Sperm Morphology of the Eurasian Beaver, Castor fiber: An Example of a Species of Rodent with Highly Derived and Pleiomorphic Sperm Populations

摘要: The structural organization of the spermatozoon from Eurasian beaver, Castor fiber (Family: Castoridae), was determined and compared to that other sciuromorph rodents. beaver has a head, which is variable in form but usually paddle-shaped, with small nucleus very large acrosome, tail relatively short most Transmission electron microscopy indicates testicular spermatozoa acrosome projects apically, although few it becomes partly flexed. During final stages maturation, however, highly folded so apical segment comes lie alongside part occurs lateral nucleus, with, some cases, fusion taking place between outer acrosomal membranes. sperm wedge-shaped, being broader basally narrowing apically an occasional nuclear vacuole occurring. This structure markedly different found species Geomyoidea, sister group Castoridae. findings thus emphasize divergent nature demonstrate that, within proposed Infraorder Castorimorpha, differences have evolved.