Ultrastructural Study of Haemocytes of the Freshwater Snail Planorbarius corneus (L.) (Gastropoda, Pulmonata)

Ultrastructural studies were performed on the blood cells of Planorbarius corneus. Spreading and round cell forms were observed. The spreading form can be distinguished from the round form by its abundant cytoplasm, pseudopods and irregularly shaped nucleus. Electron dense granules in the mitochondrial matrix are found in the round form and are lacking in the spreading form. Moreover, cellular apoptosis is observed in the round form. The ultrastructural findings and the previously described characteristics support the idea that the two cell forms belong to two basic cell types.