Comparative Analysis of the Effect of Trematode Invasion on the Activity of Proteolytic Enzymes in Some Freshwater Gastropods

The activity of proteolytic enzymes and the effect of trematode infestation on the size and mass parameters and activity of these enzymes is studied in three species of mollusks: Lithoglyphus naticoides (C. Pfieffer, 1828), Viviparus viviparus (Linnaeus, 1758), and Lymnaea stagnalis (Linnaeus, 1758). Pepsin-, trypsin-, and chymotrypsin-like activity is found in all mollusks, indicating a wide range of protease activity in these animals. Differences in the levels of protease activity in shellfish are most likely related to the type of diet. Shellfish infection with trematodes affects the studied parameters in different ways. Thus, in infected Lithoglyphus naticoides, the shell height and mass are greater than in uninfected individuals. In Viviparus viviparus, these parameters do not display significant differences. In Lymnaea stagnalis, the shell height does not differ in uninfected and infected mollusks, and the mass is greater in infected specimens. The activity of a particular group of proteases varies depending on the mollusk species and the parasite development stage. Trematode infection has the greatest effect on protease activity in Lithoglyphus naticoides.