Studies on resistance in snails. 4. Induction of ventricular capsules and changes in the amebocyte-producing organ during sensitization of Biomphalaria glabrata snails.

Formation of an amebocyte aggregate in the ventricular cavity of Biomphalaria glabrata can be induced 30 hr or more after a single infection by irradiated or (less frequently) by normal Echinostoma lindoense miracidia. The resulting amebocyte mass frequently encapsulated and destroyed the developing E. lindoense sporocysts within the ventricle. The constituent amebocytes of the capsule correspond in vitro and by staining characteristics to circulating amebocytes of uninfected snails, but with additional inclusion bodies, increased mucopolysaccharide, acid phosphatases, and lipid-positive staining reactions. Mitotic activity, rapid growth, and later regression of the amebocyte-producing organ (located between the posterior mantle epithelium and anterior pericardial endothelium) follow the growth and regression sequence of the ventricular capsule. Though peripheral foci of secondary amebocyte production have been found and were previously known, the amebocyte-producing organ appears to be the primary amebocyte source responsible for the snails' rapid intraventricular sporocyst encapsulation.