

Proceedings of the Blue Crab Mortality Symposium


Gulf State Marine Fisheries Commission


Ocean Springs, MS


Blue crabs, Callinectes sapidus, from the Delmarva Peninsula experience recurring epizootics of a pathogenic dinoflag ellate. The parasite, Hematodinium perezi , fulminates in late summer and autumn causing significant mortalities in high salinity embayments and estuaries. Mortality rates during epizootics a re difficult to estimate because dead crabs quickly deteriorate. Host mortality was investigated in naturally- and experimentally-infected crabs. Detection of the parasite, its proliferation in the hemolymph, and distribution in lower Chesapeake Bay were also examined. The dinoflagellate was highly pathogenic, killing 100% of naturally infected crabs, and 86% of inoculated crabs over 35 and 4 0 days, respectively. Inoculated hosts began dying 14 days after infection, with a median time to death of 30.3 + 1.5 d (se). Proliferation of the parasite was rapid at 20°C, with infections progressing to high levels over one to two week s. Detection of the parasite was, however, variable. In infection experiments so me hosts presented infections after two weeks while others were not detected until four weeks post inoculation. The dinoflagellate was prevalent in the seaside bays of the Delmarva Peninsula. In fall 1996, the prevalence of the disease along the Virginia portion of the Delmarva Peninsula varied from 20-50% in legal crabs. Prevalences of 1-30% were noted for crabs caught between Cape Henry and Cape Charles, i.e., the mouth of the bay. Th e mortality studies indicate that H. perezi represents a significant threat to the blue crab fisheries in high salinity estuaries and may preferentially infect mature females that move to higher salinities to breed .

Infection and mortality studies with Hematodinium perezi in blue crabs