Correlation between herbicide contamination and effects on reproductive system of cyprinid fish Puntioplites proctozysron in Nan river, Wiangsa district, Nan province

Abstract

The use of herbicides, especially paraquat, glyphosate and atrazine in Nan Province, northern part of Thailand is dramatically increased. Nan River nearby agricultural areas is thus susceptible to contamination by the herbicide runoff. Aquatic animals are probably at risk of affecting by the contamination. In this study, Puntioplites proctozysron was used as a sentinel species to monitor the effects of herbicide contamination in Nan River. The fish were collected from the river nearby agricultural areas in San Sub-district, Wiang Sa District, Nan Province in rainy season (July and October 2010) and dry season (January and April 2011). The analyses of herbicide residues revealed detectable levels of atrazine in water (ND-0.15 mg/L), sediment (ND-0.24 mg/Kg) and fish gonads (ND-0.15 µg/g), whereas glyphosate was detected only in the fish gonad samples (1.20-2.01 ng/g). The analyses of condition factor (CF) and gonadosomatic index (GSI) showed that, CF of both sexes was significantly higher in January 2011. GSI of male fish was significantly higher in January 2011, while GSI of female fish was significantly higher in July 2011. Spearman's correlation between atrazine concentrations and general health indices revealed the positive correlation in CF and GSI for male fish and negative correlation in GSI for female fish. However, the link between herbicide contamination to CF and GSI of P. proctozysron did not clearly exhibited. These trends were alternatively explained by seasonal variation, rather than effect of herbicide contamination alone. The evaluation of herbicide effect in cellular level was done by histopathological observation of gonadal tissue. The testicular atrophy, testicular degeneration, degeneration of Leydig and Sertoli cells, asynchronus development, karyorhexis, karyolysis, germ cell atrophy, germ cell hypertrophy, eosinophilic cytoplasm was observed in testicular tissue of the male fish. Ovarian degeneration, oocyte hyperplasia, atresia in oogonia, atresia in previtellogenic oocytes, vacuolar degeneration and follicular hyperplasia were found in ovarian tissues of the female fish. Atrazine concentrations in gonadal tissues showed significantly positive correlation with testicular atrophy and degeneration of Leydig cells in male fish and atresia in previtellogenic oocyte and vacuolar degeneration in female fish. According to the results, it is concluded that the atrazine contamination in Nan River may involved with several histopathological alterations in the fish gonadal tissue, which may lead to further reproductive problems in the fish population. The results also suggested that Leydig cells in male fish and oocytes at early developmental stage in female fish are most susceptible. Histopathological alterations detected here have proven that P. proctozysron could be considered as a good sentinel species in monitoring study of the herbicide contamination in the river.