Structural and cytochemical study of the hemocytes in normal and trematode-infected Lymnaea truncatula

The ultrastructural study of adult Lymnaea truncatula hemocytes reveals a preponderance of spreading cells at different stages of differentiation. A few round cells may represent a distinct population of hemocytes. As in L. stagnalis, spreading cells are remarkable in that they synthesize peroxidase that is stored in secretory granules, but in L. truncatula hemocytes, endogenous peroxidase activity is also localized in multivesicular bodies. The ultrastructure and peroxidase content of hemocytes do not seem to be affected in snails with established parasites. Evidence that parasites interfere with normal hemocyte functions is that in the few capsules that occurred in parasitized snails the hemocytes did not spread normally and their peroxidase granules were resorbed into multivesicular bodies.