Of Four Insecticides On Daphnia Magna (d.magna) Chronic Toxicity

Insecticides entere the aquatic environment and impose side effects daphnia community so as to deteriorate aquatic environmet consequently. In this paper two-generation reproduction toxicity of fenvalerate, a-cypermethrin, chlorpyrifos, and triazophos was tested in a 21d period with water flea, Daphnia magna,. The toxicity indicator included Longevity, Body length, Days to first brood, Days to first pregnancy, Number of youth per female, Intrinsic rate of natural increase (r), and Number of broods per female. Accordingly, the dose-response relations and relations between the chronic responses and enzyme levels were investigated. The purpose for investigating chronic responses-enzyme level relations was to predict early cotamination of pesticides in the water environment. The results obtained are as follows:48-LC50 value of fenvalerate and a-cypermethrin for D. magna were 0.61 (0.47-0.75) g/L and 0.55 (0.44-0.66) ug/L respectively. The highest non-effective concentration (NOEC) and the lowest effective concentration (LOEC), as counted with Number of youth per female, covered the range of 0.005-0.01 g/L. 7d IC50, in terms of the Body length, were 0.19 g/L and 0.17 g/L respectively, while the twenty-first day IC50 were 0.22 g/L and 0.205 g/L respectively.For fenvalerate and a-cypermethrin, indicators such as Number of youth per female, Body length and r were more sensitive than another indicators in the 21 d toxicity test. The Days to first brood and Days to first pregnancy were delayed by higher concentration of fenvalerate and a-cypermethrin. The growth and fecundity were also restrained. As a result r is lower than the controls. The phenomenon that AChE and BChE activity of Daphnia magna were higher than controls might result from stimulating actions of pesticides at sub-lethal concetrations.In the recovery test, the body length and reproduction index, such as number of young per female, were reduced for F1 (1st) and F1 (3rd) individuals if the parents (F0) exposed to fenvalerate and a-cypermethrin. However all the toxicity indicator of F1 (3rd) individualswere able to restore and the values were higher than those for F0 and F1 (1st) generation of D. magna during a recovery period of 21 days.In the acute test for D. magna 48-LCso values for triazophos and chlorpyrifos were 13.81( 12.73~14.87)g/L and 7.77(6.59-8.95 )g/L respectively. 48-IC50 values for AChE of D. magna were 5.98 (5.89-6.07) g/Land 8.99 (7.76-10.22) g/L respectively, the 48-IC50 values for BChE of Daphnia magna were 7.88 (6.83, 8.93) g/L and 3.74 (2.66, 4.82) ug/L respectively. So for triazophos and chlorpyrifos 50% ChE inhibiton was more sensitive to than 50% lethal concetration, and BChE was more sensitive than AChE. NOEC and LOEC, as counted with such a indicator as Number of young per female, were measured to be 0.05-0.1 g/L.In studies with aquatic invertebrate, D. magna, estinates for the AChE and BChE inhibition at the lethal LC50 ranged from 85-99%. The reproduce reduced rate of D. magna covered from 20-42%, when AChE and BChE activity inhibition value of D. magna exposed to sub-concetration triazophos and chlorpyrifos derived from 10-55% or inducement 15~74%,respectively. Accordingly, the progress trend of aquatic invertebrates community, water flea exposed to sub-dose anti-ChEs would be predicted by using AChE and BChE inhibition.