The influence of trematode infection on the hemocyte composition in Planorbarius corneus (Gastropoda, Pulmonata)

Hemocytes are the main effector elements of gastropod anti-trematode defence reactions. Elucidation of morphological and functional characteristics of hemocytes allows for better understanding of gastropod resistance mechanisms. Hemocyte composition of Planorbarius corneus revealed types of cells: granulocytes and hyalinocytes, which differ in granularity, nucleus-tocytoplasm ratio and spreading compatibility. Flow-cytometric analysis suggested the presence of these cell types in the hemolymph of P. corneus and showed the differences in granulocyte/hyalinocytes ratio in non-infected snails and snails infected with different trematodes - Cotylurus sp., Notocotylus sp., Plagiorchis sp. and Echinostoma sp. It was also shown that in snails with large shell diameter (34 - 37 mm), the ratio of cell types in the hemolymph is clearly biased in favour of granulocytes