O Adeyemo, F Ajani, O Adedeji, O Ajiboye
acute toxicity, african catfish, blood indices, lead, nigeria
O Adeyemo, F Ajani, O Adedeji, O Ajiboye. Acute Toxicity and Blood Profile of Adult Clarias gariepinus Exposed to Lead Nitrate. The Internet Journal of Hematology. 2007 Volume 4 Number 2.
Environmental stressors and their associated risks have always been an inherent part of society. Aquatic ecosystems are especially sensitive to exposure to toxic contaminants. Pollutants either individually or in combination may have sub-lethal effects at the cellular, organ and individual level. The count of red blood cells is quite a stable index and the fish body tries to maintain this count within the limits of certain physiological standards using various physiological mechanisms of compensation. Studies have shown that when the water quality is affected by toxicants, any physiological changes will be reflected in the values of one or more of the haematological parameters (Van Vuren, 1986). Blood cell responses are important indicators of changes in the internal and/or external environment of animals. In fish, exposure to chemical pollutants can induce either increases or decreases in haematological levels. Their changes depend on fish species, age, the cycle of the sexual maturity of spawners and diseases (Golovina, 1996; Luskova, 1997).
Like in warm-blooded animals, changes in the blood parameters of fish, which occur because of injuries of the latter organs or tissues, can be used to determine and confirm the dysfunction or injuries of the latter (organs or tissue). However in the fish, these parameters are more related to the response of the whole organism, i.e. to the effect on fish survival, reproduction and growth. It should be noted that although the mechanisms of fish physiology and biochemical reaction to xenobiotics has not been investigated enough, it is obvious that species differences of these mechanisms exist.
Fish live in very intimate contact with their environment, and are therefore very susceptible to physical and chemical changes which may be reflected in their blood components (Wilson and Taylor, 1993). In fish, exposure to chemical pollutants can induce either increases or decreases in haematological levels. Blood tissue truly reflects physical and chemical changes occurring in organism; therefore, detailed information can be obtained on general metabolism and physiological status of fish in different groups of age and habitat. Early diagnosis is also possible when evaluating haematological data, particularly blood parameters (Folmar, 1993; Golovina, 1996; Luskova, 1997). Furthermore, it should be noted that haematological indices are of different sensitivity to various environmental factors and chemicals (Lebedeva
Previous haematological study of nutritional effects (Rehulka, 2000), infectious diseases (Rehulka, 2002a) and pollutants (Rehulka, 2002b) brought knowledge that erythrocytes are a major and reliable indicator of various sources of stress (Rainza-Paiva
Materials And Methods
Ninety apparently normal adult
The fish were considered as normal on the basis of their external appearance and absence of symptoms of diseases. Fishes were transported in a container filled with pond water and then acclimatized under laboratory conditions for two weeks (14 days) prior to the commencement of the experiment. During the acclimatization period, the fish were fed 4% of their body weight with commercial feed pellets (40% crude protein, 4.22% fat, 5.88% crude fiber, 10.30% ash and 10.03% moisture) once daily and the water was renewed every other day. The mortality throughout the period of acclimatization was less than 10%.
Stock solution of lead nitrate [Pb (No3)2] was made by dissolving 50 g of lead nitrate in 1 liter of well-water (Water TºC = 27.0 ± 0.1, pH = 7.26 ± 1.1. A 96-hour daily static renewal acute toxicity was conducted following the methods described by Sprague (1971).
Fish were randomly allotted at six (6) fish per group (A, B, C D and E) based on the concentrations of lead nitrate they were exposed to (0.0, 25, 50, 100 and 200 mg/l) respectively. The experiment was set up in triplicates. Fish allotted to group A served as the control. Fish were observed at 2 hours intervals for the first 2 hours after which they were observed at 6 hours interval. Dead fish were immediately removed from the experimental set-up. After the expiration of the experiment, blood was collected from the remaining fish to assess the effect of acute exposure to lead nitrate on blood parameters. Fish were anaesthetized in 8 litres of well-water containing 0.2 g of benzocaine, which had been dissolved in 5 ml acetone.
Blood was drawn from the posterior caudal vein according to Schmitt
Results are presented as mean with standard error of mean (SEM). The results were also analysed using student's
Results And Discussion
The toxic effects of heavy metal on fish are multidirectional and manifested by numerous changes in the physiological and chemical processes of their body systems (Dimitrova
Literature shows that changes in haematological indices of fish caused by heavy metals and their mixtures are different. They are predetermined both by the concentration of heavy metals in the water and time of exposure, and both these factors can cause reversible and irreversible changes in the homeostatic system of fish. It is well known that lead causes early mortality of mature red blood cells and inhibition of haemoglobin formation through inhibition of erythrocyte alpha-amino levulinic acid dehydratase (ALA-D). The result is anaemia at high lead exposures or compensating erythropoiesis at lower exposures (Hodson
Haemoglobin concentrations reflect the supply of an organism with oxygen and the organism itself tries to maintain them as much stable as possible. This study shows that mean haemoglobin in the control was 10.42, 8.52 in group B, 8.55 in group C, 9.3 in group D and 7.67 in group E. A decrease in the concentration of haemoglobin in blood is usually caused by the effect of toxic metals on gills, as well as decrease in oxygen, which also suggests anaemia or confirms toxic impact of lead in
A non-dose dependent reduction in RBC level of the treatments was observed (Fig. 4). Haematological indices (RBC count, concentration of haemoglobin and haematocrit) have been reported to indicate secondary responses of an organism to irritants (Rogers
The MCV, MCH and MCHC increased considerably in all treatments compare to the control (Figs. 9-11). However, the increase in MCV was significant (p<0.05) only in groups C and E (P = 0.033 and 0.016, respectively), while the increase in MCH and MCHC recorded by the treatments was significant (p<0.05) only in group C (p= 0.00026, 0.00034). This is in agreement with the work of Shah, (2006) following a short-term exposure of tench (
Olanike K. Adeyemo (DVM, MVPH, PHD) Department of Veterinary Public Health And Preventive Medicine, University of Ibadan, Ibadan, Nigeria. TEL: +234-805-545-45440 E-MAIL: firstname.lastname@example.org; email@example.com