T Sunmonu, O Oloyede
anaemia, blood cells, catfish, crude oil, haemoglobin, rat
T Sunmonu, O Oloyede. Haematological Response of African Catfish (Clarias gariepinus) and Rat to Crude Oil Exposure. The Internet Journal of Hematology. 2007 Volume 4 Number 1.
The effect of Bonny light crude oil on some haematological parameters was studied in African catfish (
Crude oil is a complex mixture of hydrocarbons from which various petroleum products such as gasoline, kerosene, fuel oil, lubricating oil, wax and asphalt are derived [1, 2]. Several toxic components of crude oil such as polycyclic aromatic hydrocarbons (PAHs) and water soluble fractions (WSF) have been documented [3, 4]. Crude oil and its refined petroleum products contains several organic and inorganic substances including atoms of sulphur, nitrogen, oxygen, oxygen as well as metals such as iron, vanadium, nickel and chromium .
Crude oil spillage has over the years, led to the pollution of the aquatic and terrestrial ecosystems. Many blood parameters are known to be affected by environmental and physiological factors. Therefore, haematological studies are of ecological and physiological interest such as helping to understand the relationship of blood characteristics to the habitat and adaptability of the species to the environment .
The effects of oil spill on aquatic lives are caused by either the physical nature of the oil (physical contamination and smothering) or by its chemical components (toxic effects and accumulation leading to tainting). Aquatic lives may also be affected by clean up operations or indirectly through physical damage to the habitats in which plants and animals live . The main threat posed to living resources by the persistent residues of spilled oils and water-in-oil emulsions (“mousse”) is one of physical smothering. The animals and plants most at risk are those that could come into contact with a contaminated sea surface. These include aquatic mammals and reptiles; birds that feed by diving or form flocks on the sea as well as aquatic lives on shorelines .
Previous studies have shown that crude oil can have both lethal and sub-lethal effects on a wide range of organisms. These include the observation that a relatively short exposure to crude oil led to the inhibition of growth in weaner rabbits . A similar observation was also reported in juvenile pink salmon (
Materials and Methods
a. Collection of crude oil and preparation of various mixtures
Bonny light crude oil was obtained from the Department of Petroleum Resources (DPR), Nigerian National Petroleum Corporation (NNPC), Port Harcourt, Nigeria and diluted with borehole water to obtain mixtures of 0.1%, 0.25%, 0.5%, 0.75% and 1% by volume (Table 1). These concentrations are representative with a view to mimicking the effect of natural dilution as the crude oil moves along with water in the event of oil spillage.
b. Experimental fish and treatments
One hundred and twenty apparently healthy juvenile catfish (
c. Formulation of diet
At the end of the 30 hours experimental period, the catfish were harvested, oven dried at 40oC and used as a source of protein to formulate diet for albino rats. The diet for each group was formulated by mixing known quantities of sources of each food class (Table 2). The food items were mixed together and manually made into pellets to feed albino rats.
d. Experimental rats and treatments
Sixty albino rats (
e. Determination of haematological parameters
The Automated Haematologic Analyzer (Sysmex KX – 21) was used to analyze the haematological parameters like PCV, WBC, RBC, MCH, MCHC, HGB and PLT. The analyses were carried out based on standard methods [12, 13].
f. Statistical analysis
All data were analysed statistically using Analysis of Variance (ANOVA) test . Significant difference between the treatment means was determined at 5% confidence limit using Duncan's Multiple Range Test .
The haematological parameters of catfish and rat exposed to various levels of crude oil polluted water and diet are as presented in Tables 3 and 4 respectively. The data obtained in the study revealed that there was a significant reduction (p<0.05) in the concentration of all the haematological parameters analyzed in both the catfish (Table 3) and rat (Table 4) as the level of exposure to crude oil increased. Indeed, the least concentration of all the blood parameters analyzed was observed in the catfish and rat exposed to 1% concentrated polluted water and diet respectively.
One of the major problems of the inhabitants of the Niger Delta region of Nigeria is contamination of water and aquatic lives by crude oil. This contamination may not necessarily lead to outright mortality but may have significant effects which can lead to physiological stress and dysfunction in animals . The severity or degree of the problems in the inhabitants of the area is dependent upon the point of contact with the polluted water. Hence, justifying the need for the preparation of different crude oil concentrations.
In the present study, it is obvious that exposure of catfish and rat to crude oil caused a significant reduction (p<0.05) in RBC count. Consequently, HGB and PCV reduced significantly (p<0.05) as the concentration of crude oil increased. The observed reduction in the concentrations RBC, HGB and PCV suggest an anaemic condition in the crude oil treated catfish and rat. The significant reduction (p<0.05) in RBC count may be attributed to cytotoxic effect and suppression of erythropoiesis caused by constituents of the crude oil. This is in line with previous studies which showed that the erythroid colony-forming unit (CFU-e) was very susceptible to the cytotoxic effect of the crude oil derivative benzene .
The RBC count dropped significantly (p<0.05) as the concentration of crude oil increased. This would imply reduction in the level of oxygen that would be carried to the tissues and the level of carbon dioxide returned to the lungs would also be reduced. The values obtained for MCH and MCHC serve to indicate variations in erythrocyte shape, size and haemoglobin content. Reduced MCH and MCHC as observed in the present study, which is an indicator of anaemia, was also reported in previous studies .
Similarly, PLT concentration was observed to reduce significantly (p<0.05) as the concentration of crude oil increased (Tables 3 and 4). In a related study, toxic components especially those in crude oil changed blood chemistry and induce anaemia by causing bone marrow hypoplasia and interfered with platelet production in the animals, hence the reduced values .
The major functions of WBC are to fight infection, defend the body by phagocytosis against invasion by foreign organisms and to produce or at least transport and distribute antibodies in immune response. A significant reduction (p<0.05) in WBC count with increase in crude oil concentration (Tables 3 and 4) suggests that the catfish and rat are exposed to high risk of infection. The observation in this study is similar to the findings of previous studies in which there was a reduction in total WBC count in goats as the level of crude oil concentration increased . It was argued that the reduction in WBC count in goats may be as a result of stress imposed by crude oil hydrocarbons.
The result generated from this study is suggestive of the fact that crude oil is an environmental stressor which causes depression of RBC and WBC counts. Thus, it can be concluded that crude oil has serious consequences on haematological parameters in catfish and rat.
Dr. Taofik O. Sunmonu Phone number: +2348033939464 E-mail: email@example.com