In vitro release of the anti-gonadotropic hormone, schistosomin, from the central nervous system of Lymnaea stagnalis is induced with a methanolic extract of cercariae of Trichobilharzia ocellata.

Abstract

Infection with digenetic trematodes causes an inhibition or complete cessation of fecundity in their intermediate hosts, freshwater snails. It has been demonstrated in the host-parasite combination Lymnaea stagnalis-Trichobilharzia ocellata that the action of the female gonadotropic hormones upon their target organs is inhibited by the peptide schistosomin. Schistosomin is produced in the central nervous system of the snail and released upon parasitic infection. In order to study the in vitro release of schistosomin, a bioassay was developed. Central nervous systems were incubated with either an acetic acid or a methanolic extract of larval stages of Trichobilharzia ocellata (miracidia, mother sporocysts, cercariae). The incubation media were chromatographed using HPLC and released schistosomin (-like material) was tested for bioactivity in the calfluxin bioassay. The in vitro release of schistosomin was only induced with a methanolic extract of cercariae. The nature of the cercarial factor is discussed.