Levron Céline, Sitko Jiljí, Scholz Tomás
Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, Czech Republic.
J Parasitol. 2009 Feb;95(1):1-9. doi: 10.1645/GE-1646.1.
Using transmission electron microscopy, spermiogenesis and the spermatozoon ultrastructural organization are described in Ligula intestinalis (Linnaeus, 1758) (Diphyllobothriidea), a parasite of the great crested grebe Podiceps cristatus (Linnaeus, 1758). Spermiogenesis starts with the differentiation zone of 2 striated rootlets, 2 centrioles giving rise to 2 flagella, and an intercentriolar body. The latter is composed of 5 electron-dense layers separating 4 electron-lucent layers. In the early stages of spermiogenesis, an electron-dense material is present in the apical region of the differentiation zone. Later, the flagella undergo a rotation and fuse with the cytoplasmic extension in a proximo-distal process. The spermatozoon contains 2 axonemes with a 9 + "1" trepaxonematan pattern, the nucleus, the cortical microtubules, and an electron-dense zone. The spermatozoon anterior extremity in L. intestinalis is characterized by the absence of crested bodies and a ring of electron-dense cortical microtubules. Some characters of spermiogenesis and spermatozoon in L. intestinalis confirm the recent splitting of "Pseudophyllidea" into 2 new orders, i.e., Bothriocephalidea and Diphyllobothriidea. The process of spermiogenesis is similar in both orders for the "type I" of spermiogenesis and the presence of electron-dense material. However, the intercentriolar body is clearly more developed in the Diphyllobothriidea than in the Bothriocephalidea. Moreover, these 2 orders seem to differ in the presence or absence of a ring of electron-dense cortical microtubules in the anterior extremity of the spermatozoon.
利用透射电子显微镜,对凤头鸊鷉(Podiceps cristatus,林奈,1758)的一种寄生虫——阔节裂头绦虫(Ligula intestinalis,林奈,1758)(双叶槽绦虫目)的精子发生过程及精子超微结构组织进行了描述。精子发生始于2条横纹小根、2个产生2条鞭毛的中心粒和一个中心粒间体的分化区。后者由5个电子致密层分隔4个电子透明层组成。在精子发生的早期阶段,分化区顶端区域存在电子致密物质。之后,鞭毛发生旋转,并在近-远轴过程中与细胞质延伸部分融合。精子含有2条具有9 + “1” 三辐射轴丝模式的轴丝、细胞核、皮质微管和一个电子致密区。阔节裂头绦虫精子的前端特征是没有嵴状体和一圈电子致密的皮质微管。阔节裂头绦虫精子发生和精子的一些特征证实了最近 “假叶目” 被分为2个新目,即双槽头绦虫目和双叶槽绦虫目。对于 “I型” 精子发生和电子致密物质的存在,这两个目的精子发生过程相似。然而, 双叶槽绦虫目的中心粒间体明显比双槽头绦虫目的更发达。此外,这两个目在精子前端是否存在一圈电子致密的皮质微管方面似乎有所不同。