The life cycle and transmission dynamics of the larval stages of Hypoderaeum conoideum

The morphology of the different larval stages and life cycle of Hypoderaeum conoideum (Trematoda: Echinostomatidae) are described. The freshwater snai l species Lymnaea peregra (Gastropoda: Lymnaeidae) serves as the natural fi rst intermediate host and this and L. corvus serve as experimental first in termediate hosts. These and other freshwater snails, such as Physella acuta and Gyraulus chinensis, in turn serve as second intermediate hosts. Adult worms were obtained from chicks and ducks, but not from rats, mice and gold en hamsters. The morphology of the larval stages is compared with previous work on H. conoideum. Several aspects of the biology of the life history st ages are described with emphasis on the transmission dynamics of the free-l iving stages. Differential suitability of the snail species that may act as first and/or second intermediate hosts is studied and discussed.