Ovarian follicular development in the hawksbill turtle (Cheloniidae: Eretmochelys imbricata L.)

Abstract

Ovarian follicular development is an essential process in the determination of maturation stages associated with size. This association acquires importance when managing populations of threatened species. We histologically processed 11 prepubescent ovaries, four pubescent ovaries, and one breeding adult ovary with vitellogenic follicles using specific staining techniques to identify the follicular stages of Eretmochelys imbricata. Follicular stages were compared with maturation stages [including straight carapace length (SCL)]. The ovary presented several germinal beds and a lacunar system less histochemically and morphologically heterogeneous than that of crocodiles. During previtellogenesis (four stages), the oocyte grows rapidly due to the strong transcriptional activity of lampbrush chromosomes and numerous nucleoli, and the strong metabolism associated with lipid synthesis. The Stage III ooplasm showed a Sudan positive band. This stage was the most frequent in all ovarian sections and it was independent of maximal follicular stage. Stage IV, more frequent in pubescent and adult ovaries, presented a lipid vacuole-rich ooplasm and a broadening of the zona pellucida and the theca. The vitellogenesis begins with the penetration and accumulation of spherical glycoprotein yolk platelets and chemically neutral lipid droplets which are observed to be mixed, but spatially and chemically segregated. Both the yolk platelets and lipid droplets increase in size, density, and proximity to the periphery of the oocyte due to their coalescence. The SCL of the immature females did not determine the maximal follicular stage nor its frequency in the ovaries. Straight carapace length turned out to be an imprecise measure in identifying the presence of follicular stages in females larger than the minimum legal size limit in Cuba. Consequently, for a national conservation program to be successful, it must emphasize the critically endangered status of E. imbricata, as well as the maturity of the most frequent hawksbill sizes encountered in the Cuban archipelago fishery.

Histological description of the reproductive tract of male and female hatchlings of the Magdalena river turtle (Podocnemis lewyana).

“…4Cf), surrounded by flat follicular cells. Such development was classified as stage I of folliculogenesis in juvenile hawksbill sea turtles (Pérez-Bermúdez et al, 2012). On the other hand, the tubular structures of males and females were also found in an immature stage.…”

“…The cortex is formed by germinal beds and multiple developing follicular structures (Yntema, 1981;Callebaut et al, 1997;Hei et al, 2010;Pérez-Bermúdez et al, 2012). Germinal beds contain oogonia (primordial oocytes) and oocytes (Pérez-Bermúdez et al, 2012), which later will become a mature ovum to be fertilized when the female reaches sexual maturity. The ovarian follicular development includes three different stages: folliculogenesis, previtellogenesis and vitellogenesis, in which the oocyte increases its size gradually (e.g.…”

“…The ovarian follicular development includes three different stages: folliculogenesis, previtellogenesis and vitellogenesis, in which the oocyte increases its size gradually (e.g. from 19.2 µm to 24.9 mm in the hawksbill turtle, Eretmochelys imbricata, Pérez-Bermúdez et al, 2012). Deeper in the ovary is the medulla, which is composed of lymphoid lacunae, blood vessels, fibroblasts, collagen fibers, and smooth muscle (Callebaut et al, 1997;Hei et al, 2010;Pérez-Bermúdez et al, 2012).…”

“…from 19.2 µm to 24.9 mm in the hawksbill turtle, Eretmochelys imbricata, Pérez-Bermúdez et al, 2012). Deeper in the ovary is the medulla, which is composed of lymphoid lacunae, blood vessels, fibroblasts, collagen fibers, and smooth muscle (Callebaut et al, 1997;Hei et al, 2010;Pérez-Bermúdez et al, 2012). The size of the ovaries varies with age and the physiological state of the female, and follicles can develop in both ovaries at the same time (Callebaut et al, 1997).…”

Gonadal Differentiation in Reptiles Exhibiting Environmental Sex Determination

“…The number of germinal beds and morphology varies among reptilian species [Jones et al, 1982], but do not change over the lifetime of an individual [Radder and Shine, 2007]. Discrete single or multiple germinal beds have been characterized in squamate ovaries [Guraya and Varma, 1976;Hernán-dez-Franyutti et al, 2005;Moodley and van Wyk, 2007], whereas crocodilians and turtles possess clusters of oogonia (nests) distributed throughout the entire ovarian cortex, adjacent to previtellogenic follicles [Uribe et al, 1996;Uribe and Guillette, 2000;Calderón et al, 2004;Moore et al, 2010b;Pérez-Bermúdez et al, 2012]. As observed across squamate phylogenies, the number of germinal beds per ovary correlates with clutch size and resulting fecundity [Jones et al, 1982;Radder et al, 2008].…”