Abstract
Little work has been done on phagocytosis of fish leucocytes and on the role of phagocytes in the host-parasite relations in fish. The purpose of the work reported in this paper was to classify the leucocytes of goldfish(Carassius auratus) by peroxidase reaction, and to examine which of the leucocytes could phagocytize bacteria.
Inoko & Itoga's method using o-tolidine as a hydrogen donator was applied to blood smears to detect the peroxidase reaction of leucocytes.
Phagocytosis of leucocytes on bacteria was examined in vitro. Heparinized blood was obtained from goldfish by heart puncture. Eighteen hour broth cultures of Staphylococcus aureus and Escherichia coli were used as bacterial cell suspensions. Zero point zero one ml of the bacterial cell suspension was added to 0.09ml of the blood in a small test tube. The mixture was incubated for several hours at 25°C with shaking. After the last incubation, the mixture was spread on slides.The peroxidase staining was applied to these slides. The peroxidase reaction and the structure of the leucocytes phagocytized bacteria were examined.
The peroxidase positive granules in the leucocyte of goldfish stained yellow brown by Inoko & Itoga's method and the nucleus of the peroxidase positive leucocyte could be clearly observed. The positive reaction could be observed on the blood smears preserved for a period of 47 days without fixation. The average number of the peroxidase positive leucocytes per 5, 000 erythrocytes was 17 in the peripheral blood of goldfish. Many peroxidase positive cells were observed on touch preparations from kidney and head kidney.
Three types of leucocytes, peroxidase positive leucocyte, peroxidase negative large leucocyte and peroxidase negative small leucocyte, could phagocytize bacteria. The appearance of peroxidase positive leucocyte phagocytized bacteria was similar to that of granulocyte in mammals.
