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Crucian carp (Carassius auratus) is widely distributed in the world and has become an economically freshwater fish. The population in Lake Dali Nur can tolerate the extreme alkaline environment with alkalinity over 50 mmol/L (pH 9.6), thus providing a special model for exploring alkali-tolerant molecular markers in an extremely alkaline environment. In this study, we constructed a high-density and high-resolution linkage map with 16,224 SNP markers based on genotyping-by-sequencing (GBS) consisting of 152 progenies and conducted QTL studies for alkali-tolerant traits. The total length of the linkage map was 3918.893 cM, with an average distance of 0.241 cM. Two QTLs for the ammonia-N-tolerant trait were detected on LG27 and LG45. A QTL for the urea-N-tolerant trait was detected on LG27. Interestingly, mapping the two QTLs on LG27 revealed that the mapped genes were both located in the intron of CDC42. GO functional annotation and KEGG enrichment analysis results indicated that the biological functions might be involved in the cell cycle, cellular senescence, MAPK, and Ras signaling pathways. These findings suggest that CDC42 may play an important role in the process of dealing with extremely alkaline environments. [ABSTRACT FROM AUTHOR]

Phenotypic differences between diploid parents and their allotriploid offspring are common in aquaculture breeding. Some allotriploid populations exhibit rapid growth rates and increased body weight, which are significant for supporting fisheries development. Understanding the genetic mechanisms underlying these traits is crucial for implementing diverse breeding strategies to achieve high production in fish farming. Here, we collected the following fish species for our study: red crucian carp (Carassius auratus red var., 2nRR), common carp (Cyprinus carpio L., 2nCC), and two allotriploids (3nR2C and 3 nRC2). These allotriploids were obtained through backcrossing an allotetraploid of C. auratus red var. x C. carpio L. (4nR2C2, ♂) with C. auratus red var. and C. carpio L. (♀), respectively. These allotriploids demonstrated faster growth rates compared to their diploid inbred parents, contributing to the Chinese fisheries industry for several decades. We conducted a systematic comparison of mitochondrial DNA (mtDNA) copy numbers in the liver and muscle tissues of 2nRR, 2nCC, 3nR2C, and 3 nRC2 under different seasons. When entering winter (low water temperature: 13 °C), the triploid fish (3nR2C and 3 nRC2) exhibited lower mtDNA copy numbers in the muscle, indicating a reduction in individual activity and energy expenditure to facilitate weight maintenance when food availability is limited. Furthermore, we analysed the expression levels of three nuclear-regulated mitochondrial genes (tfam, tfb1m, and tfb2m) and observed an imbalance of allelic expression in tfam and tfb1m in the two triploid fish. These findings enhance our understanding of the molecular regulatory mechanisms underlying growth trait differences among fish with different ploidy levels. [ABSTRACT FROM AUTHOR]

Microbial infection can pose a great threat to health of farmed fish. This study aimed to investigate the probiotic characteristics of Bacillus cereus strain fkW8-1-2 isolated from intestine of WCC and its anti-biofilm activity against pathogenic bacteria. The strain fkW8-1-2 showed a high resistance to low pH, bile salt and lysozyme during long-term incubation. The strain fkW8-1-2 displayed a gradual increase of cell surface hydrophobicity with various forms of hydrocarbons. The strain fkW8-1-2 showed the remarkable autoaggregation and coaggregation activity with A. hydrophila L3-3 and E. tarda 1l-4. The culture medium (CM) and cell-free supernatants (CFS) of strain fkW8-1-2 at 48 h cultivation could attenuate biofilm formation of A. hydrophila and E. tarda with the maximum inhibition rates. In addition, the intact cells of strain fkW8-1-2 exhibited the strong antioxidant activity for DPPH removal and superoxide anion clearance. These results indicated that strain fkW8-1-2 possessing probiotic characteristics can pose a protective role in health of farmed fish. [ABSTRACT FROM AUTHOR]

Nonylphenol (NP) is a known endocrine-disrupting chemical (EDC) that has been shown to affect bone development in mammals. However, the detrimental impacts of NP on the skeletal growth and development of aquatic species, especially bony fish, remain poorly understood. Bone morphogenic proteins (BMPs), essential for bone formation and osteoblast differentiation, act through the BMP-Smad signaling pathway. In this study, two BMP genes, BMP2 and BMP4, were cloned and characterized in the red crucian carp (Carassius auratus red var.). The full-length cDNAs of BMP2 and BMP4 were 2029 bp and 2095 bp, respectively, encoding polypeptides of 411 and 433 amino acids, and share a typical TGF-β domain with other BMPs. The tissue expression patterns of both genes were identified, showing ubiquitous expression across all studied tissues. Additionally, the exposure of embryos or adult fish to NP stress resulted in a downregulation of BMP2, BMP4, and other genes associated with the BMP-Smad signaling pathway. Moreover, the combined treatment of adult fish with NP and the specific BMP receptor inhibitor significantly reduced these genes' expression. These findings elucidate the mechanism of NP stress on BMP2 and BMP4, suggesting a role for the BMP-Smad signaling pathway in the response to endocrine-disrupting chemicals in fish. [ABSTRACT FROM AUTHOR]

The coexistence of sexual and asexual lineages is rarely documented in vertebrates. Various ecological and evolutionary mechanisms have been proposed to explain their stable coexistence. Gibel carp (Carassius gibelio), a highly invasive freshwater fish in Europe, is one such example of a sexual and asexual vertebrate, combining gynogenesis (sperm-dependent parthenogenesis) and sexual reproduction. In this study, we focused on vigour-related traits in gynogenetic and sexual forms of gibel carp coexisting in the same habitat, to reveal whether there is a link between parasite load and vigour-related traits reflecting the potential advantage of one reproductive form over another, which may eventually facilitate the obligatory coexistence of sperm-dependent gynogenetic females with sexual males. Using physiological parameters (indexes of somatic condition, energetic condition, and reproductive performance; glucose levels; and erythrocytes-related variables), diploid sexual males, diploid sexual females, and triploid gynogenetic females were found to be differentiated from one another. However, based on immune variables representing innate immunity, specific immunity, and index of immunocompetence, mostly sexual males were found to be weakly differentiated from both groups of females. We revealed different patterns of interactions between parasite abundance and immune variables between sexual and gynogenetic forms. Using parasite assemblage composition, different relationships between parasite assemblage and immunity or physiology in sexual males and sexual females were evidenced, potentially related to male reproduction biology. In contrast, gynogenetic females exhibited the advantage that parasite assemblage composition did not affect their immunity or physiology. Our study suggests that reproduction mode-associated costs of physiology and immunity may facilitate the coexistence of the asexual-sexual complex. We highlight that multiple ecological processes and evolutionary mechanisms contribute to the coexistence of asexual and sexual gibel carp. [ABSTRACT FROM AUTHOR]

The swim bladder in some teleost fish functions to transfer the sound energy of acoustic stimuli to the inner ears. This study uses the auditory evoked potential tests, micro-computed tomography scanning, reconstruction, and numerical modeling to assess the contribution of the swim bladder to hearing in crucian carp (Carassius carassius). The auditory evoked potential results show that, at the tested frequency range, the audiogram of fish with an intact swim bladder linearly increases, ranging from 100 to 600 Hz. Over this frequency, the sound pressure thresholds have a local lowest value at 800 Hz. The mean auditory threshold of fish with an intact swim bladder is lower than that of fish with a deflated swim bladder by 0.8–20.7 dB. Furthermore, numerical simulations show that the received pressure of the intact swim bladders occurs at a mean peak frequency of 826 ± 13.6 Hz, and no peak response is found in the deflated swim bladders. The increased sensitivity of reception in sound pressure and acceleration are 34.4 dB re 1 μPa and 40.3 dB re 1 m·s−2 at the natural frequency of swim bladder, respectively. Both electrophysiological measurement and numerical simulation results show that the swim bladder can potentially extend hearing bandwidth and further enhance auditory sensitivity in C. carassius. [ABSTRACT FROM AUTHOR]

Carassius auratus herpesvirus (CaHV) is a pathogen isolated from crucian carp (Carassius auratus) associated with high mortality. A diagnosis method that can detect the virus at an early stage, specifically and accurately, is an urgent requirement for the prevention of CaHV transmission. In the present study, a droplet digital PCR (ddPCR) method based on the tumor necrosis factor receptor (TNFR) gene was established to detect and quantify CaHV DNA with high specificity and no cross-reactions with other aquatic viruses. Skin mucus samples were collected from infected crucian carp from Day 1-8 after infection, and positive amplification was detected on the first day by ddPCR (0.54 copies/μL), whereas the presence of CaHV was not detected by routine PCR until Day 6. Tissue DNA was then collected from the head kidney of 20 fishes which were injected with CaHV and died during the experiment. The five negative samples checked by routine PCR were detected by ddPCR and real-time PCR (qPCR), respectively. The results showed that the positive detection rate of ddPCR (100%) was higher than that of qPCR (40%). The detection limit of the ddPCR was found to be 0.52 copies/μL, which was much lower than the 50.12 copies/μL determined by qPCR. Overall, ddPCR offers a highly promising diagnosis method for the absolute quantification of CaHV in carrier fish and samples from the skin mucus and head kidney with low viral concentrations. [ABSTRACT FROM AUTHOR]

Frequent outbreaks of emerging infectious diseases in fish, such as Carassius auratus herpesvirus (CaHV) infection has caused great economic losses in China. However, the lack of a sensitive cell culture system has limited studies of CaHV. In the present study, a new cell line (gibel carp skin cell, GiCS) derived from gibel carp (Carassius gibelio) skin tissue was established to create a valuable tool for research of the virus. The GiCS cells consisted mainly of epithelial-like cells, which grew well at 25 °C in L-15 medium supplemented with 10-20% fetal bovine serum. Chromosomal analysis revealed that the skin cell line remained amphitriploid, with most chromosome counts being 156 (54%). The GiCS cells can be efficiently transfected and expressed exogenous genes. In particular, the GiCS cells showed high susceptibility to CaHV infection, which was confirmed by virus infection tests, detection of viral gene expression, and ultrastructural observation. To our knowledge, it is the first cell line that is highly permissive to CaHV infection. In addition, the cells also showed susceptibility to several aquatic animal viruses from different families including Iridoviridae, Rhabdoviridae, and Reoviridae. In conclusion, these results indicated that the establishment of the GiCS cell line is a significant advance that will be beneficial to future studies of CaHV and other aquatic animal viruses. [ABSTRACT FROM AUTHOR]

An 8-week feeding experiment aimed to investigate the effects of fermented soybean residue in diets on the growth performance, serum antioxidant parameters, intestinal digestive capacity, and microbial composition of the hindgut of Furong crucian carp. The feeds were formulated to contain 0%, 6%, 12%, 18%, and 24% fermented soybean residue (CON, FSR6, FSR12, FSR18, and FSR24, respectively), respectively, to form five diets (crude protein: 33%; crude lipid: 5%). The results showed that incorporating 6% fermented soybean residue into the diet significantly increased the weight gain rate (WGR) and specific growth rate (SGR) and decreased the feed coefficient rate (p < 0.05). Through regression analysis of WGR and SGR, the optimal levels of the dietary fermented soybean residue of Furong crucian carp were determined to be 6.78% and 7.06%. Incorporating fermented soybean residue into the diet decreased the lipid content of the whole body and the levels of glucose, total cholesterol, and triglyceride in the serum of Furong crucian carp. The inclusion of 6% and 12% fermented soybean residue in the diet markedly increased the antioxidant capacity, intestinal amylase activity, and intestinal villous height of Furong crucian carp (p < 0.05). At the 6% level, fermented soybean residue significantly increased the abundance of Romboutsia and Clostridium_sensu_stricto_1 while significantly decreasing the abundance of Vibrio (p < 0.05), indicating that a 6% level of fermented soybean residue was beneficial for intestinal health. In conclusion, incorporating 6–7% fermented soybean residue into the diet of Furong crucian carp was recommended. [ABSTRACT FROM AUTHOR]

The trial was conducted to investigate the effects of the replacement of dietary fishmeal (FM) by the blend of Tenebrio molitor meal (TMM), Chlorella meal (CM), Clostridium autoethanogenum protein (CAP), cottonseed protein concentrate (CPC) on growth, protein utilization and intestinal health of gibel carp (Carassius gibelio, CAS Ⅴ). The FM-based diet was used as the control, and the blended proteins (TMM: CM: CAP: CPC) at ratios of 1 : 1:8 : 2 (BLEND A), 1 : 1:6 : 4 (BLEND B), and 1 : 1:4 : 6 (BLEND C) were used to replace FM at three levels (33%, 67%, 100%), respectively. The results showed that, compared to the control group, growth performance increased significantly when dietary FM was fully replaced by BLEND B (P < 0.05), while decreased by BLEND A (P < 0.05). The complete substitution of FM with BLEND B significantly upregulated the mRNA expression of intestinal proinflammatory cytokines, anti-inflammatory cytokines, and tight junction-related genes (P < 0.05), improving intestinal tissue morphology and health. And it also significantly increased intestinal trypsin activity (P < 0.05), upregulated the mRNA expression of amino acid sensory receptor-related and amino acid or peptide transport-related genes (P < 0.05), increased protein apparent digestibility coefficient (P < 0.05). The 100% substitution of FM with BLEND A significantly upregulated the mRNA expression of intestinal proinflammatory cytokines and downregulated the mRNA expression of anti-inflammatory cytokine il-10 (P < 0.05), reduced intestinal villus height (P < 0.05), and decreased protein apparent digestibility coefficient (P < 0.05). In conclusion, BLEND B could completely substitute dietary FM and was beneficial to the growth and health of gibel carp. Dietary digestible essential amino acids index (DEEAI) was found as an important indicator and should be higher than 79.5% to meet the maximum growth of fish. [ABSTRACT FROM AUTHOR]

Successful invasive non-native fish species can cause enormous damage to native biodiversity. In mainland Europe, the introduction of the gibel carp (Carassius gibelio) has led to a decline in populations of the formerly widespread native crucian carp (C. carassius). Both invasive and native species develop two phenotypes, namely stunted and deep-bodied, which depend on the intensity of competition and predation in the water body. The deep-bodied phenotype is associated with a more diverse fish community composition, can attain large sizes and is very attractive to recreational anglers. This study analysed trends in the record sizes of native crucian carp and invasive gibel carp (individuals close to the maximum attainable size of the species) reported by recreational anglers over the last 50 years in Czechia, recording the invasion of gibel carp from its beginnings to the fully established population phase. The study provides circumstantial evidence that gibel carp is behind transition from the relative abundance of large crucian carp to near extirpation, while large gibel carp have taken over the reports of record catches in the genus Carassius. This indicates that the crucian carp, which is currently classified as critically endangered in the Red List of Czechia, has very limited possibilities to realise its deep-bodied phenotype. It also shows the potential of using data from recreational anglers for mapping invasion processes and as a source of relatively localised information on endangered species. [ABSTRACT FROM AUTHOR]

Fishes of the genus Carassius are useful experimental vertebrate models for the study of evolutionary biology and cytogenetics. Carassius demonstrates diverse biological characteristics, such as variation in ploidy levels and chromosome numbers, and presence of microchromosomes. Those Carassius polyploids with ≥ 150 chromosomes have microchromosomes, but the origin of microchromosomes, especially in European populations, is unknown. We used cytogenetics to study evolution of tandem repeats (U1 and U2 small nuclear DNAs and H3 histone) and microchromosomes in Carassius from the Czech Republic. We tested the hypotheses whether the number of tandem repeats was affected by polyploidization or divergence between species and what mechanism drives evolution of microchromosomes. Tandem repeats were found in tetraploid and hexaploid Carassius gibelio , and tetraploid Carassius auratus and Carassius carassius in conserved numbers, with the exception of U1 small nuclear DNA in C. auratus. This conservation indicates reduction and/or loss in the number of copies per locus in hexaploids and may have occurred by divergence rather than polyploidization. To study the evolution of microchromosomes, we used the whole microchromosome painting probe from hexaploid C. gibelio and hybridized it to tetraploid and hexaploid C. gibelio , and tetraploid C. auratus and C. carassius. Our results revealed variation in the number of microchromosomes in hexaploids and indicated that the evolution of the Carassius karyotype is governed by macrochromosome fissions followed by segmental duplication in pericentromeric areas. These are potential mechanisms responsible for the presence of microchromosomes in Carassius hexaploids. Differential efficacy of one or both of these mechanisms in different tetraploids could ensure variability in chromosome number in polyploids in general. [ABSTRACT FROM AUTHOR]

In previous studies, an allodiploid lineage (WR-F1-F5) was established by the distant hybridization of white crucian carp (Carassius cuvieri, WCC, ♀) and red crucian carp (Carassius auratus red var., RCC, ♂), an allodiploid fish (WR-II) was produced by WR-F1 (♀) x WCC (♂). In this study, the nutrients in the muscle and ovary of WR-II and its parents (WCC, RCC, and WR) were investigated, including protein, fat, amino acid, docosahexaenoic acid (DHA), moisture, and ash. The results showed that the protein content of WR-II in muscle and ovary (17.90 % and 25.60 % respectively) was higher than that of WR, and was significantly higher than that of WCC and RCC (p < 0.05). The fat content of WR-II in muscle and ovary (4.30 % and 5.31 % respectively) was higher than that of WR and was significantly higher than that of WCC and RCC (p < 0.05), and the muscle and ovary of WR-II showed rich DHA content (0.32 % and 0.54 % respectively) than that of WCC and RCC (p < 0.05). Fifteen amino acids were detected in WR-II and its parents, the total amino acid (TAA) content of WR-II in muscle and ovary (15.49 % and 18.43 % respectively) was significantly higher than that of WCC (p < 0.05), the delicious amino acid (DAA) content of WR-II in muscle and ovary (6.56 % and 8.29 % respectively) was different degrees higher than that of WCC, RCC, and WR. The moisture and carbohydrates of WR-II in muscle and ovary were lower than those in WCC and RCC. Furthermore, protein, fat, TAA, and DAA content in the ovary were significantly higher than those in muscle (p < 0.05), showing tissue differences in all detected fish. This study indicated that WR-II had the characteristics of high protein, high fat, high DHA, high TAA, high DAA, low moisture, and low carbohydrates, which provided theoretical support for its application. [ABSTRACT FROM AUTHOR]

Crucian carp (Carassius auratus gibelio), an extensively cultivated freshwater fish, was one of the model species for the study of fish immunology. Polyclonal antibodies were advantageous molecular tools for studying teleost immune system. Specifically, polyclonal antibodies reacting with immunoglobulins (Ig) were used successfully in studies of the teleost fishes. In the present study, we produced polyclonal antibody against CH2 domains of crucian carp IgM, and measured the in vivo dynamics of IgM mRNA caused by CyHV-2 infection. The recombinant protein IgM with relative molecular weight about 53 KD was correctly expressed in prokaryotic cells. The specificity of the polyclonal antibody was evaluated by Western blotting and results revealed that the antibody not only specifically recognized crucian carp serum but also cross-reacted with grass carp serum. Quantitative RT-PCR analysis demonstrated the expression of IgM mRNA changed significantly after CyHV-2 infection. The expression of IgM in the kidney increased and reached a maximum at 6 h post-infection (hpi), while dropped to a low level at 5 days post-infection (dpi). In conclusion, the expression of IgM was significantly upregulated in the kidney of crucian carp infected with CyHV-2, indicating that IgM played a potential role in systemic immunity against viral infection. Polyclonal antibody against crucian carp IgM had certain clinical relevance, which might provide insight into the early stage of virus infection and prevention of the disease. [ABSTRACT FROM AUTHOR]

Aquatic products are good sources of essential nutrients, but the presence of pyrethroids (PYRs) as contaminants may pose risks to consumer health as the intricate matrices of PYRs usually obstruct chemical hazard detection. In this study, a gas chromatographic method was established and validated for simultaneously detecting residues of seven PYRs (cyhalothrin, permethrin, cyfluthrin, cypermethrin, tau-fluvalinate, fenvalerate, deltamethrin) in aquatic products. The aim of this method was to assess better the potential risks of pesticide residues in aquatic products. The PYRs in aquatic products were extracted with acetonitrile, purified with n-hexane saturated with acetonitrile, and cleaned up on a Cleanert® Alumina N column. Statistical analysis and orthogonal array experimental design were used to optimize the key parameters. To validate the proposed method, commonly consumed aquatic products (such as carp, crucian carp, whiteleg shrimp, river crab, sea cucumber, and scallop) were obtained from local supermarkets in Shanghai. Satisfied linearity of the calibration curves was achieved in a matrix-matched standard solution, with a correlation coefficient (R2) larger than 0.995. The average recoveries at five fortification levels varied from 77.0% to 117.2%, with relative standard deviations (RSDs) below 11.1%. Concerning electron capture detection, the limits of detection (LOD) and limits of quantification (LOQ) were 2.0–5.0 µg/kg and 5.0–10.0 µg/kg, respectively. These results demonstrate the high stability and sensitivity of this method for simultaneously detecting PYRs in aquatic products, having great practicability and which can be popularized easily. [ABSTRACT FROM AUTHOR]

A 56-day feeding trial was conducted to evaluate the effect of different dietary protein sources on the growth performance, muscle flavor substances, and quality structure of Triploid Crucian Carp. Three isonitrogenous (32.00%), isolipidic (8.00%), and isoenergetic (18.00 MJ kg−1) practical diets were formulated. These diets consisted of fishmeal as the animal-derived protein source (AP), a combination of soybean meal and rapeseed meal as the plant-derived protein source (PP), and a mixture of fishmeal, soybean meal, and rapeseed meal as the mixed protein source (MP). Each diet was randomly assigned to triplicate tanks of fish and each tank was stocked with 25 fish (11.5 ± 0.4 g). The fish were fed until apparent satiation twice a day. The results showed a significant enhancement in the growth performance of Triploid Crucian Carp in the AP group compared with both the MP and PP groups (p < 0.05). Dietary plant derived protein can remarkably reduce the crude lipid content and increase the moisture content of the whole body and the dorsal muscle (p < 0.05). The antioxidant ability of fish in the PP group and MP group was better than that in the AP group (p < 0.05). Regarding free amino acids composition of muscle, the contents of glycine, methionine, and lysine were significantly enhanced in the AP group, while the histidine content was significantly increased in the PP group (p < 0.05). In terms of texture, dietary plant protein significantly improved the muscular hardness, gumminess, and chewiness. The activities of intestinal trypsin and alkaline phosphatase (ALP) of fish in the PP group were significantly higher than that in the AP group (p < 0.05). The expression levels of hepatopancreas TOR and IGF1 genes in the PP group were significantly higher than that in the MP group (p < 0.05). The present results indicate dietary fishmeal significantly improved the growth performance and muscular flavor glycine content, while dietary plant-based protein increased crude protein content, antioxidant ability, and muscular texture performance of Triploid Crucian Carp. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effects of vitamin E addition to the water column on immune response, antioxidant capacity, and liver tissue structure of crucian carp (Carassius auratus) under acute cold stress. Crucian carp was placed in the aqueous solution of control group (E1), negative control group (E2), and 100 mg/L vitamin E (E3) and cooled from 20 to 5°C by cold acclimation intelligent cooling device. Samples were taken at three temperature points of 20, 10, and 5°C, respectively, and the samples were detected and analyzed. The results showed that the content of each index increased under acute cold stress. The contents of white blood cell, red blood cell, hemoglobin, platelet, lysozyme, and glutathione peroxidase in E3 treatment group were significantly lower than those in E1 and E2 treatment groups (P < 0.05). The contents of cholinesterase, alkaline phosphatase, acid phosphatase, hydrogen peroxide, superoxide anion, superoxide dismutase, peroxidase, and malondialdehyde in E3 treatment group were significantly lower than those in E1 and E2 treatment groups (P < 0.01). Under acute cold stress, the liver tissue structure of crucian carp also changed, such as hepatocyte vacuolization, and the damage degree of E3 treatment group was lower than that of E1 and E2 treatment groups. In summary, the addition of vitamin E in water to treat crucian carp can reduce the harm caused by acute cold stress to its body and provide a theoretical reference for the application of vitamin E in water to alleviate fish stress. [ABSTRACT FROM AUTHOR]

Background: Amphora coffeaeformis, a unicellular diatom, can significantly accumulate lipids under nitrogen (N) limitation. However, the molecular mechanism underlying lipid accumulation in A. coffeaeformis remains unknown and its application development is lagging. Results: This work analyzed the lipid composition of A. coffeaeformis under N deprivation and investigated its mechanism underlying lipid accumulation using RNA-seq. The results showed that the total lipid content of A. coffeaeformis increased from 28.22 to 44.05% after 5 days of N deprivation, while the neutral lipid triacylglycerol (TAG) content increased from 10.41 to 25.21%. The transcriptional profile showed that N deprivation induced wide-ranging reprogramming of regulation and that most physiological activities were repressed, while the upregulation of glycerol-3-phosphate acyltransferase directly determined TAG accumulation. Moreover, we explored the effect of A. coffeaeformis as a food additive on the lipid composition of crucian carp. The results showed that the contents of unsaturated fatty acids in the meat of fish supplemented with A. coffeaeformis were significantly increased, indicating its potential application in animal nutrition for improving meat quality indicators. Conclusion: The findings shed light on the molecular mechanisms of neutral lipid accumulation and revealed the key genes involved in lipid metabolism in A. coffeaeformis. Moreover, we also confirmed that A. coffeaeformis can be used as feed additive for improving the lipid composition of crucian carp meat, which provided evidence for the biotechnology application of this high-oil microalgae. [ABSTRACT FROM AUTHOR]

TNFα belongs to superfamily of tumor necrosis factor that can exert the pleiotropic effort in a large quantity of biological processes, including immune homeostasis, intracellular modulation and etiopathogenesis, but its regulatory role in mucosal immune regulation of fish is unclear. Currently, this study aimed to evaluate the immunoregulatory function of TNFα1 on gut barrier in teleost fish. In this study, TNFα1 sequences were identified from red crucian carp (RCC, Carassius auratus red var). The high-level expression of RCC-TNFα1 mRNA was detected in gill among all the isolated samples. Then, RCC-TNFα1 expression increased dramatically in immunerelated tissues after A. hydrophila infection and in cultured fish cells after lipopolysaccharide (LPS) treatment. RCC-TNFα1 fusion protein was generated and purified in vitro. RCC receiving RCC-TNFα1 perfusion showed an increased levels of villi fusion and edema in injured midgut with the fuzzy appearance. In addition, The mRNA expressions of tight junction (TJ) genes, mucin genes and redox sensitive genes decreased sharply in TNFα1-treated midgut in comparison with those of the control (P < 0.05), whereas the expression levels of apoptotic genes involved in caspase signals and unfolded protein response (UPR) attained the dramatic increase. These results demonstrated that RCC-TNFα1 stimulation could impair midgut structural integrity and immune function by induction of antioxidant collapse and apoptotic activation. [ABSTRACT FROM AUTHOR]

This research aims to identify the hub genes associated with the senescence of triploid caudal fin cells. Transcriptomic data are obtained from the high and low generation (P6, P60) of triploid crucian carp caudal fin cells by high-throughput sequencing technology. Initially, all differential genes between the high and low generations are screened, yielding 4140 significantly upregulated genes and 3724 significantly downregulated genes. Subsequently, an aging gene set containing 950 genes is downloaded from the CellAge database to extract the differentially expressed genes associated with caudal fin cell aging, totaling 29 genes. GO and KEGG enrichment analyses are performed on these 29 aging differential genes. The GO analysis shows enrichment mainly in cellular processes related to aging, such as regulation of cell division, chromatin organization, cell cycle regulation. KEGG analysis reveals that the 29 aging-related genes are primarily involved in cell cycle and cellular senescence pathways. A PPI network of aging-related genes is constructed using the STRING database and Cytoscape software. Top-ranked genes were identified by using Degree, MCC, MNC, and Closeness algorithms in the Cytohubba plugin in Cytoscape, resulting in hub genes EZH2, JUN, MYD88, RBL2, BMP4, CCND1, NFKB2, MMP9. Lastly, qRT-PCR validation of these eight hub genes further confirmed the involvement of four genes: EZH2, RBL2, BMP4, and CCND1. The hub gene screened in this study may become a potential biomarker of fish caudal fin cell senescence, which provides a valuable experimental basis for the senescence of fish caudal fin cells, especially the senescence of caudal fin cells in polyploid fish, and the reproduction and breeding improvement of polyploid fish. It also provides meaningful data for elucidating the molecular mechanism of polyploid formation in animals, as well as the formation of aging and tumour in human beings. [ABSTRACT FROM AUTHOR]

In the scope of this study, fish fauna of Küçük Menderes River and its tributaries, updated with the comparison of the recent ichthyofaunal studies, as well as the length-weight relations (LWR) and condition factors (CF) were estimated for 7 freshwater fish species belonging to six families from the river basin: endemic Oxynoemacheilus eliasi, Cobitis fahireae; invasive, Carassius gibelio, Atherina boyeri, transloce Perca fluviatilis and the native Squalius fellowesii, Cyprinus carpio. The fish samples were collected with various fishnets and DC electro-fishing devices from six stations in 2018 and 2019. The LWR of the fishes was studied based on 379 specimens. The estimated values of parameter b ranged from 2.884 (A. boyeri) to 3.176 (C. fahireae). The coefficient of determination (R2) was changed between 0.792 to 0.980 for all sampling localities. In the study, Fulton's condition factor ranged between 0.391 (S. fellowesii) to 3.080 (S. fellowesii); the relative condition factor ranged between 0.346 (O. eliasi) to 2.746 (S. fellowesii), respectively. This research is anticipated to contribute valuable insights for the conservation of the species, while also furnishing essential data to inform future fisheries management studies in the region. [ABSTRACT FROM AUTHOR]

Biological materials have properties like great strength and flexibility that are not present in synthetic materials. Using the ribs of crucian carp as a reference, we investigated the mechanisms behind the high mechanical properties of this rib bone, and found highly oriented layers of calcium phosphate (CaP) and collagen fibers. To fabricate a fish-rib-bone-mimicking membrane with similar structure and mechanical properties, this study involves (1) the rapid synthesis of plate-like CaP crystals, (2) the layering of CaP–gelatin hydrogels by gradual drying, and (3) controlling the shape of composite membranes using porous gypsum molds. Finally, as a result of optimizing the compositional ratio of CaP filler and gelatin hydrogel, a CaP filler content of 40% provided the optimal mechanical properties of toughness and stiffness similar to fish bone. Due to the rigidity, flexibility, and ease of shape control of the composite membrane materials, this membrane could be applied as a guided bone regeneration (GBR) membrane. [ABSTRACT FROM AUTHOR]

Efficient detection and degradation of fungicides are greatly concerned with aquatic food safety. Herein, a multifunction CoFe2O4/MoS2@Au (ACMS) composite was synthesized for crystal violet (CV) and malachite green (MG) photocatalytic degradation and SERS determination. As the construction of the Z-scheme heterostructure of ACMS, which enhanced the light absorption capability and the separation efficiency of photoexcited carrier significantly, ACMS possessed an excellent photocatalytic performance with a degradation rate of 94.76% for CV under simulated solar light irradiation. Furthermore, the multifunction ACMS exhibited superior SERS capability with a detection limit (LOD) of 4.309 × 10−2 μg L−1 for MG residues in water. And the ACMS substrates could be utilized to determine the MG residues in crucian carp extract, resulting in a recovery rate of 96.00~116.00%. In addition, such multifunction heterojunctions were performed for in situ monitoring of the photodegradation process. This research opened up a novel perspective on the applications of heterojunction-based multifunction materials for food safety control. [ABSTRACT FROM AUTHOR]

Gut microbiome plays an important role in host's development and reproduction. Lotus-fish co-culture (LFC) is a popular integrated agriculture-aquaculture farming system in China. However, there is still a relative dearth of information on how changes of aquaculture modes will affect the fish gut microbiome. In the present study, metagenomic sequencing was used to compare gut bacteria of the hybrid fish Hefang crucian carp (Carassius cuuieri ♀ × C. auratus var. red ♂) cultured in LFC and intensive pond culture (IPC) systems. The results indicated that aquaculture modes exerted great influences on the fish gut bacterial community. A significantly higher gut bacterial diversity was found in LFC than that in IPC (P < 0.05). The relative abundances of Actinobacteria and Chloroflexi were apparently higher in LFC than those in IPC, whereas Planctomycetota, Firmicutes, and Verrucomicrobia showed opposite patterns. Besides, gut bacterial metabolic potentials involved in energy metabolism, carbohydrate metabolism, amino acid metabolism, environmental information processing, and cellular processes were significantly increased in LFC compared to those in IPC. On the contrary, the bacterial functional potentials related to nucleotide metabolism, DNA mismatch repair, as well as homologous recombination were significantly stimulated in the IPC system. Source-tracking analysis suggested that fish gut bacterial community in IPC was originated mainly from water sources, whereas the gut bacterial community in LFC was originated from more unknown sources and soil sources. Our results provided new insight into the influence of aquaculture modes on the microbial community diversity and functionality in aquatic animals and highlighted the importance of environment microbiome in reshaping the gut microbes. [ABSTRACT FROM AUTHOR]

A 60-day feeding trial was conducted to investigate the influence of glutathione (GSH) on growth performance, lipid metabolism and muscle quality of hybrid crucian carp (initial body weight: 15.03 ± 0.11 g) fed a high-fat diet (HFD). Five experimental diets were prepared in this study: the control diet (6.17% fat), HFD (12.37% fat), and HFD with 200 mg/kg, 400 mg/kg and 600 mg/kg GSH supplementation, respectively. The results indicated that feeding HFD to hybrid crucian carp remarkably reduced weight gain rate (WGR), specific growth rate (SGR), total antioxidant capacity (T-AOC) and total superoxide dismutase (T-SOD) activities of serum and liver, glutathione peroxidase (GSH-Px) and glutathione reductase (GR) activities of liver, but significantly increased malondialdehyde (MDA) content of liver compared to the control group. After adding 200-600 mg/kg GSH to HFD, the WGR, SGR, as well as serum and liver T-AOC activity of hybrid crucian carp increased significantly. Moreover, the supplementation of 400 mg/kg GSH significantly increased the activities of T-SOD, catalase (CAT) of serum and liver, as well as the GSH-Px, glutathione-S-transferase (GST) and GR of liver, but decreased MDA content of serum and liver compared to the HFD. The HFD significantly increased muscle crude lipid, polyunsaturated fatty acids (PUFA) contents and fiber diameter, but decreased chewiness, gumminess, hardness and fiber density compared to the control group. The addition of 400-600 mg/kg GSH significantly increased muscle chewiness, gumminess, hardness, and decreased muscle fiber diameter of HFD-fed hybrid crucian carp. Meanwhile, the addition of 200-600 mg/kg GSH significantly reduced the mono-unsaturated fatty acids (MUFA) content and increased the PUFA content of muscle compared to the HFD. The HFD significantly up-regulated the expression of lipid synthesis genes (dgat2 and srebp1) and down-regulated the expression of lipolysis genes (lpl, hsl and acox1) of liver compared to the control group. The addition of 400-600 mg/kg GSH significantly decreased the expression of lipid synthesis genes (dgat2 and srebp1) and increased the expression of lipolysis genes (hsl, lpl, acox1 and ppara) of HFD-fed hybrid crucian carp. This study demonstrated that GSH effectively ameliorated the decline of growth performance and muscle quality of hybrid crucian carp caused by HFD, and reduced the risk of liver lipid deposition of hybrid crucian carp by regulating the expression of genes related to liver lipid metabolism. [ABSTRACT FROM AUTHOR]

MnSOD is a ubiquitous metalloenzyme that constitutes the first line of antioxidant defense against oxidative stress. In this study, full length sequence of MnSOD was identified from hybrid crucian carp (WR, Carassius cuvieri ♀ × Carassius auratus red var ♂). Tissue-specific analysis revealed that the highest expression of WR-MnSOD was detected in kidney. Aeromonas hydrophila challenge could dramatically enhance WR-MnSOD mRNA expression in tissues. In vivo administration of purified WR-MnSOD peptide could maintain gut mucosal barrier function, rescue redox balance as well as decrease apoptotic cell death in midgut upon bacterial infection, suggesting that WR-MnSOD is playing a crucial role in gut mucosal barrier function and could be used as feed additive to improve gut immunity in fish. [ABSTRACT FROM AUTHOR]

Heavy metal toxicity is a significant threat to human health and the environment. Contamination of the food chain with heavy metals in water sources may impact the health of consumers adversely. This study aimed to determine the concentrations of Pb, Cd, Cr, Cu, and Zn in the invasive fish species Carassius gibelio inhabiting two important lakes in Türkiye: Lake Beyşehir and Lake Eğirdir, from the Lake District Region and assess any health risks posed by the consumption of these species. For this purpose, C. gibelio species were obtained from two lakes in dry and rainy seasons and heavy metal concentrations were determined via ICP-OES analyses. The Cd concentrations in the muscle samples obtained from both lakes were below the analysis limits. The mean heavy metal concentrations (mg/kg) in the Beyşehir and Eğirdir lake samples were found as Pb: 0.32, Cr: 0.09, Cu: 0.52, and Zn: 6.88 and Pb: 0.88, Cr: 0.08, Cu: 0.46, and Zn: 12.6, respectively. The average heavy metal concentrations in the muscle tissues were below the national/international legislation limits, and the estimated daily intake (EDI), target hazard quotients (THQs), total THQs (TTHQs), and carcinogenic rates (CRs) did not exceed these limits. The results suggested that the consumption of these invasive fish species from these two lakes might not pose any potential health risk for consumers. Transference values (TF) for the digestive tract were also calculated, and biomagnification was determined for Pb, Cd, and Cr. Risk assessment studies are very important in terms of evaluating the effects of fish consumption on human health via applying different indices. This is the first study in which heavy metal concentrations were determined simultaneously in Lake Beyşehir and Lake Eğirdir, and the public health risk of consuming their invasive fish species was estimated. [ABSTRACT FROM AUTHOR]

Simple Summary: Fish are maintained at high densities in modern fish farming systems, which explains their high susceptibility to infections. Copper sulfate and trichlorfon are commonly applied to fish for the control of infections and water quality. A high stocking density, Cu exposure, and trichlorfon exposure are typical inducers of physiological stress for fish. We found that adding the extract of mulberry (Morus alba L.) leaves (EML) to crucian carp (Carassius auratus) feed regulated their digestive capacity, antioxidant status, amino acid metabolism and bioenergetic homeostasis, thereby relieving the detrimental effects of these inducers on fish growth performance, feed intake and fish locomotion. This study was designed to examine the protective effects of the extract of mulberry (Morus alba L.) leaves (EML) on crucian carp (Carassius auratus) against a high stocking density, Cu exposure and trichlorfon exposure, which adversely impact fish growth performance, feed intake and fish locomotion. High stocking densities decreased the activities of amylase, lipase, trypsin, Na+/K+-ATPase and alkaline phosphatase (AKP), and increased the content of malonaldehyde (MDA) in fish digestive organs, indicating an impairment of the digestive function and a disturbance of the antioxidant status. Cu exposure increased the activities of glutamate–oxaloacetate transaminase (GOT) and glutamate–pyruvate transaminase (GPT) in fish digestive organs, suggesting the activation of amino acid metabolism. Furthermore, trichlorfon exposure reduced the activities of lactate dehydrogenase (LDH), glutathione reductase (GR), GOT and GPT, and the capacities of the anti-superoxide anion (ASA) and anti-hydroxyl radical (AHR) in fish muscles, indicating a disruption of the bioenergetic homeostasis and antioxidant status. Our present study indicates that dietary EML supplementation relieved the detrimental effects induced by these stressors. [ABSTRACT FROM AUTHOR]

Simple Summary: High stocking density and Cu and trichlorfon exposure are typical inducers of physiological stress in fish. It is well known that the stress response may be harmful to aquatic animals, inhibiting growth, causing reproductive failure, and reducing resistance to pathogens. Hence, it is important to attenuate the detrimental effects induced by these stressors in modern farming systems. Although Scoparia dulcis relieved cadmium-induced oxidative stress in rats, little information is available on the effects of high stocking density and CuSO4 and trichlorfon exposure in fish. Therefore, this study investigates the protective effects of dietary supplementation with Scoparia dulcis extract on fish maintained at a high stocking density and exposed to CuSO4 and trichlorfon. The present study may offer a feasible way of relieving the effects induced by these stressors. The objective of this study was to investigate the effects of Scoparia dulcis extract (SDE) on stress induced by high stocking density and Cu and trichlorfon exposure in crucian carp (Carassius auratus). The results showed that these stressors exerted detrimental effects in fish, such as inhibition of growth performance, reduced feed intake, and interruption of fish locomotion. Under high stocking density, dietary SDE supplementation increased the content of reduced glutathione (GSH) and the activities of amylase, catalase (CAT), and glutathione reductase (GR) and decreased the content of malonaldehyde (MDA) in the intestine of crucian carp. A similar trend was presented in the hepatopancreas under Cu exposure. Dietary SDE supplementation enhanced the activities of CAT, superoxide dismutase (SOD), glutathione peroxidase (GPx), lactate dehydrogenase, glutamate-oxaloacetate transaminase, and glutamate-pyruvate transaminase in the muscle of crucian carp under trichlorfon exposure. The optimum dietary SDE supplementation levels were 4.07, 4.33, and 3.95 g kg−1 diet based on the recovery rate of weight gain (RWG), feed intake (FI), and inhibitory rate of rollover (IR) for crucian carp under high stocking density and Cu and trichlorfon exposure, respectively. Overall, dietary supplementation with SDE may be a useful nutritional strategy for relieving these stresses in aquatic animals. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the effect of dietary protein levels on flesh quality, oxidative stress, and autophagy status in the muscles of triploid crucian carp (Carassius carassius triploid), and the related molecular mechanisms. Six experimental diets with different protein levels (26%, 29%, 32%, 35%, 38%, 41%) were formulated. A total of 540 fish with an initial weight of 11.79 ± 0.09 g were randomly assigned to 18 cages and six treatments with three replicates of 30 fish each for 8 weeks feeding. It could be found that the whole-body ash content significantly increased in high protein level groups (p < 0.05). The 29% dietary protein level group exhibited the highest muscle moisture, although there was an inconspicuous decrease in the chewiness of the muscles when compared with the other groups. The dietary protein level influenced the content of free amino acids and nucleotides, especially the content of flavor amino acids, which exhibited an increasing tendency along with the increasing protein level, such as alanine and glutamic acid, while the flavor nucleotides showed different fluctuation trends. Moreover, the genes related to muscle development were shown to be influenced by the dietary protein level, especially the expression of MRF4, which was up-regulated with the increasing dietary protein levels. The 29% dietary protein level promoted the majority of analyzed muscle genes expression to the highest level when compared to other dietary levels, except the Myostain, whose expression reached its highest at 38% dietary protein levels. Furthermore, the effect of dietary protein levels on antioxidant signaling pathway genes were also examined. High protein levels would boost the expression of GSTα; GPX1 and GPX4α mRNA expression showed the highest level at the 32% dietary protein group. The increasing dietary protein level decreased both mRNA and protein expressions of Nrf2 by up-regulating Keap1. Autophagy-related gene expression levels reached the peak at 32% dietary protein level, as evidenced by a similar change in protein expression of FoxO1. In summary, muscle nutritional composition, antioxidative pathways, and autophagy levels were affected by the dietary protein levels. A total of 29–32% dietary protein level would be the appropriate level range to improve muscle quality and promote the antioxidant and autophagy capacity of triploid crucian carp muscles. [ABSTRACT FROM AUTHOR]

The present study investigated the sequential regulation signals of high-carbohydrate diet (HCD)-induced hepatic lipid deposition in gibel carp (Carassius gibelio). Two isonitrogenous and isolipidic diets, containing 25% (normal carbohydrate diet, NCD) and 45% (HCD) corn starch, were formulated to feed gibel carp (14.82 ± 0.04 g) for 8 weeks. The experimental fish were sampled at 2nd, 4th, 6th, and 8th week. In HCD group, the hyperlipidemia and significant hepatic lipid deposition (oil red O area and triglyceride content) was found at 4th, 6th, and 8th week, while the significant hyperglycemia was found at 2nd, 4th, and 8th week, compared to NCD group (P < 0.05). HCD induced hepatic lipid deposition via increased hepatic lipogenesis (acc, fasn, and acly) but not decreased hepatic lipolysis (hsl and cpt1a). When compared with NCD group, HCD significantly elevated the hepatic sterol regulatory element binding proteins 1 (SREBP1) signals (positive hepatocytes and fluorescence intensity) at 4th, 6th, and 8th week (P < 0.05). The hepatic SREBP1 signals increased from 2nd to 6th week, but decreased at 8th week due to substantiated insulin resistance (plasma insulin levels, plasma glucose levels, and P-AKTSer473 levels) in HCD group. Importantly, the hepatic carbohydrate response element binding protein (ChREBP) signals (positive hepatocytes, fluorescence intensity, and expression levels) were all significantly elevated by HCD-induced glucose-6-phosphate (G6P) accumulation at 2nd, 4th, 6th, and 8th week (P < 0.05). Compared to 2nd and 4th week, the hepatic ChREBP signals and G6P contents was significantly increased by HCD at 6th and 8th week (P < 0.05). The HCD-induced G6P accumulation was caused by the significantly increased expression of hepatic gck, pklr, and glut2 (P < 0.05) but not 6pfk at 4th, 6th, and 8th week, compared to NCD group. These results suggested that the HCD-induced hepatic lipid deposition was mainly promoted by SREBP1 in earlier stage and by ChREBP in later stage for gibel carp. This study revealed the sequential regulation pathways of the conversion from feed carbohydrate to body lipid in fish. [ABSTRACT FROM AUTHOR]

Valnemulin (VML) is a semi-synthetic pleuromutilin derivative widely used to treat animal bacterial diseases. However, no study has comprehensively evaluated VML metabolism in aquatic animals, including crucian carp. This study aimed to investigate VML metabolism in crucian carp. VML metabolites in crucian carp were quantified via intraperitoneal injection and analyzed via ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Three VML metabolites were detected in crucian carp via ultra-performance liquid chromatography-tandem quadrupole and time-of-flight mass spectrometry (UPLC-Q-TOF/MS) structural analysis. The enrichment and metabolism rules of the metabolites were summarized based on tissue distribution and concentration changes of the three metabolites. The metabolites were mainly found in the liver at 0.1 h after VML injection. The levels of the metabolites were abundant in the bile from 4 h to 12 h and in the skin after 72 h. The levels of the metabolites in the bile first increased, then decreased. The metabolism in the liver was completed at 72 h. The metabolites were detected in the skin following a 72 h period, which increased with time. [ABSTRACT FROM AUTHOR]

Current knowledge on the fish gut microbiota has largely been obtained from experiments on laboratory-reared animals. Here, the crucian carp (Carassius auratus) with a mean weight of 159.9 ± 11.4 g (mean ± SD) were collected from their natural habitats (i.e., Wuhu lake and Poyang lake, China), and the gut microbiota were analysed by using the next-generation sequencing of 16S rRNA gene. We obtained more than 430,000 high-quality reads, which constituted more than 1200 operational taxonomy units (OTUs), revealing extremely diverse microbes in the fish gut. Proteobacteria, Fusobacteria, Bacteroidetes and Firmicutes were detected as the prominent phyla (each > 1% of total abundance) within the gut microbiota, regardless of the host habitat or the gut segment (i.e., foregut vs. hindgut). Although the microbes in the hindgut were more diverse (OTU number, Shannon and Chao1; One-way Anova, p > 0.05) than in the foregut, the host habitat had a significant role in shaping the community structures (MRPP, ANOSIM, PERMANOVA, p < 0.01). Interestingly, we also detected a set of common OTUs, whereby genera Aeromonas and Cetobacterium might comprise the core gut microbiota of crucian carp. [ABSTRACT FROM AUTHOR]

Aquaponics is a new type of composite farming system, which combines aquaculture and hydroponics through ecological design to achieve scientific synergism. However, the effects of aquaponics on the welfare status and stress parameters of fish are unclear. In this study, 150 crucian carp with an average initial body weight of 7.06 ± 0.32 g were selected. Nine fish were randomly selected as the control group (NC group and hypoxia group) for stress, antioxidant and gene expression parameters after acclimation and hypoxia stress, respectively. The remaining crucian carps were randomly divided into three experimental groups with 20 crucian carps in each group (T0, T1 and T2, respectively), with three replicates. The fresh weight of the lettuce root in the T2 group had no significant effect (p > 0.05). Compared with the control group (T0 and T1), there were significant differences in the specific growth rate, the weight gain rate, the fresh leaf weight, the chlorophyll content and the water quality parameters in group T2 (p < 0.05). Regarding the biochemical parameters, superoxide dismutase and catalase showed significant differences between the T2 and T1 groups (p < 0.05). At the same time, the HSP70 and Prdx3 genes were upregulated in the liver of the T2 group compared to the NC group and the hypoxia group. The research suggests that aquaponics may reduce the hypoxia stress of crucian carp without affecting the growth of crucian carp and lettuce. [ABSTRACT FROM AUTHOR]

The fish-flower symbiosis model is an eco-friendly sustainable farming technology combining plants, fish and microorganisms in a recirculating aquaculture system. However, there are few studies on the structure and diversity of microbial communities in fish intestines, culture water and plant roots during fish-flower symbiosis. Here, we cultured carp (Cyprinus carpio), crucian carp (Carassius auratus) and grass carp (Ctenopharyngodon idella) with mint (Mentha spicala L.) and extracted total genomic DNA from intestinal microorganisms, culture-water microorganisms and root microorganisms for each fish species for high-throughput sequencing of 16S rRNA genes. Analysis of microbial community structure and diversity revealed changes in abundance of microbial genera in the intestines and culture water of each fish species, including changes in the dominant taxa. Pirellula, Truepera, Aquincola, Cetobacterium and Luteolibacter were widespread in the fish intestine, culture water and mint root system. This study revealed the effects of mint feeding on the structure and diversity of microbial communities of fish, water bodies and the mint root system during fish-flower symbiosis, providing a theoretical reference for the promotion and application of fish-flower (mint) symbiosis technology and healthy fish culture technology. [ABSTRACT FROM AUTHOR]

Genome duplication supplies raw genetic materials and has been thought to be essential for evolutionary innovation and ecological adaptation. Here, we select Kelch-like (klhl) genes to study the evolution of the duplicated genes in the polyploid Carassius complex, including amphidiploid C. auratus and amphitriploid C. gibelio. Phylogenetic, chromosomal location and read coverage analyses indicate that most of Carassius klhl genes exhibit a 2:1 relationship with zebrafish orthologs and confirm two rounds of polyploidy, an allotetraploidy followed by an autotriploidy, occurred during Carassius evolution. The lineage-specific expansion and biased retention/loss of klhl genes are also found in Carassius. Transcriptome analyses across eight adult tissues and seven embryogenesis stages reveal varied expression dominance and divergence between the two species. The expression of klhls in response to Carassius herpesvirus 2 infection shows different expression changes corresponding to distinct herpesvirus resistances in three C. gibelio gynogenetic clones. Finally, we find that most C. gibelio klhl genes possess three alleles except eight genes that have lost one or two alleles due to genome rearrangement. The allele expression bias is prosperous for Cgklhl genes and varies during embryogenesis owning to the sequential expression manner of the alleles. The current study provides global insights into the genomic and transcriptional evolution of duplicated genes in a given superfamily resulting from multiple rounds of polyploidization. [ABSTRACT FROM AUTHOR]

Stress inevitably occurs during any fish handling and manipulation in culturing, research, or clinical examination situations that require capture and removal of fish from water. Different stress factors can affect the changes in the relative numbers and function of cells of the fish immune system. Catching, transportation and over-crowding caused stress-induced changes in the total number of leukocytes and thrombocytes, as well as changes in the leukocyte formula in Prussian carp (Carassius gibelio, Bloch, 1782) presented here. Cytochemical characterization of leukocyte cell types was performed by applying Myeloperoxidase (MPO), Periodic Acid Schiff (PAS) and Sudan Black B (SBB) staining of Prussian carp blood smears. Cytochemical characterization is a rapid and efficient method for white leukocyte differentiation and insight in their functional status. Comparison and analysis in Prussian carp hematological parameters from fish with and without exposure to stressful conditions such as capture, manipulation, transport and holding, revealed significant differences between stressed and non-stressed fish. Significant reduction in the total number of thrombocytes and lymphocytes and the increase in total neutrophil count were observed in stressed animals. However, differences in total leukocyte number and the number of monocytes were not observed. Deviations from the estimated reference intervals for Prussian carp hematological parameters clearly indicated the presence/absence of a stress reaction and to some extent its intensity. Estimated reference intervals and characterization of morphological and cytochemical appearance of blood cells form a solid basis for further research of the cellular immune function and hematology changes in Prussian carp. [ABSTRACT FROM AUTHOR]

This study investigated the potential role of curcumin (CUR) in preventing oxidative stress and ferroptosis induced by ammonia exposure in gibel carp. Experimental fish (initial weight: 11.22 ± 0.10 g, n = 150) were fed diets supplemented with or without 0.5% CUR for 56 days, followed by a 24 h ammonia (32.5 mg/L) exposure. Liver damages (aspartate aminotransferase (AST), alanine aminotransferase (ALT), adenosine deaminase (ADA), and alkaline phosphatase (ALP)) and oxidative stress enzyme activities (reactive oxygen species (ROS), malondialdehyde (MDA); and the content of antioxidant capacity (T-AOC), superoxide dismutase (SOD), and glutathione peroxidase (GPx)) were induced by ammonia stress. The antioxidant capacity was decreased, as indicated by inhibited gene expression of nuclear factor erythroid 2-related factor 2 (nrf2), heme oxygenase-1 (ho-1), catalase (cat), and sod. Ferroptosis was induced by ammonia stress, as suggested by upregulated mRNA levels of nuclear receptor coactivator 4 (ncoa4), transferrin receptor 1 (tfr1), and iron-responsive element-binding protein 2 (ireb2), and downregulated expression of glutathione peroxidase 4 (gpx4), ferroportin (fpn), and ferritin heavy chain 1 (fth1). In addition, both mRNA and protein levels of ferroptosis markers acyl-CoA synthetase long-chain family member 4 (ACSL4) and prostaglandin-endoperoxide synthase 2 (PTGS2) were upregulated, while cystine/glutamate antiporter (SLC7A11) was downregulated. However, liver injury and ferroptosis in fish induced by ammonia could be attenuated by CUR. Collectively, these findings demonstrate that CUR ameliorates oxidative stress and attenuates ammonia stress-induced ferroptosis. This study provides a new perspective on potential preventive strategies against ammonia stress in gibel carp by dietary CUR. [ABSTRACT FROM AUTHOR]

The detection of emerging contaminants (ECs) and understanding their ecotoxicity has brought new challenges to water pollution control. Triclosan (TCS), as an emerging contaminant, is a commonly used antibacterial agent widely present in the environment. Microdialysis (MD), as a sampling technique, can overcome some of the deficiencies of traditional approaches to sampling, using sources such as blood, urine, tissue, and target organs, in terms of invasiveness, time from collection to analysis, and possible changes during sample preparation. In this study, we coupled MD with analysis using UHPLC-QTOF/MS to identify the endogenous metabolites in the liver as biomarkers of the exposure of living crucian carp to TCS. The identified biomarkers were then quantified using UHPLC-MS/MS to continuously monitor the effect of TCS on endogenous metabolites in the liver of living crucian carp, which contributes to a better understanding of the toxicological effect of TCS. The experimental results demonstrated that TCS exposure interfered with the metabolic pathways of amino acids (l-isoleucine and l-histidine), purines (xanthine and hypoxanthine), and small nerve molecules (acetylcholine and choline). [ABSTRACT FROM AUTHOR]

Simple Summary: It is almost 50 years since amoeba-associated granulomatosis was first described in goldfish (Carassius auratus), but the aetiologic agent has never been identified. In this study, a new archamoeba species, Endolimax carassius, is characterised as the causative agent of systemic granulomatous disease in goldfish. Phylogenetic analyses determined the new goldfish parasite species as a genotype sister of Endolimax piscium, the causative agent of systemic granulomatous disease in Senegalese sole. The fish genotypes clustered with other available genotypes from mammals in a well-supported Endolimax clade within the Mastigamoebidae. Endolimax is a genus of intestinal amoebae which stands among the least known human protists. Previous studies on amoebic systemic granulomatosis of a marine fish (Solea senegalensis) resulted in the unexpected characterization of a new organism which was related to Endolimax and named E. piscium. The existence of multiple reports of systemic granulomatosis caused presumptively by unidentified amoebae in goldfish lead us to investigate the organism involved in goldfish disease. Analysed goldfish presented small whitish nodules in the kidney, which correspond to chronic granulomatous inflammatory reactions with a ring-layer of amoebae in the periphery. Amoebae were amitochondriate and were located in a parasitophorous vacuole within macrophages, as previous studies on this condition in goldfish and other freshwater fish pointed out. SSU rDNA characterization confirmed a new Endolimax lineage which appears closely related to E. piscium, but the molecular evidence, distinct pathological features and lack of ecological overlapping between the hosts support their assignment to a new species, E. carassius. The results support the existence of a considerable unexplored diversity of Endolimax spp. among fish, and their proper characterization can contribute to an understanding of Archamoebae evolution and pathogenic potential. [ABSTRACT FROM AUTHOR]

In humans, four small HERCs (HERC3-6) exhibit differential degrees of antiviral activity toward HIV-1. Recently we revealed a novel member HERC7 of small HERCs exclusively in non-mammalian vertebrates and varied copies of herc7 genes in distinct fish species, raising a question of what is the exact role for a certain fish herc7 gene. Here, a total of four herc7 genes (named HERC7a–d sequentially) are identified in the zebrafish genome. They are transcriptionally induced by a viral infection, and detailed promoter analyses indicate that zebrafish herc7c is a typical interferon (IFN)-stimulated gene. Overexpression of zebrafish HERC7c promotes SVCV (spring viremia of carp virus) replication in fish cells and concomitantly downregulates cellular IFN response. Mechanistically, zebrafish HERC7c targets STING, MAVS, and IRF7 for protein degradation, thus impairing cellular IFN response. Whereas the recently-identified crucian carp HERC7 has an E3 ligase activity for the conjugation of both ubiquitin and ISG15, zebrafish HERC7c only displays the potential to transfer ubiquitin. Considering the necessity for timely regulation of IFN expression during viral infection, these results together suggest that zebrafish HERC7c is a negative regulator of fish IFN antiviral response. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the susceptibility to body deformities in juveniles of 13 common European cypriniform fish, caused by intensive feeding with the same commercial dry diet administered at 25°C according to a similar feeding schedule. The final share of individuals with body malformations differed considerably among species and was 0.0-87.0%. Unaffected by the intensive feeding were only Barbus barbus (L.), Chondrostoma nasus (L.), Cyprinus carpio L. and Leuciscus aspius (L.). They can be safely fed with the highest rations of dry diet constituting 2,5-3% of fish biomass daily. Most of the species exhibited body malformations in a short time of only 20-30 days of feeding. Abramis brama (L.), Leuciscus idus (L.), Leuciscus leuciscus (L.), Scardinius erythrophthalmus (L.), Carassius carassius (L.), Rutilus rutilus (L.) and Squalius cephalus (L.) proved to be highly prone to body deformities – daily ration of feed 2.5% of fish biomass resulted in high incidence of malformed individuals after 60 days of feeding (50-87%). For these species safe daily ration of a dry diet should not exceed 2% of total fish biomass. Tinca tinca (L.) and Vimba vimba (L.) showed medium susceptibility to body deformities (11 and 24%, respectively). They can be fed with the daily ration of a dry diet about 2,3% of fish biomass. Some regularities connected with different susceptibility to fish body deformities are discussed in the paper. [ABSTRACT FROM AUTHOR]

Blood analysis is used to evaluate the effects of various environmental factors on fishes and to assess fish health and welfare. Fish blood is routinely sampled from the caudal vein or the heart. The aim of the present study was to determine the differences between venous and cardiac crucian carp (Carassius carassius (L.)) blood parameters. Additionally, the influence of sex was tested. The fish were divided into two groups: group I consisted of 10 males and 9 females, group II consisted of 8 males and 8 females. The fish from group I had blood sampled first from the caudal vein and then from the heart. The fish from group II had the procedures in the opposite order. The hematological parameters determined in the present study depended on the blood collection site and the sex of the individuals. Blood biochemical indices depended on the sex of the fish but not on the blood sampling site. The effect of sampling order was observed in the case of both hematological and biochemical parameters. The results of the current study indicated that the blood collection site, the sex of fish, and sampling order should be taken into consideration in hematological experiments. [ABSTRACT FROM AUTHOR]

Antibiotics were the main fishery drugs for treating Aeromonas hydrophila (A. hydrophila) infection, which would generate selective pressure and result in the appearance of antibiotic-resistant bacteria. The bacterial quorum sensing (QS) system provides a new alternative strategy against A. hydrophila infection. QS inhibitors can reduce bacterial virulence behaviors by disrupting QS, which has no effect on bacterial growth. Therefore, we studied the effect of cinnamaldehyde from a natural plant extract on the QS of A. hydrophila aiming to reduce its pathogenicity. The efficacy of cinnamaldehyde against A. hydrophila was evaluated from various aspects, including the effects on aerolysin, lipase, protease, swarming motility, biofilm formation, acyl-homoserine lactones (AHLs), and QS-related genes. Moreover, the therapeutic effect of cinnamaldehyde in vitro and in vivo was studied. The results showed that cinnamaldehyde could decrease the virulence phenotypes of A. hydrophila regulated by QS. Moreover, the transcriptions of related genes (aerA, ahyR, and ahyI) were downregulated following the addition of cinnamaldehyde. The in vitro and in vivo therapeutic assays show that cinnamaldehyde could reduce the aerolysin-mediated A549 cell injury and increase the survival rate of crucian carp infected with A. hydrophila. These results indicate that cinnamaldehyde would be a candidate QS inhibitor against A. hydrophila infection. [ABSTRACT FROM AUTHOR]

For aquaculture assessments, the length-weight relationship and condition factor are considered as standard methods for determining fish growth, its health and the potential yield. A year-long study was conducted to calculate length-weight relationships (LWRs) and condition factor (K) for seven fish species, Schizothorax niger (Alghad or snowtrout), S. curvifrons (Sattar snowtrout), Cyprinus carpio (Common carp), Carassius carassius (Crucian carp), Pethia conchonius (Rosy barb), Crossocheilus diplochilus (Kashmir latia) and Gambusia holbrooki (Mosquito fish) in Manasbal Lake. The results revealed that four captured fish species (S. niger, S. curvifrons, C. diplochilus and G. holbrooki) exhibited negative allometric growth, while other fish species (C. carpio, C. carassius, P. conchonius) exhibited positive allometric growth. LWR was significant at P < 0.01 in all seven fish species, with a coefficient of determination (R2) ranging between 0.73 to 0.96. The K was higher in C. carpio than C. carassius, P. conchonius, G. holbrooki, C. diplochilus, S. niger and S. curvifrons. The current study providing the LWRs and condition factor of seven fish species from Manasbal Lake, Kashmir will be helpful for the management of fish species as well as for assessing the ecological condition of the Lake. [ABSTRACT FROM AUTHOR]

Background: MicroRNAs (miRNAs) are endogenous small non-coding RNAs (21–25 nucleotides) that act as essential components of several biological processes. Golden-back crucian carp (GBCrC, Carassius auratus) is a naturally mutant species of carp that has two distinct body skin color types (golden and greenish-grey), making it an excellent model for research on the genetic basis of pigmentation. Here, we performed small RNA (sRNA) analysis on the two different skin colors via Illumina sequencing. Results: A total of 679 known miRNAs and 254 novel miRNAs were identified, of which 32 were detected as miRNAs with significant differential expression (DEMs). 23,577 genes were projected to be the targets of 32 DEMs, primarily those involved in melanogenesis, adrenergic signaling in cardiomyocytes, MAPK signaling pathway and wnt signaling pathway by functional enrichment. Furthermore, we built an interaction module of mRNAs, proteins and miRNAs based on 10 up-regulated and 13 down-regulated miRNAs in golden skin. In addition to transcriptional destabilization and translational suppression, we discovered that miRNAs and their target genes were expressed in the same trend at both the transcriptional and translational levels. Finally, we discovered that miR-196d could be indirectly implicated in regulating melanocyte synthesis and motility in the skin by targeting to myh7 (myosin-7) gene through the luciferase reporter assay, antagomir silencing in vivo and qRT-PCR techniques. Conclusions: Our study gives a systematic examination of the miRNA profiles expressed in the skin of GBCrC, assisting in the comprehension of the intricate molecular regulation of body color polymorphism and providing insights for C. auratus breeding research. [ABSTRACT FROM AUTHOR]

Background: MicroRNAs (miRNAs) are endogenous small non-coding RNAs (21–25 nucleotides) that act as essential components of several biological processes. Golden-back crucian carp (GBCrC, Carassius auratus) is a naturally mutant species of carp that has two distinct body skin color types (golden and greenish-grey), making it an excellent model for research on the genetic basis of pigmentation. Here, we performed small RNA (sRNA) analysis on the two different skin colors via Illumina sequencing. Results: A total of 679 known miRNAs and 254 novel miRNAs were identified, of which 32 were detected as miRNAs with significant differential expression (DEMs). 23,577 genes were projected to be the targets of 32 DEMs, primarily those involved in melanogenesis, adrenergic signaling in cardiomyocytes, MAPK signaling pathway and wnt signaling pathway by functional enrichment. Furthermore, we built an interaction module of mRNAs, proteins and miRNAs based on 10 up-regulated and 13 down-regulated miRNAs in golden skin. In addition to transcriptional destabilization and translational suppression, we discovered that miRNAs and their target genes were expressed in the same trend at both the transcriptional and translational levels. Finally, we discovered that miR-196d could be indirectly implicated in regulating melanocyte synthesis and motility in the skin by targeting to myh7 (myosin-7) gene through the luciferase reporter assay, antagomir silencing in vivo and qRT-PCR techniques. Conclusions: Our study gives a systematic examination of the miRNA profiles expressed in the skin of GBCrC, assisting in the comprehension of the intricate molecular regulation of body color polymorphism and providing insights for C. auratus breeding research. [ABSTRACT FROM AUTHOR]

Dietary supplementation with fermentation products of Astragalus can enhance the immune function of aquaculture animals. We explored the synergistic effects of Lactobacillus plantarum and Bacillus coagulans on the solid-state fermentation of Astragalus to investigate whether feeding fermentation products to crucian carp can improve disease resistance. The optimal ratio of Astragalus + (L. plantarum + B. coagulans) (ALB), temperature, and number was 3 : 3, 37°C, and 1.0 × 108 CFU/g, respectively. After 48 h mixed fermentation, the number of probiotics increased to 2.2 × 109 CFU/g, pH decreased to 3.2, and high molecular weight proteins disintegrated into small molecular weight or soluble proteins. In addition, several holes appeared on the Astragalus surface. Compared with unfermented Astragalus, the content of Astragalus polysaccharide and calycosin increased by 3.82- and 1.31-fold, respectively, on fermentation and that of total Astragalus saponins decreased by 0.77-fold. Furthermore, on Cyprinid herpesvirus 2 (CyHV-2) and Aeromonas veronii (A. veronii) challenges, the cumulative survival rates of crucian carp fed common feed and ALB were 80.00% and 65.00%, respectively. Overall, feeding mixed fermentation products to crucian carp positively impacted their health and disease resistance. We believe that our results provide theoretical guidance for developing effective plant-based agents to prevent diseases in crucian carp. [ABSTRACT FROM AUTHOR]

Background: In order of importance, the most commercially important fish species often caught for food in Lake Ziway are Oreochromis niloticus, Clarias gariepinus, Carassius carassius, and Cyprinus carpio. Some fish parasites have been reported in this lake, and the lake ecosystem appears to be conducive to parasite propagation, which may have an impact on fish marketability and societal health. Objective: The purpose of this study was to look into the prevalence of major fish parasites in four of the most commercially important fish species in Lake Ziway, as well as their effects on the commercial values of host fishes and the health of fish consumers. Materials and Methods: From May to July 2019, the study was carried out by purchasing random samples of live fish from local fishermen at Wafiko, Korokonch, and Kafteria landing sites and administering a research questionnaire to various stakeholders. Within three months, 240 specimens from the four species were examined in the Laboratory of Batu Fish and Aquatic Life Research Center. The data were analyzed using SPSS software. Results: About 87.5% of the fish examined were found to be infested with 64.2% (trematodes), 42.5% (nematodes), 40% (crustaceans), 17.1% (cestodes) and 1.3% (Acantocephala). The fish examined were found to be heavily infested with zoonotic Clinostomum, Contraceacum, and Capillaria species. Thus, fishers were losing some catches due to the effect of parasites. The differences in the prevalence of parasites among the studied fish species were statistically significant (P = 0.00), but it was not statistically significant for the fish sexes (P = 0.60). Conclusion: Lake Ziway's commercially important fish species are heavily infested with various types of external and internal parasites, which have both health and economic consequences for the people living on raw fish as food. Therefore, it is vital that awareness creation is done and sanitary measures are taken to stem the problem of human health caused because of eating raw fish and to enhance the productivity of the lake ecosystem. [ABSTRACT FROM AUTHOR]

Simple Summary: Roundup is a widely used herbicide. Its active component, glyphosate, is described as an endocrine disrupter. The effect of this glyphosate-containing herbicide on the reproductive parameters of crucian carp (Carassius carassius) was investigated in this study. The entire pituitary glands and ovarian fragments of crucian carp were incubated in vitro in the medium containing two different concentrations of Roundup (1 and 10 ng/mL). We assessed the final oocyte maturation and ovulation, structural changes in follicles, levels of 17,20β-progesterone, and luteinizing hormone. The mRNA levels of zona radiata (chorion) genes, kisspeptin, and its receptor as well as luteinizing hormone and estrogen receptors were also determined. Obtained results indicate that Roundup may adversely affect oocyte maturation and the quality of crucian carp eggs, suggesting that exposure to this herbicide can lead to reproductive disorders in fish. Roundup, the most popular herbicide in global agriculture, is regarded as an endocrine disruptor causing alterations of important hormones at the hypothalamic−pituitary−gonadal axis as well as impairment of gametogenesis. The whole pituitary glands of crucian carp (Carassius carassius) were incubated for 3 h in the medium containing Roundup (0-control, 1 and 10 ng/mL). The level of luteinizing hormone (LH), and mRNA transcript abundance of kisspeptin (kiss-1) and its receptor (gpr54), were determined. The isolated ovarian fragments were incubated for 24 h in the presence of Roundup and the following effects on reproductive parameters were determined: the final oocyte maturation and ovulation, structural changes in follicles, secretion of 17,20β-progesterone (17,20β-P) as well as mRNA transcript abundance of the luteinizing hormone receptor (lhr), estrogen receptors (erα, erβ1, erβ2), and zona radiata (chorion) proteins (zp2 and zp3). Roundup inhibited final oocyte maturation and decreased the percentage of ovulated eggs, and furthermore, caused structural changes in the ovarian follicular components. There were no significant changes in the measured hormone levels and analyzed genes mRNA transcript abundance. Summing up, obtained results indicate that Roundup may adversely affect oocyte maturation and the quality of eggs, suggesting that exposure to this herbicide can lead to reproductive disorders in fish. [ABSTRACT FROM AUTHOR]