オオミジンコ

In the present study, 48-hour median effective concentrations (48-h EC50s) were evaluated for 22 chemicals selected from among 46 agricultural chemicals which are thought to be endocrine-disrupting chemicals and for 8 non-agricultural chemicals using the Daphnia magna acute immobilization test (OECD guideline 202). Furthermore, lowestobserved-effect concentrations (LOECs) were evaluated for Endosulfan (Benzoepin), a strongly toxicant agricultural chemical to Crustacea and for 8 of the chemicals described above using the D. magna reproduction test (OECD guideline 211). On the basis of the 48-h EC50s and LOECs for the chemicals evaluated in the present study, problems regarding the sensitivity of tests using Daphnia sp. in comparison with 3-h LC50s that have been reported elsewhere (see references), are discussed. The results are as follows. 1) The ratios of 3-h LC50/48-h EC50 for 15 agricultural chemicals were higher than 6.6. With respect to DDT, the ratio was higher than 22,471. These results indicate that the acute immobilization test is a more useful test than the 3-h median lethal test as a toxicant evaluation test for agricultural chemicals. 2) The ratios of 48-h EC50/LOEC for Endosulfan and 8 of the chemicals were high, ranging from 1.7 to 58. Accordingly, the reproduction test is a more sensitive test than the acute immobilization test. In respect of the toxicant evaluation of chemicals uSing Daphnia sp., it would be best to evaluate the toxicity using the reproduction test which is a long-term toxicity test. On the other hand, it is obviously difficult to obtain data on many chemicals instantly using the reproduction test because the test requires such a large amount of time and labor. lt is however possible to predict the results of the reproduction test from the results of the acute immobilization test because a strong correlation clearly exists between these two tests with regard to the toxicant evaluation of chemicals. Accordingly, the acute immobilization test is considered suitable as a toxicant evaluation test for agricultural chemicals.