Determination of heavy metal genotoxicity and their accumulation pattern in different fish organs of selected fish species collected from the Asa River, Ilorin, Kwara State, Nigeria

Abstract

This study investigated bioaccumulation of heavy metals and cytogenotoxic effects that could result from exposure of fish to heavy metals in the Asa River, Ilorin, Nigeria. The three different fish species, Tilapia zilli, Oreochromis niloticus and Sarotherodon galilaeus were obtained from the Asa River and the fourth species, Clarias gariepinus was cultured in the laboratory to serve as control. The fish organs; bone, gills, kidney and liver from the four fish species were carefully dissected for the determination of some heavy metals. The results showed that the metal concentration levels were in the order Pb> Cr > Zn > Cd. The highest lead concentration value was observed in the gills of Tilapia fish. The lowest level of Cd was observed in the bone tissue of Oreochromis niloticus. The values of heavy metals found in the cultured fish species were very low in concentration compared to the ones sourced from Asa River. Micronuclei and frequencies of nuclear abnormalities were assessed in the blood erythrocytes of both laboratory cultured fish and the ones obtained from Asa River. Significant differences (P<0.05) were observed for mean frequencies of micronucleus induction in the blood erythrocytes of Oreochromis niloticus, Sarotherodon galilaeus. As for other nuclear abnormalities, significant differences (P<0.05) were observed for mean frequencies in the blood erythrocytes, gills and liver of Tilapia zilli and Oreochromis niloticus. Genotoxicity results in this study showed that the Asa river water contains genotoxic metals say be responsible for the micronucleus and nuclear abnormalities observed in the aquatic environment.

Keywords: Genotoxicity, bioaccumulation, organs, cultured, metals, fish organs