Effect of Schistosoma mansoni infection on fecundity and perivitelline fluid composition in Biomphalaria glabrata.

Egg production in the snail, Biomphalaria glabrata, infected with Schistosoma mansoni declined on day 23 postinfection, and was significantly lower than uninfected control snails by day 28 and thereafter. Protein and galactogen content of eggs produced by infected snails did not change during the period of reduced fecundity. This suggests that decreased hemolymph nutrient levels (rather than depleted albumen gland reserves) are responsible for inhibition of snail egg production. Growth rates of infected and uninfected snails were indistinguishable from days 14 through 35 postinfection. The hatching success of eggs produced by infected snails decreased slightly beginning at day 21 postinfection.