December 2021 | Volume 36 | Issue 2 | Page 153 Introduction M etal pollution of freshwater bodies such as streams, rivers, and lakes has been recorded around the Corresponding author’s: Sajid Abdullah and Huma Naz humanaz@cuvas.edu.pk, uaf_sajidabdullah@yahoo.com world due to its harmful efects not only on humans but also on other living species. Heavy metal pollution severely deteriorates the quality of environment by interfering with ecological equilibrium of an aquatic ecosystem (Farombi et al., 2007). In aquatic bodies, fsh are the animal which cannot escaped from harmful impact of these heavy metals and that’s the reason fsh is commonly used as bio-indi- Sajid Abdullah 1 *, Huma Naz 2 *, Zunera Abbas 1 , Uzma Nazir 1 , Mehrunisa Basharat 1 , Tanveer Ahmed 3 , Ad- nan Ahmad Qazi 2 Micronucleus Assay as a Biomarker to Diagnose Lead, Chromium and Cadmium Induced Genotoxicity in Erythrocytes of Carnivorous Fish, Wallago attu 1 Department of Zoology, Wildlife and Fisheries, University of Agriculture Faisalabad, Pakistan. 2 Department of Zoology, Cholistan University of Veterinary and Animal Sciences Bahawalpur, Pakistan. 3 Department of Life Sciences, Khwaja Fareed University of Engineering and Information Technology, Rahim Yar Khan, Pakistan. Abstract | Heavy metals discharged from agriculture and industries into water bodies are a signifcant cause of water contamination. Tis increase in heavy metals cause genetic damage in exposed species like fsh. Terefore, this study focused on the genotoxic efects of lead (Pb), chromium (Cr) and cadmium (Cd) on nuclear abnormalities in peripheral erythrocytes of Wallago attu were assessed by micronucleus assay. Fish were exposed to diferent concentrations (1/3 rd , 1/4 th , 1/5 th and 1/7 th of LC 50 ) of Pb, Cr and Cd, separately, for three weeks. Blood sample of fsh was collected to see the micronuclei (MN) and deshape nuclei (DN) in peripheral erythrocytes of fsh after one-week interval. Fish W. attu showed signifcant induction of MN and DN in blood due to metals (Pb, Cr and Cd) exposure. It was noted that Pb and Cd exposure caused signifcant formation of MN and DN in RBCs of fsh throughout the experimental period. However, Cr treated fsh showed higher formation of MN and DN during initial two weeks of exposure after that both were decreased. Te toxic potential of diferent concentration of Pb, Cr and Cd induced genotoxicity followed order: 1/3 rd >1/4 th >1/5 th >1/7 th of LC 50 . Te metal specifc response of fsh followed the trend: Pb>Cr>Cd. Statistical analysis revealed that diferent concentrations and duration of Pb, Cr and Cd have signifcant efect on the frequency of micro-nucleated erythrocytes. Te inferences of this study will be helpful in monitoring aquatic ecosystems using fsh biomarkers. Novelty Statement | Te study is novel for detecting the genetic damage at cellular level of fsh (Wallago attu) caused by heavy metals and industrial toxicants in water. Article History Received: February 22, 2021 Revised: July 19, 2021 Accepted: August 13, 2021 Published: October 08, 2021 Authors’ Contributions SA supervised the study and guided the author in planning the research work. HN helped in laboratory work. ZA, TA and UN executed the research work. MB helped in statistical analy- sis. AAQ assisted in manuscript writing. Keywords Blood, Nuclear abnormalities, Metal toxicity, Carnivorous fsh To cite this article: Abdullah, S., Naz, H., Abbas, Z., Nazir, U., Basharat, M., Ahmed, T. and Qazi, A.A., 2021. Micronucleus assay as a biomarker to diagnose lead, chromium and cadmium induced genotoxicity in erythrocytes of carnivorous fsh, Wallago attu. Punjab Univ. J. Zool., 36(2): 153-158. https://dx.doi.org/10.17582/ journal.pujz/2021.36.2.153.158 Punjab University Journal of Zoology 36(2): 153-158 (2021) https://dx.doi.org/10.17582/journal.pujz/2021.36.2.153.158 Research Article