Study of the proliferative activity of hemolymph cells in pulmonate molluscs

Hemocytes, the cell of the hemolymph, play a key role in the immune response of pulmonate molluscs to various pathogens including trematode infection. The number of hemocytes is known to increase after immunization but the mechanism of their multiplication remains debatable, proliferative capacity being the stumbling block. Some scientists consider that hemocytes may proliferate, while others think that their multiplication is only possible in special hematopoietic centres. In this work we studied the proliferative activity of hemocytes in five species of pulmonate molluscs: Biomphalaria glabrata, Planorbarius corneus, Planorbis planorbis, Lymnaea stagnalis and Succinea putris. ImageStream technique was used for the study of the hemocyte populations of these molluscan species for the first time. The hemocytes of all the studied species were represented by two main types, granular cells and hyalinocytes. Microscopic and flow-cytometric study of the hemocytes with the use of EdU revealed some EdU-positive cells. However, the analysis of the cell cycle of the hemocytes showed that the amount of DNA in these cells was not increased. Thus, it remains unclear whether the cells of the hemolymph retain the capacity to multiplication.