Characterization of the Blood Cells of Australian Crocodiles (Crocodylus porosus [SCHNEIDER] AND C. johnstoni [KREFFT])

Circulating blood of eight crocodiles (four Crocodylus porosus [SCHNEIDER], four Crocodylus johnstoni [KREFFT]) was examined by light microscopy, cytochemistry and transmission electron microscopy. The results were correlated and on that basis erythrocytes, thrombocytes, lymphocytes, monocytes and three main types of granulocytes were characterized. Erythrocytes, thrombocytes, lymphocytes and monocytes were similar in appearance to those described for other reptiles. In addition, lymphocytes and monocytes had ultrastructural details similar to those described for the cells in man. The three main granulocytes were designated types I, II and III. Type III had characteristics which were similar to those described for the basophil. Types I and II were eosinophilic on blood films stained with Giemsa. On ultrastructural detail, and by comparison with ultrastructural reports for the granulocytes of the fowl and lizard (Agamia stellio), type I appeared to be similar to the heterophil but type II could not be characterized definitely. However, the crystalline array present in granules of type II has been recorded for eosinophil granules in man.