The mating behaviour of Echinostoma paraensei grown in mice

Adults of Echinostoma paraensei grown in mice were exposed to 3-H-tyrosine and transplanted to uninfected mice singly or with unexposed worms. The presence of sperm labelled with the radioactive tyrosine in the seminal receptacles of labelled and unlabelled worms recovered after 5 days indicated the mating pattern of this species. Of nine isolated, labelled worms recovered, four had self-inseminated (44%). Of the 39 unlabelled found with eight labelled worms, only eight exhibited labelled sperm for a cross-insemination rate of 21%. Six of these eight labelled worms had self-inseminated (75%) in addition to the cross-insemination. This pattern of mating is termed unrestricted, unlike the restricted mating seen in three species of eyeflukes, which will not self-inseminate in groups. In contrast to the other species of echinostomes investigated, very little sperm was found in the seminal receptacles of the serially sectioned E. paraensei. Adults were always found in the duodenum, even when transplanted in the ileum.