Sexual development dysgenesis in interspecific hybrids of Medaka fish.

Fish are amongst vertebrates the group with the highest diversity of known sex-determining genes. Particularly, the genus Oryzias is a suitable taxon to understand how different sex determination genetic networks evolved in closely related species. Two closely related species, O. latipes and O. curvinotus, do not only share the same XX/XY sex chromosome system, but also the same male sex-determining gene, dmrt1bY. We performed whole mRNA transcriptomes and morphology analyses of the gonads of hybrids resulting from reciprocal crosses between O. latipes and O. curvinotus. XY male hybrids, presenting meiotic arrest and no production of sperm were sterile, and about 30% of the XY hybrids underwent male-to-female sex reversal. Both XX and XY hybrid females exhibited reduced fertility and developed ovotestis while aging. Transcriptome data showed that male-related genes are upregulated in the XX and XY female hybrids. The transcriptomes of both types of female and of the male gonads are characterized by upregulation of meiosis and germ cell differentiation genes. Differences in the parental species in the downstream pathways of sexual development could explain sex reversal, sterility, and the development of intersex gonads in the hybrids. We hypothesize that male-to-female sex reversal may be connected to a different development time between species at which dmrt1bY expression starts. Our results provide molecular clues for the proximate mechanisms of hybrid incompatibility and Haldane's rule.

Clinician Advocacy and Intersex Health: A History of Intersex Health Care and the Role of the Clinician Advocate Past, Present, and Future.

Throughout the history of Western culture, sex has been reflected as a binary rule, with this binary system affecting self-expression, lifestyle choices, and health outcomes of everyone, but especially those with intersex traits. "Intersex" (or differences of sex development) is an umbrella term used to describe a wide range of natural variations in genitalia, gonads, and chromosome patterns that do not fit typical binary notions of male or female bodies. Currently, people who identify as intersex or as having intersex traits are not provided with the appropriate care needed for their wellbeing. Intersex health care has undergone a great deal of change in the last century, led by intersex leaders and advocates. Clinician advocates have also played a vital role. This article will focus on this history of intersex health care evolution, the role of clinician advocacy, and suggestions for how clinicians can become advocates for improving intersex health care. [Pediatr Ann. 2021;50(9):e359-e365.].

Rad21l1 cohesin subunit is dispensable for spermatogenesis but not oogenesis in zebrafish.

During meiosis I, ring-shaped cohesin complexes play important roles in aiding the proper segregation of homologous chromosomes. RAD21L is a meiosis-specific vertebrate cohesin that is required for spermatogenesis in mice but is dispensable for oogenesis in young animals. The role of this cohesin in other vertebrate models has not been explored. Here, we tested if the zebrafish homolog Rad21l1 is required for meiotic chromosome dynamics during spermatogenesis and oogenesis. We found that Rad21l1 localizes to unsynapsed chromosome axes. It is also found between the axes of the mature tripartite synaptonemal complex (SC) in both sexes. We knocked out rad21l1 and found that nearly all rad21l1-/- mutants develop as fertile males, suggesting that the mutation causes a defect in juvenile oogenesis, since insufficient oocyte production triggers female to male sex reversal in zebrafish. Sex reversal was partially suppressed by mutation of the checkpoint gene tp53, suggesting that the rad21l1 mutation activates Tp53-mediated apoptosis or arrest in females. This response, however, is not linked to a defect in repairing Spo11-induced double-strand breaks since deletion of spo11 does not suppress the sex reversal phenotype. Compared to tp53 single mutant controls, rad21l1-/- tp53-/- double mutant females produce poor quality eggs that often die or develop into malformed embryos. Overall, these results indicate that the absence of rad21l1-/- females is due to a checkpoint-mediated response and highlight a role for a meiotic-specific cohesin subunit in oogenesis but not spermatogenesis.

Involvement of glycolysis activation in flatfish sexual size dimorphism: Insights from transcriptomic analyses of Platichthys stellatus and Cynoglossus semilaevis.

The starry flounder (Platichthys stellatus), a flatfish cultured at the margins of the North Pacific, displays an obvious female-biased growth advantage, similar to many other fish species. To reveal the molecular mechanism underlying sexual size dimorphism, a comparative transcriptomic analysis of the somatotropic and reproductive axes was conducted. In total, 156, 67, 3434, and 378 differentially expressed genes (DEGs) between female and male samples were obtained in the brain, liver, gonad, and muscle tissues (q < 0.05). These DEGs were significantly enriched for various GO terms, including ion channel activity, protein binding, lipid transporter activity, and glycolytic process. The significantly enriched KEGG pathways included insulin secretion, axon guidance, and glycolysis/gluconeogenesis. In a detailed analysis of DEGs in these significantly enriched pathways, 35 genes showed higher expression levels in female muscle tissues than in male muscle tissues. A protein-protein interaction network further revealed specific interactions involving the glycolysis related-protein enolase (ENO), triosephosphate isomerase (TPI), Bisphosphoglycerate mutase (BPGM), fructose-bisphosphate aldolase (ALDO), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Interestingly, the role of glycolysis/gluconeogenesis was supported by an analysis of common DEGs between P. stellatus and Chinese tongue sole (Cynoglossus semilaevis). These results indicate that the activation of glycolysis in female muscle tissues contributes to flatfish sexual size dimorphism.

Photoperiod in aquaculture of the sea urchin Arbacia dufresnii (Echinodermata: Echinoidea): Effects on gamete production and maturity / Fotoperiodo en la acuicultura del erizo de mar Arbacia dufresnii (Echinodermata: Echinoidea): El efecto en la producción y madurez de gametas

Introduction: Photoperiod is, together with temperature and food availability, one of the main stimuli in the regulation of gametogenesis in a wide variety of species. Objective: To evaluate the effect of photoperiod on the production of mature gametes in cultured Arbacia dufresnii. Methods: An experiment was carried out with three varying light-dark regimes/treatments: constant light (24 h light), neutral photoperiod (12 h light, 12 h darkness), and constant darkness (24 h darkness). Twenty females were used in each treatment. All were induced to spawn and, ten randomly selected females from each treatment were induced to spawn again after 30 days. After 60 days, spawning was induced in the remaining females. The gametes were collected in filtered seawater, fixed in Davidson solution, quantified and measured per individual in triplicate in a Sedgewick-Rafter chamber. To determine maturation, fertilization success was evaluated 30 minutes after fertilization. Results: Our results showed that in the aquaculture system, after only two months, mature gametes were obtained, and in the neutral light regime there were 10 times more gametes than the number produced in wild sea urchins during the spawning period in question. We also found that with a greater exposure to light, a lower number of mature gametes was produced. Conclusions: This study suggests the viability of the production of mature gametes in a short period of time as regards Arbacia dufresnii.

Introducción: El fotoperiodo es, junto con la temperatura y la disponibilidad de alimentos, uno de los principales estímulos para el desarrollo de la gametogénesis en una amplia variedad de especies. Objetivo: Evaluar el efecto del fotoperiodo en la producción de gametas maduras de Arbacia dufresnii en un sistema de recirculación cerrado para determinar el mejor fotoperiodo para una acuicultura novedosa, enfocada en la producción de gametas con alta concentración de pigmentos para usos biotecnológicos. Métodos: Se realizó un experimento con tres regímenes/tratamientos diferentes de luz y oscuridad: luz constante (luz durante 24 h), fotoperiodo neutro (12 h de luz, 12 h de oscuridad) y oscuridad constante (oscuridad durante 24 h). Se utilizaron veinte hembras en cada tratamiento. Se indujo a todas las hembras a desovar al comienzo del experimento. Después de 30 días, diez hembras seleccionadas al azar de cada tratamiento fueron inducidas a desovar nuevamente. Al final del experimento, después de 60 días, se indujo el desove a las hembras restantes en cada tratamiento. Las gametas se recolectaron en agua de mar filtrada, se fijaron en solución de Davidson, se cuantificaron y midieron por triplicado en una cámara Sedgewick-Rafter. Para determinar la maduración, se evaluó el éxito de la fecundación después de 30 minutos de fertilización, calculando el porcentaje de huevos fertilizados. Resultados: Nuestros resultados muestran que, en el sistema acuícola, en solo dos meses se obtuvieron gametas maduras y casi 10 veces más la cantidad producida por los erizos de mar en su ambiente natural usando el fotoperiodo neutro (12 h luz:12 h oscuridad). También encontramos que la mayor exposición a la luz produce la menor cantidad de gametas maduras. Conclusión: Este estudio sugiere la viabilidad de la producción de gametos maduros en un corto período de tiempo en Arbacia dufresnii.

Structure of the gonoduct of the viviparous teleost Cnesterodon decemmaculatus (Jenyns, 1842) (Poeciliidae).

During embryogenesis, teleost females do not develop Müllerian ducts, which form the oviducts in all other vertebrates. Thus, when they reach sexual maturity they do not have oviducts. In viviparous teleosts, the lack of oviducts means that the development of the embryos occurs as an intraovarian gestation, unique among vertebrates. The ovary is an unpaired hollow organ whose cavity is continuous with the caudal portion, the gonoduct, characterized by the absence of germinal cells, which opens to the exterior at the gonopore. The gonoduct attains essential function as a barrier between the germinal region of the ovary and the exterior during all reproductive stages. This study describes the functional morphology of the gonoduct in the viviparous teleost Cnesterodon decemmaculatus during non-gestation (previtellogenesis and vitellogenesis) and gestation. The ovaries were processed using histological techniques and stained with hematoxylin-eosin, and periodic acid Schiff. The gonoduct has two regions: cephalic and caudal, and is formed by three histological layers, which are, from inside to the periphery: (a) tunica mucosa; (b) tunica muscularis; and (c) tunica serosa. In the cephalic region there are mucosal folds extending into the lumen and forming a structure similar to a cervix. The histology of the gonoduct indicates essential functions, that is, (a) the control of the luminal diameter in the limit to the germinal region of the ovary by the presence of a cervix; (b) during insemination the gonoduct receives the spermatozoa, may store and transport them to the germinal region; (c) the presence of melano-macrophage centers indicates support of immunological processes, especially during gestation when these centers increase in size; (d) production of exocrine secretions; and (e) it is the birth canal, internally lined by an ciliated epithelium and surrounded by smooth musclesboth tissues supposedly supporting the birth process.

Transcriptomic analysis of gene expression in normal goat ovary and intersex goat gonad.

Intersexuality is a congenital reproductive disorder that usually occurs in hornless goats, hindering breeding of goats with hornless traits and the development of the goat industry. In this study, we aimed to identify differentially expressed genes in intersex and normal goat gonads by comparing gene transcription profiles of intersex and normal goat gonads. As intersex goats are genetically based on females, we chose female goats as controls. The goats in the control group and the experimental group were both over one-year old. We evaluated the anatomical characteristics of the reproductive organs of five intersex goats using histopathological methods. The gonads were found to be ovarian and testicular types. RNA-Seq technology was used to identify differentially expressed genes in gonads and normal goat ovary tissues. Transcription analysis results were verified by qPCR. The results showed that 2,748 DEGs were upregulated and 3,327 DEGs were downregulated in intersex ovaries unlike in controls, whereas 2006 DEGs were upregulated and 2032 DEGs were downregulated in the interstitial testes. Many of these genes play important roles in mammalian sex determination and sex differentiation, such as SOX9, WT1, GATA4, DMRT1, DHH, AMH, CYP19A1 and FST. We found that many DEGs are involved in biological developmental regulation by GO and KEGG enrichment analyses, and that most genes associated with the steroid synthesis pathway were downregulated. The DEGs identified in this study may be involved in the regulation of intersex goat sex determination and differentiation, and may increase our understanding of the molecular mechanisms of mammalian sex differentiation.

Identification and characteristics of insulin-like growth factor system in the brain, liver, and gonad during development of a seasonal breeding teleost, Pampus argenteus.

Reproductive activity is closely related to the development and function of the brain and liver in teleosts, particularly in seasonal breeding teleosts. This study measured the involvement of the insulin-like growth factor (IGF) system in controlling the reproduction of the silver pomfret Pampus argenteus, a seasonal breeding tropical to temperate commercial fish. We cloned and characterized the cDNAs of igfs (igf2 and igf3) and igfrs (igf1ra, igf1rb, and igf2r) and examined their transcript levels in relation to seasonal reproduction. Phylogenetic analyses revealed that two types of IGFs (IGF-1 and IGF-2) and three types of IGFRs (IGF1RA, IGF1RB, and IGF2R) of the silver pomfret were clustered with those of teleosts; however, IGF-3 was a transmembrane protein different with the IGF-3 of other teleosts. The expression of IGF-3 was gonad-specific in the silver pomfret. The transcript levels of igf1 in the female brain were the highest, and the levels of igfrs in both sexes' brains increased during gametogenesis. Meanwhile, igfs and igfrs maintained high transcript levels in both sexes' liver and gonad during vitellogenesis and spermatogonia proliferation. We concluded that the development and activities of brain, liver, and gonad were related to the IGF system (IGFs and IGFRs). And the IGFs were mainly expressed in the liver. Nevertheless, gonadal development, especially vitellogenesis and spermatogonia proliferation, were related with IGFs in this species.

Gonadal maturation in Pseudoplatystoma metaense x Leiarius marmoratus hybrids, (Siluriformes: Pimelodidae) / Maduración gonadal en híbridos de Pseudoplatystoma metaense x Leiarius marmoratus (Siluriformes: Pimelodidae)

SUMMARY: Establishing guidelines for responsible management in fish production systems requires knowledge of the basic biology of the fish to be raised. The objective of this work was to determine the reproductive capacity of hybrids produced from the crossing of females of Pseudoplatystoma metaense with males of Leiarius marmoratus. Males presented a digitiform, unrestricted spermatogonial testicle containing caudal digits producing glycoproteins that do not form a seminal vesicle. It was possible to find free sperm in the lumen of the tubules and in the ducts. The ovary of the females was found to be saccular and synchronous with at least three groups of oocytes. In the first year of life, only oogonia up to previtellogenic oocytes (cortical alveolus 284.9 ± 35.7 mm in diameter) were found. After the second year vitellogenic oocytes 730 ± 3.78 mm in diameter were observed. The events of gonadal development of the hybrids indicate that they are gonochoric, synchronic animals. The maturation peaks in the high-water season, overlapping with the parental species. Therefore, the escape of hybrids from fish cultures to the rivers may increase the risk of crosses, gene introgression, or diminution of the reproductive capacity of the pure species.

RESUMEN: El establecimiento de pautas para la gestión responsable en los sistemas de producción de peces requiere el conocimiento de la biología básica de los peces a criar. El objetivo de este trabajo fue determinar la capacidad reproductiva de los híbridos producidos por el cruce de hembras de Pseudoplatystoma metaense con machos de Leiarius marmoratus. Los machos presentaron un testículo espermatogonial digital no restringido que contiene dígitos caudales que producen glucoproteínas que no forman una vesícula seminal. Fue posible encontrar esperma libre en la luz de los túbulos y en los conductos. Se encontró que el ovario de las hembras era sacular y sincrónico con al menos tres grupos de ovocitos. En el primer año de vida, solo se encontraron oogonia hasta ovocitos previtelogénicos (alvéolo cortical de 284,9 ± 35,7 mm de diámetro). Después del segundo año, se observaron ovocitos vitelogénicos de 730 ± 3,78 mm de diámetro. Los eventos de desarrollo gonadal de los híbridos indican que son animales sincrónicos gonocóricos. La maduración alcanza su punto máximo en la temporada de aguas altas, superponiéndose con las especies parentales. Por lo tanto, el escape de híbridos de cultivos de peces a los ríos puede aumentar el riesgo de cruces, introgresión genética o disminución de la capacidad reproductiva de las especies puras.

Morphological, ecological and physiological characteristics of downstream-migrating and non-migrating Pacific bicolor eels Anguilla bicolor pacifica.

This is the first study describing the morphological, ecological and physiological characteristics of two downstream-migrating and two non-migrating female Pacific bicolor eels, Anguilla bicolor pacifica. The total length and age of the downstream-migrating eels were 1005 mm and 10 years and 1110 mm and 11 years old, respectively, and those of the non-migrating eels were 892 mm and 8 years and 805 mm and 9 years, respectively. Silvering-related characteristics (silvering index, eye index, pectoral-fin index, gut-somatic index and swimbladder-somatic index) and reproductive physiological characteristics (gonado-somatic index, follicle diameter, oocyte stage, transcription of gonadotropins and concentration of sex steroids) of the migrating eels were more advanced than those of the non-migrating eels.

Re-evaluation of reproductive cycle and fecundity of finetooth sharks Carcharhinus isodon (Valenciennes 1839) from the Northwest Atlantic Ocean, with new observations on ovarian cycle and reproductive endocrinology of biennially reproducing sharks.

To provide updated information on life history for improved fishery management, the reproductive cycle of the finetooth shark Carcharhinus isodon from Northwest Atlantic (NWA) populations was investigated by examining temporal changes in morphology and histology of reproductive organs. Changes in plasma concentrations of gonadal sex hormones in relation to reproductive stage were also examined. Increases in testis width, epididymis head width, plasma testosterone concentrations and occurrence of mature spermatozoa were observed in male sharks between December and April, suggesting a seasonal pattern in reproduction that culminates with copulatory activity in May. Increases in maximum follicular diameter, oviducal gland width, plasma 17ß-estradiol concentrations and occurrence of vitellogenic follicles were observed in non-pregnant female sharks during the same time period along with the occurrence of newly pregnant females in May, demonstrating strong synchronicity between male and female reproductive cycles. Pregnant females bearing full-term embryos were also observed in May, indicating that parturition occurs between mid-May and early June and gestation requires 12 months. Only transient temporal changes in follicle size and oviducal gland width were observed in pregnant females, indicating that reproductive periodicity is biennial; nonetheless, a single female exhibiting signs of concurrent vitellogenesis and pregnancy was observed. Mean brood size ± S.D. was 3.9 ± 0.9 offspring/female. Fecundity was not significantly correlated with female size, in part due to an unexpectedly high rate of early embryo mortality, which occurred in 11% of pregnant females, and was more common in larger individuals. Changes in ovarian activity during mid-pregnancy were observed, suggesting possible roles for the ovary in regulating some aspects of early to mid-gestation. This study confirms that earlier characterizations of the reproductive cycle and fecundity in NWA finetooth sharks remain valid for use in fishery management. This study also highlights unusual features of finetooth shark pregnancy (e.g., early embryo death, mid-pregnancy changes in ovarian function) that may have broader relevance to understanding elasmobranch reproduction.

Traditional approaches to estimate length at first maturity (L50 ) retrieve better results than alternative ones in a Neotropical heptapterid.

Length at first maturity (L50 ) is an important tool for the management and conservation of fish populations. Traditional approaches based on macroscopic and microscopic maturity staging exhibit high accuracy and precision, while alternative approaches (e.g., Ig -based staging, stanza changing point) are less resource-demanding. Herein, we compare four approaches to estimate L50 in a population of the heptapterid Rhamdioglanis transfasciatus from Atlantic Forest streams. Fish were sampled monthly during a year by using electrofishing. We measured the length (cm), mass (g), and gonad mass (g) of each specimen, then classified their maturity status macroscopically and microscopically. Alternative approaches were strongly discordant from traditional ones. Logistic curves considering mature individuals as those displaying at least 1% of the maximum Ig in the sample greatly underestimated L50 for females and overestimated L50 for males. The stanza changing point derived from the polyphasic growth model underestimated L50 in both cases. Despite the increasing development of less onerous approaches, it seems that they are not suitable for all fish populations and the requirements to use such approaches demand further investigation.

Gonadal analysis in the F1 progeny of a gynogenetic Siberian sturgeon Acipenser baerii female.

This is the first report of reproduction of a gynogenetic female Siberian sturgeon (Acipenser baerii) and subsequent production of viable offspring with differentiated gonads. Gonads were sampled twice from 30 randomly selected individuals. Gonadal fragments were examined histologically to identify the sex ratio and the sexual maturation stage. The first examined group consisted of 20 % females, 45 % males and 35 % sexually undifferentiated individuals, whereas the second group was composed of 30 % females and 70 % males. The average gonadosomatic index was determined to be 2.72 % and 2.80 % in the first and second groups, respectively. Molecular analysis based on five microsatellite DNA loci was conducted for all the fish for which there were evaluations. The aim of the study was to determine whether the gynogenetic Siberian sturgeon female that produced the offspring that were evaluated was a "superfemale" (WW) or a normal female (ZW). A "superfemale", therefore, is a female of the WW genotype that will produce only females when mated to a male with a ZZ genotype. The presence of female and male offspring clearly indicates that the Siberian sturgeon female that produced the offspring was not a "superfemale".

Comparing the effect of triadimefon and its metabolite on male and female Xenopus laevis: Obstructed growth and gonad morphology.

Amphibians are the most endangered class of vertebrates. In this study, Xenopus laevis frogs were exposed to 0, 1 and 10 mg/L of triadimefon or triadimenol. After 14 or 28 days of exposure, high levels of triadimefon or triadimenol obstructed the growth of frogs. However, low levels of triadimefon induced the growth of females after the longer period of exposure. We also found that the antioxidant enzyme activity and LDH levels in males were higher than those in females after 28-days exposure. In histopathology tests, triadimenol exerted more effect on the ovary while triadimefon exerted more effect on the testes. Additionally, the levels of Estradiol in all 14-day treatments, except 1 mg/L triadimenol, were significantly decreased, however, there was no difference in testosterone levels. Furthermore, triadimefon and triadimenol disrupted the expression of genes controlling hormone homeostasis and reproduction, and this effect depended on the exposure time and the gender of the organism. Our experiments explored the effect of triadimefon and its metabolite on the gonads of frogs and highlighted the role that pesticides are likely to play in the global decline of amphibians.

Natural sex change in mature protogynous orange-spotted grouper (Epinephelus coioides): gonadal restructuring, sex hormone shifts and gene profiles.

Sexual patterns of teleosts are extremely diverse and include both gonochorism and hermaphroditism. As a protogynous hermaphroditic fish, all orange-spotted groupers (Epinephelus coioides) develop directly into females, and some individuals change sex to become functional males later in life. This study investigated gonadal restructuring, shifts in sex hormone levels and gene profiles of cultured mature female groupers during the first (main) breeding season of 2019 in Huizhou, China (22° 42' 02.6″ N, 114° 32' 10.1″ E). Analysis of gonadal restructuring revealed that females with pre-vitellogenic ovaries underwent vitellogenesis, spawning and regression and then returned to the pre-vitellogenic stage in the late breeding season, at which point some changed sex to become males via the intersex gonad stage. A significant decrease in the level of serum 17ß-estradiol (E2) was observed during ovary regression but not during sex change, whereas serum 11-ketotestosterone (11-KT) concentrations increased significantly during sex change with the highest concentration in newly developed males. Consistent with serum hormone changes, a significant decrease in cyp19a1a expression was observed during ovary regression but not during sex change, whereas the expression of cyp11c1 and hsd11b2 increased significantly during sex change. Interestingly, hsd11b2 but not cyp11c1 was significantly upregulated from the pre-vitellogenic ovary stage to the early intersex gonad stage. These results suggest that a decrease in serum E2 concentration and downregulation of cyp19a1a expression are not necessary to trigger the female-to-male transformation, whereas increased 11-KT concentration and upregulation of hsd11b2 expression may be key events for the initiation of sex change in the orange-spotted grouper.

Captivity alters neuroendocrine regulators of stress and reproduction in the hypothalamus in response to acute stress.

Wild animals are brought into captivity for many reasons. However, unlike laboratory-bred animals, wild caught animals often respond to the dramatic shift in their environment with physiological changes in the stress and reproductive pathways. Using wild-caught male and female house sparrows (Passer domesticus) we examined how time in captivity affects the expression of reproductive and stress-associated genes in the brain, specifically, the hypothalamus. We quantified relative mRNA expression of a neurohormone involved in the stress response (corticotropin releasing hormone [CRH]), a hypothalamic inhibitor of reproduction (gonadotropin inhibitory hormone [GnIH]), and the glucocorticoid receptor (GR), which is important in terminating the stress response. To understand potential shifts at the cellular level, we also examined the presence of hypothalamic GnIH (GnIH-ir) using immunohistochemistry. We hypothesized that expression of these genes and the abundance of cells immunoreactive for GnIH would change in response to time in captivity as compared to free-living individuals. We found that GR mRNA expression and GnIH-ir cell abundance increased after 24 and 45 days in captivity, as compared to wild-caught birds. At 66 days in captivity, GR expression and GnIH cell abundance did not differ from wild-caught birds, suggesting birds had acclimated to captivity. Evaluation of CRH and GnIH mRNA expression yielded similar trends, though they were not statistically significant. In addition, although neuroendocrine factors appeared to acclimate to captivity, a previous study indicated that corticosterone release and immune responses of these same birds did not acclimate to captivity, suggesting that neuroendocrine endpoints may adapt more rapidly to captivity than downstream physiological measures. These data expand our understanding of the physiological shifts occurring when wild animals are brought into captivity.

Morphological characterization of pirarucu Arapaima gigas (Schinz, 1822) gonadal differentiation.

Arapaima gigas is a giant air-breathing and bony tongue fish from the Amazon basin and a promising species for aquaculture. A. gigas farming industry is still not established because of the lack of information on its reproductive physiology. Reproduction in captivity cannot be manipulated or stimulated, and the identification of males and females in a broodstock is not easy. We aimed to reveal the morphological sex differentiation of pirarucu as studies involving gonad development are essential to understanding the reproductive physiology of any species. We performed histological analysis on the whole body and extracted the gonads of 150 juveniles. The first sign of ovary differentiation is the sex-specific rearrangement of the germ cells. In 9 cm total length females, the germ cells group into nests and are restricted to the lateral face of the gonad, in close contact with the abdomen wall. With further development, this region invaginates and that later develops into ovigerous lamellae. Meiosis starts soon after ovary differentiation. In males, the germ cells are scattered along the elongated differentiating testis at first, and later become more restricted to the central region where the spermatogonial cysts start to develop. Somatic and germ cells are jointly involved in the cellular reorganization during gonadal differentiation, specifically when the germ cells begin to establish new associations during the development of both the germinal epithelium and stroma. RESEARCH HIGHLIGHTS: In Arapaima gigas, the ovary differentiation occurs in 9 cm TL females and it is marked by the rearrangement of germ and somatic cells; and the germ cells entering meiosis with no formation of ovarian cavity; testis differentiation occurs later and meiosis does not start in males smaller than 80 cm TL.

In vivo assessment of gonad status, secondary sex characteristics and spawning in transparent Casper zebrafish.

Important aspects of vertebrate reproduction, such as gametogenesis, involve changes in organs found deep internally and thus not easily studied directly in most living vertebrates due to obscuring pigment and overlying tissues. Transparent lines of zebrafish, especially the Casper double mutant, allow direct observation and analysis of reproductive events in the gonads in vivo. The natural production of fertilized eggs in zebrafish is a complex process involving oogenesis, spermatogenesis, mating behavior, endocrine and neurological processes with inputs from the environment including light, temperature and nutrition. While these factors play important roles, the hypothalamic-pituitary-gonadal axis (HPGA) is central in the regulation of embryo output. Endocrine disrupting compounds (EDCs) include a variety of pollutants often present in the environment. EDCs may have direct effects on the HPGA or indirect effects through toxic action on supporting organs such as the liver or kidney. Estrogenic compounds such as diethylstilbestrol (DES) have been reported to affect reproduction in a variety of species including man. In this study, the effects of DES on reproduction were determined in a novel way by using transparent Casper zebrafish that allow direct visualization of gonad status over time. Changes in gonad status with DES treatment were correlated with effects on secondary sex characteristics (i.e., genital vent size and breeding tubercles) spawning and embryo production. The results suggest that the Casper zebrafish is a useful model for studying dynamics of reproductive events in vertebrate gonads in vivo and for determining effects of EDCs on zebrafish reproduction.

Transcriptome analysis to characterize the genes related to gonad growth and fatty acid metabolism in the sea urchin Strongylocentrotus intermedius.

BACKGROUND: Sea urchin gonads of both sexes, commonly termed "roe", are highly valued seafood delicacies, and Strongylocentrotus intermedius is considered one of the tastiest sea urchins. In order to produce high-quality gonads for consumption and clarify the mechanism of gonad growth and development of the sea urchin, more genetic information, especially at the transcriptome level, is needed. OBJECTIVE: A more thorough understanding of sea urchin gonad growth and development in both sexes could enable regulation of these processes at several stages with the aim of suppressing gametogenesis in order to produce high-quality gonads for consumption. METHODS: The adult sea urchins S. intermedius were cultured for 3 months, and were sampled for the gonadal transcriptome analysis which has been performed on the RNAs of three male and female adults of S. intermedius in each gonad development stage. RESULTS: Illumina sequencing raw sequence data was deposited in the NCBI Sequence Read Archive (SRA) database (PRJNA532998). It generated 560,196,356 raw reads and 548,956,944 clean reads were acquired, which were assembled into 107,850 transcripts with 44,124 genes. Comparative analysis showed the differentially expressed genes (DEGs) from 114 to 2566. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were used to determine the functional significance of these DEGs. We have selected 9 genes related to growth and 12 genes related to fatty acid biosynthesis and metabolism in sea urchin gonads. CONCLUSION: These data for sea urchins were intended to provide markers for gonad growth and development that can be accumulated for use in aquaculture applications.

Reproductive biology of the Neotropical catfish Iheringichthys labrosus (Siluriformes: Pimelodidae), with anatomical and morphometric analysis of gonadal tissues.

The reproduction of Iheringichthys labrosus (Lütken, 1874) from the Turvo River, Brazil, was studied using anatomical, biometric, histological, and ultrastructural techniques. Between April 2014 and March 2015, a total of 278 males and 512 females were captured bimonthly. The testes of Iheringichthys labrosus are fringed and possess a cranial spermatogenic region and an exclusively secretory caudal region. Histologically, the cranial region is composed of seminiferous tubules with spermatogenesis being completed in cysts. The spermatozoa are of the primitive type with a spherical head and have a rudimentary intermediate piece and a long tail with an axonemic arrangement of 9 + 2. The caudal region does not form an individualized gland, and cells in this testis area have characteristics of protein secretion. A variable density electron-dense secretion accumulates in the cisternae of the rough endoplasmic reticulum in the lumen of the seminiferous tubules and in the testicular ducts during maturation. The cortical alveoli are discontinuous, and the zona pellucida consists of three layers crossed by pore canals, and the follicular cells are squamous in the early stages of oogenesis and cuboidal in advanced stages. The gonadosomatic index was associated with the maturation of the gonads while the condition factor indicated that the fish feed less and utilize adipose reserves during the reproductive period. Males and females reproductively functional throughout the year with spawning being partial or multiple, similar to that reported in studies of the species in lentic environments.