THE LIFE-HISTORY, ULTRASTRUCTURE, AND EXPERIMENTAL TRANSMISSION OF HEPATOZOON CATESBIANAE-N COMB, AN APICOMPLEXAN PARASITE OF THE BULLFROG,RANA-CATESBEIANA AND THE MOSQUITO, CULEX-TERRITANS IN ALGONGUIN-PARK,ONTARIO

Gametogenesis and sporogonic development of a haemogregarine parasite of bullfrogs (Rana catesbeiana) was observed in cells of the Malpighia n tubules of laboratory-reared Culex territans that had fed on natural ly infected bullfrogs. Mature oocysts, which varied considerably in si ze, were multisporocystic with ellipsoidal sporocysts that contained 4 sporozoites. Sporogonic development was completed in about 20 days. M ature meronts were observed in the liver and merozoites in erythrocyte s of laboratory-reared bullfrogs that had been fed sporocysts 19 days previously. Similar attempts to infect laboratory-reared green and nor thern leopard frogs experimentally were unsuccessful, suggesting rathe r narrow specificity for this parasite in ranids. Gametogenesis and sp orogonic stages of this parasite were ultrastructurally similar to tho se described for Hepatozoon species. The parasite appears to be transm itted directly between bullfrogs and mosquitoes in the study area wher e Cx. territans feeds avidly on bullfrogs, which in turn were observed to naturally ingest these mosquitoes. Based on data presented in this study and the earlier description by Stebbins in 1903, the haemogrega rine parasite of bullfrogs was designated as a new combination, Hepato zoon catesbianae.