Aquatic Animal Health Program, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
Department of Animal Sciences, College of Agricultural and Life Sciences, University of Florida, Gainesville, Florida, USA.
Anat Rec (Hoboken). 2022 Feb;305(2):446-461. doi: 10.1002/ar.24645. Epub 2021 May 6.
Sperm characteristics, such as sperm morphology and sperm morphometry are important in assessing sperm quality. This is especially important for the management and conservation of endangered and exotic species, like the Florida manatee, where information of this nature is extremely limited. In this study, we fill this knowledge gap to better understand the reproductive physiology of Florida manatees by conducting the first extensive analysis of sperm morphometry and ultrastructure. Sperm were retrieved from the vas deferens of nine recently deceased Florida manatees. Computer-aided sperm morphology analysis (CASMA) was used for morphometric analysis and laser-scanning confocal microscopy and electron microscopy were used for structural and ultrastructural characterization. Our findings reveal new morphometric and structural data for the Florida manatee spermatozoon. Twelve morphometric features of Florida manatee sperm were quantified with some approximately 1.5-2 times larger than those previously reported. Ultrastructurally, the Florida manatee spermatozoon followed a mammalian structural pattern with an ovate-shaped head, midpiece containing 84-90 mitochondria, and a flagellum. However, unique ultrastructural features were identified. Distinct, rectangular-like enlargement of four outer dense fibers surrounding the axoneme was evident, which may provide additional tensile strength to counteract the forces on sperm transiting the female reproductive tract. Likewise, strong localization of F-actin fibers within the midpiece may function to maintain sperm integrity within the female reproductive tract. These findings highlight the potential effects of sexual selective pressures on sperm size and structure in the Florida manatee and provide avenues for research on the occurrence of sperm competition in this species.
精子特征，如精子形态和精子形态计量学，在评估精子质量方面非常重要。这对于濒危和外来物种的管理和保护尤为重要，例如佛罗里达海牛，关于这类物种的信息非常有限。在这项研究中，我们通过首次对精子形态计量学和超微结构进行广泛分析，填补了这一知识空白，从而更好地了解佛罗里达海牛的生殖生理学。我们从九头最近死亡的佛罗里达海牛的输精管中提取了精子。使用计算机辅助精子形态分析（CASMA）进行形态计量分析，使用激光扫描共聚焦显微镜和电子显微镜进行结构和超微结构特征描述。我们的研究结果揭示了佛罗里达海牛精子的新形态计量和结构数据。我们对佛罗里达海牛精子的 12 个形态特征进行了定量分析，其中一些特征大约是之前报道的 1.5-2 倍。超微结构上，佛罗里达海牛精子符合哺乳动物的结构模式，具有卵圆形头部、中段含有 84-90 个线粒体和鞭毛。然而，我们还发现了独特的超微结构特征。轴突周围的四个外部致密纤维明显呈矩形扩大，这可能为精子在通过雌性生殖道时提供额外的拉伸强度。同样，中段内 F-肌动蛋白纤维的强烈定位可能有助于在雌性生殖道内保持精子的完整性。这些发现强调了性选择压力对佛罗里达海牛精子大小和结构的潜在影响，并为研究该物种精子竞争的发生提供了途径。
