Search Results (35)

Black rockfish (Sebastes schlegelii) is a marine ovoviviparous teleost that exhibits significant sexual dimorphism, with females growing faster and reaching larger sizes than males. Establishing stable oogonial stem cells (OSCs) is critical for understanding germline stem cell dynamics and facilitating all-female breeding. In this study, we successfully isolated and cultured OSCs from S. schlegelii for 12 passages. These cells exhibited alkaline phosphatase activity, expressed germline marker genes (ddx4, cdh1, klf4), and maintained a diploid karyotype (2n = 48). Transcriptomic comparisons between early (P3) and late (P12) passages revealed significant metabolic dysfunction and cell cycle arrest in the late-passage cells. Specifically, the down-regulation of glutathione-related and glycolysis-related genes (gstm3, gstt1, mgst3, gsta1, gsta4, gsto1, gapdh) and key mitotic regulators (cdk1, chk1, cdk4, e2f3, ccne2, ccnb1) suggested that metabolic imbalance contributes to oxidative stress, resulting in cell cycle inhibition and eventual senescence. This study provides a marine fish model for investigating metabolism-cell cycle interactions in germline stem cells and lays the foundation for future applications in germ cell transplantation and all-female breeding. Full article

This study evaluated the antibacterial activity and residual functional compounds of blood orange (Citrus sinensis L. Osbeck) juice by-product extract (BJBE). The effects of dietary BJBE on growth performance, digestive enzyme activity, antioxidant status, immune parameters, and disease resistance against Vibrio harveyi were examined in juvenile black rockfish (Sebastes schlegelii). In total, 630 juvenile rockfish were randomly assigned to 21 rectangular tanks (50 L) for a feeding trial, with 30 fish per tank in triplicate. Seven isonitrogenous and isolipidic experimental diets were formulated with BJBE at 0 (control, BJBE0), 0.1 (BJBE0.1), 0.2 (BJBE0.2), 0.3 (BJBE0.3), 0.5 (BJBE0.5), 0.7 (BJBE0.7), and 1.0 (BJBE1) g kg⁻¹. A disk diffusion assay confirmed BJBE’s strong antibacterial efficacy against V. harveyi. After an 8-week feeding trial, fish fed BJBE0.7 and BJBE1 exhibited significantly a greater final weight, weight gain, and specific growth rate compared with those fed BJBE0. Feed efficiency was significantly higher in fish fed BJBE0.7 than in those fed BJBE0. The protein efficiency ratio was significantly higher in fish fed BJBE0.3, BJBE0.5, BJBE0.7, and BJBE1 relative to those fed BJBE0. Intestinal amylase activity was significantly higher in fish fed BJBE0.7 and BJBE1 compared with those fed BJBE0, and trypsin activity was significantly higher in BJBE0.7-fed fish than in BJBE0-fed fish. In comparison to the BJBE0 diet, the plasma superoxide dismutase, catalase, and glutathione levels of fish fed BJBE0.7 and BJBE1 diets were significantly higher. Lysozyme activity and immunoglobulin M level in fish fed BJBE0.7 and BJBE1 were significantly higher than that in fish fed BJBE0. After a challenge with V. harveyi, disease resistance was significantly higher in fish fed BJBE0.5, BJBE0.7, and BJBE1 compared with those fed BJBE0. Overall, 0.7–1.0 g kg⁻¹ is proposed as the optimal dietary BJBE inclusion level for enhancing growth performance, digestive enzyme activity, antioxidant status, immune parameters, and disease resistance against V. harveyi infection in juvenile black rockfish. Full article

Aggressive behavior is regulated by intricate neural circuits and molecular mechanisms, notably through the interaction of brain-derived neurotrophic factor (BDNF) with its receptor, tropomyosin receptor kinase B (TrkB), which influences neuroplasticity and related behavioral phenotypes. We investigate the role of the BDNF signaling pathway in fish aggression using juvenile black rockfish (Sebastes schlegelii), which exhibit distinct aggressive phenotypes. The TrkB agonist 7,8-dihydroxyflavone (7,8-DHF) was administered intraperitoneally at doses of 1.25, 2.5, and 5 mg/kg to assess its effects on the behavioral characteristics of high-aggression (H-agg) and low-aggression (L-agg) phenotypes. Our findings indicate the following: (1) The effects of 7,8-DHF are dose-dependent, with 2.5 mg/kg identified as the effective threshold dose for H-agg individuals; (2) in the H-agg group, this dose significantly reduced locomotor acceleration, angular velocity, and activity frequency, while prolonging the first movement latency; (3) in the L-agg group, only angular velocity was significantly decreased with the 2.5 mg/kg treatment, with no significant changes observed in other behavioral parameters. This study provides the first evidence for differential behavioral responses to 7,8-DHF in S. schlegelii, demonstrating dose-dependent aggression suppression in H-agg phenotypes and threshold-specific responses in L-agg phenotypes. These insights into the neuro-molecular basis of fish aggression can guide phenotype-specific management in aquaculture, potentially improving stress management, reducing injuries and mortality, and boosting productivity. Full article

As a lysosomal cysteine protease of the papain subfamily, cathepsin B (CTSB) is characterized by its innate immune functions and hydrolytic activity. However, the functions of CTSB in the immune responses of teleosts remain to be clarified. In this study, two CTSB genes in S. schlegelii, SsCTSBa and SsCTSBb, were identified. Both SsCTSBa and SsCTSBb are composed of a 993 bp ORF encoding 330 amino acids. It was found in a phylogeny analysis that both genes form monophyletic clades with their orthologous counterparts of Honeycomb rockfish (Sebastes umbrosus). A synteny analysis indicated that the CTSB homologues were comparatively conserved during vertebrate evolution. Additionally, quantitative real-time PCR revealed the ubiquitous mRNA expression of SsCTSBa and SsCTSBb in all of the examined tissues, and substantially differential expression patterns could be observed following Aeromonas salmonicida infection. A subcellular localization analysis demonstrated that the distribution of SsCTSBa and SsCTSBb was mainly in the cytoplasm. Moreover, rSsCTSBa and rSsCTSBb showed strong binding to Poly(I:C) and exhibited diverse agglutination effects on different bacteria. Overall, these findings suggest that the CTSB genes in black rockfish might show essential functions in the host defense of teleosts against bacterial infections, providing valuable insights for further investigations into the immune mechanism of teleost CTSB. Full article

Spermatogenesis, the process of male germ cell development, is tightly regulated by the hypothalamic–pituitary–testis (HPT) axis in seasonally breeding teleosts. Despite its importance, our understanding of how the brain and male germ cells coordinate key transitions—such as testis initiation and maturation—remains limited, particularly in species with distinct seasonal reproductive cycles. Black rockfish (Sebastes schlegelii), a marine viviparous teleost, exhibits a prolonged testis quiescent phase lasting three-quarters of the year, with testis initiation occurring in September and maturation concluding in November and December. The mechanisms underlying these transitions are poorly characterized, leaving a critical gap in our knowledge of seasonal spermatogenesis and its regulation. Addressing this gap is crucial for advancing artificial breeding technologies, which could significantly benefit the aquaculture industry. RNA-seq was used to explore the gene regulatory networks involved in testis initiation in S. schlegelii. Transcriptomic analyses of brain and testis were conducted across key developmental phases. In the brain, upregulated genes were notably involved in neuroactive ligand–receptor interactions, whereas in the testis, differentially expressed genes were linked to cell cycle processes and ATP-dependent chromatin remodeling. Our findings reveal the molecular mechanisms underlying testis initiation in S. schlegelii, providing omics evidence for the role of the HPT axis in regulating this process. By elucidating the gene regulatory networks of the brain and testis during critical transitions, this study advances our understanding of spermatogenesis in seasonally breeding teleosts. These insights pave the way for developing year-round artificial breeding technologies, contributing to the sustainable management of commercially valuable fish species. Full article

Photobacterium damselae subsp. Piscicida (PDP), a marine bacterium, has been reported to infect a variety of economically important marine species worldwide. Understanding the occurrence and pathogenicity of PDP is crucial for effective disease control and ensuring the success of aquaculture operations. In late August 2023, an epidemic outbreak of P. damselae subsp. piscicida DQ-SS1, accompanied by significant mortality, was recorded in cage-cultured black rockfish (Sebastes schlegelii) located on Daqin Island for the first time. Genomic analysis revealed that DQ-SS1 possesses 2 chromosomes, with a total size of 4,510,445 bp and 3923 predicted CDSs. Pathogenic genes analysis identified 573 and 314 genes related to pathogen–host interactions and virulence, respectively. Additionally, DQ-SS1 displayed susceptibility to 15 antimicrobials, was resistant to 11 antimicrobials, and was intermediately sensitive to four antibiotics. Meanwhile, the in vitro assay revealed that the extracellular products (ECP) of DQ-SS1 were lethal to macrophages and exhibited hemolysin, lipase, and amylase activities. Moreover, DQ-SS1 also demonstrated the ability to survive in fish serum and resist complement-mediated killing. The in vivo assay showed that the infected fish exhibited severe histopathological alterations, such as the infiltration of inflammatory cells, cellular degeneration and necrosis, and loose cell aggregation. Lastly, the in vivo infection assays revealed the LD₅₀ of DQ-SS1 was 1.7 × 10³ CFU/g. This is the first study to elucidate the pathogenicity and genomic characteristics of multidrug-resistant PDP in cage-cultured S. schlegelii, which contributes to the advancement of diagnostic and preventative strategies for this disease in marine-cultured fishes and provides information for an in-depth study of the pathogenic mechanism of PDP. Full article

Bordetella trematum is a rare member of the genus Bordetella, primarily associated with human wound infections rather than respiratory diseases. The bacterium has been isolated from various clinical specimens, including ear inflammatory discharge, diabetic ulcers, and chronic wounds. The study aimed to characterize the genomes and antimicrobial resistance (AMR) profiles of B. trematum obtained from the fecal samples of asymptomatic highland eyelash pit vipers (Bothriechis schlegelii). The identification was conducted using MALDI-TOF mass spectrometry and biochemical tests. AMR was assessed using the microbroth dilution method, while whole-genome sequencing was performed on the Illumina NextSeq platform. The isolates displayed characteristic B. trematum biochemical features and demonstrated a resistance to cefotaxime, ciprofloxacin, and trimethoprim, while one also exhibited a resistance to ceftazidime. The whole-genome sequencing and comparison with limited public data revealed a high diversity within B. trematum, reaching >48,000 single nucleotide polymorphisms (SNPs), with 64 SNP differentiating tested snake isolates and thus, being considered epidemiologically unrelated. This is the first report of B. trematum isolated from an animal source in Europe. The findings provide valuable insights into this rare bacterium’s phenotypic and genomic characteristics, addressing an important knowledge gap in its ecology and AMR profile. Full article

Global fisheries face overfishing challenges, endangering fish stock and biodiversity. While hatchery release stocking programs aim to bolster fish populations, their effectiveness remains uncertain due to challenges in data acquisition, such as obtaining stocking details and differentiating between wild and stocked individuals. This study evaluates the stock status of black sea bream (Acanthopagrus schlegelii) released in Chinese hatchery programs since the 1980s. Samples from Zhanjiang fish markets (January 2019–October 2021) underwent analysis using the length–weight relationship (LWR), length-based spawning potential ratio (LBSPR), and length-based Bayesian (LBB) methods. The male and female LWRs were W = 0.0188L^2.9725 and W = 0.016L^3.0284, respectively, and the observed condition factors indicated good health. The estimates imply that the region is conducive to species survival and can sustain its stocking programs. The LBSPR (SPR = 0.21 (0.17–0.25)) and LBB (B/B_MSY = 1.1 (0.718–1.34), B/B₀ = 0.37 (0.253–0.473)) results suggest a rebuilding population capable of replenishing to more sustainable levels. However, F/M and net selectivity estimates indicate that fishing practices target juvenile fish, limiting the reproductive potential of A. schlegelii. These findings underline the need for enhanced management strategies, including delayed harvesting and the use of size-specific fishing gear, to ensure the long-term sustainability of the species. Full article

TGF-β1/Smads is a classic signaling pathway, which plays important roles in the development process of organisms. Black porgy Acanthopagrus schlegelii and red porgy Pagrus major are valuable economic fishes, and their hybrid offspring show excellent heterosis traits. Yet the molecular regulation mechanism of the heterosis traits is less clear. Here, we explored the TGF-β1/Smads pathway’s molecular genetic information for heterosis in A. schlegelii ♂ × P. major ♀ (AP) and A. schlegelii ♀ × P. major ♂ (PA) in terms of growth and development. The mRNA expression levels of TGF-β1, TβR-I, TβR-II, and Smad2 genes in different developmental stages of A. schlegelii were detected. Furthermore, the expression levels of TGF-β1, TβR-I, TβR-II, and Smad2 genes in different tissues of adult (mRNA level) and larva (mRNA and protein level) of A. schlegelii, P. major, and their hybrids were determined by both real-time quantitative PCR and Western blot techniques. The results indicated the ubiquitous expression of these genes in all developmental stages of A. schlegelii and in all tested tissues of A. schlegelii, P. major, and its hybrids. Among them, the mRNA of TGF-β1, TβR-I, and TβR-II genes is highly expressed in the liver, gill, kidney, and muscle of black porgy, red porgy, and their hybrid offspring. There are significant changes in gene and protein expression levels in hybrid offspring, which indirectly reflect hybrid advantage. In addition, there was no correlation between protein and mRNA expression levels of Smad2 protein. The results provide novel data for the differential expression of growth and development genes between the reciprocal hybridization generation of black porgy and red porgy and its parents, which is conducive to further explaining the molecular regulation mechanism of heterosis in the growth and development of hybrid porgy. Full article

This study was designed to evaluate the effects of yacon (Smallanthus sonchifolius) juice byproduct (YJB) on the growth performance, digestive and antioxidant enzyme activities, and disease resistance against Streptococcus iniae of juvenile black rockfish (Sebastes schlegelii) based on different feeding schedules. Four different YJB feeding strategies were evaluated: feeding the fish a basal diet continuously (control, T0), feeding them YJB (2.5 g/kg) continuously (T1), feeding them YJB for 1 day and the basal diet the next day (T2), and feeding them YJB for 1 day and the basal diet for the following 2 days (T3). No difference in survival among the treatments was found after the 8-week feeding trial (p > 0.05). However, the T1 and T2 groups exhibited significant enhancements in final body weight, weight gain, and specific growth rate compared with the T0 and T3 groups. Furthermore, the T1 and T2 groups showed a significant improvement in feed consumption, feed efficiency, and protein efficiency ratio compared with the T0 and T3 groups. No significant differences in the condition factor or viscerosomatic and hepatosomatic indices were observed among all the groups. Intestinal amylase, trypsin, and lipase activity was significantly (p < 0.05) higher in the T1 and T2 groups than in the T0 and T3 groups. Lysozyme, superoxide dismutase, and catalase activity along with glutathione peroxidase content were significantly (p < 0.05) higher under all YJB feeding regimens than those under the control treatment. The survival rates in all the YJB treatment groups after the S. iniae challenge were significantly (p < 0.05) enhanced. In conclusion, we recommend offering YJB at day-to-day intervals to improve growth performance, digestive enzyme activity, antioxidant status, and disease resistance against S. iniae. Full article

The study aimed to uncover the molecular response of juvenile Sebastes schlegelii to air exposure stress by identifying differentially expressed genes (DEGs) that may underlie their anti-stress mechanisms. Juvenile Sebastes schlegelii were subjected to varying durations of air exposure stress. The total RNA was extracted from whole tissues and sequenced using the Illumina NovaSeq 6000 platform. The transcriptome data were analyzed to identify DEGs through pairwise comparisons across a control group and two experimental groups exposed to air for 40 s and 2 min 30 s, respectively. The comparative DEG analysis revealed a significant number of transcripts responding to air exposure stress. Specifically, 5173 DEGs were identified in the 40 s exposure group (BS) compared to the control (BC), 6742 DEGs in the 2 min 30 s exposure group (BD) compared to the control (BC), and 2653 DEGs when comparing the BD to the BS group. Notably, Gene Ontology (GO) analysis showed an enrichment of DEGs associated with peptidase activity and extracellular regions, suggesting a role in the organism’s stress response. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis pointed to the involvement of metabolic pathways, which are crucial for energy management under stress. The upregulation of protein digestion and absorption pathways may indicate a physiological adaptation to nutrient scarcity during stress. Additionally, the identification of antibiotic biosynthesis pathways implies a potential role in combating stress-induced infections or damage. The identified DEGs and enriched pathways provide insights into the complex anti-stress response mechanisms in juvenile Sebastes schlegelii. The enrichment of peptidase activity and extracellular region-related genes may reflect the initiation of tissue repair and immune response following air exposure. The connection between protein digestion and absorption pathways and anti-stress capabilities could be interpreted as a metabolic readjustment to prioritize energy-efficient processes and nutrient assimilation during stress. The role of antibiotic biosynthesis pathways suggests a defensive mechanism against oxidative stress or microbial invasion that might occur with air exposure. Full article

It is widely known that all-female fish production holds economic value for aquaculture. Sebastes schlegelii, a preeminent economic species, exhibits a sex dimorphism, with females surpassing males in growth. In this regard, achieving all-female black rockfish production could significantly enhance breeding profitability. In this study, we utilized the widely used male sex-regulating hormone, 17α-methyltestosterone (MT) at three different concentrations (20, 40, and 60 ppm), to produce pseudomales of S. schlegelii for subsequent all-female offspring breeding. Long-term MT administration severely inhibits the growth of S. schlegelii, while short term had no significant impact. Histological analysis confirmed sex reversal at all MT concentrations; however, both medium and higher MT concentrations impaired testis development. MT also influenced sex steroid hormone levels in pseudomales, suppressing E2 while increasing T and 11-KT levels. In addition, a transcriptome analysis revealed that MT down-regulated ovarian-related genes (cyp19a1a and foxl2) while up-regulating male-related genes (amh) in pseudomales. Furthermore, MT modulated the TGF-β signaling and steroid hormone biosynthesis pathways, indicating its crucial role in S. schlegelii sex differentiation. Therefore, the current study provides a method for achieving sexual reversal using MT in S. schlegelii and offers an initial insight into the underlying mechanism of sexual reversal in this species. Full article

Sebastes schlegelii is one of the most commercially important marine fish in the northwestern Pacific. However, little information about the genome-wide genetic characteristics is available for S. schlegelii individuals from the Bohai and Yellow Seas. In this study, a total of 157,778, 174,480, and 188,756 single-nucleotide polymorphisms from Dalian (DL), Yantai (YT), and Qingdao (QD) coastal waters of China were, respectively, identified. Sixty samples (twenty samples per population) were clustered together, indicating shallow structures and close relationships with each other. The observed heterozygosity, expected heterozygosity, polymorphism information content, and nucleotide diversity ranged from 0.14316 to 0.17684, from 0.14035 to 0.17145, from 0.20672 to 0.24678, and from 7.63 × 10⁻⁶ to 8.77 × 10⁻⁶, respectively, indicating the slight difference in genetic diversity among S. schlegelii populations, and their general genetic diversity was lower compared to other marine fishes. The population divergence showed relatively low levels (from 0.01356 to 0.01678) between S. schlegelii populations. Dispersing along drifting seaweeds, as well as the ocean current that flows along the western and northern coasts of the Yellow Sea and southward along the eastern coast of China might be the major reasons for the weak genetic differentiation. These results form the basis of the population genetic characteristics of S. schlegelii based on GBS (Genotyping by Sequencing). In addition to basic population genetic information, our results provid a theoretical basis for further studies aimed at protecting and utilizing S. schlegelii resources. Full article

Establishing muscle lineage cell lines from fish will provide a great opportunity to study muscle development, which can eventually contribute to the improvement of the fish quality in the aquaculture industry. However, there has been a lack of the development of proper fish muscle lineage cell lines so far. Here, we report the establishment of a skeletal muscle-derived myogenic cell line from black sea bream (Acanthopagrus schlegelii). For this, we first attempted to find the optimal conditions for the primary explant culture of A. schlegelii muscle tissues and then established muscle-derived cell lines. After that, cell lines were characterized for their muscle-specific gene expression, growth, and myogenic differentiation. We found that the primary explant culture was effective when the tissue fragments were cultured in Dulbecco’s Modified Eagle Medium supplemented with fetal bovine serum and antibiotics on gelatin-coated dishes. Additionally, we confirmed that the addition of basic fibroblast growth factor was necessary to establish the cell lines. One of three cell lines established was capable of long-term culture, expressed three major myogenic regulatory genes including Pax7, MyoD, and Myog, and differentiated to myotubes in the condition using low concentration of horse serum, demonstrating that this cell line was a skeletal muscle-derived myogenic cell line. Full article

The climate crisis and growing petroleum demand have put the health of aquatic animals in jeopardy. Fish are sensitive to chemical pollutants in aquatic environments, such as polycyclic aromatic hydrocarbons, dioxins, and dibenzofurans. This study investigated the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and β-naphthoflavone (β-NF) exposure on histopathological and immunohistochemical features and expression patterns of cytochrome P450 1 (CYP1) family genes in black rockfish, Sebastes schlegelii. Histopathological alterations in the liver included congested central vein, sinusoidal dilatation, lymphocyte infiltration, and severe vacuolation within hepatocytes. The most prevalent alterations in TCDD-exposed kidneys were glomerular enlargement, narrowing of tubular lumen, melanomacrophage centers (MMCs), and necrosis. Moreover, CYP1A immunostaining was strong in renal tubules following TCDD exposure. All CYP1 family genes (CYP1A, CYP1B, CYP1C1, and CYP1C2) were significantly increased in the gills, liver, and kidney exposed to TCDD. Similarly, a significant increase of CYP1A mRNA expression in the kidney was observed upon exposure to TCDD (30.9-folds) and β-NF (25.5-folds) compared with that of the control group (p < 0.05). TCDD and β-NF exposure exerted more adverse effects on the kidney than the liver, and TCDD had a greater in vivo toxic effect than β-NF. The combined histopathological, immunohistochemical, and molecular alternations may be helpful for diagnosing chemical contaminant exposure in S. schlegelii. Full article