Observation of hematocytes in peripheral blood and the hematopoiesis in Sinibrama taeniatus

Sinibrama taeniatus is a small economic fish endemic to the upper reaches of the Yangtze River. In order to figure out the component types of hematocytes and the hematopoiesis process, and thus to further provide valuable information on the fundamental construction of the immune system of S. taeniatus, smears of peripheral blood and imprints including pronephros, body kidney, liver and spleen were stained with Wright-Giemsa staining. After that, the morphological characteristics and distribution of hematocytes in peripheral blood and hematopoietic organs were observed, and the sizes and proportion of different types of hematocytes in the detected four organ prints were statistically analyzed as well. The results showed that the hematocytes of S. taeniatus was mainly comprised of erythrocytes and leukocytes. Leukocytes can be divided into several types including lymphocytes, granulocytes, monocytes, thrombocytes and so on. In the peripheral blood smears, as the main group, lymphocytes accounted for the largest proportion of total leukocytes (65.79%±0.10%), followed by thrombocytes and neutrophils, accounting for 16.76%±0.07% and 13.92%±0.09% respectively. The number of monocytes was the least, only 3.33%±0.01%. The hematopoiesis of S. taeniatus was mainly divided into four lineages: erythroid, lymphoid, monocytoid and granuloid, and each lineage can be further divided into three stages called primitive, immature and mature ones. The second stages of all three kinds varied depending on types. Immature erythrocytes can just be divided into early and late periods, while that of granulocytes consisted early, middle and late periods. Among these four hematopoietic organs, the pronephros and body kidney were the central place, while the spleen maintained the ability of hematopoiesis of various blood cells, and the liver can only host the development of lymphocytes. Blood cells in the immature stage can migrate to peripheral organs to develop and further mature. These results of the present study provided a basis for further research on the immune system of this endemic fish. It may function as a reference for the study of blood cell development and immune system of fish represented by S. taeniatus.