Impact of Azolla on the histopathology of the liver and intestine of the fingerling carp Cyprinus carpio

Abstract

This study aims to evaluate the histopathological effects of Cyprinus carpio treated with Azolla growing on the pond with sheep manure fertilizer. Heavy metals contamination in aquatic ecosystems is known to be recognized by aquatic macrophytes. This study aims to estimate the accumulative of lead(Pb) and Zinc (Zn) in Azolla and to detect if these heavy metals cause damage to fish tissues. Azolla cultured in ponds fertilized with sheep manure for eight days, the Pb and Zn were estimated in the sheep manure which were (28.5 and 139.3) mg /kg respectively the percentage of these heavy metals in the macrophytes was 50% for Pb and 19% for Zn. Cyprinus carpio were divided into five groups depending on the rate of Azolla concentrated with Pb and Zn added to fish feed as the T1 (0%), T2(4.5%), T3(9%), T4(13.5%) and T5(18%). Histopathological changes and lesions vary in severity according to the level of Azolla in microscopic examination of the intestine and liver from these groups, which range in the abnormal most villi shape, with adherence to condensed heavy metals, goblet cells and juncture hyperplasia, its necrosis, and villi damage. Also, liver lesions are characterized by vacuolar degeneration and proliferation of sinusoids in fish of T2; The lesions are more severe in other groups, including isolated infiltration of inflammatory cells, vasculitis, vasogenic oedema with thrombus formation, the concentration of the bile duct, atrophy of the pancreas with the necrotic portal area. In the conclusion of this study that Azolla macrophytes are good bioaccumulation of Pb and Zn that can be transmitted into fish and cause histopathological changes and tissue damage, other studies should be conducted to determine the correlation between concentrated heavy metals in Azolla plants and histopathological and physiological changes in fish.