Abstract: Objective To observing and analyze the microstructures and ultrastructures of the liver in zebrafish. Methods The tissue samples were observed by using light and electron microscopy.Results There was no typical portal area within the parenchyma, bile ducts and venules were randomly distributed within the parenchyma. The polygonal hcpatocytes are arranged in twisting, branching and anastomosing cords usually two cells thick .There was a single big and spherical nucleus in the hepatocyte,and the nucleoli displayed a separation into granulose component, fibrillar centers and dense fibrillar component. The cytoplasm are dominated by numerous stacks of non-fenestrated lamellae of rough endoplasmic reticulum (RER) of considerable length arranged in close parallel array and smooth endo-plasmic reticulum was rarely observed. The number of mitochondria is of considerable, and myelinbody was found in mitochondria. When the cytoplasm was rich in mitochondria, RER, and ribosome and the number of nucleopore was massive, glycogen was found in small concentrations, and a few lysosome may be observed. When glycogen was found in large concentrations, the number of nucleopore was few, so the cytoplasmic organoids were. These suggested that the consumption of glycogen ensured normal metabolism of nucleic acids and proteins, and mitochondria provided energy in the process of protein synthesis. The biliary system is arranged in arborization. Bile canaliculus includeded intracellular and intercellular bile canaliculus，the intracellular bile canaliculus had lots of long microvilli, the intercel-lular bile canaliculus had relatively shorter ones. Erythrocytes, lymphocytes，fat-storing cells and endot-helial cells were also described. A comparison between zebrafish liver and that of other teleosts was made. Conclusions The way of hepatocytes arranged in zebrafish was different from other teleostei and was not exactly conformable to previous accounts, this distinction was relevant to the animal species and research methods. The ultrastructure of hepatocytes proved its active synthesis and metabolic function.

Key words: Liver, Micro structure, Ultrastructure, Zebrafish