Contents lists available at ScienceDirect Ecotoxicology and Environmental Safety journal homepage: www.elsevier.com/locate/ecoenv Insights into the heavy metal-induced immunotoxic and genotoxic alterations as health indicators of Clarias gariepinus inhabiting a rivulet Umarah Zahoor Banday 1 , Sadiya Binte Swaleh 1 , Nazura Usmani ⁎ Aquatic Toxicology Laboratory, Department of Zoology, Aligarh Muslim University, Aligarh, 202002, India ARTICLEINFO Keywords: Heavy metals Serum enzymes Hematology Cortisol Histopathology MT ABSTRACT There is a dire need to assess the quality of fishes transported for human consumption as lately, their health is challengedbecauseofanthropogenicactivities.Heavymetalswithalongenvironmentalpersistencearetoxicto fishes and the humans. The study was conducted to evaluate the impact of heavy metals on Clarias gariepinus inhabiting popular Ganges rivulet at Narora (28.18° E, 78.39° N). The limnological values deviated from the international Standards (USEPA, WHO). Higher total dissolved solids (859mg/L), total suspended solids (406mg/L), low dissolved oxygen (5.60mg/L), and pH (5.21) indicated the presence of contaminants. Heavy metals estimated followed the order Cd > Ni > Cu > Cr. Serum enzymes (hepatic and renal markers) viz., aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) were higher than the normal, whereas, creatine kinase (CK) was considerably low in both male and female fish. Stress induced was marked by elevation in cortisol and glucose. This had its impact on hematological parameters as well, as a decline in Total leucocyte count (TLC) & mean corpuscular volume (MCV) and increase in Mean cell hemoglobin (MCH) was observed. Erythrocytes also showed altered morphology. Marked histopathological al- terations were observed in all immune organs (head-kidney, liver, spleen, thymus). Oxidative stress induced by heavy metals leads to the production of metal scavenging protein metallothionein (MT) and glutathione per- oxidase (GPX). Maximum fold change in metallothionein (MT) gene expression was observed in the liver, fol- lowedbyspleen,thymus,blood,andhead-kidney.Glutathioneperoxidase(GPX)geneexpressionwashighestin theliver,followedbythymus,spleen,blood,andhead-kidney.Thegeneexpressionstudiesfurthervalidatedthe increased level of heavy metals as potent contaminants of water and the non-condusive abiotic factors. 1. Introduction Natural water bodies require maintenance for the sustenance of floraandfauna.Evenslightalterationsinphysicochemicalpropertiesof water can have its impact on the health of aquatic organisms. Contaminations of these resources, particularly by non-biodegradable heavy metals, pose a threat to aquatic species, especially the fishes, which are sensitive to small alterations in their surroundings. These heavy metals affect the physicochemical properties of the water, making it unsuitable for the survival of aquatic life. In this regard, the current study was undertaken to pertain to a rivulet of river Ganges flowing through Narora, Uttar Pradesh (28.18° E, 78.39° N), India. The riverhasahugeeconomicvalueintermsoffoodprevailingintheform of freshwater fishes. The concern is related to contaminant loaded ef- fluents released into the rivulet from the power plant located in the vicinity, which primarily contains heavy metals, hence posing a severe threattotheaquaticorganisms.Thusitbecomesimportanttoelucidate water quality of rivulet, presence of heavy metals, and eventually the toxic effects on fish. Bioaccumulation and biomagnification of heavy metals occur at various levels of the food chain that culminates at hu- mans,influencingtheirhealth.Theseelementscanbindwithbiological matter containing nitrogen, sulfur, and oxygen affecting structures and functioning of proteins, enzymes, hormones, and other biomolecules. Stress induced impairs an organism's energy levels, thus mobilizing proteins and lipids to meet its energy demands. Alteration in serum biochemistry can lead to diseases and mortality. Induced studies have reported altered activity of enzymes (catalase, superoxide dismutase, peroxidase, cytochrome c oxidases, ferroxidases, monoamine oxidase, and dopamine β-monooxygenase) in tissues of sensitive species as a result of heavy metal accumulation (Stern B. R. 2010; ATSDR. 2002). Mehjabeen Javed et al. (2017) evaluated oxidative stress and bio- chemical alterations in gill, liver, and kidney of Channa punctatus https://doi.org/10.1016/j.ecoenv.2019.109584 Received 16 July 2019; Accepted 17 August 2019 ⁎ Corresponding author., E-mail addresses: umarah18@gmail.com (U.Z. Banday), sadiyabinteswaleh@gmail.com (S.B. Swaleh), nazurausmani@gmail.com (N. Usmani). 1 both the authors have equally contributed to the study. Ecotoxicology and Environmental Safety 183 (2019) 109584 0147-6513/ © 2019 Elsevier Inc. All rights reserved. T