四种胃蝇三期幼虫的扫描电镜观察

OBSERVATIONS OF FOUR KINDS OF GASTEROPHILUS THIRD INSTARS UNDER SCANNING ELECTRON MICROSCOPY

为准确掌握伊犁马四种胃蝇属三期幼虫的鉴别特征,本文以伊犁地区采集的马胃蝇蛆(n=200)为试验材料,借助体视显微镜、扫描电子显微镜对其进行形态学鉴定,并以各属蝇蛆每节排列刺的差异、形状、口钩及气门板等结构作为鉴定依据。结果显示,本次试验共鉴定出四种马胃蝇三期幼虫:兽胃蝇蛆、鼻胃蝇蛆、红尾胃蝇蛆、肠胃蝇蛆。超微观察可见鼻胃蝇三期幼虫第一胸段出现"隔板状"突出物、其刺列为单排刺列且胸部第一刺列为双排刺,此外鼻胃蝇三期幼虫口钩表面纹路差异较大且表面沟壑中有类似"纤毛状物"的存在;兽胃蝇三期幼虫背侧下颌骨部分扩展成叶且叶部的顶部为平滑状,其他三种胃蝇属三期幼虫叶部的顶端部位为锯齿状;红尾胃蝇形态学特征与肠胃蝇差异不显著,但其寄生部位与刺带特征可作为其鉴定依据。胃蝇属常见四种三期幼虫体表刺列、头部下颌骨叶部、口钩表面沟壑等均可作为其鉴别要点,为马胃蝇三期幼虫的鉴定提供参考依据。

To gather knowledge for the diagnostic characteristics of the third-stage larvae of four equine Gasterophilus species, 200 equine Gasterophilus samples were collected from Ili region, Xinjiang and examined for their morphological identification under stereo microscopy and scanning electron microscopy. The identification basis for Gasterophilus species were their differences of spine rows on every segments, shapes, mouth hooks and stigmal plates. These Gasterophilus samples were found to contain the third-stage larvae of four equine Gasterophilus species, i.e. G.pecorum, G.nasalis, G.haemorrhoidalis and G.intestinalis. Ultramicroscopic observations revealed that the third-stage larvae of G.nasalis had a ＂separator like＂ process on its first thorax area with single spines while double rows of spines were arranged on the first thorax area. Additionally, more differences on the superficial stripes of mouth hooks and existence of similar ＂seta like＂ structures in superficial gullies were noted. The dorsal mandibles of the third-stage larvae of G.pecorums expanded andformed the smooth lobes at the apex while the serrate lobes at the apexes were observed in other Gasterophilus species. The differences of morphological characters of G.haemorrhoidalis and G.pecorum were minor but the parasitic positions and characteristics of spine zones were quite different and considered as identification basis. In conclusion, the major identification points of the third-stage larvae of the most common four Gasterophilus were the superficial spine rows, mandible lobes of head and superficial gully of mouth hooks.