DAO 43:139-152 (2000)  -  doi:10.3354/dao043139

Epizootiology of the parasitic dinoflagellate Hematodinium sp. in the American blue crab Callinectes sapidus*

Gretchen A. Messick1,**, Jeffrey D. Shields2

1National Ocean Service, Center for Coastal Environmental Health and Biomolecular Research, Cooperative Oxford Laboratory, 904 S. Morris St., Oxford, Maryland 21654-9724, USA
2Virginia Institute of Marine Science, The College of William & Mary, PO Box 1346, Gloucester Point, Virginia 23062, USA
*Disclaimer: The mention of trade names does not reflect endorsement by the National Ocean Service nor Virginia Institute of Marine Science **E-mail:

ABSTRACT: Hematodinium sp. is a parasitic dinoflagellate that infects and kills blue crabs Callinectes sapidus. Periodic outbreaks of dinoflagellate infections with subsequent high host mortalities prompted a study of the epizootiology and distribution of the crab pathogen. Hemolymph samples from over 13000 crabs were assessed for infections over 8 yr. Moderate to high prevalences were found at several locations along the Atlantic and Gulf coasts of the United States. In the coastal bays of Maryland and Virginia, prevalence followed a seasonal pattern, with a sharp peak in late autumn. Infections were significantly more prevalent in crabs measuring less than 30 mm carapace width; host sex did not influence prevalence. Prevalences were highest in crabs collected from salinities of 26 to 30”; no infected crabs were found in salinities below 11”. Intensity of infection did not vary among crab sizes, molt stages, or sexes. Naturally and experimentally infected crabs died over 35 and 55 d in captivity, with a mean time to death of approximately 13 and 42 d, respectively. Several other crustaceans, including gammaridean amphipods, xanthid (mud) crabs, and the green crab Carcinus maenus, were found with Hematodinium-like infections. Considering its widespread distribution and high pathogenicity, we suggest that Hematodinium sp. represents a significant threat to blue crab populations in high salinity estuaries along the Atlantic and Gulf coasts of the USA.


KEY WORDS: Hematodinium sp. · Callinectes sapidus · Seasonality · Size · Salinity · Disease · Dinoflagellate


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