柑橘大实蝇产卵器的超微结构观察(双翅目:实蝇科)

Ultrastructural observation of ovipositor of Bactrocera minax(Diptera:Tephritidae)

柑橘大实蝇Bactrocera minax(Enderlein),是柑橘的重要害虫。本文基于光学显微镜、扫描电镜、石蜡切片和透射电镜观察,对柑橘大实蝇的产卵器形态结构进行研究。结果表明,柑橘大实蝇产卵器由产卵器基节、翻缩膜和产卵针3部分组成,翻缩膜是浅黄色的柔软的细长管状结构,又分为骨化带、骨化环和膜质部3部分。骨化带表面有4条褐色的、纵向的、柔软的离散带。骨化环和膜质部表面存在小齿和无齿两种角质化鳞片,鳞片的一端与表皮连接,另外一端处于自由状态,鳞片以覆瓦状包围在骨化环和膜质部表面。骨化带和骨化环弯曲程度极低,而膜质部弯曲程度较大。产卵针由1块背片和2块腹片组成,2块腹片之间、背片与腹片之间与可折叠弯曲的柔性角质层连接。其背片两内侧均存在1个未封闭的圆环,其内部有肌肉(背腹肌)、气管、输卵管和直肠等组织或器官。产卵器上有毛形、腔锥形和钟形3种类型感受器。在产卵器收缩时,首先产卵针折叠在翻缩膜内,然后再一起折叠在基节内。因此,在成虫休息时,产卵器形成了产卵针(内层)、翻缩膜(中间层)和基节(外层)3个腹节的套叠。柑橘大实蝇的产卵器是伪产卵器,其结构或组织经过进化,从而适应其伪产卵器的外翻、弯曲、收缩折叠运动机制。本研究为理解昆虫进化和多样性,以及昆虫的产卵、交配和代谢物排泄等行为机制提供新的例证。

Chinese citrus fly,Bactrocera minax(Enderlein)(Diptera:Tephritidae),is an important pest of citrus crops.The morphology and structure of the ovipositor of B.minax were observed on optical microscopy,scanning electron microscope(SEM),paraffin section,and transmission electron microscopy(TEM).The results showed that the ovipositor of B.minax was composed of oviscape,eversible membrane,and aculeus.The eversible membrane was a soft and long tubular structure with light yellow color,which was divided into sclerotized belt,sclerotized ring,and membranous section.The surface of the sclerotized belt had 4 brown,longitudinal,and soft discrete bands.Two kinds of cutinized scales with denticulations and without denticulations existed on the surfaces of the sclerotized ring and membranous section.One end of the scale was connected with the epidermis,and the other end was in a free state.Scales imbricate around the surface of the sclerotized ring and membranous section.The sclerotized belt and sclerotized ring with an extremely low degree of curvature,and the membranous part with a relatively large degree of curvature.The aculeus was composed of a tergite and two sternites,and a flexible cuticle that can be bent and folded is connected between the two sternites and between the tergite and the sternite.An unclosed ring was found on both inner sides of the tergite of the aculeus.In addition,tissues or organs such as muscles(tergosternite muscle),trachea,oviduct,and rectum were located inside the aculeus.Three types of sensillum were distributed on the ovipositor:trichoid sensilla,campaniform sensilla,and coeloconic sensilla.When the aculeus contracts,the aculeus first is folded in the eversible membrane and then folded together in the oviscape,Therefore,when the adults rested,the ovipositor formed a folding of three abdominal segments of the aculeus(inner layer),eversible membrane(middle layer)and oviscape(outer layer).The ovipositor of B.minax was a pseudo ovipositor,and its structure or tissue had evolved to adapt to the eversion,bending,contraction,and folding motion mechanism of the pseudo ovipositor.This study will provide new evidence for understanding insect evolution and diversity,as well as insect behavioral mechanisms such as oviposition,mating,and metabolite excretion.