The anti-gonadotropic neuropeptide schistosomin interferes with peripheral and central neuroendocrine mechanisms involved in the regulation of reproduction and growth in the schistosome-infected snail Lymnaea stagnalis

Parasitized snails display abnormal body growth and reduction or cessation of reproduction. Antigonadotropic neuropeptide schistosomin interferes with peripheral and central neuroendocrine mechanisms involved in the regulation of reproduction and growth in the schistosome-infected snail Lymnaea stagnalis. As soon as schistosomin is bound to its receptor, it might interfere with either the binding of the gonadotropic hormones to their receptors or with a membrane-bound component of the signal transducing system in the target cells resulting in a decrease of the gonadotropic hormone–receptor binding. The fact that schistosomin also enhances the adenylate cyclase (AC) activity in Ala-Pro-Gly-Trp-amide (APGW) neurons, which are involved in the innervation of the male copulatory system, suggests that it may also play a role in the effects of parasitosis on male reproductive activity in this hermaphrodite snail. The central and peripheral effects of schistosomin on reproduction-regulating neuroendocrine mechanisms strongly suggest that schistosomin is responsible for the inhibition of egg laying in L. stagnalis infected with T. ocellata. Growth and reproduction in Lymnaea show an inverse relationship, which is clearly disturbed in parasitized snails. The data obtained in this study indicate that schistosomin plays an important role by affecting this balance.