By inhibiting reproductive
hormones, the
neuropeptide schistosomin produced by the snail Lymnaea stagnalis plays an essential role in parasitic
castration mediated by the schistosome parasite Trichobilharzia ocellata during late stage
infection. Here we report on the presence and expression of
schistosomin in the snail Biomphalaria glabrata, a prominent intermediate host of the parasite Schistosoma mansoni, one of the causative agents of human
schistosomiasis. The deduced
amino acid (aa) sequences from complementary DNAs (cDNAs) from B. glabrata contain
a 17 aa
signal peptide and a 79 aa mature
peptide with 62 -- 64% identity to
schistosomin from L. stagnalis. Ontogenic expression at the
protein and
mRNA levels showed that
schistosomin was in higher abundance in embryos and juveniles relative to mature snails, suggesting that
schistosomin is likely involved in developmental processes, not in reproduction. Moreover, expression data demonstrated that
infection with two different digenetic trematodes, S. mansoni and Echinostoma paraensei, did not provoke elevated expression of
schistosomin in B. glabrata from early stage
infection (4 days post-exposure; dpe) to patent
infection (up to 60dpe), by which time parasitic
castration has been accomplished. In conclusion, our data suggest that a role of
schistosomin in parasitic
castration cannot be established in B. glabrata infected with either of two trematode species.