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

¹ Aquaculture Program, Animal Science Department, University of California, Davis, CA 95616

Eggs of the estuarine shrimp, Palaemon macrodactylus, were studied under various conditions to determine their susceptibility to a known fungal pathogen, Lagenidium callinectes. Eggs exhibited no signs of fungal infection under normal conditions, but were infected when detached from the female or when the female's first pereiopods ("cleaning chelipeds") were excised. This implied that preening or egg removal by the first pereiopods 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. Similarly, 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 were found to inhibit a variety of pathogenic fungi, including six strains of Lagenidium callinectes, two strains of Halipthoros milfordensis and a freshwater Saprolegnia species.

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