Comparative investigation of kidney tubules of Kutum, Rutilus frisii kutum in brackish water (Caspian Sea) and fresh water (Khoshkrood River)

Structure، size and number of tubules were investigated in kidney of Kutum، Rutilus frisii kutum captured from brackish water (Caspian Sea) and fresh water (Khoshkrood River). 10 mature Kutum were collected from Anzali coast with 8. 49 ppt salinity and 12. 4°C temperature. The same number of specimens ware also collected from freshwater with 0. 18 ppt salinity and 18°C temperature. Anterior، middle and posterior parts of the kidney from each sample were dissected for histological examination. Glomerular distal، proximal and collecting tubules of kidney were compared in two aquatic habitats. There were no differences in number of kidney tubules. The mean size of glomerular and collecting tubules were significantly larger in fresh water samples than sea water saples (P<0. 05). The mean Size of proximal tubules was marginally larger in seawater compared to freshwater، although such difference was not significant.