Reproductive toxic effects of chronic exposure to bisphenol A and its analogues in marine medaka (Oryzias melastigma).

As awareness of BPA's health risks has increased, many countries and regions have implemented strict controls on its use. Consequently, bisphenol analogues like BPF and BPAF are being increasingly used as substitutes. However, these compounds are also becoming increasingly prevalent in the environment due to production, use and disposal processes. The oceans act as a repository for various pollutants, and recent studies have revealed the extensive presence of bisphenols (BPs, including BPA, BPF, BPAF, etc.) in the marine environment, posing numerous health hazards to marine wildlife. Nevertheless, the reproductive toxicity of these chemicals on marine fish is not comprehensively comprehended yet. Thus, the histological features of the gonads and the gene expression profiles of HPG (Hypothalamic-Pituitary-Gonadal) axis-related genes in marine medaka (Oryzias melastigma) were studied after exposure to single and combined BPs for 70 days. The effects of each exposure group on spawning, embryo fertilization, and hatching in marine medaka were also assessed. Furthermore, the impacts of each exposure group on the genes related to methylation in the F2 and F3 generations were consistently investigated. BPs exposure was found to cause follicular atresia, irregular oocytes, and empty follicles in the ovary; but no significant lesions in the testis were observed. The expression of several HPG axis genes, including cyp19b, 17ßhsd, 3ßhsd, and fshr, resulted in significant changes compared to the control group. The quantity of eggs laid and fertilization rate decreased in all groups treated with BPs, with the BPAF-treated group showing a notable reduction in the number of eggs laid. Additionally, the hatching rate showed a more significant decline in the BPF-treated group. The analysis of methylated genes in the offspring of bisphenol-treated groups revealed significant changes in the expression of genes including amh, dnmt1, dnmt3ab, mbd2, and mecp2, indicating a potential transgenerational impact of bisphenols on phenotype through epigenetic modifications. Overall, the potential detrimental impact of bisphenol on the reproduction of marine medaka emphasizes the need for caution in considering the use of BPAF and BPF as substitutes.

Effects of salinity on behavior and reproductive toxicity of BPA in adult marine medaka.

Salinity is an important environmental factor influencing the toxicity of chemicals. Bisphenol A (BPA) is an environmental endocrine disruptor with adverse effects on aquatic organisms, such as fish. However, the influence of salinity on the biotoxicity of BPA and the underlying mechanism are unclear. In this study, we exposed marine medaka (Oryzias melastigma) to BPA at different salinities (0 psµ, 15 psµ, and 30 psµ) for 70days to investigate the toxic effects. At 0 psµ salinity, BPA had an inhibitory effect on the swimming behavior of female medaka. At 15 psµ salinity, exposure to BPA resulted in necrotic cells in the ovaries but not on the spermatozoa. In addition, BPA exposure changed the transcript levels of genes related to the nervous system (gap43, elavl3, gfap, mbpa, and α-tubulin) and the hypothalamic-pituitary-gonadal (HPG) axis (fshr, lhr, star, arα, cyp11a, cyp17a1, cyp19a, and erα); the expression changes differed among salinity levels. These results suggest that salinity influences the adverse effects of BPA on the nervous system and reproductive system of medaka. These results emphasize the importance of considering the impact of environmental factors when carrying out ecological risk assessment of pollutants.

A high-quality chromosome-level genome assembly of the Chinese medaka Oryzias sinensis.

Oryzias sinensis, also known as Chinese medaka or Chinese ricefish, is a commonly used animal model for aquatic environmental assessment in the wild as well as gene function validation or toxicology research in the lab. Here, a high-quality chromosome-level genome assembly of O. sinensis was generated using single-tube long fragment read (stLFR) reads, Nanopore long-reads, and Hi-C sequencing data. The genome is 796.58 Mb, and a total of 712.17 Mb of the assembled sequences were anchored to 23 pseudo-chromosomes. A final set of 22,461 genes were annotated, with 98.67% being functionally annotated. The Benchmarking Universal Single-Copy Orthologs (BUSCO) benchmark of genome assembly and gene annotation reached 95.1% (93.3% single-copy) and 94.6% (91.7% single-copy), respectively. Furthermore, we also use ATAC-seq to uncover chromosome transposase-accessibility as well as related genome area function enrichment for Oryzias sinensis. This study offers a new improved foundation for future genomics research in Chinese medaka.

Toxic effects of environmental concentration Bisphenol AF exposure on the survival, growth and reproduction of adult male Oryzias curvinotus.

Bisphenol AF (BPAF) is a novel environmental endocrine disruptor, and is widely detected in the aquatic environment, which is a potential threat to the health of fish. In this study, male Oryzias curvinotus were exposed to environmental concentrations (0.93 and 9.33 µg/L) of BPAF for 21 days. The effects of BPAF on survival, growth, reproduction, liver and testis histology, and gene transcriptional profiles of O. curvinotus were investigated. The results showed that the survival rate of male O. curvinotus slight decrease with increasing BPAF concentration, and there was no significant effect on body length, body weight, and K-factor. BPAF (9.33 µg/L) caused significant changes in testicular structure and reduced spermatid count in O. curvinotus. Changes in transcript levels of some antioxidant-related genes in gills and liver following BPAF exposure, imply an effect of BPAF on the immune system. After BPAF exposure, chgs and vtgs were up-regulated, validating the estrogenic effect of BPAF. In the hypothalamic - pituitary - gonadal axis (HPG) results, erα, erγ and cyp19a1b were all up-regulated in the brain, and the 0.93 µg/L BPAF group was more up-regulated than the 9.33 µg/L BPAF group. In testis, BPAF significantly up-regulated the mRNA expression level of cyp17a1 and cyp11b, while significantly down-regulated mRNA expression level of cyp11a, and cyp19a1 was significantly down-regulated only in the 0.93 µg/L BPAF group. In conclusion, environmental levels of BPAF have adverse effects on the survival and reproduction of O. curvinotus, and the potential toxic effects of environmental levels of BPAF cannot be ignored.

Single-cell transcriptome landscape of zebrafish liver reveals hepatocytes and immune cell interactions in understanding nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is becoming the most common chronic liver disease in the world. Immunity is the major contributing factor in NAFLD; however, the interaction of immune cells and hepatocytes in disease progression has not been fully elucidated. As a popular species for studying NAFLD, zebrafish, whose liver is a complex immune system mediated by immune cells and non-immune cells in maintaining immune tolerance and homeostasis. Understanding the cellular composition and immune environment of zebrafish liver is of great significance for its application in NAFLD. Here, we established a liver atlas that consists of 10 cell types using single-cell RNA sequencing (scRNA-seq). By examining the heterogeneity of hepatocytes and analyzing the expression of NAFLD-associated genes in the specific cluster, we provide a potential target cell model to study NAFLD. Additionally, our analysis identified two subtypes of distinct resident macrophages with inflammatory and non-inflammatory functions and characterized the successive stepwise development of T cell subclusters in the liver. Importantly, we uncovered the possible regulation of macrophages and T cells on target cells of fatty liver by analyzing the cellular interaction between hepatocytes and immune cells. Our data provide valuable information for an in-depth study of immune cells targeting hepatocytes to regulate the immune balance in NAFLD.

Toxic Effects of Bisphenol AF Exposure on the Reproduction and Liver of Female Marine Medaka (Oryzias melastigma).

In recent years, bisphenol AF (BPAF) in aquatic environments has drawn attention to its ecological risks. This study aims to investigate the toxic effects of BPAF (188.33 µg/L) exposure for 30 days on female marine medaka (Oryzias melastigma). On the 10th and 30th day of exposure, the toxicity was evaluated using histological analysis of the liver and ovaries and the transcription levels of genes related to the antioxidant system, immune system, and hypothalamic-pituitary-gonadal (HPG) axis. Findings revealed that (1) BPAF exposure caused vacuolation, karyopyknosis and karyolysis in the liver of marine medaka, and the toxic impact augmented with duration; (2) exposure to BPAF for 10 days facilitated the growth and maturation of primary ova, and this exposure had a comparatively inhibitory effect after 30 days; (3) exposure to BPAF resulted in a biphasic regulation of the transcriptional abundance of genes involved in antioxidant and inflammatory response (e.g., il-8, cat), with an initial up-regulation followed by down-regulation. Additionally, it disrupted the transcriptional pattern of HPG axis-related genes (e.g., 3ßhsd, arα). In conclusion, 188.33 µg/L BPAF can alter the expression levels of functionally related genes, impair the structural integrity of marine organisms, and pose a threat to their overall health.

The effects of 17α-methyltestosterone on gonadal histology and gene expression along hypothalamic-pituitary-gonadal axis, germ cells, sex determination, and hypothalamus-pituitary-thyroid axis in zebrafish (Danio rerio).

As a synthetic androgen, 17α-methyltestosterone (MT) is widely used in aquaculture to induce sex reversal and may pose a potential risk to aquatic organisms. This ecological risk has attracted the attention of many scholars, but it is not comprehensive enough. Thus, the adverse effects of MT on zebrafish (Danio rerio) were comprehensively evaluated from gonadal histology, as well as the mRNA expression levels of 47 genes related to hypothalamic-pituitary-gonadal (HPG) axis, germ cell differentiation, sex determination, and hypothalamus-pituitary-thyroid (HPT) axis. Adult zebrafish with a female/male ratio of 5:7 were exposed to a solvent control (0.001% dimethyl sulfoxide) and three measured concentrations of MT (5, 51 and 583 ng/L) for 50 days. The results showed that MT had no significant histological effects on the ovaries of females, but the frequency of late-mature oocytes (LMO) showed a downward trend, indicating that MT could induce ovarian suppression to a certain extent. The transcriptional expression of activating transcription factor 4b1 (atf4b1), activating transcription factor 4b2 (atf4b2), calcium/calmodulin-dependent protein kinase II delta 1 (camk2d1), calcium/calmodulin-dependent protein kinase II delta 2 (camk2d2) and calcium/calmodulin-dependent protein kinase II inhibitor 2 (camk2n2) genes in the brain of females increased significantly at all treatment groups of MT, and the mRNA expression of forkhead box L2a (foxl2) and ovarian cytochrome P450 aromatase (cyp19a1a) genes in the ovaries were down-regulated by 5 and 583 ng/L group, which would translate into inhibition of oocyte development. As compared to females, MT had relatively little effects on the reproductive system of males, and only the transcriptional alterations of synaptonemal complex protein 3 (sycp3) and 17-alpha-hydroxylase/17,20-lyase (cyp17) genes were observed in the testes, not enough to affect testicular histology. In addition, MT at all treatments strongly increased corticotropin-releasing hormone (crh) transcript in the brain of females, as well as deiodinase 2 (dio2) transcript in the brain of males. The paired box protein 8 (pax8) gene was significantly decreased at 51 or 583 ng/L of MT in both female and male brains. The above results suggest that MT can pose potential adverse effects on the reproductive and thyroid endocrine system of fish.

Transcriptome Analysis Revealed the Advantages of Room Temperature Preservation of Concentrated Oocystis borgei Cultures for Use in Aquaculture.

Oocystis borgei, a microalgae species employed for regulating the quality of aquaculture water, demonstrates the capacity to adsorb noxious substances, curtail the growth of detrimental bacteria, and outcompete blooming cyanobacteria. It can be concentrated by natural sedimentation and stored at room temperature, making it costless and simple to transport and use. To study the mechanism of adaptation to room temperature preservation, O. borgei was concentrated (1.19 × 107-1.21 × 107 cell/mL) and stored for 50 days at low (5 °C, LT), normal (25 °C, NT), and high (35 °C, HT) temperatures, respectively. Polysaccharide content, lipid content, cell survival, and resuscitation were evaluated. RNA-Seq was also used to examine how concentrated O. borgei responded to temperature. During storage, there was an increase in polysaccharide content and a decrease in lipid content, with both being significantly upregulated in the LT and HT groups. Survival and cell density were highest in the NT group. The RNA-Seq analysis revealed extensive differences in transcript levels. ATP synthesis was inhibited in the LT group due to the reduced expression of PsaD, PsaE, PsaF, PsaK, and PsaL. Under HT, the formation of reactive oxygen species (ROS) was facilitated by low levels of redox-related genes (nirA) and high levels of oxidative genes (gdhA, glna, and glts). The findings suggest that storing concentrated O. borgei at room temperature is optimal for microalgae preservation, enhancing theoretical research in this field. Our study provides further theoretical and practical support for the development of O. borgei as a live ecological preparation for aquaculture microalgae ecology management.

The First High-Quality Chromosome-Level Genome of the Lutjanus erythropterus (Bloch, 1790) Using Single-Tube Long Fragment Reads and Hi-C Technologies.

Lutjanus erythropterus (Bloch, 1790), a Perciformes from the Lutjanidae family, is a commercially important species because of its taste and abundance. Despite the increase in genome resources in recent years, few genome assemblies are available within this fish family for comparative and functional studies. In this study, we determined the chromosomal genome of Crimson snapper using high-throughput Single-Tube Long Fragment Reads sequencing technology and Hi-C data. The final assembly size was 973.04 Mb with contig and scaffold N50 values of 1.51 and 40.65 Mb, respectively. We successfully scaffolded 95.84% of the genome sequence onto 24 chromosomes ranging in length from 19.37 to 49.48 Mb. A total of 22,663 genes and 13,877 gene families were identified in the genome, with 29 gene families being L. erythropterus-specific. A phylogenetic analysis using single-copy gene families showed that L. erythropterus and Larimichthys crocea had the closest genetic relationship with a divergence time of ∼47.7 Ma. This new genomic resource will facilitate comparative genomic studies as well as genetic breeding programs for L. erythropterus.

The first high-quality chromosome-level genome of Eretmochelys imbricata using HiFi and Hi-C data.

Eretmochelys imbricata, a critically endangered sea turtle inhabiting tropical oceans and protected across the world, had an unknown genome sequence until now. In this study, we used HiFi reads and Hi-C technology to assemble a high-quality, chromosome-level genome of E. imbricata. The genome size was 2,138.26 Mb, with contig N50 length of 123.49 Mb and scaffold N50 of 137.21 Mb. Approximately 97.52% of the genome sequence was anchored to 28 chromosomes. A total of 20,206 protein-coding genes were predicted. We also analyzed the evolutionary relationships, gene family expansions, and positive selection of E. imbricata. Our results revealed that E. imbricata diverged from Chelonia mydas 38 million years ago and had enriched olfactory receptors and aging-related genes. Our genome will be useful for studying E. imbricata and its conservation.

Effects of bisphenols on lipid metabolism and neuro-cardiovascular toxicity in marine medaka larvae.

Bisphenols are environmental endocrine disruptors that have detrimental effects on aquatic organisms. Using marine medaka larvae, this study explored the effects of bisphenol compounds [bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF), and bisphenol AF (BPAF)] on the early growth and development of aquatic organisms. Marine medaka larvae were exposed to bisphenol compounds at concentrations of 0.05, 0.5, and 5 µM for 72 h, and changes in heartbeat rate, behavior, hormone levels, and gene expression were determined. Bisphenols were shown to have a toxic effect on the cardiovascular system of larvae and can cause neurotoxicity and endocrine disruption, such as changes to thyroid-related hormones. Functional enrichment showed that bisphenols mainly affect lipid metabolism and cardiac muscle contraction of larvae, which implied that the main toxic effects of bisphenols on marine medaka larvae targeted the liver and heart. This study provides a theoretical foundation for evaluating the toxicological effects of bisphenols on the early development of aquatic organisms.

Physiological and transcriptional effects in the male western mosquitofish (Gambusia affinis) following exposure to dexamethasone.

Dexamethasone (DEX) is a synthetic glucocorticoid widely found in a variety of aquatic environments and has potential adverse effects on aquatic organisms. This study was to assess the toxic effects of exposure to different concentrations (0, 5 and 50 µg/L) of DEX for 60 days on adult male mosquitofish (Gambusia affinis). Morphological analyses of skeleton and anal fin, histological effects of testes and livers, and transcriptional expression levels of genes related to reproductive and immune system were determined. The results showed that exposure to DEX significantly increased 14L and 14D values of hemal spines, which suggested DEX could affect skeleton development and result in more masculine characteristics in male fish. In addition, the damage to testis and liver tissue was observed after DEX treatment. It also enhanced mRNA expression of Erß gene in the brain and Hsd11b1 gene in the testis. The findings of this study reveal physiological and transcriptional effects of DEX on male mosquitofish.

Toxic effects of bisphenol AF on the embryonic development of marine medaka (Oryzias melastigma).

Bisphenol AF (BPAF), an emerging environmental endocrine disruptor, has been detected in surface waters worldwide and has adverse effects on aquatic organisms. The accumulation of BPAF in oceans and its potential toxic effect on marine organisms are important concerns. In this study, the effects of BPAF (10, 100, 1, and 5 mg/L) on marine medaka (Oryzias melastigma) were evaluated, including effects on the survival rate, heart rate, hatchability, morphology, and gene expression in embryos. The survival rate of marine medaka embryos was significantly lower after treatment with 5 mg/L BPAF than in the solvent control group. Exposure to 1 mg/L and 5 mg/L BPAF significantly reduced hatchability. Low-dose BPAF (10 µg/L) significantly accelerated the heart rate of embryos, while high-dose BPAF (5 mg/L) significantly decreased the heart rate. BPAF exposure also resulted in notochord curvature, pericardial edema, yolk sac cysts, cardiovascular bleeding, and caudal curvature in marine medaka. At the molecular level, BPAF exposure affected the transcript levels of genes involved in the thyroid system (dio1, dio3a, trhr2, tg, and thra), cardiovascular system (gata4, atp2a1, and cacna1da), nervous system (elavl3 and gap43), and antioxidant and inflammatory systems (sod, pparß, and il-8) in embryos. These results indicate that BPAF exposure can alter the expression of functional genes, induce abnormal development, and reduce the hatching and survival rates in marine medaka embryos. Overall, BPAF can adversely affect the survival and development of marine medaka embryos, and BPAF may not be an ideal substitute for BPA.

Short-term exposure to norethisterone affected swimming behavior and antioxidant enzyme activity of medaka larvae, and led to masculinization in the adult population.

Norethisterone (NET), one of the synthetic progestins, is detected with increasing frequency in the water environment and distributed in the ocean, with a potential toxicity risk to marine organisms. However, current studies on the adverse effects of progestins (including NET) in aquatic environments have focused on freshwater organisms, mainly fish. In the present, marine medaka (Oryzias melastigma) larvae were exposed to 91.31 ng/L NET for 10 days, and then the swimming behavior, oxidation-antioxidant-related enzyme activities, sex and thyroid hormone levels, and the gene transcription patterns of the larvae were measured. After NET treatment, medaka larvae were raised in artificial seawater until 5 months of age, and the sex ratio was counted. Ten-day exposure to 91.31 ng/L NET inhibited swimming behavior, of marine medaka larvae, which showed that the time in the resting state was significantly prolonged, while the time in the large motor state was significantly reduced; disrupted oxidative-antioxidant system, significantly up-regulated the enzymatic activities of reactive oxygen species (ROS), malondialdehyde (MDA), and glutathione peroxidase (GSH-Px); affected the hormone levels of larvae, lowered 11- keto testosterone (11-KT) and triiodothyronine (T3) concentrations. RNA-seq results showed that 91.31 ng/L NET exposure for 10 days changed the transcript levels of 275 genes, of which 28 were up-regulated and 247 were down-regulated. Differentially expressed genes (DEGs) were mainly significantly enriched in piwi interacting RNA (piRNA), gonadal development, gametogenesis, and steroidogenesis biological processes, etc. After removing NET exposure and returning to breeding for 140 days, a significant increase in male proportions (69.67%) was observed in sexually mature medaka populations in the NET-treated group. These results show that exposure to 91.31 ng/L NET for 10 days can lead to various adverse effects on marine medaka larvae. These findings shed light on the potential ecological risks of synthetic progestins to marine organisms.

Population genetic characteristics of Hainan medaka with whole-genome resequencing.

The DMY gene is deleted in all males of the Sanya population (SY-medaka) of the Hainan medaka, Oryzias curvinotus, as recently reported by us. However, due to limited knowledge regarding their population genetic background, it is difficult to explore the possible evolutionary pathway. Herein, we resequenced the whole genome of four populations, including SY-medaka. A total of 56 mitogenomes and 32,826,105 SNPs were identified. We found that the genetic differentiation is highest between SY-medaka and the other populations. The results of the population history of the O. curvinotus suggest that the SY-medaka has been in a bottleneck period recently. Further analysis shows that SY-medaka are the most strongly affected by environmental selection. Moreover, we screened some potential genomic regions, and the genes contained in these regions may explain the potential mechanism of the selection process of the SY-medaka. In conclusion, our study can provide new clues for the adaptation process of medaka in the new environment of Sanya.

Effects of bisphenol AF on growth, behavior, histology and gene expression in marine medaka (Oryzias melastigma).

Bisphenol AF (BPAF) is one of the substitutes for bisphenol A (BPA), which has endocrine-disrupting, reproductive and neurological toxicity. BPAF has frequently been detected in the aquatic environment, which has been a long-term threat to the health of aquatic organisms. In this study, female marine medaka (Oryzias melastigma) were exposed to 6.7 µg/L, 73.4 µg/L, and 367.0 µg/L BPAF for 120 d. The effects of BPAF on behavior, growth, liver and ovarian histology, gene transcriptional profiles, and reproduction of marine medaka were determined. The results showed that with the increase of BPAF concentration, the swimming speed of female marine medaka showed an increasing trend and then decreasing trend. BPAF (367.0 µg/L) significantly increased body weight and condition factors in females. BPAF (73.4 µg/L and 367.0 µg/L) significantly delayed oocyte maturation. Exposure to 367.0 µg/L BPAF showed an increasing trend in the transcript levels of lipid synthesis and transport-related genes such as fatty acid synthase (fasn), sterol regulatory element binding protein (srebf), diacylglycerol acyltransferase (dgat), solute carrier family 27 member 4 (slc27a4), fatty acid-binding protein (fabp), and peroxisome proliferator-activated receptor gamma (pparγ) in the liver. In addition, 6.7 µg/L BPAF significantly down-regulated the expression levels of antioxidant-related genes [superoxide dismutase (sod), glutathione peroxidase (gpx), and catalase (cat)], and complement system-related genes [complement component 5 (c5), complement component 7a (c7a), mannan-binding lectin serine peptidase 1 (masp1), and tumor necrosis factor (tnf)] were significantly up-regulated in the 73.4 and 367.0 µg/L groups, which implies the effect of BPAF on the immune system in the liver. In the hypothalamic-pituitary-ovarian axis (HPG) results, the transcription levels of estrogen receptor α (erα), estrogen receptor ß (erß), androgen receptor (arα), gonadotropin-releasing hormone 2 (gnrh2), cytochrome P450 19b (cyp19b), aromatase (cyp19a), and luteinizing hormone receptor (lhr) in the brain and ovary, and vitellogenin (vtg) and choriogenin (chg) in the liver of 367.0 µg/L BPAF group showed a downward trend. In addition, exposure to 367.0 µg/L BPAF for 120 d inhibited the spawning behavior of marine medaka. Our results showed that long-term BPAF treatment influenced growth (body weight and condition factors), lipid metabolism, and ovarian maturation, and significantly altered the immune response and the transcriptional expression levels of HPG axis-related genes.

A patched1 gene homologue participates in female differentiation of Cynoglossus semilaevis.

Patched (Ptch) is a receptor in the hedgehog signaling pathway, essential for animal development. Our previous study showed that ptch1 gene participates in the maintenance of the male germline and spermatogenesis in Cynoglossus semilaevis (csptch1). In this study, we identified a patched1 gene homolog (csptch1 x1). The csptch1 x1 gene is 5761 bp long, with a 4638 bp coding sequence that encodes 1545 amino acids. The Csptch1 x1 protein has 12 transmembrane regions and sterol-sensing domains and is highly homologous to the csptch1 (91 amino acids difference). Expression pattern analysis showed that csptch1 x1 is expressed in eight different tissues of adult tongue sole, and the expression is significantly higher in tissues of female than that in male tissues. The expression pattern in developmental stages was also analyzed. csptch1 x1 could be detected at the 1-cell stage and was highly expressed at the blastocyst, somite, and blastopore closing stages, implying that it participates in cell differentiation. In ovarian development, the expression of csptch1 x1 was initiated at 20 days after hatching (dah) and was significantly high at 35-50 and 95-150 dah. In situ hybridization showed that csptch1 x1 was predominantly expressed in primordial germ cells, oocytes, and follicular cells, but the expression of the gene was lower in the testis. These results suggest that csptch1 x1 may be mainly involved in female differentiation and ovarian development, different from the role of csptch1 in spermatogenesis.

A Potential Role of the Translation Elongation Factor eef1a1 in Gonadal High-Temperature Perception in Chinese Tongue Sole (Cynoglossus semilaevis).

The eukaryotic translation elongation factor 1 alpha (eef1a) gene has a well-defined role in protein synthesis. However, its role in external temperature perception and internal sex differentiation and development is still unclear. In this study, eef1a1 was identified and functionally analyzed in Chinese tongue sole (Cynoglossus semilaevis). The eef1a1 cDNA, 1809 bp in length, had a 1386 bp open reading frame (ORF) that encoded a 461 amino acid polypeptide containing one EF-1_alpha domain. eef1a1 expression levels were investigated across different tissues and during gonadal development. In the gonad, eef1a1 showed a sexually dimorphic expression pattern with a statistically higher expression level in the ovary than in the testis from 6 months postfertilization to 3 years postfertilization. Under high temperature (28 °C) treatment during C. semilaevis sex differentiation (from 30 days postfertilization to 3 months postfertilization), eef1a1 was statistically down-regulated in males, while the difference was not detected in females. In addition, the dual-luciferase assay exhibited that eef1a1 can respond to high temperature rapidly. Based on these results, C. semilaevis eef1a1 might have a dual role in the perception of external temperature changes and sex differentiation regulation.

Long-term exposure to bisphenol A and its analogues alters the behavior of marine medaka (Oryzias melastigma) and causes hepatic injury.

Bisphenols (BPA, BPF, and BPAF) are widely present in the aquatic environment and have various adverse effects on aquatic organisms. However, their hepatic toxicity in marine fish is not fully understood. Hence, we examined the growth parameters, histological features, antioxidant defense mechanisms, and gene expression profiles in the livers of marine medaka after exposure to single and combined bisphenols for 70 days. The final body weight and final body length of males exposed to BPAF were significantly higher than those in the control group, and the survival rate was significantly lower. Bisphenol exposure led to vacuolization and local lesions in the liver, especially in the BPAF group, and altered antioxidant enzyme activity in the liver, leading to oxidative stress. In addition, after bisphenol exposure, marine medaka showed anxiolytic effects and a significant reduction in swimming distance compared with that in the control group. As determined by RNA-seq, bisphenol exposure altered multiple biological pathways in the liver, such as fatty acid biosynthesis, fatty acid metabolism, and ribosome biogenesis pathways, with significant changes in gene expression levels. In particular, chgs and vtgs were significantly up-regulated after BPAF exposure, suggesting an estrogenic effect. Overall, bisphenols can adversely affect the growth and metabolism of marine medaka. BPF and BPAF may not be ideal substitutes for BPA.