Morphological changes in the clasper gland of the Atlantic stingray,Dasyatis sabina, associated with the seasonal reproductive cycle

Reproductive Anatomy of Chondrichthyans: Notes on Specimen Handling and Sperm Extraction. I. Rays and Skates

Simple Summary

Many species of rays and skates are endangered, and ex situ conservation programs developed by research centers and public aquaria could improve this situation. To reproduce these species in captivity, scientists need to know how to extract their sperm and how to conduct their artificial insemination; however, the anatomical diversity of the reproductive organs of this group of animals is a handicap. A comparison of the reproductive anatomies of 11 distinct species is presented here, emphasizing the important differences between the species when performing sperm extraction or artificial insemination. In addition, the process of obtaining sperm samples from both live and dead males is described in detail, using both cannulation and abdominal massage.

Abstract

The superorder Batoidea (rays, skates, and relatives), constitutes one of the most threatened group of vertebrates. Strengthening ex situ conservation programs developed in research centers and public aquaria could be a way of addressing this situation. However, captive breeding programs must be improved to prevent the capture of wild animals and to develop proper in situ reintroduction strategies. Sperm extraction and artificial insemination are two techniques commonly used in other threatened species, which could also be used in rays and the like. However, the different reproductive morphologies present within this group of animals may hamper both processes. Here, we present a comparison of the reproductive anatomies of 11 distinct batoid species, emphasizing the important differences between the species when performing sperm extraction or artificial insemination. Both male and female animals, belonging to the Rajidae, Dasyatidae, Torpedinidae and Myliobatidae families, from the Mediterranean Sea were studied. In addition, we describe the procedure to extract sperm using both cannulation and abdominal massage, either from live or dead batoids Finally, the obtention of motile sperm recovered from the oviducal gland of females is described. These techniques generate a new range of possibilities for the conservation of these threatened species.

Evidence for mouse sulfhydryl oxidase-assisted cross-linking of major seminal vesicle proteins

Copulatory plug formation in animals is a general phenomenon by which competition is reduced among rival males. In mouse, the copulatory plug formation results from the coagulation of highly viscous seminal vesicle secretion (SVS) that is rich in proteins, such as dimers of SVS I, SVS I + II + III, and SVS II. These high-molecular-weight complexes (HMWCs) are also reported to be the bulk of proteins in the copulatory plug of the female mouse following copulation. In addition, mouse SVS contributes to the existence of sulfhydryl oxidase (Sox), which mediates the disulfide bond formation between cysteine residues. In this study, flavin adenine dinucleotide (FAD)-dependent Sox was purified from mouse SVS using ion exchange and high-performance liquid chromatography. The purified enzyme was identified to be Sox, based on western blot analysis with Sox antiserum and its capability of oxidizing dithiothreitol as substrate. The pH optima and thermal stability of the enzyme were determined. Among the metal ions tested, zinc showed an inhibitory effect on Sox activity. A prosthetic group of the enzyme was identified as FAD. The K_m and V_max of the enzyme was also determined. In addition to purification and biochemical characterization of seminal vesicle Sox, the major breakthrough of this study was proving its cross-linking activity among SVS I-III monomers to form HMWCs in SVS.

Reproductive biology of the Brazilian blind electric ray Benthobatis kreffti (Chondrichthyes: Narcinidae)

ABSTRACT This study provides information on the reproductive biology of the Brazilian blind electric ray Benthobatis kreffti, endemic to southern and southeastern Brazil. Individuals were caught by bottom trawl carried out in 2003 and 2007, at 492-501 m depth off the São Paulo State continental slope. A total of 152 females (115-299 mm) and 144 males (91-243 mm) were sampled. Maturity was first observed at 177 and 162 mm, with total length at 50% maturity of 191 and 176 mm in females and males respectively. Uterine fecundity ranged from 1-3 and was not related to female total length. Size at birth estimated from the largest near-term observed embryos and smallest free-swimming ray was 91-100 mm. The low fecundity observed is typical of deepwater elasmobranch species, as well as late maturity in comparison with costal species. The relatively large size-at-birth suggests that this species invests more in length of each embryo than in litter size, increasing the offspring’s survival chance. In this context, these parameters highlight the vulnerability of this and other deepwater species to non-natural death, mostly caused by deep-sea fisheries.

Reproductive biology of Psammobatis rutrum (Chondrichthyes: Arhynchobatidae) in south Brazil, south-west Atlantic

This study presents information on the reproductive biology of Psammobatis rutrum based on 55 males and 53 females obtained as by-catch from bottom trawlers off southern Brazil during July 2013 and September 2014 and includes a detailed description of the egg capsule. Total lengths (L_T ) ranged from 22·3 to 31·6 cm and most of the sample comprised larger individuals, although there were no sexual differences in length-frequency distributions. Significant sexual differences were found for total length-disc width, L_T -body mass and L_T -eviscerated body mass relationships, with females being heavier and larger. Males started to mature at 25·5 cm L_T and females, at 25·9 cm L_T , while L_T at maturity was calculated in 26·67 and 26·81 cm, respectively. Attaining larger sizes and mass may represent a reproductive investment for females, as observed in other rajoid species. Egg bearing females were first observed over 27·1 cm L_T and ovarian fecundity was 1-12 vitellogenic follicles. The egg capsules were 2·22-2·62 cm length and had attaching fibrils on both lateral sides. Microscopically, the ventral face of the egg capsule was rougher than the dorsal face.

Clasper gland morphology and development in Potamotrygon magdalenae (Elasmobranchii: Potamotrygonidae)

Clasper gland morphology and development in Potamotrygon magdalenae and its relation with the acquisition of reproductive maturity is described in males of different developmental stages (embryos, neonates, juveniles, and reproductively active and resting adults). The glands are subcutaneous masses in the proximal base of each clasper. They are partially bilobate organs with a ventral groove that bears a row of papillae. Glands tend to be asymmetric, the left gland has a larger size, a trend that has been observed in other organs of elasmobranchs. Glands are formed by radially organized tubular secretory units lined with a simple columnar epithelium with basal nuclei and granular eosinophilic cytoplasm; vascularized loose connective tissue surrounds the gland units. The gland is covered by two layers of striated muscle tissue in circular and longitudinal arrangement. The clasper glands begin to develop in neonates and their secretory activity begins in juveniles. The active secretion of the clasper gland is observed in mature males, it includes glycoproteins and sulfated mucopolysaccharides. The size of the glands has a positive and direct relationship with body size, measured as disc width. Significant differences in clasper gland size were found between mature (active and resting) and immature (neonates and juveniles) males, suggesting that the acquisition of the sexual maturity involves the increase in the size of the gland due to a highly augmented secretory activity. Therefore, clasper glands are clearly associated with the reproductive activity of males and their secretion should have an endocrine control as other sexual secondary organs. J. Morphol. 278:369-379, 2017. © 2017 Wiley Periodicals, Inc.

Reproductive biology of the stingrays, Myliobatis goodei and Myliobatis ridens (Chondrichthyes: Myliobatidae), in southern Brazil

This study, carried out between spring 2012 and winter 2014, characterized the sexual development and reproductive cycle of Myliobatis goodei and Myliobatis ridens in the extreme south of Brazil to support future management and conservation plans. Ninety-five specimens of M. goodei (24 males and 71 females) and 175 M. ridens (24 males and 151 females) were sampled. Female M. goodei attained disc-width-at-50% maturity (WD50 ) at 683 mm. Uterine fecundity was four to five embryos. The largest male recorded, a mature individual, had a disc width of 650 mm. In M. ridens, WD50 was 662 mm. Uterine fecundity varied from one to eight embryos. The largest male on record was a maturing 590 mm WD individual. The hepato-somatic index was higher in autumn in females of M. goodei, and in the summer in M. ridens. The gonado-somatic index and the largest vitellogenic follicle diameter were higher in spring in both species. Pregnant females of both species were recorded during spring, although for M. ridens, these females also occurred in summer. Embryos had WD of 61-218 and 40-236 mm for M. goodei and M. ridens, respectively. The incidence of pregnant females in southern Brazil in spring-summer coincides with the small-scale beach artisanal fisheries season peak, when M. goodei and M. ridens suffer fishing mortality, while using the coastal shallow areas in the warmer periods (spring-summer) to give birth.