Search Results (733)

AQP8-type water channels are expressed superficially in the plasma membrane or intracellularly in the inner mitochondrial membrane, where they respectively function in osmohomeostasis or as peroxiporins to alleviate oxidative stress. To date only single-copy AQP8 or AQP16 genes are known in tetrapods and two binary gene clusters composed of aqp8aa-aqp8ab and aqp8ba-aqp8bb in teleost fishes. Here, using phylogenomic and synteny analyses, we revise this view and show that bony fish aqp8aa, -ab, -ba and -bb genes are non-canonical co-orthologs that independently arose at chromosomal breakpoints. Conversely, canonical orthologs of tetrapod AQP8 are now detected in all vertebrate classes except hagfishes. In cartilaginous fishes, intact aqp8 orthologs and linked pseudogenes exist in squalomorph sharks and only fractionated aqp8-like pseudogenes in galeomorph sharks. Some isolated aqp8-like exons are detected in batoid ray genomes, while no aqp8-type coding sequences are currently found in holocephalan genomes. In the actinopterygian (ray-finned fish) lineage, the canonical ortholog of tetrapod AQP8 is estimated to have undergone gene translocation in their common ancestor ~400 million years ago but was subsequently inactivated or lost in many descendant lineages. In close temporal proximity to this gene translocation event, the actinopterygian aqp8aa-aqp8ab binary gene cluster was generated in the original syntenic locus, potentially as a result of meiotic recombination. Our data support a model of total chromosomal replication for the generation of AQP16 genes and the teleost aqp8ba-aqp8bb gene cluster. We further uncover additional duplicates in Strepsirrhini primates that provide an eminent example of the stochastic nature of neofunctionalization. The present data thus suggest that that common ancestral genome duplications combined with lineage-level chromosomal translocation, recombination and replication events contributed to the diversification of vertebrate AQP8-type genes. Full article

Accurate measurement of antigen-specific antibody responses is essential for evaluating antibody avidity and quantification. Traditional. Enzyme-Linked Immunosorbent Assay (ELISA), while widely used, is limited by lengthy procedures, dependence on secondary antibodies, and inconsistent reproducibility. In this study, biolayer interferometry (BLI) was established and validated for simultaneous quantification and avidity assessment of specific IgM in serum of Larimichthys crocea (Large yellow croaker) using Pseudomonas plecoglossicida outer membrane protein Omp-H as antigen. Sera from immunized and control fish were analyzed by both BLI and ELISA, with systematic comparison between platforms. Optimal serum dilutions were 1:128 for BLI and 1:1024 for ELISA. Validation with another outer membrane protein, Omp-W, confirmed the method’s broad applicability. BLI association signals and avidity indices correlated strongly with ELISA values, yielding consistent results for both antigens. BLI successfully captured specific antibody responses in infected sera and demonstrated superior inter-plate reproducibility compared to ELISA, which exhibited significant inter-plate variation. However, BLI required lower serum dilutions (hence larger volumes) to achieve comparable sensitivity. These findings establish BLI as a rapid, single-step method providing reliable quantitative and avidity data for teleost IgM, offering a reproducible alternative to ELISA with potential applications in vaccine evaluation and aquaculture infection detection. Full article

The molecular mechanisms underlying freezing recovery in vertebrates, particularly in teleost fish, remain inadequately understood. This study utilized an integrated approach combining brain transcriptomics and gut microbiota analysis to investigate the recovery process in the freeze-tolerant species Perccottus glenii following experimental freezing and thawing. Significant transcriptomic reprogramming was observed in brain tissue, with the PPAR signaling pathway strongly activated immediately upon thawing (R0), potentially facilitating lipid metabolism and neuroprotection during ischemic stress. After 4 h of recovery (R4), circadian rhythm pathways were significantly upregulated, suggesting a potential role in coordinating metabolic recovery during reperfusion. Concurrently, gut microbiota analysis revealed substantial community shifts, characterized by a marked decrease in Bacillota and an increase in Pseudomonadota during the initial recovery phase. These findings suggest that successful freezing recovery in P. glenii is associated with coordinated changes in brain and gut, highlighting potential roles of metabolic adaptation and microbial ecological dynamics under the specific freezing protocol employed. Full article

This study employed a 2 × 2 factorial design to investigate the transcriptomic responses of common carp intestine under the single and combined stress of high temperature and zinc. Results from Illumina RNA-seq, WGCNA, and qPCR showed high-quality sequencing data with good reproducibility. High temperature was the core driver of global transcriptomic reprogramming, inducing numerous DEGs via activating metabolic and stress signaling pathways. Zinc alleviated heat stress by reducing DEGs by 43.2% and activating DNA repair and cell cycle pathways. WGCNA identified core modules for heat response and zinc mitigation, revealing “emergency defense” and “repair adaptation” strategies. This study enriches the teleost stress adaptation theory and provides a scientific basis for healthy carp aquaculture. Full article

The red cusk-eel (Genypterus chilensis) is an endemic Chilean teleost fish of significant importance to fisheries and aquaculture; however, no reference genome is available for this species. In this study, we present the first hybrid genome assembly of G. chilensis using Nanopore long-reads and Illumina short-reads, integrated with structural and functional annotations from RNA-seq data of the intestine and head kidney. The resulting genome assembly was 439.89 Mb in size, with an N50 of 7.96 Mb, containing 35,029 coding genes. Comparative genomics with G. blacodes revealed high similarity in genome size and completeness. Additionally, 14,681 lncRNAs were annotated, with 641 lncRNAs and 7323 coding genes differentially expressed in a tissue-specific expression pattern. These findings provide a high-quality genomic resource that enhances the understanding of lncRNA regulation and genome structure in the Genypterus genus. This study establishes a foundation for future research on commercial traits, conservation, and the evolution of the Ophidiiformes order. Full article

Genes involved in sexual development have been identified in many teleost fishes, including the turbot, a flatfish of high commercial value in aquaculture. In this species, a major sex determination (SD) Quantitative Trait Locus has been identified, and Sox2 has been proposed as the SD gene. Although RT-PCR, qPCR, and transcriptomic analyses have been performed on turbot gonads, histological studies remain limited. Here, we examined the tissue-specific expression patterns of several sex-related genes in turbot using in situ hybridization on paraffin sections (SISH) of differentiated ovaries and testes of juvenile and adult specimens. Vasa, Foxl2, Amh, Sox2 and Sox17 transcripts were detected in both male and female gonads, whereas Cyp19a1a and Sox19 expression was restricted to the ovary; these results support previous gene expression analyses and suggest a role for these genes in gonadal development and reproductive functions in this species. SISH provides complementary information to molecular analyses by identifying the specific cell types expressing the sex-related genes analyzed in gonadal tissue, thereby offering a more comprehensive understanding of gonadal differentiation in turbot. Comparison with results reported for the gonads of other teleost species revealed similar tissue-specific gene expression patterns during sexual development. Full article

The brown trout (Salmo trutta) is a commercially and ecologically significant salmonid fish, yet its hepatic cellular and functional dynamics throughout the reproductive cycle remain poorly characterised, particularly in males. This study investigated seasonal and sex-specific liver plasticity across four reproductive stages: spawning capable (December), regressing (March), regenerating (July), and developing (November). We quantified mRNA and protein abundance of key oestrogen-responsive targets—vitellogenin (VtgA) and zona pellucida (ZP) proteins—alongside cell turnover markers, caspase 3 (Casp3) and proliferating cell nuclear antigen (PCNA). These molecular endpoints were integrated with stereological analyses to estimate hepatocyte, nuclear, and cytoplasmic volumes. Results revealed stage-dependent mobilisation and transient hepatic retention of reproductive proteins; females exhibited stronger vitellogenic signatures and more pronounced seasonal shifts than males. Although VtgA and ZP mRNA levels peaked during the developing and spawning-capable stages, males maintained low but consistent levels throughout the cycle, indicating constitutive hepatic oestrogen sensitivity. Regarding cell turnover, PCNA protein data indicated heightened proliferative activity during the spawning-capable and regressing stages. In contrast, while Casp3 mRNA levels remained stable across all stages, protein detection suggested a post-transcriptional increase in apoptotic signalling during the developing phase, consistent with controlled tissue remodelling rather than extensive cell loss. Stereological data confirmed enlarged hepatocyte and nuclear volumes during periods of high secretory and proliferative demand. Overall, these findings demonstrate significant stage-dependent and sex-specific plasticity in brown trout liver, providing a robust reference framework for ecological monitoring, endocrine disruption assessments, and studies of teleost reproductive physiology. Full article

Background: Infectious hematopoietic necrosis virus (IHNV), a rhabdovirus classified within the genus Novirhabdovirus, continues to be one of the most detrimental pathogens impacting salmonid aquaculture on a global scale. Notable for inducing high mortality rates among fry and fingerlings, IHNV represents a substantial threat to the economic stability of the aquaculture industry. This review offers an in-depth analysis of the contemporary advancements in IHNV vaccine development. Methods: We assess the efficacy and immunological mechanisms of traditional vaccine platforms, including inactivated and live-attenuated vaccines, while emphasizing the groundbreaking success of DNA vaccines, particularly those encoding the viral glycoprotein (G). Although nucleic acid-based therapies provide high levels of protection, they face logistical challenges related to delivery and regulatory obstacles associated with Genetically Modified Organisms (GMOs). Additionally, we examine emerging “next-generation” platforms, such as viral vector vaccines, subunit proteins produced in yeast or plant systems, and RNA-based technologies. We critically analyze technical bottlenecks, including the lack of efficient mucosal delivery systems and the limited understanding of long-term cellular memory in teleosts. Results: We propose future research directions that emphasize the development of multivalent formulations and the incorporation of molecular adjuvants to augment mucosal immunity. Conclusions: This synthesis seeks to integrate fundamental viral pathogenesis with applied immunology to develop a strategic framework for the sustainable, long-term management of IHNV in global salmonid populations. Full article

The yellowfin seabream (Acanthopagrus latus) is an important aquaculture species, yet endocrine gene regulation during practical fasting and feeding schedules remains poorly understood. Here, we identified and characterized two duplicated proglucagon genes (Gcga and Gcgb) and examined tissue distribution of expression and transcriptional responses to feeding-related challenges. Sequence and phylogenetic analyses confirmed that Gcga and Gcgb cluster with teleost proglucagon paralogs and contain conserved peptide domains. Both genes were broadly expressed, with the strongest relative qRT-PCR signal detected in brain and fin, while other tissues (including intestine, gill, stomach, and liver) showed comparatively low but detectable expression. Because the liver is a central metabolic organ and displayed reproducible feeding-dependent regulation, we further quantified hepatic transcription under two paradigms. In a short-term starvation–refeeding trial, hepatic Gcga was significantly suppressed during fasting and rebounded after refeeding, whereas Gcgb showed a distinct, weaker response. In an acute peri-feeding assay, hepatic Gcga and Gcgb displayed rapid but differential regulation around meal time, and Gcgb expression differed between feeding and non-feeding groups. Together, these results support transcriptional divergence between the two proglucagon paralogs in nutritional regulation within a liver-focused metabolic-response model. Our findings provide baseline molecular information for A. latus and offer endocrine insights relevant to evaluating feeding strategies in aquaculture. Full article

N. chui is an economically important marine fish species distributed along the coastal waters of China, renowned for its delicate flesh texture and high-quality dried swim bladder. However, its scientific name and taxonomic relationship with N. coibor have long remained controversial, hindering accurate resource assessment and germplasm management. To address this issue, we sequenced and annotated the first complete mitochondrial genome of N. chui (GenBank accession: PZ024444). The circular mitogenome is 16,504 bp in length and contains 37 typical genes, with gene arrangement, nucleotide composition (A + T content: 52.07%), and codon usage patterns consistent with general teleost characteristics. Phylogenetic analyses based on 13 concatenated protein-coding genes revealed that N. chui and N. coibor form a maximally supported monophyletic clade (bootstrap support = 100%), with a pairwise genetic distance of 0. These mitochondrial results strongly suggest that the two nominal taxa are very closely related and may represent the same species. However, formal taxonomic synonymy cannot be established on mitochondrial evidence alone and requires further evaluation through examination of type material and comparative morphological study. Gene-specific selection pressure analyses showed that most mitochondrial protein-coding genes were subject to purifying selection, with ATP8 exhibiting the highest mean ω among genes with ω < 1, whereas ND5 and ND6 showed elevated ω values that warrant cautious interpretation. This study provides essential mitochondrial genomic resources for future research on species delimitation, phylogeny, and conservation of this important sciaenid fish. Full article

Melatonin, a well-known antioxidant, has been widely used in sperm cryopreservation of various animals, but its regulatory mechanism in fish remains unclear. This first study on teleosts suggests a potential molecular mechanism by which melatonin may improve post-thaw sperm quality of Epinephelus fuscoguttatus via targeting mitochondrial function. Compared with the melatonin group, the MT1 receptor-inhibited group showed slightly higher sperm motility (77.09 ± 3.41% vs. 76.50 ± 1.10%), significantly inhibited mitochondrial permeability transition pore (mPTP) opening (12.64 ± 1.05% vs. 18.29 ± 1.38%), and maintained higher mitochondrial membrane potential (MMP; 85.86 ± 0.18% vs. 81.81 ± 0.69%), with both groups performing better than the control. In contrast, the MT2-inhibited and MT1/2 dual-inhibited groups exhibited reduced sperm quality compared with the MT group, suggesting that MT2 may serve as the core receptor for melatonin to regulate mitochondrial homeostasis in teleosts. Mechanistically, melatonin-activated MT2 potentially inhibits mPTP opening via the PI3K/Akt/GSK-3β pathway, and this protective effect was abrogated by the PI3K and GSK-3β inhibitors. This receptor-mediated process synergized with melatonin’s direct antioxidant effect, as ROS levels in all melatonin-treated groups were significantly lower than the control. This study is the first to find pharmacological evidence for the melatonin–MT2/PI3K/GSK-3β axis in maintaining teleost sperm mitochondrial function; it also reveals potential mechanistic differences between teleosts and mammals and fills a critical knowledge gap regarding this signaling cascade in teleost reproductive biology. Full article

Saline–alkaline water constitutes a vital strategic non-traditional fishery resource in China, characterized by high pH values, elevated carbonate alkalinity, and complex ionic compositions. These extreme environmental conditions impose significant stress on aquatic animals, mainly by inducing ionic toxicity and disrupting acid–base regulatory mechanisms. Such disruptions subsequently lead to osmotic imbalance, metabolic dysregulation, and immunosuppression, thus restricting the survival and growth of aquatic species in aquaculture systems. Consequently, the sustainable development of the saline–alkaline aquaculture is imperative for enhancing production efficiency and promoting the utilization of marginal land and water resources. This review comprehensively summarizes the current status of saline–alkaline aquaculture and highlights the stress-inducing impacts of salinity, alkalinity, and specific ionic ratios on teleost fishes and crustaceans. It further explores key adaptive mechanisms, including osmoregulatory and ionoregulatory strategies, bioenergetic trade-offs related to oxygen consumption and ammonia excretion, coordinated antioxidant and innate immune responses, as well as recent findings from multi-omics research. This review aims to offer a scientific foundation for the selection and breeding of saline–alkaline-tolerant strains, the precise regulation of aquaculture water environments, and the development of ecological aquaculture models in saline–alkaline regions, thereby facilitating the sustainable utilization of saline–alkaline land and water resources. Full article

The single mental barbel is a distinctive feature of the benthic Antarctic fishes of the «cryonotothenioid» subfamily Artedidraconinae. These barbels are unusual because their primary sensory modality is tactility, not chemosensation as in most other teleosts. They also exhibit considerable interspecific and intraspecific variation in length and in the appearance of the terminal expansion and its epidermis. Barbels range from short to long and the terminal expansion can be nonexistent, small and round, or large and oblong. In most species, the epidermal surface of the terminal expansion exhibits projections of various shapes and sizes. These range from smooth and furrowed, to ridged and furrowed, to pointed, to palmate (having lobes originating from a common point), and to fringed and leaf-like. Barbels are also subject to intraspecific variation among the species in the genera Dolloidraco, Histiodraco, Artedidraco and Pogonophryne. The various epidermal surface patterns all increase the sensory surface area exposed to the substrate and may enhance detection of their prey, primarily polychaetes. They also enhance surface roughness of the epidermis, thereby dissipating mechanical forces and providing some protection from abrasion by the substrate. The various patterns are likely an epigenetic response to different local conditions of the substrate. This variation warrants caution in their use as a defining taxonomic character. Full article

Sex determination in teleost fishes exhibits remarkable evolutionary plasticity; however, the underlying mechanisms remain largely elusive for many species of high economic importance. Herein, we provide the first genome-wide investigation of the genetic basis of sex determination in the European anchovy (Engraulis encrasicolus), an ecologically and commercially vital clupeiform fish. Using low-pass whole-genome resequencing of 100 sexually mature individuals (50 females and 50 males), we conducted a genome-wide association study (GWAS) and F_ST scans to identify sex-linked loci and characterize sex-determining regions (SDRs). Our analyses revealed two major candidate SDRs located on chromosomes 14 and 18, encompassing multiple sex-associated single-nucleotide polymorphisms (SNPs) and insertions/deletions (InDels). Among these, the amhr2 (anti-Müllerian hormone type 2 receptor) gene on Chr14 displayed the strongest and most consistent association with phenotypic sex, marked by several male-specific missense SNPs and InDel variants. Comparative and transcriptomic analyses confirmed sex-biased expression of amhr2 and other SDR-linked genes, potentially indicating a male heterogametic (XY-like) genetic sex determination system. These results provide the first molecular evidence for a candidate SDR in E. encrasicolus, raise the possibility of involvement of amhr2 and additional loci in sex determination, and highlight rapid sex chromosome turnover within Clupeiformes. Our findings not only expand the understanding of teleost sex determination evolution but also establish a genomic foundation for developing molecular tools for sex identification and population management in anchovy fisheries. Full article

Swim bladders in some teleost fish can act as gas-filled cavities that oscillate under acoustic pressure and transfer the sound energy to the inner ears. Quantifying the resonance frequency and damping of these oscillations is useful for linking swim bladder mechanics to hearing-related and behavioural questions, but many established direct-measure approaches have relied on open-water deployments and careful avoidance of boundary reflections, making experiments logistically demanding and difficult to reproduce (e.g., requiring deep-water sites, careful control of surface/boundary reflections, and complex deployment geometries). This study presents a compact laboratory methodology for estimating swim bladder resonance properties using a closed, fully water-filled, stainless-steel impedance tube. Broadband pseudorandom excitation is applied via an end-plate shaker, and the acoustic response of the system is recorded using wall-mounted hydrophones. Resonance peaks are identified using power spectral estimates of recorded signals, allowing resonance frequency and quality factor to be extracted from the peak location and −3 dB bandwidth. The approach is first established using inflated latex balloons as surrogate encapsulated gas cavities, providing a controlled benchmark for repeatability and interpretation. It is then applied to recently euthanised brown trout (Salmo trutta), where clear resonance features attributable to the swim bladder are observed and show systematic variation with body size. A coupled finite element model reproduces the principal resonance behaviour under the experimental loading and supports interpretation of the measured peaks as swim bladder resonance. The results provide a validated foundation for subsequent non-invasive measurements on live, free-swimming fish, as well as for future applications where swim bladder condition may be relevant to management or conservation. Full article