The spermatozoon

Despite the brilliant disclosures from biological research in the past quarter century about the nature of the genetic code, as well as how the genetic information system works through cooperating proteins in message transmittal, there has been surprisingly little attention paid or thought given to the role of the male gamete in species economy other than as a vehicle for bridging generations. The repetitive nature from species to species of male gametogenesis has been observed, as has the sequence of events giving spermatozoa functional integrity and competence, but their period of independence and their senescence have not been clearly detailed and the significance of these events integrated into the body of biological knowledge. The worldwide, 40-year experience with commercial artificial insemination of cattle in genetic improvement programs has generated most of the research and experience resulting in a system of practical, manipulative management of mammalian spermatozoa from which precise fertility data have emerged. These data revealed many facts about such spermatozoa that would not so readily have been observed otherwise. Such observations on a familiar mammalian species and their comparison with those made on more manipulatable species for laboratory control suggest a highly interacting life-cycle pattern for spermatozoa in which environmental temperature plays a controlling role and emphasizes the potential importance of the male in species evolution.