PHYSIOLOGICAL-CHANGES DURING THE FEMALE REPRODUCTIVE-CYCLE OF THE VIVIPAROUS LIZARD CORDYLUS-GIGANTEUS (SAURIA, CORDYLIDAE)

Seasonal morphometric and physiological changes associated with a bien nial reproductive cycle in female Cordylus giganteus are described for a 15-mo period. Cordylus giganteus is a large terrestrial, viviparous lizard endemic to the Highveld grasslands of South Africa. Vitellogen esis commences in autumn (January-February) and continues through wint er hibernation to culminate in ovulation during spring (October). Live r and oviducal hypertrophy coincide with pronounced increments in plas ma calcium, inorganic phosphate, and estradiol-17beta in advanced vite llogenic females. Total plasma protein concentration did not show a cl ear seasonal pattern. Clutch size ranges from 1-3 young and is not aff ected by female body size. Females are gravid during summer and give b irth in late summer (January-February). During embryonic development, ovarian follicles remain small and translucent, and the diameters of t he corpora lutea decrease prior to parturition. Plasma progesterone le vels increase in gravid females to peak in the second trimester of pre gnancy. The oviducts remain hypertrophied throughout pregnancy and dec rease in mass during the nonreproductive period. Nutritional exchange between female and embryos is suggested during late stages of embryoni c development, in light of the 130% net increase in embryonic dry mass when compared to ovulated yolk mass. I discuss the variation in physi ological variables among female reproductive categories, with special reference to biennial reproduction.