151 Health status of Chrysichthys nigrodigitatus in response to aquatic pollution in Epe, Lagos and Ologe Lagoons, Southwest Nigeria Kingsley Chukwuemeka Kanu 1 *, Emmanuel Taiwo Idowu 2 1 Department of Environmental Management and Toxicology, Michael Okpara University of Agriculture, PMB 7267 Umudike, Nigeria 2 Department of Zoology, University of Lagos PMB 56, Akoka, Nigeria *Corresponding author, E-mail: kanukc@gmail.com Abstract Te aquatic ecosystem is frequently the fnal recipient of pollutants, which may be hazardous to aquatic organism. In this study, in 2012 the following factors were examined: level of Pb, Ni, Cd and Zn in water, sediments, and liver, tissue and gills of Chrysichthys nigrodigitatus from Epe, Lagos and Ologe Lagoon. Superoxide dismutase, catalase, gluthathione peroxidase activity, gluthathione and thiobarbituric acid-reacting substance concentrations in fsh samples were also determined, and liver histopathology was conducted. A condition factor for fsh was also determined. Te results revealed higher levels of Zn in water samples from Lagos lagoon compared to Epe lagoon. Ni and Cd in tissue of samples from Lagos and Ologe Lagoon respectively and Pb in samples from both lagoons were higher than the FAO 1983 limit. Glutathione concentration was higher at Lagos lagoon (0.84 ± 0.55 µmol mL –1 ) compared to Ologe (0.72 ± 0.62 µmol mL –1 ). Vacuolar degeneration and bile stains were observed in liver of fsh samples from Lagos and Ologe lagoon, respectively. Te study showed that C. nigrodigitatus is adversely afected by pollutants in the lagoons. Key words: antioxidants, biomarkers, Chrysichthys nigrodigitatus, condition factor, heavy metals, histopathology, oxidative stress. Abbreviations: BAF, bio accumulation factor ; BSAF, biota-sediment accumulation factor; CAT, catalase; CF, condition factor; DO, dissolved oxygen; GPOx, gluthathione peroxidase; GSH, glutathione; SOD, superoxide dismutase; TBARS, thiobarbituric acid-reacting substances; TDS, total dissolved solids. Introduction All over the world, aquatic pollution is a major concern. Over 400 million tons of chemical products are discharged from domestic, agricultural and industrial activities into aquatic ecosystems (Schwarzenbach et al. 2006). Trace metals such as As, Hg, Se, Cd, Ni, Pb, Cr, Mo, Sb, Zn, Cu, Mn and Ni are discharged into the aquatic environment from coal- burning power plants, iron and steel plants, non-ferrous metals smelters, domestic efuents and sewage sludge disposal (Nriagu et al. 1988). In the aquatic environment, trace metals are not degraded and due to their afnity for biomolecules such as lipids and amino acids, they accumulate in cells of phytoplankton and zooplankton. In this way, high concentrations of the metals in organisms can be found on tops of food chain. Considering that the aquatic environment is the fnal sink of trace metals and chemical products, the essential ecological services provided by fsh i.e. nutrient cycling, regulation of trophic structure, aquatic food web dynamics, and carbon fux (Holmlund, Hammer 1999) may be afected. Fish health can be adversely afected by temperature changes, habitat deterioration and aquatic pollution (Skouras et al. 2003). Fish species have attracted consi- derable interest in studies assessing the biological efects of environmental contaminants (Powers 1989). Te ability of fshes to accumulate pollutants in their cells, tissues or body fuids and respond to these pollutants, some times in a specifc way, makes them valuable biomonitoring tools for water quality assessment. Fishes may also accumulate trace metals to a level that may pose health risk to the fsh and humans via dietary intake. Biomarkers have ofen been employed to assess the health status of organisms and can serve as early-warning indicators of the efects of environmental pollution (Payne et al. 1987). Biomarkers are measureable biological responses that may indicate exposure to and/or efects from anthropogenic substances at sub-lethal concentrations. A number of biochemical, physiological, enzyme and immune assays are considered suitable markers of exposure to and efects of aquatic contamination (Zelikof et al. 2000; Skouras et al. 2003; Farombi et al. 2007; Olarinmonye et al. 2009; Obiakor et al. 2010). Te lagoons in Lagos State Nigeria are the fnal sink of efuents from over 2000 medium and large-scale industries. Also, the Ogun River discharges its municipal waste water into the lagoons (Uaboi-Egbenni et al. 2010). Tere has been a decline in artisanal fshery in Lagos and Environmental and Experimental Biology ISSN 2255-9582 Environmental and Experimental Biology (2017) 15: 151–159 Original Paper DOI: 10.22364/eeb.15.14