Preliminary Study Of Endocrine Disrupting Effects Of Three Pesticides On Rare Minnow

In this study, we discussed the embryology and histopathology of rare minnow, and the toxicology of three pesticides respectively (avermectin, ethofenprox and chlorpyrifos) on embryos, larval fish, juvenile fish and adult fish. According to the draft of fish embryo toxicity test of OECD test guideline, we observed the toxicological effects of the three pesticides on embryos. According to the OECD test guideline204and OECD guidance document123, we study the histopathological effects of the three pesticides on rare minnow gonads.The results of fish embryo toxicity test showed that the sensitivity of embryos to these three pesticides was less than other life stages of rare minnow (larvae, juvenile and adult fish). The hatching of embryos was inhibited by avermectin, and malformations phenomenon of spine curvature was also being obeservated. The embryos appeared pericardial sac edema and spine curvature when exposured in ethofenprox. The embryo toxicity showed a dose-effect and time-effect relationship when exposured in chlorpyrifos. It also can lead to some obvious teratogenic effects such as:the stretching failure of embryonic yolk sac, curvature of the spine or tail, as well as the pericardial sac edema. By comparing toxic effects of the three pesticides with embryos, larvae, juveniles and adult fish of rare minnow, the toxic of three pesticides on larval, juvenile and adult fish are all highly toxic. Adult fish is the most sensitive, followed by the larvae, juveniles and embryos.Histopathological observation was carried on immediately after14days’ prolonged toxicity test. Picture analysis was carried on for observing every test fish of three replicates of each treatment group. The results showed that the increasing proportion of the spermatogonia proportion on male rare minnow testis in each treatment group of avermectin was along with increasing concentration, but there was not an impact on development synchronicity of gonadal. It was also can be observed that male rare minnow gonad was inhibited by avermectin and the development of testicular was blocked or inhibited. No changes of ethofenprox was observed in all treatment groups. It was also could be observed that the increased spermatogonia proportion of male fish in all treatment groups of chlorpyrifos.In addition, the changes of the body length and weight of rare minnow was analysised after14days’ prolonged toxicity tests. The results of avermectin shows that fish body weight and body length were decreased in the high concentration (0.004-0.002mg/L) compared to the control group. But the opposite phenomenon occurs at low concentrations. The fish body weight of high concentration group of ethofenprox (0.022-0.011mg/L) was increased compared to control group whereas low concentrations did not change significantly. The fish body length of all treatment group of chlorpyrifos were less than control and solvent control, and the fish body length and weight appeared gradually reduced with concentration increasing.