Genotoxicity and limbs asymmetry in the Egyptian toad (Sclerophrys regularis) as biomarkers for heavy metals toxicity

   Many species of amphibians are facing remarkable decline and extinction throughout the world. Chemical contamination, such as heavy metals, is one of the factors contributing to the extinction of amphibians. Wetland biota, particularly amphibians, may be harmed by heavy metal contamination. The emergence of micronucleated erythrocytes (MN) and nuclear lesions (NL), collectively known as MN-Test, in nucleated erythrocytes is an excellent tool for detecting genotoxicity or chromosomal damage. Furthermore, developmental instability, also known as fluctuating asymmetry (FA), is broadly applied to assess changes in the health of the environment under natural conditions when it is subjected to long-range pollution. Some heavy metals (MN, Fe, Pb, Cd, and Cr) were measured in water – soil from two separate environments of  Egyptian toad “Sclerophrys regularis” (EL Giza and El Wahat regions, Egypt). MN and FA traits were also assessed to compare and evaluate the impact of heavy metals pollution. The current results have revealed that EL Giza is more polluted than EL Wahat, and toads inhabiting EL Giza showed higher micronucleated MN and NL of RBCs than that from EL Wahat. Two patterns of fluctuating asymmetry;  the right hindlimb was larger than the left limb and the right forelimb was larger than the left forelimb, were recorded from EL Giza. On the other hand, opposite results were obtained for toads processed from El Wahat. Statistical analysis indicated the presence of strong relation between heavy metals distribution in the environment and the investigated biomarkers (0.05≥ P≤ 0.01).