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

Abstract

Ultrastructure of sperm storage in female soft-shelled turtle, Trionyx sinensis was examined under light and electron microscopes. Sperm storage tubules are restricted to the anterior of the uterus. These tubules developed either by folding or fusion of the oviductal mucosal folds and are lined by both ciliated and secretory cells. Ciliated cells are characterized by a few microvilli and prominent cilia in the apical membranes. A prominent feature of the secretory cell is the presence of secretory granules in the supranuclear region. The size, shape, and electron density of these granules vary markedly. The secretory product is released mainly by exocytosis into the oviductal lumen, where it appears as flocculent material. The unique structure in the base of the epithelium, the basal border of the cell-the basal lamina-and a blood vessel layer, is presumed to be a important barrier, by which the nourishment exchange and the microenvironment maintenance are ensured. The gland cell is presented with numerous, round, membrane-bound secretory granules of moderate to high electron densities. We divide these granules into three types according to their appearance: (1) membrane bounded granules with high-homogeneous electron density, (2) membrane bounded granules with moderate-homogeneous electron density, (3) membrane bounded, electron dense granules with concentric structures. These granules are presented as different stages of the secretions in the gland cell. The junction complexes are markedly distributed between cells, which are important in keeping stability and the microenvironment maintenance of the sperm storage tubules. Sperm stored in the tubules are heterogeneous in cytology. In addition to the mature sperm in the lumen, sperm with large chromatic granules are found, which are presumed to be immature sperm and are being in the process of nuclear condensation. Several spermatozoa in the tubules are exhibited with definitive indications of degeneration of the nuclei. The nuclear volume increases. The electron density of the central cores in mitochondria declines, combined with the deterioration of concentric membrane structure. Those changes are possibly due to the long time storage of the sperm in sperm storage tubules, and the leakage of reactive oxygen species is suggested to be a major cause. We conclude that the ultrastructure character of sperm storage in the oviduct

Ultrastructural Features of Sperm Storage Tubules in the Oviduct of the Indian Garden Lizard, Calotes Versicolor

“…Sever and Ryan, () proposed a dual origin for the carrier matrix. The present ultrastructural study of SSTs in C. versicolor shows the presence of copious amounts of secretory material released from the secretory cells lining the SSTs, as such supporting the theory of Han et al, (). The nature of the abundant secretory material and its possible role in sperm sustenance are currently under investigation.…”

“…Moreover, the exact nature of the “carrier matrix,” its origin and possible roles are yet to be understood. The presence of immature and degenerating spermatozoa in the storage tubules has been reported in reptiles and amphibians (Sever ; Han et al, ). However, in the present study the stored sperm was normal with a structural integrity.…”

Post‐ejaculatory modifications to sperm (PEMS)

“…In the Chinese soft‐shelled turtle, Pelodiscus sinensis , spermatogenesis is seasonal and, following spermiation, sperm spend many months within the male epididymis and the female oviduct, respectively (Zhang et al ., ). The epithelial cells of both tissues have distinctive secretory functions that are believed to contribute to the protection and nourishment of sperm (Han et al ., ; Bian et al ., ). In mammals, the complex epithelial folds, channels, microgrooves and mucous of the FRT create a highly selective environment through which sperm must navigate, significantly reducing the population of sperm that enter the oviduct from the uterotubal junction (Coy et al ., ; Holt & Fazeli, , ; Tung et al ., ).…”

Hormones and the Sex Ducts and Sex Accessory Structures of Reptiles

“…This ability is not unique to reptiles, being common in birds, but reptiles as a group store sperm for longer periods than other vertebrates, up to several years, for example, in turtles (Gist & Jones, 1987). An infundibular location of sperm storage is found in the soft-shelled turtle L. punctata (Sarkar, Sakar, & Maiti, 2003) and an anterior uterine location has been reported in another soft-shelled turtle, Trionyx sinensis (Han et al, 2008). The locations of sperm storage within the oviduct are highly variable.…”

“…It has yet to be established whether the host glands or tubules provide sustenance for stored spermatozoa, although Han et al (2008) reported both sperm maturation and degradation within storage tubules. In some reptiles, stored sperm are found in association with an amorphous carrier matrix (Halpert, Garstka, & Crews, 1982;Kumari, Sarkar, & Shivanandappa, 1990;Sarkar et al, 2003).…”