Ecotoxicolgical Effects Of Monensin On Earthworm

In recent years, potential toxicity of veterinary drugs on environmental organisms has been paid considerable attentions. Monensin is widely used in animal production as an antiprotozoal, antibacterial, or antifungal agent. However, the ecotoxicological effects of monensin on earthworm have been less concerned. The aim of the study focused on ecotoxicological effects of monensin in individual, biochemical and molecular level by a comprehensive mixture with methods of ecotoxicology, biochemistry and molecular biology. Some biomarkers of earthworm including genetic toxicity, antioxidant enzyme system were also chosen in the study. The information of ecotoxicological effects of monensin on earthworm will be a useful tool for drug risk assessment and risk prediction early. Monensin was considered to be potential risk on soil environmental safety. Results of the research were presented as following:Acute toxic tests of monensin on earthworm (Eisenia fetida) were done with two international standard methods (OECD,1984) including contact filter paper test and artificial soil test. Results showed that the LC50 of monensin on earthworms was 79.322μg·cm-2(48h) and 75.883 mg·kg-1(14d) respectively for contact filter paper test and artificial soil test.The effect of different concentration levels of momesin and abendozole on earthworm growth, survival, production was studied with bass soil test. The results showed that the reproduction of earthworm was significantly inhibited in lower monensin concentration with LOEC 5mg·kg-1 (P<0.05). The growth and survival of earthworm were significantly affected respectively at the monensin concentrations of 25mg·kg-1 and 50 mg·kg-1; The number of cocoon and hatching rate were inhibited significantly with LOEC 5 mg·kg-1. There was a significant dose-response relation between the exposure concentration of monensin and inhibition rate of earthworm growth and reproduction. The parameter of reproduction was more sensitive on monensin exposure.Low concentration albendazole inhibited the reproduction of earthworm significantly with LOEC 5 mg·kg-1 (P<0.05). The growth and survival of earthworm was affected significantly by monensin with LOEC 7mg·kg-1.When the albendazole concentration reached to 10mg·kg-1, the mortality of earthworm was 53%. There was a significant dose-response relationship between the exposure concentration of albendazole and the inhibition rate of earthworm growth and reproduction. The results showed that the toxicity of abendazola is stronger than that of monensin.Four kinds of enzyme activity of superoxide dismutase (SOD), glutathione-sulfurtrans-ferase (GSH-S), acetylcholine esterase (T-CHE) and adenosine-triphosphatase (ATPase) was also observed with the same test. After 21days exposure, monensin affected significantly on the enzymatic activities of SOD,GSH-S,T-CHE and ATPase. And significant dose-response relation between exposure concentration and enzyme activity was observed.The genotoxicity changes of monensin on earthworm coelomocytes were tested with comet assay (single cell gel electrophoresis test, SCGE) The result showed that monensin with high concentration (15,25,50mg·kg-1) could make the DNA of earthworm coelomocytes damaged obviously, which demonstrated that there were genotoxic compounds produced in the degradation process. There was also a significant dose-response relation between the exposure concentration of monensin and DNA damage of earthworm. The activity of enzyme of earthworm and DNA damage level can predict ecotoxicolgical risk as a biomarker as soon as possible.In a word, monensin had direct toxic effects on soil animals and also existed with a potential ecological risk.