Search

Chemical communication through olfaction is crucial for fish behaviours, mediating in socio-sexual behaviours as reproduction. Turbot, a flatfish with significant aquaculture production, possesses a well-developed olfactory system from early developmental stages. After metamorphosis, flatfish acquire their characteristic bilateral asymmetry with an ocular side facing the open water column, housing the dorsal olfactory rosette, and a blind side in contact with the sea bottom where the ventral rosette is located. This study aimed to address the existing gap in specific histological, ultrastructural, lectin-histochemical and immunohistochemical studies of the turbot olfactory rosettes and olfactory bulbs. We examined microdissected olfactory organs of adult turbots and premetamorphic larvae by using routine histological staining techniques, and a wide array of lectins and primary antibodies against G-proteins and calcium-binding proteins. We observed no discernible structural variations in the olfactory epithelium between rosettes, except for the dorsal rosette being larger in size compared to the ventral rosette. Additionally, the use of transmission electron microscopy significantly improved the characterization of the adult olfactory epithelium, exhibiting high cell density, small cell size, and a wide diversity of cell types. Moreover, specific immunopositivity in sensory and non-sensory cells provided us of essential information regarding their olfactory roles. The results obtained significantly enriched the scarce morphological and neurochemical information available on the turbot olfactory system, revealing a highly complex olfactory epithelium with distinct features compared to other teleost species, especially with regard to olfactory cell distribution and immunolabelling patterns. [ABSTRACT FROM AUTHOR]

Fish growth and health are predominantly governed by dietary nutrient supply. Although the beneficial effects of omega-3 polyunsaturated fatty acids supplementation have been shown in a number of fish species, the underlying mechanisms are still mostly unknown. In this study, we conducted an investigation into the effects of EPA and DHA on cell proliferation, nutrient sensing signaling, and branched-chain amino acids (BCAA) transporting in primary turbot muscle cells. The findings revealed that EPA and DHA could stimulate cell proliferation, promote protein synthesis and inhibit protein degradation through activation of target of rapamycin (TOR) signaling pathway, a pivotal nutrient-sensing signaling cascade. While downregulating the expression of myogenin and myostatin, EPA and DHA increased the level of myogenic regulatory factors, such as myoD and follistatin. Furthermore, we observed a significant increase in the concentrations of intracellular BCAAs following treatment with EPA or DHA, accompanied by an upregulation of the associated amino acid transporters. Our study providing valuable insights into the mechanisms underlying the growth-promoting effects of omega-3 fatty acids in fish. [ABSTRACT FROM AUTHOR]

Clostridium autoethanogenum protein (CAP) is a promising protein source for aquaculture; however, how CAP influences fish quality is worth extensive research. We randomly allocated 630 turbot with initial body weights of about 180 g into 6 groups, with fishmeal-based control diet or diet with CAP replacing 15% (CAP15), 30% (CAP30), 45% (CAP45), 60% (CAP60), or 75% (CAP75) of fishmeal protein. After a 70-d feeding trial, the fillet yield (P = 0.015) and content of protein (P = 0.017), collagen (P 0.05). By contrast, the muscle hardness increased linearly with increasing CAP (P = 0.004), accompanied by linear reduction of muscle fiber area (P = 0.003) and expression of myogenesis-related genes, including cathepsin D (ctsd P

During embryonic development, vitamins are involved in energy metabolism and protein synthesis, while cathepsins and antioxidant defense play key roles in yolk degradation and protecting fish embryos from oxidative damage. This study aimed to investigate the consumption of vitamins (A, B1, B2, C, D, and E), ontogenesis of cathepsins, and antioxidant capacity in developing embryos of turbot. In this study, embryos were collected over time from 2.3 to 102.5 h (i.e., hatching) after fertilization for vitamins, cathepsins, and antioxidant capacity analyses. Results showed that the embryonic growth rate in the cleavage stage (CS) was faster than in other stages, while that in the segmentation stage (SS) was lower than in other stages. Embryos displayed higher demands on VA during blastula stage (BS), gastrula stage (GS), the early SS, and hatching day (HD), VB1 at CS; VB2 at BS, GS, SS, and HD; VD at CS and SS; VE at CS, BS, and the late SS; and Vc during entire periods. Cathepsins A (CA) showed a high level at early SS, suggesting its involvement in yolk degradation. Cathepsins B (CB) and cathepsins D (CD) were highly active at GS, suggesting an active apoptosis process. CA, CB, CD, and cathepsins L (CL) all kept low levels in CS, revealing low protein demand during the cleavage process. On the whole, the predominant antioxidant enzymes were superoxide dismutase (SOD) and malondialdehyde (MDA) from CS to SS; SOD, MDA, glutathione peroxidase (GSH-Px), and catalase (CAT) during SS; and GSH-Px and CAT during HD. In conclusion, the fastest growth rate and the slowest growth rate of embryos occurred in CS and SS, respectively, being consistent with energy allocation. Vitamin consumption and cathepsin ontogenesis were stage-specific. Oxidative damage on embryos was relatively less at CS, but larger at SS and HD. [ABSTRACT FROM AUTHOR]

Hsp40–Hsp70 typically function in concert as molecular chaperones, and their roles in post-infection immune responses are increasingly recognized. However, in the economically important fish species Scophthalmus maximus (turbot), there is still a lack in the systematic identification, interaction models, and binding site analysis of these proteins. Herein, 62 Hsp40 genes and 16 Hsp70 genes were identified in the turbot at a genome-wide level and were unevenly distributed on 22 chromosomes through chromosomal distribution analysis. Phylogenetic and syntenic analysis provided strong evidence in supporting the orthologies and paralogies of these HSPs. Protein–protein interaction and expression analysis was conducted to predict the expression profile after challenging with Aeromonas salmonicida. dnajb1b and hspa1a were found to have a co-expression trend under infection stresses. Molecular docking was performed using Auto-Dock Tool and PyMOL for this pair of chaperone proteins. It was discovered that in addition to the interaction sites in the J domain, the carboxyl-terminal domain of Hsp40 also plays a crucial role in its interaction with Hsp70. This is important for the mechanistic understanding of the Hsp40–Hsp70 chaperone system, providing a theoretical basis for turbot disease resistance breeding, and effective value for the prevention of certain diseases in turbot. [ABSTRACT FROM AUTHOR]

Objective: The waterless transport of live fish has changed the present situation of live‐fish transport. However, the waterless transport environment may cause stress in fish. This research evaluated the effect of tea polyphenol–trehalose (TPT) coating solutions on Turbot Scophthalmus maximus during waterless transport. Methods: After cold acclimation, Turbot were coated and subsequently transported in a waterless environment for 18 h. Physiological and biochemical parameters were measured, including lysozyme (LZM) and immunoglobulin M (IgM) activities, serum creatinine (Cr) and uric acid (UA) concentrations, and nutritional flavor. Result: The results showed that the nonspecific immunity of Turbot was inhibited during the waterless transport; the LZM activity first increased and then decreased, and the serum Cr and UA concentrations significantly increased. In addition, the waterless transport promoted the breakdown of Turbot flesh proteins, leading to changes in nucleotides and free amino acids (FAAs). After waterless transport, the LZM and IgM activities in the TPT‐treated Turbot were higher than those in the control group (CK), and the changes in FAA content and nucleotides were smaller than those observed in the CK group. Conclusion: This study shows that the use of TPT coating solution can reduce the impact of waterless transportation stress on the immune and metabolic functions of Turbot and can maintain the meat quality and flavor of Turbot. Impact statementWaterless transportation of live fish is considered as a green and economical solution to achieve high survival rates and quantity. In this article, we address a new method (coatings) to handle live Turbots in waterless transport, this method can reduce transportation stress and maintain the quality of Turbot. [ABSTRACT FROM AUTHOR]

Abstract Waterless transport is an alternative method for live aquatic products. However, the changes that occur in the fish body after transportation are not known. Herein, the effects of different transport methods on quality of turbot (Scophthalmus maximus) were investigated. Fish were divided into four groups: Group A (water, 17°C), Group B (waterless, 3°C), Group C (water, 3°C), and Group D (control, 17°C). In the case of 100% survival, the maximum transport time was 40 h for Group A, 55 h for Group B, and 90 h for Group C. Both crude protein and crude fat decreased significantly (p 40 h, regardless of the transport method.

The present work evaluated the effects of dietary fishmeal replacement with three non-food protein sources, including defatted Tenebrio molitor meal (TM), Clostridium autoethanogenum protein meal (CAP) and Chlorella vulgaris meal (CV), on the freshness traits of turbot Scophthalmus maximus. TM, CAP, or CV were used to respectively replace 0 %, 15 %, 30 %. 45 %, 60 % and 75 % of dietary fishmeal protein. Turbot (180.5 ± 2.5 g) were fed with eighteen experimental diets for 70 days, and were stored at 4 ℃ for 3 days. TM and CAP linearly increased QIM scores, but no obvious trend between QIM scores and CV dietary level. The TM15 diet decreased the QIM score, indicating better overall freshness compared to the other TM-groups. Chromameter indicated that consumers could not distinguish the color differences among groups (ΔE < 3). The muscle hardness of all groups was significantly reduced after storage (P30 %) resulted in increased pH, TVB-N, and TBA levels compared with the fish fed TM0 diet. But cathepsin B and L activities showed no significant differences across all TM-groups. Among the CAP-groups, no significant differences were noted in pH and TBA levels; however, CAP linearly increased TVB-N levels after storage. CV did not significantly influence the post-storage pH, TVB-N, and TBA levels. The muscle glycogen content showed no significant variance among the groups. In conclusion, a 15 % dietary replacement of fishmeal with TM optimized the freshness of turbot by decelerating muscle softening, lipid oxidation, and the production of volatile nitrogen compounds, whereas higher levels of TM accelerated these processes. CAP replacement level exceeding 15 % enhanced the production of volatile nitrogen compounds. Dietary inclusion of CV did not impact the freshness of turbot during storage.

In China, a novel pathogen within the genus Circovirus has been identified as a causative agent of the ‘novel acute hemorrhage syndrome’ (NAHS) in aquacultured populations of turbot (Scophthalmus maximus L.). Histopathological examination using light microscopy revealed extensive necrosis within the cardiac, splenic, and renal tissues of the afflicted fish. Utilizing transmission electron microscopy (TEM), we detected the presence of circovirus particles within the cytoplasm of these cells, with the virions consistently exhibiting a spherical morphology of 20–40 nm in diameter. TEM inspections confirmed the predominance of these virions in the heart, spleen, and kidney. Subsequent molecular characterization through polymerase chain reaction (PCR) analysis corroborated the TEM findings, with positive signals in the aforementioned tissues, in stark contrast to the lack of detection in gill, fin, liver, and intestinal tissues. The TEM observations, supported by PCR electrophoresis data, strongly suggest that the spleen and kidney are the primary targets of the viral infection. Further characterization using biophysical, biochemical assays, and genomic sequencing confirmed the viral classification within the genus Circovirus, resulting in the nomenclature of turbot circovirus (TurCV). The current research endeavors to shed light on the pathogenesis of this pathogen, offering insights into the infection mechanisms of TurCV in this novel piscine host, thereby contributing to the broader understanding of its impact on turbot health and aquaculture.

In this study, Saccharomycopsis fibuligera nucleotides (SFN) were extracted for exploring the influence on growth, inflammatory response and intestinal health level in turbot juveniles (initial weight 7.16 ± 0.01 g) for 10 weeks. Five isonitrogenous and isolipidic experimental feeds were formulated to include fishmeal-based diet (FM) that contained no SFN, while the other four soybean meal-based diet (SBM), that replaced 30 % FM, contained 0.25, 0.5 or 0.75 % SFN hereafter referred to as SBM0.25, SBM0.5 and SBM0.75, respectively. The feed efficiency exhibited a significantly quadratic or linear increase with the increase of SFN intake and the values reached the peak in the SBM0.5 treatment (P < 0.05). With the increase of SFN supplementation, the specific growth rate presented a significantly linear increase tendency (P < 0.05), and reached a peak in the SBM0.5 treatment. The hepatic antioxidant ability of turbot juveniles was significantly linear or quadratic promoted with dietary SFN supplementation in SBM-based diets (P < 0.05). Moreover, activities of plasma transaminases and γ-glutamyl transpeptidase of turbots showed significantly linear and quadratic decreasing trends with the SFN supplementation increasing (P < 0.05). The hepatic pro-inflammatory factor mRNA expressions were significantly linear or quadratic down-regulated and the anti-inflammatory factor mRNA expression was significantly linear and quadratic up-regulated with the SFN supplementation increasing (P < 0.05). Moreover, the height of villi and microvilli, the thickness of the muscularis and the tight junction proteins mRNA expression level exhibited significantly linear or quadratic increasing trends with the increasing dietary SFN supplementation (P < 0.05). The relative abundance of Lactobacillus plantarum of hindgut was significantly higher of fish fed the SBM0.75 diet compared with the SBM treatment. In conclusion, SFN supplementation was beneficial to the growth and health level of turbot juveniles, the appropriate amount of SFN supplemented was above 0.5 % in this study.

The Aeromonas salmonicida is responsible for causing furunculosis in various fish species. Furunculosis is a ubiquitous disease that affects the aquaculture industry and causes the mass mortality of turbot. Vibrio vulnificus is a pathogen that causes skin ulcers and hemorrhagic septicemia in fish, resulting in significant mortality in aquaculture. In this study, we have established a bivalent inactivated vaccine against A. salmonicida and V. vulnificus with Montanide™ ISA 763 AVG as an adjuvant. This bivalent inactivated vaccine was used to immunize turbot by intraperitoneal injection, and the relevant immune indexes were detected. The results demonstrate that the bivalent inactivated vaccine exhibited a relative percent survival (RPS) of 77% following A. salmonicida and V. vulnificus intraperitoneal challenge. The vaccinated group exhibited higher levels of acid phosphatase activity and lysozyme activity compared to the control group. ELISA results showed a significant increase in serum antibody levels in immunized turbot, which was positively correlated with immunity. In the kidney tissue, related immune genes (TLR5, CD4, MHCI and MHCII) were up-regulated significantly, showing that the vaccine can induce cellular and humoral immune responses in turbot. In conclusion, the bivalent inactivated vaccine against A. salmonicida and V. vulnificus was immunogenic, efficiently preventing turbot from infection, which has the potential to be applied in aquaculture. [ABSTRACT FROM AUTHOR]

A ten-week feeding trial was conducted to investigate the effect of dietary niacin on intestinal health of juvenile turbot. Three isonitrogenous and isolipidic experimental diets were formulated, containing 0 (NA0, as control), 20 (NA20), and 80 (NA80) mg/kg niacin, respectively. Compared with the NA0 group, dietary 20 mg/kg niacin significantly reduced the gene expression of NF-κB and pro-inflammatory cytokines (TNF-α, IFN-γ and IL-8), and increased the expression of TGF-β. Furthermore, dietary niacin at 20 mg/kg significantly decreased the gene expression of Caspase-9 and tumor suppressor p53, and increased the ratio of Bcl-2/Bax. Sequencing of intestinal bacterial 16 S rRNA V4 region revealed that dietary 20 mg/kg niacin significantly up-regulated the abundance of lactic acid bacteria (Lactobacillus, Streptococcus, Lactococcus, Leuconostoc and Enterococcus) and Anoxybacillus, and optimized the composition of intestinal bacterial community. However, diet NA80 increased the relative abundance of opportunistic pathogen Vibrio and Pseudomonas. Collectively, dietary niacin at 20 mg/kg is beneficial to gut health of juvenile turbot, however, excessive addition of niacin (80 mg/kg) showed negative effect on intestinal microbial communities.

Objective: Investigating the effects of farming region and commercial size on the nutrition and flavor quality of Scophthalmus maximus. Methods: Farming turbot of three regions, namely, Rushan, Haiyang and Suizhong, and two typical commercially available sizes, 450~750 and 750~1 250 g, were selected for this study to compare their nutrient composition and flavor substances. Used principal component analysis and orthogonal partial least squares discriminant analysis to visualize the differences between different groups and to identify the nutritional indicators in differentiate farming region and commercial size. Results: The protein and collagen content of turbot in the Rushan and Haiyang regions were significantly higher than those in the Suizhong region, and the DHA content of the large-size group in Suizhong accounted for 20.97% of the total fatty acid content, which was significantly higher than that of other groups. The muscle bitterness, saltiness and sweetness of turbot in the Suizhong area were significantly higher than those in the Rushan and Haiyang regions, and there were more volatile compounds in the Haiyang region, followed by the Rushan region and the Suizhong region. As for the commercial sizes, the collagen content of the large-size group was significantly higher than that of the small-size group. The volatile substances with higher content in the small-size group included 3-methylbutanal and propan-2-ol, etc., while the volatile substances with higher content in the large-size group included 2-methyl-1-propanol, 2-pinene and tetrahydrofuran, etc. Conclusion: Five indicators of fat, collagen, moisture content, total unsaturated fatty acids and ash were obtained based on the orthogonal partial least squares discriminant analysis to differentiate turbot from different farming regions, and to provide basic data for the evaluation of nutrition and flavor quality of farmed turbot.

Germ cell transplantation (GCT) is a promising biotechnology that enables the production of donor-derived gametes in surrogate recipients. It plays a crucial role in the protection of endangered species, the propagation of elite species with desired traits, and long-term preservation of genetic resources. This significance is particularly pronounced when GCT is synergistically employed with cryopreservation techniques. However, GCT often encounters challenges due to low colonization rates and, in some cases, complete loss of donor cells in recipients. Glial cell line-derived neurotrophic factor (GDNF) plays a pivotal role in sustaining the self-renewal of spermatogonial stem cells (SSCs) in mammals. Additionally, it has been shown to promote the proliferation of spermatogonia in vitro cultures in certain animal species. In turbot (Scophthalmus maximus), we found that the expressions of gdnf and gfrα1a were predominantly observed in spermatogonia rather than somatic cells, which differed from their expression patterns in mammals. The efficiency of exogenous spermatogonia transplantation in Japanese flounder (Paralichthys olivaceus) larvae could be substantially enhanced by incubating donor cells from turbot with 100 ng/ml GDNF prior to transplantation. This led to a noteworthy increase in the colonization rate, rising from 33%-50%–61.5%. Additionally, the addition of 20 ng/ml GDNF in cell medium could also promote the proliferation of turbot germ cells in vitro. These results demonstrated the gdnf in turbot testis expression characteristics and suggested that addition of GNDF could be an effective way to improve the GCT efficiency and promote the germ cells expansion during in vitro culture. • Expression patterns of gdnf and gfrα1a in turbot reveal preferential localization in spermatogonia, distinct from mammas. • GDNF incubation significantly enhances exogenous spermatogonia transplantation efficiency in Japanese flounder larvae. • GDNF addition boosts turbot germ cell proliferation in culture, hinting its potential to enhance germ cell expansion in vitro. [ABSTRACT FROM AUTHOR]

Reproduction is subtlety regulated by the hypothalamic-pituitary-gonad (HPG) axis in vertebrates. Pituitary gland is the center of the HPG axis, while pituitary gonadotropins follicle stimulating hormone (FSH) and luteinizing hormone (LH) were identified the key elements of the HPG axis in teleost and mammal. Morphology, cell lines, and gonadotropins cell localization of female turbot and mouse pituitary were determined at mature stage to illustrate the anatomical difference and cell characteristics in this study. Results show that turbot pituitary is chicken heart-shaped, dorsoventral, located on the ventral surface of the diencephalon. The mouse pituitary is oval, located in the pituitary fossa of the sella turcica at the skull base. Two well-distinguished areas adenohypophysis (AH) and neurohypophysis (NH) in pituitary were identified in turbot and mouse. Turbot AH comprised the rostral pars distalis (RPD), proximal pars distalis (PPD), and pars intermedia (PI). NH was not pronounced and with finger-like protrusions into PPD. However, mouse AH only comprised the pars distalis (PD) and PI. NH distribution was semicircular. Three main types of cells (acidophilic, basophilic, and chromophobic cells) were distributed in the mouse PD region, whereas appeared in the turbot PPD, RPD, and PI. Moreover, the percentage of mouse chromophobic and basophilic cells was higher and lower than that of turbot, respectively. The diameter of the aforementioned three cells in the mouse was significantly higher than turbot. fshβ- and lhβ-immunoreactive signals were identified in turbot-distinct pituitary cells that primarily occupied the peripheral and central regions of AH. However, mouse fsh- and lh-immunoreactive cells were expressed in the same cells and present in the PD. These results demonstrate the significantly difference of pituitary morphology, cell lines and gonadotropins (fshβ and lhβ) location in female turbot and mouse. These differences help for fully understand the evolution and endocrinological functions of pituitary. [ABSTRACT FROM AUTHOR]

The development of host-derived probiotics offers an alternative nutritional strategy for aquaculture. Turbot (Scophthalmus maximus L.) is an important cultured fish in the world. However, research on its host-associated probiotics is limited. The present study evaluates the probiotic potential of Bacillus velezensis T20 (T20) isolated from the intestine of turbot. In the experiment, turbots were fed with two diets: the control diet (CON) and CON supplemented with 1 × 108 CFU/g T20 for 8 weeks. Results showed that the addition of T20 did not affect the growth performance of turbot, but significantly decreased the mortality of turbot challenged by Edwardsiella tarda. Moreover, T20 could survive in the intestine of turbot, it might contribute to the improved intestinal antioxidant capacity, physical barrier and digestive enzymes activities of turbot. In terms of intestinal microbiota, T20 modulated intestinal microbiota communities. Specifically, T20 increased the relative abundances of Bacillus and B. velezensis in both intestinal mucosa and digesta, and decreased potential pathogen such as Mycoplasma, Staphylococcus and Weissella in intestinal digesta. In conclusion, the present study showed that dietary B. velezensis T20 could enhance the disease resistance, improve the communities of intestinal microbiota and promote the intestinal health of turbot.

Hsp40–Hsp70 typically function in concert as molecular chaperones, and their roles in post-infection immune responses are increasingly recognized. However, in the economically important fish species Scophthalmus maximus (turbot), there is still a lack in the systematic identification, interaction models, and binding site analysis of these proteins. Herein, 62 Hsp40 genes and 16 Hsp70 genes were identified in the turbot at a genome-wide level and were unevenly distributed on 22 chromosomes through chromosomal distribution analysis. Phylogenetic and syntenic analysis provided strong evidence in supporting the orthologies and paralogies of these HSPs. Protein–protein interaction and expression analysis was conducted to predict the expression profile after challenging with Aeromonas salmonicida. dnajb1b and hspa1a were found to have a co-expression trend under infection stresses. Molecular docking was performed using Auto-Dock Tool and PyMOL for this pair of chaperone proteins. It was discovered that in addition to the interaction sites in the J domain, the carboxyl-terminal domain of Hsp40 also plays a crucial role in its interaction with Hsp70. This is important for the mechanistic understanding of the Hsp40–Hsp70 chaperone system, providing a theoretical basis for turbot disease resistance breeding, and effective value for the prevention of certain diseases in turbot.

The feed conversion rate (FCR) is a crucial economic trait in aquaculture fish, as feed costs account for the vast majority of aquaculture costs. Given the importance of this trait, there have little efforts to unravel the genomic architecture of FCR and identify key genes or genomic regions useful as selection makers. This situation may stem from the inherent swimming behavior of fish, which presents challenges in obtaining individual FCRs. In this work, we developed a specialized small cage culture system. Through this system, the Feed Conversion Ratio (FCR) of 300 individuals was successfully determined, marking the first successful determination of individual FCRs for turbot. The results revealed a range of FCR values from 35.3% to 192.6%, with an average of 126.5% ± 23.5%. On this basis, a genome-wide association study (GWAS) was conducted to identify single nucleotide polymorphisms (SNP) associated with FCR. A total of 2613,115 SNPs on 22 chromosomes were selected for GWAS analysis by Efficient Mixed-Model Association eXpedited (EMMAX) software. A linear mixed model was employed to test the association between each SNP and FCR, considering population structure and genetic relatedness among individuals. Two significant SNPs on Chr6 were identified to be correlated with FCR. According to their localization in genome, four candidate genes were identified on Chr6, including uncharacterized protein KIAA1755, Kinesin Family Member 21B (KIF21B), Discs large homolog-associated protein 4B (DLGAP4B), and Copine 5B (CPNE5B), all of which are closely located in the genome and exhibit significant functional similarities. Our results will facilitate the implementation of marker-assisted selection in breeding programs and serve as a foundation for future research in this area.

The mass production of triploid turbot Scophthalmus maximus is expected to enhance the economic benefits of aquaculture due to its sterility, growth, and survival advantages. Among the methods for inducing triploidy in teleost, pressure shock has been considered a more consistent and reliable approach. In this study, the optimal parameters for inducing triploidy in turbot through hydrostatic pressure shock were investigated in a series of trials, including the intensity (55–75 MPa), timing (3.5–8.5 min after fertilization, maf) and duration (4–12 min). The ploidy level was determined by flow cytometry analysis. Under a water temperature of 14.5 ± 0.5 °C, treatment optima for pressure shock were determined to be 4.5–5.5 maf with 60 MPa for 6 min, resulting in 100% triploidy rate. A comparison of induction efficiency between pressure shock using this combination and cold shock initiated at 6.5 maf in −2 °C sea water for 25 min was carried out using eggs from three females. The higher hatching rates and triploidy rates, and lower abnormality rates were investigated with pressure shock treatment compared with cold shock treatment. The optimized parameters were successfully applied to three large batches of eggs (∼ 250, 300 and 330 mL) for mass production of triploid turbot. The total length and body weight of triploids were significantly lower than those of diploid counterparts at 2 months after hatching (mah), however, they exhibited a significant increase at 8 and 11 mah, respectively, and maintained this higher level thereafter. Additionally, the survival rates remained similar from 2 to 12 mah. The results of this preliminary study indicate that pressure shock rather than cold shock is more beneficial for the commercial production of triploid turbot under farming conditions.

The present study examined the genetic diversity and spatial distribution of turbot (Scophthalmus maximus), an economically important species on the Bulgarian Black Sea coast. Maximum entropy (MaxEnt) modeling software Version 3.4.4. was utilized to develop a habitat suitability model for S. maximus in the Bulgarian Black Sea region. Data collected via demersal and pelagic surveys and genetic sampling from 2017 to 2021 were utilized to link species occurrence localities with selected abiotic factors. Our findings showed that the species' habitat preferences are strongly influenced by temperature and dissolved oxygen, and projections based on simplified climatic scenarios indicated potential distribution shifts and a substantial reduction in reproduction habitats in the northern region. The assessment of genetic diversity was based on mtDNA COIII sequencing; MtDNA revealed a low level of polymorphism in all analyzed populations. The extensive fishing pressure may have increased the likelihood of genetic and population bottlenecks and a consequent decline in genetic diversity in the Shabla, Nesebar, and Tsarevo populations. The Tajima's D values for the latter indicated that turbot underwent a bottleneck followed by rapid population expansion. Our findings are essential for the conservation and effective management of S. maximus stocks in the region. [ABSTRACT FROM AUTHOR]

Ovarian fluid is essential for successful fertilization by maintaining the viability, motility, and velocity of sperm. The organic compounds and inorganic ions in ovarian fluid significantly influence spermatozoa's motility, velocity, and longevity. However, the effect of ovarian fluid on sperm performance is limited in teleost fish. In this study, the effect of ovarian fluid on sperm performance and its components in external fertilization species (Scophthalmus maximus , turbot) and internal fertilization species (Sebastes schlegelii , black rockfish) was investigated using computer-assisted sperm analysis, high-performance liquid chromatography, and metabolome analysis. The ovarian fluid had a distinct and species-specific effect on both species. In the black rockfish, the ovarian fluid from turbot significantly increased sperm motility (74.07% ± 4.09%), as well as VCL (45 ± 1.67 μm/s), VAP (40.17 ± 1.6 μm/s), and VSL (36.67 ± 1.86 μm/s), and longevity (352 ± 11.31 min) (P < 0.05). In the turbot, only the longevity (71.33 ± 5.69 min) and fertilization rate (65.27% ± 11.59%) showed significantly improvement (P < 0.05). The ovarian fluid was rich in organic compounds, suggesting enrichment in the glycolysis/gluconeogenesis pathways. The results suggest that glycometabolism plays a crucial role in improving sperm performance in teleost with internal fertilization. Thus, incorporating ovarian fluid into the sperm activation medium can enhance artificial fertilization in fish breeding. • Ovarian fluid has different effect in turbot and black rockfish. • Ovarian fluid enhanced sperm motility in black rockfish. • Ovarian fluid significantly prolonged sperm longevity in turbot and black rockfish. • Ovarian fluid may provide energy for sperm survival and extended longevity. [ABSTRACT FROM AUTHOR]

The Aeromonas salmonicida is responsible for causing furunculosis in various fish species. Furunculosis is a ubiquitous disease that affects the aquaculture industry and causes the mass mortality of turbot. Vibrio vulnificus is a pathogen that causes skin ulcers and hemorrhagic septicemia in fish, resulting in significant mortality in aquaculture. In this study, we have established a bivalent inactivated vaccine against A. salmonicida and V. vulnificus with Montanide™ ISA 763 AVG as an adjuvant. This bivalent inactivated vaccine was used to immunize turbot by intraperitoneal injection, and the relevant immune indexes were detected. The results demonstrate that the bivalent inactivated vaccine exhibited a relative percent survival (RPS) of 77% following A. salmonicida and V. vulnificus intraperitoneal challenge. The vaccinated group exhibited higher levels of acid phosphatase activity and lysozyme activity compared to the control group. ELISA results showed a significant increase in serum antibody levels in immunized turbot, which was positively correlated with immunity. In the kidney tissue, related immune genes (TLR5, CD4, MHCI and MHCII) were up-regulated significantly, showing that the vaccine can induce cellular and humoral immune responses in turbot. In conclusion, the bivalent inactivated vaccine against A. salmonicida and V. vulnificus was immunogenic, efficiently preventing turbot from infection, which has the potential to be applied in aquaculture.

The development and maturation of sperm entails intricate metabolic processes involving water molecules, amino acids, hormones, and various substances. Among these processes, the role of aquaporins (aqps) in the testis is crucial. Turbot (Scophthalmus maximus) is a significant marine flatfish species in China; however, natural egg laying in females is not feasible under cultured conditions. Consequently, artificial insemination becomes necessary, requiring the retrieval of sperm and eggs through artificial methods. In this study, we combined genomic, transcriptomics, RT-qPCR, computer-assisted sperm analysis (CASA), and immunohistochemistry to investigate the involvement of the aqp family in spermatogenesis in turbot. Through genomic data analysis, we identified 16 aqps genes dispersed across 13 chromosomes, each exhibiting the characteristic major intrinsic protein (MIP) domain associated with AQPs. The results from RNA-seq and RT-qPCR analysis revealed prominent expression of aqp4, 10, and 12 during the proliferative stage, whereas aqp1 showed primary expression during the mature stage. aqp11 displayed high expression levels during both MSII and MSV stages, potentially contributing significantly to the proliferation and maturation of male germ cells. Conversely, aqp8 showed elevated expression levels during the MSIII, MSIII-IV, and MSIV stages, suggesting its direct involvement in spermiogenesis. Immunohistochemical analysis unveiled the predominant localization of AQP1 protein in male germ cells rather than Sertoli cells, specifically concentrated in the head of sperm within cysts. Furthermore, a noteworthy decline in sperm motility was observed when sperm were subjected to treatment with either the AQP1-specific inhibitor (HgCl2) or the AQP1 antibody. However, no direct correlation was found between the expression of Smaqp1 and sperm quality. Overall, these findings provide new insights into the involvement of aqps in teleost spermatogenesis. Moreover, they hold potential for improving techniques related to sperm activation and cryopreservation, offering valuable knowledge for future advancements in this field. [ABSTRACT FROM AUTHOR]

The health of aquatic organisms can be affected due to anthropogenic activities and limited actions to reduce the pollution of the Black Sea. The accumulation of organic pollutants (OPs) in the aquatic environment occurs in water, sediment, and then biota. The turbot (Scophthalmus maeoticus) is a benthic fish of commercial interest scarcely studied in the Black Sea region, and none of the studies researched OP concentrations in its main tissues. In this paper, polycyclic aromatic hydrocarbons (PAHs) and POPs, organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were determined in water, sediment, and turbot muscles, gills, gonads, and livers, to research their accumulation level. The determinations were made with gas chromatography on turbots sampled in 2021 from the Romanian Black Sea waters. OCPs—p,p'DDT and its metabolites p,p'DDE, p,p'DDD—are dominant in the turbot tissues. From PAHs, benzo(g,h, i)perylene was the dominant compound, while for PCBs it was PCB 52. The OPs' presence in the wild turbot is due to river input, dredging and coastal rehabilitation works, industrial activities and contaminated food and poses a risk to human health due to the exceeding maximum allowable concentration for human consumption in Romania and the European Union. [ABSTRACT FROM AUTHOR]

Acidic digestion is an important digestive process of marine fish. In fish stomach, two enzymes are involved in the secretion of hydrochloric acid (HCl) and proteomic digestion: H+/K+-ATPase and pepsinogen. However, the starting of digestive function in fish is still unclear. To reveal the details of acidic digestion of turbot Scophthalmus maximus in early development, a 40 day of turbot larvae culture was conducted. The H+/K+-ATPase gene from the turbot S. maximus (smH+/K+-ATPase) was identified and characterized. Based on our previous discription on pepsinogen of turbot S. maximus, we combined pepsinogen and H+/K+-ATPase and analyzed the mechanism of acidic digestion in turbot. Results show that the spatial and temporal expression profiles of H+/K+-ATPase agreed with pepsinogen A and C in turbot, indicating a synergetic action between H+/K+-ATPase and pepsinogen during the acidic digestion process. In addition, the turbot juveniles showed a faster growth after the expressions of H+/K+-ATPase gene and pepsinogen gene, demonstrating that pepsin had a higher digestive efficiency, for which a compound diet should be provided to the fish from Day 22 onward. This study provided a reference for biology research and aquaculture of turbot and other marine fishes. [ABSTRACT FROM AUTHOR]

Lepeophtheirus salmonis was collected from the Atlantic salmon, Salmo salar, in Turkey. It is known as the salmon louse. It was obtained from fish samples that were farmed in Norway and imported to Turkey. Although it has not been proven that the salmon louse carries zoonotic or any pathogens, attention should be paid to biosecurity measures and hygiene rules in product trade among countries. This study demonstrates that the fish louse, even dead, travels between countries. In addition, Lepeophtheirus europaensis was collected from the turbot and the brill during the project to monitor demersal fish from Turkey. L. europaensis was diagnosed on wild fish in this study; it is important to know the diversity of parasites in terms of taking precautions against possible future diseases, since the farming of these fish is carried out in Turkey. L. europaensis was also reported for the first time on turbot and brill in Turkey. [ABSTRACT FROM AUTHOR]

A continuous intestine cell line from turbot (Scophthalmus maximus) designated as SMI was established utilizing the tissue explant technique. Primary SMI cell was cultured at 24 °C in a medium with 20% fetal bovine serum (FBS), then subcultured in 10% FBS after 10 passages. Impacts of medium or temperature on the growth of SMI were examined and the results indicated it grew well in DMEM supplemented with 10% FBS at 24 °C. The SMI cell line was subcultured more than 60 times. Karyotyping, chromosome number, and ribosomal RNA genotyping analysis revealed that SMI had a modal diploid chromosome number of 44 and originated from turbot. After being transfected with pEGFP-N1 and FAM-siRNA, a large number of green fluorescence signals were observed in SMI, indicating that SMI could be used as an ideal platform to explore gene function in vitro. In addition, the expression of epithelium-associated genes such as itga6, itgb4, gja1, claudin1, zo-1, and E-cadherin in SMI suggested the SMI had some characteristics of epidermal cells. The upregulation of immune-associated genes such as TNF-β, NF-κB, and IL-1β in SMI after stimulation with pathogen-associated molecular patterns suggested the SMI might exhibit immune functions similar to the intestinal epithelium in vivo. [ABSTRACT FROM AUTHOR]

This eight-week feeding trial was conducted to investigate whether adding yeast cell wall extract mixed with bacteria producing mycotoxin-degrading enzymes (YEMDE) to an aflatoxin B1 (AFB1)-contaminated diet affects the growth performance, liver health, antioxidant status, and intestinal microbiota status of juvenile turbot. A total of 480 fish were divided into four groups (three replicate tanks each group): basal diet (Control); Control diet supplemented with 100 μg/kg AFB1 (AFB1); and AFB1 supplemented with 500 mg/kg or 1000 mg/kg YEMDE (AFY500 and AFY1000, respectively). The results showed that a minor variation in growth performance was observed among all groups (P > 0.05). Compared to the Control diet, the AFB1 diet significantly deceased the activities of triglyceride and catalase in the serum (P

In vertebrates, bony fishes possess not only innate immune cells but also T and B cells that are equivalent to those in mammals. However, the precise sub-cluster of immune cells in teleost fish remains largely unknown. Herein, we developed a dynamic bacterial infection model in turbot (Scophthalmus maximus) and created a fish immune cell landscape (FICL) for a primary lymphoid organ (head kidney), a secondary lymphoid organ (spleen), and barrier tissues (gills and posterior intestine). Moreover, through comprehensive characterization of the expression profiles of 16 clusters, including dendritic cells-like (DCs-like), macrophages (MΦs), neutrophils, NK cells, as well as 12 sub-clusters of T and B cells, we found that CD8+ CTLs, CD4−CD8− T, Th17 and ILC3-2 like cells possess a bifunctional role associated with cytotoxicity and immunoregulation during bacterial infection. To our knowledge, these results could provide a useful resource for a better understanding of immune cells in teleost fish and could act as a comprehensive knowledge base for assessing the evolutionary mechanism of adaptive immunity in vertebrates.

Purpose. The development of marine aquaculture in the Black Sea is relevant and promising for many reasons, as stated in the decisions and documents of national organizations in the region and the General Fisheries Commission for the Mediterranean (GFCM). Turbot is one of the most valuable fish marketed in seaside countries of the Black Sea as well as in the European Union. Various aspects of the biology of turbot have been investigated yet.Butunfortunately, surveillance procedures for listed diseasesandanalysis of the possibility its prevention and spread have not been provided. Therefore, in this study, in order to evaluate the data on viral diseases of turbot in Ukraine, in 2020 a field survey in free-living Black Sea turbot (Scophthalmus maeoticus) in the northern parts of Black Sea and Sea of Azov was carried out. Methodology. Before sampling all fish were observed for the external lesions, measured from snout to tail length and of total length and weight. Sampling included pooled internal organs, gills and brain. Cell culture and polymerase chain reaction (PCR) methods were used to identify viral diseases. Findings. An external fish examination did not reveal any sign of disease. The internal organs, as well as the gills, were in good condition and had appropriate color, shape and without any pathological changes. All tested samples were free of IPNV, VHSV and VNN viruses as was determined by the methods of cell culture and PCR. The cytopathic effect (CPE) on cells was not observed after the first and the second blind passages. Using the RT-PCR method, we did not identify any of the viruses we were looking for. Originality. This was the first attempt to screen turbot viral diseases in the Ukrainian waters of the Black and Azov Seas. Practical value. In future the permanent surveillance of viral diseases in turbotin accordance with the EU strategy on animal health allows to prevent the outbreaks and develop new approaches for the diagnostic tests in purpose to study the ecology of pathogens in different areas.

The Black Sea Turbot (BST) is one of the most valuable fish species exploited within the fisheries activities conducted in the Black Sea, due to market demand and high selling prices. However, due to the anthropogenic pressure exercised on the Black Sea, BST is prone to accumulate different contaminants such as heavy metals. The risk of heavy metals transfer to the human consumer, through fish consumption, is possible. Thus, constant evaluation of the biomass is needed in order to avoid consumer intoxication. It is well known that different metals manifest competing behaviour for binding spots when accumulating in biota. Therefore, the present study aims to evaluate the concentration of macro- (Ca, Mg, K, Na) and micro-elements (Fe, Zn, Cu, Ni, Cr, Mn, Co, Cd, Pb) in BST muscle tissue collected from the Romanian Black Sea sector and to determine the correlation relationship between them (Pearson coefficient). The following accumulation trend in BST muscle was identified: Na>K>Ca>Mg>Zn>Fe>Cu>Mn>Ni>Cd>Pb>Cr>Co. [ABSTRACT FROM AUTHOR]

The impacts of dietary supplementation with graded levels of Sophora flavescens root extract (SFE) on growth performance, antioxidant capacity, immune status, and resistance against Edwardsiella tarda challenge in Scophthalus maximus were investigated in this study. In all, 600 turbot (initial body weight: 8.38 ± 0.07 g) were randomly distributed in 12 tanks with 50 fish per tank and fed four experimental diets supplemented with 0, 0.05%, 0.1%, or 0.2% SFE (named as: SFE0, SFE0.05, SFE0.1, and SFE0.2, respectively), for 56 days. The results showed that 0.1% and 0.2% SFE supplementation have significantly increased the FBW, WGR, SGR, and PER of turbot, while decreased the FCR of turbot (p < 0.05). Dietary SFE supplementations have significantly increased the activities of plasma SOD, CAT, GPx, T-AOC, GST and LZM, decreased plasma MDA contents in turbot under normal or challenge condition (p < 0.05). Meanwhile, SFE addition dramatically enhanced the hepatic mRNA expression of antioxidant parameters (including Nrf2, Keap1, SOD, CAT, Trx2, GST and GR) during the normal condition. mRNA levels of NF-κB p65, IκBα, TNF-α, TGF-β, and IL-10 in the liver of fish were notably up-regulated by SFE treatment during normal condition (p < 0.05), while the transcription of IL-1β was down-regulated by SFE whenever under normal or challenge condition. 0.1% and 0.2% SFE administration have significantly increased the survival rate of turbot against E. tarda challenge (p < 0.05). In conclusion, dietary SFE supplementation improved the growth performance, antioxidant activity and disease resistance of turbot, and SFE could be a potential feed additive for turbot. [ABSTRACT FROM AUTHOR]

Fish vaccination plays a vital role in the prevention of fish diseases. Inappropriate injection positions will cause a low immunization rate and even death. Currently, traditional visual algorithms have poor robustness and low accuracy due to the specificity of the placement of turbot fins in the application of automatic vaccination machines. To address this problem, we propose a new method for estimating the injection position of the turbot based on semantic segmentation. Many semantic segmentation networks were used to extract the background, fish body, pectoral fin, and caudal fin. In the subsequent step, the segmentations obtained from the best network were used for calculating body length (BL) and body width (BW). These parameters were employed for estimating the injection position. The proposed Atten-Deeplabv3+ achieved the best segmentation results for intersection over union (IoU) on the test set, with 99.3, 96.5, 85.8, and 91.7 percent for background, fish body, pectoral fin, and caudal fin, respectively. On this basis, the estimation error of the injection position was 0.2 mm–4.4 mm, which is almost within the allowable injection area. In conclusion, the devised method was able to correctly differentiate the fish body from the background and fins, meaning that the extracted area could be successfully used for the estimation of injection position. [ABSTRACT FROM AUTHOR]

Long noncoding RNAs (lncRNAs), can regulate mRNA by targeting miRNA in a competing endogenous RNA network, have become a hot topic in the research of fish immune mechanism recent years. While in turbot (Scophthalmus maximus L.), an economically important marine fish, there are limited researches about the role of lncRNAs in its immune response to bacterial infection. In this study, a total of 184 differentially expressed lncRNAs (DElncRNAs) were systematically identified and characterized using whole-transcriptome sequencing of the liver of turbot challenged with Vibrio anguillarum at 0 h (control) and three different time points post infection (2 h, 12 h and 24 h, respectively). Subsequently, GO and KEGG signaling pathways of differentially expressed lncRNAs were analyzed to predict their function. We found that lncRNAs in our results were significantly enriched in several immune-related signaling pathways, including the NOD-like receptor signaling pathway, Toll-like receptor signaling pathway, Cytokine-cytokine receptor, MAPK signaling pathway, phagosome, PPAR signaling pathway and the regulation of autophagy. In addition, a total of 492 DE lncRNA - DE miRNA -DE mRNA networks were identified at three different time points post infection, which were consisted of 102 networks at 2 h, 122 networks at 12 h and 81 networks at 24 h post infection, respectively. Noticeably, 92 of these regulated networks were immune-related. These observations suggested that lncRNAs can regulate the expression of immune-related genes in the response to bacterial infection in turbot. Moreover, our findings would provide a new insight into the immune response of turbot to pathogen infection and lay a foundation for future study. • A total of 184 differentially expressed lncRNAs (DElncRNAs) were systematically characterized of the liver of turbot challenged with V. anguillarum. • lncRNAs participate in immune-related signaling pathways, including the NOD-like receptor signaling pathway, Toll-like receptor signaling pathway. • A total of 492 DE lncRNA - DE miRNA -DE mRNA networks were identified; 92 of which were immune-related. [ABSTRACT FROM AUTHOR]

The brain plays a critical role in controlling reproduction through the hypothalamus-pituitary-gonadal (HPG) axis in vertebrates. Turbot (Scophthalmus maximus) has become an economically important marine fish in Europe and North China. Previous research investigating turbot reproduction has focused on the role of the HPG axis in regulating egg and sperm production. However, the morphology and histology of the organs in the HPG axis have not been studied. In this study, we investigated the morphology and histology of brains in female and male turbot at different stages of gonadal development. The results showed that the brains of both female and male turbot were composed of seven parts that are typical of advanced teleosts: the telencephalon, diencephalon, cerebellum, hypothalamus, pituitary gland, myelencephalon, and olfactory bulbs. The telencephalon was well-developed and contained five distinct lobes, with the contiguous diencephalon at the caudal portion. The torus longitudinales and rostral torus semicircularis of the mesencephalon flattened along the dorsal surface, and the rostral corpus cerebellum was located in the dorsal portion. The actual total brain volume in mature males was significantly greater (p<0.05) than that of females with gonadal development. Notably, the pituitary volume in male turbot significantly increased (p<0.05) from immature to mature stage, but this difference did not occur in females. The data together illustrate a distinct sex difference in the turbot brain during gonadal development, providing insight into their HPG axes. [ABSTRACT FROM AUTHOR]

An eight-week feeding trial was conducted to investigate the effects of diets supplemented with three sulfur-containing amino acids (SAA), namely, methionine, cysteine, and taurine, on the intestinal health status of juvenile turbot (Scophthalmus maximus) fed high-lipid diets. Four diets were formulated, namely, a high-lipid control diet (16% lipid, HL) and three SAA-supplemented diets, which were formulated by supplementing 1.5% methionine (HLM), 1.5% cysteine (HLC), and 1.5% taurine (HLT) into the HL control diet, respectively. Each diet was assigned to triplicate tanks, and each tank was stocked with 30 juvenile fish (appr. initial weight, 8 g). The histological and morphometric results showed that dietary SAA supplementation obviously improved the intestinal morphology and integrity, in particular as reflected by higher height of microvilli and mucosal folds. Dietary SAA supplementation, in particular cysteine, up-regulated the gene expression of mucin-2 and tight junction proteins (ZO-1, Tricellilun and JAM). Dietary SAA supplementation remarkably down-regulated the gene expression of apoptosis-related factors such as p38, JNK, and Bax, expression of pro-inflammatory factors (e.g., NF-κB, AP-1 IL-1β, IL-8, and TNF-α). SAA supplementation resulted in higher antioxidative abilities in the intestine. Additionally, dietary SAA supplementation largely altered the communities of intestinal microbiota. Compared with the HL group, higher relative abundance of potential beneficial bacteria, and lower relative abundance of opportunistic pathogens were observed in SAA-supplemented groups. Dietary taurine supplementation significantly increased the relative abundance of Ligilactobacillus (in particular Lactobacillus murinus) and Limosilactobacillus (especially Lactobacillus reuteri). In conclusion, dietary sulfur-containing amino acids supplementation have promising potential in ameliorating the intestinal inflammation of turbot fed high-lipid diets. Especially dietary cysteine and taurine supplementation have more positive effects on the communities of the intestinal microbiota of turbot. • Dietary SAA can ameliorate the intestinal inflammation caused by high-lipid diets in turbot. • Dietary SAA enhanced the intestinal mucosal barrier function of turbot. • Dietary SAA improved the communities of intestinal microbiota of turbot. • Taurine increased the abundance of some lactic acid bacteria in the intestine of turbot. [ABSTRACT FROM AUTHOR]

Long non-coding RNA (lncRNA) play vital regulatory roles in various biological processes. Intestine is one of the most sensitive organs to environmental and homeostatic disruptions for fish. However, systematic profiles of lncRNAs in the intestine of teleost in responses to pathogen infections is still limited. Turbot (Scophthalmus maximus L.), an important commercial fish species in China, has been suffering with Vibrio anguillarum infection, resulted in dramatic economic loss. Hereinto, the intestinal tissues of turbot were sampled at 0 h, 2 h, 12 h, and 48 h following V. anguillarum infection. The histopathological analysis revealed that the pathological trauma was mainly present in intestinal tunica mucosal epithelium. After high-throughput sequencing and bioinformatic analysis, a total of 9722 lncRNAs and 21,194 mRNAs were obtained, and the average length and exon number of lncRNAs were both less than those of mRNAs. Among which, a set of 158 lncRNAs and 226 mRNAs were differentially expressed (DE-lncRNAs and DEGs) in turbot intestine at three time points, related to many immune-related genes such as complement, interleukin, chemokine, lysosome, and macrophage, indicating their potential critical roles in immune responses. In addition, 2803 and 1803 GO terms were enriched for DEGs and co-expressed target genes of DE-lncRNAs, respectively. Moreover, 127 and 50 KEGG pathways including cell adhesion molecules (CAMs), phagosome, JAK-STAT signaling pathway, cytokine-cytokine receptor interaction, and intestinal immune network for IgA production, were enriched for DEGs and co-expressed target genes of DE-lncRNAs, respectively. Finally, qRT-PCR was conducted to confirm the reliability of sequencing data. The present study will set the foundation for the future exploration of lncRNA functions in teleost in response to bacterial infection. • Intestine tissues of turbot were sampled at different time points following V. anguillarum infection. • The pathological trauma was mainly present in intestinal tunica mucosal epithelium. • A total of 158 lncRNAs and 226 mRNAs were differentially expressed, many of which were involved in immune activities. • qRT-PCR was conducted to confirm the reliability of sequencing data. [ABSTRACT FROM AUTHOR]

Excessive dietary carbohydrate commonly impairs the functions of liver and intestine in carnivorous fish. In the present study, a 10-week feeding trial was carried out to explore the regulation of biotin on the hepatic and intestinal inflammation and apoptosis in turbot (Scophthalmus maximus L.) fed with high carbohydrate diets. Three isonitrogenous and isolipidic experimental diets were designed as follows: the CC diet with 18.6% of carbohydrate and 0.04 mg/kg of biotin, the HC diet with 26.9% of carbohydrate and 0.05 mg/kg of biotin, and the HCB diet with 26.9% of carbohydrate and 1.62 mg/kg of biotin. Results showed that high dietary carbohydrate (HC diet) impaired the morphology of liver and intestine, however, inclusion of dietary biotin (HCB diet) normalized their morphology. Inflammation-related gene expression of nuclear factor κB p65 (nf-κb p65), tumor necrosis factor α (tnf-α), interleukin-1β (il-1β), il-6 and il-8, and the protein expression of NF-κB p65 in the liver and intestine were significantly up-regulated in the HC group compared to those in the CC group (P < 0.05), the HCB diet decreased their expression compared to the HC group (P < 0.05). The gene expression of il-10 and transforming growth factor-β (tgf-β) in the liver and intestine were significantly decreased in the HC group compared to the CC group (P < 0.05), and inclusion of dietary biotin increased the il-10 and tgf-β expression in the liver and intestine (P < 0.05). Moreover, compared to the CC group, the HC group had a stronger degree of DNA fragmentation and more TUNEL-positive cells in the liver and intestine, and the HCB group had a slighter degree of DNA fragmentation and fewer TUNEL-positive cells compared to the HC group. Meanwhile, the gene expression of B-cell lymphoma protein-2-associated X protein (bax) and executor apoptosis-related cysteine peptidase 3 (caspase-3) were significantly up-regulated and the gene expression of B-cell lymphoma-2 (bcl-2) was significantly down-regulated both in the liver and intestine in the HC group compared with those in the CC group (P < 0.05). Inclusion of dietary biotin significantly decreased the bax and caspase- 3 mRNA levels and increased bcl- 2 mRNA level in the liver and intestine (P < 0.05). In conclusion, high dietary carbohydrate (26.9% vs 18.6%) induced inflammation and apoptosis in liver and intestine. Supplementation of biotin (1.62 mg/kg vs 0.05 mg/kg) in diet can alleviate the high-dietary-carbohydrate-induced hepatic and intestinal inflammation as well as inhibit apoptosis in turbot. The present study provides basic data for the application of biotin into feed, especially the high-carbohydrate feed for turbot. • High dietary carbohydrate (26.9%) impaired the morphology of liver and intestine of turbot. • High dietary carbohydrate induced inflammation and apoptosis in liver and intestine. • Biotin alleviated the inflammation induced by high carbohydrate potentially via NF-κB pathway. • Biotin regulated apoptosis caused by high carbohydrate potentially via bax / bcl2 / caspase3 pathway. [ABSTRACT FROM AUTHOR]

Myostatin (MSTN), a member of the transforming growth factor‐β (TGF‐β) superfamily, has retained the function of inhibiting muscle growth in fish. Turbot Scophthalmus maximus possesses two MSTN paralogs (MSTNa and MSTNb), but their respective response to dietary nutrients is still unclear. To clarify the effects of fish protein hydrolysate (FPH) on MSTNa and MSTNb, their mRNA levels were quantified in the muscle using the fasting–refeeding experiment and long‐term feeding trial. Gene expressions in various tissues showed that MSTNb but not MSTNa was expressed mostly in the muscle. After 2 weeks of starvation, MSTNa expression was up‐regulated in the muscle by refeeding FPH diet at 3 h and 6 h, while MSTNb expression was affected from 3 h to 3 days. Moreover, changes in MSTNb expression over time showed that significant reduction was observed at 3 h in fish refed optimal levels of FPH, but at 6 h in fish refed excessive levels of FPH. The expressions of two MSTN paralogs and related gene expressions of TGF‐β/SMAD‐dependent signalling pathway were not significantly altered by graded levels of FPH after 7 days of refeeding, while the expressions of MSTNb as well as the upstream FMODa and downstream SMAD4 were significantly affected after the long‐term feeding trial (8 weeks). In conclusion, FPH mainly modulated the expression of MSTNb in the muscle, whereas MSTNa was only affected in the early stage of refeeding. Furthermore, during the refeeding period, optimal levels of FPH in diets may regulate MSTNb more rapidly to initiate compensatory growth. [ABSTRACT FROM AUTHOR]

• Discovered and identified a new type of aquaculture virus turbot circovirus (TurCV);. • The entire genome of TurCV was sequenced and its intracellular colonization morphology was identified. • TurCV mainly infects spleen and kidney in turbot. In China, a novel pathogen within the genus Circovirus has been identified as a causative agent of the 'novel acute hemorrhage syndrome' (NAHS) in aquacultured populations of turbot (Scophthalmus maximus L.). Histopathological examination using light microscopy revealed extensive necrosis within the cardiac, splenic, and renal tissues of the afflicted fish. Utilizing transmission electron microscopy (TEM), we detected the presence of circovirus particles within the cytoplasm of these cells, with the virions consistently exhibiting a spherical morphology of 20–40 nm in diameter. TEM inspections confirmed the predominance of these virions in the heart, spleen, and kidney. Subsequent molecular characterization through polymerase chain reaction (PCR) analysis corroborated the TEM findings, with positive signals in the aforementioned tissues, in stark contrast to the lack of detection in gill, fin, liver, and intestinal tissues. The TEM observations, supported by PCR electrophoresis data, strongly suggest that the spleen and kidney are the primary targets of the viral infection. Further characterization using biophysical, biochemical assays, and genomic sequencing confirmed the viral classification within the genus Circovirus , resulting in the nomenclature of turbot circovirus (TurCV). The current research endeavors to shed light on the pathogenesis of this pathogen, offering insights into the infection mechanisms of TurCV in this novel piscine host, thereby contributing to the broader understanding of its impact on turbot health and aquaculture. [ABSTRACT FROM AUTHOR]

This study evaluated the lipid content, fatty acid (FA) profile, and lipid peroxidation of turbot muscle before and after culinary processing, including traditional oven and grilling, with and without extra virgin olive oil. The impact of muscle location and skin presence was evaluated. The skin had negligible effects on FA profile, although grilling without skin resulted in a significantly higher cooking loss. The ventral muscle displayed a significantly higher total lipid content than the dorsal muscle. Processed samples, without oil, showed no significant FA profile differences compared to fresh muscle. However, lipid peroxidation significantly increased with culinary processing, particularly through oven cooking in the absence of olive oil. Although the incorporation of olive oil during culinary processing reduced EPA + DHA content, these LC-PUFA/100 g remained above the recommended daily intake of 250 mg for humans. While phenolic compounds present in olive oil, derived from hydroxitirosol and tyrosol, may not directly protect PUFAs, they appeared to contribute to the prevention of lipid peroxidation, particularly in longer processing (oven). In summary, farmed turbot has a very high nutritional value that is preserved when cooked under controlled conditions. • Turbot muscle was oven-baked or grilled, with and without olive oil. • Skin presence had negligible effects during the cooking process. • Lipid peroxidation increased in processed samples compared to fresh ones. • EPA + DHA levels were reduced in samples cooked with olive oil. • Turbot maintained high nutritional value when cooked under controlled conditions. [ABSTRACT FROM AUTHOR]

Aeromonas salmonicida is one of the most prevalent pathogens that causes huge economic losses to aquaculture. Effective vaccination is the first choice for preventing infection. Bacterial ghost (BG), an empty bacterial shell devoid of cytoplasm, is a promising vaccine antigen with distinct advantages. Herein, we established strategies for producing a substantial yield of A. salmonicida ghost (ASG) and investigated the immune-protective properties of it. As a result, 2.84 mg/ml NaOH was discovered to be capable of inducing considerable amounts of ASG. Furthermore, the ASG vaccine elicited adaptive immunity in turbots after rapid activation of innate immunity. Even though formalin-killed cells (FKC) produced a few more antibodies than ASG, ASG ultimately provided a much stronger immune protection effect because it strengthened cellular immunity, with a relative percentage survival (RPS) of 50.1 % compared to FKC. These findings demonstrated that ASG effectively activated cell-mediated immunity, which helped get rid of microorganisms inside cells. Therefore, this study presented novel perspectives for future research on furunculosis vaccine products based on ASG as an antigen. • Aeromonas salmonicida ghost (ASG) is a superior immunogen for inactivated vaccines. • The relative percentage survival of immunized turbot was up to 50.1 %. • ASG has the ability to induce a stronger cellular immune response. [ABSTRACT FROM AUTHOR]

Turbot (Psetta maxima) is a commercially valuable species in aquaculture, and the new strategies and models for growth are essential for rapid growth in aquaculture operations. Hence, the objectives of this study were to assess the best feeding protocol and growth model for turbot in culture conditions. Over a period of 2 years, growth data were recorded for the determination of the most suitable growth model. Starvation and subsequent refeeding were realized in juvenile fish. The fish were exposed to three feeding regimes. Control groups (C1 and C2) were fed daily to satiation throughout the weeks 11 and 14. Fish in the two treatments were deprived of food for 1‐week followed by 2 weeks or 1 week of refeeding (T1 and T2) in repeated cycles. In the second experimental group, fish were deprived of food for 1 day followed by 2 or 1 day of refeeding (T3 and T4) in repeated cycles. Length and weight were determined at daily/weekly feeding (C2/C1), feeding every other day/week (T4/T2), feeding at two‐day/week intervals (T3/T1) in all treatments. The results indicated that growth in the T1 and T4 groups exhibited similar results with the control group. Overall, alternative feeding strategies can be used instead of continuous feeding. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted, where turbot were fed four experimental diets, containing different LPC levels (0%, 0.1%, 0.25%, and 0.5%, named LPC0, LPC0.1, LPC0.25, and LPC0.5, respectively). The intestinal morphology results showed that there were no widened lamina propria and mixed inflammatory cells in the LPC-supplemented groups. Dietary LPC remarkably decreased the expression of TLRs (TLR3, TLR8, TLR9, and TLR22), MyD88, and signaling molecules (NF-κB, JNK, and AP-1). Similarly, diets with LPC supplementation markedly depressed the gene expression of NF-κB and JNK signaling pathway downstream genes (TNF-α, IL-1β, Bax, Caspase9, and Caspase-3). Furthermore, dietary LPC modified the intestinal microbial profiles, increasing the relative abundance of short-chain fatty acids-producers, lactic acid bacteria, and digestive enzyme-producing bacteria. Predictive functions of intestinal microbiota showed that turbot fed LPC diets had a relatively higher abundance of functions, such as lipid metabolism and immune system, but a lower abundance of functions, such as metabolic diseases and immune system diseases. The activities of intestinal acid phosphatase and alkaline phosphatase were also increased by dietary LPC. In conclusion, LPC supplementation could regulate the intestinal mucosal barrier via the TLR signaling pathway and alter the intestinal microbiota profile of turbot fed high-lipid diets. [ABSTRACT FROM AUTHOR]

Turbot (Scophthalmus maximus) is an important cold-water economic fish. However, the production and development of turbot industry has been constantly hindered by the frequent occurrence of some diseases. Lacking full-length transcriptome for turbot limits immune gene discoveries and gene structures analysis. Therefore, we generated a full-length transcriptome using mixed immune-related tissues of turbot with PacBio Sequel platform. In this study, a total of 31.7 Gb high quality data were generated with the average subreads length of 2618 bp. According to the presence of 5′ and 3′ primers as well as poly (A) tails, FL (Full-length) and NFL (Non-full-length) isoforms were obtained. Meanwhile, we identified 32,003 non-redundant transcripts, 76.02% of which was novel isoforms of known genes. In addition, 12,176 alternative splicing (AS) events, 6614 polyadenylation (APA) events, 1905 transcription factors, and 2703 lncRNAs were identified. This work is a comprehensive report on the full-length transcriptome of immune-related tissues of turbot, and it also provides valuable molecular resources for future research on the adaptation mechanisms and functional genomics of turbot. • Full-length transcriptome of turbot was generated using SMRT Sequencing technology. • The FL transcriptome comprised 32,003 non-redundant transcripts. • 12,176 AS events, 6614 APA events, 2703 lncRNAs, and 1905 TFs were identified. • Novel genes related to immunity from novel genes and unmapped transcripts were identified. [ABSTRACT FROM AUTHOR]

Furunculosis caused by Aeromonas salmonicida in turbot farming is increasingly leading to huge economic losses. In this study, an inactivated vaccine containing a compound adjuvant of ginseng stem leaf saponins and aluminum hydroxide gel (GSLS/Alum) was developed against A. salmonicida and evaluated on turbot. As a result, serum antibody titer in vaccinated group was significantly higher than that in control group and the relative percentage survival (RPS) was up to 75.7%. Comparatively, the RPS of groups that vaccinated with only inactivated vaccine and vaccine containing Alum adjuvant or an oil emulsion Montanide™ ISA 763A were 32.4%, 48.6% and 64.9%, respectively. Although the vaccine containing oil adjuvant elicited comparable IgM level as that containing the compound GSLS/Alum adjuvant, the latter had no obvious side effects. Moreover, the inactivated vaccine containing the compound adjuvant was more likely to induce a higher cellular immune response according to the expressions of some immune related genes. Most importantly, an excellent protection of the vaccine containing GSLS/Alum adjuvant was obtained when turbots were naturally infected under clinical condition. In summary, our study demonstrated that the formulation of GSLS and Alum is a potential compound adjuvant in turbot vaccine development. • Ginseng stem leaf saponins plus aluminium is effective and safe as vaccine adjuvants. • The relative percentage survival of immunized turbot was up to 75.7%. • Vaccine containing compound adjuvant protect turbots in clinical trial. • The compound adjuvant was more likely to induce a higher cellular immune response. [ABSTRACT FROM AUTHOR]

Neutrophils can capture and kill pathogens by releasing neutrophils extracellular traps (NETs), which play critical roles in anti-microbial infection in mammals; however, the mechanisms involved in NETs formation and its role in anti-bacterial infection in teleost fish remains largely unknown. In this study, to explore the function of NETs in turbot, we established an in vitro bacterial infection model in head kidney derived neutrophils, and found that the haemolysin over-expressed Edwardsiella piscicida (ethA +) could induce a robust phenotype of NETs, compared with that in wild type or ethA mutant (ethA + - ΔethA) strains. Besides, the NETosis was mediated by ethA + -induced pyroptosis, and arms the ability of bacterial killing in neutrophils of turbot. Moreover, we found that neutrophils elastase (NE) might involves in this pyroptotic signaling, rather than inflammatory Sm caspase. Taken together, this study reveals the important role of pyroptosis in NETs formation in turbot neutrophils, suggesting that NETs formation is a critical immune response during bacterial infection in teleost fish. • Haemolysin over-expressed E. piscicida (ethA + ) infection could induce NETs formation in turbot. • Neutrophils elastase (NE) might be involved in EthA + infection induced pyroptosis. • Pyroptosis mediated NETosis plays crucial roles in bacterial cleaning. [ABSTRACT FROM AUTHOR]

This study aimed to analyze the morphology of the tongue, which varies among fish species and has not been studied in turbot (Scophthalmus maximus), using macro‐anatomical, light and scanning electron microscopy (SEM). As research materials, the tongues of eight adult turbot, which were used for consumption, were examined. The roughly triangular‐shaped tongue of the turbot consisted of three parts: apex, body, and root. The thickness of the tongue continued to increase from the apex to the root. Although papillae were not observed in the macroscopic examination of the tongue, microscopic examination revealed the presence of cone‐like shaped papillae on the submucosa. The tongue was composed of mucosa, submucosa, and hyaline cartilage. By SEM the presence of the taste buds (Types I and III), taste pores and papillae on the dorsal surface were demonstrated. Taste buds are the first descriptions in S. maximus. Therefore our results could add new data to the fish tongue anatomy. Highlights: Morphological and morphometric data of the turbot (Scophthalmus maximus) tongue were obtained in this study and compared with other species. In addition, the dorsal surface of the turbot tongue was described for the first time using SEM. [ABSTRACT FROM AUTHOR]

A 30-day feeding trial was conducted to investigate the effects of the supplementation of mannan oligosaccharide (MOS) in the diet on the skin wound healing process of juvenile turbot (Scophthalmus maximus). Two groups of diets were formulated, the control diet (CON) and the control diet supplemented with 0.16 % MOS (MOS), which were fed to the turbot separately. Each group had 3 replicates, with 20 fish per replicate. At the end of the feeding trial, all the fish were weighed and counted. Then four fish per tank were randomly selected for sampling, and the skin of the rest fish was wounded by a biopsy punch. The wounded fish continued to be fed as usual with the same diets respectively, and then sampled again at the 1, 3, and 7 day(s) post wounding (dpw). The results by image analysis showed that the wound closure rate of wounded fish was significantly improved by the supplementation of dietary MOS. As for the results of gene expression, dietary MOS promoted the expression of pro-inflammatory factors (il-1β & tnf-α) and decreased the expression of anti-inflammatory factors (tgf-β1 & il-10). It also enhanced the expression of genes related to re-epithelialization (mmp-9, fgf2, tgf-β1, rock1), as well as new tissue formation and remodeling (fn1, lamb2, col1-α, vegf). Furthermore, dietary MOS promoted re-epithelialization, cell proliferation, collagen deposition, and angiogenesis according to the histomorphological observation. In addition, the supplementation of MOS modified the communities of skin microbiota, decreasing the abundance of Rolstonia, Pseudomonas, and Aeromonas, while increasing the abundance of Pseudoalteromonas luteoviolacea and Shewanella colwellianav. In conclusion, the supplementation of dietary MOS (0.16 %) can promote the re-epithelialization and the recruitment of inflammatory cells, stimulate ECM biosynthesis and angiogenesis, modify the communities of skin microbiota, and ultimately promote the skin wound healing process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)