Microanatomy of the female reproductive system of the viviparous freshwater whipray Fluvitrygon signifer (Chondrichthyes: Myliobatiformes: Dasyatidae). II. The genital duct.

BACKGROUND: Fundamental knowledge on microscopic structures of the whole female chondrichthyan genital ducts from a single species remains unavailable. The present study describes microanatomy of the entire female genital duct (anterior oviduct, oviducal gland, uterus and vagina) of the freshwater dasyatid Fluvitrygon signifer. RESULTS: The females have only the left genital duct. The genital ducts reveal histological variation among individuals in terms of tissue organization, histochemical profiles and secretory activities. The anterior oviducts of mature females possess branched mucosal folds and exhibit dynamic relationship between production and secretion of secretory substances, while those of immature/regenerating females have short, unbranched mucosal folds and inactive secretory activities. The oviducal gland comprises glandular tubules, which show histological and histochemical heterogeneity and, thus, can be classified into three types. The uterus is categorized into five patterns principally based on histological features of the trophonematal and uterine mucosa. The vagina displays different histochemical reactions, likely reflecting various degrees of glycosylation of secretory granules. CONCLUSIONS: The genital ducts of the females of F. signifer show differential microscopic and histochemical characteristics, indicating their different reproductive statuses.

Effect of progesterone administration on the distribution of oviductal carbohydrates in Rana tigrina.

Our aim has been to determine whether carbohydrate distribution in the oviducts of progesterone-treated animals is comparable with that of seasonal breeders in Rana tigrina. Like many other anurans, R. tigrina oviduct exhibits a short straight portion (pars recta, pr) at the beginning followed by a long, highly coiled portion (pars convoluta, pc). Histologically, the oviduct of this species revealed some unique features, one of which was intense toluidine blue staining, specifically in the upper mucosal glands of pc4. Based on lectin reactivities in the epithelial cells and mucosal glands, patterns of lectin staining in the seasonal breeders were classified into seven types: R1-R3 (for pr) and C1-C4 (for pc). Typically, some lectins reacted selectively either with ciliated cells (concanavalin A) or non-cialiated cells (Ricinus communis agglutinin I and wheatgerm agglutinin); however, Bandeiraea simplicifolia agglutinin I reacted with both cell types. These staining patterns were different in the progesterone-treated animals. Differences in glycan distribution in the oviductal secretions were revealed by lectin blotting. Compared with the seasonal breeders, an enhanced staining of some lectins was noted in the hormone-treated animals: either an increased staining intensity of existing protein bands or additional staining of new protein bands. Inversely, the staining of wheatgerm agglutinin was markedly diminished in the hormone-treated animals, suggesting the inhibitory effect of progesterone on oviductal glycan distribution. Whether alteration in glycan distribution upon progesterone treatment affects the physiological properties of the released jelly substances remains to be addressed.

Histology of the digestive tract of the freshwater stingray Himantura signifer Compagno and Roberts, 1982 (Elasmobranchii, Dasyatidae).

We investigated the histology and histochemistry (of carbohydrates and proteins) of the digestive tract of the freshwater stingray Himantura signifier. The alimentary tract consists of a mouth, pharynx, esophagus, stomach (with a descending cardiac and ascending pyloric part), anterior intestine (with an initial portion and a spiral intestine) and posterior intestine, ending in a cloaca. Histologically, three layers--mucosa, muscularis and adventitia/serosa--were defined from the mouth to esophagus and in the posterior intestine, whereas in the stomach and anterior intestine four layers were present, including a submucosa. The epithelial lining of mouth, pharynx and cloaca was of the stratified cuboidal type, whereas that of the esophagus and posterior intestine was stratified columnar. The stomach and anterior intestine were lined by a simple columnar epithelium with microvilli. Goblet cells were observed along the alimentary tract, except in the stomach. In the descending cardiac portion of this organ, gastric glands composed of oxyntic, oxyntic-peptic and peptic cells were observed. The anterior intestine presented a spiral valve with 11 folds, formed by mucosa and submucosa. The posterior intestine was particular in displaying a three-layered muscularis. Mucosubstances secreted along the alimentary tract contained both neutral and acid mucins, but in the stomach only neutral mucins were detected. The stomach presented intense protein content in the epithelial lining of the gastric pits. Enteroendocrine cells were identified in the stomach and intestine. Overall, our data offer a baseline for comparative purposes and future detailed ultrastructural and immunohistochemical studies.