Comparisonal study on histological structure of kidney in dominant fish species from northwestern regions of the Persian Gulf

In this research, histological structures of different parts of kidney (trunk and head kidney) were described in 21fish species from northwest regions of the Persian Gulf. Fishes were anesthetized and then their kidneys with some adjacent vertebral column were collected and fixed in Buin’s solution for histological purposes. Samples were processed according to routin paraffin method sectioned (5 micrometers) and stained (Hematoxylin and Eosin). According to the results, kidneys have two distinct structures including hematopoitic and excretory tissues. Head kidney has more hematopoitic role with nephrons among them. Different types of blood cell such as red blood cell, lymphocytes, monocytes and granolocytes as well as plasmacells, reticular cells and macrophages were observed in head kidney. There were melanomacrophage bodies among hematopoitic tissues in some species. Excretory parts in studied species were included of glomerules and nephric tubules. Neck section, proximal tubule (I and II), distal tubule and collecting tubule were present in nephric tubules. In chondroichthyes such as Grey Bamboo Shark )Chiloscyllium griseum( and stingary )Himantura walga (nephrones have bigger parts in comparison with osteichthyes due to evolutionary aspects