兴义维蚋中枢神经系统的组织学观察

Histological Observation of the Central Nervous System in Simulium(Wilhelmia)xingyiense(Diptera:Simuliidae)

目的研究兴义维蚋成熟幼虫、成熟蛹和新羽化成虫中枢神经系统的组织解剖学结构特点。方法2009年8～11月在贵阳市花溪牛角岛溪流中采集蚋类幼虫，依据鳃斑、后颊裂和直肠鳃等形态学特征筛选出兴义维蚋成熟幼虫：2011年3月在贵阳大凹和青岩古镇旁小溪中采集成熟蛹，依据蛹茧和呼吸丝特征筛选出兴义维蚋成熟蛹，将蛹孵化为新羽化成虫。成熟幼虫、成熟蛹和新羽化成虫各取30只进行石蜡连续切片，经苏木素-伊红（HE）染色后对神经系统进行组织学观察。结果各个发育时期的兴义维蚋的中枢神经系统均由脑、食道下神经节和腹神经索3部分组成．止于第6腹节处。幼虫的脑分为左右2个半球，神经髓较简单，腹神经索包括3对胸神经节和8对腹神经节，第Ⅵ-Ⅷ腹神经节有愈合为复合神经节的倾向。蛹和成虫的脑部明显分化为前脑、中脑和后脑3部分，腹神经索包括3对胸神经节和5对腹神经节，及纵贯各神经节的神经索。脑和各体神经节的组织学结构相似，由外到内依次是神经鞘、神经细胞体层和髓质层。前脑叶的髓质层复杂，包括一对蕈形体、一个中央复合体和一对附叶，每侧蕈形体出现2个不发达的次生性融合的冠；视叶由视内髓、视外髓和视神经节层组成；中脑由中脑叶和触角中枢形成；后脑通过围食道神经与食道下神经节相连。结论兴义维蚋的中枢神经系统组成与其他蚋种相似，但在成熟幼虫腹部神经节数目上存在差异。

Objective To investigate the morphological characters of the central nervous system in mature larvae, mature pupae and newly emerged adults of Simulium （Wilhelmia） xingyiense. Methods From August to November 2009, the blackfly larvae were collected from the rivulets nearby Niujiao Island in Huaxi of Guiyang City. The mature larvae of S. （Wi.） xingyiense were confirmed based on the diagnostic characteristics of gill spots, postgenal cleft, and rectal gill. The mature pupae were obtained from the rivulets of Da＇ao Town and Qingyan Town in Guiyang in March 2011, which were selected according to the characteristics of cocoon and respiratory filaments. Nervous system of the larvae, pupae and newly emerged aduhs was observed under the light microscope with HE-stained paraffin sections. Results The central nervous system was composed of brain, subesophageal ganglion and ventral nerve cord. The brain of the larva was divided into two narrowly interconnected egg-shaped lobes. Ventral nerve-cord of the larva consisted of three pairs of thoracic ganglia and eight pairs of abdominal ganglia. The brain of the pupa and adult was composed of protocerebrum, deutocerebrum, and tritocerehrum. The ventral nerve cord of the pupa and adult was similar to that of larva. From outside to inside, the structure characters of the brain and ganglia were similar with nerve sheath, neurocyte and neuropile. The neuropile of protocerebrum contained a pair of mushroom bodies, a central complex and a pair of accessory lobes. The optic lobe was composed of medulla interna, medulla externa and lamina ganglionaris. The deutoeerebrum consisted of the antennal lobe and the dorsal lobe. The tritocerebrum connected to the subesophagcal ganglion by perioperative esophageal nerve. Conclusion The central nervous system of S. （Wi.） xingyiense is similar to other simuliid blackflies. There is a difference in the number of abdominal ganglion of the mature larva.