Total Haemocyte Counts and Haematopoiesis in Saduria Entomon (Linnaeus, 1758) (Isopoda, Valvifera) From the Baltic Sea Infected With the Yeast Cryptococcus La Urentii (Kufferath) Skinner*)

Studies were made of the haemolymph and haematopoiesis of 22 specimens of Saduria entomon, naturally infected with the yeast Cryptococcus laurentii. In 18 of these haemocytes were also counted. Their total haemocyte count was 693, which is 3 times the figure in healthy S. entomon. Their haemolymph contained granulocytes, hyaline cells, and C. laurentii cells. Granulocytes contained phagocytosed C. laurentii cells, while hyaline cells did not contain phagocytosed yeast. Haematopoiesis was clearly taking place in the gut wall of the S. entomon specimens under study. In the 4 remaining individuals the haemolymph was filled with C. laurentii cells among which only single hyaline cells with phagocytosed yeast cells were observed. In their gut wall only yeast cells accumulated. The results obtained support our earlier findings that in S. entomon granulocytes are the primary phagocytotic haemocytes, and that hyaline cells can be taken to be prohaemocytes capable of proliferation under specific conditions.