小菜蛾成虫下唇须感器的超微结构及其神经元中枢投射

Ultrastructure of sensilla on labial palps and the central projection of their sensory neurons in Plutella xylostella (Lepidoptera: Plutellidae) adults

【目的】明确小菜蛾Plutella xylostella成虫下唇须感器的形态结构及感器神经元的投射。【方法】利用光学显微镜观察和扫描电子显微镜观察下唇须结构和感器类型,利用神经回填技术和激光共聚焦显微镜观察下唇须感器神经元在脑部的投射。【结果】小菜蛾成虫下唇须共3节,其上存在Böhm氏鬃毛、钟形感器、鳞形感器、锥形感器、微毛形感器5种不同类型的感器和一个陷窝器结构。Böhm氏鬃毛短小尖细,钟形感器形如顶部凹陷的圆帽,两种感器均分布于下唇须第1节,且大小上均无雌雄二型差异;鳞形感器形同柳叶,锥形感器粗而直,均散生于下唇须的第2和3节,两种感器在大小上均存在雌雄二型差异,其中雌性的鳞形感器显著大于雄性的,根据其雌雄二型差异现象推测雌蛾的鳞形感器可能与感受寄主植物挥发物有关;下唇须第3节中上部具有一个圆形陷窝器结构,雄虫的陷窝器内径为5.68±0.33μm,雌虫的为6.03±0.23μm,雌雄间无显著性差异;凹坑内长有表面光滑的微毛形感器。小菜蛾下唇须感器神经元主要投射于脑部咽下神经节、每个触角叶的下唇须陷窝器神经纤维球和腹神经索3条通路。【结论】阐明了小菜蛾下唇须感器的类型、分布和形态特征及其感器神经元在脑部的投射形态,为深入了解小菜蛾下唇须感器的生理和功能奠定了基础。

【Aim】 This study aims to characterize the morphology of sensilla on labial palps and the central projection of their sensory neurons in adults of the diamondback moth, Plutella xylostella .【Methods】 The structures of labial palps and their sensilla type were observed under light and scanning electron microscopy, and the central projection of the sensory neurons of sensilla on labial palps were observed by using neuronal backfills and confocal microscope.【Results】 The labial palp of P. xylostella adults consists of three segments, on which there are five types of sensilla, including B hm bristles, sensilla campaniformia, sensilla squamiformia, sensilla basiconica, and microtrichia, and a labial-palp pit organ (LPO). B hm bristles are spine-like, sensilla campaniformia have circular dome surrounded by a cuticular rim, and both of the two sensilla were found only on the 1st segment of labial palp, without significant differences in size between sexes. Sensilla squamiformia are willow leaf-like, sensilla basiconica are thick and straight, and both are scattered on the 2nd and 3rd segments, with significant differences in size between sexes. Sensilla squamiformia in females are significantly larger than those in males, and this sexual dimorphism suggests that this type of sensilla of female are likely associated with sensing of host plant odours. The LPO is located in the middle and upper part of the 3rd palpus segment, and the width of the pit is 5.68±0.33 μm in males and 6.03±0.23 μm in females, without significant difference between sexes. Many microtrichia with smooth surface are located in inner pit. The sensory neurons on the labial palp project to the subesophageal ganglion, labial pit organ glomerulus (LPOG) in each antennal lobe and the ventral nerve cord.【Conclusion】 The morphology of sensilla on labial palps and the central projection of their sensory neurons in P. xylostella adults have been illustrated in this study, providing a basis for further investigation on their physiology and function.