Morphology of the reproductive tract and acquisition of sexual maturity in males ofPotamotrygon magdalenae(Elasmobranchii: Potamotrygonidae)

Abstract

The purpose of this study was to describe the structure of the reproductive tract of males of Potamotrygon magdalenae before, during, and after they acquire sexual maturity, and to establish the first maturity scale for males within the family Potamotrygonidae. The male reproductive tract of P. magdalenae is composed of testes, efferent ducts, epididymides, deferent ducts, seminal vesicles, Leydig, alkaline, and clasper glands, and claspers, all of which are paired and functional. Four sexual maturity stages were established: immature, maturing, reproductively active, and resting. The degree of claspers calcification is also a good indicator of sexual maturity in this species. The testes are lobulated, each lobe contains numerous spermatocysts which are organized in zones and are displaced radially from germinal papillae to the spermatozoa zone where individual spermatozoa are conveyed to the efferent ducts. The epididymis can be regionalized in head, body, and tail; these regions are distinguished by external pigmentation and by the epithelium lining configuration. The tail of the epididymis is connected with the deferent duct and this, in turn, with the seminal vesicle. The spermatozoa are organized in spermatozeugmata which begin to form in the deferent duct; this latter organ is attached laterally at the Leydig gland that is composed by simple glandular units. Irregular and vesicular secretions can be found in the genital ducts. These secretions might be associated with the maturation of the spermatozoa and formation of spermatozeugmata. The male reproductive tract of P. magdalenae is similar to other elasmobranchs; however, two types of primary spermatogonia, an epididymis internally regionalized, and the presence and structure of spermatozeugmata are specific features not yet described in freshwater stingrays. Most of the year, the males were reproductively active, however, few resting adult males occurred during one of the months of the lowest waters.

Sperm of Galeorhinus galeus (Elasmobranchii, Triakidae) Traverse an Excurrent Duct System Characterized by Pronounced Regionalization: A Scanning Electron and Light Microscopy Study

“…Here we present evidence of pronounced regionalization of the intratesticular and extratesticular excurrent duct systems of Galeorhinus galeus, with some of the observations being described for the first time for mating chondrichthyans. Whether or not some of the novel findings reported here reflect different physiological states, for example, breeding versus non-breeding (Jones and Jones, 1982;Piercy et al, 2003) or actual species differences, for example, sharks versus rays (Babel, 1967;Chatchavalvanich et al, 2005;Henderson et al, 2014;Del Mar Pedreros-Sierra and Ram ırez-Pinilla, 2015) is unclear. These considerations, together with the widely varying sampling and dissection protocols employed in other studies, and the novel approach employed in the present study of microscopically examining 20 sequential blocks of tissue excised from the entire epididymis, certainly make comparisons across species difficult.…”

Clasper gland morphology and development inPotamotrygon magdalenae(Elasmobranchii: Potamotrygonidae)

“…Thirty one (31) individuals of Potamotrygon magdalenae (Duméril, 1865) were collected in total [9 immature or neonates (Stage 2), 3 maturing or juveniles (Stage 3), 12 mature reproductively active (Stage 4) and 7 mature resting males (Stage 5)], during one year (August 2010 to September 2011) using cast nests and trammel; these were collected at the Ciénaga de Paredes, a swamp located in Puerto Wilches municipality, Department of Santander, Colombia (Latitude: 7.44472, Longitude: −73.7714). They were submerged in a lethal dose of 1% Lidocaine and fixed in 10% formaldehyde (see details in Pedreros‐Sierra and Ramírez‐Pinilla, ). The reproductive stage in which each male was found and its respective disc width size were obtained from the data provided by Pedreros‐Sierra and Ramírez‐Pinilla ().…”

“…They were submerged in a lethal dose of 1% Lidocaine and fixed in 10% formaldehyde (see details in Pedreros‐Sierra and Ramírez‐Pinilla, ). The reproductive stage in which each male was found and its respective disc width size were obtained from the data provided by Pedreros‐Sierra and Ramírez‐Pinilla (). These authors combined gross examination with histological analyses of reproductive organs (testes, epididymis, Leydig glands and seminal vesicles; additionally, the degree of calcification of the claspers was determined and classified as noncalcified, partially calcified and calcified) to determined sexual maturity stages and reproductive activity of males of P. magdalenae .…”

“…Detailed descriptions about the development and morphology of clasper glands in species of this family are unknown. Males of this species are reproductively active during the entire year, although a few males were found in resting reproductive stages (the production of both germinal cells and secretions by male reproductive tract are temporally halted) during the driest month of the year (February; Pedreros‐Sierra and Ramírez‐Pinilla, ). Studying specimens from neonates to adults, four reproductive stages were identified for the males of this population: immature, maturing, active and resting adults; additionally, clasper calcification is a good indicator of sexual maturity (Pedreros‐Sierra and Ramírez‐Pinilla, ) as in other elasmobranchs (Friedman, ; Hamlett et al, ).…”

“…Males of this species are reproductively active during the entire year, although a few males were found in resting reproductive stages (the production of both germinal cells and secretions by male reproductive tract are temporally halted) during the driest month of the year (February; Pedreros‐Sierra and Ramírez‐Pinilla, ). Studying specimens from neonates to adults, four reproductive stages were identified for the males of this population: immature, maturing, active and resting adults; additionally, clasper calcification is a good indicator of sexual maturity (Pedreros‐Sierra and Ramírez‐Pinilla, ) as in other elasmobranchs (Friedman, ; Hamlett et al, ). In the present study, we describe the morphology and histology of the clasper glands and their development in this population of P. magdalenae , the histochemical nature of the secreted fluids and relate the size of the gland and the production of the fluids with the male reproductive stage.…”