Morphological changes in the oviductal endometrium during the reproductive cycle of the tortoise,Gopherus polyphemus

Abstract

The oviducts of 24 tortoises (Gopherus polyphemus) were examined using histological techniques and scanning electron microscopy to determine endometrial morphology. Measurements of endometrial characteristics (epithelial cell height, cilia length, thickness of endometrial glandular layer, and glandular diameter) in the uterus and tube (tuba uterina) were obtained to determine changes during the reproductive cycle. Epithelial cell height increases in both the uterus and the tube during vitellogenesis and remains hypertrophied during gravidity. Cilia length increases in the uterus during late vitellogenesis and gravidity, but the length of tubal cilia does not change during the reproductive cycle. The ratio of secretory to ciliated epithelial cells in the oviduct increases from quiescence to gravidity. The thickness of the glandular endometrial layer increases in both the uterus and tube during vitellogenesis. In the uterus, the glandular layer decreases in thickness during gravidity. The diameter of the uterine glands increases throughout vitellogenesis and gravidity; however, following ovulation glandular cells become depleted of secretory granules and cell height diminishes. The diameter of the tubal glands is unchanged during the reproductive cycle. Oviductal hypertrophy during vitellogenesis coincides with elevated circulating estradiol, whereas during gravidity progesterone concentrations peak (Taylor, '82, PhD Dissertation, University of Florida, Gainesville) and may induce secretion of albumen and eggshell components.

Ultrastructure of Anterior Uterus of the Oviduct and the Stored Sperm in Female Soft‐Shelled Turtle,Trionyx sinensis

“…Therefore, it is speculated that the dense electron granules with no concentric lamellae are immature ones that are developed from membrane-bound granules with moderate electron density. The materials in all these granules might also have its function to form eggshell fibers similar to those of turtle, Pseudemys s. scripta (Palmer and Guillette, 1990). However, no internal ultrastructures such as we have observed has been reported in turtles as well as other reptiles.…”

“…A primary role of secretory cell in reptiles has earlier been reported in Gopherus polyphemus (Palmer and Guillette, 1990) and in some others (Guillette et al, 1989), which was suggested to have a function in secretion of the calcareous layer of egg shells. In present study, the electron density of secretory granules in secretory cells changes obviously, indicating a matrix solution process, by which the nonsoluble calcareous materials is modified and become dissolved.…”

Hematology and Plasma Biochemistry Reference Range Values for Free-Ranging Desert Tortoises in Arizona

“…Unlike Mojave desert tortoises, Sonoran tortoises are monestrous, laying a single clutch of eggs each year (Murray et al, 1996). In addition, Palmer and Guillette (1990) found increased levels of ESTR during vitellogenesis in free-ranging gopher tortoises.…”

Localization of insulin‐like growth factor‐I‐like immunoreactivity in the reproductive tract of the vitellogenic female American alligator, Alligator mississippiensis

“…The term "oviduct" is used here to refer to the entire structure derived from the embryonic Mullerian duct. Turtles, lizards, snakes, and tuatara have oviducts divided into two distinct regions: an anterior tube that secretes the egg albumen and a posterior uterus that secretes the proteinaceous fibers and calcium of the eggshell (Guillette et al, 1988;Palmer and Guillette, 1989; Cree and Guillette, unpub data). In contrast, although neonatal alligators exhibit no regional specialization of the oviduct (Austin, 1990), sexually mature females (those > 1.8 m in length) have an oviduct differentiated into three structurally and functionally distinct regions: a tube region that secretes albumen and a uterus divided into an anterior, fibersecreting region and a posterior, calcium-secreting region (Palmer and Guillette, 1992).…”