四种蝉科昆虫的精子形态(半翅目:蝉科)

Sperm morphology of four cicada species( Hemiptera: Cicadidae)

【目的】为了明晰蝉科昆虫的精子形态及其在分类和系统发育分析方面的意义,本研究对蝉亚科的蒙古寒蝉Meimuna mongolica、黑蚱蝉Cryptotympana atrata、蛉蛄Pycna repanda及姬蝉亚科的蟋蝉Tettigetta sp.的精子进行了比较研究。【方法】分别通过光学显微镜和透射电子显微镜,观察这4种蝉科昆虫的精子形态特征。【结果】蒙古寒蝉、黑蚱蝉、蛉蛄和蟋蝉这4种蝉科昆虫精子形态基本相似,但精子长度在种内和种间都有明显不同,均表现出多态性。根据精子长度,蛉蛄精子可被分为长精子、中长精子和短精子3种类型;蒙古寒蝉、黑蚱蝉和蟋蝉的精子被分为长精子和短精子2种类型。4种蝉的精子结构也基本相似,头部包含顶体和细胞核,颈区由中心粒和中心粒侧体组成,尾部一般由一根轴丝和一对线粒体衍生物组成,轴丝微管为9+9+2模式。但蝉亚科3个物种的部分精子具有多个线粒体衍生物;首次在蛉蛄精子尾部发现一个电子致密的三角形区域,该结构在蝉科其他昆虫精子中未曾发现。蝉科不同类群的精子中心粒侧体存在显著差异,姬蝉亚科的蟋蝉精子中心粒侧体为片层状结构,蝉亚科昆虫则为鞘状结构。【结论】与蝉次目的角蝉总科和沫蝉总科昆虫精子相比,仅蝉科昆虫的精子表现出多态性,是该科的特有衍征。精子尾部可具多个线粒体衍生物的现象在蝉亚科物种中是否普遍存在有待进一步研究。蝉科不同类群在精子形态方面的差异,为蝉科昆虫分类及蝉次目系统发育分析提供了重要信息。

【Aim】In order to clarify the sperm morphology of Cicadidae and their significance in insect taxonomy and phylogeny,the sperm ultrastructures of Meimuna mongolica,Cryptotympana atrata,Pycna repanda,and Tettigetta sp.were compared in this study.【Methods】The morphological characteristics of sperm of four species of Cicadidae were observed using light and transmission electron microscopies,respectively.【Results】The sperm morphologies of M.mongolica,C.atrata,P.repanda and Tettigetta sp.are similar,but the sperm length is significantly different within and between species.Spemotozoa of all these investigated species show polymegaly.Based on the length of spermatozoa,spermatozoa in P.repanda can be divided into three types,i.e.,long spermatozoa,medium spermatozoa,and short spermatozoa.The spermatozoa of M.mongolica,C.atrata and Tettigetta sp.are only divided into two types,i.e.,long spermatozoa and short spermatozoa.The sperm ultrastructures of these four species are similar,i.e.,the head region contains the acrosome and the nucleus,the neck region is composed of a centriole and a centriolar adjunct,the tail region generally consists of an axoneme and a pair of mitochondrial derivatives,and the axoneme has a 9+9+2 arrangement of microtubules(9 accessory microtubules,9 doublet microtubules,and 2 central microtubules).However,some differences were revealed in sperm ultrastructure among different species.Some spermatozoa in the three species of the subfamily Cicadinae possess multiple mitochondrial derivatives.An electron-dense deltoid region exists in the sperm tail of P.repanda,which has never been found in other cicadas.The structure of the centriolar adjunct of spermatozoa is significantly distinct among different subfamilies within the Cicadidae.The centriolar adjunct exhibits a lamellar structure in Cicadettinae,but has a sheath structure in Cicadinae.【Conclusion】Compared with the spermatozoa in Membracoidea and Cercopoidea within Cicadomorpha,only the spermatozoa in Cicadidae show polymegaly,which is a synapomorphy of this family.Whether the occurrence of multiple mitochondrial derivatives in the tail of flagellum is ubiquitous within the subfamily Cicadinae still needs further study.The differences in sperm morphology in different groups of Cicadidae provide significant information for the taxonomy of Cicadidae and the phylogenetic analysis of Cicadomorpha.