The Cercaria of Allocreadium ictaluri Pearse (Digenea: Allocreadiidae)

The cercaria of Allocreadium ictaluri Pearse was reported from limpets, Laevapex fusca (Adams), in Lake Oberlin, an oxbow of Red River in Oklahoma, and Tippecanoe River in Indiana. The cercaria was fully described for the first time and clams were infected experimentally. The cercaria previously reported for A. ictaluri was the larva of a deropristiid, Skrjabinopsolus manteri Cable, which matures in the spiral valve of sturgeons. Allocreadium ictaluri Pearse, 1924, is an in- testinal parasite obtained by catfish when they ingest unionid clams containing metacercariae in their mantle. Seitner (1951) attributed the meta- cercariae to biocellate gymnocephalous cercariae that penetrate the mantle and encyst in the thick- ened border. Later, Peters (1957) found stylets in young metacercariae, proving that the larva of A. ictaluri is a biocellate xiphidiocercaria of the type that Looss (1894) claimed for A. isopo- rum, the type species, and Hopkins (1934) dem- onstrated for papillose allocreadiids.