Chapter 3: Oogenesis

SÁNCHEZ S. S.; VILLECCO E.I.

Reproductive Biology and Phylogeny of Anura

Sciences Publishers Inc.

Año: 2003; p. 27 - 71

Oogenesis is a complex process that leads to the formation and differentiation of the female gamete. Within the gonad, the development of each gamete is mainly mediated through the follicles which undergo progressive cellular and molecular interactions (Fig. 26). One of the most relevant events in amphibian oogenesis is the marked gene expression and accumulation of transcripts during primary oocyte growth. The high pattern of accumulation of different RNAs is related to the requirement for stored components to be used in early development. Besides RNAs, oocytes store components to meet all nutritional requirements of the embryo until it is able to consume food. Thus, a large number of yolk platelets accumulate during the vitellogenic phase. When the oocytes complete their growth in the ovary (full grown oocytes) they are arrested at the prophase of meiosis I. However, they are not able to be fertilized or support embryonic development unless they undergo oocyte maturation. This process corresponds to a complex differentiation program that transforms the oocyte into an egg that is fertilization competent.