Fine structural observation on the oogenesis and vitellogenesis of the Chinese soft-shelled turtle (Pelodiseus sinensis)

Abstract

Fine structure observations were performed by means of electron microscopy on oogenesis and vitellogenesis and the special functions of follicular cells in the Chinese soft-shelled turtle (Pelodiseus sinensis). Histological examination of the ovary showed a well developed lacunae system containing fine granules, fibres or gelatiniform materials with one or two germinal beds dispersed on the dorsal surface of the ovarian cortex. The process of oogenesis comprised 10 consecutive phases according to the morphology of the yolk platelets, follicular cells and zona pellucida (ZP). Electron microscopy of vitellogenesis revealed some of the mitochondria gradually being transformed into yolk granules. In the advanced stage of vitellogenesis, large amounts of rough endoplasmic reticula, Golgiosomes and other cell organelles that are involved in synthesis and secretion were observed in follicular cells. The ZP was formed by microvilli, thus increasing the absorptive surface of the oocyte and facilitating transport of nutrients from the follicular epithelium to the ooplasm. This study demonstrated that the ovaries of members of the Testudinidae share more features with Archosaurs than with Squamates, indicating that these features were phylogenetically conserved in the Archosauria. The present observations suggest that the accumulation of yolk materials was controlled by the intrinsic and extrinsic pathways as well as by the activity of follicular cells. These results might also support a sibling relationship of the Testudinidae with the Archosauria and not with all extant reptiles.

Ribosomal RNA gene functioning in avian oogenesis

“…The authors considered this as evidence of rDNA amplification. A similar situation seems to be typical of NOR activities in growing oocytes of crocodile (Uribe and Guillette 2000;Moore et al 2008) and turtle (Nainan et al 2009;Pérez-Bermúdez et al 2012). In these animals, which are phylogenetically the closest to birds, a single nucleolus has been observed in the small oocyte nucleus; in later lampbrush oocytes, multiple free nucleoli have been found located under the nuclear envelope.…”

Sperm storage and spermatozoa interaction with epithelial cells in oviduct of Chinese soft‐shelled turtle, Pelodiscus sinensis

“…2007; Nainan et al. 2010). However, there is still a limited knowledge on oviductal sperm storage, an important reproductive strategy in the turtle.…”

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

“…Histologically, the ovary is an elongated structure formed by a cortex and a medulla. 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.…”

“…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).…”