Male Fish Research Articles

Effects of buccal cavity parasite Ceratothoa carinata (Isopoda, Cymothoidae) on the condition and reproduction of its host fish Japanese scad Decapterus maruadsi.

All species of the isopod family Cymothoidae are obligate fish parasites, extracting nourishment through hematophagy and tissue consumption. To elucidate the detrimental effects of this parasitic relationship upon the host fish, we examined body length, weight of body, gonad, liver and stomach contents, and condition factor of Japanese scad Decapterus maruadsi infected with the buccal cavity parasite Ceratothoa carinata in different seasons. During the host fish's breeding season in July, the wet weight and condition factor of male and female host fish ages 1 and 2 were conspicuously diminished. No impacts were detected in September, after the breeding season. We found no impact of the parasite on the stomach content weight or signs of prey fish in the stomachs. Thus, parasite infection with C. carinata potentially diminishes the reproductive success of the host fish by negatively impacting the host's physiological condition, particularly during the breeding season.

Sex-specific divergent responses of marine medaka (Oryzias melastigma) towards long-term benzo[a]pyrene exposure revealed stronger resilience and recoverability in female fish

Benzo[a]pyrene (BaP), a representative five-membered polycyclic aromatic hydrocarbon, has been extensively studied as a pollutant for decades. Despite this, sex-specific responses to BaP exposure remain poorly understood. This study employed a life-cycle exposure approach to investigate the effects of prolonged BaP exposure on marine medaka (Oryzias melastigma), highlighting sex-specific responses. After a 90-day exposure period, significant variations in biometric measurements and oxidative stress markers were observed between male and female fish. BaP exposure resulted in weak detoxification defense in males, while females exhibited an opposite response. Transcriptomic analysis revealed 13 significantly enriched pathways in males and 11 in females, with varying numbers of differentially expressed genes between the sexes, highlighting distinct biological responses. Host resistance assay showed higher mortality rates among BaP-exposed males, and suppressed immune gene expressions and lysozyme activity, while females demonstrated enhanced immune genes and lysozyme activity post-challenge, indicating a more resilient defense response. Furthermore, after a one-month depuration period following BaP exposure, male medaka demonstrated slower recoverability compared to females. These findings underscore sex-specific effects of BaP exposure on fish, with females displaying stronger resilience. Understanding these distinctions are crucial for accurately assessing the impact of environmental pollutants on the aquatic population and ecosystem maintenance.

Presence of abnormal otoliths in hallucinogenic fish and their comparison with normal otoliths using light and scanning electron digital imaging.

The otolith organs located in the inner ear of the fish are responsible for vital activities such as balance and hearing. Abnormalities in these organs can adversely affect the vital activities of the fish species. The main purpose of the study is to analyze the abnormalities in the otoliths of Sarpa salpa, known as the hallucinogenic fish. For that, 372 individuals of S. salpa are collected from the North Aegean Sea. As a result of the abnormality analyses in S. salpa otoliths, anomalies were detected such as various prominence structures on the surface of the otolith caused by accumulation and a more transparent appearance due to the different crystal structures in some parts of the otolith. These abnormalities were found in the left and/or right otoliths of male and female individuals in different total lengths. The percentage of individuals with abnormal otoliths of S. salpa is calculated as 52.42%. It was determined that there are statistical differences between the left and right otolith measurements of male and female individuals with abnormal and normal otoliths(p < 0.05). There is no relationship between the percentage of individuals showing abnormality and total length and sex. The current study presents for the first time abnormal otolith information on left and right otoliths in male and female S. salpa. It is thought that abnormalities in hallucinogenic fish otoliths could be related to genetic predisposition as well as stress due to nutritional preference, pollutants, and environmental factors. RESEARCH HIGHLIGHTS: The presence of abnormalities in the otoliths of Sarpa salpa, a hallucinogenic fish, was revealed for the first time. Abnormalities in the otoliths of S. salpa were identified, such as the presence of various prominence structures on the otolith's surface, loss of parts as well as a more transparent appearance in the outlines or surface of the otolith. Normal and abnormal otoliths of female and male hallucinogenic fish from different size groups were examined using light and scanning electron microscopy. Abnormality detected in the otoliths of hallucinogenic fish is not related to the gender and size of the fish.

Influence of humic acids on growth performance, bravery, stress resistance, antioxidant activity, and immune gene expression in male Siamese fighting fish (Betta splendens)

The current study investigated the effects of a humic acid supplement on the growth performance, antioxidant enzyme activity, immune-related genes, behavior and endocrinology of male Betta splendens fish. Fish species that are naturally exposed to high levels of humic substances in their environment are likely to perform better under captive conditions when given these substances. In this study, fish were fed a diet containing 0, 0.5 %, 1 %, and 1.5 % humic acid for six weeks. The results showed no significant differences in growth and feeding parameters between treatments (p > 0.05). The fish with a diet of 1.5 % humic acid showed more aggressive behavior in the mirror test than the control group (p < 0.05). In contrast, the fish fed a diet containing 1 % and 1.5 % humic acid showed a higher level of activity in the test with new objects than the control group (p < 0.05). The testosterone levels after aggression were significantly higher in the fish fed diets containing 1 % and 1.5 % humic acid than in the control group (p < 0.05). In addition, the humic acid-treated fish showed lower oxidative stress and cortisol production in common aquaculture stressors than the control (p < 0.05). Gene expression analysis showed upregulation of immune-related genes, including β-defensin 1, c-type lysozyme, interleukin-1β, and tumor necrosis factor-α, in response to humic acid supplementation compared to control (p < 0.05). Overall, the results of this study indicate that a diet containing 1 % humic acid has a positive effect on the physiology, immunology, and behavior of male B. splendens.

Effect of Physical Factors on Milt Quality of Malabar Grouper, Epinephelus Malabaricus in Summer and Winter Season

A study was conducted to test the effect of physical factors such as temperature, salinity, and pH on spermatozoa motility of Malabar grouper (Epinephelus malabaricus). Mature and healthy male fishes were collected from the Red Sea during the summer and winter seasons for milt collection. Milt quality was assessed for colour, volume, sperm cell concentration, motility, and viability. Sperm motility was tested under different water temperatures, salinity, and pH media. A significant difference (P &lt; 0.01) in sperm cell concentration (density), sperm motility (%), and viability (%) was observed between the summer and winter seasons. Changes in water temperature, pH, and salinity influenced sperm motility (%) and motility duration (min). Low pH and salinity caused adverse effects on spermatozoa motility. The results of the study are useful for the germplasm conservation of Malabar grouper, E.malabaricus.

Study of Some Environmental and Reproductive Aspects of Some Fish Species in the Tigris River West of the City of Samarra, Salah Al-Din / Iraq

The study was conducted on the Tigris River in the Qalaa area, west of the city of Samarra, Salah al-Din/Iraq, for the period between October 2023 and March 2024, 117 fish were caught, with one catch per month. It has been observed that the higher sex ratio tends to favor females in Carasobarbus luteus, Luciobarbus xanthopterus, Carassius auratus, Leuciscus vorax, and Cyprinus carpio with ratios of 7.0:1, 5.0:1, 4.6:1, 3.5:1 and 3.0:1 respectively, while the lower percentage tends to favor females in Acantho brama marmid, C. macrostomum and Chondrostoma regium in the ratio of 1.8:1, 1.5:1 and 1.19:1, respectively. show the monthly changes in gonad (G.S.I) function for male and female fish (Chondrostoma regium, Carassius auratus and Carasobarbus luteus), (Acantho brama marmid, Leuciscus vorax and Luciobarbus Xanthopterus) and (C. macrostomum and Cyprinus carpio) respectively. The water temperature ranged between 10 and 22°C. The highest water temperature was in October and the lowest in February. The highest value of dissolved oxygen was 8.4 mg/L in March and the lowest value of dissolved oxygen was 6.5 mg/L in October. The highest turbidity value was 49 NTU 1 in December, and the lowest value 39.5 NTU was recorded in February.

Asthma Among Manitoba Workers: Results from the Manitoba Occupational Disease Surveillance System

BackgroundThis study characterized the risk of new-onset asthma among workers in Manitoba, Canada. MethodsAccepted time loss claims from the Workers' Compensation Board of Manitoba from 2006 to 2019, containing workers' occupations and industries, were linked with administrative health data from 1996 to 2020. After restricting the cohort to the first claim per person in an occupation and applying age and coverage exclusions, the cohort comprised 142,588 person–occupation combinations. Asthma cases were identified if workers had at least two medical records for asthma (International Classification of Diseases, Ninth Revision, 493) within a 12-month period, within the 2 years before 3 years after cohort entry. New-onset asthma was identified using a 3-year washout period. Asthma hazard ratios by occupation and industry were estimated using Cox proportional hazard models, adjusted for age, and stratified by sex. ResultsIncreased asthma risk was observed among workers with known asthmagen exposure, including male veterinary and animal health technologists and technicians (hazard ratio 3.97, 95% CI 1.78–8.86), male fish processing workers (3.40, 1.53–7.57), and male machining tool operators (2.91, 1.72–4.92). Increases were also observed for occupations with unknown or suspected allergens, including gas station attendants, drivers, mail/postal and related workers, public works and maintenance laborers, mine laborers and crane operators, and some indoor worker groups. Decreased risks were observed among nurses and residential and commercial installer and servicers. ConclusionThis database linkage study successfully identified occupations and industries with known sensitizing agents or irritants, and several occupation and industries not typically associated with work-related asthma, warranting further investigation.

DNA methylation plays a critical role in testicular maintenance, but not in sex determination of male tilapia Oreochromis niloticus

The significance of DNA methylation in fish sex determination and differentiation is increasingly being recognized. Exploring the role of DNA methylation in sex determination and differentiation is advantageous for the advancement of sex control techniques in aquaculture. In this study, the global DNA methylation levels of XX and XY gonads at different developmental stages of tilapia (Oreochromis niloticus) was assessed using an anti-5-methylcytosin (5-mC) antibody. The results indicated that the difference of global DNA methylation levels between XX and XY gonads was established after morphological sex differentiation had occurred at 30 dah (days after hatching). The bisulfite sequencing PCR (BSP) analysis revealed a significant disparity in the DNA methylation level of cyp19a1a between the XX and XY gonads after 30 dah, rather than before. The Dnmts (DNA methyltransferases) inhibitor 5-aza-2′-deoxycytidine (5-aza-dC, 20 μg/g diet), the aromatase inhibitor letrozole (AI, 150 μg/g diet), and 17β-estradiol (E2, 150 μg/g diet) were employed for treating XX and XY tilapia in order to investigate the involvement of DNA methylation in sex determination and differentiation. Treatment of XX and XY fish with 5-aza-dC from 5 to 50 dah did not result in any sex reversal, either female-to-male or male-to-female. For XX tilapia, both the use of AI alone and its combination with 5-aza-dC resulted in sex reversal from female-to-male when treated from 30 to 60 dah. This indicates that the addition of 5-aza-dC did not prevent the sex reversal from female-to-male induced by AI treatment, which is different from the results observed in zebrafish (Danio rerio). Intriguingly, treatment of XY fish from 30 to 90 dah with either E2 or 5-aza-dC alone resulted in 6% and 0% sex reversal, respectively, while simultaneous treatment with 5-aza-dC and E2 resulted in significant decrease of cyp19a1a methylation level and increase of cyp19a1a expression and 65% sex reversal. Taken together, these results suggest that DNA methylation plays a critical role in gonadal maintenance, but not in sex determination in tilapia. This study deepens our understanding of the role of epigenetic modifications in fish sex differentiation and maintenance, providing an approach to achieve sex reversal in testis-differentiated male fish and improving the available methods for sex control in aquaculture.

Masculinization of Tilapia (Oreochromis Niloticus) by Oral Method Using Senggani Fruit Extract (Melastoma Malabathricum L.)

Introduction: Tilapia have different growth rates in male and female fish where the growth of male fish is faster than female. Therefore, in tilapia farming activities, the production of tilapia weighing &gt;100g/head is difficult to achieve due to uncontrolled spawning. Method: This study was designed using a completely randomized design (CRD) with 5 treatments and 4 replicates, namely treatment A (control), B (Senggani fruit extract 0.75 g/kg feed), C (extract 1.5 g/kg feed), D (extract 2.25 g/kg feed), E (extract 3 g/kg feed). The organisms used in the study were 7-day-old tilapia larvae. Tilapia larvae were given feed that had been added with Senggani fruit extract according to the treatment dose. Tilapia were reared for 62 days, and given artificial feed containing 41% protein, each feeding was given with a frequency of 3 times a day (morning, afternoon, evening). Results and Discussion: The results showed that the highest percentage of male sex was found in treatments A, B, C, D and E, which amounted to 50; 56.25; 57.5; 58.75; and 60%, respectively. Daily growth rate, survival and feed conversion ratio obtained during the study in each treatment amounted to 7.49, 7.45; 7.44; 7.46; and 7.40. for survival 73.75; 72.5; 72.5; 70; and 68.75 then the results of feed conversion ratio respectively 1.86; 1.88; 1.89; 1.86; and 1.91. The analysis showed that the highest percentage of male sex was found in the treatment of 3 g/kg feed which amounted to 60% (P&gt;0.05). Daily growth rate, survival rate and feed conversion ratio did not significantly affect the treatment given (p&gt;0.05). Conclusion: The results of water quality measurements obtained are still within the optimum limits for tilapia rearing. Conclusion: Feeding using Senggani fruit extract to masculinize tilapia did not have a significant effect (p&gt;0.05) on the percentage of male tilapia, daily growth rate and feed conversion ratio.

Sonic hedgehog (shh) gene from Pseudopleuronectes yokohamae (Teleostei: Pleuronectidae): Molecular cloning, characterization, and expression profile during early embryonic, juvenile, and adult stages.

The hedgehog signaling pathway plays an important role in early development and growth of most vertebrates. Sonic hedgehog (shh) gene is a critical regulator of embryonic development in many species, including humans. However, it is not clear what roles shh can play in the development of fish. In this paper, shh gene was cloned from Pseudopleuronectes yokohamae. The full-length complementary DNA (cDNA) of P. yokohamae sonic hedgehog gene (Pyshh) comprises 3194 bp, with a 1317-bp open reading frame (ORF) that encodes a polypeptide of 438 amino acids with a typical HH-signal domain and Hint-N domain. The conserved sequences of the protein among species were predicted by using multiple sequence comparison. The phylogenetic tree construction showed that PySHH is clustered in a branch of Pleuronectidae. To explore the expression of Pyshh gene in various tissues of P. yokohamae, we used real-time fluorescence quantitative PCR technology to detect it. The results showed that Pyshh gene is widely distributed in various tissues of P. yokohamae juveniles, different tissues of adult males and females, and is particularly expressed in immune organs. The Pyshh gene expression was higher in the muscle and brain of juvenile fish, and higher in bone, gill, and skin of male fish than that of female fish, suggesting that Pyshh might be involved in the formation of immune organs of P. yokohamae. The expression of Pyshh gene significantly upregulated from the gastrula stage to the hatching stage. Western blotting of the expression levels of PySHH during different embryonic development stages revealed that PySHH levels increased gradually during development stages from oosperm stage to hatching stage. These results indicate that Pyshh is highly conserved among species and plays a critical role in the complex process of embryonic development. Its precise regulation is essential for the proper formation of many organs and tissues in the body, and disruptions in its function may have serious consequences for the formation of immune organs in fish.

Improving photovoltaic cell parameter calculations through a puffer fish inspired optimization technique

The precise estimation of solar PV cell parameters has become increasingly important as solar energy deployment expands. Due to the intricate and nonlinear characteristics of solar PV cells, meta-heuristic algorithms show greater promise than traditional ones for parameter estimation. This study utilizes the Puffer Fish (PF) meta-heuristic optimization method, inspired by male puffer fish's circular structures, to estimate parameters of a modified four-diode PV cell. The PF algorithm's performance is assessed against ten benchmark test functions, with results presented as mean and standard deviation for validation. Comparative analysis with Particle Swarm Optimization (PSO), Grey Wolf Optimization (GWO), Rat Search Algorithm (RAT), Heap Based Optimizer (HBO), and Cuckoo Search (CS) algorithms highlights PF's superior performance, achieving optimal solutions with minimal error of 7.8947E-08. Statistical tests, including Friedman Ranking (1st) and Wilcoxon's rank sum (3.8108E-07), confirm PF's superiority. The circular structures of male puffer fish serve as an effective model for optimization algorithms, enhancing parameter estimation. Benchmark tests and statistical analysis consistently underscore PF's superiority over other meta-heuristic algorithms. Future research should explore PF's potential applications in solar energy and beyond.

Reproductive Biology Status Reproductive Biology Status of Moonfish (Mene maculata) in Palabuhanratu Bay during West Monsoon

The moonfish (Mene maculata) is a demersal fish with important ecological and economic value. The high use of pitcher fish as food fish has the potential to disrupt reproductive patterns, recruitment and stock availability of pitcher fish resources, for which information on reproductive biology is minimal during the west monsoon. This research aims to analyze the reproductive biology status of moonfish in Palabuhanratu Bay. The research period took place from September 2021 to February 2022 (representing the west monsoon), with a sample of 522 fish. Fish samples were taken using a simple random sampling method at Palabuhanratu Nusantara fishing port. The data was analysis to obtain the sex ratio, allometric growth pattern, spawning season, the reproductive potential, and the size at maturity. Results shown that the sex ratio was 1:0.76, which is dominated by male fish. Moonfish have a negative allometric growth pattern. The peak of spawning season during the study period was in September and October. Reproductive potential ranges from 11,988 to 21,164 eggs. The spawning pattern of moonfish is indicated as total spawner. The result of Spearman-Karber method analysis showed that the size of the first maturity of female and male moonfish (Lm50) was 143 mm and 150.5 mm TL, respectively. So, female moonfish mature gonads earlier than male fish.

Kondisi Aspek Biologi Reproduksi Ikan Silais (Kryptopterus hexapterus) di Sungai Bilah Kabupaten Labuhanbatu

Aspects of reproductive biology are important information in efforts to monitoring fish resources. Aspects of reproductive biology of K. hexapterus to be observed include: sex ratio, Gonadal Maturity Rate, and Gonadal Maturity Index. Fish sampling was carried out in October – December 2021 using splint net fishing gear. Determination of observation stations by purposive sampling method, where based on the location of fishermen install splint nets. The results obtained the sex ratio of male and female K. hexapterus (1: 0.34). Male of the Gonadal maturity Rate only at levels I-II while females are level I-IV. It can be concluded based on the results of the study, that there is too much difference in the ratio between male and female fish caught, so that Gonadal maturity Rate of male fish is not obtained that is ready to spawn. However, in female fish there are already those who reach Gonadal maturity Rate IV phase, this means they are ready to spawn. Male of the Gonad Maturity Index (0.12 - 0.43%) and female (0.11 - 2.98%). Conditions like these can make it difficult for female fish to find males who are also gonadally mature and equally ready to spawn.

Reversible Sterilization of Channel Catfish via Overexpression of Glutamic Acid Decarboxylase Gene.

The confinement of transgenic fish is essential to prevent their escape and reproduction in natural ecosystems. Reversible transgenic sterilization is a promising approach to control the reproduction of transgenic fish. Therefore, the present study was conducted to develop a reversibly sterile channel catfish (Ictalurus punctatus) via the transgenic overexpression of the goldfish (Carassius auratus) glutamic acid decarboxylase (GAD) gene driven by the common carp (Cyprinus carpio) β-actin promoter to disrupt normal gamma-aminobutyric acid (GABA) regulation. Three generations of GAD-transgenic fish were produced. All studied generations showed repressed reproductive performance; however, this was not always statistically significant. In F1, 5.4% of the transgenic fish showed a sexual maturity score ≥ 4 (maximum = 5) at five years of age, which was lower (p = 0.07) than that of the control group (16.8%). In the spawning experiments conducted on F1 transgenic fish at six and nine years of age, 45.5% and 20.0% of fish spawned naturally, representing lower values (p = 0.09 and 0.12, respectively) than the percentages in the sibling control fish of the same age (83.3% and 66.7%, respectively). Four of six pairs of the putative infertile six-year-old fish spawned successfully after luteinizing hormone-releasing hormone analog (LHRHa) therapy. Similar outcomes were noted in the three-year-old F2 fish, with a lower spawning percentage in transgenic fish (20.0%) than in the control (66.7%). In one-year-old F2-generation transgenic fish, the observed mean serum gonadotropin-releasing hormone (GnRH) levels were 9.23 ± 2.49 and 8.14 ± 2.21 ng/mL for the females and males, respectively. In the control fish, the mean levels of GnRH were 11.04 ± 4.06 and 9.03 ± 2.36 ng/mL for the females and males, respectively, which did not differ significantly from the control (p = 0.15 and 0.27 for females and males, respectively). There was no significant difference in the estradiol levels of the female transgenic and non-transgenic fish in the one- and four-year-old F2-generation fish. The four-year-old F2-generation male transgenic fish exhibited significantly (p < 0.05) lower levels of GnRH and testosterone than the control fish. In conclusion, while overexpressing GAD repressed the reproductive abilities of channel catfish, it did not completely sterilize transgenic fish. The sterilization rate might be improved through selection in future generations.

The effect of photoperiod on maturation of gonads in male freshwater fish, Notopterus notopterus (Pallas) from Farhatabad Nala of Gulbarga district, Karnataka, India

The effect of photoperiod on maturation of gonads in male freshwater fish, Notopterus notopterus (Pallas) from Farhatabad Nala of Gulbarga district, Karnataka, India

Use of OODEV® in Improving the Reproductive Performance of Male Yellow Rasbora Fish Rasbora lateristriata (Bleeker, 1854)

A local commodity, Yellow rasbora fish Rasbora lateristriata (Bleeker, 1854), can potentially be used as a food resource by the Kulon Progo community. Added to that, cultivation or aquaculture is known to optimize this potential. Furthermore, Aquaculture will also prevent illegal fishing in nature, where yellow rasbora fish are listed as vulnerable species in the IUCN Red list. This study induced male yellow rasbora fish using the hormone OODEV® injection, which comprises the hormone Pregnant Mare Serum Gonadotropin (PMSG) and anti-dopamine. PMSG is a hormone that contains FSH as well as LH in it. Yellow rasbora fish were nurtured to the age of six months and treated with four different treatments (dose) for a month, namely 0 mL/Kg, 0.25 mL/Kg, 0.5 mL/Kg, and 0.75 mL/Kg. Observed parameters included motility (movement and duration) as well as sperm count, sperm viability, sperm morphology, sperm morphometry, gonadosomatic index (GSI), and survival rate (SR). Data obtained were analyzed using SPSS with the One-way ANOVA test and continued with Duncan's test if the results were significant. The obtained results had no significant effect on the IGS value (p&gt;0.05), with the highest value found at a dose of 0.75 mL/Kg. In addition, administration of OODEV® also improved sperm quality with the best results at 0.75 mL/Kg in terms of motility with the highest progressive movement compared to other doses but not significant (p&gt;0.05) compared to the control, and significantly (p&lt;0.05) longest movement duration compared to other doses, while in terms of morphometry it had the second widest middle piece area but not significant (p&gt;0.05) compared to other doses, widest tail area but not significant (p&gt;0.05) compared to other doses except with 0.25 mL/Kg, longest tail length (p&gt;0.05) but not significant with other doses except with 0.25 mL/Kg , and significantly (p&lt;0.05) had the longest sperm total length. Every dose showed a 100% percentage of survival rate.

Effect of Additional Dried Tubifex sp. in Commercial Feed Against Color Intensity of Guppy (Poecilia reticulata)

Guppy fish (Poecilia reticulata) is a type of ornamental fish that is in great demand, because of its small size and beautiful color. The color of ornamental fish will generally fade, due to a lack of carotenoids in their feed. The purpose of this study was to determine the effect of giving Tubifex sp. in commercial feed to increase the color intensity of guppy fish and the best dose of Tubifex sp. The test fish used were male guppy fish strain HB Red. This study used a completely randomized design (CRD) method with five treatments and three replications, that is commercial feed with the addition of Tubifex sp. with doses of 0% (P1), 2% (P2), 4% (P3), 6% (P4), and 8% (P5). Parameters observed were color intensity (chroma value), survival, and water quality. Addition of Tubifex sp. in commercial feed gave the effect with the highest yield on P5 at a dose of 8%, with an increase in color intensity (chroma value) of 4,21±0,25d. At P1 it gave an increase of 1,19±0,02a, P2 was 1,34±0,04a, P3 was 1,81±0,21b, and P4 was 2,88±0,18c. So, the best treatment is P5 (8%). Survival showed the results were not significantly different, that is 100%. Water quality is included in the tolerance limit of fish with the results of temperature 26,6 – 27,4°C, pH 7,4 – 7,9, and DO 6,2 – 7,7 mg/L.

Environmentally relevant estrogens impaired spermatogenesis and sexual behaviors in male and female zebrafish

Environmental estrogens (EEs) are found extensively in natural waters and negatively affect fish reproduction. Research on the reproductive toxicity of EEs mixtures in fish at environmentally relevant concentrations is scarce. In this study, adult male zebrafish were exposed for 60 days to EES (a mixture of EEs), EE2-low (5.55 ng/L, with an estrogenic potency equal to EES), and EE2-high (11.1 ng/L). After exposure, the expression levels of vtg1, vtg3, and esr1 in the livers in EES-treated fish remained unaltered, whereas they were significantly increased in EE2-treated fish. Both EE2-high and EES exposures notably reduced the gonad somatic index and sperm count. A disrupted spermatogenesis was also observed in the testes of EE2-high- and EES-exposed fish, along with an alteration in the expression of genes associated with spermatogonial proliferation (pcna, nanog), cell cycle transition (cyclinb1, cyclind1), and meiosis (aldh1a2, cyp26a1, sycp3). Both EE2 and EES significantly lowered plasma 11-ketotestosterone levels in males, likely by inhibiting the expression level of genes for its synthesis (scc, cyp17a1 and cyp11b2), and increased 17β-estradiol (E2) levels, possibly through upregulating the expression of cyp19a1a. A significant increase in tnfrsf1a expression and the tnfrsf1a/tnfrsf1b ratio in EE2-high and EES-treated males also suggests increased apoptosis via the extrinsic pathway. Further investigation showed that both EE2-high and EES diminished the sexual behavior of male fish, accompanied with reduced E2 levels in the brain and the expression of genes in the kisspeptin/gonadotropin-releasing hormone system. Interestingly, the sexual behavior of unexposed females paired with treated males was also reduced, indicating a synergistic effect. This study suggests that EES have a more severe impact on reproduction than EE2-low, and EEs could interfere not only with spermatogenesis in fish, but also with the sexual behaviors of both exposed males and their female partners, thereby leading to a more significant disruption in fish reproduction.

High temperature exposure causes sexual dimorphism in immune responses against largemouth bass ranavirus (LMBV) in Micropterus salmoides

Largemouth bass (Micropterus salmoides) is an important freshwater fish species in aquaculture. Largemouth bass ranavirus (LMBV) infection at high temperature results in a considerably higher mortality rate in females than that in males. This study compared the spleen transcriptomes and analyzed the impact of sexual dimorphism on immunity and metabolism of largemouth bass infected with LMBV at high temperatures to gain a comprehensive understanding of the sex-based differences in immunity and metabolism of this species. (1) Compared with the ambient temperature group (W20), the high temperature group (W30) exhibited multiple significant differences in metabolic and immune terms, with several immunity-related pathways, including phosphatidylinositol 3-kinase-protein kinase B (PI3K-Akt) signaling pathway. Most identified pathways were associated with the estrogen signaling pathway, which also differed significantly. (2) Differences in glycolipid metabolism, immunity, and the endocrine and complex adaptive systems were distinctly different between male groups (W20M vs. W30M), whereas the female groups (W20F vs. W30F) were not significantly different. The male groups had a significantly higher number of enriched immunity-related KEGG pathways and differentially expressed genes (DEGs) and pathways related to the estrogen signaling pathway. (3) When comparing male and female samples infected with LMBV at the same temperature, no significant difference was observed between the ambient temperature groups (W20F vs. W20M). The high-temperature groups (W30F vs. W30M) had 18 immunity-related pathways among the top 25 enriched KEGG pathways, and gene expression correlation analysis of the DEGs showed positive correlations. This study demonstrates that the combined effects of high temperature and LMBV affect multiple metabolic and immune pathways in largemouth bass, thereby modulating immune responses by regulating the estrogen signaling pathway and influencing the expression of estrogen and its receptors. Under high-temperature conditions, male fish may have stronger estrogen signaling pathway-associated immune responses, which regulate immune pathways, including antigen processing and presentation, complement system, and phagocytosis. Consequently, males may have higher disease resistance than that of females. Our result contribute to mono-sex breeding and antiviral drug therapies available in largemouth bass, thereby markedly improving breeding efficiency.

Individual differences in the boldness of female zebrafish are associated with alterations in serotonin function.

One of the most prevalent axes of behavioral variation in both humans and animals is risk taking, where individuals that are more willing to take risk are characterized as bold while those that are more reserved are regarded as shy. Brain monoamines (i.e. serotonin, dopamine and noradrenaline) have been found to play a role in a variety of behaviors related to risk taking. Using zebrafish, we investigated whether there was a relationship between monoamine function and boldness behavior during exploration of a novel tank. We found a correlation between serotonin metabolism (5-HIAA:5-HT ratio) and boldness during the initial exposure to the tank in female animals. The DOPAC:DA ratio correlated with boldness behavior on the third day in male fish. There was no relationship between boldness and noradrenaline. To probe differences in serotonergic function in bold and shy fish, we administered a selective serotonin reuptake inhibitor, escitalopram, and assessed exploratory behavior. We found that escitalopram had opposing effects on thigmotaxis in bold and shy female animals: the drug caused bold fish to spend more time near the center of the tank and shy fish spent more time near the periphery. Taken together, our findings indicate that variation in serotonergic function has sex-specific contributions to individual differences in risk-taking behavior.