Morphology and phagocytic ability of hemocytes from Cristaria plicata

Abstract

Cristaria plicata is one of the most important freshwater mussels for pearl production in China, whose hemocytes were characterized using light, phase contrast and electron microscopy. In accordance with the presence or the absence of granules in the cytoplasm, two main types of hemocytes were recognized, granulocytes and agranulocytes. The granulocytes possessed cytoplasmic granules, while agranulocytes had none or a few cytoplasmic granules. In addition, in line with the diameter of granulocytes and cytoplasmic granules, granulocytes were further divided into large and small granulocytes. According to the diameter of agranulocytes and the different N/C ratios, agranulocytes could also be divided into hyalinocytes and lymphoid hemocytes. The mean concentration of the hemocytes of C. plicata was about (2.37 ± 0.51) × 10 6 cell mL −1. The two main cell types were small granulocytes (56.60% ± 1.41) and hyalinocytes (36.80% ± 2.11), while large granulocytes (4.20% ± 0.23) and lymphoid hemocytes (2.40% ± 0.12) were of the minority. With the rise of water temperature, total hemocyte counts showed a significant increase. The hemocytes presented different tinctorial properties for Wright's staining in smears. Small granulocytes and hyalinocytes exhibited acidophils and basophils, while large granulocytes and lymphoid hemocytes showed only acidophils and basophils respectively. Three types of hemocytes, large granulocytes, small granulocytes and hyalinocytes, could phagocytize yeast and Bacillus subtilis cells. Small granulocytes appeared to be more efficient in phagocytosis than large granulocytes and hyalinocytes, and large granulocytes showed to be more efficient than hyalinocytes. Water temperature had a great effect on the phagocytic ability of hemocytes.