Oviducal Gland Research Articles

Low microbial abundance and community diversity in the egg capsule of the oviparous cloudy catshark (Scyliorhinus torazame) during oviposition.

Vertebrate embryos are protected from bacterial infection by various maternally derived factors, yet little is known about the defence mechanisms in elasmobranchs. This study aimed to characterize the intracapsular environment of freshly laid eggs of the oviparous catshark (Scyliorhinus torazame) by investigating the microbial abundance and microbiota to understand its potential contribution to embryonic defence. The egg capsule of oviparous elasmobranchs is tightly sealed until pre-hatching, after which seawater flows into the capsule, exposing the embryos to the surrounding seawater. We found that early embryos were highly vulnerable to environmental pathogens, suggesting that the embryos are somehow protected from infection before pre-hatching. Indeed, the intracapsular environment of freshly laid eggs exhibited significantly low bacterial density, maintained until pre-hatching. Furthermore, the microbiome inside eggs just after oviposition differed markedly from those of rearing seawater and adult oviducal gland epithelia; these eggs were predominantly populated by an unidentified genus of Sphingomonadaceae. Overall, this study provides compelling evidence that early embryos of oviparous cloudy catshark are incubated in a clean intracapsular environment that potentially plays a significant role in embryonic development in oviparous elasmobranchs.

Reproductive biology of the silky shark Carcharhinus falciformis (Müller & Henle, 1839) in waters off Côte d’Ivoire (West Africa)

Since 2008, the quantity and size of silky shark, Carcharhinus falciformis decrease drastically in catches of artisanal driftnet fishery operating in the coastal waters off Côte d’Ivoire. The objective of this study was to describe the reproductive biology of this species, based on 336 specimens (162 males and 174 females). The total length (TL) of males and female ranged from 81–242 and 79–254 cm respectively. The sex ratio was 0.89:1 (M:F) and 0.93:1 (M:F) in embryos and adults respectively. Males of >180 cm had calcified clasper (17–35 cm) whereas females of >190 cm had oviduct gland length of 18–47 mm. The estimated length at first maturity was 182.8 cm for males and 195.2 cm for females. The range in litter size of three gravid females was 7–9, with an average of 8 embryos of 52–54.5 cm TL were collected in August and December. However, the absence of neonates and scars on females' body, as well as ovulating and differentiating females in catches does not allow a clear determination of its reproductive period in Ivorian waters and therefore, additional research including histological analysis is necessary to better understand the process of spawning of silky shark.

Progesterone initiates tendril formation in the oviducal gland during egg encapsulation in cloudy catshark (Scyliorhinus torazame)

The diverse reproductive strategies of elasmobranchs (sharks, rays, and skates) have attracted research attention, but the endocrine control of reproduction is still incompletely known in elasmobranchs. By long-term monitoring of the egg-laying cycle in cloudy catsharks (Scyliorhinus torazame), we recently demonstrated a transient increase in plasma progesterone (P4) levels just prior to the appearance of the capsulated eggs in the oviducts. In the present study, we examined the in vivo effects of P4 administration in mature female cloudy catsharks. Although no capsulated eggs were observed following the implantation of P4-containing silicone tubing, we did find dark swollen oviducts in the abdominal cavity, in which clumps of long and coiled tendrils were observed. The tendril is an extension of the egg capsule, and the formation of the egg capsule begins with the tendril before main capsule formation. During the period of P4 implantation, the tendrils elongated, and their diameters were significantly increased on day 2 of treatment. Tendril formation was also confirmed on the day of endogenous P4 surge. Tendrils were not formed in catsharks implanted with estradiol-17β or testosterone. Histological analysis of the oviducal gland revealed that P4 implantation induced the secretion of tendril materials from the secretory tubules in the baffle zone, while the tendril materials were stored in the cytoplasm of the secretory cells under low P4 condition. Morphometrically, the area of secreted luminal materials in the secretory tubules was highly correlated to the diameter of tendrils. Our results suggest that the P4 surge during the egg-laying cycle serves as a trigger for egg capsule formation in the oviducal gland of cloudy catshark, but the hormonal signals were incomplete as the main capsule was not formed. Further studies are required to identify the hormones required for ovulation and formation of the main egg capsule.

The morphological characteristics and modification of the oviducal glands adapted for long-term sperm storage and fertilization in Amphioctopus fangsiao

Sperm storage is an important reproductive strategy in Amphioctopus fangsiao. Sperm can be stored in the oviducal glands up to eight months before fertilization. However, studies on the underlying storage mechanisms remain limited. In this study, the morphological structures of the oviductal glands and the changes adapted for sperm storage and fertilization were investigated by Hematoxylin eosin (HE) staining, transmission electron microscopy (TEM), and Alcian blue periodic acid Schiff (AB-PAS) staining. Results revealed that the nucleo-cytoplasmic ratio of the peripheral gland cells decreased and the eosinophilic secretory granules (glycoproteins) appeared in the cytoplasm and lumen during sperm storage. The cytoplasm of the central gland appeared vacuolated and AB pH 2.5 (+) secretions (acid mucins) were dispersed in the cells. These secretions may pass through the central cavity into the oviducts and be involved in zygote packaging. The spermathecae are composed of columnar epithelial ciliated cells with secretory functions. PAS (+) glycoproteins were found in the lumen, providing a microenvironment conducive to sperm survival. Cilia in the oviducts, central cavity, and spermathecae may help with sperm delivery, storage, and release, and egg transport. This study enhances our understanding of the biological reproduction process in A. fangsiao.

Diversity of the egg tertiary membranes in some elasmobranch species and comments on the actual yolk-sac viviparous reproductive mode

After fertilization, elasmobranch eggs (mostly megalecithal) are encapsulated in a tertiary membrane of different complexity, in the oviducal gland. The gross morphological characteristics of this membrane in elasmobranchs are highly variable, attaining it most sophisticates’ forms within the oviparous species. The purpose of this study was to contribute to the knowledge of the elasmobranch tertiary membranes, in both viviparous and oviparous species, and to discuss the relation with their role in protecting the embryos their development. In addition, the limitations of yolk-sac viviparity as a single reproductive mode category are commented, suggesting a new arrangement of taxa within that reproductive mode and new terminology. Data on tertiary membranes in elasmobranchs come from a large number of sources ranging from 1977 to date. Specimens were captured on board of commercial and scientific research cruises, from the following some major geographic regions: South Western Atlantic, South Western Pacific, and different areas of the Mediterranean Sea. In all, our records of tertiary membranes belong to ten species of sharks of five orders; Hexanchiformes, Squatiniformes, Heterodontiformes, Lamniformes, Carcharhiniformes, and eight species of rays and skates, of four orders: Rajiformes, Rhinopristiformes, Torpediniformes and Myliobatiformes. The reproductive modes reported for all this species were both lecithotrophic (yolk-sac viviparity, short single oviparity) and matrotrophic (ovotrophy, placentotrophy, limited and lipidic histotrophy). Six morphological and structural major patterns were detected within the yolk-sac viviparous species (type I to VI); a thin, diaphanous, shapeless membrane; candle capsules; oviparous-like tough egg capsule, and cases where no tertiary membrane was present.

Maturity and reproduction in the Arabian carpet shark, Chiloscyllium arabicum from the Saudi Arabian waters of the Arabian Gulf

ABSTRACT The Arabian carpet shark, Chiloscyllium arabicum is endemic to the Arabian Gulf and the northern Arabian Sea. The aim of this work is to study the reproduction and maturity of this species. A total of 87 males and 139 females, including 19 egg-bearing individuals collected from bottom set longline fisheries in the Saudi Arabian waters of the Arabian Gulf between October 2017 and February 2019, were examined. The size at 50% maturity was estimated as 62.3 and 62.5 cm total length (TL) for males and females, respectively. Changes in the gonadosomatic index (GSI) of males indicated the mating to happen between December and February. The maximum follicle diameter, oviducal gland width and GSI in mature females, suggested the ovulation to extend from September to May with the peak during March–May. Females carried 2–4 egg cases in the uteri, and the egg-laying period was between February and May. The segregation of sexes was observed in the larger (70–80 cm TL) size ranges.

Oviducal gland transcriptomics of Octopus maya through physiological stages and the negative effects of temperature on fertilization.

BackgroundElevated temperatures reduce fertilization and egg-laying rates in the octopus species. However, the molecular mechanisms that control the onset of fertilization and egg-laying in the octopus’ oviducal gland are still unclear; and the effect of temperature on the expression of key reproductive genes is unknown. This study aims to better understand the molecular bases of octopus fertilization and egg-laying, and how they are affected by elevated temperatures.MethodRNA-seq of oviducal glands was performed for samples before, during, and after fertilization and their transcriptomic profiles were compared. Also, at the fertilization stage, the optimal and thermal-stress conditions were contrasted. Expression levels of key reproductive genes were validated via RT-qPCR.ResultsIn mated females before egg-laying, genes required for the synthesis of spermine, spermidine, which may prevent premature fertilization, and the myomodulin neuropeptide were upregulated. Among the genes with higher expression at the fertilization stage, we found those encoding the receptors of serotonin, dopamine, and progesterone; genes involved in the assembly and motility of the sperm flagellum; genes that participate in the interaction between male and female gametes; and genes associated with the synthesis of eggshell mucoproteins. At temperatures above the optimal range for reproduction, mated females reduced the fertilization rate. This response coincided with the upregulation of myomodulin and APGW-amide neuropeptides. Also, genes associated with fertilization like LGALS3, VWC2, and Pcsk1 were downregulated at elevated temperatures. Similarly, in senescent females, genes involved in fertilization were downregulated but those involved in the metabolism of steroid hormones like SRD5A1 were highly expressed.

Differential gene expression analysis related to sperm storage in spermathecas of Amphioctopus fangsiao

Sperm storage in the female body is an important strategy in animal reproductive behavior. Amphioctopus fangsiao is an economically important cephalopod that has a sperm storage period of up to seven months. There are few studies concerning the mechanism of sperm storage in A. fangsiao. In this study, we performed transcriptome gene expression profiling of the oviductal glands at different phases (presence and absence of sperm storage). In total, 7943 differentially expressed genes (DEGs) comprising 4737 upregulated and 3206 downregulated genes were identified. GO and KEGG enrichment analyses were used to search for sperm storage-related genes. A protein interaction network was constructed to examine the interactions between genes. Nineteen genes associated with immunity, apoptosis, and autophagy were obtained and verified by qRT-PCR. This is the first comprehensive analysis of sperm storage-related genes in A. fangsiao. The results provide basic insights into the complex sperm storage mechanism of A. fangsiao.

Expressions and Distributions of Leucine-enkephalin, Delta, Mu, and Kappa Opioid Receptors in Four Systems of the Octopus, Octopus ocellatus by Comparative Immunohistochemical Method and ELISA

We have investigated the expressions and distributions of leucine-enkephalin (Leu-enk), delta (δ), mu (μ), and kappa (κ) opioid receptors immunoreactivities in the respiratory, circulatory, excretory and reproductive systems of the Octopus, Octopus ocellatus, by comparative immunohistochemical method and enzyme-linked immunosorbent assay (ELISA). The results showed that δ opioid receptor and Leu-enk immunoreactivities were both detected in the branchia, ventricle, branchial heart, ovary and oviducal gland, while δ opioid receptor was additionally detected in the branchial gland and kidneys in less extend. The majority of the examined tissues presented weak immunoreactivities of δ opioid receptor and Leu-enk, with the notable exception of the white body and spermary tissues that were found negative. No labellings of μ and κ opioid receptors were observed in the respiratory, circulatory, excretory and reproductive systems of O. ocellatus. The combined results of δ opioid receptor and Leu-enk immunoreactivities indicated that they may be involved in the regulations of respiration, circulation, reproduction and endocrine together with other hormones or neurotransmitters in the O. ocellatus’ body. The different densities of δ opioid receptor and Leu-enk in the respiratory, circulatory, excretory and reproductive systems of O. ocellatus may be related to the different functions.

The Establishment of an Optimal Protocol for Contrast-Enhanced Micro-Computed Tomography in the Cloudy Catshark Scyliorhinus torazame.

The purpose of this study was to determine the optimal imaging protocol for contrast-enhanced computed tomography (CECT) using micro-CT (μ-CT) for the posterior cardinal vein (PCV), dorsal aorta (DA), hepatic portal vein (HPV), kidney, liver, cephalic arteries (CAs), and gills of Cloudy Catsharks Scyliorhinus torazame. Additionally, we examined the availability of CECT screening for the coelomic organs. Different doses of iopamidol (100, 300, 500, and 700 mg iodine [mgI]/kg) were administered intravenously for 20 s in six sharks. The CT scans from the pectoral girdle to the pelvic girdle were performed at 0-600 s after administration. Contrast-enhanced CT imaging of the CAs, gills, and coelomic organs was examined. Assessment of the signal enhancement value revealed that the PCV was easily visualized with all contrast doses at 25 s. The CAs, gills, and DA were visible at a slightly higher dose (CAs and gills: 200 mgI/kg at 40 s; DA: 300 mgI/kg at 50 s). The HPV was obvious at a dose of at least 500 mgI/kg after a 150-s delay. The parenchyma of the kidney had a contrast effect at 300 mgI/kg, 150 s after the contrast effect of the renal portal system disappeared. The liver, which stores a lot of lipids, had poor overall contrast enhancement that was optimized at the highest dose of 700 mgI/kg. Contrast-enhanced CT screening at 700 mgI/kg and 150 s is likely to obtain the optimal imaging of the reproductive organs, such as the ovary, oviducal gland, uterus, and testis. The present findings can be applied not only to clinical practice but also to academic research and education on elasmobranchs in aquariums.

A Taxonomic Survey of Female Oviducal Glands in Chondrichthyes: A Comparative Overview of Microanatomy in the Two Reproductive Modes.

Simple SummaryThe oviducal gland (OG) is a specialized region of the reproductive female system in cartilaginous fish located in the anterior oviduct. Its biological importance is closely related to the reproductive modalities of these species, and its basic function is the production of the egg jellies, the tertiary envelope formation (egg case in oviparous and candle case in viviparous) and sperm storage. Since knowledge on the overall process of Chondrichthyes reproduction is still scarce, in this study we conducted morphological and morphometrical analysis on the OGs belonging to several cartilaginous fish displaying two different reproductive modalities (oviparity and viviparity). Moreover, we paid particular attention to the fate of spermatozoa in the female reproductive tract, which would be useful to better understand the ecology and population dynamics of these species.Oviducal glands (OGs) are distinct expanded regions of the anterior portion of the oviduct, commonly found in chondrichthyans, which play a key role in the production of the egg in-vestments and in the female sperm storage (FSS). The FSS phenomenon has implications for understanding the reproductive ecology and management of exploited populations, but little information is available on its taxonomic extent. For the first time, mature OGs from three lecithotrophic oviparous and four yolk-sac viviparous species, all considered at risk from the fishing impacts in the central western Mediterranean Sea, were examined using light microscopy. The OG microanatomy, whose morphology is generally conserved in all species, shows differences within the two reproductive modalities. Oviparous species show a more developed baffle zone in respect to viviparous ones because of the production of different egg envelopes produced. Among oviparous species, Raja polystigma and Chimaera monstrosa show presence of sperm, but not sperm storage as observed, instead, in Galeus melastomus and in all the viviparous sharks, which preserve sperm inside of specialized structures in the terminal zone.

Reproductive Anatomy of Chondrichthyans: Notes on Specimen Handling and Sperm Extraction. II. Sharks and Chimaeras

Simple SummarySperm extraction and artificial insemination may serve ex situ conservation initiatives for threatened sharks and related species. A comparison of the reproductive anatomy of eight chondrichthyans is presented in this study, emphasizing the important differences when performing these reproductive techniques. Additionally, we show how to obtain sperm samples from both living and dead specimens using cannulation, abdominal massage, or oviducal gland extraction. These tools can improve the success of breeding programs developed in aquaria and research facilities.The chondrichthyan fishes, which comprise sharks, rays, and chimaeras, are one of the most threatened groups of vertebrates on the planet. Given this situation, an additional strategy for the protection of these species could be the ex situ conservation projects developed in public aquaria and research centers. Nevertheless, to increase sustainability and to develop properly in situ reintroduction strategies, captive breeding techniques, such as sperm extraction and artificial insemination, should be developed. These techniques are commonly used in other threatened species and could be also used in chondrichthyans. However, the different reproductive morphologies found in this group can complicate both processes. Therefore, a comparison of the reproductive anatomy of eight distinct chondrichthyans, with an emphasis on those important differences when performing sperm extraction or artificial insemination, is carried out herein. Sharks and chimaeras belonging to the Scyliorhinidae, Carcharhinidae, Centrophoridae, Etmopteridae, Hexanchidae, and Chimaeridae families were obtained from commercial fisheries, public aquaria, and stranding events. In addition, the process of obtaining viable sperm samples through cannulation, abdominal massage, and oviducal gland extraction is described in detail for both living and dead animals.

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

Simple SummaryMany 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.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.

Female sperm storage in the bonnethead Sphyrna tiburo oviducal gland: Immunolocalization of steroid hormone receptors in sperm storage tubules

Female sperm storage (FSS) has been demonstrated to occur in representatives from all major vertebrate groups and has been hypothesized to have several possible adaptive benefits that may maximize reproductive success of its practitioners. However, while the range of taxa that exhibit FSS and its possible evolutionary benefits have received significant attention in past years, the physiological mechanisms by which FSS occurs in vertebrates have only recently been explored. In this study, we examined the potential role of gonadal steroid hormones in regulating FSS in the bonnethead Sphyrna tiburo, a small hammerhead species in which females have been shown to be capable of storing male spermatozoa for up to 6 – 7 months following copulation. Like past studies on this species, we observed associations between plasma concentrations of the gonadal steroids 17β-estradiol, testosterone, and progesterone with FSS in female bonnetheads, suggesting roles for these hormones in regulating this process. Using immunohistochemistry, we also observed presence of androgen receptor, estrogen receptor alpha (ERα), and progesterone receptor in epithelial cells of sperm storage tubules in the bonnethead oviducal gland, as well as occurrence of ERα in stored spermatozoa, specifically during the sperm storage period. These results suggest that E2, T, and P4 may regulate certain aspects of FSS in bonnethead indirectly through actions on the female reproductive tract, whereas E2 may also have direct effects on sperm function. This is the first study on the regulation of FSS in sharks and has formed a basis for future work geared towards improving our understanding of this process in chondrichthyans.

Reproductive biology of the swell shark Cephaloscyllium ventriosum (Carcharhiniformes: Scyliorhinidae).

The Cephaloscyllium ventriosum shark is present in the artisanal fisheries of elasmobranchs on the western coast of Baja California Sur, Mexico. The main characteristics of the sexual maturation of this species based on individuals captured from off north-west Mexico in 2013-2016 are described. The size at maturity of this species was determined for the first time (total length 82 cm for females and 76 cm for males). Most females had one egg case per one uterus, and two per one uterus was an isolated event of low incidence. From the histological analysis of females, it was possible to show sperm storage in the oviducal gland. Fully developed sperm in immature organisms were identified in the testes. The main indicator of the maturity stage of males and their mating activity is the clasper. The present study provides evidence for a reliable estimation of the sexual maturity of these organisms, demonstrating the need for the combination of macroscopic and microscopic methods.

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

BackgroundFundamental 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.ResultsThe 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.ConclusionsThe genital ducts of the females of F. signifer show differential microscopic and histochemical characteristics, indicating their different reproductive statuses.

Reproductive cycles of the southern banded guitarfish Zapteryx xyster and the Velez ray Raja velezi caught as bycatch in a bottom-trawl fishery

The southern banded guitarfish, Zapteryx xyster, and the Velez ray, Raja velezi, are two endemic elasmobranchs in the eastern Tropical Pacific that are commonly caught by the bottom-trawl fishery. Reproductive cycles of these batoids were inferred from the hepatosomatic and gonadosomatic indexes (males and females) and the oviductal gland width and the yolk follicle diameter (females) of mature specimens collected along the Pacific of Costa Rica between 2010 and 2011. Z. xyster females have a partially defined annual cycle with one reproductive peak in June and July, with most neonates and gravid females occurring during December and January (beginning of the dry season). The gestation period of Z. xyster can range between four and six months; males are probably capable of mating continuously throughout the year. Females and males of R. velezi have a continuous reproductive cycle with no clear peaks. Management and conservation measures of these batoids should consider their reproductive ecology, which may be linked to the degree of vulnerability to fishing. Based on our findings, we recommend reducing fishing pressure when mating (June-July) and pupping (December-January) of Z. xyster occur. In contrast, a reduction of fishing pressure on previously identified nursery grounds of R. velezi in the southern Pacific of Costa Rica may benefit their population.

Assessment of sperm storage across different reproductive modes in the elasmobranch fishes

The oviducal gland is a specialised region of the elasmobranch oviduct that is thought to be a site of sperm storage, among other functions. The phenomenon of female sperm storage in elasmobranchs has implications for the understanding of their reproductive ecology and the management of exploited populations, but relatively little information exists on its taxonomic extent. In the present study, oviducal glands from 29 different species, of varying reproductive modes, from the northern Indian and North East Atlantic oceans were examined using light microscopy for the presence of sperm. The organisation of the gland into four fundamental zones; club, papillary, baffle and terminal, was conserved across all species, with slight variations in relative zone volume due to reproductive mode. Spermatozoa observed within the oviducal gland were not limited to a particular reproductive mode or maturity stage. Although spermatozoa were most commonly encountered in the terminal zone tubules, in some species they were also encountered elsewhere in the gland. The storage of sperm may be a vital reproductive strategy for many species and furthering our taxonomic understanding of which species employ this strategy will help to better inform fisheries managers and protect exploited low reproductive species.

Reproductive parameters of the shovelnose guitarfish Pseudobatos productus (Ayres, 1856) in Northwest Mexico

The shovelnose guitarfish Pseudobatos productus is a major species in batoid catch on the north-western coasts of Mexico. Our goal was to describe the reproductive biology of this species, including morphometric and histological analysis of the gonads. Sampling was carried out on artisanal fishing camps near Bahía Tortugas, Baja California Sur, Mexico. A total of 147 organisms were collected, with a size of 58.9 to 162 cm of total length (TL). The size of first maturity (L50%) was 111.3 cm TL for females, and 102.2 cm TL for males. The sex ratio was 1.42 females per male, but 1:1 for embryos. Positive correlations were found between TL and the number of oocytes, the diameter of oocytes, the uterus height, the oviducal gland height, the oviducal gland width, and the clasper length. We describe four histological zones in the oviducal gland of females, with no sperm storage. Mature testicle lobes showed distinct spermatogenesis stages, ranging from spermatogonia to mature sperm cells.

Reproductive biology of the Rasptail skate Rostroraja velezi (Rajiformes: Rajidae).

The Rasptail skate Rostroraja velezi is commercially exploited in artisanal elasmobranch fisheries along the west coast of Baja California Sur, Mexico, but information on its life history is limited. This study aimed to investigate the reproductive biology of R. velezi. A total of 105 specimens were caught from April 2008 to May 2012, including the largest reported specimen with 121 cm total length, 96 cm disc width (DW ). Females attained larger sizes than males. Males and females presented functional gonads. There was an asymmetry in the testes of males, with the left testis being larger. Histological analysis of the reproductive biology of R. velezi was performed here for the first time. The presence of sperm storage in females and spermatogenic development beginning at the first stages of maturity in males was recorded. It was possible to identify the development of secretions in the club, baffle and terminal zone of the oviducal gland. DW at maturity, defined as the DW at which 50% of the population is mature, was estimated at 68-72 cm for females and 65.1 cm for males. Egg-bearing females caught in April and May presented one egg capsule per uterus. Furthermore, a description of the egg capsule of R. velezi is provided. Elucidating the reproductive cycle, the type of reproductive strategies, and the fecundity of R. velezi will allow us to understand the impact of fisheries on this species.