埃及尼罗鲶鱼精子形成及精子超微结构(英文)
A Novel Type of Spermiogenesis in the Nile Catfish Chrysichthys auratus (Siluriformes: Bagridae) in Egypt, with Description of Spermatozoon Ultrastructure ( in English)
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摘要: 用透射电镜观察了埃及尼罗鲶鱼（Chrysichthys auratus）精子形成及精子超微结构。精子形成过程除了具有鱼类精子形成的共同特征外，还具有一些特点：由于细胞核没有转动，中心粒复合体和鞭毛的起始部分位于细胞核的后端，并与核垂直；精子细胞变态过程中未产生袖套腔；基板未跨越基体的基部；基足将基体固定于细胞核；中段和鞭毛的基部具大量囊泡。成熟精子头部呈长锥状，没有顶体；中段长并含大量囊泡，向后延伸并包围鞭毛的基部；鞭毛细长，无侧鳍；线粒体位于核的后端附近，并包围轴丝；轴丝具典型的“9+2”模式。总之，埃及尼罗鲶鱼的精子形成有别于硬骨鱼类的常见的精子形成类型——I型和II型，可以称为III型。Abstract: Spermiogenesis and spermatozoon ultrastructure in the Nile catfish Chrysichthys auratus are described using transmission electron microscopy. Spermiogenesis involves some unique peculiarities such as: the development of the centriolar complex and the initial segment of the flagellum in a position directly perpendicular to the basal pole of the nucleus, as a result of absence of nuclear rotation; lack of a cytoplasmic canal during differentiation of the spermatids into spermatozoa; the base of the basal body is not traversed by the basal plate; a basal foot anchors the basal body to the nucleus; and the presence of numerous vesicles around the midpiece and base of the flagellum. In addition, spermiogenesis includes some common features such as: chromatin compaction; formation of a medial shallow nuclear fossa; and elimination of excess cytoplasm. The mature spermatozoon has an elongate conical-shaped head with no acrosome or acrosomal vesicle, a long midpiece with numerous vesicles that continue backwards around the base of the flagellum and a long tail or flagellum, which has no lateral fins or a membranous compartment. The mitochondria lie close to the nucleus basal pole and surround the initial segment of the axoneme and are separated from the flagellum by the inner mitochondrial envelope due to disappearance of the cytoplasmic canal. The flagellum has the classical axoneme structure of a 9+2 microtubular pattern. On the basis of the peculiar features mentioned above, it is concluded that spermiogenesis in this Nile catfish is a synapomorphic type derived from types I and II spermiogenesis, which are common among teleosts. Accordingly, this type could be considered as a novel type of spermiogenesis and could be termed as “type III”.
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