中华按蚊各发育阶段形态特征的电镜扫描观察

Scanning electron microscopic(SEM)observations on the developmental morphology of Anopheles sinensis(Anophelinae:Culicidae)

【目的】中华按蚊Anopheles sinensis Wiedemann是我国最主要的传疟媒介之一,本研究基于实验室饲养的中华按蚊,采用电镜扫描技术观察了中华按蚊不同发育阶段的形态学特征,对蚊虫的形态学、生长发育和基础生物学等的研究具有参考价值。【方法】配置1%锇酸、6%戊二醛等试剂,结合不同浓度的乙醇脱水和叔丁醇真空冷冻干燥技术制备了幼虫、蛹和成虫的电镜样品,使用日立SU3500扫描电子显微镜对其各个发育时期具有重要分类和鉴定意义的形态特征进行观察和描述。【结果】中华按蚊成蚊雌雄个体差异不大,喙与触须均接近等长。雄成蚊触角末端膨大弯曲,触须呈马尾状,梗节呈中间凹陷的圆饼状,腹部末端的尾器有一对钳状抱肢;雌成蚊喙细长,上颚和下颚均有锯齿,有利于刺破皮肤吸食血液,梗节饱满呈球状,腹部末端的尾器为一对向内弯曲的尾须,明显短于雄性的钳状抱肢。电镜下中华按蚊蛹整体呈蝌蚪状,呼吸管位于头部,开口呈锐角三角形,管缘部位有一圈较为平滑整齐的钝圆齿特征;尾鳍为两瓣,呈扇形,雄性蛹期的外生殖器明显较雌性长。4龄幼虫胸腹闭合连接,头部触角上有数量众多刺状感受器,腹部第8节末端背面有气门器。电镜下中华按蚊卵整体呈船形,船面较其它蚊种大,表面均匀分布有细粒状的小突起,大多数分布呈现六边形的花纹结构,精孔区位于卵背面两端,精孔扁平凹陷。【结论】中华按蚊各个发育时期电镜扫描的超微形态结构中,蛹的呼吸管和卵的外部形态特征均可以作为其重要的鉴别特征。该研究为中华按蚊的分类学以及蚊媒防控研究提供了更为详细和直观的形态特征鉴定依据。

[Objectives]To determine the morphological characters of Anopheles sinensis Wiedemann,an important vector of malaria in China,and thereby provide a reference for the identification and classification of the Hycanus group.[Methods]Samples were fixed with 1%osmium acid and 6%glutaraldehyde,and specimens of different developmental stages prepared for electron microscopy by combining dehydration at different ethanol concentrations with tert-butanol vacuum freeze-drying.Morphological characters were observed and recorded using a Hitachi SU3500 electron microscope at 5 kV voltage in the SE(secondary electron)mode.[Results]There was little sexual dimorphism in beak or antennae length.Adult males have horsetail tentacles with enlarged,curved ends and circular-cake pedicels and the tail organs at the end of their abdomen have a pair of pincer-like arms.Adult females have slender beaks and serrated upper and lower jaws,which are used for piercing human skin and sucking blood.Their pedicels are full and spherical and the tail organs at the end of the abdomen have a pair of inwardly curved tail whiskers that are obviously shorter than the male’s pincer-like arms.Electron microscopy revealed that the respiratory tubes of the tadpole-like pupa are on the head and have an acute triangular opening with a smooth circle of blunt teeth at the edge.The fan-shaped caudal fin is two-petaled.The external genitalia of male pupae are obviously longer than those of female pupae.4th instar larvae have a linked thorax and abdomen,spiny receptors on the antennae,and a valve on dorsal end of the 8th abdomen segment.The eggs are boat shaped and have a larger surface area than the eggs of other mosquito species.Eggs have evenly distributed,small,granular protrusions on their surface,most of which are arranged in a hexagonal pattern.Eggs also have flat,fine pores at their dorsal ends.[Conclusion]The respiratory tubes of pupae and the external morphology of eggs are important characteristics for identifying A.sinensis.These results not only provide valuable information for identifying A.sinensis but also aids mosquito-borne disease control.