The killifish, fundulus heteroclitus, second intermediate host of the trematode, Ascocotyle (Phagicola) dimunuta

Ascocotyle (Phagicola) diminuta was described by Stunkard and Haviland (1924)from the intestine of wild rats collected at the Clason Point dump near New York by the City Board of Health. Feeding experiments have demonstrated that metacercariae encysted in the gills of the common killifish, Fundulus hetero clitus, are stages in the life-cycle of this parasite. The larvae have been found also, although rarely and in small numbers, in the gills of the striped killifish, Fundulus majalis. Since both species of Fundulus are susceptible, it appears probable that the habits of F. heteroclitus occasion greater exposure of this species to the cercariae. It is possible that infection of the fishes occurs during the spawning season when they are in water of low salinity. The asexual stages of these trematodes and the mollusks which harbor them are yet unknown.