Crucian Carp Carassius Auratus Research Articles

Multi-omics analysis of miRNA-mediated intestinal microflora changes in crucian carp Carassius auratus infected with Rahnella aquatilis.

Infection by an emerging bacterial pathogen Rahnella aquatilis caused enteritis and septicemia in fish. However, the molecular pathogenesis of enteritis induced by R. aquatilis infection and its interacting mechanism of the intestinal microflora associated with microRNA (miRNA) immune regulation in crucian carp Carassius auratus are still unclear. In this study, C. auratus intraperitoneally injected with R. aquatilis KCL-5 was used as an experimental animal model, and the intestinal pathological changes, microflora, and differentially expressed miRNAs (DEMs) were investigated by multi-omics analysis. The significant changes in histopathological features, apoptotic cells, and enzyme activities (e.g., lysozyme (LYS), alkaline phosphatase (AKP), alanine aminotransferase (ALT), aspartate transaminase (AST), and glutathione peroxidase (GSH-Px)) in the intestine were examined after infection. Diversity and composition analysis of the intestinal microflora clearly demonstrated four dominant bacteria: Proteobacteria, Fusobacteria, Bacteroidetes, and Firmicutes. A total of 87 DEMs were significantly screened, and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that the potential target genes were mainly involved in the regulation of lipid, glutathione, cytosine, and purine metabolism, which participated in the local immune response through the intestinal immune network for IgA production, lysosome, and Toll-like receptor (TLR) pathways. Moreover, the expression levels of 11 target genes (e.g., TLR3, MyD88, NF-κB, TGF-β, TNF-α, MHC II, IL-22, LysC, F2, F5, and C3) related to inflammation and immunity were verified by qRT-PCR detection. The correlation analysis indicated that the abundance of intestinal Firmicutes and Proteobacteria was significantly associated with the high local expression of miR-203/NF-κB, miR-129/TNF-α, and miR-205/TGF-β. These findings will help to elucidate the molecular regulation mechanism of the intestinal microflora, inflammation, and immune response-mediated miRNA-target gene axis in cyprinid fish.

Сравнительная характеристика состояния внутренних органов серебряного карася (Carassius auratus gibelio) в возрастном аспекте

The histological results of the study of the organs of larvae and mature individuals of the silver crucian carp Carassius auratus gibelio (Bloch, 1782) caught in the reservoirs of the Volga River delta are presented. Analysis the internal organs state and tissues helps to identify physiological disorders and pathologies. Thanks to the histological method, it becomes possible to study the structure of the body at the cellular and tissue level, to determine the development of the pathological process and the degree of damage. For pathomorphological evaluation, the liver, gills, kidneys, spleen, intestines and pancreas were examined in silver crucian carp of different ages. It was established that representatives of this species of different ages had identical pathological changes in the organs, but the degree of their manifestation was different: there was a tendency to increase the intensity of the pathology with age. 4 types of major pathological changes associated with metabolic disorders, necrotic damage to cells and tissues, circulatory disorders of organs and signs of hyperplasia were found. Sexually mature individuals had a higher level of pathological manifestations. To a greater extent, the gills, which are in direct contact with the environment, were damaged. The liver of the studied fish also had significant damage. The most frequently reported liver pathology was lipoid degeneration (vacuolar degeneration). Kidneys, intestines and spleen were characterized by degenerative and necrotic disorders. In the spleen of adults, granulomatous inflammation was found, which indicates infectious diseases. The same types of morphological changes were found in larvae and mature individuals, which indicates the nonspecific nature of the identified pathologies, which, as a rule, are associated with the adaptation of the organism to the prevailing living conditions.

Characteristics of CD4-1 gene and its immune responses against Aeromonas veronii infection by activating NF-κB signaling in Qihe crucian carp Carassius auratus

CD4-1 found in bony fish contains four extracellular immunoglobulin (Ig)-like domains similar to that of mammalian CD4, which is crucial for the activation of CD4+ helper T-cell. However, there is limited knowledge regarding the molecular markers, immune functions and regulation mechanism of CD4-1 in teleosts due to their vast diversity. In this study, we cloned and characterized two isoforms of Qihe crucian carp CD4-1, designated as CaCD4-1.1 and CaCD4-1.2. We further explored their expression responses upon stimulation with Aeromonas veronii, and the regulation of their immune responses against A. veronii by NF-κB. The ORF of CaCD4-1.1 and CaCD4-1.2 cDNA encoded 477 and 466 amino acids, respectively. Both proteins contained seven conserved cysteine residues in the extracellular domain, and a CCC motif in their cytoplasm, respectively. However, CaCD4-1.1 exhibited a relatively limited similarity with CaCD4-1.2 in the ectodomain. The quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that the mRNA expression of CaCD4-1.1 and CaCD4-1.2 exhibited differential constitutive expression across all examined tissues. Furthermore, the expression level of CD4-1.2 was higher than that of CD4-1.1 in the gills, head kidney, and spleen of Qihe crucian carp subjected to A. veronii challenge, while it was lower in the trunk kidney. Inhibition of NF-κB activity resulted in a decrease in the expression levels of CD4-1.1 and CD4-1.2 mRNA in the gill, while inducing an increase in expression levels in the spleen, in accordance with the observed ultrastructural changes in both organs. Interestingly, the impact of NF-κB on the mRNA expression level of CD4-1.1 appears to be stronger than that of CD4-1.2. Our results suggest that CaCD4-1.1 and CaCD4-1.2 could be expressed on T cells and antigen-sampling cells that exhibit similar characteristics to mammalian M cells, respectively, and differentially regulated by NF-κB in adaptive immune responses against bacterial infection. This research contributes to a better understanding of the crucial role of CD4-1 in the immune response of Qihe crucian carp and provide novel insights for the prevention and treatment of fish diseases in aquaculture.

Correction: Xu et al. Effects of Replacing Dietary Fish Meal by Soybean Meal Co-Fermented Using Bacillus subtilis and Enterococcus faecium on Serum Antioxidant Indices and Gut Microbiota of Crucian Carp Carassius auratus. Fishes 2022, 7, 54

In the original publication [...]

Development of RT-qPCR and loop-mediated isothermal amplification (LAMP) assays for the rapid detection of Rahnella aquatilis in fish

Rahnella aquatilis is widely recognized as an opportunistic pathogen of fish, but molecular detection and diagnostic techniques for it remain to be developed. In a previous study, we isolated the pathogenic R. aquatilis strain KCL-5 from diseased crucian carp Carassius auratus and identified it as a new fish pathogen causing enteritis and septicemia. Here, we describe novel real-time quantitative PCR (RT-qPCR) and loop-mediated isothermal amplification (LAMP) assays for the rapid and sensitive detection of R. aquatilis. Specific RT-qPCR and LAMP primers were developed for the outer membrane protein (OmpA) gene. Their reaction systems were optimized using the recombinant plasmid pMD18-T containing the OmpA gene and their specificities were confirmed using various bacterial fish pathogens including Aeromonas hydrophila, A. veronii, A. allosaccharophila, Yersinia ruckeri, Vibrio vulnificus, V. alfacsensis, Providencia rettgeri, and R. aquatilis. The sensitivities of the RT-qPCR and LAMP assays were further evaluated using serial dilutions of the positive recombinant plasmid pMD18-T/OmpA. Both the RT-qPCR and LAMP assays were able to reliably detect the presence of R. aquatilis with high accuracy and a specificity of 100%. The lowest detection limits of the RT-qPCR and LAMP assays were 2.3 copies/μL and 2.3 × 101 copies/μL, respectively. To the best of our knowledge, this is the first report of RT-qPCR and LAMP methods for R. aquatilis detection, and provides a means for its rapid detection and diagnosis in fish.

Characterization of gill transcriptome, SSR/SNP markers and expression analysis of lysozyme LysC gene from Carassius auratus upon Aeromonas hydrophila infection

The gills are large mucosal surfaces and play primary roles in respiration and immune defences. However, the molecular mechanism for gills of fish needs still to be explored. In the present study, transcriptomic analysis and identification of SSR and SNP markers were performed in the gills of crucian carp Carassius auratus. The results showed a total of 84,259 unigenes were annotated to NCBI NR, KEGG and GO databases for 55,283, 39,303, 33,388, respectively. Enriched KEGG pathway analyses for the identified genes showed the mainly functional modules such as metabolism, cellular processes, environmental adaptation, genetic processing, organismal and immune systems. Moreover, 22,102 SSRs (simple sequence repeats) were potentially identified and 9776 (44.2%) were accounted for the most dinucleotides. Transition and transversion sites of SNPs (single nucleotide polymorphisms) were also observed. Tissue distribution showed that the expression level of lysozyme LysC gene was relatively high in intestine, liver, spleen and kidney tissues and up-regulated in gills, skin and brain after the A. hydrophila infection. We discovered the immune-related pathways through the transcriptome analysis in the gills of crucian carp, some potential SSR/SNP markers were identified, and lysozyme gene predominantly expressed in mucosal immune organs (eg., gills, skin, intestine) responded to A. hydrophila infection. To the best of our knowledge, this was the detailed report on the molecular characteristics in crucian carp gills with transcriptome analysis, which will not only provide a scientific reference for further understanding the local defense mechanism, but also lay a foundation for molecular marker-assisted breeding in fish.

CD4-1 and CD4-2 single positive are two major CD4 lymphocyte subpopulations in ginbuna crucian carp Carassius auratus langsdorfii

CD4-1 and CD4-2 single positive are two major CD4 lymphocyte subpopulations in ginbuna crucian carp Carassius auratus langsdorfii

Adoptive transfer of sensitized leukocytes confers partial protection against herpesviral hematopoietic necrosis (HVHN) in ginbuna crucian carp Carassius auratus langsdorfii immunized with a live attenuated vaccine

Adoptive transfer of sensitized leukocytes confers partial protection against herpesviral hematopoietic necrosis (HVHN) in ginbuna crucian carp Carassius auratus langsdorfii immunized with a live attenuated vaccine

Dynamics of CD4-1+ and CD4-2+ lymphocytes in vaccinated ginbuna crucian carp Carassius auratus langsdorfii followed by cyprinid herpesvirus-2 (CyHV-2) challenge

Dynamics of CD4-1+ and CD4-2+ lymphocytes in vaccinated ginbuna crucian carp Carassius auratus langsdorfii followed by cyprinid herpesvirus-2 (CyHV-2) challenge

A novel NLRP3 homologue lacking the PYD domain activates IL-1β expression and promotes the bacterial elimination in Qihe crucian carp Carassius auratus

A novel NLRP3 homologue lacking the PYD domain activates IL-1β expression and promotes the bacterial elimination in Qihe crucian carp Carassius auratus

Addition of Brevibacillus laterosporus to the rearing water enhances the water quality, growth performance, antioxidant capacity, and digestive enzyme activity of crucian carp Carassius auratus

Addition of Brevibacillus laterosporus to the rearing water enhances the water quality, growth performance, antioxidant capacity, and digestive enzyme activity of crucian carp Carassius auratus

CD4-1 and CD4-2 single positive are two major CD4 lymphocyte subpopulations in ginbuna crucian carp Carassius auratus langsdorfii.

In this study, we established a murine cell line that expresses ginbuna crucian carp (ginbuna) CD4-2 and used it to develop an anti-CD4-2 monoclonal antibody (mAb). An established mAb, named D5, showed good reactivities to BALB/3T3 cells expressing CD4-2 and a lymphocyte population in the ginbuna leukocytes. Gene expression analysis showed that D5+ cells express CD4-2 and TCRβ genes but not CD4-1 and IgM genes, meanwhile May Grunwald-Giemsa staining of sorted D5+ cells had the typical morphology of lymphocytes. Two-color immunofluorescence analysis with anti-CD4-1 mAb (6D1) and anti-CD4-2 mAb (D5) by flow cytometry revealed that the percentages of CD4-1 single positive (SP) and CD4-2 SP lymphocytes were comparatively higher than CD4-1/CD4-2 double positive (CD4 DP) lymphocytes in all tissues examined in ginbuna. The highest percentages of CD4-2 SP cells (∼40%) were found in the thymus, while the head-kidney exhibited the highest percentages of CD4-1 SP (∼30%) and CD4 DP (∼5%) cells. These findings indicated that ginbuna CD4+ lymphocyte population consists of two major subpopulations (CD4-1 SP and CD4-2 SP) and a minor subset (CD4 DP).

The feeding habits of small-bodied fishes mediate the strength of top-down effects on plankton and water quality in shallow subtropical lakes

The proliferation of small-bodied fishes in lakes is often accompanied by deterioration of water quality and ecosystem function. However, the potential impacts of different types of small-bodied fish species (e.g., obligate zooplanktivores and omnivores) on subtropical lake ecosystems in particular have been overlooked mainly due to their small size, shorter life spans and lower economic value. Therefore, we conducted a mesocosm experiment to elucidate how plankton communities and water quality respond to different types of small-bodied fishes, including a common zooplanktivorous fish (thin sharpbelly Toxabramis swinhonis) and other small-bodied omnivorous fishes (bitterling Acheilognathus macropterus, crucian carp Carassius auratus and sharpbelly Hemiculter leucisculus). During the experiment, the mean weekly total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (CODMn), turbidity, chlorophyll-a (Chl.α) and trophic level index (TLI) values were generally higher in treatments where fish were present compared to treatments where fish were absent, but responses varied. At the end of the experiment, phytoplankton abundance and biomass and the relative abundance and biomass of cyanophyta were higher while the abundance and biomass of large-bodied zooplankton were lower in the fish-present treatments. Moreover, the mean weekly TP, CODMn, Chl.α and TLI values were generally higher in treatments with the obligate zooplanktivore, thin sharpbelly, when compared to treatments with omnivorous fishes. Also, the ratio of zooplankton to phytoplankton biomass was the lowest, and the ratio of Chl.α to TP was the highest in treatments with thin sharpbelly. Collectively, these general findings indicate that an overabundance of small-bodied fishes can have adverse effects on water quality and plankton communities and that small-bodied zooplanktivorous fishes likely induce stronger top-down effects on plankton and water quality than omnivorous fishes. Our results emphasise that small-bodied fishes should be monitored and controlled if overabundant when managing or restoring shallow subtropical lakes. From the perspective of environmental protection, the combined stocking of different piscivorous fish species that feed in different habitat types could be a way forward to control small-bodied fishes with different feeding habits, but more research is needed to assess the feasibility of this approach.

Multiomics analysis revealed miRNAs as potential regulators of the immune response in Carassius auratus gills to Aeromonas hydrophila infection.

The gill of fish is an important immune organ for pathogen defense, but its microRNA (miRNA) expression and regulatory mechanism remain unclear. In this study, we report on the histopathological and immunohistochemical features of the gills of the crucian carp Carassius auratus challenged with Aeromonas hydrophila. Small RNA libraries of the gills were constructed and sequenced on the Illumina HiSeq 2000 platform. A total of 1,165 differentially expressed miRNAs (DEMs) were identified in gills, of which 539 known and 7 unknown DEMs were significantly screened (p<0.05). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that the potential target genes/proteins were primarily involved in 33 immune-related pathways, in which the inflammatory responses were focused on the Toll-like receptor (TLR), mitogen-activated protein kinase (MAPK), and nuclear factor kappa B (NF-κB) signaling pathways. Moreover, the expression levels of 14 key miRNAs (e.g., miR-10, miR-17, miR-26a, miR-144, miR-145, and miR-146a) and their target genes (e.g., TNFα, TLR4, NF-κB, TAB1, PI3K, and IRAK1) were verified. In addition, the protein levels based on isobaric tags for relative and absolute quantification (iTRAQ) were significantly associated with the results of the quantitative real-time PCR (qRT-PCR) analysis (p<0.01). miR-17/pre-miR-17 were identified in the regulation expression of the NF-κB target gene, and the phylogenetic tree analysis showed that the pre-miR-17 of C. auratus with the closest similarity to the zebrafish Danio rerio is highly conserved in teleosts. This is the first report of the multi-omics analysis of the miRNAs and proteins in the gills of C. auratus infected with A. hydrophila, thus enriching knowledge on the regulation mechanism of the local immune response in Cyprinidae fish.

Characterization of CD3γ/δ gene and its immune response in Qihe crucian carp Carassius auratus after challenged by Aeromonas veronii and Poly(I:C)

CD3γ/δ found in non-mammalian vertebrates is a CD3 homolog with structural characteristics similar to both mammalian CD3γ and CD3δ, and plays important roles in T cell recognization and immune response in fish. In this study, the full-length of CD3γ/δ from Qihe crucian carp (named CaCD3γ/δ) was cloned and characterized, then the expression response profiles and potential immune functions was explored after Aeromonas veronii and Poly(I:C) challenge. The results showed that the full-length of CaCD3γ/δ was 819 bp including a 5ʹ-UTR of 141 bp, a 3ʹ-UTR of 168 bp, and an ORF of 510 bp encoding a putative 169-aa protein with an estimated MW of 18.71 kD and a theoretical pI of 8.77. The protein sequence of CaCD3γ/δ contained a Leu-Leu and a CXXXC motif in the extracellular domain, and an ITAM and a Leu-Ile motif in the cytoplasm, and a residue of Asn in the transmembrane. CaCD3γ/δ was constitutively expressed in the spleen, liver, gill, and blood of Qihe crucian carp. After the carp were challenged with Poly(I:C) and Aeromonas veronii, the mRNA expression levels of CaCD3γ/δ were significantly changed in the spleen, head kidney, intestine and gill, according to the results of qPCR. However, compared with A. veronii, Poly(I:C) challenge can rapidly induce the CaCD3γ/δ expression levels in head kidney, intestine and spleen, which suggested CaCD3γ/δ may be differentially modulated by different pathogens. Moreover, the results of immunohistochemical analysis showed that the CaCD3γ/δ+ secreted cells in the spleen and gills of Qihe crucian were increased after challenged with Poly(I:C), as well as the spleen challenged with A. veronii, but at different levels. Combined with the fact that vascular congestion, necrosis of parenchymal cells, and inflammatory cells including lymphocytes infiltration were also observed in the gill and spleen of Qihe crucian carp treated with A. veronii and Poly(I:C) revealed by pathological analysis, it was predicted that CaCD3γ/δ+ T lymphocytes may participated in the immune response against pathogens. This study will contribute to understand the important role of CaCD3γ/δ+ T lymphocytes in the immune response of Qihe crucian carp, and provide new insights for the prevention and treatment of the diseases of Qihe crucian carp.

Molecular characteristics and the roles of CaASC and its restriction to Aeromonas hydrophila in Carassius auratus

Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), as a critical adaptor molecule in inflammasome complexes, plays an important role in mediating inflammation reaction. In this study, the complete cDNA of ASC gene with 891 bp was cloned in Qihe crucian carp Carassius auratus (named as CaASC), which was composed of a 5′-UTR of 36 bp, a 3′-UTR of 252 bp, and an ORF of 603 bp encoded 200 amino acids with a predicted isoelectric point of 5.61 and a molecular mass of 22.0 kDa. Multiple sequence alignment and motif analysis revealed that CaASC contained a conserved N-terminal Pyrin domain (PYD) and a C-terminal Caspase recruitment domain (CARD). CaASC mRNA and protein expressions were detected in selected tissues, with the highest mRNA level in the spleen. Meanwhile, CaASC gene expressions were clearly altered in intestine, gill, skin, spleen, liver and head kidney of fish challenged by Aeromonas hydrophila, LPS, and polyI:C, respectively. The recombined proteins of CaASC with fluorescent tag were over-expressed in transfected 293T cells, and the green specks were observed obviously and located in the cytoplasm. Furthermore, knockdown of CaASC reduced the expression of IL-1β and promoted the bacterial colonization in fish tissues, while overexpression of CaASC increased the expression of IL-1β and hampered the bacterial colonization in these tissues. Taken together, these results identified the molecular characteristics of CaASC in C. auratus, and revealed its role in regulating IL-1β expression and restricting bacterial infection in vivo.

Molecular characterization of NLRC3 and its interaction with other inflammasome components and regulation on the bacterial colonization in Qihe crucian carp Carassius auratus

The NLRC as a very unique subfamily of Nod like receptors (NLRs), is believed to play an important role in the bacterial recognition of animals. However, the molecular characterization and immunological role of NLRC3 in Carassius auratus is little known. In this study, we identified and achieved a complete cDNA sequence of NLRC3 gene in Qihe crucian carp Carassius auratus (named as CaNLRC3). The full-length cDNA sequence of CaNLRC3 was composed of 3823 bp, which contained a 5′-UTR of 251 bp, a 3′-UTR of 158 bp, and an open reading frame (ORF) of 3414 bp encoded 1137 amino acids with a predicted isoelectric point of 8.25 and a molecular mass of 124.1 kDa, characterized with a caspase recruitment domain (CARD) at N-terminus. The mRNA expression of CaNLRC3 was detected to be constitutive in all the examined tissues, with the high expression levels in spleen, skin and intestine. After challenges with bacteria or pathogenic analogue, expression levels of CaNLRC3 gene were strongly induced. Co-localization and co-immunoprecipitation results found that CaNLRC3 can assemble CaASC through CARD domain interaction, then CaASC associated with CaCaspase-1a, presumably to assemble the NLRC3 inflammasome complex. The overexpression of CaNLRC3 could significantly increase the mRNA expression of IL-1β, and promote the bacterial elimination and result in the decrease of bacterial loading in liver, spleen and kidney after bacterial infection. Vice versa, the knockdown of CaNLRC3 could obviously reduce IL-1β expression at mRNA level, and bacterial loading was significantly increased in tissue. Taken together, CaNLRC3 is proved to be a pivotal cytosolic innate immune receptor in this study, which is acted as the potential component of inflammasome to regulate inflammation reaction, and could modify bacterial loading in tissue and restrict bacterial infection in teleost.

Comparison of growth performance, feed utilization and morphology between homologous and heterologous juvenile Qihe crucian carp Carassius auratus

Qihe crucian carp (Carassius auratus) is a valuable fish species in China that has two reproduction modes, unisexual gynogenesis and sexual reproduction. However, little is known about the differences between offspring of Qihe C. auratus produced by these two reproduction modes. A thorough multi-aspects comparison of the offspring produced via the two reproduction modes would provide essential guide to aquaculturists in the artificial breeding and farming of Qihe C. auratus. Therefore, this study compared the growth performance, feed utilization, and morphological traits between homologous and heterologous juvenile Qihe C. auratus after three-month successive culture. Noticeably, homologous fish grew faster than heterologous fish in terms of the body size and final body weight; the feed intake, protein efficiency ratio, and the values of all 15 measured traits of homologous fish were significantly higher than that of heterologous fish. However, for external morphology, heterologous fish had relatively larger head size and thicker body. Additionally, the significant direct effects of the morphological traits on body weight varied between homologous and heterologous fish at different culture stages. Therefore, six independent regression equations were constructed to evaluate the relationships between different morphological traits and body weight. Further, in some traits, the homologous and heterologous fish presented discrepant allometric growth patterns. Finally, discriminant function equations (total accuracy: 92.78%) were successfully constructed based on morphological indexes to ease the identification of homologous and heterologous Qihe C. auratus. These findings suggest that homologous fish can grow faster, but heterologous fish have a thicker body, which is of higher economical value and a key parameter that determines quality and price.

Skin immune response to Aeromonas hydrophila infection in crucian carp Carassius auratus revealed by multi-omics analysis

Fish skin is an essential protective barrier and functions as the first line of immune defense against pathogens. However, the molecular mechanism at the proteome-level remains unclear in the skin of fish. In this study, the comparative proteomics of skin immune responses of crucian carp Carassius auratus infected with Aeromonas hydrophila was investigated by isobaric tags for relative and absolute quantification (iTRAQ), two-dimensional gel electrophoresis combined with mass spectrometry (2-DE/MS) as well as high-throughput transcriptome (RNA-seq) techniques. A total of 241 and 178 differentially expressed proteins (DEPs) at 6 and 12 h post-infection (hpi) were respectively identified by iTRAQ, and key-DEPs were furtherly verified with 2-DE/MS analysis. GO and KEGG analysis showed that these DEPs were mostly related to metabolism, regulation of the cytoskeleton, stress and immune responses. Co-association results of proteome and transcriptome revealed the lysozyme (LYZ), complement C3, DnaJ (Hsp40) homolog subfamily C member 8 (DNAJC8) and allograft inflammatory factor 1-like (AIF1L) play important roles in skin immune responses of crucian carp. The significantly up-regulated expression of detected immune-related genes (c3, mapk3, f5, nlr, hsp90, itgb2, fnl, flnca, p47, mhc and pros1) were validated by qRT-PCR analysis. To our knowledge, this is first report on multi-omics analysis of the differential proteomics for the skin immune response of C. auratus against A.hydrophila infection, which contribute to the understanding the mechanisms of skin mucosal immunity in cyprinid fish.

Nutrient dynamics and balance of zero–water exchange ponds of grass carp, crucian carp and bighead carp

This study aimed to investigate the nutrient dynamics and balance of zero–water exchange ponds of grass carp Ctenopharyngodon idella, crucian carp Carassius auratus and bighead carp Aristichthys nobilis, and explain advantages of the zero–water exchange mode from the perspective of material flow. This study was conducted for two years. The polyculture ponds of grass carp, crucian carp and bighead carp were grouped into the treatment group using the zero–water exchange mode, while the ordinary polyculture ponds of grass carp, bighead carp, and crucian carp were grouped into the control group. The results showed that 1) the treatment group reduced water conductivity, dissolved solids and sediment organic carbon significantly (P < 0.05), and improved water transparency significantly (P < 0.05); 2) the carbon, nitrogen, and phosphorus accumulation amount and rate in the water of the treatment group were significantly lower (P < 0.05) than those in the control group, so was the sediment accumulation rate of organic carbon and nitrogen (P < 0.05); 3) the carbon, nitrogen, and phosphorus utilization efficiency of stocked fish in the treatment group were significantly higher (P < 0.05) than those in the control group, with an increase of 29.49%, 21.72%, and 20.65%, respectively. Therefore, the zero–water exchange pond was a green and efficient aquaculture mode, which could improve water quality, reduce nutrient accumulation, and improve the utilization efficiency of nutrients effectively. Considering the nutrient emissions from aquaculture in China, the zero–water exchange mode has a good value for promotion.