Department of Comparative Anatomy, Institute of Zoology and Biomedical Research, Jagiellonian University, Cracow, Poland.
J Fish Biol. 2020 Nov;97(5):1491-1506. doi: 10.1111/jfb.14518. Epub 2020 Sep 17.
The aim of this study was to analyse spermatogenesis in the African butterflyfish, Pantodon buchholzi, using transmission electron microscopy and scanning electron microscopy. P. buchholzi is the most basal teleost that exhibits insemination and produces a highly complex introsperm with the most elongate midpiece known in teleost fishes. Their early stages (spermatogonia and spermatocytes) do not differ greatly from those of other fishes, with the exception of Golgi apparatus degradation appearing as spindle-shaped bodies (SSBs). In round, early spermatids, the development of the flagellum begins after the migration of the centriolar complex towards the nucleus. Later, the elongation of the midpiece coincides with the displacement of the mitochondria and their fusion to produce nine mitochondrial derivatives (MDs). In these spermatids, the nucleus is situated laterally to the midpiece, with condensing chromatin in the centre of the nucleus. Within the midpiece, the flagellum is located within a cytoplasmic canal and is surrounded by a cytoplasmic sleeve containing fibres, MDs and a great amount of cytoplasm located on one side. During the next phase, nuclear rotation, the highly condensed chromatin is displaced to a position above the centriolar apparatus, whereas chromatin-free nucleoplasm is transferred to the cytoplasm. Later, this nucleoplasm, still surrounded by the nuclear membrane, is eliminated into the cyst lumen as the nucleoplasmic packet. Within the highly elongate spermatids, other excess organelles (SSBs, endoplasmic reticulum and mitochondria) are eliminated as residual bodies (RBs). Fully developed spermatozoa, which contain conical-shaped nuclei, eventually coalesce to form unencapsulated sperm packets (spermatozeugmata) that are surrounded by RBs at the level of the extremely elongate midpieces. Later, RBs are removed at the periphery of the cyst by means of phagocytosis by Sertoli cells.
本研究旨在通过透射电子显微镜和扫描电子显微镜分析非洲蝴蝶鱼（Pantodon buchholzi）的精子发生过程。P. buchholzi 是最基础的硬骨鱼，具有内受精的特性，并产生高度复杂的内精子，其中段是硬骨鱼中已知最长的。它们的早期阶段（精原细胞和精母细胞）与其他鱼类没有太大区别，除了高尔基体降解形成纺锤形小体（SSB）。在圆形的早期精细胞中，中心粒复合体向核迁移后，鞭毛开始发育。随后，中段的伸长与线粒体的移位和融合相吻合，产生九个线粒体衍生物（MD）。在这些精细胞中，核位于中段的侧面，核内染色质浓缩在核的中心。中段内，鞭毛位于细胞质管内，周围是含有纤维、MD 和大量位于一侧的细胞质的细胞质鞘。在接下来的核旋转阶段，高度浓缩的染色质被转移到中心粒装置的上方位置，而无染色质的核质被转移到细胞质中。随后，这个核质仍然被核膜包围，被排除到囊泡腔中，形成核质包。在高度伸长的精细胞中，其他多余的细胞器（SSB、内质网和线粒体）被作为残余体（RB）消除。完全发育的精子，含有锥形核，最终融合形成未包裹的精子束（精子束），这些精子束被极度伸长的中段周围的 RB 包围。随后，RB 通过支持细胞的吞噬作用在囊泡的外周被去除。
