title: Pre-spermiogenic initiation of flagellar growth and correlative ultrastructural observations on nuage, nuclear and mitochondrial developmental morphology in the zebrafish Danio rerio.
abstract: The microstructural and ultrastructural changes of germ cells during spermatogenesis of zebrafish (Danio rerio) were examined using light microscopy (LM) and transmission electron microscopy (TEM). Generally the process of spermatogenesis in zebrafish is similar to that of other teleosts, however, here we describe some peculiar features of zebrafish spermatogenic cells which have a limited report in this species. (1) The basic events of spermiogenesis are asynchronous, location of flagellum finished in initial stage, while chromatin condensation sharply occurred in intermediate stage and elimination of excess cytoplasm mainly taken place in final stages. (2) Surprisingly, the cilia or initial flagellae are created in spermatocytes, approach toward the nucleus of early stage spermatids, and then the centrioles depress into nuclear fossa and change their orientation to each other from right angle to obtuse angle about 125°. (3) During spermatogenesis, the chromatin compaction performs in a distinctive pattern, condensed heterogeneously from granular into chromatin clumps with central electron-lucent areas, round or long, which diminished to small nuclear vacuoles in spermatozoa. This finding demonstrates the origin of nuclear vacuoles in zebrafish spermatozoa for the first time. (4) Nuages are observed in both spermatogonia and spermatocytes. They are connected with the mitochondria and nuclear membrane, and are even located in the perinuclear spaces of spermatogonia nuclei. (5) Mitochondrial morphology and distribution shows diversity in different germ cells. The condensed mitochondria appear in pachytene spermatocytes, and mitochondria including membrane conglomerate exist in both spermatocytes and spermatids. This study was undertaken in order to disclose specific spermatogenic cells features in zebrafish that could be helpful for understanding the correlative function in this model species.
authors: Laboratory of Animal Cell Biology and Embryology, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China.
authors: Linli
authors: L
authors: Zhang
authors: Laboratory of Animal Cell Biology and Embryology, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China.
authors: Ping
authors: P
authors: Yang
authors: Laboratory of Animal Cell Biology and Embryology, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China.
authors: Yi
authors: Y
authors: Liu
authors: Laboratory of Animal Cell Biology and Embryology, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China.
authors: Xunguang
authors: X
authors: Bian
authors: Laboratory of Animal Cell Biology and Embryology, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China.
authors: Shakeeb
authors: S
authors: Ullah
authors: Laboratory of Animal Cell Biology and Embryology, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China.
authors: Qian
authors: Q
authors: Zhang
authors: Laboratory of Animal Cell Biology and Embryology, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China.
authors: Wei
authors: W
authors: Chen
authors: Laboratory of Animal Cell Biology and Embryology, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China.
authors: Yuan
authors: Y
authors: Le
authors: Laboratory of Animal Cell Biology and Embryology, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China.
authors: Bing
authors: B
authors: Chen
authors: Shanghai Laboratory Animal Research Centre, Shanghai Institutes for Biological Sciences, Shanghai, China.
authors: Jinxing
authors: J
authors: Lin
authors: Shanghai Laboratory Animal Research Centre, Shanghai Institutes for Biological Sciences, Shanghai, China.
authors: Cheng
authors: C
authors: Gao
authors: Shanghai Laboratory Animal Research Centre, Shanghai Institutes for Biological Sciences, Shanghai, China.
authors: Jianhua
authors: J
authors: Hu
authors: Laboratory of Animal Cell Biology and Embryology, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China. Electronic address: chenqsh305@njau.edu.cn.
authors: Qiusheng
authors: Q
authors: Chen
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000000981:diagnostic imaging*; D002843:Chromatin / Q000000981:diagnostic imaging; D003593:Cytoplasm / Q000648:ultrastructure; D005407:Flagella / Q000648:ultrastructure*; D008297:Male; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008928:Mitochondria / Q000648:ultrastructure*; D009685:Nuclear Envelope / Q000648:ultrastructure; D013091:Spermatogenesis / Q000502:physiology*; D013094:Spermatozoa / Q000648:ultrastructure*; D014463:Ultrasonography; D015027:Zebrafish / Q000254:growth & development*
chemical_list: D002843:Chromatin
keywords: Chromatin; Fine structure; Flagella; Mitochondria; Spermatid; Zebrafish