Structural analysis of toad oviductal mucosa in relation to jelly components secretion throughout the reproductive cycle

Abstract

Summary In amphibians, the components of the jelly coats that surround the oocytes at the time of fertilization and coordinate gamete interaction are secreted by the oviduct. We analysed the histological variations in the mucosa of the oviductal pars convoluta (PC) of Rhinella arenarum during the reproductive cycle and its relationship with secretion. During the preovulatory period, the mucosa reaches a high degree of morphological and functional development, with a large number of epithelial (ESC) and glandular secretory cells (GSC) loaded with contents that are secreted into the oviductal lumen. During the ovulatory period, the secretory cells (SC) of both layers present maximum secretory activity through apocrinia and merocrinia. While the ESC located at the tips of the folds release their content directly in contact with the oocytes, the GSC secrete material from the bottom of the epithelial folds that, by interaction with the secretion of the ESC in the lateral faces, form a product with a certain degree of organization. Secretion is a continuous process with formation of coats of increasing complexity from the intermediate proximal zone (IPZ) to the pars convolute (pc) itself, and the passage of the oocyte is a requisite for the organization of the jelly coats around the gamete. During the early postovulatory period, although there is a marked decrease in the number and volume of the SC, the ESC still release material into the oviductal lumen. In the late postovulatory period the morphological characteristics of the PC begin to recovery although there is no evidence of secretion.