|Title||The cercarial type in the genus Allocreadium|
|Publication Type||Journal Article|
|Year of Publication||1957|
|Journal||Journal of Parasitology|
|Issue||5, Sec. 2|
Since the writer reported the retention of a well developed stylet in mature progenetic adults of Allocreadium neotenicum from water beetles, a complete stylet has also been found in mature specimens of A. lobatum from Semotilus atromaculatus in both Michigan and Indiana. In A. ictaluri, search for a stylet showed it to be absent in adults and most metacercariae, but stylets were found in very young cysts in unionid mussels, which are known to be the second intermediate hosts of A. ictaluri. Although not yet proved experimentally to be the young metacercariae of A. ictaluri, the cysts with stylets are among the smallest in a continuous series leading to metacercariae which unquestionably are immature A. ictaluri. Unlike A. neotenicum and A. lobatum, A. ictaluri sheds the stylet, which was found in various stages of disintegration in the cyst. The discrepancy as to the type of cercaria in the genus Allocreadium reported in previous studies thus seems to be resolved by establishing the larval type as an ophthalmoxiphidiocercaria.