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Research Article
 

Effect of Atrazine on Nile Tilapia (Oreochromis niloticus Trewavas, 1983)



A.O. Agbon, I.T. Omoniyi, W.O. Abdul, F.I. Adeosun, A.A. Idowu and O. Odulate
 
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ABSTRACT

Mechanization of agriculture to promote and improve the yields from agricultural practices has necessitated the use of pesticides and other agrochemicals. The effects of using these pesticides on the environment are rarely considered by farmers. This study investigated the acute and sublethal effect of atrazine on tilapia, an ubiquitous culturable fish species. The 96 h LC50 was determined using static renewal bioassay method while the effect on haematological parameters was determined after exposure for 3 weeks to sublethal doses of atrazine. The LC50 was found to be 6.977 mg L-1. Sublethal exposure resulted in anaemia and increased the white blood cell counts.

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  How to cite this article:

A.O. Agbon, I.T. Omoniyi, W.O. Abdul, F.I. Adeosun, A.A. Idowu and O. Odulate, 2014. Effect of Atrazine on Nile Tilapia (Oreochromis niloticus Trewavas, 1983). Trends in Applied Sciences Research, 9: 598-602.

DOI: 10.3923/tasr.2014.598.602

URL: https://scialert.net/abstract/?doi=tasr.2014.598.602
 
Received: July 12, 2014; Accepted: October 16, 2014; Published: December 01, 2014



INTRODUCTION

The issue of food security in Nigeria has raised questions on how to feed the teeming population that is in excess of 140 million inhabitants. Food security in Nigeria has been a topical issue of discourse in government circle since the initiation of the Millennium Development Goals (MGDs) at the onset of the twenty first century. Government representatives have not failed to emphasize the importance of food to household/family and national security. This informed the government initiative to set up the National Special Programme on Food Security (NSPFS) in 2000. To meet food security, the three tiers of governments have intensified the promotion of agriculture beyond subsistence scale. The mechanization of agriculture cannot be divorced from the use of pesticides and other agrochemicals to promote and improve the yields from agricultural practices. The effect of using these pesticides on the environment is rarely considered by farmers and perhaps, government itself. There is abundant literature to support the reports of over-dosage and gross abuse by illiterate, semi-literate and even literate farmers. Water, soil and sediments serve as the ultimate sinks for most chemicals produced and used by man. These pesticides end up in water bodies where they could exert either acute or sublethal effects on the aquatic biota. Scientists, resource managers and medical experts today widely accept the idea that human society is dependent upon a healthy environment and that continued environmental degradation threatens, the quality of life (Bickham et al., 2000). A standard approach for evaluating the threat a xenobiotic poses to environmental health is to test whether environmentally realistic concentrations have adverse effects on organisms that may be harbingers of possible risk to humans or ecosystem services. This study was conducted to determine the acute and heamatological effects of atrazine on tilapia.

MATERIALS AND METHODS

A total of 150 tilapia fish were obtained from the 3 ha reservoir of the integrated fish farm of the University of Agriculture, Abeokuta and taken to the Laboratory where they were acclimated in out-door rectangular glass-fibre tanks of 2x1x0.5 m for a period of two weeks prior to the commencement of experiment. From the out-door fibre-glass tanks, 120 healthy tilapia with a mean weight of 11.53±2.32 g and mean standard length of 10.50±2.15 cm, were selected and then transferred in-doors into transparent glass aquaria of 0.6x0.3x0.3 m 48 h prior to introduction of toxicant. All the glass aquaria were covered with a 1 mm mesh size nylon net on a wooden frame to prevent the fish from jumping out of the tanks. The water in out-door rectangular tanks were routinely refreshed every other day by 50% exchange using declorinated municipal water supply from underground water storage tanks. The atrazine which was purchased from a government accredited Agro-Allied shop had stock solution concentration of 600 g L-1 Atrazine.

During acclimation and exposure to sub-lethal tests, 10 fish/tank the fish were fed 3% body weight daily with 2 mm size Multi feed® extruded fish feed (45% protein). The Total Ammonia-Nitrogen (TAN), nitrate-nitrogen and pH were monitored with HANNA Scientific® water quality kit once a week while dissolved oxygen and temperature were measured with Oxyguard® Handy Beta meter daily. These were done to ensure that the parameters were within the tolerant range for the fish.

The lethal test to determine the 96 h LC50 was conducted using the method described by EIFAC (1983). The concentrations of atrazine used were 5, 6.25, 7.50 and 8.75 mg L-1 while the control had no toxicant. Observations of the state of the fish in test aquaria tanks were made at fixed intervals from start viz: 3, 6, 12, 24, 48, 72 and 96 h. A record of number of survivors in each concentration was made. From these data, the LC50 values were calculated by probit analysis using the US EPA software (Probit Program Version 1.5).

Sublethal tests were conducted in duplicate bioassays with concentrations of 1.20 and 0.62 mg L-1 atrazine. The tilapia were exposed for a period of 21 days after which 5 fish each were taken from each treatment replicate including control, for haematological analysis. The blood samples were obtained from each of the fish via puncture of the dorsal aorta and collected in heparinized microcapillary tubes for assay. Three sub-samples were taken from each fish. The blood samples collected were subjected to standard haematological methods according to Svoboda et al. (2001).

RESULTS

The LC50 was calculated to be 6.977 mg L-1 with 95% confidence interval of between 6.55 and 7.35 mg L-1 as shown in Fig. 1. The mean haematological parameters are presented in Table 1 while the water quality parameters which were measured were found to be within the acceptable range for the test fish (Table 2).

Image for - Effect of Atrazine on Nile Tilapia (Oreochromis niloticus Trewavas, 1983)
Fig. 1:Probit plot showing tilapia mortality in atrazine

Table 1:Mean±SD values of haematological indices of tilapia exposed to sublethal concentrations of atrazine
Image for - Effect of Atrazine on Nile Tilapia (Oreochromis niloticus Trewavas, 1983)

Table 2:Water quality parameters during exposure
Image for - Effect of Atrazine on Nile Tilapia (Oreochromis niloticus Trewavas, 1983)

DISCUSSION

Acute toxicity testing is the accepted valid parameter for government regulations and guidelines for water pollution and control (Rand et al., 1995). The acute toxicity test of Atrazine in tilapia bioassays revealed the 96 h LC50 to be 6.977 mg L-1. Sublethal test revealed that it induced anaemia which could be attributed to destruction of erythrocytes or the inhibition of erythropoiesis and hemosynthesis (Omoregie, 1998; Agbon et al., 2002; Agbon, 2009) as shown in the significant decrease in RBC count (p<0.05) which indicated that the fish were stressed during the sublethal exposure to the atrazine. The PCV values in the tilapia blood were observed to have decreased significantly (p<0.05). A decrease in PCV may indicate the extent of the shrinking cell size due to exposure in the toxicant (Ahmad et al., 1995). These decreases in the PCV values indicated that atrazine treatment might be interfering with the normal physiology of RBC. The tilapia blood Hb were observed to have decreased significantly (p<0.05). Sawhney and Johal (2000) suggested that depression and exhaustion in haemopoietic potentials occur under anoxic conditions. The significant decrease in Hb concentration may also be due to either an increase in the rate at which the Hb is destroyed or to a decrease in the rate of Hb synthesis (Reddy and Bashamohideen, 1989).

The WBC counts were observed to have increased slightly in this study. Das et al. (2004) reported that increase in WBC count occurred as a protective response to stress while Adekunle et al. (2007) were of the view that elevation of WBC was due to immune response by the tilapia. Further studies of the differentials showed an increase in monocytes with increase in the concentration of the toxicant. This indicates an increase in phagocytic activities to rid the system of damaged broken down tissues.

CONCLUSION

This study has established that low doses of atrazine could induce anaemia and lymphopoiesis in tilapia. Hence, the need for caution during use by farmers to avoid potential environmental pollution of streams in watershed around their fields.

REFERENCES

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