Grass Carp Ctenopharyngodon Idella Research Articles

The SIDT2/MDA5/IFN axis contributes to virus resistance in teleost fish

Disease resistance varies among fish species. The genetic factors contributing to disease resistance are largely unknown. Here, by comparative analysis on the disease resistance trait of grass carp (Ctenopharyngodon idellus, Ci) and barbel chub (Squaliobarbus curriculus, Sc), we report that the genes encoding SIDT2, MDA5 and IFN are associated with the resistance to viral infection. We identified the amino acid difference of SIDT2s, the existing or lacking of dsRNA binding loci in the carboxy-terminal domain (CTD) of MDA5s, and the promoter difference of ifn2s between the two fish species. Both CiSIDT2 and ScSIDT2 negatively regulate the MDA5-IRF3/7 mediated type I IFN reaction, and ScSIDT2 exhibited a stronger ability than CiSIDT2 to induce Ciirf7, Ciifn1, Ciifn2 and Cimx expressions, and to resist GCRV infection. ScMDA5 showed a greater ability than CiMDA5 in the induction of IRF7-mediated type I interferon and anti-GCRV function. CiMDA5 CTD inhibited Ciifn1 while enhanced Ciifn2 exrpessions, and ScMDA5 CTD exerts opposite effects on Ciifn1 and Ciifn2 expressions. ScMDA5 CTD possesses the ability to bind with GCRV nucleic acid fragments, while CiMDA5 lacking binding with virus genome. The promoter activities of Ciifn2 is significantly higher than that of Scifn2 owning to their differences in promoter sequences and binding proteins. These data revealed the mechanism of SIDT2-MDA5-IFN genetic architecture contributing to the difference in interspecies resistance and opening the possibility of molecular breeding for fish resistance.

Optimization of soybean oil content in a soybean oil-based aquafeed for grass carp (Ctenopharyngodon idella) to achieve optimal growth performance, proximate and fatty acid compositions, and lipid metabolism

Soybean oil (SO), an important plant-derived lipid, is routinely used in aquafeed as a partial substitute for fish oil. However, the effect of various contents of SO in a SO-based aquafeed on specific aquatic animals and the underlying mechanisms are unclear. In this study, five isonitrogenous diets containing different SO contents (0 %, 3 %, 6 %, 9 %, and 12 %, named as S0, S3, S6, S9, and S12, respectively) were prepared with SO as the predominant lipid source, and 12-week feeding experiments were conducted on juvenile grass carp (Ctenopharyngodon idella) (initial weight: 12.54 ± 0.08 g). Apart from lower feed conversion ratio in the S6 and S9 groups (P < 0.05), no obvious changes were observed in other growth indices (e.g., final weight and weight gain rate) in grass carp fed on diets with 0–9 % SO (P > 0.05). The S12 group exhibited significant decrease in the final weight and weight gain rate and increase in the viscerosomatic index (P < 0.05). Unlike gradual decrease in moisture, ash, and saturated fatty acid contents, muscle crude fat and unsaturated fatty acid (particularly polyunsaturated fatty acid) contents significantly increased with the increasing SO contents (P < 0.05). Serum triglyceride contents continuously increased with the increasing SO amounts, exhibiting the maximum value in the S12 group (P < 0.05). Similarly, the S12 group displayed the highest levels of aspartate aminotransferase, alanine transaminase, low-density lipoprotein cholesterol, and total cholesterol in serum (P < 0.05). Only the S12 group exhibited scanty lymphocytic infiltration in some areas of the hepatopancreas. However, other groups exhibited no obvious histopathological abnormalities. Lipogenic genes (dgat, fad, elovl1, elovl6, elovl7, lpcat, and pla2), ACSL family members (acsl1a, acsl1b, acsl3, acsl4, acsl5, and acsl6), lipolytic genes (atg1, cpt1a, cpt1b, hsl, and lpl), fatty acid transport-related genes (cd36, fabp, and fatp), and transcription factor involved in lipid metabolism (ppar α) were gradually upregulated as dietary SO content increased (P < 0.05). However, the transcript levels of srebp1 and its target gene acc1 exhibited decreasing trend under the same conditions, and significant downregulation of ppar γ was observed in the S12 group (P < 0.05). In conclusion, the optimal content of SO as the main lipid source in a SO-based diet for juvenile grass carp ranged from 6 % to 9 %, at which growth requirements of grass carp were met and fish health and fillet quality were effectively maintained. Our data provided a scientific reference for developing more efficient aquafeed formulations and enhancing fish flesh quality in aquaculture, as well as provided basic information for further assessing the regulatory mechanism of lipid homeostasis in teleost fishes.

An Observational Study of Skeletal Malformations in Four Semi-Intensively Reared Carp Species.

Cyprinids include some of the most widely farmed freshwater species. The aim of this study was to assess the incidence of skeletal malformations in carp species reared in semi-intensive systems in Albania: common carp (Cyprinus carpio), silver carp (Hypophthalmichthys molitrix), grass carp (Ctenopharyngodon idella) and bighead carp (Hypophthalmichthys nobilis). The common carp fingerlings had a mean total length of 28.9 ± 5.0 mm; the frequencies of individuals with at least one anomaly and at least one severe anomaly were 79.2% and 43.4%, respectively. The silver carp juveniles had a mean total length of 21.6 ± 2.1 mm; the frequencies of individuals with at least one anomaly and one severe anomaly were 93.1% and 57.5%, respectively. The grass carp fry had a mean total length of 33.5 ± 2.6 mm; all the analyzed specimens showed almost one anomaly and 86.4% showed at least one severe anomaly. The bighead carp juveniles had a mean total length of 34.4 ± 5.7 mm; the frequencies of individuals with at least one anomaly and at least one severe anomaly were 95.0% and 62.5%, respectively. The development of a more suitable feeding protocol for herbivorous species and the setting up of more efficient broodstock management protocols are suggested to reduce the high incidence of skeletal malformations.

Characterization of multi-copy C3 genes and association analysis of C3.1 polymorphism with GCRV resistance traits in Ctenopharyngodon idella

Molecular-assisted breeding plays an essential role in the selection of high disease -resistant fish in grass carp (Ctenopharyngodon idella) aquaculture. Complement 3 (C3) is a central molecule in the complement cascade and plays a polyfunctional role in immune defense, complement activation, and the inflammatory response. In this study, 9 copies of the C3 gene (named C3.1-C3.9) were identified in C. idella, and their structure, genomic location, phylogeny, expression patterns, and genetic characteristics were systematically analyzed. Phylogenetic analysis indicates that nine copies of grass carp C3 (hereafter called CiC3) cluster in the branch of Osteichthyes together with that of other fish, forming a different evolutionary branch distinct from other vertebrates. CiC3 are constitutively expressed in all examined tissues, among which CiC3.1 is the dominant C3 molecule. At 14 days of grass carp reovirus (GCRV) challenge, the CiC3s expression patterns share a similar expression trend. Furthermore, the comparison of the level of C3 protein, the mRNA expression level of dominant CiC3 (C3.1), and the mortality after GCRV challenge between the Xiangjiang River and Yangtze River grass carp indicate that the C3 protein exhibits distribution of polymorphism in a population, and the expression level of C3 is heritable and positively correlated with GCRV resistance. Furthermore, we identified 10 SNPs (named SNP1–10) of the C3.1 gene between GCRV-resistant and GCRV-susceptible grass carp groups. Inspiringly, SNP7 (g.76773C/T), SNP8 (g.76945 T/C), SNP1 (g.7065C/T), SNP9 (g.77153 A/C) and SNP10 (g.77252 T/C) have been verified to be significantly associated with the GCRV-resistant trait. Collectively, our findings provide potential molecular markers and relevant SNP sites for future grass carp breeding with respect to GCRV resistance.

Molecular cloning and characterization of BNIP3 and NIX1/2 and their role in DHA-induced mitophagy and apoptosis in grass carp (Ctenopharyngodon idellus) adipocytes

B-cell lymphoma-2 and adenovirus E1B 19-kDa-interacting protein 3 (BNIP3) and BNIP3 like (BNIP3L or NIX) play a vital role in regulating mitophagy and the intrinsic apoptosis in mammals, but their gene characterizations remain unclear in fish. Herein, bnip3, nix1 and nix2 were isolated and characterized from grass carp (Ctenopharyngodon idellus), which encode peptides of 194, 233 and 222 amino acids, respectively. As typical BH3-only proteins, grass carp BNIP3, NIX1 and NIX2 proteins contain BH3 and C-terminal transmembrane domains for inducing apoptosis. Moreover, the LC3-interacting region motif of BNIP3, NIX1 and NIX2 is also conserved in grass carp. Phylogenetic analyses also demonstrated that nix1 and nix2 may have originated from the genome duplication event. Expression pattern analysis indicated that bnip3, nix1 and nix2 were highest expressed in brain, followed by eye (bnip3) and liver (nix1 and nix2). BNIP3, NIX1 and NIX2 localized to the nucleus and the cytoplasm, with a predominant localization to mitochondria within the cytoplasm. In the present study, we found that 200 μM DHA impaired the mitochondrial function, manifested as the decreased antioxidant ability, cellular ATP content and mitochondrial membrane potential in grass carp adipocytes. In addition, the gene expression and enzyme activities of caspase family were significantly increased in 200 μM DHA group, indicating that adipocyte apoptosis was induced. Meanwhile, DHA increased the gene expression of bnip3, nix1 and nix2 in a dose-dependent manner in grass carp adipocytes. The colocalization of mitochondria and lysosomes was promoted by 200 μM DHA treatment, implying that BNIP3/NIX-related mitophagy was activated in adipocytes. Based on these findings, it can be inferred that BNIP3/NIX-related mitophagy may be involved in the adipocyte apoptosis induced by DHA in grass carp.

Relationships among the fish passage efficiency, fish swimming behavior, and hydraulic properties in a vertical‐slot fishway

AbstractThree‐dimensional hydrodynamic numerical simulation and laboratory fish‐passage experiment with juvenile grass carp (Ctenopharyngodon idella) were used to systematically estimate hydrodynamic parameters, fish passage efficiency, fish swimming behavior, and fish swimming trajectories in a vertical‐slot fishway (VSF) under five different flow discharges. The spatial‐mean time‐averaged velocity magnitude along the slot section determined passage success rate. The absolute value of the time‐averaged Reynolds‐shear‐stress component in the X–Y direction played a decisive role in selecting the swimming path. In addition, fish energy expenditure along the mean‐50% swimming route indicated that higher mainstream velocity did not necessarily signify larger energy consumption, because successfully‐migrating fish selected the relatively lower velocity zone during the migration process. Our findings for fish swimming behavior in response to velocity and turbulence can be used to develop high‐efficiency fishways for grass carps or other species with similar traits.

Effects of herbivorous fish on shallow lake ecosystems increase at moderate nutrient conditions

Submerged macrophytes are vital in shallow lakes, as they provide critical ecosystem functions and services and can stabilize the clear-water conditions by various mechanisms. Nutrient enrichment reduces the resilience of macrophyte dominance in shallow lakes, thereby making them susceptible to shifts towards phytoplankton dominance following perturbations. Here, we conducted a mesocosm experiment to examine the individual and combined effects of nutrient enrichment and the addition of grass carp (Ctenopharyngodon idella) on the abundance of submerged macrophytes, epiphyton, and phytoplankton. We hypothesized that moderate nutrient enrichment facilitates macrophyte abundance, but also phytoplankton abundance after macrophyte removal by herbivorous fish. Our data showed that herbivory by grass carp could trigger a shift from macrophytes to algal dominance in mesocosms with moderate nutrient concentrations, but not in those with low nutrient concentrations. Moderate nutrient enrichment alone promoted submerged macrophyte growth, whereas the introduction of grass carp induced a collapse of submerged macrophytes regardless of nutrient conditions. Moreover, the introduction of grass carp showed more negative effects on light conditions of the water column in mesocosms with moderate nutrient concentrations compared to those with low nutrient concentrations. A recovery of submerged macrophytes might thus be limited by low light availability in lakes with moderate nutrient conditions suffering grass carp perturbation. Our results suggest that submerged macrophyte-dominated shallow lakes with moderate nutrient conditions are vulnerable to perturbation by herbivorous fish such as grass carp. In turn, managing the abundance of herbivores in these lakes can support the dominance of macrophytes and associated clear water conditions.

Phosphofructokinase family genes in grass carp: Molecular identification and tissue-specific expression in response to glucose, insulin and glucagon.

It is widely acknowledged that glucose serves as the primary energy source for organisms. However, fish exhibit persistent postprandial hyperglycemia and are thought to have low glucose tolerance. Glycolysis serves as the ubiquitous pathway for glucose catabolism, with phosphofructokinase (PFK) acting as a crucial rate-limiting enzyme in this process and playing an indispensable role. PFK is classified into three isoforms based on their major expression sites, i.e., PFKM (skeletal muscle type), PFKL (liver type) and PFKP (platelet type). In this study, grass carp (Ctenopharyngodon idella) was used as animal model and the open reading frame (ORF) sequences of six PFK genetic isoforms of grass carp were cloned. Real-time PCR was used to detect its tissue distribution, and expression changes in oral glucose tolerance test (OGTT), insulin and glucagon injection experiments. The results showed that the ORF of pfkla, pfklb, pfkma, pfkmb, pfkpa and pfkpb genes was 2343, 2340, 2355, 2331, 2364 and 2349bp in length, respectively. The results of tissue distribution showed that pfkla and pfklb, homologous to mammalian pfkl, exhibited low expression levels in the liver of grass carp, but were expressed at the highest level in the brain. Muscle-type pfkma and pfkmb mRNA were found to be highly expressed in both red and white muscle, with pfkmb also exhibiting high expression levels in the heart, while platelet type pfkpa and pfkpb showed high mRNA abundances in the brain and heart. Oral glucose administration stimulated pfkma and pfkmb mRNA expression in the red muscle, and up-regulated pfklb mRNA levels in the liver at 3h post treatment, but it suppressed liver-type and platelet-type PFK genes expression in the brain. The expression of pfkmb in white muscle and pfkmb and pfkpb in heart were promoted by insulin, whereas the expression of pfkla and pfkpb in the brain, pfkma and pfkmb in the red muscle, pfkma in the white muscle, and pfklb in the liver was suppressed by insulin. As for glucagon, it inhibited pfkma and pfkmb mRNA expression in the red muscle, as well as pfklb in the liver, but it up-regulated PFK genes expression in most tissues detected, such as brain (pfklb, pfkpa and pfkpb), white muscle (pfkma and pfkmb), liver (pfkla) and heart (pfkmb and pfkpb). Our results suggest that PFK family genes have different or even opposite expression patterns in response to glucose, insulin and glucagon stimulation in various tissues of grass carp, which may contribute to glucose intolerance in fish.

Assessing grass carp (Ctenopharyngodon idella) occupancy and detection probability within Lake Erie from environmental DNA

Assessing grass carp (Ctenopharyngodon idella) occupancy and detection probability within Lake Erie from environmental DNA

Evidence of Microplastics in Gut Content of Grass Carp (Ctenopharyngodon idella) Fingerlings and their Effects on Growth Performance and Body Composition

Evidence of Microplastics in Gut Content of Grass Carp (Ctenopharyngodon idella) Fingerlings and their Effects on Growth Performance and Body Composition

Anti-infective immune functions of type IV interferon in grass carp (Ctenopharyngodon idella): a novel antibacterial and antiviral interferon in lower vertebrates

Anti-infective immune functions of type IV interferon in grass carp (Ctenopharyngodon idella): a novel antibacterial and antiviral interferon in lower vertebrates

Insights into Dietary Different Co-Forms of Lysine and Glutamate on Growth Performance, Muscle Development, Antioxidation and Related Gene Expressions in Juvenile Grass Carp (Ctenopharyngodon idellus).

The study aimed to compare the effects of crystalline L-lysine and L-glutamate (CAA), Lys-Glu dipeptide (KE) on the growth and muscle development of grass carp (Ctenopharyngodon idellus), and related molecular mechanisms. Five experimental diets (CR, 0.5% CAA, 1.5% CAA, 0.5% KE, 1.5% KE) containing Lys and Glu as free (Lys and Glu, CAA) dipeptide (Lys-Glu, KE) forms were prepared, respectively. A total of 450 juvenile grass carp with an initial weight of 10.69 ± 0.07g were randomly assigned to 15 cages, and 5 treatments with 3 replicates of 30 fish each for 61days of feeding. The results showed that the group of 0.5% KE exhibited the best growth performances according to the indicator's weight gain rate (WGR) and specific growth rate (SGR), although no statistically significant occurred among all groups; diet supplemented with 0.5% CAA significantly elevated the condition factor (CF) and viscerasomatic index (VSI) of juvenile grass carp. Diet supplemented with different Lys and Glu co-forms at different levels promoted the muscle amino acid content compared with those of CR group. Comparing with the CR group and other groups, the hardness of 0.5% CAA group significantly increased, and the springiness of 0.5% KE group excelled. Both the muscle fiber diameter and density of 0.5% KE group showed significant difference with those of the CR group, and a negative correlation between them was also observed. To uncover the related molecular mechanism of the differences caused by the different co-forms of Lys and Glu, the effect of different diets on the expressions of protein absorption, muscle quality, and antioxidation-related genes was analyzed. The results suggested that comparing with those of CR group, the dipeptide KE inhibited the expressions of genes associated with protein metabolism, such as AKT, S6K1, and FoxO1a but promoted PCNA expression, while the free style of CAA would improve the FoxO1a expression. Additionally, the muscle development-related genes (MyoD, MyOG, and Myf5) were significantly boosted in CAA co-form groups, and the expressions of fMYHCs were blocked but fMYHCs30 significantly promoted in 0.5% KE group. Finally, the effect of different co-forms of Lys and Glu on muscle antioxidant was examined. The 0.5% CAA diet was verified to increase GPX1a but obstruct Keap1 and GSTP1 expressions, resulting in enhanced SOD activity and reduced MDA levels in plasma. Collectively, the different co-forms of Lys and Glu influenced the growth of juvenile grass carp, and also the muscle development and quality through their different regulation on the protein metabolism, muscle development- and antioxidative-related genes.

JunD functions as a transcription factor of IL-10 to regulate bacterial infectious inflammation in grass carp (Ctenopharyngodon idella)

IL-10 is a key anti-inflammatory mediator ensuring the protection of a host from excessive inflammation in response to pathogen infections, whose transcription or expression levels are tightly linked to the onset and progression of infectious diseases. An AP-1 family member called CiJunD was shown to be a transcription factor of IL-10 in grass carp (Ctenopharyngodon idella) in the current study. CiJunD protein harbored the conserved Jun and bZIP domains. Mutant experiments demonstrated that CiJunD bound to three specific sites on IL-10 promoter, i.e., 5′-ATTATTCATA-3′, 5′-AGATGAGACATCT-3′, and 5′-ATTATTCATC-3′, mainly relying on the bZIP domain, and initiated IL-10 transcription. Expression data from the grass carp spleen infected by Aeromonas hydrophila and lipopolysaccharide (LPS) challenged spleen leukocytes indicated that the expressions of CiJunD and IL-10 were positively correlated, while the expression of pro-inflammatory cytokines, such as IL-1β, IL-6, IL-8, IFN-γ, and TNF-α, showed an overall downward trend when CiJunD and IL-10 peaked. The ability of CiJunD to down-regulate the production of pro-inflammatory cytokines and up-regulate the expression of IL-10, both with and without LPS stimulation, was confirmed by overexpression experiments. Meanwhile, the subcellular fractionation assay revealed that the nuclear translocation of CiJunD was significantly enhanced after the LPS challenge. Moreover, in vivo administration of grass carp with Oxamflatin, a potent agonist of JunD activity, could promote IL-10 but suppress the expression of pro-inflammatory cytokines. Intriguingly, tissue inflammation lesions and the survival rates of grass carp infected with A. hydrophila were also significantly improved by Oxamflatin administration. This work sheds light on the regulation mechanism by JunD of IL-10 expression and bacterial infectious inflammation for the first time, and it may present a viable method for preventing infectious diseases in fish by regulating IL-10 expression and inflammatory response.

Аналіз ураження коропових риб ендо- та ектопаразитами у рибогосподарських водоймах Одеської області

Purpose. Conducting an analysis of parasitic diseases of different age groups of carps grown in specialized fish farms of Odesa region under different forms of ownership for 2014–2023. Methodology. The paper presents the generalized results of studies carried out during planned test catches in specialized fish farms of various forms of ownership located in Odesa region. Parasitological studies were carried out according to the Bykhovska-Pavlovska method. The study included: visual inspection; excision of skin and muscle tissue; microscopy of scrapings from the surface of the body, fins and gills; microscopy of eye lenses; pathological autopsy, search for parasites in the body cavity; compression microscopy of internal organs and muscle tissue; intestinal dissection; gallbladder microscopy; dissection and microscopy of the swim bladder walls. At the same time, the parasitic species were identified, and the extensiveness and intensity of the invasion were calculated. Parasites were identified using identification keys. Findings. The study was conducted by employees of the ichthyopathology laboratory of the Institute of Fisheries of the National Academy of Sciences in laboratory conditions and at sampling sites in the period from 2014 to 2023. The objects of the study were different age groups of common carp (Cyprinus carpio), hybrids of silver and bighead carps (Hypophthalmichthys spp.), grass carp (Ctenopharyngodon idella) and crucian carp. Parasitological analysis showed that carp were most often affected by monogeneans, the prevalence (P) was 50.6% of the studied fish, and infestation intensity (II) was an average of 10 parasites per fish. In addition, a large percentage of infection was caused by ciliates with P of 24% P, II was 9 parasites per fish. Grass carp, in turn, were most affected by ciliates — P 56.3% with an average II — 16 parasites per fish and monogeneans — P 36.4% with an average II — 12 parasites per fish and trematodes — P 25.4% with II 8 parasites per fish. Grass carp was the most affected by crustaceans, the P was 46.6%, and the II was 3 parasites per fish, trematode P 16.6% with an average II of 10 parasites per fish. In Prussian carp, infestation by monogeneans was most often detected, which reached 75% with II — 5 parasites per fish. In the period of 2019-2023, carp was most often affected by monogeneans, where P was 29.3%, and II was 3 parasites per fish, also a high percentage of infection was due to ciliates 24%, II was 6 parasites per fish. Chinese carps, in turn, was most affected by trematodes — P 59.1% at II — 60 parasites per fish. Grass carp was the most affected by diplostoma, where P was 45.5% with an average II of 45 parasites per fish. Crucian carp was most affected by lernea. Based on the analysis of data on parasitic diseases of freshwater fish, it can be concluded that both in the period 2014‒2018 and 2019‒2023, fish were most often affected by monogeneans and infusoria, but in the period 2019‒2023, the infestation of silver and grass carps by diplostomes and postodiplostomes increased significantly. Originality. An analysis of parasitic diseases of carp grown in specialized farms of various forms of ownership, located in the Odesa region for the period of over the past ten years has been presented. The results of these studies can be used for parasitological monitoring of water bodies as well as control of the spread of ecto- and endoparasites. Practical value. The obtained results can be used for a timely understanding of trends in the spread of parasitic diseases and allows using the obtained material for parasitological monitoring of fish farms. Keywords: fish, carps, parasites, prevalence, infestation intensity.

Characterization and in vitro antibacterial activity of grass carp (Ctenopharyngodon idella) serum amyloid A

Serum amyloid A (SAA) predominantly synthesized by hepatocytes is a classical acute phase protein and has been extensively studied in mammals. However, the studies on the structure and properties of fish SAA are limited although SAA genes have been cloned and identified from various fishes. In the present study, a cDNA of grass carp (Ctenopharyngodon idella) SAA (gcSAA) was cloned and characterized, displaying a high homology with its counterparts in vertebrates. gcSAA mRNA was expressed with highest abundance in the liver and its levels were increased by a 24-hour infection of Aeromonas hydrophila (A. hydrophila) for more than 5 folds in the intestine, 15 folds in the spleen, 75 folds in the head kidney and 100 folds in the liver, implying that it is an acute phase protein in grass carp. Subsequently, recombinant gcSAA protein (rgcSAA) was prepared from a prokaryotic expression system after codon optimization of its coding sequence. The direct antibacterial activity assay and the plate count assay disclosed that gcSAA inhibited the growth and survival of A. hydrophila but not Edwardsiella piscicida (E. piscicida) which both are common bacterial pathogens in aquaculture. The propidium iodide (PI) uptake assay confirmed the bactericidal property of gcSAA, showing that it is able to enhance the uptake of PI in A. hydrophila but not E. piscicida. These findings revealed the molecular features of gcSAA and its roles in host defense against bacterial infection.

Comprehensive mRNA and microRNA analysis revealed the effect and response strategy of freshwater fish, grass carp (Ctenopharyngodon idella) under geosmin exposure

Geosmin is an environmental pollutant that causes off-flavor in water and aquatic products. The high occurrence of geosmin contamination in aquatic systems and aquaculture raises public awareness, however, few studies have investigated the response pathways of geosmin stress on freshwater fish. In this research, grass carp were exposed to 50 μg/L geosmin for 96 h, liver tissue was sequenced and validated using real-time qPCR. In total of 528 up-regulated genes and 488 down-regulated genes were observed, includes cytochrome P450 and uridine diphosphate (UDP)-glucuronosyltransferase related genes. KEGG analysis showed that chemical carcinogenesis-DNA adducts, metabolism of xenobiotics by cytochrome P450, drug metabolism-cytochrome P450 pathway was enriched. Common genes from the target genes of microRNAs and differential expression genes are enriched in metabolism of xenobiotics cytochrome P450 pathway. Two miRNAs (dre-miR-146a and miR-212–3p) down regulated their target genes (LOC127510138 and adh5, respectively) which are enriched cytochrome P450 related pathway. The results present that geosmin is genetoxic to grass carp and indicate that cytochrome P450 system and UDP-glucuronosyltransferase play essential roles in biotransformation of geosmin. MicroRNAs regulate the biotransformation of geosmin by targeting specific genes, which contributes to the development of strategies to manage its negative impacts in both natural and artificial environments.

Integrated multitrophic aquaculture in ponds using substrate for periphyton as natural source of food

As a productive and sustainable alternative to fish farmers, the present study aims to evaluate the use of substrate for periphyton growth in an Integrated Multitrophic Aquaculture (IMTA) with complementary species. The studied species were: Nile tilapia (Oreochromis niloticus), grass carp (Ctenopharyngodon idella) and curimbatá (Prochilodus lineatus). The experiment had four treatments with three replicates that evaluated the IMTAs: [T100] Cb:C – tilapia inside hapas fed on recommended feed, with grass carp and curimbatás outside the hapas making use of natural food; [T50] Cb:C – the same species distribution with tilapia fed 50 % of the daily amount of commercial diet. Cb:C 100 and Cb:C 50 – grass carp and curimbatás fed on recommended feed at two feeding rates (100% and 50%) with substrate for periphyton growth in the feeding restriction treatment. In phase II, tilapias were included in all the treatments as a complementary species. Growth performance of fish and physical-chemical parameters of water were evaluated. In the proposed models, the species were efficient in utilizing the feed and in nutrient cycling, achieving productivity of 6 t/ha in the system without water renewal. Inserting secondary and complementary species reduced the feed conversion ratio (FCR) to values of 0.95 in systems under feed restriction and 1.28 in the groups that received 100% of commercial feed. Considering the reduction of the FCR and the high productivity, farmers can diversify their products in the same area without increasing inputs.

Molecular characterization of the grass carp bscl2 gene and its expression response to lipid accumulation, nutritional status, insulin and glucagon

Bscl2 plays a role in lipid metabolism of mammals, however its role in teleost fish remains unclear. Using the grass carp (Ctenopharyngodon idella) as a model, the bscl2 gene was isolated from the brain and characterized. Thereafter, the tissue distribution of the gene was examined, before expression was analyzed as a function of fasting, refeeding, oral glucose administration and overfeeding. In addition, bscl2 mRNA levels were evaluated in grass carp primary hepatocytes treated with glucagon, insulin, oleic acid, and glucose. Results showed that the cloned bscl2 gene was 1341 bp, encoding 446 amino acids, and was highly expressed in the brain, heart, and gonad. Following oral glucose administration, bscl2 expression increased. Expression of bscl2 decreased in fasted fish but increased following refeeding. Overfeeding, which resulted in elevated lipid accumulation, also stimulated bscl2 expression. In primary hepatocytes, bscl2 levels were increased by glucose, oleic acid, and insulin treatments, and reduced by glucagon treatment. These data suggest that bscl2 may play an important role in nutrient metabolism in teleost fish.

The role of vitamin E in polyunsaturated fatty acid synthesis and alleviating endoplasmic reticulum stress in sub-adult grass carp (Ctenopharyngodon idella)

Vitamin E (VE) is an essential lipid-soluble vitamin that improves the fish flesh quality. However, the underlying molecular mechanisms remain unclear. This study aimed to investigate the effects of VE on growth performance and flesh quality in sub-adult grass carp (Ctenopharyngodon idella). A total of 450 fish (713.53 ± 1.50 g) were randomly divided into six treatment groups (three replicates per treatment) and fed for nine weeks with different experimental diets (dietary lipid 47.8 g/kg) that contained different levels of VE (5.44, 52.07, 96.85, 141.71, 185.66, and 230.12 mg/kg diet, supplemented as dl-α-tocopherol acetate). Notably, the treatment groups that were fed with dietary VE ranging from 52.07 to 230.12 mg/kg diet showed improvement in the percent weight gain, special growth rate, and feed efficiency of grass carp. Moreover, the treatment groups supplemented with dietary VE level of 141.71, 185.66, and 230.12 mg/kg diet showed enhancement in crude protein, lipid, and α-tocopherol contents in the muscle, and the dietary levels of VE ranging from 52.07 to 141.71 mg/kg diet improved muscle pH24h and shear force but reduced muscle cooking loss in grass carp. Furthermore, appropriate levels of VE (52.07 to 96.85 mg/kg diet) increased the muscle polyunsaturated fatty acid content in grass carp. Dietary VE also increased the mRNA levels of fatty acid synthesis-related genes, including fas, scd-1, fad, elovl, srebp1, pparγ, and lxrα, and up-regulated the expression of SREBP-1 protein. However, dietary VE decreased the expression of fatty acid decomposition-related genes, including hsl, cpt1, acox1, and pparα, and endoplasmic reticulum stress-related genes, including perk, ire1, atf6, eif2α, atf4, xbp1, chop, and grp78, and down-regulated the expression of p-PERK, p-IRE1, ATF6, and GRP78 proteins. In conclusion, dietary VE increased muscle fatty acid synthesis, which may be partly associated with the alleviation of endoplasmic reticulum stress, and ultimately improves fish flesh quality. Moreover, the VE requirements for sub-adult grass carp (713.53 to 1590.40 g) were estimated to be 124.9 and 122.73 mg/kg diet based on percentage weight gain and muscle shear force, respectively.

Glycerol tributylate (Triacylglycerol tributanoate) promoted the liver lipid metabolism by cultivating the intestinal flora of grass carp (Ctenopharyngodon idellus).

To investigate the effects of glycerol tributyrin (TB) (Triacylglycerol tributanoate) on the regulation of liver lipid metabolism by intestinal flora of grass carp (Ctenopharyngodon idellus). The compound feed with soybean oil 2.8% + fish oil 1.8%, soybean oil 6.3% + fish oil 1.8%, and soybean oil 6.2% + fish oil 1.8% + TB 0.1% was added to the basal diet as a fat source and fed to the basal (control) group, high lipid (HL) group, and tributyrin (TB) group for 12weeks. We tested the growth performance, fat content, diversity, and abundance of gut flora and other related indexes of grass carp by Soxhlet extraction, liver tissue enzyme activity, oil red O staining, and 16S rRNA high-throughput sequencing. The results showed that the liver fat number and liver fat content of grass carp in the TB group were lower than those in the HL group, while the fattening degree was significantly higher than those in the other two groups; according to the indices such as Shannon, Ace, and Coverage, it was found that the grass carp in the TB group had the highest abundance and diversity of intestinal microflora; at the portal level, Proteobacteria and Fusobacteria were the main dominant flora in the TB group, with the number of unique OUTs accounting for about 59. 9% of the total number measured; at the genus level, the relative abundance of lipase-producing, short-chain fatty acid-associated bacteria, such as Bacillus-Lactobacillus and Bifidobacterium, was significantly lower (p < 0.05). Thus, we conclude that the addition of TB to high-fat diets can alter the structure of the intestinal microbial community and promote hepatic lipid metabolism in grass carp. TB can alleviate fatty liver in grass carp by increasing the relative abundance of short-chain fatty acids in the intestine. Meanwhile, TB inhibits the conversion of primary bile acids to secondary bile acids in the host, which can block intestinal FXR signaling and the hepatic FXR-SHP pathway, thus slowing down fat synthesis and alleviating the accumulation of liver lipids in grass carp.