THE FUNGUS LAGENIDIUM CALLINECTES COUCH (1942) ON EGGS OF THE BLUE CRAB IN CHESAPEAKE BAY

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Abstract
A parasitic fungus (Lagenidium callinectes) occurs commonly on the egg mass (sponge) of the blue crab (Callinectes sapidus) in Chesapeake Bay. Studies were carried out to ascertain the conditions of existence of the parasite throughout the egg mass and to locate areas of Chesapeake Bay in which it occurs. Collections of sponges were made at commercial crab docks; lactophenol was used for clearing the eggs. The fungus was found to be a peripheral parasite of the egg masses; it spreads rapidly over the surface of a sponge but seldom penetrates to eggs deeper than 3 mm. Crab eggs are susceptible to infection in all stages of development. Infection is heavier in older egg masses due to longer exposure of these eggs. Peripheral infection does not retard development of eggs in the interior of the mass. In the laboratory, transmission of infection from parasitized eggs to healthy eggs is rapid; development of the fungus proceeded in salinities from 5 to 30 p.p.t. A nemertine, Carcinonemertes carcinophila, is present in the egg masses and shows periodic fluctuations similar to the fungus. Infection was found to be heaviest in the waters of southern Chesapeake Bay where the greatest population of spawning crabs is found. Results indicate that L. callinectes does not constitute a serious biological factor in fluctuations of the crab population.