Influence of larval schistosomes on polysaccharide synthesis in albumin glands of Biomphalaria glabrata.

An in vitro bioassay was used to examine [14C]glucose incorporation into polysaccharides in albumen glands (AGs) of susceptible M-line Biomphalaria glabrata infected with the NMRI strain of Schistosoma mansoni. Polysaccharide and galactogen synthesis were unaffected by larval trematode infection in AGs of snails at days 14, 21, and 28 post-infection (p.i.) when compared to uninfected controls. Further experiments were conducted to determine if daughter sporocysts, hypothesized to be primary mediators of parasitic castration in this system, were able to exert direct effects on synthetic activity of uninfected AGs via haemolymph-borne molecules or in vitro culture-generated larval excretory-secretory (ES) products. When AGs were incubated in the presence of infected snail haemolymph, significant differences in quantities of polysaccharides and galactogen were detected only in test organs incubated in day 28 p.i. haemolymph. Daughter sporocyst ES products generated during the first 48 h of culture caused a significant reduction in polysaccharide and galactogen synthesis in test organs. When ES products from days 3 to 6 of in vitro culture were tested similarly, no significant differences in either polysaccharide or galactogen synthesis were observed between control and test organs. These data demonstrate that daughter sporocysts are able to modulate a specific aspect of the reproductive activity of the snail host through haemolymph-borne molecules of host or parasite origin, or directly through in vitro culture-generated ES products.