云南切梢小蠹幼虫不同发育阶段头部感器的对比观察

Morphological observation and comparison of sensilla on the head appendages of different instar larva of Tomicus yunnanensis(Coleoptera:Curculionidae:Scolytinae)

为探究和分析云南切梢小蠹Tomicus yunnanensis Kirkendall&Faccoli幼虫3个发育阶段头部感器的差别及其功能作用,应用场发射扫描电子显微镜对其触角和口器上的感器进行了对比观察。结果表明:云南切梢小蠹幼虫头式为下口式,头部前方有1对1节的触角,着生有锥形感器1和末梢锥形感器1~4,且每种感器在每根触角上的数量仅有1~3个;口器分为上唇、上颚、下颚和下唇4部分,共有5类12种感器,分别为毛形感器1~2、刺形感器1~5、锥形感器2、指形感器和末梢锥形感器2、4、5,每种感器的数量有4~406个不等。毛形感器和刺形感器表面光滑、无孔,位于口器的各个部位,为机械感器;锥形感器和末梢锥形感器表面具孔,集中分布于触角、下颚须和下唇须端部,应为化学感器;指形感器为下颚须和下唇须特有,每侧仅有1个,可能对声音震动有感知能力。随着幼虫龄数的增加,不同发育阶段的幼虫头部各感器的类型、数量和分布保持稳定,但各感器的大小呈指数级增加。研究结果将为理解云南切梢小蠹幼虫取食行为提供了科学依据。

To clarify the diversification and function of the sensilla on the head appendages of different instar larvae of Tomicus yunnanensis(Coleoptera:Curculionidae:Scolytinae),we observed the ultrastructure of the larval head by using field-emission scanning electron microscopy.The main results were as follows:1)The structure type of the larval head was hypognathous.2)The antennae were situated at the front view of the head with one segment and five types of sensilla that were identified as sensilla basiconica 1 and sensilla twig basiconica 1~4 with 1~3 individuals.3)The mouthpart was consist of the labrum,mandible,maxilla,and labium.There were 12 types of the sensilla,including sensilla trichodea 1~2,sensilla chaetica 1~5,sensilla basiconica 2,sensilla digitiformia,and sensilla twig basiconica 2,4 and 5.Each type of sensilla was presented by 4~406 individuals on each section of mouthpart.4)Sensilla trichodea and sensilla chaetica having smooth and nonporous surfaces were widespread and regarded as mechanical sensations,sensilla basiconica and sensilla twig basiconica having the surface pores occurred only on the terminal tip of the antennae,maxillary palp,and labial palp and were considered as the chemoreceptive functions,sensilla digitiformia having only one on the ventral view of every palp might sense the signals of acoustic vibrations;5)Sensilla type,abundance and distributions on every segment of head appendages were consistent with different instar larvae,but there were significant differences in the sensilla sizes of every type.This research will provide a scientific basis for further exploration of foraging behavior about the larvae of T.yunnanensis.