Folliculogenesis and ovarian histology of the oviparous gecko, Hemidactylus mabouia (Sauria: Gekkonidae)

Abstract

Histological changes during the ovarian cycle of the oviparous gekkonid lizard, Hemidactylus mabouia are described. The ovaries each contained a single germinal epithelium (bed) with numerous oogonia and primordial follicles. Similar to other squamates, the ovarian stroma was characterized by follicles in different stages of development, and may contain corpora lutea, and corpora atretica. The seasonal study revealed that vitellogenic ovarian hypertrophy commenced in spring (September) and ovulation of the first clutch (two eggs) occurred in summer (November). A second vitellogenic cycle followed, the second clutch being ovulated in late‐summer (January). Ovarian quiescence, marked by predominance of pre‐vitellogenic (hydration stage) follicles, was evident in females collected from February to July. Although oocyte growth was accompanied by changes in the granulosa layer, zona radiata and thecal layers, the zona pellucida remained unchanged throughout. The small cells of the granulosa layer differentiated into three distinct cell types ‐ small, intermediate and the conspicuous large pyriform cells. Similar to most other squamates, the intermediate and pyriform cells at the onset of vitellogenesis regressed to a single cuboidal epithelium. Following ovulation, the granulosa layer hypertrophied forming luteal tissue. The theca layer differentiated into two layers and septal invasion of the corpus luteum took place. At the time of oviposition, corpora lutea regressed to form ovarian scars (corpora albicantia). Follicular artresia occurred in previtellogenic follicles (hydration stage) and seldom in vitellogenic follicles. The highest incidence of atresia occurred in the post‐breeding period (February). The gross morphology, oogenesis and folliculogenesis of the ovaries of H. mabouia correspond to the general squamate pattern described for oviparous reptiles.