Haematology in Juveniles of African Catfish (Clarias gariepinus) Exposed to Primextra Gold® (Atrazine) Herbicide

Introduction

The ever-increasing world population and the attendant increase in food demand necessitated that new ways of increasing agricultural output be sought. In an attempt to increase agricultural output, man relies heavily on the use of chemicals to protect crops from pests, right from the time of dressing of seeds before planting, through fighting weeds and other pests on the farm, to the preservation of already harvested products. On one side, benefits derived from the use of pesticides in agriculture are immense, but on the other side, environmental pollution and/or degradation is one major problem that is linked to their application [1].

The presence of pesticides in the environment has caused significant social and scientific development anxiety worldwide, as all-over-the-world their extensive use can create potential risks to the environment and human health, and easily pollute bodies of water thereby resulting in extensive damage to non-target species, including fish [2]. Be it intentional or unintentional application, water is contaminated through direct application into the aquatic system, drifts during spray, atmospheric fallout as rain and dust, soil erosion, sewage, industrial effluent and occasionally by spillage Moreno MA, et al. [2].

The aquatic environment is particularly one vulnerable area as it is the ultimate recipient of pollutants due to basin drainage. The aquatic ecosystems have been known to receive a wide spectrum of pollutants, which may be introduced to them directly or indirectly. The indiscriminate use of chemicals has resulted in large scale reduction in aquatic productivity. Pesticides have different diverse impacts on aquatic animals especially fishes which are of economic importance and high value from the point of biological conservation [3]. Environmental pollution by pesticides has become a serious problem in terms of global conservation and animal and human health [4, 5]. Besides overexploitation and habitat loss, pollution from herbicides is one of the main causes of fish species and other aquatic organisms’ loss [6].

Atrazine (2-Chloro-4-ethylamino-6-Isopropylamino- s-triazine) is one of the most currently and widely used herbicides in this part of the world and several studies have detected its presence in water bodies at levels above the limits determined by local and international authorities (for example the Maximum Contaminant Level of 3μg/L by USEPA) [5]. Due to its potential to bio accumulate in organisms and its proposed negative effects, the application of atrazine has been banned in many countries (in the EU region by European Commission Directive No. 2004/248/ EC) [7].

Fish is highly nutritious, easily digestible and a much sought after food. Nutritional value of fish depends on their biochemical composition, which is affected by water pollution. The African catfish, Clarias gariepinus is one of the richest sources of animal protein to man [8]. The aim of this study is to evaluate the toxicity of Primextra Gold® (atrazine) to the juveniles of the African catfish, Clarias gariepinus.

Discussion

The health status of blood in living organisms is imperative because of its numerous roles including Oxygen and nutrient transportation. Blood plays a major function in the regulation of internal environment of a system (homeostasis) as stated by Ada FB, et al. [9]. After exposure to the concentrations of Primextra Gold® (Atrazine) herbicide, the results for haematological indices showed significant differences in Hb (haemoglobin), RBC (Red Blood Cells), WBC (White Blood Cells), PCV (packed cell volume), MCV (mean corpuscular volume), MCH (mean corpuscular haemoglobin) and MCHC (mean corpuscular haemoglobin concentration) between the control and the various treatments. Usually any intense or severe attack on it can out rightly lead to death of an organism. Reduction in haemoglobin concentration with increased concentration of atrazine observed in this study conforms to the report of Edori OS, et al. [10] in which Clarias gariepinus was exposed to sublethal concentrations of paraquat. The decrease in haemoglobin may have led to a condition in which the capacity of the blood to transport oxygen to tissues is reduced; consequently, decline in red blood cells may depict a reduction in cellular iron which supports Oxygen carrying potential of blood. Ada FB, et al. [9] opined that haemoglobin reduction invariably contributes to the stress and anaemic state of organisms which further alters respiration, metabolism and induces morbidity and mortality. Hence, haemoglobin reduction in treated fish might have impaired Oxygen supply to the various tissues. The red blood cells decreased with increase in concentration of atrazine which is similar to findings of Odo JI, et al. [11] who revealed that reduced red blood cell count implies a reduction in the level of Oxygen carried to the tissues. According to Adedeji OB, et al. [12], high concentration of pesticides or long term exposure of fish to different concentrations of pesticides usually decreases red blood cells indices and this is evident in the present study that showed reduction in all the concentrations compared to the control. Adedeji OB, et al. [12] revealed that red blood cells break down at an early stage in the incidence of pernicious anaemia. White blood cells showed significant difference, it increased with increase in concentration of atrazine and this is contrary to the findings of Ajani F, et al. [13] who reported a continuous decrease with increase in concentration of malathion. The increase in white blood cells from this investigation with increase in concentration could be due to attempts made by the fish to fight against the effects of the pollutant which could have led to production of more white blood cells to improve the health status of the fish. Increase in white blood cell count is seen as an adaptation of organisms and their efforts to combat invaders from body cells [9]. The population of exposed white blood cells which have been swiftly multiplied by previously surviving ones according to Popoola OM [14] is usually comprised of new or younger cells (because the old ones are killed) that would fight the invaders. They increase in the number of younger cells may be responsible for the differences in the white blood cell volume observed between exposed and control groups. Therefore, sharp increase in white blood cells (WBC) count above that of the control group could be resistance to prevalent unwanted change and adaptability to the environment. Packed cell volume decreased in this study and that implied poor transportation of oxygen and absorbed nutrients which could possibly have resulted to a decreased status of fish condition. An anaemic response in the test fish was perhaps also due to the destruction of intestinal cells [11, 15] reported similar trends in fish exposed to pedimentiline. The fluctuations in the MCV, MCH and MCHC in this study indicates that the concentration of haemoglobin in the red blood cells were lower in the exposed fish than in the control over the exposure period. Mean corpuscular haemoglobin, which indicates blood level conditions, fluctuated, thus indicating anaemic condition in the test fish exposed to atrazine. Ada FB, et al. [9] reported that herbicides may trigger the multiplication of the blood cells to compensate for the low load of haemoglobin per cell whereas Adeyemo OK [16] explained that decrease in MCV, MCH and MCHC imply the malfunctioning of the organs responsible for blood production in fish. However, MCV fluctuations in values recorded in fish exposed to concentrations of atrazine did not concur with the findings of Ada FB, et al. [9] who reported that MCV did not change significantly in the exposed groups compared with the control. Moreover, the reduction in these blood metabolites is an indication of anaemia caused by exposure to the toxicant.

Water physicochemical parameters usually serve as indicators of the quality of water bodies, revealing the toxic levels and effects of chemicals present in aquatic media and on aquatic organisms. During the test period, only temperature showed no significant difference between the mean values of the treated fish and that of the control. Significant changes were however recorded in the mean values of pH, dissolved Oxygen (DO), total dissolved solids (TDS) and electrical conductivity (EC) between the control and various treatments. Generally, means of temperature and pH fluctuated slightly between the control and the treated solutions; this is line with studies of Ayoola SO [17] who reported slight changes in test water temperature and pH on exposure of O. niloticus juveniles to glyphosate herbicide. There was a significant relationship (p˂0.05) between the rates of dissolved Oxygen with atrazine concentration, as the mean values decreased with increase in concentration of the toxicant in the test solutions. The significant negative correlation between dissolved Oxygen (DO) values and toxicant concentration as dissolved oxygen decreased considerably with increasing concentrations of atrazine is in consonance with earlier reports of Ajani and Awogbade [18] and Ada FB, et al. [9] that reported same decline in dissolved Oxygen (DO) in exposed fish studied under laboratory conditions. This may be due to stress induced by atrazine which resulted in agitation and abnormal behaviours of the test fish, thereby, leading to reduced dissolved Oxygen (DO) level in the test solutions. Ada FB, et al. [9] suggests that it may be possible that some herbicides make use of oxygen in decomposition process; this may probably be one of the reasons for decline in oxygen in treated test solutions in the present study. Total dissolved solids (TDS) and electrical conductivity (EC) increased with increasing concentrations of atrazine indicating organic matter content and electrolyte concentrations. The changes might have been as a result of the active ingredient and also the level of concentration of the toxicant in test solutions. These are in agreement with the findings of Akaahan TJ, et al. [19] on the effects of zinc on water quality when C. gariepinus juveniles were examined and on the toxicity of paraquat dichloride on water quality during exposure of adult C. gariepinus Popoola OM [14, 20, 21].

Conclusion

Atrazine alter the pristine state of aquatic environment and kill non-target organisms like fish. The effects of atrazine on haematology and water physicochemical parameters were examined under laboratory conditions. An indication of subtle but rapid deterioration of life due to the effects of atrazine exerted on fish was evident in the blood parameters because small concentrations of toxicants in water bodies are harmful. Concentrations of atrazine on juveniles of Clarias gariepinus caused alterations in haematological parameters (Haemoglobin, Red Blood Cell, White Blood Cell, Packed Cell Volume, Mean Corpuscular Volume, mean corpuscular haemoglobin and Mean Corpuscular Haemoglobin Concentration) of exposed fish and caused a range of defects and health problems like anaemia as a result of increased white blood cell of the test fish. It is however imperative to note that the life of an organism is in the blood, so the enormous impact of atrazine on the blood characteristics posed an adverse damage to the treated fish. At exposure to concentrations of atrazine, fish showed abnormal behaviours such as restlessness, gasped for air, and vertical movements. Dissolved Oxygen level in the test solutions reduced drastically and this can induce death in fish. Atrazine application to enhance crop yield; although produces an immediate satisfactory result, but it consequently carries an accompanying side effect, moreover, when we act locally, the impact may be felt globally so let us be environmentally conscious and seek to achieve environmental sustainability for future generations.

Recommendations

1. Based on the findings of this work that atrazine affects physicochemical parameters of water and fish haematology, Biological methods of controlling weeds and organic farming should be encouraged.
2. Atrazine should be applied at a minimum effective concentration so that non-target organisms will not be affected.
3. Researches on the rate of atrazine in Nigeria water bodies should be conducted and the effects of atrazine to other biochemical parameters on Clarias gariepinus should be examined due to the fact that atrazine affects physicochemical parameters of water and fish haematology.