Development of the germinal epithelium and early folliculogenesis during ovarian morphogenesis in the cichlid fish Cichlasoma dimerus (Teleostei, Perciformes).

MEIJIDE, F.; REY VAZQUEZ, G.; GRIER, H.; LO NOSTRO, F.; GUERRERO, G.

ACTA ZOOLOGICA

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 97 p. 18 - 33

0001-7272

Formation of the germinal epithelium and folliculogenesis during ovarian development in 22 Cichlasoma dimerus were described at the light- and electron-microscopic levels. Prior to 23 gonadal differentiation, germ cells and enveloping support cells reside within an 24 inpocketing of the coelomic epithelium. Separation of the germinal and interstitial 25 compartments of the gonad by a basement membrane is apparent from early gonadal 26 development. Upon ovarian differentiation, oogonia undergo cyst-forming divisions leading 27 to the formation of clusters of interconnected cystocytes that synchronously enter meiosis, 28 becoming oocytes. At the pachytene step, each oocyte becomes individualized by 29 cytoplasmic extensions of prefollicle cells, thereby developing as an ovarian follicle. 30 Subsequent somatic reorganization leads to the formation of the ovarian lumen in a 31 cephalo-caudal gradient. As a result, the germinal epithelium becomes internalized and 32 lines the ovarian lumen. As defined by its origin from the germinal epithelium, the ovarian 33 follicle is composed of an oocyte and the surrounding follicle cells. Thecal cells derived 34 from the stroma encompass the basement membrane outside the follicle, thus forming a 35 follicle complex. A common basement membrane is shared by the germinal epithelium and 36 the follicle complex along a small portion of its surface. This point of attachment represents 37 the site at which the oocyte would be released to the ovarian lumen during ovulation.