除草剂丁草胺对花背蟾蜍胚后早期脑部发育的毒性作用

发布时间：2018-11-10 18:19

【摘要】：目的：通过对花背蟾蜍胚后早期蝌蚪的急慢性毒性实验，我们探讨除草剂丁草胺染毒后对背蟾蜍胚后发育早期蝌蚪的形态学与行为学的改变、脑部神经元形态和数量以及室管膜厚度的改变，从而揭示除草剂丁草胺对花背蟾蜍胚后早期脑部发育的毒性作用，为生态保护工作提供更充实的资料。方法：首先对花背蟾蜍发育至gosner20、gosner25和gosner26期的蝌蚪进行急性染毒，求出各期蝌蚪的LC_(50)及其95%置信区间、安全浓度，并观察记录蝌蚪在行为学和形态学上的变化；接着依照gosner20,25,26期蝌蚪的各自24hLC_(50)浓度对各期蝌蚪进行染毒，24h后从各期取4-5只蝌蚪做脑部石蜡切片，尼氏染色，观察急性染毒后的脑部组织学变化；然后以发育至gosner25期的蝌蚪做为研究对象，以其24h LC_(50)浓度值为基础换算为一系列浓度梯度（24h LC_(50)浓度值的1/5、1/10、1/20、1/50、1/100和1/200）进行慢性染毒，每隔3天记录体重、体长的变化，并取4-5只蝌蚪做脑部石蜡组织切片，尼氏染色观察染毒对花背蟾蜍胚后早期脑部发育的影响。结果：随着发育时间的增加，丁草胺对花背蟾蜍的LC_(50)值逐渐增大。急性染毒对蝌蚪的行为学和形态学均产生了不同程度的毒性作用。慢性染毒过程中，丁草胺对花背蟾蜍胚后早期生长发育造成了明显的滞育影响，体重从第6天、体长从第9天开始染毒组与对照组之间出现了显著性差异。急慢性染毒后蝌蚪脑部神经元形态均未出现明显病理性改变，但在急性染毒24h后，蝌蚪的部分脑区的神经元数量出现了明显减少，在慢性染毒的第3天，花背蟾蜍蝌蚪脑部四个区域（大脑海马区、间脑丘脑区，中脑顶盖区和延髓区）的神经元数量均出现了不同程度的减少，在第6天，染毒组的神经元数量恢复到了与对照组基本相同的水平，而到了第12天，海马区和延髓区的的神经元数量出现了下降，第21天观察，除中脑区外，海马区、间脑区和延髓区染毒组的神经元数量均高出了对照组的水平。在急慢性染毒期间，延髓区神经元数量减少最为显著。同时，在染毒过程中，侧脑室，第三脑室和第四脑室的室管膜厚度均出现了明显的增厚。结论：酰胺类除草剂丁草胺对花背蟾蜍胚后发育早期的蝌蚪具有中等毒性，染毒会对蝌蚪的行为和形态造成改变，并且具有明显的滞育效应，对体重的影响较对体长的影响更为明显；丁草胺染毒对蝌蚪脑部神经元的形态基本上不产生影响，，但染毒会使室管膜的厚度产生保护性的增高。在染毒早期，蝌蚪脑部四个区域神经元数量均出现了减少，尤其对延髓区神经元的影响最为显著，但随后通过蝌蚪自身的适应性调节，神经元的数量又逐步恢复到了正常水平。
[Abstract]:Objective: to investigate the changes of morphology and behavior of tadpoles in the early postembryonic tadpoles of Bufo bufo (Bufo bufo) at the early stage of postembryonic development after exposure to herbicide butachlor. The changes of morphology and number of neurons in the brain and ependymal thickness revealed the toxic effect of herbicide butachlor on the early postembryonic brain development of toad and provided more sufficient data for ecological protection. Methods: tadpoles developed to gosner20,gosner25 and gosner26 stages were exposed to acute toxicity. The LC_ (50) and 95% confidence interval and safe concentration of tadpoles were obtained. The changes in behavior and morphology of tadpoles were observed and recorded. Then the tadpoles of each stage were exposed to the 24 h LC50 concentration of gosner20,25,26. After 24 hours, 4-5 tadpoles were taken from each stage for paraffin section and Nissl staining to observe the changes of brain histology after acute exposure. Then the tadpoles developed to the stage of gosner25 were used as research objects, and their 24 h LC_ (50) concentrations were converted to a series of concentration gradients (1 / 5 / 10 / 10 / 10 / 1 / 20 / 20 / 50 / 100 and 1 / 200 of the concentration of 24 h LC_ (50) for chronic exposure. The changes of body weight and body length were recorded every 3 days, and 4-5 tadpoles were taken as paraffin sections of the brain. Results: with the increase of development time, the LC_ (50) value of butachlor on toad increased gradually. The behavior and morphology of tadpoles were affected by acute exposure. During chronic exposure, butachlor had a significant diapause effect on the growth and development of toad embryo, and there were significant differences in body weight and body length between the control group and the control group from the 6th day and the 9th day. After acute and chronic exposure, no pathological changes were found in the brain neurons of tadpoles, but after 24 hours of acute exposure, the number of neurons in some brain regions of tadpoles decreased significantly, and on the third day of chronic exposure, the number of neurons in some brain regions of tadpoles decreased significantly. The number of neurons in four brain regions (hippocampus, diencephalon, mesencephalic tectum and medulla oblongata) of Bufo bufo tadpole decreased in varying degrees. The number of neurons in the exposed group returned to the same level as that in the control group, but on the 12th day, the number of neurons in the hippocampus and medulla oblongata decreased. The number of neurons in diencephalon and medulla oblongata groups was higher than that in control group. During acute and chronic exposure, the number of neurons in the medulla oblongata decreased most significantly. At the same time, the ependymal thickness of lateral ventricle, third ventricle and fourth ventricle were obviously thickened. Conclusion: butachlor has moderate toxicity to the tadpoles in the early postembryonic development of Bufo bufo, which can change the behavior and morphology of the tadpoles, and has obvious diapause effect. The effect on body weight is more obvious than on body length. Butachlor exposure had no effect on the morphology of brain neurons of tadpoles, but the thickness of ependymal membrane was increased by exposure to butachlor. In the early stage of exposure, the number of neurons in the four regions of tadpole brain decreased, especially in the medulla oblongata area, but the number of neurons gradually returned to normal level through the adaptive regulation of tadpole itself.
【学位授予单位】：沈阳师范大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R114

【相似文献】