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Pink shrimp, Penaeus duorarum Burkenroad, from natural populations in Biscayne Bay and from cultured populations in ponds operated by the University of Miami at Turkey Point, Florida, were examined for parasites during the summer of 1969. Parasites, with percentage incidence in parentheses, found in pond‐reared shrimp were: the gregarines Cephalolobus penaeus Kruse, 1959 (11%), and Nematopsis penaeus Kruse, 1959 (20%); the larval cestodes Prochristianella penaeus Kruse, 1959 (17%), and Polypocephalus sp. (0.7%). Additional parasites found in wild shrimp but absent in pond‐reared samples were: the microsporidian Thelohania duorara Iversen and Van Meter, 1959 (8%); an unidentified cestode of the genus Prochristianella (14%): and a larval nematode, probably Contracaecum habena (Linton, 1900) (13%). The incidence of parasitism in pond‐reared shrimp is compared to that previously recorded from wild P. duorarum collected from Tortugas and Biscayne Bay. Absence or reduced incidence of certain parasites in pond‐reared P. duorarum is discussed.

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Preliminary experiments indicate that mice inoculated with cercariae of Schistosoma mansoni that have been exposed to cobalt-60 radiation in the range of 2500 to 3000 rep develop immunity to reinfection with nonradiated cercariae.