Journal of Natural Sciences Research www.iiste.org ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online) Vol.4, No.18, 2014 55 Changes in the Leucocyte and Serum Biochemistry in Clarias gariepinus (Burchel) Exposed to Sublethal Lead Choride * Oluah, Ndubuisi Stanley, Ulasi, A.M Omerebele and Nwani, Christopher Didigwu Ecotoxicology Research Laboratory, Fisheries & Hydrobiology Reseaech Unit, Department of Zoology & Environmental Biology, University of Nigeria, Nsukka email = ndubuisi.oluah@unn.edu.ng; ndubuisioluah@yahoo.com * To whom all correspondences should be addressed. Abstract Clarias gariepinus fingerlings were chronically exposed to sublethal concentrations of lead ( 0.00; 0.10 and 0.40 mg/L) as lead chloride for twenty eight days in the laboratory. The changes in the leucocytes and serum biochemical parameters (glucose, protein and total cholesterol) of the fish were determined every seven days for 28 days in a renewable static bioassay system. At the end of the study, these parameters were significantly (p < 0.05) elevated in the treatment groups when compared with the control. There was pronounced leucocytosis in the lead-exposed fish when compared with the control. The lymphocytes and the basophils were the most dominant agranulocyte and granulocytes, respectively. The magnitude of increase was influenced by both duration of exposure and concentration. The fish exposed to lead were significantly (p<0.05) hyperglycaemic and hypercholesteremic. The serum protein concentration was also significantly (p< 0.05) increased in the treatment groups when compared with the control. These changes are indications of stress imposed on the fish by lead and could be used as indices of lead poisoning. Keywords: Clarias, lead, hyperglycaemia, cholesterol, protein, leucocyte 1 INTRODUCTION In recent years heavy metal contamination of the aquatic ecosystem has become a source of concern to not only environmentalists but also to health workers and biologist alike due the public health implications of the increased environmental load of these metals. This problem seemed to be exacerbated by the uncontrolled anthropogenic discharges of heavy metals as industrial wastes, sewage, pesticides and through mining activities. Lead is one of the most widely used heavy metal that has wide applications in such products as storage batteries (lead accumulator), electric cable sheaths, alloys, pesticides, paints, petrol and rubber products among other uses (Jackson et al, 2005). Naturally, lead occurs in water bodies in trace amounts but due increasing commercial activities, it is increasingly being mobilized into the aquatic environment that the concentration could reach toxic level (Van Vuren, 1999). Lead reaches water bodies either as industrial effluents, runoff from agricultural fields or as ores from mines. In water bodies, lead forms complexes with sediments or organic materials (TNO, 2001) and in the process enters the food chain. The problem posed by lead in the aquatic system is complex due to its non-degradability and interactions with other materials to form complexes that may potentiate their toxic effects. In mammals lead exposure promotes increased liver weight, pycnosis of kupfer cells and inhibited hepatic enzymes (ATSDR, 1999). Once absorbed into the body, the lead affects the fish in a variety of ways. It affects the blood (Allen, 1993; Nussey et al, 1995), the structural integrity of vital organs of the fish (Karan et al, 1998) and the enzyme systems (Oluah, 1999). Heavy metal contamination also predisposes animals to chromosomal and DNA damage (Palmer and Puls, 1994; Bolognesi et al, 1999) as well as neurological, renal and biochemical disorders in fish (Goyer, 1993). In fish, lead induces poor growth performance and reduced nitrogen conversion ratio (Hayat et al, 2007; Naz et al, 2008). In Nigeria, due to increasing industrialization, pesticide application and other commercial activities, the level of lead ion in Nigerian waters has increased in recent years above WHO permissible levels of 0.2mg/L (WHO, 1996). In Aba River, Mgbemena et al (2011) reported that the lead level ranged from 60.025 -70.16 mg/kg sediment while in Anam River at Otuocha, the concentration ranged from 0.59-7.34 ppm (Igwilo et al., 2006). In Ethiope River, the lead concentration ranges between 0.27-0.72 mg/L (Osakwe and Peretiemo-Clarke, 2013). The level of lead in Kubanni and Delimi Rivers in Northern Nigeria are 6.54 and 0.51-0.95 mg/L, respectively (Uzairu et al., 2008; Sabo et al., 2013). Within the last few years, newspapers in Nigeria reported that more than four thousand eight hundred persons died of lead poisoning in Zamfara State. The food habit and ecology of Clarias species as omnivorous and opportunistic feeders predispose it to lead poisoning as it feeds on both food of animal origin and detritus. Thus, Clarias is a good sentinel organism for ecotoxicological study of lead contamination in water bodies. The purpose of the study was therefore to investigate the effect of sublethal lead on the leucocyte and some biochemical parameters in Clarias gariepinus with a view to using them as biomarkers of lead toxicity.