Ecotoxicity Of Microcystin And Its Biodegradation Products

Microcystin-LR, produced and released by various blue-green algaes, is a cyclic heptapeptide and is reported as a phycotoxins. Microcystin-LR is responsible for the deaths of wild animals, agricultural livestock and caused human health problems in many waterbodies. Many of studies found that MCs have toxicity to both the terrestrial and aquatic organisms. It is reported that MCs have hepatotoxicity, nephrotoxicity, gastrointestinal toxicity, embryotoxicity, immunotoxicity, genotoxicity, cytotoxicity and teratogensis. Previous studies mainly focused on the toxicity of MCs on the exposed individual, however, whether these toxicities from MCs could be transferred to progeny has not been clarified yet. So it is necessary to study the ecotoxicity of MCs.Adda can be produced and accumulated under anaerobic conditions during the biodegradation of MCs. In fact, anaerobic environment exists in natual water, so Adda will be accumulated in the waterbody as the MCLR biodegradated in anaerobic conditions, and it is will cause water pollution. Adda is the essential activity groups for the expression of MCs toxicity, however, the acute toxicity of Adda to mouse (i.p.) is more lower than toxicity of MCLR. Adda ecotoxicity and its impact on the environment have not been studied. So it is necessary to investigate the ecotoxicity of Adda.In present thesis, toxicity of microcystion-LR, possibility of toxicity transferable to progeny of animals and ecotoxicity of Adda were analyzed by used the model organism Caenorhabditis elegans. The main conclsions obtained are listed as follows:1. We study the toxicity of MCLR to Caenorhabditis elegans and their progeny. The results showed that MCLR exposure could decrease reproduction of parental animal of Caenorhabditis elegans, suppress locomotion behavior, increase rate of vulva malformations, reduce lifespan and delay development. It is suggested that MCLR exposure result in multi-biological toxicity to Caenorhabditis elegans and these toxicities could be transferred to the progeny of Caenorhabditis elegans. Although the defects of body length could be recovered in progeny of animals exposed to 1μmol/LMCLR and defects of brood size and head thrash could be recovered in progeny of animals exposed to 0.001μmol/L concentrations MCLR, reproduction and locomotion behavior have still significantly inhibited(P<0.05), moreover rate of vulva malformations and decrease of lifespan both increased. It is suggested that MCLR exposure cause to serious toxicity to Caenorhabditis elegans, and some of toxicities can be transferred to progeny of Caenorhabditis elegans. Moreever, reduction of lifespan and increase of rate of vulva malformations showed even more severe defects. Therefore, MCLR exposure will cause adverse effects to individual and development growth of Caenorhabditis elegans.2. We investigate the toxicity of Adda to Caenorhabditis elegans. The result suggested that Adda exposure could reduce brood size significantly(P<0.05), supress locomotion behavior, decrease lifespan, not lengthen generation time, not significantly effect body length and rate of vulva malformations. The result suggested that although ecotoxicity of Adda is decreased by 50 times, compared with ecotoxicity of MCLR, Adda exposure will change age structure of population, population density and population spatial distribution, for reproduction, locomotion behavior and lifespan could be effected. This will cause adverse effects to individual and development growth of Caenorhabditis elegans, and caused hazard to ecological environment.