Biochemical basis for the continuous copulation of female Schistosoma mansoni

Sexual dimorphism in blood flukes of the family Schistosomatidae is marked, and until the male clasps the female in the gynaecophoric canal the female cannot attain sexual maturity 1 or migrate out of the liver 2 . When previously-paired egg-producing females are transferred to a new host without males, the vitelline cells necessary for egg production degenerate 3 . By means of sensitive fluorographic analysis of electrophoresed polypeptides, we have now found molecular evidence of an obligatory continuous relationship between the sexes in Schistosoma mansoni . The male worm retains little of the protein it produces in greatest abundance, and this protein is electrophoretically identical to the most abundant protein found in, but not synthesised by, the female.