Study on the development of sperm motility and social dominance of male mice.

It has been shown that sperm motility and other parameters related to the reproductive activity varied depending on the social status of male mice. In order to clarify whether such variation is derived from inborn difference or depends on any conditions during maturation, we investigated developmental change of sperm motility, reproductive organs, and body size of ddY male mice. We also investigated how the establishment of social dominance of male mice during maturation was correlated with sperm motility. It was found that sperm motility was significantly higher during puberty than in adulthood, although there already existed relatively large statistical variance. The correlation between sperm motility and the social status was revealed to start after 10 weeks of age. It was suggested that a certain inborn difference of sperm motility became enlarged due to environmental factors experienced by male mice during maturation.