Changes in the cell composition of the hemolymph in the snail Planorbarius corneus after infection with the trematode Plagiorchis sp.

We found two functional populations of hemocytes in the hemolymph of the pulmonate snail Planorbarius corneus: hyalinocytes and granulocytes. The hyalinocytes were much more numerous than granulocytes. Each population was subdivided into subpopulations based on morphological and functional characteristics. The hyalinocyte population was represented by two subpopulations differing in size, granularity, and ability to form pseudopodia. In snails infected with the trematodes Plagiorchis sp., the cellular composition of the hemolymph changes, with hemocytes being mostly represented by granulocytes. This phenomenon is associated with the fact that granulocytes form a hemocytic paletot on the surface of sporocysts of Plagiorchis sp. It is suggested that pulmonate molluscs have one lineage of hemolymph cells. Hematopoietic stem cells can divide, ensuring multiplication of prohemocytes. The latter differentiate into hyalinocytes, which, in turn, differentiate into granulocytes.