斑蝥素对小菜蛾体壁组织结构的影响

为探究昆虫天然产物斑蝥素(cantharitin,CTD)对鳞翅目昆虫小菜蛾Plutella xylostella(L.)的触杀机制,利用透射电子显微镜观察了该物质处理小菜蛾4龄幼虫体壁组织结构的变化。斑蝥素亚致死剂量0.15μg/头和半致死剂量0.3μg/头点滴处理试虫前胸背板,中毒试虫反映结果类似。处理12h后中毒试虫虫体发黑,陆续死亡。处理12h后,体壁细胞细胞核固缩并且边极化,线粒体扭曲,内脊模糊出现空泡化,线粒体和粗面内质网数量下降;处理24h后,体壁细胞出现的类似处理12h后的症状,且症状更为明显。结果表明CTD对小菜蛾体壁表皮层组织结构无显著破坏作用,但对体壁细胞有明显的致毒作用。

Effect of cantharidin on the integument structure of Plutella xylostella

To investigate the contact toxicity of the natural insect product cantharidin（C10H12O4,CTD） against a Lepidopteran insect,the diamondback moth Plutella xylostella（L.） ,transmission electron microscope（TEM） images of P.xylostella larvae were observed at different times after treatment with CTD.Exposure to a sublethal dose of 0.15 μg/larva and a medial lethal dose of 0.3 μg/larva for 12 h and 24 h by topical application to the pronotum gave similar results;larvaes’ bodies became dark and they died 12 h after treatment.TEM images of the epidermal cells of treated larvae showed that cell nuclei had aggregated,mitochondria had become distorted with mitochondrial cristae and the mitochondria had become blurred and vacuolizated.The quantity of mitochondria and rough endoplasmic reticulum（RER） declined 12 h after CTD treatment.These phenomena were also evident 24 h after CTD treatment.These results indicate that CTD did not destroy the cuticle layers but damaged epidermal cells in the insects’ integument.