The Character of Sperm Maturation in the Epididymis of the Ascrotal Hyrax, Procavia capensis and Armadillo, Dasypus novemcinctus

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Abstract
The maturation and storage of spermatozoa in the Wolffian duct appear to have become considerably more complex in scrotal mammals as compared with many submammalian vertebrates. As part of a systematic study of the evolutionary correlates of this trend to complexity in mammals, various parameters of epididymal function have been examined in 2 ascrotal (testicondid) eutherian mammals, the rock hyrax, Procavia capensis and the armadillo, Dasypus novemcinctus. Maturation of spermatozoa in the epididymis of these testicondids is reflected in a pattern of changes which appears little different from that of scrotal mammals. It is characterized by increased stability of the sperm nucleus and structural elements of the tail engendered through crosslinking of protein bound thiols, by change in the binding affinity for lectins and cationic ferric oxide colloid particles of components expressed on the surface of the sperm tail (hyrax and armadillo) and head (armadillo) and, morphologically, by migration and loss of the cytoplasmic droplet and, especially in the hyrax, reduction in the size of the acrosome. By contrast, an obvious difference exists between testicondid and scrotal therians in the conditions which mediate sperm storage in the epididymis. Hyrax spermatozoa retain the capacity for optimal motility for at least 30 days in the terminal storage region deep within the pelvic cavity, whereas the spermatozoa of scrotal mammals do not survive at body temperatures. The implications of the results for understanding of the significance of epididymal function and scrotal development are discussed briefly.

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