The ovarian structure and oogenesis in the Podarcis siculus lizard: a comprehensive overview spanning over sixty years

Oogenesis in oviparous vertebrates begins with a clustered gonad, a structure that may appear simple at first glance, but which conceals a certain complexity in the differentiation of follicles and the maturation of germ cells. The primordial follicle, originating from the germinal bed, undergoes a series of morphological changes involving both follicular cells and oocytes. This differentiation process requires a coordinated interplay between intrinsic factors and extrinsic signaling molecules. In this review, the process is described thanks to the research conducted over the years on the wall lizard Podarcis siculus. Overall, these studies have enabled the identification of the precise phases and molecules underlying follicular differentiation, the formulation of a hypothesis regarding the biseasonal origin of a currently annual reproductive cycle, and the recognition of the factors contributing to damage to the reproductive cycle of terrestrial oviparous vertebrates, caused by physical events such as temperature variations and chemical events such as environmental pollutants and endocrine disruptors.