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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]

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]

In this study, the spatial and temporal changes in the landings of whiting (Merlangius merlangus), red mullet (Mullus barbatus) and turbot (Scophthalmus maximus) caught in the Black Sea were discussed using the open access data set of officially recorded landing statistics published by Turkish Statistical Institute (TUIK). The landings of whiting in Turkish seas increased steadily from 1981 to 1988, reaching the highest amount in the 56-year period in 1988. In order years, fluctuation was observed in the production. The catch quantity of red mullet, which continued to increase until 1989, has been decreasing since then and reached its lowest catch amount since 1971 in the year 2022. Turbot, which had the highest catch in 1983, has a catch amount of less than 1000 tons since the early 2000s. In the period between 1967 and 2022, when comparing the production amounts of the Eastern and Western Black Sea, it was found that the majority of the red mullet and turbot catch was obtained from the Eastern Black Sea. Although the catch amount of whiting was high in the Eastern Black Sea until 2017, it has been determined that the Western Black Sea has had more catch since 2017. [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. [ABSTRACT FROM AUTHOR]

The accurate statistics of the number of fry plays an important role in improving the intelligent level of fry quality evaluation, breeding density estimation and fry sales. At present, the counting of Turbot seedling mainly relies on manual labor, which is of high labor intensity and low precision. Because of the characteristics of turbot fry, such as small individual, high transparency and irregular shape, the traditional method of seed counting cannot be directly applied to Turbot seed counting. To solve the above problems, a method of identifying and counting turbot fry based on ResNet34 was proposed. Firstly, a set of image sampling device was designed, which consisted of camera, light source and container, etc., and was suitable for small target counting. The clear fry image was obtained by adjusting the Angle of camera and light source, and then image preprocessing methods such as background difference, Gaussian filter, global gray linear transformation and morphological processing were used to achieve the foreground segmentation and preliminary positioning of fry. In order to effectively unify the sample space and the target space to be identified, the minimum external moment is used to regularize the foreground image initially, and the regularized sample is used to build the image sample set. In the identification stage of turbot fry, the same pretreatment method was used to obtain the target region to be identified, and ResNet34 framework was introduced as the identification model to realize the accurate identification of the target region seed. Finally, the number of turbot seedlings was calculated by counting the number of targets to be identified. The experimental results showed that the method achieved good accuracy in the identification and counting of tiny fry. The average accuracy of the recognition of turbot fry using ResNet34 framework reached 94. 27%, which was 8. 64 percentage points higher than that of SVM method and AlexNet method, and 7. 4 percentage points higher than that of SVM method. It is better than ResNet18 ( identification accuracy 93. 21%) and ResNet50 ( identification accuracy 93. 83%) and other similar structures. The average accuracy rate of fry counting of the model in this paper is 96. 28%, indicating that the proposed sample set construction and identification method can meet the needs of small target counting, and can provide technical reference for fish fry counting. [ABSTRACT FROM AUTHOR]

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]

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 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]

The experiment was to study the effect of different supplemental levels of Black soldier fly larvae powder on growth performance and serum biochemical indexes of turbot. A total of 240 juvenile turbot were randomly divided into four groups, with six replicates in each group and ten fish in each replicate. The fish in control group were fed with basic diet, and 15% group, 30% group and 45% group were fed with 15%, 30% and 45% Black soldier fly larvae powder instead of fish meal in basic diet, respectively. The pre-test lasted for 7 d and the formal test lasted for 60 d. The results showed that the final weight, WGR and CF of turbot in 45% group were significantly lower than those in control group and 15% group (P<0.05), and HSI in 30% group and 45% group was significantly lower than that in control group (P<0.05). Serum T-AOC and GSH-Px activity in 15% group and 30% group were significantly higher than those in control group (P<0.05). The activity of SOD in serum of turbot in experimental groups was significantly higher than that in control group (P<0.05). The activity of serum ACP in serum of turbot in 30% group and 45% group was significantly higher than that in control group (P<0.05), and the activity of ALP in serum of turbot in 45% group was significantly higher than that in control group (P<0.05). The serum TP content of turbot in 15% group and 30% group was significantly higher than that in control group, the serum ALT activity of turbot in 30% group was significantly higher than that in control group (P<0.05), and the serum TC content of turbot in experimental groups was significantly lower than that in control group (P<0.05). The experiment indicates that it is feasible to replace fish meal in diet with Black soldier fly larvae powder, and the effect of replacing 30% fish meal is better. [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]

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]

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]

The diseases triggered by Vibrio anguillarum infection have created huge economic losses to the turbot (Scophthalmus maximus) farming industry. However, the immune mechanism of turbot to V. anguillarum infection has not been deeply investigated. To better understand the immune response of turbot to V. anguillarum infection, transcriptome analysis of the head kidney and liver of turbot was performed. A total of 15,948 and 11,494 differentially expressed genes (DEGs) were obtained from the turbot head kidney and liver, respectively. Transcriptome analysis revealed that the head kidney and liver of turbot have some differences in the gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis of the DEGs for the different functions of these two organs. Although there are many uncertain factors in this immune process, such as the occurrence of alternative splicing (AS) events and the differences in the protein structure of the DEGs, the NFκB signalling pathway, MKK‐dependent AP‐1 activation, JAK‐STAT signalling pathway, the signal transmission of MHC Ⅰ and a series of DEGs including HSP90 driving NLRP3 to produce inflammatory factors (IL‐1β, IL‐8, TNFα, etc.) were possible important immune response pathways for turbot to V. anguillarum infection. Overall, our research has conducted a preliminary exploration of the immune mechanism of turbot in response to V. anguillarum infection. [ABSTRACT FROM AUTHOR]

The pattern recognition receptors (PRRs) can recognize the conserved molecular structures of pathogens to active the innate immune responses, and subsequently induce the antigen-specific adaptive immune responses for the clearance of infected pathogen. Among the PRRs, Toll-like receptors (TLRs) are the first and best characterized PRRs across all the species. Among the TLR members, TLR7 showed significant conservation across the vertebrates, with the lowest rate of evolution for its LRR domains from primates to fishes. In the current study, one TLR7 (Sm TLR7) gene was captured in turbot, with a 3144 bp open reading frame (ORF), that encoding 1047 amino acid residues. Following multiple sequence comparison, Sm TLR7 was found to have the highest similarity and identity both to Paralichthys olivaceus with 91.9% and 85.9%, respectively. In phylogenetic analysis, Sm TLR7 was firstly clustered with Japanese flounder, and then clustered with fugu, rainbow trout, and zebrafish. In addition, Sm TLR7 was widely expressed in all the examined tissues with the highest expression level in spleen, followed by skin, while the lowest expression level was detected in blood. Following both Edwardsiella tarda and Vibrio anguillarum challenge, Sm TLR7 was significantly down-regulated in gill and intestine, and up-regulated in skin. Moreover, Sm TLR7 was significantly up-regulated in head kidney macrophages following LPS, LTA, PGN and polyI:C stimulation, as well as showed the strongest binding ability to LPS, followed by PGN, LTA, and polyI:C in a dose-dependent manner. Finally, following RNAi of Sm TLR7, MyD88 and IL-1β were slightly up-regulated, while TRAF6 and IL-8 were significantly down-regulated. The characterization of TLR7 can expand our understanding of the PRRs in teleost fishes, and eventually aid the exploration of interactions between host and pathogen. • The TLR7 gene from turbot exhibited highly similarities with that in other teleosts. • Turbot TLR7 was significantly regulated in mucosal tissues following different bacteria challenge. • Turbot TLR7 showed significantly strong responses to LPS, LTA, PGN and poly I:C stimulation. • Following RNAi of TLR7, TRAF6 and IL-8 were significantly down-regulated. [ABSTRACT FROM AUTHOR]

Propolis is non-hazardous resinous substance mixture containing bioactive ingredients such as polyphenols, flavonoids and organic acid. It has been widely used as food supplement and immune adjuvant due to its benefits in anti-microbial and immunomodulation. Edwardsiella piscicida is a kind of threatening pathogen which could cause high mortality in turbot. However, whether propolis could enhance the innate immune response against E. piscicida infection in turbot remains unknown. In this study, we found dietary propolis addition could improve the expression of anti-oxidative stress related enzymes, e.g., SOD, CAT and GPT, and relieved the histopathological changes of juvenile turbot after E. piscicida infection. Moreover, propolis addition increased the expression of cytokines such as il-1β , il-6 and tnf-α in different organs of juvenile turbot. Importantly, rescued survival and decreased bacterial loads were observed in propolis feeding group. Taken together, these findings suggest that the important roles of propolis in protecting juvenile turbot from E. piscicida infection, indicating propolis might be applied as a promising immunopotentiator candidate in aquaculture. • Dietary propolis addition could enhance anti-oxidant stress activity of turbot. • Dietary propolis addition improved immune defense against E. piscicida infection of turbot. • The protection period could last at least 3 weeks after 4-week propolis feeding trail. [ABSTRACT FROM AUTHOR]

The class A scavenger receptors play important roles in innate immunity and are distributed on plasma membrane of macrophages and other cell types. Notably, the class A scavenger receptor 4 (SCARA4) contains a typical C-type (calcium-dependent) lectin domain, which belongs to the collectin family of pattern recognition receptors and is involved in the immune response against infection. Here, one turbot SCARA4 gene was identified with a 2,292 bp open reading frame (ORF) encoding 763 amino acid residues. Multiple sequence analysis and phylogenetic analysis confirmed that Sm SCARA4 gene was more close to that of P. olivaceus. Gene structure and syntenic analysis showed conserved exon/intron organization pattern and syntenic pattern across selected vertebrate species. Tissue distribution analysis showed Sm SCARA4 was expressed in all the tested healthy tissues with the relative high expression levels in skin, gill and spleen. Following both E. tarda and V. anguillarum challenge in vivo , Sm SCARA4 was significantly repressed in gill and intestine. Remarkably, Sm SCARA4 showed the strongest binding ability to LPS and strongest upregulation in turbot head kidney macrophages in response to LPS. Knockdown and overexpression of Sm SCARA4 revealed its interactions with the two pro-inflammatory cytokines, TNF-α and IL-1β. Finally, repression of Sm SCARA4 via combined treatment of LPS and overexpression of Sm SCARA4 construct in turbot head kidney macrophages further indicated an inhibitory role of Sm SCARA4 in LPS-stimulated inflammation. Taken together, turbot Sm SCARA4 plays an important role in turbot immunity, especially in the mucosa-related systems; Sm SCARA4 possesses strong binding specificity to LPS, and exerts protective roles in response to LPS infection by reducing the release of pro-inflammatory cytokines. The mechanisms of inhibitory role of Sm SCARA4 in LPS-elicited inflammation await further investigation. • Gene structure and syntenic analysis of SCARA4 showed conserved patterns across selected vertebrate species. • Sm SCARA4 was expressed in all the tested healthy tissues with the relative high expression levels in skin, gill and spleen. • Following both E. tarda and V. anguillarum challenge, Sm SCARA4 was significantly repressed in gill and intestine. • Sm SCARA4 showed the strongest binding ability to LPS and strongest upregulation in turbot head kidney macrophages in response to LPS. • Knockdown and overexpression of Sm SCARA4 revealed its interactions with TNF-α and IL-1β. [ABSTRACT FROM AUTHOR]

In this study sperm characteristics (sperm volume, sperm volume per kg fish, spermatocrit, sperm concentration, pH, and sperm motility) of wild‐caught and hatchery‐reared turbot (Scophthalmus maximus), originated from the Black Sea population, were assessed. In this regard, two different trials were conducted. On the Trial‐I, sperm characteristics of wild‐caught and hatchery‐reared turbot (4‐, 7‐, and 10‐year‐old) were comparatively investigated during the spawning season (May), on the Trial‐II, monthly variations of sperm characteristics of hatchery‐reared turbot (4‐year‐old) were investigated. On the Trial‐I, a positive correlation between body weight and sperm volume was recorded. Significant differences were noted in sperm volume, and sperm concentration, however, there was no significant difference between the groups in terms of sperm volume per kg of body weight, spermatocrit, and pH. The sperm motility showed a significant decrease after the 15 minutes post‐activation in all the specimens. The active spermatozoa rate of the wild‐caught turbot was 44% at 15 minutes post‐activation, whereas it was 16%, 13%, and 64% for 4‐, 7‐, and 10‐year‐old turbot, respectively. The average motility duration of the wild‐caught turbot spermatozoa was significantly longer compared to hatchery‐reared turbot despite having a comparatively lower initial motility rate than hatchery‐reared turbot. On Trial‐II spermiation duration of hatchery reared Black Sea turbot was determined as 6 months, starting from February until the end of July. The highest and the lowest sperm volume, and sperm volume per kg were recorded in June and July, respectively. Significant differences were determined between the months in terms of sperm volume per kg, sperm volume, spermatocrit, and sperm concentration, however, the pH was similar. These results demonstrate the sperm characteristics of wild‐caught and hatchery‐reared Black Sea turbot were different in the spawning season (May) and the potential spermiation season was between February and July. [ABSTRACT FROM AUTHOR]

A 12‐week feeding trial was conducted to investigate the effects of dietary Lactobacillus casei, stachyose, or combined (synbiotic) on immunity and intestinal health of turbot (Scophthalmus maximus. L). Four isonitrogenous and isolipidic diets were formulated: Control diet, Control diet with 1.0×108 CFU/g L. casei (LC), 25.0 g kg‐1 stachyose (ST) or 1.0 × 108 CFU/g L. casei + 25.0 g kg‐1 stachyose (SL) supplementation separately. The results showed that fish‐fed diets ST and SL had a significant higher activity of lysozyme and concentration of complement 3 and 4, and IgM in serum, while the higher activity of ACP was observed in LC and SL group. The highest viable counts of L. casei in mucosa and content of DI were observed in SL group. Diet SL significantly increased the PR of DI, expression of tight junction proteins, pcna and the bcl‐2/bax, while decreased the expression of caspase‐3 and caspase‐9. Moreover, diets LC, ST and SL remarkably decreased the abundance of Mycoplasma but increased the abundance of Lactobacillus and Bacteroides, α‐diversity, and altered the bacterial communities in DI. Therefore, both stachyose and L. casei could enhance the immunity and intestinal health of turbot, while the synbiotic was superior to individual administration of stachyose or L. casei. [ABSTRACT FROM AUTHOR]

Tetraploid fish are the key source of diploid gametes in polyploid breeding, and they can be induced by disrupting the first mitotic cell cleavage. In this study, the induction protocol of tetraploid by hydrostatic pressure shock and the viability of the tetraploid progenies were investigated in turbot, Scophthalmus maximus. Under water temperature of 14.5 ± 0.5 °C, fertilized diploid zygotes were treated by different combination of timing (65–90 min after fertilization, maf), pressure intensity (60–85 MPa), and duration (2–10 min), respectively. Ploidy level was determined by silver staining of NOR regions, karyotype analysis, and flow cytometry. The optimal protocol for the pressure shock induction was determined to be the combination of timing of 80 maf, 75 MPa of hydrostatic pressure, and 6 min of duration time. Two batches of tetraploid-induced progenies with a total of more than 73,000 morphologically normal larvae were produced. The hatching rates and tetraploidy rates of the two induction groups were 8.97% and 4.09% and 53.33% and 46.67% at 1 day after hatching (dah), respectively. At 150 dah, 1 out of 20 juveniles was identified as tetraploid by karyotype analysis. However, none of tetraploid juveniles was detected by the flow cytometry analysis among the 446 juveniles survived at 365 dah. This preliminary study provides the evidence supporting the large-scale production of tetraploid turbot progenies, thus encouraging further research on the subject. [ABSTRACT FROM AUTHOR]

Soya-saponins represent key anti-nutritional factors that contribute to soybean meal-induced enteritis, and glutamine is an effective fish intestine protectant that combats the negative effects of soya-saponins. Nuclear transcription factor-kappa B (NF-кB) systems are involved in the interactions between soya-saponins and glutamine, and the goal of the present work was to clarify the related molecular mechanisms used by the NF-кB kinase (IKK)/inhibitor of NF-κB (IκB)/NF-кB system. Primary cultured turbot (Scophthalmus maximus L.) intestinal epithelial cells were concurrently administrated with 1 mg/mL of soya-saponins and several levels of glutamine (0, 0.5, 1.0 and 2.0 mM) for 12 h and then subjected to real-time PCR and Western blot assays. Compared with cells treated with soya-saponins alone, glutamine significantly decreased the expression of interleukin-1 beta, interleukin 8 and tumor necrosis factor α genes, significantly reduced nuclear and cytosolic NF-κB p65 abundance levels in a dose-dependent manner, increased the IκBα protein level but decreased its phosphorylation, and down-regulated the IKKα/β and phosphorylated IKKα/β levels. In conclusion, this in vitro work confirmed that glutamine attenuated soya-saponin-induced inflammatory responses in turbot intestines. Moreover, it identified molecular pathways in which glutamine first decreased the p65 level and then prevented its nuclear translocation. In addition, glutamine reduced IκBα phosphorylation and maintained its level. Finally, glutamine decreased IKK expression and phosphorylation. ● Glutamine significantly decreased the expression of NF-кB target genes ● Glutamine significantly reduced nuclear and cytosolic NF-κB p65 abundance ● Glutamine increased the IκBα protein level but decreased its phosphorylation ● Glutamine down-regulated the IKKα/β and phosphorylated IKKα/β levels [ABSTRACT FROM AUTHOR]

Seven immune factors, lysozyme, hepcidin, heat-shock protein (HSP) 70, HSP90, immunoglobulin M, C-type lectin, and Lily-type lectin, were measured by PCR in the livers, spleens, and head kidneys of turbot infected with Vibrio anguillarum. Additive main effects and multiplicative interaction (AMMI) and genotype main effects and genotype × environment interaction (GGE) biplot analysis were used to analyze genotype × tissue interactions for immunological factors. The AMMI analysis revealed that immune factor expression was significantly affected by genotype, tissue, and genotype × tissue interactions. Genotype (65.85%) was the major contributor to the total variation in immune factor expression in comparison to tissue effects (7.54%) and genotype × tissue interactions (12.52%). GGE biplot analysis revealed differences in the ranking of the seven immune factors in the three tissues; head kidney possessed the strongest ability to distinguish the seven immune factors. The test tissue locations were divided into liver-spleen and head kidneys regions; HSP70 was expressed the highest in the liver-spleen regions, and lysozyme had the highest expression in the head kidney region. Overall, HSP70 and HSP90 had the best expression and stability in the three tissues. • Genotype was the major contributor to the total variation in immune factor expression. • HSP70 and lysozyme had the highest expression in the liver-spleen region and the head kidney region, respectively. • HSP70 and HSP90 would be the preferred breeding index. [ABSTRACT FROM AUTHOR]

The genetic parameters and activity of five immune factors, including lysozyme (LZ), acid phosphatase (ACP), nitric oxide synthase (NOS), superoxide dismutase (SOD), together with the concentration of total protein (PC), were evaluated in the serum of turbot infected with Vibrio anguillarum. A total of 900 turbot individuals from 30 full-sib families were subjected to experimental infection with V. anguillarum. The genetic parameters of the above-mentioned traits were determined and subsequently analysed: the heritability values of PC, LZ, ACP, NOS and SOD were 0.27, 0.21, 0.27, 0.29 and 0.20 respectively. The ranges of phenotypic, genetic and environmental correlations within each of the five immune factors were -0.252-0.711, -0.223-0.685 and -0.268-0.730 respectively. Considering that the heritabilities of LZ, ACP, NOS and SOD were moderate and that the genetic correlations between LZ, ACP, NOS and SOD were highly positive, it is inferred that the whole immunocompetence of turbot against V. anguillarum can be optimized through genetic improvement of these four immune traits using multi-trait integrated breeding technology or indirect selection. [ABSTRACT FROM AUTHOR]

Aeromonas salmonicida is an aquatic pathogen that can infect a variety of fish. Phage therapy has been applied to treat bacterial infections. In this study, we obtained three A. salmonicida subsp. masoucida phage isolates from sewage, and one phage (vB_AsM_ZHF) exhibited the best antibacterial effect, based on in vitro kinetics experiments. Sequencing indicated that the vB_AsM_ZHF genome is 161,887 bp (41.24% C+G content) with 237 predicted open reading frames. No antibiotic resistance or virulence genes were detected in the complete genome, which is a requirement for phage therapy safety. Intraperitoneal injection of phage vB_AsM_ZHF into turbot at 8 x 104 PFU/fish rescued turbot from A. salmonicida subsp. masoucida injection and reduced the bacterial burden by 1 order of magnitude. Injection of vB_AsM_ZHF also decreased levels of inflammatory cell infiltration in muscle tissue, cytokines interleukin-1 β (IL-1 β), tumor necrosis factor alpha (TNF-α), and gamma interferon (IFN-γ) in serum and the expression of the inflammatory factors IL-1 β, IL-6, IFN-γ, transforming growth factor β, TNF-α, and hepcidin in the liver, spleen, and head kidney of turbot. Phage vB_AsM_ZHF demonstrated antibacterial ability in vitro and in vivo and significantly reduced mortality in turbot challenged by A. salmonicida subsp. masoucida. This study revealed that phage vB_AsM_ZHF can effectively treat the infection caused by A. salmonicida subsp. masoucida in turbot. IMPORTANCE A. salmonicida is an aquatic pathogen that can infect different fish and causes economic loss to the global aquaculture industry. Clinical strains of A. salmonicida have developed multidrug resistance, and phage therapy is being evaluated for controlling bacterial infections. Phages are biological antibacterial agents and have the potential to be therapeutic agents against multidrug-resistant bacteria. In this study, three A. salmonicida subsp. masoucida phages were isolated from sewage, and their biological behaviors were characterized. The newly isolated phage vB_AsM_ZHF could inhibit A. salmonicida subsp. masoucida infection in vitro and in vivo, suggesting that it may be an alternative strategy to antibiotics for protecting fish against multidrug-resistant A. salmonicida subsp. masoucida in the aquaculture industry. [ABSTRACT FROM AUTHOR]

Background: Feeding-induced cell signaling and metabolic responses affect utilization of dietary nutrients but are rarely taken advantage of to improve animal nutrition.Objectives: We hypothesized that by modulating postprandial kinetics and signaling, improved dietary utilization and growth performance could be achieved in animals.Methods: Juvenile turbot (Scophthalmus maximus L.) with an initial mean ± SD weight of 10.1 ± 0.01 g were used. Two feeding frequencies (FFs), either 1 or 3 meals/d at a fixed 2.4% daily body weight ration, and 2 diets that were or were not supplemented with 1% crystalline leucine (Leu), were used in the 10-wk feeding trial. At the end of the trial, a 1-d force-feeding experiment was conducted using the aforementioned FF and experimental diets. Samples were collected for the analysis of postprandial kinetics of aminoacidemia, mechanistic target of rapamycin (mTOR) signaling activities, protein deposition, as well as the mRNA expression levels of key metabolic checkpoints at consecutive time points after feeding.Results: Increased FF and leucine supplementation significantly enhanced fish growth by 7.68% ± 0.53% (means ±SD) and 7.89% ± 1.25%, respectively, and protein retention by 4.01% ± 0.59% and 4.44% ± 1.63%, respectively, in feeding trial experiments. The durations of postprandial aminoacidemia and mTOR activation were extended by increased FF, whereas leucine supplementation enhanced mTOR signaling without influencing the postprandial free amino acids kinetics. Increased FF and leucine supplementation enhanced muscle protein deposition 21.6% ± 6.85% and 22.3% ± 1.52%, respectively, in a 24-h postfeeding period.Conclusions: We provided comprehensive characterization of the postprandial kinetics of nutrient sensing and metabolic responses under different feeding regimens and leucine supplementation in turbot. Fine-tuning of postprandial kinetics could provide a new direction for better dietary utilization and animal performances in aquaculture. [ABSTRACT FROM AUTHOR]

Turbot is one of the most valuable fish species in the Black Sea commercial fishery. The serious, dramatic depletion of the turbot stock and catches that began in the 1980s was caused by overfishing and poor ecological conditions. The state of the turbot stock began to improve in the northwestern part of the Black Sea in 2016. Landings were at their 30-year maximum in this part of the sea. Catches per unit effort (CPUEs) have been at a stable, high level there for the last few years. Average turbot weight and length have also been increasing. The Stock Synthesis (SS3) framework was used in the stock assessment. According to SS3 analysis, fishing mortality (F) reached the minimum level of 0.29 in 2018. The cumulative SPR (Spawner Potential Rate) index was 0.27, which approximately equaled SPRMSY = 0.25. Thus, currently the turbot stock is mostly moderately exploited at a level close to the management target in the northwestern part of the Black Sea. However, the entire Black Sea population has not fully recovered yet. [ABSTRACT FROM AUTHOR]

TLRs are the first and best-characterized pattern recognition receptors conserved across all the species. Different from mammals, the TLRs in teleost fishes are very diversified due to various evolutionary mechanisms. Here, we characterized one TLR1 gene in turbot, with a 2,415 bp open reading frame (ORF), that encoding 804 amino acid residues, and have the highest similarity and identity both to Paralichthys olivaceus with 88.9% and 79.9%. In phylogenetic analysis, it was firstly clustered with P. olivaceus , and then clustered with Takifugu rubripes. TLR1 was widely expressed in all the examined healthy tissues with the highest expression level in spleen, followed by head-kidney. In addition, it was significantly regulated in gill, skin and intestine following Edwardsiella tarda and Vibrio anguillarum challenge with different expression patterns. In in vitro stimulation with pathogen-associated molecular patterns, TLR1 showed significantly strong and elevated responses to LPS, but only responded to LTA and Poly(I:C) at the highest evaluated concentration, while no response was detected using PGN stimulation. Moreover, in subcellular localization analysis, TLR1 was distributed in the cytoplasm, membrane and nucleus. Taken together, TLR1 played vital roles for host immune response to bacterial infection, only with strong binding ability to LPS and involved in the production of inflammatory cytokines. However, the specific ligand for TLR1 and its functional association with other TLRs should be further characterized in fish species. • The TLR1 gene from turbot exhibited highly similarities with that in other teleosts. • Turbot TLR1 was widely expressed in all the examined tissues and significantly regulated in mucosal tissues following different bacteria challenge. • Turbot TLR1 showed much more significantly strong responses to LPS than LTA, poly I:C and PGN stimulation.. • Turbot TLR1 was distributed in the cytoplasm, membrane and nucleus. [ABSTRACT FROM AUTHOR]

Fish are largely dependent on dietary phosphorus for skeletal development and mineralization. In aquaculture, commercial diets commonly have higher phosphorus concentration than the basal requirements in most fish species to ensure growth and prevent bone mineral disorders. Excessive phosphorus in feeds is harmful for metabolism and results in an increase of wastes in farm effluents, which impact aquatic ecosystems. Previous studies have shown that depletion/excess of dietary phosphorus cause skeletal malformations and reduced/enhanced mineralization in fish. There is scarce information on dietary phosphorus requirements for optimal bone mineralization in species with different types of bone (cellular vs. acellular bone), which is particularly relevant for sustainable aquaculture. Thus, the aim of our study was to analyse the effect of dietary phosphorus concentrations on bone mineralization of turbot, a demersal acellular‐boned fish and valuable aquaculture species. Our results show that the dietary phosphorus concentration did not cause changes to the bone mineral density and the phosphate/calcium concentrations. No apparent skeletal malformations were detected. Additionally, we did not find an altered expression of genes involved in bone mineral metabolism. Taken together, our data show that the phosphorus requirements for optimum growth and bone mineralization in turbot are below those currently used commercially at least for the time period examined: 55–195 days postfertilization (dpf). [ABSTRACT FROM AUTHOR]

Soy saponins, as thermo-stable anti-nutrients in soybean meal (SBM), are the primary causal agents of SBM-induced enteritis, which represents a well-documented pathologic alternation involving the distal intestines of various farmed fish. Our previous work showed that soy saponins might lead to SBM-induced enteritis, destroy tight junction structure and induce oxidative damage in juvenile turbot. Glutamine, as a conditionally essential amino acid, is an important substrate utilized for the growth of intestinal epithelial cells. An 8-week feeding trial was carried out to determine whether glutamine can attenuate the detrimental effects of soy saponins. Three isonitrogenous-isolipidic experimental diets were formulated as follows: (i) fish meal-based diet (FM), considered as control; (ii) FM + 10 g/kg soy saponins, SAP; and (iii) SAP + 15 g/kg glutamine, GLN. The results showed that dietary soy saponins significantly increased the gene expression levels of inflammatory markers (IL-1β , IL-8 and TNF-α) and related signaling factors (NF-кB , AP-1 , p38 , JNK and ERK), which were remarkably attenuated by dietary glutamine. Compared to SAP group, GLN-fed fish exhibited significantly higher expression levels of tight junction genes (CLDN3 , CLDN4 , OCLN , Tricellulin and ZO-1). Glutamine supplementation in SAP diet markedly suppressed the production of reactive oxygen species, malondialdehyde and protein carbonyl, and enhanced the activities of antioxidant enzymes as well as the mRNA levels of HO-1 , SOD , GPX and Nrf2. Furthermore, GLN-fed fish had a remarkably lower number of autophagosomes compared to SAP-fed fish. In conclusion, our study indicated that glutamine could reverse the harmful effects of soy saponins on intestinal inflammation, tight junction disruption and oxidative damage, via attenuation of NF-кB, AP-1 and MAPK pathways and activation of Nrf2 pathway. Glutamine may have the function of controlling autophaghic process within an appropriate level of encountering inflammation. • Dietary glutamine reversed the harmful effects of soy saponins on turbot intestine. • Soy saponins induced inflammation, tight junction disruption and oxidative damage. • Glutamine and soy saponins could regulate NF-кB, AP-1, MAPK and Nrf2 pathways. • Glutamine has the function to control autophagy within an appropriate level. [ABSTRACT FROM AUTHOR]

Understanding sex determination (SD) across taxa is a major challenge for evolutionary biology. The new genomic tools are paving the way to identify genomic features underlying SD in fish, a group frequently showing limited sex chromosome differentiation and high SD evolutionary turnover. Turbot (Scophthalmus maximus) is a commercially important flatfish with an undifferentiated ZW/ZZ SD system and remarkable sexual dimorphism. Here we describe a new long-read turbot genome assembly used to disentangle the genetic architecture of turbot SD by combining genomics and classical genetics approaches. The new turbot genome assembly consists of 145 contigs (N50 = 22.9 Mb), 27 of them representing >95% of its estimated genome size. A genome wide association study (GWAS) identified a ~ 6.8 Mb region on chromosome 12 associated with sex in 69.4% of the 36 families analyzed. The highest associated markers flanked sox2 , the only gene in the region showing differential expression between sexes before gonad differentiation. A single SNP showed consistent differences between Z and W chromosomes. The analysis of a broad sample of families suggested the presence of additional genetic and/or environmental factors on turbot SD. The new chromosome-level turbot genome assembly, one of the most contiguous fish assemblies to date, facilitated the identification of sox2 as a consistent candidate gene putatively driving SD in this species. This chromosome SD system barely showed any signs of differentiation, and other factors beyond the main QTL seem to control SD in a certain proportion of families. • A chromosome-level genome assembly was constructed to disentangle the genetic architecture of turbot SD. • Data suggest that sox2, located within an intron of a long non-coding RNA, is the master SD gene of turbot. • Turbot shows an undifferentiated SD system with evidence of recombination suppression around the SD gene. • Other genomic regions and environmental factors are involved in turbot SD as supported by segregation analysis within families. [ABSTRACT FROM AUTHOR]

This study was carried out to determine the effects of replacement of wheat flour with wheat middling (WM) and supplemental phosphorus at a level of 1% on growth and nutrient utilization, whole body, fillet, viscera and liver proximate compositions in turbot, (Scophthalmus maximus Linnaeus, 1758). The control diet was based on a mixture of three fish meals and whole wheat flour. Fish with an average initial weight of 266.67±0.72 g were fed experimental diets for 9 weeks. Each treatment was tried in four replicates. At the end of the experiment, there were no significant effects of the treatment on growth rate, nutrient utilization parameters such as feed intake, feed conversion ratio, protein efficiency rate, nitrogen, lipid and energy gains and retentions, hepato-somatic index, viscero-somatic index, condition factor, whole body (except dry matter which was significantly lower in P added diet than the control) and organ nutrient compositions (P>0.05). The findings suggest that WM can totally replace wheat flour and there is a tendency of a positive contribution of dietary P supplementation on the response variables. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of different concentrations (20, 40 and 60 mg/L) of 3-aminobenzoic acid ethyl ester methanesulfonate (MS-222) on the quality changes in turbot during simulated transport in water. The results showed that the ammonia nitrogen content in the transportation water of each sample increased significantly, and the dissolved oxygen level decreased. The dissolved oxygen content in MS-222-treated samples was higher than that of control group (CK) samples. For turbot flesh quality, simulated transport in water led to a decrease in moisture, fat and protein contents in all samples. The MS-222-treated turbot samples showed higher pH values, glycogen contents, springiness and chewiness values and lower lactic acid contents comparing with the CK samples during simulated transport in water. In addition, the fresh and bitter amino acids in the muscle of turbot increased in each treatment group compared to the non-transported fish at the end of the simulated transport. The results showed that MS-222 treatment could retard the turbot transport stress and improve the quality of turbot during simulated transport in water. [ABSTRACT FROM AUTHOR]

A complex and dynamic community of microorganisms is attached to the mucosal surface of the fish gut. Gut microbes play important roles in fish metabolism and immunity. Edwardsiella piscicida infection of turbot causes Edwardsiellosis, and vaccination is an effective method to prevent and control aquaculture diseases. Here, intraperitoneal vaccination by E. piscicida 10Δ, a live attenuated vaccine candidate, significantly upregulated the expression of immune response-related genes in the turbot spleen and enhanced the serum antibody titers of IgM. 16S rRNA amplicon sequencing revealed that the vaccination of E. piscicida 10Δ slightly reduced the relative abundance of intestinal microbiota in turbot. Meanwhile, E. piscicida 10Δ potentially conferred the intestinal microbiota metabolic capacity associated with carbohydrate metabolism, while hypothetically impaired their metabolic capacity related to fatty acid degradation and amino acid metabolism. Collectively, E. piscicida 10Δ can effectively stimulate the host immune responses and has no apparent influence on the relative abundance of intestinal microbiota, which can thus be considered as a potentially safe live attenuated vaccine. • E. piscicida 10Δ upregulates the expression of immune response-related genes and enhances the serum antibody titer of IgM. • E. piscicida 10Δ has no apparent influence on the relative abundance of intestinal microbiota in turbot. • E. piscicida 10Δ potentially changes the metabolic capacity of intestinal microbiota. [ABSTRACT FROM AUTHOR]

In this study, changes in the physiological parameters of the muscles of living turbot (Scophthalmus maximus) fish during waterless preservation and transportation were assessed. Results indicated that the survival rate of turbot at low temperature, waterless conditions in pure O 2 was 100% at 24 h and 95% at 36 h. Crude fat, organic acids, free amino acids, ATP levels, and pH values in the fish at 12 h after revitalization were not significantly different (p < 0.05) in the waterless preservation treatment than they were in the control group. Total protein content in turbot meat of recovered fish was close to the content in the control group. Although the protein content was lower than it was in the control group, the difference was negligible. Moreover, the elasticity, chewiness, and viscosity of turbot meat after 12 h of recovery was the same as those attributes in fish in the control group. The low-temperature waterless preservation treatment induced a strong stress response in turbot fish, characterized by strong biochemical reactions that resulted in fluctuations in the level of several stress indicators. Nevertheless, the recovery period provided a partial recovery of the indicator levels. The results of this study will contribute to the development of an effective, eco-friendly method to improve the survival rate and quality of living turbot fish during waterless preservation and transport. The study provides new insights that can be used to improve the waterless preservation and transport of living turbot fish, while addressing both market needs and consumer expectations. • The waterless method allows for the delivery of live fish to larger market areas. • Waterless preservation increases loading capacity and density of a single transport. • This eco-friendly approach does not negatively affect the nutrient status of turbots. • Waterless preservation can enhance commodity value of aquaculture products. • Waterless preservation represents a non-toxic approach that keeps fish fresh. [ABSTRACT FROM AUTHOR]

A 56‐day feeding trial was conducted to investigate the effects of arachidonic acid (ARA) supplementation on growth and immunity of plant protein‐fed turbot (Scophthalmus maximus L.). Five isonitrogenous and isoenergetic diets were formulated, including fishmeal group (0.6 g/kg ARA), plant protein group (0.2 g/kg ARA) and plant protein groups supplemented with ARA (2.6, 7.4 and 11.8 g/kg ARA). Results showed that replacement of dietary fishmeal by plant protein blend significantly inhibited weight gain rate (WGR) from 511.53 ± 2.92% to 399.32 ± 5.40%. The specific growth rate (SGR) and final body weight (FBW) were also reduced. However, supplying ARA up to 11.8 g/kg could restore the WGR, SGR and FBW to the similar levels with FM group (p >.05). In addition to decreasing nutrient digestibility and distal intestinal morphology, the plant protein‐based diet also attenuated innate immune enzyme activity and triggered intestinal inflammation, which were significantly improved by ARA supplementation. Dietary ARA restored the expression of the anti‐inflammatory cytokine (transforming growth factor‐β) and reduced pro‐inflammatory cytokine (tumour necrosis factor‐α, interleukin‐1β and interleukin‐8) mRNA levels. Taken together, ARA supplementation in the plant protein‐based diet could improve growth performance and alleviate intestinal inflammation caused by dietary plant protein in juvenile turbot. [ABSTRACT FROM AUTHOR]

In this study, 1,800 turbot (Scophthalmus maximus) individuals from 30 full‐sib families were experimentally infected with Vibrio anguillarum, and the expression levels of the immune factors lysozyme, hepcidin, heat‐shock protein 70 (HSP70), HSP90, immunoglobulin M (IgM), C‐type lectin and Lily‐type lectin in the liver were measured by real‐time PCR. Heritability values of the seven immune factors were 0.289 ± 0.087, 0.092 ± 0.024, 0.282 ± 0.043, 0.244 ± 0.027, 0.343 ± 0.081, 0.092 ± 0.011 and 0.084 ± 0.009, respectively. The ranges of phenotypic, genetic and environmental correlations were –0.889 to 0.759, –0.841 to 0.888 and –0.919 to 0.883, respectively. The heritability values of HSP70, HSP90 and IgM were moderate, and the genetic correlations between HSP70, HSP90 and IgM were moderate to highly positive, which suggests that the immunocompetence of turbot against V. anguillarum can be improved by genetically improving these three immune characters via multi‐trait integrated breeding technology or indirect selection. [ABSTRACT FROM AUTHOR]