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Interferons (IFNs) represent a group of proteins with notable antiviral capabilities. Recently, the discovery of type IV IFN, i.e. IFN-υ has created a new avenue for research on class II cytokines. In the present study, IFN-υ was identified in blunt snout bream to possess conserved sequence CXXXXX[W/L] and gene locus. In the bream, IFN-υ was expressed in examined tissues and was induced significantly following poly(I:C) stimulation. With the stimulation of recombinant IFN-υ in vivo, transcriptome was sequenced in head kidney, and 814 DEGs were identified with 165 possible IFN-stimulated genes (ISGs) characterized through comparison with type I IFN induced ISGs in zebrafish. Furthermore, IFN-υ was found to show high affinity with CRFB12, but no interaction was observed between IFN-υ and CRFB4, through surface plasmon resonance (SPR) and coimmunoprecipitation (Co-IP) analyses. These results should contribute to the understanding of IFN-υ and its receptor complex, and importantly its immune function in inducing ISGs. • IFN-υ was cloned in blunt snout bream with conserved features. • The type IV IFN was constitutively expressed and was induced by poly(I:C). • Transcriptome induced by recombinant IFN-υ contains about 170 ISGs. • IFN-υ was found to interact with CRFB12, but not CRFB4. [ABSTRACT FROM AUTHOR]

The blunt snout bream (Megalobrama amblycephala , BSB) is one of important freshwater fish of value in China, but it has poor tolerance to hypoxia environment. To improve this disadvantage, we cultivate an improved blunt snout bream (BTBB) from a hybrid lineage of Megalobrama amblycephala (♀) × Culter alburnus (♂). In this study, we found that the BTBB had higher tolerance hypoxia than BSB. Moreover, in order to take a deep insight into the molecular mechanisms of higher hypoxia tolerance in BTBB, we analyzed the liver transcriptomes of BTBB and BSB under normoxic and hypoxia conditions comparatively and found out several differentially expressed genes (DEGs). Among the GO functional categories, negative regulation of response to stimulus (GO: 0048585), oxidation-reduction process (GO: 0055114), and response to oxidative stress (GO: 0006979) in biological processes were observed. In addition, according to Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, the results indicated that many DEGs participated in FoxO signaling pathway, MAPK signaling pathway, VEGF signaling pathway, PPAR signaling pathway and p53 signaling pathway, and other processes. This study provides important clues about the potential molecular mechanisms explaining the higher hypoxia tolerance in BTBB. It also presents further evidence for the enhanced ability to resist hypoxia in BTBB, which is significant for fish genetic breeding. • The BTBB had higher tolerance hypoxia than BSB. • KEGG pathway analysis showed that many DEGs were enriched in the hypoxia response pathway. • The molecular mechanism of hypoxia tolerance of BTBB was analyzed. [ABSTRACT FROM AUTHOR]

Juvenile blunt snout bream Megalobrama amblycephala were reared under three photoperiods, 8 L: 16D, 12 L: 12D and 16 L: 8D (L: light; D: dark) for over 8 weeks. The results showed that growth performance was significantly enhanced by long photoperiod. Contrary to feed conversion ratio, final length, final weight, weight gain and feed intake increased significantly as illumination time increased from 8 h daily to 16 h daily. Low size heterogeneity and whole-body lipid content in fish exposed to long photoperiod were also observed. Both relative mRNA expression level of GH and IGF-I increased as illumination time increased from 8 h to 16 h daily. The lowest value of plasma cortisol was observed at the middle the photophase while the highest value was observed at the transition between the day and night span. Hepatic MDA content significantly increased as illumination time increased from 8 h daily to 16 h daily. The activities of hepatic catalase and glutathione peroxidase were lowest in fish exposed to 16 L: 8D photoperiod and significantly lower than that in fish exposed to 8 L: 16D. These results indicate that photoperiod manipulation may not only improve growth performance but also reduce size heterogeneity. However, prolonged photoperiod could cause chronic stress since plasma cortisol level was higher in the long photoperiod group, leading to an increasing oxidative stress. • Long photoperiod not only improved growth performance but also reduced size heterogeneity. • Long photoperiod caused the elevated mRNA expression of GH and IGFI-I. • Long photoperiod may cause chronic stress, leading to oxidative stress. [ABSTRACT FROM AUTHOR]

Abstract This study was conducted to understand the effect of high-fat diet challenge on lipid transport and endoplasmic reticulum stress in blunt snout bream. Ninety fish (average weight: 41.84 ± 0.07 g) were randomly fed a control diet (6% fat) or a high-fat diet (11% fat) for 9 weeks. The growth performance and feed utilization efficiency were evaluated at the end of the trial. The liver samples of both groups were harvested for molecular analysis and histological evaluation. Compared to the Control group, the high-fat diet group showed no effects on either growth performance or energy intake in blunt snout bream. However, high-fat diet resulted in a massive accumulation of lipid and pathological structural alternations, and disrupted expression of lipid transport-related genes and endoplasmic reticulum stress in the liver of the fish. In vitro, after exposure of the isolated primary hepatocytes from blunt snout bream to oleic acid, the cells showed increased intracellular TG accumulation, decreased VLDL secretion, which was attributed to altered expression levels of lipid transport-related genes through the activated IRE1/XBP1 signaling. The oleic acid-induced detrimental effects were alleviated by co-incubating the cells with an IER1 inhibitor, 4μ8c. In conclusion, high-fat diet could lead to aberrant lipid secretion by activating the ER stress-associated IRE1/XBP1 pathway. Inhibiting the activity of IRE1 represents a promising target to rescue the side-effects of high-fat diet on the liver function of blunt snout bream. Highlights • High-fat diets could result in abnormal secretion and synthesis of VLDL protein. • High-fat diet could lead to aberrant lipid secretion by activating the ER stress-associated IRE1/XBP1 pathway. • Inhibiting the activity of IRE1 represents a promising target to rescue the side-effects of high-fat diet on fish. [ABSTRACT FROM AUTHOR]

Abstract RNase1 is an enzyme important in host defense in vertebrates where it degrades the RNA of bacteria and viruses. We evaluated the effect of RNase1 on the resistance to Aeromonas hydrophila infection in Megalobrama amblycephala. The fish were randomly divided into four groups: a blank group (none-treated M. amblycephala), a control group (injected PBS), a challenge group (A. hydrophila- injected) and a treatment group (pre-treated with RNase1 24 h before the A. hydrophila injection), and we collected five tissues of each group. Then we recorded changes in the levels of glutathione (GSH), oxidized glutathione (GSSG), hepatic catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA) and lysozyme; and the relative mRNA expression of catalase (CAT), selenium-dependent glutathione peroxidase (GPx), Cu/Superoxide dismutase (Cu/Zn-SOD), glutamate-cysteine ligase (GCLC), glutathione reductase (GR) and nuclear factor erythroid 2-related factor 2 (Nrf2) for four groups. The expression of six genes was highest in liver and blood of the blank group. It was significantly higher in the gut of the treatment group (compared to control and challenge groups) 12 h after the infection. The treatment group exhibited a significant increase in GSH, SOD and CAT activity, and a decrease in GSSG, MDA and lysozyme content (compared to the control and challenge groups) 6 and 12 h after infection. These results suggest that supplementation with RNase1 protein can enhance resistance against A. hydrophila infections in M. amblycephala. Highlights • CAT, GPx, Cu/Zn-SOD, GCLC, Nrf2 and GR genes in fish and mammals were analyzed. • These genes were highly expressed in liver and blood of healthy M.amblycephala. • Pre-treatment with RNase1 increase GSH, CAT and SOD activity after A.hydrophila infection. • Pre-treatment with RNase1 decrease GSSG, MDA and lysozyme content after A.hydrophila infection. • RNase1 protein play a protective role in M. amblycephala after A. hydrophila infection. [ABSTRACT FROM AUTHOR]

Abstract Currently, there is a trend to use high-fat diets in intensive aquaculture that is accompanied with incidence of fatty liver when dietary lipid level surpasses an upper limit. So, it is necessary to develop appropriate strategies to reduce the risk of fatty liver in commercial fish farming. Studies in mammals have revealed a correlation between fatty liver and AMP-activated protein kinase (AMPK) activity, which has been recognized as a key modulator of lipid metabolism. Considering the frequent occurrence of fatty liver in blunt snout bream farming, an in-vitro study was designed to evaluate the efficiency of metformin, as a stimulator of AMPK, in activation of AMPK and its subsequent effects on lipid metabolism in primary hepatocytes. Fish hepatocytes were seeded at a density of 1 × 106 ml−1 in 6-well tissue culture plates and treated with three different media including: 1) Leibovitz's L-15 medium [L15] as control, 2) high-fat medium [L15 + 400 μM oleic acid], and 3) metformin medium [L15 + 400 μM oleic acid+200 μM metformin]. After 48 h of culture, the cells and supernatant were collected for analysis. The results showed significant (P <.05) enhancement of cell triglyceride and total cholesterol concentrations in the high-fat group over control, and metformin addition significantly reduced the values. Also, the high-fat group exhibited significantly higher aspartate aminotransferase activity than both control and metformin groups. The lowest AMPK and phospho-AMPK protein expression was found in the high-fat group while metformin addition significantly up-regulated their expression levels. Mitochondrial and peroxisomal oxidation rates in the high-fat group were significantly lower than control while similar oxidation rates were observed for metformin treated and control groups. The high-fat group showed significantly lower CPT I activity than control, and metformin inclusion increased the activity. Expression of genes associated with lipid metabolism such as PPARα, CPT I, AOX, PGC-1α and TFAM was suppressed in the high-fat group, and metformin supplementation up-regulated their expression levels. The opposite trend was true for the expression of ACC2 gene. Also, the results showed down-regulation of FAS and SREBP-1C genes in the high-fat medium group, and metformin addition resulted in further reduction of their expression level. The lowest activities of mitochondrial complexes (I-III) were found in the high-fat group and metformin prevented high-fat-induced reduction of mitochondrial complexes activity. Notably increased concentrations of reactive oxygen species and malondialdehyde were found in the high-fat group, and metformin treatment reduced their concentrations. Moreover, metformin group exhibited higher glutathione peroxidase activity than the high-fat group. The findings in this study showed clearly that metformin activated AMPK in blunt snout bream hepatocytes, which contributed to enhanced lipid metabolism and attenuated lipid deposition in the cells incubated with high-fat medium. Highlights • Metformin was tested for AMP-activated protein kinase (AMPK) activation in fish. • Metformin reduced triglyceride and cholesterol concentrations in hepatocytes. • AMPK and phospho-AMPK protein expression was significantly enhanced by metformin. • Metformin increased fatty acid oxidation and lipid metabolism genes expression. [ABSTRACT FROM AUTHOR]

Abstract This study aimed to investigate the effects of dietary non-protein energy adjustments on the mitochondrial biosynthesis and function of juvenile Megalobrama amblycephala. Fish (average weight: 37.98 ± 0.07 g) were fed eight diets containing two dietary carbohydrate levels (30% and 43%) and four lipid sources (fish oil, soybean oil, palm oil and the mixed oil) for 11 weeks. Liver mitochondrial respiratory chain complex V activity and ATP (adenosine triphosphate) content both increased significantly with increasing dietary carbohydrate levels, whereas the opposite was true for the AMP (adenosine 5′-monophosphate)/ATP ratio, hepatic transcripts of AMP-activated protein kinase α1 (AMPKα1), AMPKα2, peroxisome proliferators γ-activated receptor coativator-1α (PGC-1α), NADH dehydrogenase 1 and cytochrome c oxidase 1 (COX1) as well as the activities of Na+-K+-ATPase, succinate dehydrogenase (SDH), citrate synthase (CS) and mitochondrial respiratory chain complex I, III and IV. Additionally, hepatic ATP content, the transcripts of AMPKα, COX1 and ATP6 and the activities of Na+-K+-ATPase, SDH, CS and mitochondrial respiratory chain complex III were all significantly affected by lipid sources. Furthermore, an interaction between dietary carbohydrate levels and lipid sources was also observed in the activities of liver mitochondrial Na+-K+-ATPase and respiratory chain complex III as well as the transcripts of ATP6 and PGC-1α. Overall, these findings suggested that dietary carbohydrate levels and lipid sources remarkably affected the mitochondrial biosynthesis and function of M. amblycephala. A diet containing 30% carbohydrate and FO could boost its mitochondrial biosynthesis, while that of 30% carbohydrate and SO could enhance the mitochondrial function. [ABSTRACT FROM AUTHOR]

Midkine (Mdk) is a heparin-binding growth factor that is involved in regulating cell growth, differentiation and migration. Here, we report the isolation and characterization of duplicated mdk genes in blunt snout bream ( Megalobrama amblycephala ). The mdka and - b genes encode 146 aa and 147 aa peptides, respectively, sharing a sequence identity of 64%. During embryogenesis, mdka mRNA is detectable after 12 h post-fertilization (hpf) and mdkb mRNA can be detected after 8 hpf, about 4 h prior to mdka mRNA. Whole-mount in situ hybridization demonstrated that two paralogs of mdk mRNA were detected in the brain and dorsal neural tube at 16 hpf. At 22 hpf, mdka mRNA was abundant in the brain and dorsal neural tube, whereas mdkb mRNA were transcribed in the brain and tailbud. Later, at 55 hpf, both paralogs were mainly expressed in the brain. Furthermore, both the mdk genes were highly expressed in multiple adult tissues except in the skin and a low expression of mdka in the muscle. In addition, they were differentially inhibited in the liver and intestine with exogenous recombinant human growth hormone, while their mRNA levels were up-regulated in the brain. During starvation, both the mdk genes were significantly up-regulated in the intestine, brain and liver and returned to the control levels following 6 days of refeeding. Our results suggest that duplicated mdk genes may play conserved and divergent roles in embryonic development and tissue growth regulation in blunt snout bream. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the interactive effects of dietary carbohydrate levels and lipid sources on growth performance, tissue fatty acid (FA) profiles and intermediary metabolism of Megalobrama amblycephala . Fish (average weight: 37.98 ± 0.07 g) were randomly fed one of eight diets containing two carbohydrate levels (30% and 43%) and four lipid sources (fish oil, FO; soybean oil, SO; palm oil, PaO; and mixed oil (FO: SO: PaO = 1:1:1), MO) for 11 weeks. Little difference ( P > 0.05) was observed in growth performance and whole-body composition (except for lipid). However, energy retention, body lipid content, tissue lipid and glycogen contents and plasma metabolites concentrations all increased significantly ( P < 0.05) with increasing carbohydrate levels. Additionally, nitrogen retention (NRE), body and tissue (liver and muscle) lipid content, liver and intraperitoneal fat glycogen contents and plasma metabolites concentrations were all significantly affected ( P < 0.05) by lipid sources. Hepatic and muscle monounsaturated fatty acids (MUFA) contents increased significantly ( P < 0.05) with increasing carbohydrate levels, whereas the opposite was true for eicosapentaenoic acid, docosahexaenoic acid, polyunsaturated fatty acids (PUFA) and n − 3 long-chain PUFA (n − 3 LC-PUFA) contents ( P < 0.05). In terms of lipid sources, fish fed FO presented a high proportion of n − 3 LC-PUFA, EPA and DHA ( P < 0.05); while fish received SO and PaO obtained a high proportion of n − 6 LC-PUFA and MUFA, respectively ( P < 0.05). Liver glucokinase, glycogen synthase, fatty acid synthetase (FAS), acetyl-CoA carboxylase α, delta-6 fatty acyl desaturase and peroxisome proliferator-activated receptor γ (PPARγ) as well as muscle pyruvate kinase (PK) expressions all increased significantly ( P < 0.05) with increasing carbohydrate levels, whereas the opposite was true for the transcriptions of enzymes involved in β-oxidation and gluconeogenesis. Hepatic FAS and muscle phosphoenolpyruvate carboxykinase (PEPCK) transcriptions were significantly affected ( P < 0.05) by lipid sources. Furthermore, an interaction between dietary carbohydrate levels and lipid sources was also observed in feed intake, NRE, body/tissue lipid and glycogen contents, plasma lipids, tissue MUFA, PUFA, n − 3 LC-PUFA and n − 6 LC-PUFA contents as well as the transcriptions of enzymes involved in glucose and lipid metabolism ( P < 0.05). Overall, these findings suggested that blunt snout bream can efficiently utilize various lipid sources at different carbohydrate levels. Dietary carbohydrate levels and lipid sources as well as their interaction significantly affected nutrient retention, tissue lipid and glycogen contents, plasma metabolites, tissue FA profiles and the intermediary metabolism, but not growth and feed efficiency. [ABSTRACT FROM AUTHOR]

As a competitive binding protein, follistatin (FST) antagonizes myostatin (MSTN) function and promotes muscle growth. Overexpression of FST in transgenic mice results in dramatically increased muscle mass caused by hyperplasia and/or hypertrophy. Previously, we identified two functional divergent fst genes (gc fst1 and gc fst2 ) in grass carp ( Ctenopharyngodon idella ). The objectives of this study were to determine if gc fst genes have similar roles on promoting muscle growth in fish. We generated a heterozygous gc fst1 - and gc fst2 -transgenic F0 generation in blunt snout bream ( Megalobrama amblycephala ). We then produced a homozygous gynogenetic F1 generation, and eventually a homozygous transgenic F2 generation. Driven by the zebrafish skeletal muscle-specific gene Mylz2 promoter, high levels of gc fst1 or gc fst2 mRNAs were expressed in embryonic somites and adult muscles in homozygous gc fst1 - or gc fst2 -transgenic F2 blunt snout bream, respectively. In contrast to gc fst1 -transgenic fish or wild-type controls, adult gc fst2 -transgenic F2 blunt snout bream exhibited a double-muscling phenotype and marked increases in body height and thickness. Overexpression of gcfst2 caused significant fiber size enlargement in skeletal muscle in gc fst2 -transgenic F2 blunt snout bream. Our findings suggest that enhanced muscle growth induced by gcfst2 overexpression in transgenic blunt snout bream is caused by hypertrophic muscle growth. This approach may be used to promote directional breeding in important aquaculture species such as blunt snout bream in the future. Statement of relevance To promote directional breeding in important aquaculture species blunt snout bream, our research papers presents novel data on fish breeding. Our article complies with the Policy Statement for submission of manuscripts to the Genetics Section. [ABSTRACT FROM AUTHOR]

A new hypoxia-tolerant variety of blunt snout bream was obtained by successive breeding of the wild population, which markedly improved hypoxia tolerance. In this study, the hypoxia-tolerant variety was exposed to hypoxia (2.0 mg O 2 ·L−1) for 4, 7 days. The contents of blood biochemical indicators including the number of red blood cells (RBC), total cholesterol (T-CHO), total protein (TP), triglyceride (TG), glucose (GLU), and lactic acid (LD) increased significantly (P < 0.05) under hypoxia. The glycogen content in the liver and muscle decreased significantly (P < 0.05) and the LD content in the brain, muscle and liver increased significantly (P < 0.05) under hypoxia. The levels of oxidative stress-related indicators i.e., superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), catalase (CAT), and total antioxidant capacity (T-AOC) also changed significantly (P < 0.05) in the heart, liver, and intestine of the new variety under hypoxia. Additionally, hypoxia has caused injuries to the heart, liver, and intestine, but it shows amazing repair ability during reoxygenation. The apoptotic cells and apoptosis rate in the heart, liver, and intestine increased under hypoxia. Under hypoxia, the expression of the B-cell lymphomas 2 (Bcl-2) gene in the heart, liver, and intestine was significantly (P < 0.05) down-regulated, while the expression of the BCL2-associated agonist of cell death (Bad) gene was significantly (P < 0.05) up-regulated. These results are of great significance for enriching the basic data of blunt snout bream new variety in response to hypoxia and promoting the healthy development of its culture industry. [Display omitted] • It provides some new insights into the hypoxia-tolerance of blunt snout bream new variety under hypoxia. • The results from this study will inspire future studies on tissue damage and repair of fish under hypoxia/reoxygenation. • The expression of Bcl-2 and Bad genes involved in apoptosis of blunt snout bream new variety under hypoxia was analyzed. • The oxidative stress, histological structure, and apoptosis of blunt snout bream under hypoxia were comprehensively analyzed. [ABSTRACT FROM AUTHOR]

A growth experiment was conducted to estimate the effects of dietary Zn on growth, antioxidant responses, and sperm motility of adult blunt snout bream, Megalobrama amblycephala. Six experimental diets were formulated, each containing graded levels of Zn (0, 20, 40, 80, 160, and 320 mg/kg, respectively) supplied as ZnSO 4 ·7H 2 O, providing the actual dietary Zn values of 7.8, 32.7, 50.3, 87.2, 165.4, and 328.5 mg/kg diet, respectively. Each diet was assigned to three replicate groups of 15 fish (mean initial body weight: 128.6 ± 0.7 g) for 12 weeks. Results showed that weight gain (WG) and whole body Zn content increased linearly with increasing dietary Zn levels, then remained nearly unchanged when Zn levels reached the 50.3 and 87.2 mg/kg diets, respectively. Fish fed with the control diet had a significantly higher feed conversion rate than those fed with Zn supplemented diets ( P < 0.05). Dietary Zn had no significant effects on crude protein of the fish body ( P > 0.05), but had a significant effect on moisture, lipid and ash content ( P < 0.05). Dietary Zn had significant effects on hepatic malondialdehyde content, superoxide dismutase, catalase, total antioxidant capacity, and glutathione peroxidase activity, but had no effect on serum glucose, high-density lipoprotein cholesterol, or total cholesterol content. Serum alkaline phosphatase activity increased significantly ( P < 0.05), whereas triglyceride content decreased significantly with the increase in dietary Zn levels ( P > 0.05). Testis histological sections showed few leydig cells in the control group. Sperm motility parameters were also affected by dietary Zn. A broken-line regression analysis showed that the optimum dietary Zn requirement of blunt snout bream (approx.128 g) was 52.1 mg/kg for maximum WG and 86.2 mg/kg for maximum whole body Zn content. Insufficient Zn inhibits the growth and testicular development of adult blunt snout bream. However, superfluous Zn (328.5 mg/kg) in the diet decreases the antioxidant function and sperm motility. [ABSTRACT FROM AUTHOR]

Hox genes encode transcription factors that play a key role in specifying the body plan in most metazoans. HoxPG13 genes most probably played an important role in body length variation during the evolution of animals. This is the first report of the mRNA expression patterns of the entire Hox paralog group 13 ( HoxA13a, HoxA13b, HoxB13a, HoxC13a, HoxC13b, HoxD13a ) in fish. Expression was studied by qPCR in five tissues of adult Megalobrama amblycephala specimens (spleen, liver, kidney, intestine and gills) and during development (17 stages: fertilised egg to 90 days-old juveniles). Expression in tissues (for all six genes) was generally very low in gills (0.0006–0.05), spleen (0.006–0.09) and kidney (0.02–0.39); the highest in intestine (from 2.28 for HoxC13b to 244.29 for HoxC13a ). During the development, a peak in expression around the hatching was observed for all six genes. Results suggest a high maternal expression of HoxA13a , and low for HoxA13ab . HoxD13a paralog exhibited the lowest expression: 0.0006–2.63 in tissues and 0.0005–1.7 during development, suggesting the possibility of a gradual loss of functionality. Expression of HoxC13 paralogs corroborates the findings in zebrafish: HoxC13b is maternally expressed and more important during the development. In adults, it was the opposite: expression was low for HoxC13b and very variable for HoxC13a (0.06–244.29). Differences in expression levels between both pairs of paralogs ( Aa / Ab and Ca / Cb ) indicate the possibility of the existence of some redundancy afforded by maintaining both paralogs. [ABSTRACT FROM AUTHOR]

This study carried out a 10-week feeding trial to investigate the effects of dietary folic acid on the growth, digestive enzyme activity, immune response and antioxidant enzyme activity of blunt snout bream ( Megalobrama amblycephala ) fingerlings. For this purpose, six semi-purified diets were formulated to contain graded levels of folic acid (0.0, 0.5, 1.0, 2.0, 5.0, and 10.0 mg/kg diets), and three tanks (300 l/tank) were randomly arranged and assigned to each experimental diet. Blunt snout bream fingerlings (initial weight 27.0 ± 0.03 g) were fed with the diets to near satiation four times daily. The results showed that final body weight, weight gain rate, specific growth rate and feed efficiency ratio significantly (P < 0.05) increased with an increasing dietary folic acid level of up to 1.0 mg/kg, plateaued at up to 2.0 mg/kg and thereafter reduced. Fish fed with 1.0–5.0 mg/kg dietary folic acid showed a significant rise (P < 0.05) in Fulton condition factor compared to those fed with an un-supplemented diet, while reverse trends were observed in viscerosomatic and hepatosomatic indexes. Serum urea content of the groups fed with 1.0 and 2.0 mg/kg dietary folic acid, and alkaline phosphate activity of the group fed with a 2.0 mg/kg diet were significantly lower than those fed with the control diet. Muscle crude protein content, serum total protein, complement 3, complement 4 and immunoglobulin M contents, and intestinal amylase, lipase, trypsin and chymotrypsin activities were significantly (P < 0.05) enhanced as the dietary folic acid level increased up to 1.0 mg/kg and thereafter plateaued. Malondialdehyde activity in fish fed with 1.0–5.0 mg/kg dietary folic acid was significantly lower than those fed with un-supplemented diet, while reverse patterns were found in superoxide dismutase and catalase activities (P < 0.05). Based on the broken line-regression analysis of weight gain rate, specific growth rate and hepatosomatic index, the optimum dietary folic acid for blunt snout fingerlings was estimated to be 0.68, 0.68 and 0.82 mg/kg, respectively. Statement of relevance Vitamins are considered as low molecular weight organic compounds that are required in small amounts for the maintenance of metabolism, normal growth and health of fish. Folic acid is a form of water-soluble vitamin B9, which is important in amino acid and nucleotide metabolism, growth and health of most aquatic animals. Blunt snout bream is a Chinese freshwater herbivorous species that has been recognized as a main aquaculture species, with high economic value which is mostly used in the fresh water polyculture system. Because of an increase in consumer demand and the relatively low production costs of this species, its production has rapidly expanded in China with 0.7 Mt in 2012. Nowadays, several nutritional requirements have been reported about this fish including some vitamin requirements. However, no information is available regarding the folic acid requirement of blunt snout bream. Therefore, this study hypothesized that dietary folic acid may improve growth and digestion, immune and antioxidant capacities of blunt snout bream fingerlings. [ABSTRACT FROM AUTHOR]

Carnitine palmitoyltransferase I (CPT I, EC 2.3.1.21) controls the main regulatory step of fatty acid oxidation, and hence studies of its molecular characterization are useful to understand lipid metabolism in cultured fish. Here, a full-length cDNA coding CPT I was cloned from liver of blunt snout bream Megalobrama amblycephala . This cDNA obtained covered 2499 bp with an open reading frame of 2181 bp encoding 726 amino acids. This CPT I mRNA predominantly expressed in heart and white muscle, while little in eye and spleen. The phylogenetic tree constructed on the basis of sequence alignments among several vertebrate species suggests that this blunt snout bream CPT I sequence belongs to the CPT IA family. In order to investigate the characterization of CPT IA mRNA expression, post-prandial experiment and feeding trial were conducted. The results showed that CPT IA mRNA expression was unchanged from 2 to 12 h, and then significantly increased at 24 h post-feeding in liver and heart. Berberine, an alkaloid, was identified as a promising lipid-lowering drug. In order to elucidate the effect of berberine on CPT I expression, fish were fed for 8 weeks with three diets (low-fat diet (LFD, 5% fat), high-fat diet (HFD, 15% fat), and berberine-supplemented diet (BSD, 15% fat). The results showed that HFD could decrease the expression of CPT IA and PPARα, while BSD increased those expressions. [ABSTRACT FROM AUTHOR]

Microsomal triglyceride transfer protein (MTTP), a major intracellular protein capable of transferring neutral lipids, plays a pivotal role in the assembly and secretion of apolipoprotein B-containing lipoproteins. In this study, MTTP cDNA was firstly cloned from the liver of blunt snout bream ( Megalobrama amblycephala ), the full-length cDNA covered 3457-bp with an open reading frame of 2661-bp, which encodes 886 amino acids, including a putative signal peptide of 24 amino acids long. After the feeding trial, a graded tissue-specific expression pattern of MTTP was observed and high expression abundance in the liver and intestine indicated its major function in lipid transport in this fish species. In addition, expression of genes encoding MTTP as well as peroxisome proliferator-activated receptor (PPAR), which are transcription factors and serve as key regulators in lipid homoeostasis, was all affected by dietary lipid and choline supplementations. Elevated dietary lipid levels significantly increased the liver, intestinal and muscle MTTP mRNA abundance. Additionally, the down-regulation of MTTP expression in the liver and muscle was observed when fish were fed with inadequate choline supplementation in high-fat diet, yet up-regulated as supplementing extra choline in diet. Expressions of PPARα and PPARβ in the liver and muscle showed similar trend of MTTP expression. The results suggested the potential connection of MTTP and PPAR in response to different dietary nutritional factors. Furthermore, extra choline supplementations could promote lipid transfer and enhance fatty acid oxidation, which indicated a molecular mechanism of choline on diminishing fat accumulation in blunt snout bream. [ABSTRACT FROM AUTHOR]

The study aimed to investigate the effect of feed palygorskite inclusion on pelleting technological characteristics, growth performance and tissue trace elements content of blunt snout bream, Megalobrama amblycephala . Diets without (control group) or with 2% palygorskite were pelleted and were measured for pelleting technological characteristics. Then the diets were fed to two groups of fish in four replicates (30 fish per replicate) for six weeks. Compared with the control group, dietary 2% palygorskite inclusion enhanced pellet production rate, pellet durability and the degree of starch gelatinization of pellet, and reduced percentage of fines. There was no difference in the weight gain, feed conversion rate, condition factor, hepatosomatic index and viscera/body ratio of fish between groups. Palygorskite supplementation significantly enhanced the Fe content in the blood and muscle and Zn content in the muscle, but reduced muscular Cd concentration. However, the accumulations of Cu and Pb in the body were not affected by palygorskite. The results indicated that dietary palygorskite supplementation could enhance pellet production efficiency, pellet quality, and alter trace elements accumulation in the tissues without impairing growth performance of blunt snout bream. [ABSTRACT FROM AUTHOR]

A feeding trial was conducted to determine the dietary threonine (Thr) requirement of juvenile blunt snout bream and to assess the effects of Thr on the growth performance, feed utilization, whole body composition, plasma composition and target of rapamycin (TOR) pathway gene expression. Five isonitrogenous and isoenergetic semi-purified diets (34% crude protein) were formulated to contain graded levels of dietary Thr (0.58, 1.08, 1.58, 2.08 and 2.58% in dry matter (DM)). l -Amino acid mixture was supplemented to simulate the whole body amino acid pattern of fish, except for Thr. Triplicate groups of juvenHabte-Michael Habte-Tsionile fish (initial weight, 3.01 ± 0.01 g) were fed with the respective diet to near satiation four times daily for 9 weeks. The results indicated that final body weight, weight gain rate (WGR), specific growth rate (SGR), feed efficiency ratio (FER), protein efficiency ratio (PER), protein retention value (PRV), Fulton condition factor ( K factor), and whole body protein content significantly ( P < 0.05) increased with increasing dietary Thr levels up to 1.58% and thereafter decreased. Plasma free Thr concentration and total protein content rose as dietary Thr levels increased ( P < 0.05). High dietary Thr level (2.58%) triggered plasma urea content ( P < 0.05). Dietary Thr regulated TOR and eukaryotic translation initiation factor 4E-binding protein 2 (4E-BP2) gene expressions in the proximal-intestine (PI), mid-intestine (MI) and distal-intestine (DI) of juvenile blunt snout bream, which may explain further that dietary Thr enhanced growth performance and protein retention. Based on the second-degree polynomial regression analysis of SGR against dietary Thr levels, the optimum dietary Thr level for juvenile blunt snout bream was estimated to be 1.57% of the diet, corresponding to 4.62% of dietary protein. [ABSTRACT FROM AUTHOR]

An 8-week experiment was conducted to determine the optimal feeding frequency of juvenile blunt snout bream Megalobrama amblycephala . Fish (8.87 ± 0.03 g) were randomly assigned to one of six feeding frequencies (1, 2, 3, 4, 5 and 6 times daily) and hand-fed at 8% of the biomass per day for the first 4 weeks and 6% for the remaining 4 weeks. The results showed that maximum final weight (29.75 ± 0.73 g) and weight gain (20.86 ± 0.77 g) was observed in fish fed 3 times daily. Whole-body lipid content increased significantly ( P < 0.05) as feeding frequency increased from 1 to 5 times daily, whereas moisture content showed an opposite trend. The activities of intestinal α-amylase and Na + , K + -ATPase increased significantly ( P < 0.05) as feeding frequency increased from 1 to 3 times daily, but decreased with further increasing feeding frequency. In addition, growth hormone (GH) mRNA expression level in the brain of fish fed 1 and 2 times daily significantly higher ( P < 0.05) than fish fed in other groups. Hepatic insulin-like growth factor-I (IGF-I) expression increased significantly ( P < 0.05) as feeding frequency increased from 1 to 3 times daily, but decreased significantly with further increasing feeding frequency. In conclusion, both low and high feeding frequency could result in growth retardation, poor feed efficiency, decreased intestinal enzyme activities and low hepatic IGF-I expression of juvenile blunt snout bream. The optimal feeding frequency for this species at the juvenile stage is 3 times daily. [ABSTRACT FROM AUTHOR]

Signal transducer and activator of transcription 3 (STAT3) is a major regulator of immune response and chronic inflammatory, which can be activated by interleukin-6 (IL-6). In mammals, STAT3 has multiple isoforms, and its function has been well studied. In teleost, a single stat3 has been cloned and identified in several species, but studies on its function are limited. In the present study, four stat3 isoforms including mastat3α1, mastat3α2, mastat3β1 and mastat3β2 were identified from blunt snout bream (Megalobrama amblycephala). The results of quantitative PCR (qPCR) showed that four mastat3 transcripts were ubiquitously expressed in all 10 tissues examined. After Aeromonas hydrophila challenge, the expression patterns of mastat3a1 , mastat3a2 and mastat3β2 were similar, but significantly different from that of mastat3β1. In addition, western blot showed that rmaIL-6+rmasIL-6R (IL-6 trans -signaling) significantly up-regulated phosphorylation levels of the four maSTAT3 isoforms and mRNA levels of the il-10 , il-11 , tnf-a , socs3a and socs3b genes, while rmaIL-6 (IL-6 classical signaling) only significantly up-regulated phosphorylation levels of the two maSTAT3α isoforms and mRNA levels of the il-10 , socs3a and socs3b genes. Meanwhile, overexpression or inhibition of JAK2 could significantly change the STAT3 phosphorylation. Finally, JAK2 and STAT3 inhibitors could significantly inhibit the up-regulation of il-10 , il-11 , tnf-a , socs3a and socs3b induced by rmaIL-6+rmasIL-6R or rmaIL-6. To sum up, this study reveals the functional distinctions and overlaps among the four maSTAT3 isoforms in blunt snout bream and reveals the differential regulation of IL-6 classical signaling and trans -signaling on downstream immune genes via the JAK2/STAT3 pathway, enriching our knowledge of fish's defense mechanisms against pathogens. • Four stat3 isoforms were identified from blunt snout bream. • After Aeronmonas hydrophila infection, mastat3α1 , mastat3α2 and mastat3β2 were up-regulated. • IL-6 classical signaling could activate both maSTAT3α isoforms. • IL-6 trans -signaling could activate four maSTAT3 isoforms. [ABSTRACT FROM AUTHOR]

In this study, we elucidated the choline metabolic pathways and its effects on growth and hepatic lipid transport in blunt snout bream, Megalobrama amblycephala . Fish were fed six experimental diets containing three lipid levels (5%, 8%, and 11%) and two choline supplementation levels (1200 and 1800 mg kg − 1 ) for 8 weeks. After the feeding trial, viscera/body ratio, hepatosomatic index, plasma aspartate aminotransferase activities, and plasma triglyceride and cholesterol contents as well as liver lipid content all increased significantly ( P < 0.05) as dietary lipid levels increased from 5 to 11% in terms of dietary lipid levels, whereas feed conversion ratio, plasma cholesterol content and liver lipid content decreased significantly ( P < 0.05) with increasing choline supplementations. Weight gain increased significantly ( P < 0.05) with increasing dietary choline supplementations when dietary lipid levels reached 11%. Additionally, hepatic lipid accumulation was further observed by oil red O staining. An increase in hepatic S-adenosylmethionine was found in fish fed diets supplemented with 1800 mg kg − 1 choline, indicating that extra choline supplementation increases very low density lipoprotein (VLDL) production through methylation of phosphatidylethanolamine to synthesize phosphatidylcholine. Additionally, increased SAM production resulted in a subsequent increase in glutathione concentration, suggesting a possible benefit in mitigating oxidative stress induced by a high-fat diet. 1800 mg kg − 1 choline supplementation in diet significantly up-regulated the relative mRNA expression levels of apolipoprotein B-100 and microsomal triglyceride transfer protein, which induced VLDL synthesis and assembly. [ABSTRACT FROM AUTHOR]

Abstract: A full-length cDNA coding lipoprotein lipase (LPL) was cloned from the visceral adipose tissue of blunt snout bream Megalobrama amblycephala by RT-PCR and rapid amplification of cDNA ends (RACE) approaches. The cDNA obtained covered 2372bp with an open reading frame of 1524bp encoding 507 amino acids, including a putative signal peptide of 22 amino acids long. Sequence alignment and phylogenetic analysis revealed a high degree of conservation (63–97%) among most fish and higher vertebrates, retaining the consensus sequence, the polypeptide “lid”, the catalytic triad and eight cysteine residues at the N-terminal region. Then, a 10-week feeding trial was conducted to investigate the effects of dietary lipid levels (4%, 8% and 12%) on the activity and mRNA expression of LPL in M. amblycephala. LPL activities in the visceral adipose tissue and white skeletal muscle both increased significantly (P <0.05) with increasing dietary lipid levels, whereas no significant difference (P >0.05) was also observed in that of the liver. LPL expressions in the visceral adipose tissue, liver and white skeletal muscles all increased significantly (P <0.05) as dietary lipid levels increased. In addition, a graded tissue-specific expression pattern of LPL (visceral adipose tissue>liver>white skeletal muscle) was also observed. The results indicated that LPL gene of M. amblycephala showed a typical structure of the lipase family, and shared a high similarity with that of the other vertebrates. In addition, an up-regulation of both LPL expressions and activities was observed in various tissues by high dietary lipid levels. [Copyright &y& Elsevier]

Abstract: A 9-week feeding trial was conducted to quantify the dietary arginine requirement of juvenile blunt snout bream. Six isonitrogenous and isoenergetic semi-purified diets (34.0% crude protein) were formulated to contain graded arginine levels (0.83% to 3.36% of dry weight) at 0.5% increments replaced by equal proportions of glycine. At the end of the feeding trial, the results showed that survival rate was not significantly affected by dietary arginine level. Final weight, specific growth rate (SGR), feed efficiency ratio (FER), protein efficiency ratio (PER) and protein productive value (PPV) increased with increasing dietary arginine level from 0.83 to 1.81% (P <0.05), thereafter showed a declining trend but the differences were not significant. Whole body compositions were independent of dietary arginine levels (P >0.05). Plasma arginine concentration increased with the increase of dietary arginine from 0.83% to 1.81%, and thereafter was relatively constant, while lower lysine content in plasma was observed in fish fed the diet with 3.36% arginine level compared to those fed diets with 0.83–2.35% arginine (P <0.05). Significantly higher plasma urea content was observed in fish fed diet with 3.36% arginine compared with those fed 0.83% arginine diet (0.83%). Significantly lower plasma total nitric oxide synthase (T-NOS) activities were observed in fish fed 0.83% arginine diet than those fed diets with 2.35–3.36% arginine. Plasma superoxide dismutase (SOD) activities and ammonia contents were not significantly affected by dietary arginine levels. Based on SGR, FER and PER, the optimal dietary arginine requirement of juvenile blunt snout bream was estimated to be 2.46% of the diet (7.23% of dietary protein), 2.28% (6.71% of dietary protein) and 2.26% of the diet (6.65% of dietary protein), respectively. [Copyright &y& Elsevier]

Abstract: High-fat diets may have favorable effects on growth partly based on protein-sparing, but high-fat diets often lead to excessive fat deposition in the liver of some fish. The goal of the study was therefore to investigate effects of fat-rich diet on mechanisms involved in fat deposition in the liver. Three hundred blunt snout bream (Megalobrama amblycephala) juveniles (initial weight 18.00±0.05g) were fed with two diets (5% or 15% fat) for 8weeks. Histological and biochemical parameters were determined. The hepatic triacylglycerol (TG) secretion rate was measured by intraperitoneal injection with poloxamer 407 (a lipoprotein lipase inhibitor). Lipid transport was studied by determining components of lipoproteins. We also examined lipid uptake by assaying lipoprotein lipase (LPL) activities and mRNA expressions in tissues. Our results showed that ultrastructural lesions of organelles in hepatocytes occurred after intake of a high-fat diet. The hepatic TG secretion rate and plasma very low density lipoprotein (VLDL) amount of fish fed high-fat diet were significantly lower compared to those of fish fed control diet. Concomitantly, variations of components of lipoproteins were also apparent. In the liver, muscle and mesenteric fat tissue, the percentage of polyunsaturated fatty acid (PUFA) was significantly increased, while both saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA) percentages decreased in high-fat group. Both activities and mRNA expressions of LPL were also increased in these tissues. On the whole, a low level of lipid transport out of the liver, alterations of lipid transport and elevated lipid uptake contributed to fatty liver of blunt snout bream fed high-fat diet. [Copyright &y& Elsevier]

Pond partitioned aquaculture system is developed in recent years, and it contributes to increasing yield and lowering land occupation. Based on the concept of partitioned aquaculture system, a new in-pond tank culture system (IPTCS) was constructed in this study. This system consists of culture tank, capture and aeration module, waste collection module, and vertical flow constructed wetland (VFCW), and the effective rearing area takes up about 10.05% of the pond area. In IPTCS, grass carp (Ctenopharyngodon idella Valenciennes, 1844) and blunt snout bream (Megalobrama amblycephala Yih, 1955) were reared at high and low stocking densities for 120 days. The initial density of grass carp in the high and low density groups was 15 kg m−3 and 7.5 kg m−3, respectively, and that of blunt snout bream were 10 kg m−3and 5 kg m−3. During the experiment, the aeration module worked 6 h / day, and the waste collection module worked 5 min / day. The results showed that high stocking density had a negative impact on the growth performance and muscle quality of grass carp and blunt snout bream, and that the water quality in the culture tank gradually was deteriorated with the increasing stocking density. The economic benefits of different stocking densities in this system were investigated in this study, and grass carp high-density rearing failed to generate high benefits, but blunt snout bream high-density rearing leads to a higher income. The feasibility and rearing effect of the in-pond culture tank system were preliminarily confirmed. • A new type of in-pond tank culture system (IPTCS) was constructed. • The economic benefit of theIPTCS was analyzed. [ABSTRACT FROM AUTHOR]

Blunt snout bream (BSB) is an important economic freshwater fish in China. One of technical bottlenecks in practice lies in improving its hypoxia tolerance. In this study, gynogenesis BSB (GBSB-R) is generated by artificial gynogenesis with UV-inactivated sperms of red crucian carp (RCC), which is regarded as one of freshwater fish with the strongest hypoxia-tolerance. Asynchronous development of the eye pigment further provides an objective morphologic evidence of distinguishing the gynogenesis BSB progeny with the hybrids of BSB (♀) × RCC (♂). It is found that the GBSB-R is a kind of all-female population with normal fertility and its genetic homozygosity is higher than that of wildtype BSB. In view of hypoxia stress tests, physiological indexes and gene expression, the obtained experimental data from this research confirm that the GBSB-R is a new strain with improved hypoxia tolerance, especially compared with the wildtype BSB. These results indicate that artificial gynogenesis is an efficient method to enlarge capacity of the BSB hypoxia tolerance, and the conducted research in this article is valuable to the practical aquaculture. • Gynogenesis blunt snout bream (GBSB-R) generated with UV-inactivated sperms of red crucian carp (RCC) • GBSB-R is a new strain with higher genetic homozygosity and stronger hypoxia tolerance than blunt snout bream (BSB) • An objective evidence to distinguish GBSB-R progeny with hybrids of BSB x RCC by asynchronous development of eye pigments [ABSTRACT FROM AUTHOR]

Crossbreeding has been conducted in many fish species. However, crosses between distant relatives that may result in higher levels of heterosis are hard to conduct due to reproductive isolation. In this study, diploid hybrids (BM) of blunt snout bream (Megalobrama amblycephala , BSB, ♀, order Cypriniformes, 2n = 48) × mandarin fish (order Siniperca chuatsi , MD, ♂, Perciformes, 2n = 48) were successfully produced. BM possessed 48 chromosomes from BSB. The body colour of BM (silver grey with many black spots) was different from that of BSB (silvery white) and MD (yellow with black stripes). The body shape of BM (small head with a slender body) was different from that of BSB (small head with a high back) and MD (body larger and flatter). We confirmed successful hybridization with microsatellite DNA markers and analysed the 5S rDNA patterns among the parental and hybrid lines. BM inherited its 5S rDNA entirely from the female parent (BSB). This study will provide a foundation for fish crossbreeding, and the successful hybrids in this study will potentially be an excellent commercial variety. • This was the first report on successful hybridization between species of the orders Cypriniformes and Perciformes. • Successful hybridization integrated genetic material from BSB and MD into BM hybrids, which might result in heterosis and make BM stronger. • The findings of this study are of great significance for fish breeding and genetics. [ABSTRACT FROM AUTHOR]

Blunt snout bream (BSB) is an important economic freshwater fish in China. One of technical bottlenecks in practice lies in improving its hypoxia tolerance. In this study, gynogenesis BSB (GBSB-R) is generated by artificial gynogenesis with UV-inactivated sperms of red crucian carp (RCC), which is regarded as one of freshwater fish with the strongest hypoxia-tolerance. Asynchronous development of the eye pigment further provides an objective morphologic evidence of distinguishing the gynogenesis BSB progeny with the hybrids of BSB (♀) × RCC (♂). It is found that the GBSB-R is a kind of all-female population with normal fertility and its genetic homozygosity is higher than that of wildtype BSB. In view of hypoxia stress tests, physiological indexes and gene expression, the obtained experimental data from this research confirm that the GBSB-R is a new strain with improved hypoxia tolerance, especially compared with the wildtype BSB. These results indicate that artificial gynogenesis is an efficient method to enlarge capacity of the BSB hypoxia tolerance, and the conducted research in this article is valuable to the practical aquaculture. • Gynogenesis blunt snout bream (GBSB-R) generated with UV-inactivated sperms of red crucian carp (RCC) • GBSB-R is a new strain with higher genetic homozygosity and stronger hypoxia tolerance than blunt snout bream (BSB) • An objective evidence to distinguish GBSB-R progeny with hybrids of BSB x RCC by asynchronous development of eye pigments [ABSTRACT FROM AUTHOR]

Crossbreeding has been conducted in many fish species. However, crosses between distant relatives that may result in higher levels of heterosis are hard to conduct due to reproductive isolation. In this study, diploid hybrids (BM) of blunt snout bream (Megalobrama amblycephala , BSB, ♀, order Cypriniformes, 2n = 48) × mandarin fish (order Siniperca chuatsi , MD, ♂, Perciformes, 2n = 48) were successfully produced. BM possessed 48 chromosomes from BSB. The body colour of BM (silver grey with many black spots) was different from that of BSB (silvery white) and MD (yellow with black stripes). The body shape of BM (small head with a slender body) was different from that of BSB (small head with a high back) and MD (body larger and flatter). We confirmed successful hybridization with microsatellite DNA markers and analysed the 5S rDNA patterns among the parental and hybrid lines. BM inherited its 5S rDNA entirely from the female parent (BSB). This study will provide a foundation for fish crossbreeding, and the successful hybrids in this study will potentially be an excellent commercial variety. • This was the first report on successful hybridization between species of the orders Cypriniformes and Perciformes. • Successful hybridization integrated genetic material from BSB and MD into BM hybrids, which might result in heterosis and make BM stronger. • The findings of this study are of great significance for fish breeding and genetics. [ABSTRACT FROM AUTHOR]

The blunt snout bream (Megalobrama amblycephala) is prone to a glucose metabolic disorder when it is exposed to a high-carbohydrate diet over a long period of time. The purpose of this study was to determine whether dietary L-tryptophan (L-trp) improves glucose regulation in blunt snout bream via effects on long non-coding RNAs (lncRNAs). Fish were fed a normal-carbohydrate diet (CN), a high-carbohydrate diet (HC), or a high-carbohydrate diet supplemented with L-trp (CL) for 9 weeks, then high-throughput sequencing was used to analyze hepatic RNA libraries. Totals of 4951 lncRNAs and 8357 mRNAs were identified. Of these, 189 differentially expressed lncRNAs and 634 differentially expressed mRNAs were identified, some of which were validated using qPCR. Enrichment analysis of the mRNAs that were co-expressed with lncRNAs identified 32 potential cis- regulatory and 892 potential trans -regulatory relationships. Functional analysis showed that these co-expressed genes were represented in 151 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, including 8 cis -KEGG enrichment pathways and 143 trans -KEGG enrichment pathways. Of the top 20 significant trans -enriched pathways, most were related to glucose metabolism, L-trp metabolism, and lipid metabolism, which suggested that L-trp might regulate glycolipid metabolism. The significantly differentially expressed mRNAs and lncRNAs that were upregulated in the HC group and downregulated in the CL group were used to construct a co-expression network. In total, 15 lncRNAs and 13 mRNA genes were included in this network, and most of the target genes were involved in the amelioration of insulin resistance and the maintenance of glucose homeostasis. Thus, we have generated a catalog of hepatic lncRNAs for the blunt snout bream and laid the foundation for further research into the regulation of glucose metabolism by dietary L-trp-induced lncRNAs. • This is the first study to profile lncRNAs in blunt snout bream. • LncRNAs and their target mRNAs are associated with glucose metabolism. • Novel pathways involved in the effects of dietary L-trp on glucose metabolism were identified. [ABSTRACT FROM AUTHOR]

• Phosphorus supplementation has positive effects on growth and reduces body lipid. • Phosphorus supplementation could activate the expression of the insulin signaling pathway. • Phosphorus supplementation could improve the antioxidant capacity. • Phosphorus supplementation enhancing the immune capacity of the liver. A 10-week feeding trial was conducted to investigate the effects of dietary phosphorus on the growth, glucolipid metabolism, antioxidant activity and immune status of the juvenile blunt snout bream. The fish were fed with three experimental diets containing graded phosphorus levels ranging from 8.1 (P8.1), 11.5 (P11.5) and 14.3 (P14.3) g/kg diet. The growth performance was significantly improved with increasing dietary phosphorus levels. Whole body ash content was highest in fish fed the P14.3 diet, while the lipid content showed the reverse trend. Plasma phosphorus, calcium and total protein contents increased significantly with increasing dietary phosphorus levels, and the lowest activities of alanine transaminase and content of triglycerides were observed in the P14.3 diet. The P11.5 diet enhanced glycolysis and lipid synthesis by improving the expression of core genes of glycometabolism and inhibiting the expression of key genes related to lipid synthesis. The P11.5 diet also improved the antioxidant capacity by activating the nuclear factor erythroid 2-related factor 2 signaling pathway and the activities of antioxidant enzymes. Besides, the expression of pro-inflammatory factor genes was reduced while the expression of anti-inflammatory factor genes was improved by dietary phosphorous supplementation. These results demonstrated that an appropriate phosphorus supplementation level has positive effects on growth, glucolipid metabolism, and health of the juvenile blunt snout bream. [ABSTRACT FROM AUTHOR]

Distant hybridization is an important technique and a useful strategy to obtain new germplasm resources. In this study, we obtained a new type of hybrid bream (BBTB) by two rounds of backcrossing from an established hybrid lineage of blunt snout bream (Megalobrama amblycephala , 2n = 48, BSB, ♀) × topmouth culter (Culter alburnus , 2n = 48, TC, ♂). The DNA content, chromosomal number, morphological traits, gonad histology, genetic composition, and muscle composition of BBTB were investigated. The determined DNA content, chromosomal number, and gonad histology showed that BBTB was a bisexual fertile diploid hybrid fish with 48 chromosomes. Analyses of the genetic composition revealed that the 5S rDNA and HoxD10a of BBTB were inherited from the two genomes of the original parents (BSB and TC). Analysis of muscle composition showed that BBTB possessed higher muscle protein levels and lower muscle carbohydrate levels than BSB. The newly obtained BBTB has the potential to establish a new diploid hybrid lineage and is highly significant for fish genetic breeding. • A new type of hybrid bream (BBTB) was obtained. • The BBTB possessed higher muscle protein levels and lower muscle carbohydrate levels than BSB. • The newly obtained BBTB had the potential to establish a new diploid hybrid lineage. [ABSTRACT FROM AUTHOR]

Zn-bearing palygorskite (Zn-Pal), prepared by the ion-exchange method with zinc (Zn) and palygorskite, has attracted attention due to its potential as an antibacterial agent and Zn source in animals. This study aimed to evaluate the effects of dietary Zn-Pal inclusion on growth, immunity, antioxidant capability, and resistance to transport stress in blunt snout bream (BNB). A total of 600 fish of similar size (average body weight, 27.78 ± 0.30 g) were randomly allotted into four groups and fed a basal diet (control group), basal diet supplemented with 90 mg/kg Zn as ZnSO 4 or 48 or 90 mg/kg Zn as Zn-Pal. Each diet was tested in five replicates with 30 fish per tank for 60 d. Compared with the control group, Zn-Pal inclusion enhanced the final body weight and feed utilization; increased the blood respiratory burst activity and the activities of plasma alkaline phosphatase, total superoxide dismutase, and copper/zinc superoxide dismutase (Cu/Zn-SOD); decreased the plasma cortisol, lactate and complement 4 (C4) contents; and upregulated the mRNA levels of nuclear factor erythroid 2-related factor 2, catalase, and Cu/Zn-SOD in the hepatopancreas (P < 0.05). Dietary Zn-Pal inclusion enhanced the lysozyme and C4 levels of plasma compared with the ZnSO 4 groups (P < 0.05). The inclusion of Zn-Pal in the diet alleviated transportation stress by improving the antioxidant capacity and immunity in BNB. In conclusion, dietary Zn-Pal inclusion increased growth and feed utilization, enhanced immunity and antioxidant capability, and improved resistance to transport stress in BNB. Zn-Pal is better than ZnSO 4 as an additive in the diet of BNB. • Zinc bearing palygorskite (Zn-Pal) improved antioxidant capability and immunity of blunt snout bream. • Transport procedure induced stress response in blunt snout bream. • Zn-Pal inclusion enhanced the resistance to transport stress in blunt snout bream. • Zn-Pal is better than ZnSO 4 as an additive in the diet of blunt snout bream. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the influences of dietary raw and gelatinized wheat starch and their ratios on the glycolipid metabolism, glucose tolerance and mitochondrial function of blunt snout bream Megalobrama amblycephala. Three diets incorporating 100% raw starch (R100), 100% gelatinized starch (G100) and 75% raw starch +25% gelatinized starch (R75/G25) were randomly assigned to 15 cages of fish for 10 weeks, after which fish were sampled. Then the remaining fish within each treatment were combined and later split into 6 tanks for a time series sampling in a glucose tolerance test. Daily gain index, relative feed intake and plasma levels of glucose, triglyceride, pyruvate and lactate all showed little difference among all the treatments. The R75/G25 group obtained the highest feed efficiency and tissue (namely liver and the abdominal fat tissue) glycogen contents. However, the highest tissue (namely muscle, liver and the abdominal fat tissue) lipid contents and plasma total cholesterol levels were both observed in the G100 group. In addition, the G100 group obtained significantly higher transcriptions of glucose transporter 2, glucokinase, peroxisome proliferator activated receptor γ and acetyl-CoA carboxylase α, but relatively low transcripts of the genes involved in gluconeogenesis and fatty acid β-oxidation, compared with the R100 group. The R100 group showed the highest glucose clearance rate, while the area under the glucose curve showed no statistical difference. Furthermore, the R100 group had relatively low activities of mitochondrial complex I, II, III and V as well as the transcriptions of cytochrome c oxidase 2, cytochrome b and NADH dehydrogenase 1 and ATP synthase 6 compared with other groups. Overall, our results suggested that high dietary inclusions of gelatinized starch could enhance the glucose transportation, glycolysis, lipogenesis, lipid deposition, glucose tolerance and mitochondrial function of blunt snout bream, while depress the gluconeogenesis and fatty acid oxidation. • Gelatinized starch enhanced glucose transportation, glycolysis and lipogenesis. • Gelatinized starch depressed gluconeogenesis and fatty acid oxidation. • Gelatinized starch improved glucose tolerance and mitochondrial function. [ABSTRACT FROM AUTHOR]

Myostatin (mstn) belongs to the TGF-β family, which is mainly involved in the negative regulation of myogenesis in vertebrates. Upon implementation of several gene-editing techniques (ZFN, TALEN, RNAi and CRISPR/Cas9), disruption of mstn gene locus in several animal species has been shown to result in elevated muscle growth. As there are numerous reports on gene editing of mstn in animals (common carp, yellow catfish, channel catfish, etc.), we aimed to study the complete disruption of mstn in economy-farmed fish. Here, we analyzed and characterized mstna and mstnb in blunt snout bream. In blunt snout bream, both mstna and mstnb peptides were found to possess unique structural characteristics of the TGF-β family. We designed three target sites (targets 1, 2, and 3) to generate knock out mutants within the mature mRNA sequence of mstna or mstnb that were located in exon 1, exon 3, and exon 3, respectively. The fertilized eggs (1–2 cell stage) were injected with 1 nL mixture of gRNA (100 pg) and Cas9 protein (900 pg). The mutation efficiency of mstna targets 1, 2, and 3 was 5.1%, 8.2%, and 10.0% with mutation types 5, 4, and 12, respectively. Similarly, the mutation efficiency of mstnb targets 1, 2, and 3 was 15.3%, 14.7%, and 26.0% with mutation types 2, 3, and 5, respectively. At the age of six months, the body weight, height, and thickness of both mstna - (mstna +/−) and mstnb - (mstnb +/−) deficient fish were found to be increased significantly (p <.01) when compared to those of wild-type control fish. Moreover, the average muscle fiber sizes of both mstna +/− and mstnb +/− fish were significantly larger (p <.01) than that of control fish. Our results provide valuable data associated with the regulation of muscle development and growth in blunt snout bream. These results also provide a basis and reference for the application of CRISPR/Cas9 (robust and efficient gene-engineering tool) in other aquaculture fish species. • The mutation efficiency and types of mstna and mstnb targets were statistically analyzed and summarized, respectively.. • The average muscle fiber sizes and other growth parameters of mstn -deficient fish were increased significantly (p<0.01). • Our experimental results provide valuable data in regulation of muscle development and growth in blunt snout bream. [ABSTRACT FROM AUTHOR]

The blunt snout bream (Megalobrama amblycephala , BSB) is important economic fish, but it is sensitive to hypoxia. To overcome this shortcoming, we previously obtained gynogenetic blunt snout bream (GBSB) with the enhanced ability to resist hypoxia. To explore the molecular mechanisms underlying the enhanced hypoxia tolerance of GBSB as a result of gynogenesis, in the present study, we conducted the comparative analyses of the liver transcriptomes of GBSB and BSB under normoxic conditions and identified differentially expressed genes (DEGs). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that many DEGs were enriched in the NF-kappa B signaling pathway (flip, nfkb2, cxcl8, il1b, tnfaip3, nfkbia, cox2, pias4, ube2i, malt1), hypoxia-inducible factor-1 (HIF-1) signaling pathway (hif-1α, vegfa, pfkfb2, glut1, hk), FOXO signaling pathway (pi3k, sgk1, foxo1, prmt1, pcka), and glycolysis/gluconeogenesis pathway (pgm, hk, aldo, pcka, gapa, acs). In addition, the average concentration of hemoglobin, which might be related to the NF-kappa B and HIF-1 signaling pathways, was higher in GBSB than in BSB (p < 0.05). This study provided important information regarding the potential molecular mechanisms underlying hypoxia tolerance in the GBSB, presenting further evidence for the enhanced ability to resist hypoxia in GBSB, which is significant for fish genetic breeding. • 7295 DEGs were identified between GBSB and BSB in liver by transcriptome analysis. • Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that many DEGs were enriched in the hypoxia response pathway. • The average hemoglobin concentration of GBSB was significantly higher than that of BSB (p < 0.05). [ABSTRACT FROM AUTHOR]