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Sperm morphology of the eurasian beaver, Castor fiber : An example of a species of rodent with highly derived and pleiomorphic sperm populations
Author(s) -
Bierla Joanna B.,
Gizejewski Zygmunt,
Leigh Christopher M.,
Ekwall Hans,
Söderquist Lennart,
RodriguezMartinez Heriberto,
Zalewski Kazimierz,
Breed William G.
Publication year - 2007
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.10544
Subject(s) - spermatozoon , biology , acrosome , sperm , anatomy , nucleus , spermatheca , beaver , ultrastructure , microbiology and biotechnology , botany , ecology
The structural organization of the spermatozoon from the Eurasian beaver, Castor fiber (Family: Castoridae), was determined and compared to that of other sciuromorph rodents. The beaver spermatozoon has a head, which is variable in form but usually paddle‐shaped, with a small nucleus and very large acrosome, and a tail that is relatively short compared to that of most other rodents. Transmission electron microscopy indicates that in most testicular spermatozoa the acrosome projects apically, although in a few it becomes partly flexed. During the final stages of maturation, however, the acrosome becomes highly folded so that the apical segment comes to lie alongside part of the acrosome that occurs lateral to the nucleus, with, in some cases, fusion taking place between the outer acrosomal membranes. The sperm nucleus is wedge‐shaped, being broader basally and narrowing apically with an occasional large nuclear vacuole occurring. This spermatozoon structure is markedly different from that found in the other species of Geomyoidea, which is the sister group of the Castoridae. The findings thus emphasize the highly divergent nature of the beaver spermatozoon and demonstrate that, within the proposed Infraorder Castorimorpha, very large differences in sperm structure have evolved. J. Morphol., 2007. © 2007 Wiley‐Liss, Inc.