MICROSTRUCTURE AND ULTRASTRUCTURE OF THE PERIPHERAL BLOOD CELLS OF EUROPEAN EEL(ANGUILLA ANGUILLA)

We studied the peripheral blood cells of one\|year\|old European eel( Anguilla anguilla )using light microscopy and transmission electron microscopy.For morphology,peroxidase Giemsa was used.The morphological study revealed that the peripheral blood has the following cell types: erythrocyte, neutrophil, lymphocyte and thrombocyte. Erythrocytes are 11 82±0 75 μm in length and 7 84±0 83 μm in width,oval shape and contain oval nuclei and dark gray cytoplasm.They were almost completely devoid of organelle,except for a few vesicles and small mitochondria.Neutrophils were 11 73±1 45 μm in length and 10 73±1 14 μm in width,round or oval,containing round,bilobed or trilobed nuclei and whitish cytoplasm.There were three special granules in neutrophils. Special granules A were round or oval shape,possess thread\|like,cotton\|like or crystalline structrures,special granules B were long oval or rod\|like,dark stained and possess cotton\|like structures,which paralleled to the long axia.Special granules C were round or oval,possessed light gray structures.The ultrastructural study revealed that the neutrophils include three types of cells according to their special granules(A,B and C special granules):type Ⅰ(included A,B and C special granules)、type Ⅱ(included A and C special granules)and type Ⅲ(included C special granules).A greater amount of mitochondria,small tubules which resemble smooth endoplasmic reticulum,and numerous oval on elongated granules which contain a striated or crystalline structure,were observed in neutrophils although neutrophils are similar to monocytes in size and shape.Monocytes were of 10 78±1 55 μm in length and 9 74±1 75 μm in width, containing round or oval nuclei.A greater amount of vesicles and a few mitochondria were observed.Thrombocytes of 1 97±0 71 μm in length and 4 02±0 74 μm in width,were round,oval,spindle or tadpole\|like shape.Deep indentations of the plasmalemma,which gave appearance of vacuoles,were often seen.Lymphocytes were clearly different from thrombocytes by the presence of large number of free ribosomes.Neither eosinophils nor basophils were found directly in peripheral blood.The nuclear division of erythrocyte and monocyte were observed in peripheral blood indicating that erythroblasts and young monocytes could enter the peripheral blood.The size of thrombocyte was the smallest while that of the neutrophil was the largest and the number of neutrophils was the least while that of lymphocytes was the most in the blood cells.