Morphology and Histological Observation on Urinary System ofAcrossocheilus yunnanensis

Urinary system of the Acrossocheilus yunnanensiswas observed in detail by anatony and paraffin section technique. The results showed that there are two head kidney of A. yunnanensis. Composed of lymphoid tissue, the headkidney is a massive solid tissue. The mesonephros includes renal corpuscle and renal tubules. Aggregation of renal corpuscles was observed in renal corpuscles and it mostly occurred in the middle of mesonephros, which indicated that thenephron of A.yunnanensisbelongs to that of a typical nephron of freshwater teleosts. The renal tubules are composed of 5 segments:the neck segment, primary and second proximal segment, distal segment and the collecting tube. The epithelia of the primary and second proximal segment are simple columner epithelium, and there are abundant brush borders at the free surface of epithelia cells, however these brush borders are absent in the distal segment and collecting tube had no brush borders. The urinary bladder belongs to the tubal bladder type, and there are secretory cells in the transitional epithelium of the bladder mucous membrane.