THE STRUCTURE OF RED BLOOD CELLS, WHITE BLOOD CELLS AND THROMBOCYTES IN FRESHWATER CROCODILES (CROCODYLUS SIAMENSIS)

Abstract

Blood cells and thrombocytes from five crocodiles, three males and two females, were studied by both light and transmission electron microscopes (TEM). The blood cells could be categorized into red blood cells, white blood cells and thrombocytes. The nucleated red blood cells were oval in shape and the TEM study revealed vacuoles in the cytoplasm. The white blood cells fell into two groups; one with granules and the other without granules. The granulocytes were heterophils, eosinophils and basophils. The heterophils had an eccentrically oval nucleus and a large number of acidophilic rod-shaped granules in the cytoplasm. Eosinophils also posessed an eccentrically oval nucleus but their numerous acidophilic granules were round. The electron microscopic study showed lysosomes in the cytoplasm. Basophils could be easily differentiated from the others. The basophil had a
centrally round nucleus and basophilic round granules. The electron microscopic study revealed round granules and mitochondria in the cytoplasm. The agranulocytes (lymphocytes and monocytes) had a round nucleus and little cytoplasm. Under the electron microscope, lymphocytes contained azurophilic granules whereas the monocyte
cytoplasm showed vacuoles, lysosomes and mitochondria. Azurophils are a type of monocyte found in crocodiles and have many azurophilic granules. Thrombocytes were found either separate from each other or aggregated together. The TEM study revealed round nuclei and a homogenous cytoplasm without any apparent organelles.