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Fertilization, the basis for sexual reproduction, culminates in the binding and fusion of sperm and egg. Although several proteins are known to be crucial for this process in vertebrates, the molecular mechanisms remain poorly understood. Using an AlphaFold-Multimer screen, we identified the protein Tmem81 as part of a conserved trimeric sperm complex with the essential fertilization factors Izumo1 and Spaca6. We demonstrate that Tmem81 is essential for male fertility in zebrafish and mice. In line with trimer formation, we show that Izumo1, Spaca6, and Tmem81 interact in zebrafish sperm and that the human orthologs interact in vitro. Notably, complex formation creates the binding site for the egg fertilization factor Bouncer in zebrafish. Together, our work presents a comprehensive model for fertilization across vertebrates, where a conserved sperm complex binds to divergent egg proteins—Bouncer in fish and JUNO in mammals—to mediate sperm-egg interaction. [Display omitted] • AlphaFold-Multimer predicts trimer formation of sperm Izumo1, Spaca6, and Tmem81 • Tmem81 is essential for male fertility in fish and mice • Trimer proteins interact in zebrafish sperm, and human orthologs interact in vitro • The zebrafish trimer interacts with Bouncer on the egg AlphaFold-Multimer predicts complex formation by three sperm proteins conserved in vertebrates. Their interaction is experimentally confirmed and shown to bridge sperm and egg during fertilization by interacting with evolutionarily unrelated egg proteins. [ABSTRACT FROM AUTHOR]

Electrofishing is a widely preferred method in freshwater. Freshwater conducts electric current at low levels. Therefore, a relatively high voltage electric current is applied in these waters. In this study, the effects of changes in the structure of the water after the electric current applied to the water on gamete quality and embryo-larvae survival rates were investigated. Water samples were collected from the central region of the tank (N), as well as from the positive (+) and negative (-) poles following the application of an electric current to the well water at 165 volts and 3 mA for durations of 15 and 30 minutes. Sperm kinematic velocity parameters, fertilization and hatching rates were determined to be at the highest level in the group where electric current was applied for 30 minutes and water samples were taken from the middle of the tank, 30 (N), were used (P<0.05). Furthermore, it was observed that the Chemical Oxygen Demand value was one of the values lowest in the groups where sperm motility results were found to be the highest (P<0.05). Regardless of the duration of electric current application, it was found that the dissolved oxygen value of the water samples collected from the positive poles was similar to the control group, but higher than the negative poles. In conclusion, the application of electric current resulted in variations in both the sperm kinematic parameter values and the water parameters among the samples collected from different poles. However, there was no statistically significant difference in fertilization and hatching rates between the groups (P>0.05). [ABSTRACT FROM AUTHOR]

Spiny Eel (Mastacembelidae family) is a freshwater fish that lives in various types of waters. Spiny eel is a potential fish that is still very rarely researched and developed. Continuous fishing has resulted decreasing number on spiny eel in the nature. This study aims to find out how the ecological and biological aspect of spiny eel in the Elo River, Magelang City, Central Java. This study used a random sampling method with minimum sample of 30 spiny eel from the wild. Data collection techniques were carried out by direct observation and by conducting a review of previous research literatures. The research results showed that the habitat of the spiny eel in the Elo River was suitable for the spiny eel to live in. There were three types of spiny eel obtained, namely Macrognathus circumcinctus, Macrognatus maculatus dan Mastacembelus unicolor with a total number of 36. Spiny eel has a negative allometric length growth pattern. The sex ratio of the spiny eel is 1.4:1. The majority of gonadal maturity level are in second stage. The average of GSI (gonadosomatic index) of male and female were 0.727% and 1.621%. Fecundity of female fish ranged from 2614 – 46233 eggs. Theoritical age is divided into three, Macrognathus circumcinctus, Macrognatus maculatus dan Mastacembelus unicolor have the average of 3.8, 7.27 and 4.67 months. Spiny eel really loved worms and crustaceans (crab and shrimp / prawn) as their main feed (IP 38.83%) and (IP 39.67%) then shrimp / prawn as their complementary feed (IP 14,63%) aquatic microinvertebratae for their additional feed (IP 4.73%) and left with unidentified feed (IP 1.15%). [ABSTRACT FROM AUTHOR]

Coral ornamental fish become potential fishery commodities, providing opportunities and challenges in managing fishery resources in Indonesia. This activity has long been done and has become one cause of damage to coral reefs in Indonesia. Changes in paradigm and technology currently applied in Indonesia are expected to provide a gradual regulatory and coral reef ecosystem improvement. The commercial trade of ornamental fish requires attention and rigorous regulation. The marine ornamental fish trade activity is expected to improve and drive the coastal communities' economy. The significant increase in exploitation is expected to be controlled with the right regulations. This regulation must refer to the concept of sustainable development established through the Sustainable Development Goals (SDGs), especially SDGs number 14 concerning life underwater. The existence of reef fish is enough to provide economic movement, which continues to heat up, especially after the pandemic and the reopening of flights and export activities abroad. However, multi-stakeholders should ratify the concept of sustainability and environment-friendliness. Support from the government, academia, industry, and community groups must be aligned and in tune to achieve sustainable development goals. Providing accurate information related to the biological characteristics of reef fish is an essential contribution for researchers that can be used directly by the community. Thus, the exploitation of reef fish can align with efforts to conserve coral reef ecosystems closely related to global warming and climate change. [ABSTRACT FROM AUTHOR]

Macrognathus aculeatus is a local fish from the Bengawan Solo and Brantas Rivers that is threatened with extinction. Due to the lack of literacy on the biology of this fish. Biological parameters can be used to determine the condition of this fish in nature. Field observations at five stations from the two rivers were conducted to obtain samples. Biological and reproductive parameters such as weight and length, gonad maturity level (GML), Gonadosomatic Index (GSI), Hepatosomatic Index (HSI), and Condition Factor (CF) were the parameters observed in this study. All data obtained were presented as mean and standard deviation. Furthermore, analysis of variance was conducted using ANOVA (p < 0.05) to determine differences in samples from each observation station. The results showed that some biological factors had significant results (p < 0.05) on Gonadosomatic Index and Hepatosomatic Index). However, there was no significant difference (p > 0.05) in the condition factor. On the other hand, there were significant differences (p < 0.05) in body weight, total length, ovary weight, and fecundity parameters across all sampling sites. [ABSTRACT FROM AUTHOR]

Quantitative adverse outcome pathways (qAOPs) describe the response–response relationships that link the magnitude and/or duration of chemical interaction with a specific molecular target to the probability and/or severity of the resulting apical‐level toxicity of regulatory relevance. The present study developed the first qAOP for latent toxicities showing that early life exposure adversely affects health at adulthood. Specifically, a qAOP for embryonic activation of the aryl hydrocarbon receptor 2 (AHR2) of fishes by polycyclic aromatic hydrocarbons (PAHs) leading to decreased fecundity of females at adulthood was developed by building on existing qAOPs for (1) activation of the AHR leading to early life mortality in birds and fishes, and (2) inhibition of cytochrome P450 aromatase activity leading to decreased fecundity in fishes. Using zebrafish (Danio rerio) as a model species and benzo[a]pyrene as a model PAH, three linked quantitative relationships were developed: (1) plasma estrogen in adult females as a function of embryonic exposure, (2) plasma vitellogenin in adult females as a function of plasma estrogen, and (3) fecundity of adult females as a function of plasma vitellogenin. A fourth quantitative relationship was developed for early life mortality as a function of sensitivity to activation of the AHR2 in a standardized in vitro AHR transactivation assay to integrate toxic equivalence calculations that would allow prediction of effects of exposure to untested PAHs. The accuracy of the predictions from the resulting qAOP were evaluated using experimental data from zebrafish exposed as embryos to another PAH, benzo[k]fluoranthene. The qAOP developed in the present study demonstrates the potential of the AOP framework in enabling consideration of latent toxicities in quantitative ecological risk assessments and regulatory decision‐making. Environ Toxicol Chem 2024;43:2145–2156. © 2024 SETAC [ABSTRACT FROM AUTHOR]

Copyright of Caspian Journal of Environmental Sciences is the property of University of Guilan & Association of Universities of the Caspian Region States and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Anatolian Environmental & Animal Science is the property of Bulent Verep and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Peatlands play an important role in the global environment and the well-being of humans by providing valuable ecosystem services. Yet, anthropogenic activities pose significant hazards for peatland management, including low levels of community participation due to lack of awareness and financial incentives. Understanding the social–cultural and economic value of these ecosystems will raise awareness to protect these important ecosystems. Here, we estimated a total economic value (TEV) of peatland ecosystem services and examined relationships between the TEV and landscape characteristics in Riau province, Indonesia. A questionnaire was used to investigate household socioeconomics, perception of peatland importance, peatland product collection, and willingness to pay for habitat and biodiversity protection from May to June 2023. A total of 200 household individuals (92% confidence) in five villages across distinct landscapes in the Sungai Kiyap-Sungai Kampar Kiri Peatland Hydrological Unit participated in the survey. The respondents obtained numerous advantages from the peatlands with an estimated TEV of USD 3174 per household per year (about 1.3 times their annual income). Approximately 81% showed a use value, especially food provisioning from fish and soil fertility. To a lesser extent, non-use values included a habitat for endemic and endangered species, biodiversity conservation for future generations, and community bonds with sacred forests. The landscape characteristics, illustrating habitat types, biophysical conditions, and property rights regimes, interplay with the relative benefits derived from the peatlands. Proximity to secondary peat swamp forests and riparian zones, especially within protected areas, enhanced economic value. Protected area co-management is essential to balance peatland conservation with sustainable livelihoods. Primary forests need restrictive protection. Meanwhile, buffer zone designation and agroforestry practices, especially in the peatland–farm interface, reduce land use tensions and promote local stewardship. This study can be used as a reference by planners and policymakers to recognize factors that promote effective peatland management, especially those that balance ecosystem protection and livelihood maintenance. [ABSTRACT FROM AUTHOR]

17β-Estradiol (E2) has been widely detected in natural water and treatment with E2 induces potential endocrine disrupting effects in fish. However, effects on fish fecundity and steroid system after treatment with environmentally relevant concentrations of E2 for the full sexual maturation cycle remain unclear. In this study, zebrafish were treatment with 0, 10 or 100 ng/L E2 from embryo to adult stage, and effects on gonadal development and differentiation, steroid hormone levels, transcription of genes associated with the hypothalamic-pituitary-gonadal-liver (HPG) axis in adults and fertilization rate of offspring were assessed. The results showed that treatment with E2 lead to increased number of feminization in zebrafish. In females, E2 decreased cumulative amount of spawning and inhibited the maturation of oocyte. In males, E2 inhibited the maturation and motility of sperm, as well as decreased the movement speed of sperm. These adverse effects on sperm might be responsible for the reduced fertilization observed in offspring. In addition, treatment with E2 changed the levels of steroid hormones in zebrafish gonad and altered the transcriptional levels of genes associated with HPG axis, which is responsible for the regulation of germ cells maturation and gonadal development in zebrafish. Overall, these results suggested that treatment with environmentally relevant concentrations of E2 for the full sexual maturity cycle resulted in adverse effects on reproduction in zebrafish. [Display omitted] [ABSTRACT FROM AUTHOR]

Sex control techniques are in great demand for aquaculture because of the huge benefits of mono-sex production. In a previous study on yellow catfish (Tachysurus fulvidraco), intersex individuals were produced by administrating 17a-methyltestosterone (MT) or aromatase inhibitor letrozole (LZ). The ovarian and testicular portions of intersexual gonads developed well and were completely separated, arousing our interest in producing selffertilizable fish and clone-like fish populations. In this study, yellow catfish fry were treated with a combination of MT and LZ at a low dose (5 mg kg-1 MT, 300 mg kg-1 LZ) at a low water temperature (27.0 °C, mixed sexproducing temperature, LL group) and a high temperature (33.5 °C, male-producing temperature, HL group), and with a high dose (10 mg kg-1 MT, 600 mg kg-1 LZ) at a low water temperature (LH group), during 12-65 days post-hatching, the critical period of sex differentiation. Both XX and XY intersex were produced with different percentages at the same time through co-treatment with MT and LZ, with or without the help of male-producing temperature. The highest percentage of XY intersex (53% in XY, 36% in XX and XY) and XX intersex (47% in XX, 25% in XX and XY) was produced in LH and HL groups, respectively. Results of gonadal morphology, histology, and sperm dynamic analysis indicate that some XX and XY intersex individuals were capable of self-fertilization through artificial insemination. The reproductive performance of these intersex individuals was then investigated by injecting spawning agents, dissecting gonads, and artificially fertilizing eggs with their own sperm. The XX, XY, and YY genotypic individuals were produced by the self-fertilization of XY intersex individuals. The present study successfully produced high percentages of XX and XY intersex and conducted self-fertilization by mating the eggs and sperm of a single intersex individual. Self-fertilization in fish will show great potential in aquaculture genetics and breeding, for example, generating highly homozygous (or "clonal") genetic material, producing mono-sex populations, and identifying unknown sex determination modes. In particular, the cloning method of producing genetic materials will be greatly beneficial for maintaining advantageous traits through self-fertilization generation after generation. [ABSTRACT FROM AUTHOR]

Background: Fecundity is an important parameter in fisheries that predicts the reproductive capability of fish stock. Information on the fecundity of Common carp is helpful in estimating the amount of offspring produced in spawning season, which is essential for the stock assessment of the species. Assessment of the fecundity of a fish is essential for evaluating the commercial potentialities of its stock, life history, practical culture and actual management of the fishery. Common carp is a commercially important fish which has the potential to meet the demand of food in the country. Scanty of data is available on fecundity parameter of common carp in Kashmir waters. Therefore, this research work aims to estimate the fecundity of Common carp collected from the Dal lake of Kashmir. Methods: The present study aims to estimate the fecundity of Common carp, [Cyprinus carpio var. communis] existing in Dal Lake, Kashmir. The 30 fish samples were collected once every month from the month of January 2018 to December 2018. Fishes were brought to Fisheries Resource Management (FRM), Faculty of Fisheries, SKUAST-K Laboratory for the estimation of total length, weight of fishes and weight of ovaries. Gravimetric and actual counting method was used for the estimation of fecundity. Result: It was observed that the number of eggs varied from 16650 (for a fish with total length 180mm and total weight 120 g) to 129000 (for a fish with total length 430 mm and total weight 1300 g. The mean absolute fecundity was recorded as 68864.07±6563.59 for a fish with a mean total length of 301.43±13.93 mm and mean total weight of 435.1±66.51 g. The relative fecundity ranged from 99.2-240.8 and the mean relative fecundity was 185.96. Significant positive correlation was found between fish weight and absolute fecundity. (r= 0.907, p<0.01), fish length and absolute fecundity (r= 0.976, p<0.01), Ovary weight and absolute fecundity (r= 0.998, p<0.01). Relative fecundity showed a significant negative correlation with weight, length and absolute fecundity (r= -0.747, p<0.01; r= -0.419, p<0.05 and r= -0.460, p<0.05 respectively. [ABSTRACT FROM AUTHOR]

Macrognathus is a genus of eel-like fish of the family Mastacembelidae of the order Synbranchiformes. The majority of South and Southeast Asia is home to these fish. The major food category of this genus is crustaceans (such as prawns) and aquatic insects (Chaoborus spp.), while juveniles mostly consume annelids (such as earthworms). According to various studies, it was found that the male: female ratio of Macrognathus sp is roughly 1:1. Macrognathus exhibit a wide range of fecundity, and the number of ova or eggs laid by a single female depends on several variables, including size, age, species, and the ecological habitats of the fish, including the availability of food. The fecundity of these fishes is found to be high when the fish were breeding, which occurred from May through August. The average ovarian diameter of M. pancalus has been found to increase every month. In some studies, lentic habitats showed higher ova diameter than lotic habitats for Macrognathus sp. For Macrognathus sp. the males matured at lengths of 10 to 11 cm and females at lengths of 11 to 12 cm on the other hand M. aral was found to be matured at an average of 12.05 cm for males and 16.05 cm for females. [ABSTRACT FROM AUTHOR]

Climbing perch Anabas testudineus is a freshwater fish that has economic value and has been cultivated in Indonesia. However, the fish farmers face problems with high-quality larvae supply because the breeding technology for this species is not well developed. Sperm and oocyte storage technology is important information in fish breeding. Therefore, this research aims to determine the best storage temperature using the dry storage method. Six levels of storage temperatures were tested in this study, namely: 29°C (room temperature as a control), 8°C, 4°C, 0°C, - 4°C, and -8°C. The oocytes are stored at the treatment temperature for 120 minutes, where every 30 minutes the quality of the oocytes is analyzed based on fertilization and hatchability parameters. The results showed that storage temperature had a significant effect on fertility (P<0.05) but had no significant effect on hatchability or the normality of larvae (P>0.05). The highest percentage of fertility was obtained in treatment B (8°C) at 30 minutes, with a value of 50.33%; this value was significantly different with other treatments. The highest hatchability percentage value was also obtained in treatment B (8°C) at 30 minutes, with a value of 12%. This value was significantly different in treatments E (-4°C) and F (-8°C), but not significantly different with treatments A (29°C), C (4°C), and D (0°C) (P > 0.05). The direct observations on the normality of the hatched larvae showed that all larvae had a normal morphology. In general, fertility and hatchability rate decrease with decreasing temperatures. Therefore, it is concluded that climbing perch fish eggs stored using the dry method can only be stored for less than 30 minutes, where the recommended temperature was 8°C. [ABSTRACT FROM AUTHOR]

Hoplias intermedius, of the Characiformes order and Erytrinidae family, is widely distributed across South America. This commercially interesting species can reach a length of 100 cm and a weight of 15–20 kg. To evaluate the reproductive biology of H. intermedius in the São Francisco River, Brazil, 154 males and 190 females were captured bi‐monthly between September 2018 and August 2019 from the downstream regions of the Três Marias dam. Gillnets with differently sized meshes were deployed at distances of 34–54 km after the confluence with the Abaeté River (18°00′49″ S, 45°10′51″ W). Biometric data, gonadosomatic index (GSI), Fulton condition factor (K) and absolute fecundity (AF) were determined for each specimen. Gonad maturation stages and the spawning season were also established. The biometric data, GSI and K average values were relatively higher in females than in males. The reproductive peak for both sexes was reached around January/February. The mean AF was 4300.5 ± 1451.2 follicles per female. Fully developed vitellogenic follicles had a mean diameter of 1014.8 ± 250.7 μm, which is characteristic of fish with moderate fecundity. Fish of all maturation stages, from mature, spawned and spermed, occurred in all bimesters, indicating that this species reproduced throughout the year. The high frequency of spawning females throughout the year and the histological characteristics of spawned ovaries indicated that trairão H. intermedius' spawning type is partial. [ABSTRACT FROM AUTHOR]

Suckermouth armored catfish (Pterygoplichthys disjunctivus) is one of the most widespread invasive species in Vietnam. However, it is relatively unknown how the species underwent its divergent adaptations to varying local conditions and habitat types, an understanding of which is essential for managing its invasion in Vietnam. We addressed this by analyzing a large number of fish (662 samples) collected in lotic (Dinh River) and lentic (Suoi Trau Reservoir) habitats in southern Vietnam during one year. The allometric growth patterns estimated by von Bertalanffy growth functions were L t = 483 1 − e − 0.71 (t − 0.40) in Dinh River and L t = 346 1 − e − 1.01 (t − 0.62) in Suoi Trau Reservoir. The estimated fish ages were 2.9 to 4.2 years old with an average total length from 206.10 ± 2.09 mm in Suoi Trau Reservoir to 319.22 ± 3.29 mm in Dinh River. The percentage of fish with matured ovaries peaked in August (100%) and was lowest in February (<10%), indicating that these fish breed nearly all year round. The main reproductive season is April–October, with a peak in July–August, as indicated by the gonado-somatic index and monthly changes in the percentage of matured fish. The lengths at 50% maturity were 234.3 and 179.7 mm for females from lotic and lentic habitats, respectively. Lotic fish had a fecundity (4812 ± 383 oocytes/ind.) which was five times greater than that of lentic fish (841 ± 91 oocytes/ind.); however, the relative fecundity of the fish was not statistically different between the two habitats (≈13 oocytes/g). This result was consistent with the larger oocytes: 2.95 ± 0.04 and 2.58 ± 0.01 mm for fish from Dinh River and Suoi Trau Reservoir, respectively. The faster growth and bigger fish with higher fecundity in the lotic habitats suggest that their population growth can accelerate more quickly, potentially affecting local communities more than those in lentic habitats. Our study sheds light on substantial phenotypic divergences in the reproduction and growth of the suckermouth armored catfish between lotic and limnetic habitats in Vietnam. [ABSTRACT FROM AUTHOR]

We analyzed the effects of pyriproxyfen (PPF) on oxidative stress and ovarian morphology in zebrafish. PPF (10−9 M) exposure increased reactive oxygen species generation in ovaries, in association with a decrease in glutathione content. The activities of glutathione S‐transferase, superoxide dismutase, and catalase were increased, while γ‐glutamyltransferase activity was not altered by pesticide treatment. The histology of ovarian tissue showed an increase in the number of previtellogenic oocytes I, and a decrease in the rate of vitellogenic oocyte (VIT) count, suggesting inhibition of follicular maturation. An increase in the thickness of the vitelline envelope was observed in VIT, as was a tendency toward an increase in atresia in the ovary of the PPF‐treated group. These findings indicate that the deleterious effect of PPF on ovarian maturation is mediated by a redox imbalance and oxidative damage. So, PPF acts as an endocrine disruptor chemical and may compromise fish reproduction by reducing female fertility. Pyriproxyfen (PPF), an endocrine disruptor chemical, exhibits a xenoestrogen‐like effect and compromise fish reproduction by reducing female fertility. The tissue damage induced by PPF during ovarian maturation is mediated by ROS formation, GSH depletion, and activated antioxidant enzymatic systems, probably in response to the oxidative insult. The pesticide‐induced oxidative stress might affect ovarian maturation, compromising fish reproduction and fertility. [ABSTRACT FROM AUTHOR]

Fish with indeterminate fecundity spawn multiple times throughout a protracted reproductive period. During that period several ovulation events succeed one another, and different oocyte developmental stages co-occur in the ovaries with new oocytes consistently recruiting from one growth phase to the next to form the sequential batches. In this study, we examined in detail the oocyte recruitment and development pattern of the sequential batches in a commercially important fish with indeterminate fecundity, the European sardine. The numbers and sizes of oocytes at different developmental stages were estimated for four phases of the ovulatory cycle (ovarian stages) and during the main spawning season (November–March) by applying the oocyte packing density theory in combination with stereological techniques. General linear models (GLMs) were used to test for changes in oocyte sizes as well as relative oocyte numbers per developmental stage within the different ovarian stages in the successive spawning months. A temporal association between several transition events of the oocyte development process was revealed. Specifically, the final maturation of the advanced batch triggered (a) the recruitment of oocytes from primary to secondary growth phase, (b) de novo vitellogenesis and (c) a surge of yolk deposition in primary vitellogenic oocytes. Oocyte recruitment was completed two days after the ovulation of the advanced batch and relative numbers of primary and secondary growth oocytes were thereafter stable until the next final maturation event. This pattern of oocyte recruitment and growth remained unchanged during the course of the spawning season. This study advances our knowledge on oocyte recruitment and development in fish with indeterminate fecundity, which is key to understanding reproduction and its drivers at the individual and population level. [ABSTRACT FROM AUTHOR]

Benzophenone-3 (BP3), an organic UV filter widely used in personal care products, is ubiquitous in aquatic environments. Previous studies have shown that BP3 can interfere with oocytes development in the ovary. The current study was conducted to evaluate the effects of embryonic BP3 exposure on reproductive outcomes in later life. Zebrafish embryos were exposed to different concentrations of BP3 (0, 1, 10, 100 μg/L) for 5 days in the developmental stage and subsequently fed for 4 months without any toxins. The body length, body weight, and ovary weight in F0 female adult zebrafish and morphology indices in F1 offspring embryos were measured. The reproductive behaviors of adult zebrafish were recorded by a digital camera. HE staining was used to estimate the development of oocytes and the proportion of different phases was calculated. qPCR was used to detect the expression levels of reproduction-related genes of the hypothalamic-pituitary-gonadal (HPG) axis. Our findings revealed that the body length and body weight were not changed with embryonic BP3 exposure, but BP3 exposure inhibited the development and maturation of ovaries in later-life female zebrafish, accompanied by an increased proportion of follicles in the primary growth and early vitellogenic stages, and a decline in the full-growth stage in ovaries. Meanwhile, reduced egg production, delayed hatching rate, altered somite count and increased mortality rate were observed at 100 μg/L in offspring embryos. Behavioral results showed that BP3 exposure reduced the frequency of chasing, touching, entering the spawning area, and the duration of fish entering the spawning area later in life, qPCR analysis showed that the expression levels of reproduction-related genes of the HPG axis were downregulated in females, following a decreasing trend in plasma E2 and 11-KT levels. These results suggested that embryonic BP3 exposure negatively affected the fertility of fish and the development of their offspring embryos, which may cause potential risks to aquatic ecosystems and human health. [ABSTRACT FROM AUTHOR]

The biology of fish sperm, an important topic in the research of reproduction and fisheries from basic science to evolutionary and applied aspects, has implications for aquaculture management, fish breeding and biological conservation. The quality of spermatozoa plays a vital role in fish fertility, and directly affects the health and performance of offspring. Environmental factors that affect determinants of spermatozoa quality usually reflected in the DNA methylation pattern of the spermatozoa epigenome, which may change offspring's performance. The aim of the present study was to conduct a review on existing data about DNA methylation in fish spermatozoa as a biological tool for identifying the quality of offspring based on their phenotypes and performances. Furthermore, this study provides valuable knowledge from fundamental to applied sciences dealing with enhancement of breeding selection, fish reproduction and environmental adaptation. The review also describes the individual parts related to DNA methylation in fish, including overview of the methods which can be used to study DNA methylation, DNA methylation dynamics and epigenetic inheritance; identification of DNA methylation changes in sperm function in response to internal and external environment constraints, and potential relationships between DNA methylation and physiological regulation of spermatozoa quality determinants. Overall, the present study revealed that our knowledge about intergenerational inheritance of the performance and adaptability of fish through sperm DNA methylation is very limited, and no general conclusion could be approached from literature mostly due to non‐standardized experimental protocol or analytical tools. [ABSTRACT FROM AUTHOR]

Steroid 5α-reductase (SRD5A) is a crucial enzyme involved in steroid metabolism, primarily converting testosterone to dihydrotestosterone (DHT). Dutasteride, an inhibitor of SRD5A types 1 and 2, is widely used for treating benign prostatic hyperplasia. An adverse outcome pathway (AOP) has been documented wherein SRD5A inhibition decreases DHT synthesis, leading to reduced levels of 17β-estradiol (E2) and vitellogenin (VTG), subsequently impairing fecundity in fish (AOP 289). However, the molecular and cellular mechanisms underlying these effects remain poorly understood. In this study, we assessed the impact of SRD5A inhibition on zebrafish embryos (Danio rerio). Exposure to dutasteride resulted in decreased DHT, E2, and VTG levels, showing a positive correlation. Dutasteride also downregulated the expression of reproduction-related genes (srd5a2, cyp19a1, esr1, esr2a, esr2b, and vtg), with interrelated reductions observed across these levels. Docking studies suggested that dutasteride's effects may operate independently of androgen receptor (AR) and estrogen receptor (ER) interactions. Furthermore, co-exposure of dutasteride (0.5 or 2 μM) with 0.5 μM DHT revealed gene expression levels comparable to the control group. These findings underscore DHT's pivotal role in modulating estrogenic function and the interplay between estrogenic and androgenic responses in vertebrates. Our proposed AOP model offers insights into mechanistic gaps, thereby enhancing current understanding and bridging knowledge disparities. [Display omitted] • Dutasteride exposure down-regulated reproductive biomarkers in zebrafish embryos. • Dutasteride exposure did not directly impact estrogen or androgen receptor reporter. • Effects of dutasteride were recovered by co-treatment with DHT. • DHT levels play a pivotal role in the zebrafish reproductive system. • Mechanisms of SRD5A inhibition clarifies gaps in AOP understanding. [ABSTRACT FROM AUTHOR]

An investigation on the feeding and breeding in Bagarius bagarius was examined from Manchar Lake District Jamshoro, Sindh, Pakistan. Total 62 samples were accessed at different length groups during April-September 2022. The range of samples was between (10.0 to 70.0 cm) and from (28-3500 g) in total length and weight respectively. For food determination the experimental fish was divided into three length groups viz., small (10.0-15.0 cm) medium (15.1-30.0 cm) and large (40.0-70.0cm) for the determination of feed preference. The results of the investigations revealed that the food fondness of B. bagarius was detected as highly carnivorous (Piscivorous) displayed higher preferences for fish (46.6 %) seconded by insect larvae (20 %) and 3rd preferred was debris (15.4 %). For breeding analysis values of ova diameter were found to be ranged between 0.55-1.0 mm, the gonadosomatic index (GSI) values were also from to be increasing from 0.71-6.5% and from 0.82-10.28% for both the sexes. These values remained high du ring April to August. It indicated that the fish spawned once in a year in July. Outcomes of egg estimation during the examination depended on 10 matured B. bagarius from Manchar Lake. Fecundity ranged between 260-554 eggs. Least egg estimation 260 was detected from fish of 41.8cm and 88.0 g in length and weight. The highest egg was 554 from 59.0 cm and 155 g in both length and weight. Total body length exhibits better relationship with fecundity of experimental fish B. bagarius from Manchar Lake than the other parameters. [ABSTRACT FROM AUTHOR]

• 83 % of fishery in the Lancang River is attributed to farm-raised fishery. • Overfishing, damming, and hydrological alterations threaten fishery and agriculture. • Lower Mekong's agriculture surged in last decade, poised for a 65 % rise by the 2060s. • Call for basin-wide studies involving all riparian countries. Fisheries and agriculture – the pillars of food security in the Lancang Mekong River Basin (LMRB) – substantially contribute to the welfare of communities in the region through international trade and local daily food sources. These sectors, however, are vulnerable to climate change as well as changes caused by the recent rising demands for food and clean energy (e.g., hydropower reservoirs). The impacts of hydropower reservoirs on the fertility of lands and fish stocks hold significant implications for the region's sustainable development. This study investigates the underlying factors driving these sectors' current conditions and critically reviews existing approaches for the basin's food security, which have been neglected by previous studies. Indiscriminate fishing, damming, and hydrological alterations are identified as key contributors to the ongoing challenges, with varying regional priorities. Findings reveal that 83 % of fishery in the Lancang Basin is attributed to farm-raised fishery. Despite significant river fragmentation stemming from cascade dams and extensive small-scale barriers in China, there has been a significant increase (∼606 %) in Lancang mainstream fishery over the past two decades. Additionally, 54 % of riverine fish species in the lower Mekong have lost connectivity due to existing dam infrastructure. Agriculture appears to remain consistent in the Lancang Basin, while the lower Mekong experienced a significant increase in agricultural lands- a trend that is projected to rise by 65 % by the 2060s. Two primary drawbacks were identified: firstly, the use of daily data (e.g., water level and discharge) that cannot fully capture the dammed LMR dynamic flow regime; and secondly, the ignorance of telecoupling to the sub-basins, neglecting the connections either among sub-basins within the basin or extending outside of it. This paper thus advocates for a unified basin-wide study engaging all riparian countries through a transboundary water cooperation mechanism. Failure to act swiftly could result in irreversible changes to the basin in the coming decades as population growth, urbanization, and human pressures accelerate. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Objective: This study describes the newest deoxyribonucleic acid (DNA) barcoding Asian redtail catfish (Hemibagrus nemurus) in the Progo River, Magelang, Central Java, Indonesia. Materials and Methods: Ten fish were caught in the Progo River, Magelang, Central Java, Indonesia. The polymerase chain reaction was the molecular diagnosis to detect the sequences of DNA of Cytochrome Oxidase I compared to National Center for Biotechnology Information data (GenBank). Results: The results showed that the percent identity was not 100% with H. nemurus data from other locations (GenBank), including Indonesia. The closest percent identity was H. nemurus from Java Island (Accession ID: MK312566.1) with 97.6% similarity. The genetic mutation that happened might be due to environmental change (pollution) in the Progo River recently. Conclusions: This study showed a genetic mutation in H. nemurus from Progo River may be caused by environmental change. Low pollution exposure levels may not be detrimental (lethal) to fish. However, it can affect fish fertility, which leads to population degradation (gene variation). Attention must be increased for fish survival in the future. [ABSTRACT FROM AUTHOR]

Background: Steroid hormones play an essential role in many reproductive processes of vertebrates. Previous studies revealed that teleost-specific Cyp17a2 (cytochrome P450 family 17 subfamily a 2) might be required for the production of cortisol in the head-kidney and 17a,20b-dihydroxy-4-pregnen-3-one (DHP) in ovary during oocyte maturation. However, the role of Cyp17a2 in male reproduction remains to be largely unknown. The aim of this study was to explore the essentiality of cyp17a2 gene in male steroidogenesis, spermatogenesis, and male fertility. Methods: A homozygous mutation line of cyp17a2 gene was constructed in tilapia by CRISPR/Cas9 gene editing technology. The expression level of germ cell and meiosis-related genes and steroidogenic enzymes were detected by qRT-PCR, IHC, and Western blotting. EIA and LC-MS/MS assays were used to measure the steroid production levels. And sperm quality was examined by Sperm Quality Analyzer software. Results: In this study, cyp17a2 gene mutation resulted in the significant decline of serum DHP and cortisol levels. On the contrary, significant increases in intermediate products of cortisol and DHP were found in cyp17a2-/- male fish. The deficiency of cyp17a2 led to the arrest of meiotic initiation in male fish revealing as the reduction of the expression of germ cell-related genes (vasa, piwil, oct4) and meiosis-related genes (spo11 and sycp3) by 90 dah. Afterwards, spermatogenesis was gradually recovered with the development of testis in cyp17a2-/- males, but it showed a lower sperm motility and reduced fertility compared to cyp17a2+/+ XY fish. Deletion of cyp17a2 led to the abnormal upregulation of steroidogenic enzymes for cortisol production in the headkidney. Moreover, unaltered serum androgens and estrogens, as well as unchanged related steroidogenic enzymes were found in the testis of cyp17a2-/- male fish. Conclusion: This study proved that, for the fist time, Cyp17a2 is indispensable for cortisol and DHP production, and cyp17a2 deficiency associated curtailed meiotic initiation and subfertility suggesting the essentiality of DHP and cortisol in the male fertility of fish. [ABSTRACT FROM AUTHOR]

In mice, CD9 expression on the egg is required for efficient sperm-egg fusion and no effects on ovulation or male fertility are observed in CD9 null animals. Here we show that cd9b knockout zebrafish also appear to have fertility defects. In contrast to mice, fewer eggs were laid by cd9b knockout zebrafish pairs and, of the eggs laid, a lower percentage were fertilised. These effects could not be linked to primordial germ cell numbers or migration as these were not altered in the cd9b mutants. The decrease in egg numbers could be rescued by exchanging either cd9b knockout partner, male or female, for a wildtype partner. However, the fertilisation defect was only rescued by crossing a cd9b knockout female with a wildtype male. To exclude effects of mating behaviour we analysed clutch size and fertilisation using in vitro fertilisation techniques. Number of eggs and fertilisation rates were significantly reduced in the cd9b mutants suggesting the fertility defects are not solely due to courtship behaviours. Our results indicate that CD9 plays a more complex role in fish fertility than in mammals, with effects in both males and females. [ABSTRACT FROM AUTHOR]

Aspects of the reproductive biology of Atlantic chub mackerel Scomber colias are reported here based on data from random samples of artisanal fish landings from Ghana. The specimens were between 13.7 cm and 40.7 cm total length (TL), and both sexes matured at a mean length (Lm50) of approximately 25 cm TL. An overall sex ratio of 1:1 was estimated for the population. Absolute fecundity of the fish ranged between 10 220 and 155 791 eggs (mean 48 238 [SE 2 324] eggs) in individuals measuring between 22.8 and 36.5 cm TL and weighing 104.3 to 525.3 g. Monthly variations in the gonadosomatic index and the proportion of fish with ripe gonads in the samples indicated the occurrence of spawning activities during two periods, March–April and June–August, the latter period of which coincided with the coastal upwelling season in Ghanaian waters. These findings are compared with those for chub mackerel from the northwestern and southwestern coasts of Africa. The results of this study will help inform the management of this small pelagic species in Ghana. [ABSTRACT FROM AUTHOR]

Background: Parastromateus niger, is one of the important fish species from economic point of view in Gwadar, Balochistan-Pakistan. This study was carried out to determine the growth and fecundity of Parastromateus niger. Methods: Growth of P. niger was determined by applying Le Cren formula while mean fecundity and relative fecundity of this fish was calculated by using equation of Yelden and Avsar. Result: Relationship between fish weight and ovary weight was found as 0.384 and 0.898 respectively in 1st and 2nd year of research. Annual mean fecundity of P. niger was calculated as 43165.4 eggs with relative fecundity of 73.7 in 2017-18 and annual mean fecundity in 2018-19 was 39759.5 eggs with 50.2 relative fecundity. Value of R2 in first year of research between fecundity and ovary weight was 0.751, for mean fecundity and relative fecundity was 0.545, in term of fecundity and total length of fish was 0.60 and for fish total weight and fecundity was 0.596. Value of R2 between fecundity and weight of ovary was 0.951, with mean fecundity and relative fecundity as 0.968, between fish fecundity and total length was 0.578 and in case of fecundity and total body weight was found 0.809 in second year of research period. [ABSTRACT FROM AUTHOR]

This present study provides an overview of the reproductive traits, including ovarian development, spawning season, size at maturity (Lm), and fecundity of Acentrogobius viridipunctatus - a high economic value fish in the Vietnamese Mekong Delta (VMD). A total of 432 females were collected using trawl nets from January to December 2020 at four sites, including Long Huu-Tra Vinh (LHTV), Trung Binh-Soc Trang (TBST), Dien Hai-Bac Lieu (DHBL), and Tan Thuan-Ca Mau (TTCM). The ovarian diameter was seen to increase from 2.09 (stage I) to 6.57 mm (stage V). Histological analysis showed that the goby was a multi-spawner due to the different oocyte stages found in stages IV and V of ovaries. It can release eggs all year-round due to the monthly appearance of ovarian stages IV and V during the study period, with the main peak in the 2-4 months of the wet season noted with the highest value of gonadosomatic index at that time. The Lm increased from 6.6 cm at TBST to 9.4 cm at TTCM. This species displayed relatively high fecundity, ranging from 5,481 to 130,683 eggs/female. The average fecundity of this fish was 27,698 ± 7,983 eggs/female at LHTV, 46,592 ± 7,264 eggs/female at TBST, 23,271 ± 4,985 eggs/female at DHBL, and 31,408 ± 2,515 eggs/female at TTCM. Egg diameter ranged from 0.45 ± 0.01 at DHBL to 0.50 ± 0.01 at TBST. For sustainable exploitation, local governments should ask the fishers to avoid catching fish during the main spawning period, and the fish length at first capture should be >Lm. [ABSTRACT FROM AUTHOR]

Steroidogenic acute regulatory protein (Star) plays an essential role in the biosynthesis of corticosteroids and sex steroids by mediating the transport of cholesterol from the outer to the inner membrane of mitochondria. Two duplicated Star genes, namely star1 and star2 , have been identified in non-mammalian vertebrates. To investigate the roles of star genes in fish steriodogenesis, we generated two mutation lines of star1 −/− and star1 −/− /star2 −/− in Nile tilapia (Oreochromis niloticus). Previous studies revealed that deficiency of star2 gene caused delayed spermatogenesis, sperm apoptosis and sterility in male tilapia. Our present data revealed that mutation of star genes impaired male fertility. Disordered seminiferous lobules and spermatic duct obstruction were found in the testis of both types of mutants. Moreover, significant decline in semen volume, sperm abnormality and impaired fertility were also detected in star1 −/− and star1 −/− /star2 −/− males. In star1 −/− male fish, lipid accumulation, up-regulation of steroidogenic enzymes, and significant decline of androgens were found. Additionally, hyperplasic interrenal cells, elevated steroidogenic gene expression level and decline of serum glucocorticoids were detected in star1 mutants. Intriguingly, either 11-KT or cortisol supplementation successfully rescued the impaired fertility of the star1 −/− mutants. Taken together, these results further indicate that Star1 might play critical roles in the production of both 11-KT and glucocorticoids, which are indispensable for the maintenance of male fertility in fish. [Display omitted] • Star1 plays critical roles in androgen and glucocorticoids synthesis in tilapia. • Star1 and star1 / star2 gene mutation impaired male fertility in tilapia. • 11-keto-testosterone and cortisol can restore male fertility in star1 mutant tilapia. [ABSTRACT FROM AUTHOR]

• The RNA-seq results revealed the overall changes of genes related to circadian rhythm and disease-linked signaling pathways. • The deficiency of Rln3a resulted in up-regulation of GnRH1 and kisspeptin 2 in the brain. • Mutation of Rln3a led to the alteration serum dopamine level and its synthase in hypothalamus. Relaxin3 (rln3) has been associated with various emotional and cognitive processes, including stress, anxiety, learning, memory, motivational behavior, and circadian rhythm. Notably, previous report revealed that Rln3a played an indispensable role in testicular development and male fertility in Nile tilapia (Oreochromis niloticus). However, the underlying molecular mechanisms remain largely unknown. We found that Rln3a is expressed exclusively in the diencephalon* (Di*) of the brain. Deficiency of Rln3a resulted in a significant increase in serum dopamine level and an upregulation of gene expression of gnrh1 and kisspeptin2. To further elucidate the role of Rln3a in fish fertility, we collected two different regions of Di* and hypothalamus (Hyp) tissues for subsequent RNA-seq analysis of both wild-type (rln3a +/+) and rln3a -/- male tilapia. Upon the transcriptomic data, 1136 and 755 differentially expressed genes (DEGs) were identified in the Di* and Hyp tissues, respectively. In Di*, the up-regulated genes were enriched in circadian rhythm, chemical carcinogenesis, while the down-regulated genes were enriched in type II diabetes mellitus, dopaminergic synapse, and other pathways. In Hyp, the up-regulated genes were enriched in circadian rhythm, pyrimidine metabolism, while the down-regulated genes were enriched in type I diabetes mellitus, autoimmune thyroid disease, and other pathways. Subsequently, the results of both qRT-PCR and FISH assays highlighted a pronounced up-regulation of core circadian rhythm genes, cry1b and per3 , whereas genes such as clocka , clockb , and arntl exhibited down-regulation. Furthermore, the genes associated with dopamine biosynthesis were significantly increased in the Hyp. In summary, the mutation of rln3a in male tilapia resulted in notable changes in circadian rhythm and disease-linked signaling pathways in the Di* and Hyp. These changes might account for the fertility defects observed in rln3a -/- male mutants in tilapia. [ABSTRACT FROM AUTHOR]

This study aims to understand the reproductive biology of Thynnichthys thynnoides at Rui River, Perak, Malaysia. A total sample of 175 individuals, including 83 from Kuala Rui (S1) and 92 from Air Ganda (S2), were collected from local artisanal fishers. Fish was caught using gill nets and scoop nets during migration and spawning seasons (i.e., November to December 2018). For each fish individual, the total length (TL), body weight (BW), and ovary weight (OW) were and. A Chi-square test was performed to evaluate the sex ratio of the studied population. Simple linear regression analysis was used to explain the relationship between absolute fecundity (FA) or relative fecundity (FR) with total length, body weight, and ovary weight. For a coefficient of determination (r²) and correlation coefficient (r), a regression equation was determined. The results showed that the TL of T. thynnoides varied from 13.3 to 20.3 cm, with a calculated mean of 16.78 ± 1.1 cm. Body weights ranged from 31.86 to 78.86 g, with an average body weight of 53.81 ± 10.1 g. The FA ranged from 14454 to 29531 (mean = 21112 ± 4612) eggs per fish, and the FR from this study ranged from 211 to 658 (mean = 358 ± 93), where the OW was more significantly correlated with the absolute fecundity (r>0.513; p<0.001) than other body metrics. Negative allometric growth of T. thynnoides was observed during this study. The overall ratio of the T. thynnoides was 1:0.82 (male: female). In conclusion, this study has shown that the fecundity of the fish population is declining, although the cause is still unclear. The knowledge of this study would help fisheries managers plan necessary regulations for sustainable fishery practice at the Rui and Perak rivers, specifically during the migration and spawning season of T. thynnoides. [ABSTRACT FROM AUTHOR]

The link between the dynamic organization of the ovary and spawning dynamics was investigated in pelagic fishes with indeterminate fecundity. Αn array of laboratory methods and statistical approaches was applied to samples of gonadal material from three commercial NE Atlantic fish species: the sardine, Sardina pilchardus, the horse mackerel, Trachurus trachurus, and the mackerel, Scomber scombrus. Methods included the application of clustering analysis algorithms in histological specimens and the application of particle analysis on whole mounts. More specifically, various attributes of ovarian dynamics such as the oocyte size frequency distribution, the ratio of total to batch fecundity, the number of oocyte cohorts, and the recruitment of early secondary growth oocytes were related to historic estimates of spawning interval and oocyte growth rate. It was shown that indeterminate spawners can display varying proportions of oocytes at the size range between primary and secondary growth based on the seasonal pattern of oocyte recruitment. This finding indicates that determinacy and indeterminacy should rather be recognized as end-points along a continuum which is controlled by the degree of overlap between oocyte recruitment period and spawning period. It was also demonstrated that fishes like sardine with long spawning intervals and fast oocyte growth exhibit relatively few, clearly separated oocyte cohorts, while fishes like mackerel with shorter spawning interval display increased number of coexisting cohorts. Ultimately, these aspects may provide a proxy of spawning interval and thereby spawning frequency which is a variable of paramount importance in biomass assessments of commercial fish stocks through egg production methods. [ABSTRACT FROM AUTHOR]

Populations of Periophthalmus chrysospilos, the Gold‐spotted mudskipper, within the Mekong Delta are facing extirpation risks due to indiscriminate harvesting for the growing aquarium and food‐fish trade. This study provides some of the first information on reproductive ecology—such as spawning type and season, length at first maturity, and batch fecundity—of this species, to be used in their management. The sex ratio of wild populations, based on 1031 individuals (523 males and 508 females) is 1:1. The gonadosomatic index (GSI) values are exhibit a non‐normal distribution and changed with gender, season, and site. A combination of GSIs and the monthly appearance of mature gonads suggest that this species reproduces throughout the year, with peak from July to October. This species exhibits sexual and spatial variation in size at first maturity (Lm) as Lm is 6.2–8.6 cm in males and 6.4–7.3 cm in females. The batch fecundity (F = 2614 to 23,465 eggs/female) exhibits non‐normal distribution and varies with site, with the highest values at Dam Doi, Ca Mau (13,336 ± 1,279 SE) and the lowest at Tran De, Soc Trang (6654 ± 851 SE). In addition, batch fecundity is directly proportional to body size due to high determination relationships between batch fecundity and fish size (r2 > 0.64 for all cases). Information derived on the reproductive biology of this species can inform its conservation, sustainable exploitation, and ex situ propagation. [ABSTRACT FROM AUTHOR]

Chromosomal ploidy manipulation is one of the means to create excellent germplasm. Triploid fish could provide an ideal sterile model for searching of a underlying mechanism of abnormality in meiosis. The complete understanding of the coding and noncoding RNAs regulating sterility caused by meiosis abnormality is still not well understood. By high-throughput sequencing, we compared the expression profiles of gonadal mRNA, long non-coding RNA (lncRNA), and microRNA (miRNA) at three different developmental stages between the diploid (XX) and triploid (XXX) female rainbow trout. These stages were gonads before differentiation (65 days post fertilisation, dpf), at the beginning of morphological differences (180 dpf) and showing clear difference between diploids and triploids (600 dpf), respectively. A majority of differentially expressed (DE) RNAs were identified, and 22 DE mRNAs related to oocyte meiosis and homologous recombination were characterized. The predicted miRNA-mRNA/lncRNA networks of 3 developmental stages were constructed based on the target pairs of DE lncRNA-miRNA and DE mRNA-miRNA. According to the networks, meiosis-related gene of ccne1 was targeted by dre-miR-15a-5p_R + 1, and 6 targeted DE lncRNAs were identified. Also, qRT-PCR was performed to validate the credibility of the network. Overall, this study explored the potential interplay between coding and noncoding RNAs during the gonadal development of polyploid fish. The mRNA, lncRNA and miRNA screened in this study may be helpful to identify the functional elements regulating fertility of rainbow trout, which may provide reference for character improvement in aquaculture. • miRNA-mRNA/lncRNA interaction networks of gonadal development in triploid fishes. • 22 genes were related to oocyte meiosis and homologous recombination. • 6 lncRNAs regulate meiosis as the target of miR-15a-5p. • Polyploidy-associated effects on fertility of fish. [ABSTRACT FROM AUTHOR]

Fishes are characterized by a great diversity of reproductive strategies that often make fecundity evaluation difficult. Unlike marine fishes, a single consensual concept of terminology and definitions is lacking for freshwater fish fecundity. Several approaches are known from scientific literature for evaluating fecundity in batch spawning fishes of indeterminate fecundity and asynchronous oocyte maturation. These methodological differences impose a bias on the outputs of comparative studies of fecundity. For both theoretical and practical reasons, accurate fecundity data are required to inform the decision-making process in terms of environmental policy and the related applications for the control of non-native species and the conservation management of native species and ecosystems. The main aim of the present study was to review briefly the existing fecundity-evaluation methods, to test among-method compatibility, and to develop a new approach that aims to make fecundity evaluation more systematic and transparent. A simulated 'test' dataset demonstrated considerable variability in the results obtained from the various existing approaches. The literature review and our analyses revealed a need for standardization. Thus, a new approach is proposed here that is based on multiple sampling throughout the reproductive cycle; provides greater overall detail of the species' reproductive traits and permits inter-population comparisons. [ABSTRACT FROM AUTHOR]

Atresia of ovarian follicles, that is the degenerative process of germ cells and their associated somatic cells, is a complex process involving apoptosis, autophagy and heterophagy. Follicular atresia is a normal component of fish oogenesis and it is observed throughout the ovarian cycle, although it is more frequent in regressing ovaries during the postspawning period. An increased occurrence of follicular atresia above physiological rates reduces fish fecundity and even causes reproductive failure in both wild and captive‐reared fish stocks, and hence, this phenomenon has a wide range of implications in applied sciences such as fisheries and aquaculture. The present article reviews the available literature on both basic and applied traits of oocyte loss by atresia, including its morpho‐physiological aspects and factors that cause a supraphysiological increase of follicular atresia. Finally, the review presents the use of early follicular atresia identification in the selection process of induced spawning in aquaculture and the implications of follicular atresia in fisheries management. [ABSTRACT FROM AUTHOR]

Freshwater fish farming is the largest sub‐sector of the global aquaculture industry, with its continued success dependent on the industry's ability to be productive and sustainable. In recent years, microorganisms have been increasingly recognised for their role in the health and overall performance of aquatic organisms, providing the aquaculture industry with a promising avenue for further success. Here, we review the literature on freshwater fish microbiology to evaluate the potential for microbial research to enhance freshwater aquaculture. A systematic review revealed that the existing freshwater fish microbiology literature incorporates <1% of freshwater fish species, with most studies focussed on Cyprinidae, Salmonidae and to a lesser extent Cichlidae. Using social network analyses, this review identified 25 key research areas commonly addressed in the existing literature highlighting the narrow focus of existing studies. Microbial community structure was the most frequently researched area, followed by environment and diet. These studies often evaluated microbiota changes associated with diadromous migrations, new technologies and advancements in feed formulations. However, research areas, such as the role of microorganisms in fish fecundity, omega‐3 content, sustainability and palatability, were underrepresented in the literature despite their influence on aquaculture success. These underrepresented research areas are examples of where additional investments in microbial research are needed to ensure the continued expansion and success of freshwater aquaculture. [ABSTRACT FROM AUTHOR]

Over the last decade, the African turquoise killifish, Nothobranchius furzeri, has emerged as an important model system for the study of vertebrate biology and ageing. Propagation of laboratory inbred strains of Nothobranchius furzeri, such as GRZ, however, can pose challenges due to the short window of fertility, the efforts and space requirements involved in continuous strain maintenance, and the risks of further inbreeding. The current method for long term strain preservation relies on arrest of embryos in diapause. To create an alternative for long term maintenance, we developed a robust protocol to cryopreserve and revive sperm for in vitro fertilization (IVF). We tested a variety of extender and activator buffers for sperm IVF, as well as cryoprotectants to achieve practical long-term storage and fertilization conditions tailored to this species. Our protocol enabled sperm to be preserved in a cryogenic condition for months and to be revived with an average of 40% viability upon thawing. Thawed sperm were able to fertilize nearly the same number of eggs as natural fertilization, with an average of ~ 25% and peaks of ~ 55% fertilization. This technical advance will greatly facilitate the use of N. furzeri as a model organism. [ABSTRACT FROM AUTHOR]

Relaxin 3 is a neuropeptide that plays a crucial role in reproductive functions of mammals. Previous studies have confirmed that rln3a plays an important role in the male reproduction of tilapia. To further understand the significance of its paralogous gene rln3b in male fertility, we generated a homozygous mutant line of rln3b in Nile tilapia. Our findings indicated that rln3b mutation delayed spermatogenesis and led to abnormal testes structure. Knocking out rln3b gene resulted in a decrease in sperm count, sperm motility and male fish fertility. TUNEL detection revealed a small amount of apoptosis in the testes of rln3b −/− male fish at 390 days after hatching (dah). RT-qPCR analysis demonstrated that mutation of rln3b gene caused a significant downregulation of steroid synthesis-related genes such as cyp17a1 , cyp11b2 , germ cell marker gene, Vasa , and gonadal somatic cell marker genes of amh and amhr2. Furthermore, we found a significant down-regulation of hypothalamic-pituitary-gonadal (HPG) axis-related genes, while a significantly up-regulation of the dopamine synthetase gene in the rln3b −/− male fish. Taken together, our data strongly suggested that Rln3b played a crucial role in the fertility of XY tilapia by regulating HPG axis genes. • The establishment of a homozygous mutant line of the rln3b gene in bony fish • Rln3b regulated testicular development and fertility in male fish. • Rln3b played a crucial role as an upstream regulatory factor in the HPG reproductive regulatory network. • Rln3b modulated the production of steroid synthesis and the expression of dopamine synthesis-related genes. [ABSTRACT FROM AUTHOR]

Capoeta aculeata (Valenciennes, 1844) is native to Iran and little is known about its biology. Some biological characteristics of this species were examined in 120 male and 257 female specimens collected monthly from the Gizehrud River of Lorestan Province (Tigris basin, Iran) during July 2014-June 2015. The maximum age of the specimens, based on scale reading, was 6+ years for both males and females. The most frequent age group was 4+ in both sexes. Fork length ranged from 12.2 to 20.8 cm (17.4±1.2SD) and weight ranged between 32-188 g (93.6±21.8SD). Sex ratio was 1M:2.1F. Based on macroscopic gonad observation, maturation cycle consisted of four stages: Developing, spawning, regressing and regeneration phases. The GSI index indicated that reproduction of C. aculeata in Gizehrud occurred between April and May, with the highest value average of 6.37 for males and 11.91 for females in May. Oocyte diameters ranged from 0.57 to 1.88 mm, with a mean value of 0.87 mm. Absolute fecundity ranged between 3000 and 19500 (8300±3400) eggs. Absolute fecundity and fish size (fork length and total weight) were moderately correlated. Relative fecundity varied from 50 to 140 (80±20) eggs per gram of total body weight. This fish is a synchronous spawner. [ABSTRACT FROM AUTHOR]

The ovarian development, spawning pattern and season, size at first maturity and fecundity of Glossogobius sparsipapillus, which is an essential commercial fish in the Mekong Delta, have been studied. Totally, 317 fish were collected from the estuarine and the coastal regions including Vinh Hau, Hoa Binh to Dien Hai, Dong Hai (Bac Lieu Province) and Tan Thuan, Dam Doi (Ca Mau Province). Fishes were sampled using gill nets during the dry and wet seasons in April 2019 - January 2020. The results show that the ovaries have different types of oocytes and that this goby was a multiple spawner. It spawned from July to September at three of the studied sites, since most of the mature ovaries appeared at that time. The size at first maturity (Lm) was from 6.50 cm in Vinh Hau and Tan Thuan to 6.78 cm in Dien Hai. The average batch fecundity was 24,966±2,542 eggs, ranging from 17,918±2,258 SE in Vinh Hau to 28,700±5,322 SE in Dien Hai, followed closely by Tan Thuan (26,352±3,458 SE). There was an increase in batch fecundity with fish size. The fish total length and weight had strong positive relationships with batch fecundity. The egg size was 48.20±4.89 SE µm length and 26.39±3.09 SE µm width. [ABSTRACT FROM AUTHOR]

Non-lethal methods for semen collection from elasmobranchs to better understand species reproduction has accompanied the development of artificial insemination. Ejaculates (n = 82) collected from whitespotted bamboo sharks Chiloscyllium plagiosum (n = 19) were assessed and cold-stored raw or extended at 4 °C. Females (n = 20) were inseminated with fresh or 24–48 h cold-stored raw or extended semen and paternity of offspring determined with microsatellite markers. Insemination of females with fresh semen (n = 10) resulted in 80 hatchlings and 27.6% fertility. Insemination of females with semen cold-stored 24 h (n = 4) and 48 h (n = 1) semen resulted in 17 hatchlings and fertilization rates of 28.1% and 7.1% respectively. Two females inseminated with fresh or cold-stored semen laid eggs that hatched from fertilization and parthenogenesis within the same clutch. Parthenogenesis rate for inseminated females was 0.71%. Results demonstrate artificial insemination with cold-stored semen can provide a strategy for transport of male genetics nationally and internationally, precluding the need to transport sharks. Production of parthenotes in the same clutch as sexually fertilized eggs highlights the prevalence of parthenogenesis in whitespotted bamboo sharks and poses important considerations for population management. [ABSTRACT FROM AUTHOR]

The development of semen cryopreservation strategies is necessary to improve the semen storage technologies of species of great commercial interest for aquaculture. Recent studies demonstrate that lipids play an important role in the fertility and cryotolerance of fish gametes. This study investigated the effect of exogenous lipids in the freezing medium on the post-thaw functional parameters of Salmo salar spermatozoa. Semen samples (n = 12) were incubated in standard extender supplemented with different concentrations of oleic acid (OA, C18:1n9), linoleic acid (LA, C18:2n6), arachidonic acid (ARA, C20:4n6) and cholesterol-loaded cyclodextrin (CLC). Post-thaw motility, membrane integrity, mitochondrial membrane potential (ΔΨm), superoxide anion (O 2 •-) and fertility rates were analyzed. The results revealed that the semen incubated with 0.003 mmol/L OA increased the motility (~7%) and ΔΨm (~2%) (P < 0.05), but membrane integrity and fertility were not increased. The addition of 0.003 mmol/L LA increased the motility (~4%) and all LA extenders increased the ΔΨm (P < 0.05); however, LA increased the O 2 •- levels and decreased the membrane integrity and fertility (P < 0.05). Semen incubated with ARA improved sperm motility (~5%), membrane integrity (~10.5%) and fertility rates (~11%) (P < 0.05). The maximum improvement in post-thaw sperm functionality was observed by adding 0.003 mmol/L ARA. In contrast, sperm quality parameters and fertility were decreased by the CLC addition (P < 0.05). This study showed that ARA could be considered as an additive for semen cryopreservation and could be relevant in the reproductive process and reproductive management of Salmo salar. • Fatty acids modulate the functionality and cryoresistance of S. salar spermatozoa. • Oleic acid and linoleic acid increase the mitochondrial membrane potential and motility of S. salar spermatozoa. • Linoleic acid induces an increase of O 2.•- production in S. salar spermatozoa • Arachidonic acid enhancement post-thaw motility, membrane integrity and fertility of S. salar spermatozoa. • Cholesterol addition has a negative impact on S. salar sperm cryopreservation. [ABSTRACT FROM AUTHOR]

Clarias gariepinus juveniles were exposed to environmentally relevant concentrations of 0 (control), 2.5, 25, 250 and 500 μg L−1 atrazine in a quality-controlled 28-day laboratory procedure. Findings revealed a significant decrease in the levels of follicle-stimulating hormone, luteinizing hormone and prolactin relative to control (p < 0.05). Atrazine reduced the levels of testosterone while increasing the concentration of progesterone. Histologically, the control and treatments presented three stages of oocyte maturation: the chromatin nucleolar oocyte stage, early perinucleolar oocyte stage and the vitellogenic oocyte stage. However, in the ovaries of the treatment group with the lowest treatment concentration (2.5 μg L−1), atretic oocytes with broken membranes invaded many of the dead ova and empty spaces. In other treatments (25, 250 and 500 μg L−1), interfollicular spaces, vacuolation in oocyte formation, and dissolution of oocyte walls were observed. Disruption of the yolk vesicle and clumping of the cytoplasm in maturing oocytes was observed only at the highest atrazine concentration (500 μg L−1). Gross alterations in ovarian histoarchitecture and reproductive hormone levels observed in this study showed interference with oogenesis which may result in reduced egg viability and fecundity in fish with ecological implications in water bodies exposed to atrazine even at reduced concentrations. [ABSTRACT FROM AUTHOR]

Evolutionary theory predicts that infection by a parasite that reduces future host survival or fecundity should select for increased investment in current reproduction. In this study, we use the cestode Ligula intestinalis and its intermediate fish host Engraulicypris sardella in Wissman Bay, Lake Nyasa (Tanzania), as a model system. Using data about infection of E. sardella fish hosts by L. intestinalis collected for a period of 10 years, we explored whether parasite infection affects the fecundity of the fish host E. sardella, and whether host reproductive investment has increased at the expense of somatic growth. We found that L. intestinalis had a strong negative effect on the fecundity of its intermediate fish host. For the noninfected fish, we observed an increase in relative gonadal weight at maturity over the study period, while size at maturity decreased. These findings suggest that the life history of E. sardella has been shifting toward earlier reproduction. Further studies are warranted to assess whether these changes reflect plastic or evolutionary responses. We also discuss the interaction between parasite and fishery‐mediated selection as a possible explanation for the decline of E. sardella stock in the lake. [ABSTRACT FROM AUTHOR]

Fluoride is an essential trace element for humans and animals. Here, we explored the effects of sodium fluoride (NaF) on morphological, hormonal and histological changes in ovary of Asian stinging catfish Heteropneustes fossilis (Bloch) after exposure to 1/10th mg and 1/5th mg F/L of LC50 of fluoride in water for 45 and 90 days. Activities of follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T) and estradiol (E) were measured using an enzyme-linked immunosorbent assay. Histological evaluation of the ovaries was conducted after staining with haematoxylin-eosin (HE). Reproductive hormones were significantly decreased after NaF-treated groups. Ovary was found to be adversely effected by exposure to NaF. Maturation of follicles was inhibited by exposure after observation of GSI and histology in ovary. These results suggest that female reproductive system is adversely affected by NaF. NaF may thus significantly reduce the fertility of female fish. This study encompasses alteration in hormonal assay to evaluate the role of vitamins C in the recovery of fluoride toxicity in fish. Vitamin C is a water-soluble ROS scavenger with high potency. [ABSTRACT FROM AUTHOR]