Ovarian follicular cycle of Tropidurus hispidus and Tropidurus semitaeniatus (Squamata: Tropiduridae) in a semiarid region of Brazil

The reproductive cycle of Squamata reptiles is often associated with environmental conditions, such as rainfall. In this respect, seasonal variations may affect the morphology of the ovarian follicles, which are associated with vitellogenesis. The present study describes histological alterations in the ovarian cycle of two lizard species, Tropidurus hispidus (Spix, 1825) and Tropidurus semitaeniatus (Spix, 1825), which inhabit a caatinga region in the state of Rio Grande do Norte. Our goal was to identify morphological differences in the ovarian follicles at each phase of vitelloge nesis and to ascertain if they are associated with rainfall. Three follicular phases were identified in both species: pre-vitellogenesis, vitellogenesis and follicular atresia. An additional phase, the luteal, was found only in T. hispidus. During the development of these phases, vitellus was deposited inside the oocyte and there were identifiable alterations in the granulosa and thecal layers. Rainfall was found to influence the gonadal cycle.