Application of an amphibian (Silurana tropicalis) metamorphosis assay to the testing of the chronic toxicity of three rice paddy herbicides: Simetryn, mefenacet, and thiobencarb
Application of an amphibian (Silurana tropicalis) metamorphosis assay to the testing of the chronic toxicity of three rice paddy herbicides: Simetryn, mefenacet, and thiobencarb
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应用两栖动物（热带鲶）变态试验测定西草净、苯噻草胺和硫苯威三种水稻除草剂的慢性毒性
DOI：
10.1016/j.ecoenv.2013.03.023
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发表时间：
2013
影响因子：
6.8
通讯作者：
and Yoichi Kamata
中科院分区：
文献类型：
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作者：
Masahiro Saka;Noriko Tada;and Yoichi Kamata
我们用两栖动物(热带森林志)变态试验(在单独暴露系统下进行了为期28天的半静态试验)检测了三种水稻除草剂(灭草净、灭草净和硫菌威)的慢性毒性。每种除草剂在两种浓度下(先前报道的96小时LC_(50)值的1/100和1/10)进行形态测量、重量测量和甲状腺组织学终点测试。在两个试验浓度(0.04和0.40 mg/L)下，西美特林对小蝌蚪的生长发育都有显著的抑制作用，表现为全身长和后肢长显著缩短，湿体质量变小，发育阶段延迟。然而，在暴露于西美替林的蝌蚪的甲状腺中没有观察到明显的组织病理学。这些结果表明，西美替林可以作为化学应激源，在不破坏甲状腺功能的情况下延缓蝌蚪的生长和发育，即使在96小时LC_(50)值的1/100。此外，暴露于0.40 mg/L西美替林的蝌蚪在尾部附近可见脊柱侧弯，发病率极高(7/30=23.3%)。因此，西米替林也可以作为致畸剂，在96小时半数致死量的1/10处诱发轴畸形。在暴露的28天中，甲草胺(0.03和0.30 mg/L)和硫菌威(0.008和0.080 mg/L)都没有引起任何异常，尽管在溶液更新前的测试浓度从第14天开始下降到标称浓度的近50%。由于西米替林的检测浓度可能出现在稻田水中，因此西米替林可能会对稻田水中的野生无尾目蝌蚪产生不利影响。
We examined the chronic toxicity of three rice paddy herbicides (simetryn, mefenacet, and thiobencarb) using an amphibian (Silurana tropicalis) metamorphosis assay (a 28-day semistatic test under an individual-separated exposure system). Each herbicide was tested at two concentrations (1/100 and 1/10 of the 96-h LC50 value reported previously) with morphometric, gravimetric, and thyroid-histological endpoints. Simetryn caused significant retardation in growth and development at both test concentrations (0.04 and 0.40mg/L), as indicated by significantly shorter total body lengths and hind limb lengths, smaller wet body masses, and delayed developmental stages compared to those observed in the control tadpoles. However, no clear histopathology was observed in the thyroid glands of the tadpoles exposed to simetryn. These results suggest that simetryn can act as a chemical stressor retarding tadpole growth and development without disrupting thyroid functions, even at 1/100 of the 96-h LC50 value. In addition, scoliosis near the tail base was observed in the tadpoles exposed to 0.40mg/L of simetryn at a significantly high incidence (7/30=23.3%). Therefore, simetryn can also act as a teratogen inducing axial malformations at 1/10 of the 96-h LC50 value. During the 28 days of exposure, neither mefenacet (0.03 and 0.30mg/L) nor thiobencarb (0.008 and 0.080mg/L) induced any abnormalities, although the test concentrations measured immediately before the solution renewals decreased to nearly 50 percent of the nominal concentrations since day 14. Because the concentrations tested for simetryn are likely to occur in paddy water, wild anuran tadpoles in paddy water may therefore be adversely impacted by simetryn.