蒙古马马鼻狂蝇三龄幼虫的形态学和分子生物学研究

Morphological and Molecular Characteristics of L3-Stage Rhinoestrus sp. from Mongolian Horse in China

为了研究蒙古马鼻狂蝇三龄幼虫的形态学和分子生物学特性,利用扫描电镜对马鼻狂蝇三龄幼虫的头部、尾部和第三体节棘刺进行形态观察;并选取蒙古马鼻狂蝇三龄幼虫,提取其线粒体CoxI基因和16S rRNA基因,进行碱基组成分析和系统发育树构建。结果发现:(1)马鼻狂蝇气门板上的结构不同于其它狂蝇,其气门板上由硬化的骨质形成期的孔缘围绕,气门肌肉使得气门板上的开口呈垂直形态,在后气门板上有几排小刺;头部有1对乳突状感受器,其上分布着1对疣状乳突;(2)蒙古马鼻狂蝇三龄幼虫的CoxI、16S rRNA基因均与GenBank数据库中提交的马胃蝇、纹皮蝇、鹿狂蝇、羊狂蝇等在系统发育树中分开。虽然蒙古马鼻狂蝇三龄幼虫形态上跟紫鼻狂蝇很像,但是其分子生物学特点说明它可能是一个新变种。

In order to explore the ultrastructure and molecular characteristics of third instar (L3) larvae of Rhinoestrus sp. from Mongolian horse, the structure of the anterior region, posterior region, and the spines of the third segment was analyzed (L3 larvae of Rhinoestrus sp.) by scanning electron microscopy. Additionally, L3 larvae of Rhinoestrus sp. from Mongolian horse were subjected to molecular characterization by polymerase chain reaction. Partial sequencing of the mitochondrial cytochrome oxidase subunit I gene ( Cox I) and 16S ribosomal RNA(16S rRNA) were performed. Phylogenetic relationships for Rhinoestrus sp. from Mongolian horse were reconstructed based on Cox I ,16S rRNA sequences and homologs from oestrid species available in GenBank, and inter-and intraspecies variations in nucleotide sequences were analyzed. Scanning electron microscopy observation showed that the posterior spiracular discs had incomplete peritremes. Two long, narrow spiracular slits were oriented more or less vertically in each spiracular disc. A row of spines was observed adjacent to the posterior spiracular discs.The pairs of papillary sensilla included two pairs of verruciform sensilla in the cephalic region. Phylogenetic relationships showed that Cox I and 16S rRNA sequences of Rhinoestrus sp. larvae collected from Mongolian horses were separated from those of Gasterophilinae, Hypodermatinae,Cephenemyia sp. and Oestrus ovis . Our ultrastructure and sequence analysis demonstrated that all samples from Mongolian horses greatly resembled Rhinoestrus purpureus , but were not Rhinoestrus purpureus . Further studies will be needed to confirm the existence of a new species.