Toxic Effects Of Methamidophos And Cypermethrin On Macrobrachium Nipponense

The toxic effects of methamidophos and cypermethrin on the freshwater prawn, Macrobrachium nipponense, were investigated for the first time. Some physiological indexes were measured in experimental regime,including LCso>oxygen consumption rate,ammonia-N excretion rate,AchE and Na=+,K+-ATPase activitiesO2 and some antioxidant enzymes (such as superoxide dismutase,catalase,glutathione peroxidase, glutathione S-transferase and glutathione reductase) activities. Each experimental index was synthesized,and toxic effects of two pesticides on M.nipponense were analysed.This research would provide the scientific basis for evaluating pesticides to the safety of aquatic animals.Firstly,the acute toxicity tests of methamidophos and cypermethrin were made respectively,the LC50 of each pesticide was measured.Secondly,six treatments were putted up in the range of 0-LC50,and the experiment lasted for 24h.,then each experimental index were measured.The results were as follows.The 96LC50 of methamidophos was 3.00mg/Liand the 96LC50 of cypermethrin was 157ng/L.It was showed that cypermethrin was more poisonous to M. nipponense than methamidophos.With the increasing concentrations of methamidophos, the oxygen consumption rate was increased,but the ammonia-N excretion rate was decreased.When prawns were exposed to high cypermethrin concentrations,both of the oxygen consumption rate and ammonia-N excretion rate were decreased.It was showed that the prawn has different mode to adapt the toxic effect on the respiration metabolism of M.nipponense.AChE and Na+,K+-ATPase activities were inhibited by methamidophos and cypermethrin. Na+,K+-ATPase activities of prawns in highest concentration of methamidophos were the same as those in cypermethrin.But the inhibitory rate of AChE activities of prawns exposed to methamidophos were higher significantly than thoseexposed to cypermethrin.Methamidophos and cypermethrin led to higher O2 value,but the alterations of activities of antioxidant enzymes were different.With the effects of methamidophos, SOD activities of the prawns increased in six concentrations,but the others increased in lower concentrations and decreased in higher concentrations.correspondingly all of the antionxidant enzymes activities of prawns exposed to cypermethrin deceased significantly.lt was showed that cypermethrin was more poisonous on antioxidant enzymes of M.nipponense than methamidophos.