Oogenesis and ovarian histology of the South American lizard Salvator merianae

Abstract

The morphology of oogenesis in lizards has been described in few species. In this paper the ovarian histology of females of the S. merianae oviparous South American lizard is studied throughout the annual cycle. For this, ovaries were processed at different stages of the follicular cycle, using conventional histological technique. Two germinal beds were identified per ovary, from where the previtellogenic follicles emerge, present throughout the entire annual cycle. At this stage, the oocyte increases in size and the follicular epithelium change from a single layer of flat cells to a polymorphic and stratified layer, with three cell types: small, intermediate, and pyriform cells. At the beginning of the reproductive stage, vitellogenic follicles were found, showing a marked decrease in follicular epithelium, which was reduced to a single layer of flat cells. The incorporation of vitello resulted in a dramatic increase of oocyte size, reaching diameters close to 2,5 cm. After ovulation, the corpus hemorrhagicum showed the permanence of the thecal envelopes and follicular cells and the invasion of blood cells. The finding of corpus luteum with cells of steroidogenic characteristics 41 days after oviposition, leads us to propose that in this species the luteal bodies would present a functional persistence superior to that usually described for oviparous vertebrates