Biennial reproduction in the female viviparous lizard Cordylus giganteus
AbstractCordylus giganteus is a large, terrestrial, viviparous lizard, endemic to the Highveld grasslands of South Africa. Autopsy and mark-recapture methods were used to study the female reproductive cycle. Although reproduction was distinctly seasonal, most mature females reproduced biennially, with 53 % of the females not reproducing in a given year. Vitellogenesis commenced in late summer (February), and continued through winter hibernation to culminate in ovulation during spring (October). The onset of vitellogenesis correlated inversely with both ambient temperature and photoperiod. Reproducing females were pregnant for most of the summer and gave birth in late summer (January-February). At the onset of vitellogenesis, fat body mass was generally small in all females but smallest in late-gravid and nonreproductive females. Only in vitellogenic females did the fat body mass increase significantly prior to hibernation. These data are consistent with the hypothesis that biennial reproduction is determined by the magnitude of energy reserves at the onset of vitellogenesis and that the potential for annual reproduction remains in any year.