title: Spermatozoon of the freshwater rotifer Brachionus calyciflorus (Rotifera, Monogononta): Advances in morphological and ultrastructural studies.
abstract: The morphological and ultrastructural features of the spermatozoon in Brachionus calyciflorus are described using light, fluorescence and transmission electron microscopy (TEM). The mature spermatozoon, which appears to be thread-like, is composed of a slightly expanded anterior of cell body region and a flagellum region without acrosome. The cell body region and flagellum region are respectively 16-27μm and 20-33μm in length (n=60). The spermatozoon is characterized by a mass of dense tubular materials, which occupy most of the cell. Some mitochondria are distributed around the nuclear region in the anterior of the cell body region, while in the posterior portion of cell body, the chromatin often contains a single lobated nucleus arranged at the center of cell. The flagellum contains the classic axoneme (9×2+2) and possesses lateral undulating membrane. Mature B. calyciflorus males have no germ cell stages earlier than the spermatids in the testis. TEM examination reveals rigid rods as well as predominant typical spermatozoon in the testis. Observations, based on successive photographs and videos, enabled a first-time recording of the unique inverted movement of the spermatozoon, which indicated that the movement of the spermatozoon is driven by the flagellum. Our study also provides further supplementary insights into the phylogenetic systematics of the Rotifera.
authors.affiliation: Jiangsu Province Key Laboratory for Aquatic Live Food, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu 210023, China. Electronic address: gushuyu@njnu.edu.cn.
authors.forename: Shuyu
authors.initials: S
authors.lastname: Gu
authors.affiliation: Jiangsu Province Key Laboratory for Aquatic Live Food, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu 210023, China.
authors.forename: Lian
authors.initials: L
authors.lastname: Li
authors.affiliation: Jiangsu Province Key Laboratory for Aquatic Live Food, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu 210023, China.
authors.forename: Luxiaoxue
authors.initials: L
authors.lastname: Liang
authors.affiliation: Jiangsu Province Key Laboratory for Aquatic Live Food, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu 210023, China.
authors.forename: Xuezhou
authors.initials: X
authors.lastname: Liu
authors.affiliation: Jiangsu Province Key Laboratory for Aquatic Live Food, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu 210023, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Ouyang
authors.affiliation: Jiangsu Province Key Laboratory for Aquatic Live Food, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu 210023, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: Jiangsu Province Key Laboratory for Aquatic Live Food, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu 210023, China. Electronic address: yangjx@njnu.edu.cn.
authors.forename: Jiaxin
authors.initials: J
authors.lastname: Yang
mesh_terms: D000818:Animals; D002843:Chromatin / Q000648:ultrastructure; D008124:Locomotion; D008297:Male; D008853:Microscopy; D015388:Organelles / Q000648:ultrastructure; D012403:Rotifera / Q000166:cytology / Q000648:ultrastructure*; D013094:Spermatozoa / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure*; D013737:Testis / Q000166:cytology / Q000648:ultrastructure*; D059008:Time-Lapse Imaging
chemical_list: D002843:Chromatin
keywords: Brachionus calyciflorus; Morphology; Spermatozoon; Transmission electron microscopy (TEM); Ultrastructure