Study On Safety Evaluation Of Pyraclostrobin To Zebrafish

Pyraclostrobin is one of the methoxyl acrylic ester pesticides with the highest activity. For characteristics of broad spectrum, high efficience and friendly to terrestrial environment, pyraclostrobin has perfect development potential. Environmental issues caused by pyraclostrobin will certainly become a focused issue of the society, while present attention was just focused on its environmental residue, and less studies was conducted on its toxic effect on aquatic organism. Acute toxicity test of pyraclostrobin to adult fish and embryo of zebrafish were conducted in this paper, on this basis, sub-lethal toxicity test to adult fish and embryo of zebrafish were also carried, and safety of pyraclostrobin to adult fish and embryo of zebrafish was comprehensively assessed. The aim of the study was to reduce environmental risk of pyraclostrobin application, at the same time, the study would provide scientific basis for intelligent use of methoxyl acrylic ester pesticides and its environmental security management. The results were as follows:On the basis of test method provided by Chemical pesticide environmental safety evaluation test guidelines, acute toxicity of pyraclostrobin to adult fish and embryo of zebrafish was conducted. The results showed that LC50 (96h) value of pyraclostrobin to adult fish and embryo of zebrafish were respectivety 635 ug/L and 92.7 ug/L. The acute toxicity grade of pyraclostrobin to adult fish was high toxic, and to embryo of zebrafish was highly toxic. Toxic symptoms such as slow movement, gills bleeding, unbalance of swimming were caused by pyraclostrobin, at the same time, pyraclostrobin would lead to yolk sac swelling, pericardium swelling, yolk sac bleeding and spine malformation of zebrafish embryo or fry.Toxic effect test of pyraclostrobin to adult fish of zebrafish was carried. One the basis of acute toxicity test, sub-chronic toxicity test was conducted. Toxic effect of pyraclostrobin to growth and development and antioxidant system of adult zebrafish were determined under sublethal concentration. The results showed that pyraclostrobin had certain inhibiting effect on weight and body length of zebrafish. At concentration of 50μg/L, pyraclostrobin had significant inhibiting effect on growth and development of zebrafish, and favourable dose-effect relationship existed between pyraclostrobin exposure concentration and weight of zebrafish. Pyraclostrobin had also certain effect on antioxidant system of adult zebrafish. As the extension of exposure time, SOD and CAT activity showed a trend of earlier rising and later reducing. GST activity showed different degree of reduce after pyraclostrobin exposure. As increase of pyraclostrobin exposure concentration, SOD, CAT and GST activity all reduced significantly. After exposure to pyraclostrobin for 14 d, obvious dose-effect relationship existed between SOD, CAT, GST activity and pyraclostrobin concentration.Toxic effect test of pyraclostrobin to zebrafish embryo was carried. On the basis of embryonic development acute toxicity test, toxic test at yolk sac absorb stage of zebrafish was conducted. The results showed that pyraclostrobin had obvious effect on embryo hatch of zebrafish. As increase of pyraclostrobin exposure concentration, mortality rate of zebrafish rised and hatching rate significantly decreased. When zebrafish embryo developed for 24hpf(hour past fertilization), pyraclostrobin had no significant effect on autokinetic movement frequency in 1 minute, that is to say pyraclostrobin had little effect on neurobehavior of zebrafish at initial stage embryonic development. While pyraclostrobin had significant toxic effect on embryonic development of zebrafish. At pyraclostrobin concentration of 25.6μg a.i./L and 41.0μg a.i./L, symptoms such as pericardium swelling, yolk sac swelling, and bleeding appeared in zebrafish embryo, and heart rate in 10s was significantlt lower than control. While malformation effect disappeared when embryo hatched. Pyraclostrobin had significant effect on embryonic development of zebrafish when at exposure concentration of 65.5μg a.i./L and 105 μg a.i./L. Heart rate of 48 hpf embryo significantly decreased, and embryonic development was inhibited. Symptoms such as no obvious colour of embryo eyes, yolk sac swelling,yolk sac bleeding, cyrtosis appeared in zebrafish embryo. Toxic effect significantly increased with increase of pyraclostrobin concentration.