Schistosoma mansoni: Changes in the albumen gland of Biomphalaria glabrata snails selected for nonsusceptibility to the parasite

The LAC-line strain of the snail Biomphalaria glabrata has very low susceptibility to the parasite Schistosoma mansoni and a very low reproductive potential. Upon examination of the reproductive tract of these snails, light and electron microscopy revealed obvious abnormalities in the albumen gland. Secretory cells that are normally cuboidal in susceptible NMRI (F-0) snails were squamous in LAC-line snails. These LAC-line cells contained small secretory granules and negligible rough endoplasmic reticulum and Golgi, compared to large granules and an extensive array of both organelles in F-0 albumen gland cells. Comparative analyses of soluble protein extracts of F-0 and LAC-line albumen glands showed several qualitative differences. Among the most prominent was an 18-kDa protein in F-0 snails that was remarkably reduced in the soluble protein extracts of LAC-line snails. Also, metabolic incorporation of [S-35]-methionine was impaired in LAC-line albumen glands. Whether these albumen gland changes are caused by decreased susceptibility to parasitism is yet to determined.