Physiological changes during the ovarian cycle of the female rock lizard, Agama atra (Sauria: agamidae)

Abstract

Seasonal morphometric and physiological changes associated with vitellogenesis in the female agamid lizard, Agama atra are described. Vitellogenic activity during August - September marked the onset of the breeding season. It is suggested that at least two clutches were ovulated during the breeding season. Large abdominal fatbodies deposited prior to the winter months were possibly utilized to meet metabolic demands during winter and the onset of vitellogenesis during early spring (August - September). Follicular growth and fatbody deposition coincided with low plasma cholesterol levels. The liver index and total plasma proteins did not show a clear seasonal pattem. Of the seven plasma protein fractions, Fraction 2 ('human beta-globulin' mobility) increased during vitellogenesis while the foremost migrating proteins ('human albumin' mobility) showed a compensatory decrease. Total plasma calcium levels increased during vitellogenesis. The oviducts remained hypertrophied throughout the breeding season, while progesterone levels increased following each ovulation cycle in the presence of corpora lutea and remained elevated until oviposition. The onset of the second vitellogenic cycle (December) coincided with high progesterone levels.