Alterations in neurotransmitters, steroid hormones, vitellogenin, and antioxidant system induced by di-n-butyl phthalate and di-isopentyl phthalate on catfish Rhamdia quelen.

Phthalates, such as di-n-butyl phthalate (DBP) and di-isopentyl phthalate (DiPeP), are pollutants with a high potential for endocrine disruption. This study aimed to evaluate parameters of endocrine disruption in specimens of the Neotropical fish Rhamdia quelen exposed to DBP and DiPeP through their food. After 30 days of exposure, the fish were anesthetized and then euthanized, and blood, hypothalamus, liver, and gonads were collected. DBP caused statistically significant alterations in the serotoninergic system of males (5 and 25 ng/g) and females (5 ng/g) of R. quelen and it increased testosterone levels in females (25 ng/g). DiPeP significantly altered the dopaminergic system in females, reduced plasma estradiol levels (125 ng/g) and hepatic vitellogenin expression (25 ng/g), and changed the antioxidant system in gonads (125 ng/g). The results suggest that DBP and DiPeP may have different response patterns in females, with the former being androgenic and the latter being anti-estrogenic. These findings provide additional evidence regarding the molecular events involving DBP and DiPeP in the endocrine disruption potential in juvenile specimens of Rhamdia quelen.

Effects of acute hypothyroidism on plasma melatonin and Aanat and Asmt expression in the pineal gland and gonads of rats.

Introduction: The reproductive system is tightly regulated by environmental and physiological signals. Melatonin, known as the hormone of darkness, plays a crucial role in regulating both the circadian and reproductive systems in mammals. Hypothyroidism is a key endocrine disorder that harms the reproductive system. Despite many studies on melatonin's effects on the reproductive system, there is conflicting information regarding melatonin synthesis modulation in hypothyroidism. The objective of this study was to investigate the modulation of plasma melatonin levels and gene expression of Aanat and Asmt in the pineal gland and gonads of rats with hypothyroidism at different times of the day. Methods: Female and male Wistar rats were divided into control and hypothyroid groups. Hypothyroidism was induced using propylthiouracil (PTU) for 15 days, rats were euthanized six hours after lights on (ZT6), before lights off (ZT11.5), and six hours after lights off (ZT18). Free thyroxine (FT4) and melatonin were quantified in plasma, and gene expressions of melatonin synthesizing enzymes (Aanat and Asmt) were measured in pineal and sexual organs (testis and ovary). Also, morphological analysis was performed in sexual organs. Results: The results reveal some disparities between the sexes. Hypothyroidism reduced antral and primary follicles in the ovary, and reduced the weight of testis, epididymis, and prostate. In relation to gene expression, we observed a reduction in Aanat expression in the pineal gland during the light phase (ZT6), and in males, this reduction occurred during the dark phase (ZT18). Regarding Asmt expression, there was a decrease in females also during the dark phase (ZT18). In the gonads, there was an increase in expression in both sexes at ZT11.5. Additionally, it was interesting to observe the association between FT4 levels and Asmt expression in the gonads. Conclusions: This study showed that acute hypothyroidism can affect components of the melatonergic system in gonads, particularly gene expression of melatonin synthesis enzymes (Aanat and Asmt) contributing to changes in reproduction organs during disease progression. These findings enhance our understanding of melatonin synthesis in the reproductive system during hypothyroidism, showing distinct responses in male and female rats, and suggest that hypothyroidism affects the circadian rhythmicity of melatonin synthesis in a sex-dependent manner.

Reproductive biology of Donax striatus (Linnaeus, 1758) (Mollusca: Bivalvia) on Gado Bravo Beach, municipality of Tibau do Norte, state of Rio Grande do Norte, Brazil.

Aspects of the reproductive biology of Donax striatus were studied from individuals collected from Gado Bravo Beach in the municipality of Tibau do Norte, state of Rio Grande do Norte, Brazil. Donax striatus is a dioic species without external (on the shell) or internal (gonads) macroscopic dimorphism. Thus, a microscopic examination of the reproductive cells is necessary. For the characterization of the gonadal development stages and determination of the size at first sexual maturity (L50), 30 specimens were selected monthly between February 2021 and January 2022 and submitted to histological processing. The condition index (CI) of each individual was estimated and monthly variations were statistically assessed. The size at first maturity (L50) was estimated to be 14.2 mm in shell length. To foster conservation of the species, catches of individuals larger than 14.2 mm is recommended. The lowest condition indices were found in the dry season, with a greater occurrence of organisms in the elimination stage and exhibiting gonad tissue reorganization. Higher indices were found in the rainy season, with the presence of mature individuals. The continuous nature of gametogenesis in Donax stritatus reflects the influence of rainfall in the region. Males and females have peak gamete elimination with pauses during the year, but with the presence of maturing and eliminating individuals throughout the year. As shellfish gathering targeting Donax striatus is excessive on Gado Bravo Beach in the state of Rio Grande do Norte, it is hoped that the results of the present study can contribute to the establishment of management measures for the activity and conservation strategies for the species.

Persistent organic pollutants and chlorpyrifos in tissues of a histotrophic viviparous species, the Southern Eagle Ray Myliobatis goodei.

Elasmobranchs are good indicators of marine pollution as they accumulate pollutants from water and food, and occupy different trophic levels. Concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and chlorpyrifos were quantified in muscle, liver, gonads, gills, and brain in both sexes and maturity stages of the Southern Eagle Ray, Myliobatis goodei, captured in Argentine coastal waters. Moreover, possible histological alterations in the liver and gonads were analyzed. Pollutant concentrations were pervasive across all tissues, with PCBs > OCPs > chlorpyrifos. Elevated pollutant levels were notably found in the liver and gills. We identified thirty-six PCB congeners in tissues, with low-chlorine congeners prevailing. Among OCPs, ∑DDT and ∑endosulfan were predominant. Females exhibited higher pollutant levels in most tissues compared to males, except in the gonads, and adults generally displayed elevated pollutant levels. Histological analysis revealed the presence of atretic follicles and melanomacrophages (MM). Continuous monitoring of pollutant levels, alongside their effects on physiological and ecological traits, is imperative for effective management and conservation efforts.

Understanding the genetic sex-determining mechanism in Hyla eximia treefrog inferred from H-Y antigen.

Genetic sex-determining mechanisms have been extensively elucidated in mammals; however, the sex chromosomes, sex-determining genes, and gene regulatory networks involved in sex differentiation remain poorly understood in amphibians. In this study, we investigated the sex-determining mechanism in the Hyla eximia treefrog based on karyotypic analysis and identification of H-Y antigen, a sex-linked peptide that is present in the gonads of the heterogametic sex (XY or ZW) in all vertebrates. Results show a diploid chromosome number 2n = 24 with homomorphic sex chromosomes. The heterogametic sex, ZW-female, were hypothesized based on H-Y antigen mRNA expression in female gonads (24,ZZ/24,ZW). The treefrog H-Y peptide exhibited a high percentage of identity with other vertebrate sequences uploaded to GenBank database. To obtain gene expression profiles, we also obtained the coding sequence of the housekeeping Actb gene. High H-Y antigen expression levels were further confirmed in ovaries using real-time polymerase chain reaction (RT-PCR) during non-breeding season, we noted a decrease in the expression of the H-Y antigen during breeding season. This study provides evidence that sex hormones might suppress H-Y antigen expression in the gonads of heterogametic females 24,ZW during the breeding season. These findings suggest that H-Y gene expression is a well-suited model for studying heterogametic sex by comparing the male and female gonads.

Histopathology and changes in the expression of metallothioneins, heat shock proteins and inducible nitric oxide synthase in Prochilodus costatus from a neotropical river contaminated by heavy metals.

The most recent dam rupture in Brazil released tons of mining tailings into the upper course of the Paraopeba River, affecting this river in an unprecedented way. The present study aimed to evaluate the influence of heavy metals on Prochilodus costatus, an important commercial species in Brazil, four years after the dam colapse. To this end, biomarkers of heavy metals, oxidative stress, and environmental stress were analyzed, and histological analyses of target organs were performed. The results demonstrated critical contamination of fish from the Paraopeba River. Increased expression of Metallothioneins - MTs, Heat Shock Protein - HSP70, and inducible nitric oxide synthase - iNOS, as well as greater rates of histological changes in the liver, spleen, and gonads, were observed in P. costatus. These findings demonstrate that, despite past contamination, the metals present in mining tailings have significantly increased the contamination of the Paraopeba River basin.

Unveiling the reproductive and migrative behavior of Trichiurus lepturus in a tropical environment: Insights and implications.

This study aimed to understand the reproductive biology and migrative behavior of the largehead hairtail Trichiurus lepturus in a tropical area, specifically off Pernambuco coast, northeastern Brazil. Commercial catches from fish corrals provided samples for analysis, including measurements, weight recording, and examination of gonads to determine its maturation stage. Reproductive analyses were performed, such as sex ratio, gonado-somatic index, and sizes at first maturity. There was a slightly higher proportion of females among the 141 largehead hairtail specimens analysed. No significant differences were observed in length distributions between males and females. However, during the winter, significant differences were observed in length distributions for grouped sexes. The species exhibited a seasonal migratory pattern, with a higher presence on the continental shelf during the winter. The study identified strategic allocation of energy in feeding activities and temporal spacing of reproductive cycles, as indicated by the sex ratio and abundance of individuals during different seasons. Fish corrals probably do not harm largehead hairtail population off the southwestern Atlantic tropical coast, with minimal capture of individuals below the size of first maturity. The insights of the study into reproductive and migration patterns contribute to future assessments and management strategies for this species and corral fisheries.

Biological patterns of reproduction of the Brazilian sardine Sardinella brasiliensis in the purse seine fishery of Southwest Atlantic Ocean: A long-term assessment.

Recent estimates of the size at first maturity (L50) of Sardinella brasiliensis showed contradictory results with a decreasing in the fish stock biomass encompassed by increasing values of L50. The methodological approach used hereby allowed to separate sardines classified in the virginal maturity stage from those categorized in the recovery stage, and ready for one next spawning event. This study evaluated the hypothesis of the existence of separated stocks experiencing distinct environmental conditions and fishing pressures which may have altered L50 estimates using a robust dataset based on biological samples collected along the entire species distribution area in the southeast-south Brazilian coast [Rio de Janeiro (RJ), São Paulo (SP), Paraná (PR), Santa Catarina (SC) and Rio Grande do Sul (RS)] between 2000 and 2018. A reclassification of the gonadal maturity stages provided a more realistic estimate of L50. Combining biological, reproductive, fishing data and the mean temperature of the catch (MTC), the leave-one-out classification correctly re-assigned individuals with an overall accuracy of 85% [100% (RJ), 45% (SP), 99% (PR), 99% (SC) and 82% (RS)]. The connectivity between the local populations of S. brasiliensis off RJ (23°S) and the southern populations is limited, contrasting to spatial structured semi-discrete population-units found between SP and RS (24°S-30°S). The northern extreme population-unit (RJ, 22°S-23°S) showed an expressive reduction of L50, and a negative correlation was detected between the increasing MTC values and the abundance of early maturing individuals and recruits of the species. Stock specific L50 estimates seemed to act as indicators of long term environmental fluctuations.

Population structure and reproductive indicators of the surubim Pseudoplatystoma punctifer (Siluriformes, Pimelodidae) in the São Miguel River, Amazon basin, Brazil.

Fish is an important source of food and income for a significant portion of the Amazonian population, especially those who live along the rivers and lakes in the region. Pseudoplatystoma punctifer (Castelnau, 1855), known as surubim, is a species of Neotropical catfish widely exploited by fisheries and commercially valuable in the Guaporé River basin, Brazil. However, population dynamics are poorly known in the region. To understand the population structure and reproductive biology aspects of the surubim, monthly experimental fisheries were carried out in the São Miguel River, state of Rondônia, Brazil, between August 2020 and July 2021. The captured fish were weighed, and its gonads were removed and weighed for histological analyses (microscopic description) and classification of the maturation stages (macroscopic description). The collected gonads were fixed in 10% buffered formalin, dehydrated, cut into 4-µm-thick sections, and stained with hematoxylin and eosin. A total of 34 individuals were collected (20 females and 14 males), showing positive allometric growth and condition factor from 0.81 to 1.79 for females and males, respectively. Females were larger in size and weight than males. P. punctifer reaches its first maturation at an average length of 68.30 cm, indicating the importance of respecting the minimum capture size as an alternative to ensure the natural stocks of this fishery resource in the region. The results provide support for the establishment of public policies and actions for conservation, management, and regulation of fishing.

Morphochromatic spectrum through gonad development stages of the razor surgeonfish, Prionurus laticlavius (Valenciennes, 1846) (Actinopterygii: Acanthuriformes).

Gonad development stages (GDS) are a critical tool that can be easily applied in fisheries to visually discriminate mature from immature organisms and assess their reproductive condition. This study proposes a morphochromatic scale to define gonad development stages for razor surgeonfish (Prionurus laticlavius) based on morphological and structural assessments of the gonad, histologically validated using multivariate dummy matrices modeled through multiple linear regression analyses. Gonads of 271 specimens were photographed prior to preservation to describe their shape, size, color, and turgor for morphochromatic analysis. Later, gonads were processed using standard histological methods. An oocyte growth scale was designed based on oocyte diameter and follicular wall thickness for each stage. In addition, five morphochromatic gonad development stages were histologically validated: immature, developing, spawning capable, regressing, and regenerating. Morphochromatic variations were observed in the last three stages in both sexes. Results show that gonad morphology and structure of P. laticlavius are similar to those of other acanthurids, albeit with some asymmetric and morphological differences, as well as gonad morphochromatic in both sexes. These findings confirm that maturation is species-specific. Also, although not a critical character, gonad colouration was found to play a major role in distinguishing between gonad development stages along with shape, size, vascularity (females), and folds (males). Therefore, gonad colouration should not be entirely overlooked because doing so may lead to errors in determining sexual maturity stages.

Chlorothalonil as a potential endocrine disruptor in male zebrafish (Danio rerio): Impact on the hypothalamus-pituitary-gonad axis and sperm quality.

Chlorothalonil is a broad-spectrum organochlorine fungicide widely employed in agriculture to control fungal foliar diseases. This fungicide enters aquatic environments through the leaching process, leading to toxicity in non-target organisms. Organic contaminants can impact organism reproduction as they have the potential to interact with the neuroendocrine system. Although there are reports of toxic effects of chlorothalonil, information regarding its impact on reproduction is limited. The aim of the present study was to evaluate the influence of chlorothalonil on male reproductive physiology using the zebrafish (Danio rerio) as ecotoxicological model. Zebrafish were exposed for 7 days to two concentrations of chlorothalonil (0.1 and 10 µg/L) along with a control group (with DMSO - 0.001%). Gene expression of hypothalamus-pituitary-gonad axis components (gnrh2, gnrh3, lhr, fshr, star, hsd17b1, hsd17b3, and cyp19a1), as well as hepatic vitellogenin concentration were assessed. In sperm cells, reactive oxygen species (ROS) content, lipid peroxidation (LPO), mitochondrial functionality, and membrane integrity and fluidity were evaluated. Results indicate that exposure to the higher concentration of chlorothalonil led to a reduction in brain gnr2 expression. In gonads, mRNA levels of lhr, star, and hsd17b1 were decreased at both chlorothalonil concentrations tested. Similarly, hepatic vitellogenin concentration was reduced. Regarding sperm cells, a decreased ROS level was observed, without significant difference in LPO level. Additionally, a higher mitochondrial potential and lower membrane fluidity were observed in zebrafish exposed to chlorothalonil. These findings demonstrate that chlorothalonil acts as an endocrine disruptor, influencing reproductive control mechanisms, as evidenced by changes in expression of genes HPG axis, as well as hepatic vitellogenin concentration. Furthermore, our findings reveal that exposure to this contaminant may compromise the reproductive success of the species, as it affected sperm quality parameters.

Gonadal Morphology of Stillborn Hawksbill Sea Turtle (Eretmochelys imbricata) Hatchlings.

This study aimed to investigate sexual dimorphism in stillborn hawksbill sea turtles (Eretmochelys imbricata) through gonadal morphological characterizations. Macroscopic, light microscopy, and transmission electron analyses were performed for 30 gonad-mesonephros complexes. Female gonads were spindle-shaped and present a translucent whitish appearance with a grainy texture. Male gonads were approximately ovoid with a smooth opaque white surface. A primary sexual difference concerns different marrow structures, with females presenting organized cellularity featuring oocytes, lacunae, and blood vessels, while males presented a distinct organizational medulla pattern marked by testicular cords extending throughout the gonad length. Ultrastructurally, female's stroma presented interstitial cells and an abundant cytoplasm rich in electrodense droplets and large oval germline cells, with a conspicuous and noncentral nucleus. Males, on the other hand, presented testicular cord cells containing small amounts of heterochromatin and approximately triangular apical and basal cytoplasms with an evident nucleolus characteristic of support cells. Additionally, there were cells with a large spherical nucleus compared with the cell size and a relatively scarce cytoplasm, identified as gonocytes. These findings indicate that macroscopic, microscopic, and ultrastructural evaluations are effective and reliable techniques for the sexual identification of stillborn E. imbricata hatchlings.

Three different seasonally expressed opsins are present in the brain of the Eared Dove, an opportunist breeder.

Birds living at high latitudes perceive the photoperiod through deep-brain photoreceptors (DBP) located in deep-brain neurons. During long photoperiods the information transmitted by these photoreceptors increases the activity of the hypothalamic-pituitary-gonadal (HPG) axis, leading to gonadal development. The presence of photopigments such as VA-Opsin, Opn4, Opn5 and Opn2 in brain areas implicated in reproductive behaviors has been firmly established in several avian species with seasonal breeding, whereas their existence in opportunistic breeding birds remains unconfirmed. The Eared Dove is an urban and peri-urban dove that breeds throughout the year. Males of this species do not exhibit the typical gonadal regression/recrudescence cycle, thus posing the question of what occurs upstream of the HPG axis. We addressed this issue by first studying the presence of diverse opsins located in DBP in the brains of Eared Dove males and whether these photopigments changed their expression throughout the year. We carried out an immunohistochemistry analysis on three different opsins: Opn2 (rhodopsin), Opn3 and Opn5. Our results demonstrate the discrete neuroanatomical distribution of these opsins in the brain of Eared Dove males and strongly indicate different seasonal expressions. In the anterior region of the hypothalamus, Opn2-positive cells were detected throughout the year. By contrast, Opn5 was found to be strongly and seasonally expressed during winter in the anterior and the hypothalamic region. Opn3 was also found to be significantly and seasonally expressed during winter in the hypothalamic region. We thus demonstrate for the first time that males of the Eared Dove, have three different deep-brain opsin-expressing photoreceptors with differential location/distribution in the anterior and hypothalamic region and differential seasonality. The persistence of Opn2 and the strong seasonal expression of nonvisual photopigments Opn3 and Opn5 in two areas of the avian brain, which are associated with reproduction, could be the primary distinction between seasonal and opportunistic breeders.

hsd17b1 is a key gene for ovarian differentiation of the Siberian sturgeon.

This is the first work using gonads from undifferentiated, genetically-sexed Siberian sturgeon describing expression changes in genes related to steroid synthesis and female and male sex differentiation. One factor identified as relevant for ovarian differentiation was the gene coding for the enzyme Hsd17b1, which converts estrone into estradiol-17ß. hsd17b1 was highly activated in female gonads at 2.5 months of age, around the onset of sex differentiation, preceding activation of two other genes involved in estrogen production (cyp19a1 and foxl2). hsd17b1 was also strongly repressed in males. Two known foxl2 paralogs are found in Siberian sturgeon-foxl2 and foxl2l-but only foxl2 appeared to be associated with ovarian differentiation. With regard to the male pathway, neither 11-oxygenated androgens nor classic male genes (amh, dmrt1, sox9, and dhh) were found to be involved in male sex differentiation, leaving open the question of which genes participate in early male gonad development in this ancient fish. Taken together, these results indicate an estrogen-dependence of female sex differentiation and 11-oxygenated androgen-independence of male sex differentiation.

Histología testicular y morfología de la vejiga natatoria del pez neotropical Plagioscion magdalenae (Acanthuriformes: Sciaenidae): implicaciones en su taxonomía y distribución / Testicular histology and morphology of the swim bladder of the neotropical fish Plagioscion magdalenae (Acanthuriformes: Sciaenidae): implications in taxonomy and distribution

Introducción: La Pácora (Plagioscion magdalenae) es una especie nativa de Colombia y en categoría de casi amenazada a nivel del país, de la que poco se conoce acerca de las estructuras con aporte etológico en su historia de vida. Objetivo: Analizar el desarrollo gonadal relacionado con la espermatogénesis de P. magdalenae y las implicaciones taxonómicas a partir de la vejiga natatoria. Métodos: Realizamos siete muestreos en dos periodos climáticos: el primero en octubre de 2019 a febrero de 2020 de recolectas bimensuales y la segunda de octubre 2020 a enero 2021 de recolectas mensuales; con el fin de abarcar cada momento del pulso de inundación de la cuenca baja del Magdalena. Describimos la histomorfología testicular y las características macroscópicas de la vejiga natatoria de la especie. Además, analizamos aspectos como relaciones morfométricas, clases de tallas por sexos, la proporción sexual y la época de madurez sexual. Resultados: Analizamos 142 ejemplares y 4 intervalos de tallas fueron establecidos (entre 145 y 575 mm LE), 66 fueron machos y 73 hembras con una proporción sexual global 1.1:0.9 (hembra-macho) sin diferencias. Los machos tienen testículos de tipo tubular, protegidos por el peritoneo que se encuentra recubierto por la musculatura sónica de la vejiga natatoria, la cual posee forma de ''zanahoria'' sin apéndices, con dos bandas laterales de músculos intrínsecos (promedio entre 6.75 cm de largo y 1.48 cm de ancho) unidos por una aponeurosis y que solo se encuentran en machos sexualmente maduros. Conclusión: Los testículos poseen una organización de tipo lobular irrestricto y la espermatogénesis se da en lóbulos seminíferos. La vejiga natatoria de la Pácora es simple y no tiene estructuras accesorias. La distribución geográfica de P. magdalenae se restringe a la cuenca del río Magdalena en Colombia.

Introduction: The Pácora (Plagioscion magdalenae) is a species native to Colombia and in near-threatened category at the country level, of which little is known about the structures with ethological contribution in its life history. Objective: To analyze the gonadal development related to spermatogenesis of P. magdalenae and the taxonomic implications from the swim bladder. Methods: We collected seven samples in two climatic periods: the first from October 2019 to February 2020 of bimonthly collections, and the second from October 2020 to January 2021 of monthly collections; to cover every moment of the flood pulse of the lower Magdalena basin. We described the testicular histomorphology and macroscopic characteristics of the swim bladder of the species. In addition, we analyzed aspects such as morphometric relationships, size classes by sex, sex ratio and time of sexual maturity. Results: We analyzed 142 specimens and established 4 size intervals (between 145 and 575 mm SL), 66 were males and 73 females with an overall sex ratio of 1.1:0.9 (female-male) with no differences. Males have tubular testes protected by the peritoneum covered by the sonic musculature of the swim bladder, which has a ''carrot'' shape without appendages, with two lateral bands of intrinsic muscles (average between 6.75 cm long and 1.48 cm wide) connected by an aponeurosis and found only in sexually mature males. Conclusion: The testes have an unrestricted lobular organization and spermatogenesis occurs in the seminiferous lobes. The swim bladder of the Pácora is simple and has no accessory structures. The geographic distribution of P. magdalenae is restricted to the Magdalena River basin in Colombia.

First evidence of gonadal hybrid dysgenesis in Chagas disease vectors (Hemiptera, Triatominae): gonad atrophy prevents events of interspecific gene flow and introgression.

BACKGROUND: Hybridization events between Triatoma spp. have been observed under both natural and laboratory conditions. The ability to produce hybrids can influence different aspects of the parent species, and may even result in events of introgression, speciation and extinction. Hybrid sterility is caused by unviable gametes (due to errors in chromosomal pairing [meiosis]) or by gonadal dysgenesis (GD). All of the triatomine hybrids analyzed so far have not presented GD. We describe here for the first time GD events in triatomine hybrids and highlight these taxonomic and evolutionary implications of these events. METHODS: Reciprocal experimental crosses were performed between Triatoma longipennis and Triatoma mopan. Intercrosses were also performed between the hybrids, and backcrosses were performed between the hybrids and the parent species. In addition, morphological and cytological analyzes were performed on the atrophied gonads of the hybrids. RESULTS: Hybrids were obtained only for the crosses T. mopan♀ × T. longipennis♂. Intercrosses and backcrosses did not result in offspring. Morphological analyses of the male gonads of the hybrids confirmed that the phenomenon that resulted in sterility of the hybrid was bilateral GD (the gonads of the hybrids were completely atrophied). Cytological analyses of the testes of the hybrids also confirmed GD, with no germ cells observed (only somatic cells, which make up the peritoneal sheath). CONCLUSIONS: The observations made during this study allowed us to characterize, for the first time, GD in triatomines and demonstrated that gametogenesis does not occur in atrophied gonads. The characterization of GD in male hybrids resulting from the crossing of T. mopan♀ × T. longipennis♂ highlights the importance of evaluating both the morphology and the cytology of the gonads to confirm which event resulted in the sterility of the hybrid: GD (which results in no gamete production) or meiotic errors (which results in non-viable gametes).

Cyp19 expression and sex change timing in captive-bred false clownfish.

The false clown anemonefish (Amphiprion ocellaris) is a protandrous hermaphrodite with a distinctive reproductive behavior. This study elucidates the genetic mechanisms and timing of sex changes in captive-bred A. ocellaris by examining the expression of key genes involved in this process, specifically cyp19a1a and cyp19a1b. Gonadal histological analyses and gene expression studies were conducted on subadult fish paired for 0, 1, 2, 3, 4, 5, and 16 months. Our findings reveal that alterations in cyp19 gene expression coincide with a pairing period starting after 3 months. Both cyp19a1a and cyp19a1b expression levels were significantly elevated in paired females compared with their male counterparts and unpaired controls. Histological investigations demonstrated that sex conversion to females occurred during the 3-month pairing period. This study highlights the crucial role of cyp19a1a and cyp19a1b in the sex change process of A. ocellaris and indicates that a minimum of 5 months of pairing is necessary for completing the sex change.

Thyroid axis participates in high-temperature-induced male sex reversal through its activation by the stress response.

Environmental changes alter the sex fate in about 15% of vertebrate orders, mainly in ectotherms such as fish and reptiles. However, the effects of temperature changes on the endocrine and molecular processes controlling gonadal sex determination are not fully understood. Here, we provide evidence that thyroid hormones (THs) act as co-players in heat-induced masculinization through interactions with the stress axis to promote testicular development. We first demonstrated that the thyroid axis (through thyroid-related genes and T3 levels) is highly active in males during the gonadal development in medaka (Oryzias latipes). Similarly, T3 treatments promoted female-to-male sex reversal in XX embryos. Subsequently, embryonic exposure to temperature-induced stress up-regulated the genes related to the thyroid and stress axes with a final increase in T3 levels. In this context, we show that blocking the stress axis response by the loss of function of the corticotropin-releasing hormone receptors suppresses thyroid-stimulating hormone expression, therefore, heat-induced activation of the thyroid axis. Thus, our data showed that early activation of the stress axis and, in consequence, the TH axis, too, leaves us with that both being important endocrine players in inducing female-to-male reversal, which can help predict possible upcoming physiological impacts of global warming on fish populations.

Gonadal morphogenesis in the South American toad Rhinella Arenarum (Anura, Bufonidae) unveils an extremely delayed rate of sex differentiation.

Among anurans, Bufonids are recognized for their retarded sex differentiation. However, few studies have addressed gonadal morphogenesis in this family. Here, we analyzed the early gonadogenesis in laboratory-reared Rhinella arenarum. Few germ cells were identified in the genital ridge at Gosner stage 26. At metamorphosis, somatic cells and germ cells were observed in the outer region of the undifferentiated gonad, whereas the central region was occupied by stromal tissue. A cortico-medullary organization was first recognized on Day 7 postmetamorphosis. The cortex was composed of germ cells and encompassing epithelial cells, whereas the medulla contained cells presumptively derived from the coelomic epithelium. Medullary somatic cells formed metameric knots along the length of the undifferentiated gonad. Consequently, a series of 12-14 gonomeres became recognizable externally. The first sign of ovarian differentiation was observed on Day 15 postmetamorphosis, when a cavity was formed within each gonomere. In contrast, testes were recognized by a uniform distribution of germ cells and intermingled somatic cells, as the division into cortex and medulla was lost. By Day 50 postmetamorphosis, the gonadal metameric organization was still apparent both in the ovaries and testes. Follicles containing diplotene oocytes were observed within the ovary. In the testis, an incipient lobular architecture was recognized without initiation of meiosis within the seminiferous cords. These observations reveal an extremely delayed gonadal development in R. arenarum, not reported previously for other anuran species. In addition, the late differentiation of the gonads contrasted with the early appearance of follicles in the Bidder's organ. Lastly, we observed that delayed metamorphs exhibited an undifferentiated gonad, demonstrating that gonadogenesis in this species is more dependent on somatic development than on age.

Temporal and inter-individual changes in the integrated biochemical condition of the gonads of female swordfish (Xiphias gladius) from the Southeastern Pacific Ocean.

The integrated biochemical condition (IBC) of gonads is closely related to the reproductive success of highly migratory marine species. The IBC of gonads can be influenced not only by size and/or age, but also by environmental conditions. Here, female swordfish, Xiphias gladius, that migrate to temperate regions with a marked seasonality (e.g., the Southeastern Pacific Ocean, SEPO) were compared in relation to the IBCs (lipids, proteins, glucose and, fatty acid profiles) of their gonads; individuals with two body size ranges and distinct degrees of sexual maturity were evaluated, and considered as: small and/or virginal (SV: <170 cm lower jaw fork-length (LJFL), oocyte size (OS) <0.08 mm) vs large and/or maturing females (LM: >190 cm LJFL, OS >0.133 mm). This comparison was conducted in two environmentally contrasting seasons (winter vs spring). Our results showed that the gonadosomatic index (GSI) was significantly higher in LM than SV. Lipid contents varied significantly between seasons and body sizes. The highest lipid concentrations were recorded in the spring in large females. No significant differences were found when comparing the protein and glucose contents of the two evaluated seasons or body size ranges of the studied females. In turn, the fatty acid (FA) profiles of female gonads significantly varied for both seasons and body size ranges. A high content of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) and poly-unsaturated fatty acids (PUFAs) were recorded in female gonads in the spring. The SFAs C16:0 and C18:0, the MUFA C18:1n9, and the essential PUFA C22:6n3 were the main contributors to the observed differences between spring and winter. These results could be used as indicators of the nutritional condition and health status of swordfish individuals. Hence, the IBC of female swordfish gonads have great potential to aid in estimating survival rates and stock abundances of this species. The integration of this information constitutes an asset in fishery management models with an ecosystem approach.