Effects of elevated haemolymph levels of the female gonadotropic dorsal body hormone on the cercarial production ofTrichobilharzia ocellata inLymnaea stagnalis

Abstract

Juvenile specimens ofLymnaea stagnalis were exposed to 0 or 4 miracidia ofTrichobilharzia ocellata. The effects of experimentally raised haemolymph levels of the female gonadotropic dorsal body hormone (DBH) on female reproduction of the host were studied, and the effect on the production of cercariae was determined. Operations of snails and implantations of endocrine dorsal bodies (DB) were performed shortly after infection in three successive experiments. DB implants in non-infected snails (+DB snails) advanced the onset of ovipository activity and enhanced oocyte production compared to that in appropriate controls. In this the increase in haemolymph level is proved of DBH produced by the DB grafts. Infected +DB snails did not show any increase in the various aspects of female reproductive activity. DB implants also did not affect the production of cercariae. Thus the blocking action by the parasites on the development of the reproductive system could not be counteracted by elevating the DBH level in the haemolymph. These results are consistent with the hypothesis that the parasites intervene in the reproductive activity of the host at the level of the targets of the gonadotropic hormones.