Substrate affinity and insecticide sensitivity of acetylcholinesterase (AChE) from Daphnia magna S., Bombyx mori L., Musca domestica L., Myzus persicae S., Anguilla anguilla L., Cyprinus carpio L., Oryzias latipes T.&S., Homo sapiens L., Bos taurus L. were tested. The Km values of M. domestica AChE to acetylthiocholine (ATCh), propionylthiocholine (PTCh), butyrylthiocholine (BTCh) were 57.3 μM, 13.4 μM and 85.9 μM respectively, which were lower than those of A. anguilla, C. carpio, O. latipes, H. sapiens and B. taurus. In nontarget organisms, the I50 values of AChE to fenitroxon and DDVP were 1.5×10-6 M~7.8×10-5 M and 2.4×10-6 M~1.1×10-4 M respectively, thus they have lower sensitivity compared with M. domestica. The I50 value of M. persicae AChE to pirimicarb was 1.3×10-8 M, which was higher sensitivity compared with other test animals except D. magna. The I50 values of D. magna AChE to fenitroxon, DDVP, carbaryl, eserine, pirimicarb were 5.2×10-10 M~2.1×10-8 M, which were higher sensitivity compared with the other test animals used for this study. cDNA of Daphnia magna AChE precursor was sequenced and compared with those of Musca domestica, Drosophila melanogaster and Torpedo californica.

There are concerns that chemical residues could harm the consumer on the environment, although 50 to 80% of the crops would be destroyed by pests and others without agrochemicals. Environmental fate and ecotoxicity studies are usually carried out to assess the impact on the human and the environment. A comparision of the Daphnia magnia and Simocephalus mixtus toxicity was performed to study the relative sensitivities and discrimination abilities to agriculture chemicals. The species of Simocephalus mixtus was more sensitive to agriculture chemicals than Daphnia magnia. Simocephalus mixtus was approved to be a water flea in determining insecticide and pesticide toxicity by heartbeat rate in a consistency and repeatability. The order of acute toxicity to water flea Daphnia magnia for ecotoxicity test was carbaryl>benomyl>amtirole with both Daphnia magnia and Simocephalus mixtus. The heartbeat pattern after the exposure to agrochemicals was different from that of exposure to heavy metals. Agrochemical leathal concentration test with heartbeat rate measurement was found to be more appropriate than inhibition concentration test with respect to toxicological endpoint.