Caracterização morfológica e imuno-histoquímica de receptores hormônio-esteroidais no sistema reprodutivo de machos de Potamotrygon wallacei (Chondrichthyes - Potamotryogoninae)

Abstract

The cururu Stingray Potamotrygon wallacei is endemic to the Middle Rio Negro basin and the smallest species among the potamotrygonins. Males present reproductive activity during the high and descending waters of the river. Previous studies have shown the influence of steroid hormones on gonadal and attached ducts development in adult males. Testosterone (T) is the primary steroid controlling testicular development and sperm production. On the other hand, progesterone (P4) seems to act during spermatogenesis and in the processes of maturation and sperm storage. However, these morphological and hormonal associations were performed by correlating the levels of steroids in plasma with the observed morphological changes without attributing a clear function to the steroidogenic cells and the real target of the steroids. In this context, this thesis investigated the ultrastructure of the reproductive system of mature males, exploring over two chapters the presence and capacity of steroidogenic cells in the production of T in the testis. In addition, analyzed the relation of P4 to attached ducts for sperm maturation and sperm aggregates formation in P. wallacei males. Samples of the reproductive system of adult males in two different reproductive stages were obtained and processed for analysis of their ultrastructure and immunohistochemical analyses. In the first chapter, the ultrastructure of steroidogenic cells and the immunolocalization of the enzyme 17-beta- hydroxysteroid dehydrogenase type 3 (17β-HSD3) were analyzed, observing the ability of these cells to T production. The second chapter describes the morphology of the different accessory ducts of the reproductive system, analyzing the progesterone receptors (PR) and relating them to sperm maturation processes and the formation of sperm aggregates. Finally, the results obtained in this thesis expanded the knowledge about the endocrinological processes involved in the reproduction of Neotropical freshwater stingrays (subfamily Potamotrygoninae). These data may help to elucidate the reproductive mechanism of this species, expanding information on the reproductive endocrinology of elasmobranchs.