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为了探明20-羟基蜕皮甾酮对昆虫蜕皮过程中体壁的表皮层、皮细胞及其细胞器的具体影响过程,本研究利用透射电镜技术研究了20-羟基蜕皮甾酮对舞毒蛾Lymantria dispar(Linnaeus)5龄幼虫体壁超微结构的变化。结果表明,用高浓度20-羟基蜕皮甾酮溶液浸过的白桦叶片饲喂幼虫,处理6h,摄入约400μg20-羟基蜕皮甾酮后,幼虫停止取食;处理12h时表皮细胞顶膜上的微绒毛减少,在皮细胞与旧表皮之间形成蜕皮间隙,旧头壳从幼虫头部脱离;处理24h时蜕皮间隙继续增大,旧表皮与皮细胞进一步分离,新表皮质层开始形成;处理36h时皮细胞顶膜形成较短的微绒毛,胞质区域出现数量较多的电子疏松泡,新表皮由上表皮、外表皮及8层左右内表皮片层组成;处理48h时顶膜与内表皮界限模糊,内表皮继续合成至16层左右;72h时细胞内出现大面积电子疏松泡,内表皮合成至20层左右。处理96h时,与对照组相比,皮细胞细胞器较少,核仁周围出现小部分空白区域,胞质区域内含物减少;虫体发黑缩小,即将死亡;内表皮层数仍旧保持20层左右。对照组幼虫6-96h虫体活跃,正常取食,外部观察及透射电镜结果均未显现蜕皮现象;表皮层由上表皮、外表皮及内表皮组成;皮细胞顶膜微绒毛密度高;表皮细胞分泌活动旺盛,胞质区域细胞界限明显,内含物丰富;细胞器典型而且活跃;内表皮片层随时间不断增加至50层左右。结果提示,外源20-羟基蜕皮甾酮能够导致舞毒蛾5龄幼虫的致死性蜕皮。
In order to find out the specific influence of 20-hydroxyecdysone on the body surface epidermis, dermal cells and organelles in the process of insect molting, we studied the effects of 20-hydroxyecdysone on Lymantria dispar Changes in ultrastructure of body wall of 5th instar larvae. The results showed that the larvae were fed on the leaves of Betula platyphylla infiltrated with high concentrations of 20-hydroxyecdysterone for 6 hours, and the larvae stopped feeding when about 400 μg of 20-hydroxyecdysterone was ingested. After 12 hours of treatment, Microvilli decreased, the skin cells and the old epidermis formed between the molting gap, the old head shell from the larvae head detachment; processing 24h molting gap continues to increase, the old epidermis and skin cells further separation, the new cortical layer began to form; treatment At 36h, the apical membrane of the dermal cells formed shorter microvilli and the cytoplasm appeared more electron-loose bulbs. The new epidermis consisted of upper epidermis, epidermis and 8 layers of inner epidermis. Epidermal boundaries fuzzy, the inner epidermis continue to be synthesized to about 16 layers; 72h when the cells appear large areas of electronic loose bulbs, the inner epidermis synthesis to about 20 layers. Compared with the control group, 96h cells showed fewer organelles, a small amount of blank area around the nucleolus, and decreased contents in the cytoplasm area. The parasites died of blackness and were about to die. The number of inner epidermis remained at 20 layers about. The larvae of control group lasted for 6-96h. The larvae of the control group were active and fed normally. The appearance of the epidermis was composed of the upper epidermis, the epidermis and the inner epidermis. The densities of the epidermal cells Secretion activity, the cytoplasmic cell boundaries obvious, rich in content; organelle is typical and active; within the epidermal parenchyma increasing with time to 50 or so. The results suggest that the exogenous 20-hydroxyecdysterone can cause lethal molting in the 5th instar larvae of Gypsy moths.