敌百虫对中国林蛙蝌蚪生长发育的毒性效应

为评价水域环境中敌百虫(trichlorfon)污染对两栖类幼体的急性毒性,将中国林蛙(Rana chensinensis)28～29期(Gos-ner)蝌蚪分别暴露于10～30 mg· L-1敌百虫5个不同浓度的水体中,分别在24、48、72和96 h统计蝌蚪的死亡率,计算半致死浓度(LC50).结果显示,暴露24、48、72和96 h,敌百虫对蝌蚪的LC50分别为14250±3.23、49.19±128、25.68±2.04、1555±1.93 mg·L-1,安全浓度(SC)为156±0.19 mg· L-1.蝌蚪中毒后尾部多呈弯曲状,仰翻,外观浮肿.对死亡蝌蚪的解剖表明,其鳃腔内充水,内鳃萎缩,肝脏、肠管和肾脏呈灰白色.另外,将28～29期蝌蚪分别暴露于0.2 ～ 2.0 mg·L-1敌百虫4个不同浓度的水体中进行慢性暴露实验,检测蝌蚪暴露28和42 d时的体重和体长以及75％个体变态所需的时间.结果表明,蝌蚪在低剂量敌百虫水体中持续暴露,其生长发育受到明显抑制,并可导致蝌蚪身体扭曲、尾部强直性弯曲等畸型发生,蝌蚪的死亡率显著增高,作用强度呈现剂量和时间的累积效应.慢性暴露实验证明SC以下的敌百虫水体仍威胁着蝌蚪的生存.

Toxicity Effect of Trichlorfon on the Growth and Development of Rana chensinensis Tadpoles

In order to evaluate the acute toxicity of trichlorfon on amphibian larvae, the Rana chensinensis tadpoles at the stage 28-29 were exposed to the water contaminated by 10-30 mg·L^-1 trichlorfon, the death rate of tadpoles were examined for 24, 48, 72 and 96 h respectively, and the median lethal concentration(LC₅₀) of trichlorfon on tadpoles were determined. The results showed that the LC₅₀ of trichlorfon for 24, 48, 72 and 96 h was 142.50±3.23, 49.19±1.28, 25.68±2.04 and 15.55±1.93 mg·L^-1, and the safe concentration (SC) was 1.56±0.19 mg·L^-1. The acute toxicity of trichlorfon could cause the tail bent, the whole body turned over and the exterior puffiness and expand. Dissection of the death tadpoles exhibited that the toxicity of trichlorfon causing the gill cavity water-filling, gill atrophy and the liver, intestine and kidney were off-white in color. In another experiment, the stage 28-29 tadpoles were challenged with different doses of trichlorfon that under SC to investigate the chronic toxicity of trichlorfon. The main items which covered body length and body weight were detected with 28 and 42 d of exposure. The time needed for 75% individual metamorphosis were also recorded. Over long exposure periods to low-dosage trichlorfon less than SC led to teratogenicity, such as the body distortion and ankylosing benting of the tail, which could restrain the growth and development of the tadpoles. The cumulative mortiality of tadpoles directly increased with ambient trichlorfon concentrations in the range. The effect had a dose-effect relationship with the trichlorfon concentration and time accumulation.