THE MALE REPRODUCTIVE-CYCLE OF THE LIZARD, CORDYLUS-GIGANTEUS (SAURIA, CORDYLIDAE)

Cordylus giganteus is a large, terrestrial, viviparous lizard endemic to the Highveld grasslands of South Africa. It has a limited distribut ion and is regarded by conservationists as threatened. The testicular cycle and associated seasonal variation in the sexual accessory struct ures, together with plasma testosterone levels, were studies over a pe riod of 15 months. Minimum size at maturity was about 165 mm snout-ven t length (SVL). Reproduction was distinctly seasonal and the timing of events deviated from the typical saurian pattern. Males exhibited a b asic post-nuptial spermatogenic cycle in which testicular growth and r ecrudescence began in summer, after emergence from winter hibernation and spring mating, followed by peak testicular size and spermiogenesis in late summer/autumn and testicular regression in late autumn and wi nter. Spermatozoa were stored in the ductus epididymidis and ductus de ferens for 7-8 months. Plasma testosterone levels peaked twice during the testicular cycle, typically coinciding with spermiogenesis in late summer and also in spring at the time of mating. The epithelial heigh ts of the ductus epididymidis, ductus deferens,and renal sexual segmen t showed significant seasonal variation, and peak secretory activity c oincided with spermiogenic activity and high circulating testosterone levels in autumn. The second rise in plasma testosterone occured in sp ring, but was not accompanied by increased secretory activity of eithe r the ductus epididymidis or the renal sexual segment epithelia. Testi cular recrudescence was correlated with increasing ambient temperature s, photoperiod, and summer rainfall, whereas testicular regression dur ing late autumn corresponded to decreasing ambient temperatures, photo period, and rainfall. This study adds to data that indicate that autum n reproductive activity is the common reproductive strategy among vivi parous cordylids and provides another example of asynchronous reproduc tive activity between male and female lizards.