EGGS OFPALAEMON MACRODACTYLUS:III. INFECTION BY THE FUNGUS,LAGENIDIUM CALLINECTES

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Abstract
Eggs of the estuarine shrimp, P. macrodactylus, were studied under various conditions to determine their susceptibility to a known fungal pathogen, L. callinectes. Eggs exhibited no signs of fungal infection under normal conditions, but were infected when detached from the female or when the female''s 1st pereiopods (cleaning chelipeds) were excised. Preening or egg removal by the 1st pereiopods probably halted infection or obviated detection of the fungus. Nutrient addition increased the number of infections and decreased the time to infection. Fertilized eggs were less susceptible to infection than unfertilized, probably the result of the hardened fertilization membrane restricting fungal penetration. Older embryos with progressively hardened coats were also less susceptible. Defense may have also been provided by antifungal bacteria isolated from embryo surfaces. Two of these epizooic bacteria belong to the marine genus, Alteromonas, and release extracellular enzymes, including lipase and chitinase. Both bacteria inhibited a variety of pathogenic fungi, including 6 strains of L. callinectes, 2 strains of Halipthoros milfordensis and a freshwater Saprolegnia sp.

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