EFFECTS OF SUB-LETHAL CONCENTRATIONS OF ATRAZINE ON HAEMATOLOGY, OXIDATIVE STRESS AND HISTOPATHOLOGY OF CLARIAS GARIEPINUS JUVENILES IN ABIA STATE, NIGERIA.

The aquatic ecosystem is a sink for pesticides Atrazini is a widely herbicide and may be toxic to fish due to it’ s solubility in water. The study aimed to evaluate the acute and sub-lethal effects of atrazine on the haematology, hythopathology and oxidative stress on jureniles of clarias ganiepirus. The results obtained showed that the 24, 48, 72, and 96yrs LC5o of atrazine was 21. 23, 19.57, 18.37 and 18.37 mg/l respectively. Physical behavioral effects observed include: done pigmentation haemorrhuging from gills, mucous secretion and respiratory ditress.. the total white blood cell, red blood cell, packed cell volume haemoglobin, catalase and super oxide dismutase, decreased, while mean corpuscular haemoglobin, mean corpuscular haemoglobin aminotransfersa, malondialdehyde increased significantly when compared with the control (P<0.056) following exposure to sublethal concentrations. histological alterations observed include congested blood vessels, inflammatory oedema, necrosis and ulceration of primary and secondary lamelle. The study showed that atrucine was toxic to clarias ganepirus and it’ s use agricultural tulbs close to aquatic bodies should be strictly monitored. SOD activity 26.77±0.37 U/L, of fish exposed to 0.75 mg/L atrazine was insignificantly (p>0.05) lower than the control 30.53±1.04 U/L. However, SOD values of fish exposed to 1.13 mg/L and 2.25 mg/L, 23.61±0.37, 19.46±1.23 U/L respectively were significantly lower (p<0.05) than the control. CAT activity 14.22±0.10, 13.04±0.32, 12.95±0.37 U/L of fish exposed to 0.75 mg/L, 1.13 mg/L and 2.25 mg/L atrazine respectively were significantly lower (p<0.05) than the control 18.24±1.14 U/L. MDA value of 2.29.0±0.11 mmol/L of fish exposed to 0.75 mg/L atrazine were statistically insignificantly higher (p>0.05) than the control 1.52±0.31 mmol/L. However, MDA values of 3.21±0.17, 3.57±0.21 mmol/L of fish exposed to 1.13 mg/L and 2.25 mg/L, respectively were significantly higher (p<0.05) than the control. AST of 19.0±1.15 U/L for fish exposed to 0.75 mg/L atrazine was insignificantly (p>0.05) higher than the control 14.33±0.58 U/L. However, AST values of fish exposed to 1.13 mg/L and 2.25 mg/L, 22.67±0.88, 23.33±2.67 U/L respectively were significantly (p<0.05) higher than the control. ALT value of 31.67±1.15, 36.67±0.67, 41.0±0.58 U/L of fish exposed to

0.75 mg/L, 1.13 mg/L and 2.25 mg/L atrazine respectively were significantly (p<0.05) higher than the control 27.0±0.58 U/L.

and Physiology

exposed to atrazine

solutions

stress parameters

References 

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Human activities like land cover change, urbanization, and industrialization have impaired ecosystems for several decades due to increase access to natural resources for an exponential growing population (Carpenter et al., 2011). The anthropogenic

 

activities lead to water contamination with diverse inorganic and organic chemicals. Agrochemicals, pharmaceuticals, hormones, industrial and consumer products, acids, alkalis, and heavy metals have been reported in aquatic ecosystems (Schwarzenbach et al., 2010; Wittmer et al., 2010). An uncertain number of chemicals may potentially be released into the aquatic environment by diverse routes like point sources, remobilization from contaminated sediments and groundwater input (Ritter et al., 2002).

Moreover, agrochemicals may enter the aquatic environment by soil run-off, spray drift, surface runoff, or drainage (Ashauer et al., 2006). Depending on the physicochemical properties, a chemical can persist in the aquatic environment (e.g., polychlorinated biphenyls, polychlorinated dibenzofurans, hexachlorobenzene), distributed via water or air over long distances (e.g., polychlorinated biphenyls), transformed into even more toxic products (e.g. the biocide triclosan degrades to methyl-triclosan) as well as degraded to nontoxic forms (Ritter et al., 2002). Additionally to the diverse exposure routes in the environment, chemicals may accumulate along the food web and may adversely affect freshwater organisms and human health (Brock et al., 2006).

Fish is a cheap and essential source of animal protein (Banaee, 2013; Angaye et al., 2015; Ineyougha et al., 2015; Izah and Angaye, 2015) and lipids for humans and domestic animals (Banaee, 2013). In Nigeria, as much as 10% of the population, (about 14 million people) depend wholly or partly on the fish or the fisheries sector for their livelihood (FAO, 2006). Due to its readily digestibility and immediately utilizability by the human body, fish is thus suitable and complementary for regions of the world with high carbohydrate diet (FAO, 2006). In Nigeria, the genus Clarias is a commonly acceptable fish with economic importance (Adewumi et al., 2015; Ogamba et al., 2015).

The use of herbicides to control weeds has been recognized as a part of agricultural practices worldwide. Unfortunately, the indiscriminate use of these herbicides to improve agricultural production and yield may impact non-target organisms, especially aquatic life forms and their environment (Battaglin et al., 2008). Herbicides are generally applied in dry season or early rainy season, which often coincide with the breeding season of many fish species. Some of these fishes breed in aquatic habitats receiving the runoff drained from the cultivation fields (Ladipo et al., 2011). Atrazine has low volatility, but its moderate water solubility (33 mg/L at 25 ◦C) makes it relatively mobile in soil and aquatic environments. It tends to partition into the water column rather than sorbing to sediments (Giddings et al., 2004).

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) is one of the most commonly used herbicides found in the rural environments. It is extensively used on corn, sorghum, sugarcane, pineapples, and to some extent on landscape vegetation (Battaglin et al., 2008). Rated as moderately toxic to aquatic species, atrazine is mobile in the environment and is among the most detected pesticides in streams, rivers, ponds, reservoirs and ground waters (Scrubner et al., 2005; Battaglin et al., 2008). It has a hydrolysis half-life of 30 days and relatively high water solubility (32 mgL-1), which aids in its infiltration into ground water (Orme and Kegley, 2004). Atrazine concentrations of 20 μg·L-1 have been commonly detected in surface water runoff, while concentrations as high as 700 μg·L-1 have been reported in underground water (Selim, 2003). Due to the low persistence of atrazine herbicide, repeated applications are practiced to control weeds in agricultural fields. As a result, large quantities of the herbicide find their ways into water bodies (Battaglin et al., 2008). The mode of action of atrazine is blocking electron transport in photosystem 11 leading to chlorophyll destruction and blocking photosynthesis in plants. When atrazine was first released for agricultural use, it was thought that since photosynthesis is limited to plants, animals would be immune to any effects of atrazine. It was soon suspected that atrazine might

have non-target action in animals including genotoxic (De Ventura Campo et al., 2008), clastogenic and biochemical effects (Weigand et al., 2001). The indiscriminate use of this herbicide, careless handling, accidental spillage or discharge of untreated effluents into natural water ways have harmful effects on the fish populations and other aquatic organisms and may contribute to long term effects in the environment (Battaglin et al., 2008). Sub-lethal effects with biochemical and histopathological alteration of fish tissues may occur with long term exposure to levels of less than 2 mg·L-1 of atrazine (Lakra and Nagpure, 2009).

Fish can serve as bio-indicators of environmental pollution and can play significant roles in assessing potential risk associated with contamination in aquatic environment since they are directly exposed to chemicals resulting from agricultural production via surface run-off or indirectly through food chain of ecosystem (Lakra and Nagpure, 2009). Fish are endowed with defensive mechanisms to counteract the impact of reactive oxygen species (ROS) resulting from metabolism of various chemicals or xenobiotics. Oxidative stress develops when there is an imbalance between pro-oxidants and antioxidants ratio, leading to ROS generation (Liu et al., 2006). Environmental contaminants such as herbicides, heavy metals and pesticides are known to modulate antioxidant defensive systems and cause oxidative damage in aquatic organisms by ROS production (Liu et al., 2006; Monteiro et al., 2006). ROS such as hydrogen peroxide (H2O2), superoxide anion O2- and hydroxyl radical (OH·) at supranormal levels can react with biological macromolecules potentially leading to enzyme inactivation, lipid peroxidation (LPO), DNA damage and even cell death (Banudevi et al., 2006). Toxicity testing of chemicals on animals has been used for a long time to detect the potential hazards posed by chemicals to environment and human. Bioassay technique has been the cornerstone of environmental health and chemical safety. Aquatic bioassays are necessary in water pollution control to determine whether a potential toxicant is dangerous to aquatic life and if so, to find the relationship between the toxicant concentration and its effect on aquatic animals (Olaifa et al., 2003). The application of environmental toxicology studies on non-mammalian vertebrates is rapidly expanding (Ayoola, 2008).

Herbicides are indiscriminately used with little or no regulation. They persist in the environment for a long time. They are applied to control weeds, but they end up in aquatic environments, affecting non-target organisms including fish. They may cause fish kill, affect fish behaviour, feeding, growth and ultimately reduce fish productivity (Yaji, 2012). Atrazine in soil breaks down through interaction with environmental compounds. atrazine can persist for months to as long as a year once it enters surface or ground water because the degrading bacteria are rare or nonexistent in surface water and groundwater (Rohr and McCoy, 2010).

Furthermore, atrazine has been associated with adverse health effects in humans. It stimulates aromatase activity in human ovarian cancer cells (Albanito et al., 2008), and increases congenital disabilities and infant mortality (Mattix et al., 2007, Winchester et al., 2009). In animals, it causes sexual abnormalities in male frogs at levels commonly found in rivers, streams and even rain, 30 times below the level allowed in drinking water. In addition, atrazine is not readily broken down under alkaline soil conditions. It has a carryover effect, a generally undesirable property of herbicides. Usually, most aquatic animals including fishes respire through their gills and sometimes with the help of skin. These respiratory organs frequently encounter hazardous pollutants present in water in different forms. These pollutants may lead to the alteration in the common area, which causes the reduction in oxygen consumption and physiological imbalance in the organism (Chamarthi et al., 2014; Muttappa et al., 2014).

The increase in the use and application of herbicides in Nigeria agriculture contributes significantly to aquatic pollution and reduction in water quality. Fish are one of the most widely distributed organisms in an aquatic environment. Being susceptible to environmental contamination, fish may reflect the extent of the biological effects of environmental pollution in waters (Ramesh et al., 2009). Fish are widely used to evaluate the health of aquatic ecosystems, and biochemical changes observed in fish serve as biomarkers of environmental pollution (Schlenk and Di-Giulio, 2002).

Fish are often sentinel organisms for ecotoxicological studies because they play several roles in the trophic web, accumulate toxic substances and respond to low concentrations of mutagens (Cavas and Ergene-Gözükara, 2005). Therefore, the use of fish biomarkers as indices of the effects of pollution are of increasing importance and can permit early detection of aquatic environmental problems (Van Der Oost et al., 2003). Mortality or bioassay experiments in general present the most preferred way to evaluate the ecological influence of toxic compounds as their effects on fish and ecological risks cannot be determined by chemical analysis (Svobodova et al., 2003). Acute toxicity tests provide basis for understanding the limiting effects of various chemicals on organisms. Similarly, knowledge of the sub-lethal effects of toxic compounds at the biochemical, genetic and histopathological levels is vital for delineating fish health status and understanding future ecological impact (Schlenk and Di-Giulio, 2002).

The study aimed to assess the toxicity of atrazine on juvenile Clarias gariepinus.

 

The specific objectives were: