Silver carp mediated biological control techniques are often advocated for controlling cyanobacteria blooms in eutrophic water, which are often enriched with arsenic (As). However, the transfer and fate of As during the biological control of cyanobacteria blooms by silver carp in As-rich eutrophic water remain unclear. Based on the simulated ecosystem experiment, the accumulation of As in silver carp and the transfer and fate of As in the water-algae-silver carp system during Microcystis aeruginosa blooms controlled by silver carp were investigated. Microcystis aeruginosa showed high tolerance to As(V). The accumulation of As in different tissues of silver carp was different, as follows: intestine > liver > gill > skin > muscle. After silver carp ingested As-rich Microcystis aeruginosa, As accumulation in the intestine, liver, gill, and skin of silver carp was enhanced under the action of digestion and skin contact. Compared with the system without algal, As accumulation in the intestine, liver, gill, and skin of silver carp increased by 1.1, 3.3, 3.3, and 9.6 times, respectively, after incubation for 30 days in the system with Microcystis aeruginosa, while the accumulation of As in the muscle was only slightly increased by 0.56 mg/kg. This work revealed the transfer and fate of As during algal control by silver carp, elucidated the accumulation mechanism of As in water-algae-silver carp system, enriched our understanding of As bioaccumulation and transformation in As-rich eutrophication water, and provided a scientific basis for assessing and predicting As migration and enrichment in water-algae-silver carp system.

Medical imaging techniques such as digital radiography and ultrasonography are non-invasive and provide precise results for examining internal organs and structures within fish. Their effectiveness can be further enhanced by using body parts like scales as markers for the organs beneath them. This study utilized the number of scales as landmarks in digital radiography and ultrasonography to non-invasively evaluate the muscles, bones, and images of internal and reproductive organs of common carp (Cyprinus carpio). Digital radiography was performed in the dorsoventral and lateral views of the fish, whereas ultrasonography was conducted in longitudinal and transverse views on sequence scale numbers with brightness and colour Doppler-modes. Digital radiography of the common carp revealed the whole-body morphology, including the bony parts from the head, pectoral fins, dorsal fins, pelvic fins, anal fins, and vertebrae to the tail that appeared radiopaque. Internal organs were also observed, with the swim bladder and heart appeared radiolucent, while the intestines, liver, testes, and ovaries appeared radiopaque. Ultrasonography in brightness mode displayed the digestive organs, reproductive organs, and muscle thickness. Additionally, colour Doppler mode demonstrated blood flow within the heart\'s ventricle.

BACKGROUND: Neither a TYRP1-mediated highly conserved genetic network underlying skin color towards optimum defense nor the pathological tendency of its mutation is well understood. The Oujiang Color Common Carp (Cyprinus carpio var. color) as a model organism, offering valuable insights into genetics, coloration, aquaculture practices, and environmental health. Here, we performed a comparative skin transcriptome analysis on TYRP1 mutant and wild fishes by applying a conservative categorical approach considering different color phenotypes.
RESULTS: Our results reveal that an unusual color phenotype may be sensitized with TYRP1 mutation as a result of upregulating several genes related to an anti-inflammatory autoimmune system in response to the COMT-mediated catecholamine neurotransmitters in the skin. Particularly, catecholamines-derived red/brown, red with blue colored membrane attack complex, and brown/grey colored reduced eumelanin are expected to be aggregated in the regenerated cells.
CONCLUSIONS: It is, thus, concluded that the regenerated cells with catecholamines, membrane attack complex, and eumelanin altogether may contribute to the formation of the unusual (coffee-like) color phenotype in TYRP1 mutant.

This study examines the levels of heavy metals in polyculture fish (Labeo rohita, Cyprinus carpio, and Catla catla), water, and sediment in Tanda Dam, Kohat, Pakistan, aiming to understand environmental and health risks. Samples of fish, water, and sediment were collected from 3 fish farms, and heavy metal concentrations were measured using a Flame Atomic Absorption Spectrophotometer (AAS). Results reveal that C. catla exhibited significantly higher (p < 0.05) levels of Zn than other fish species. Conversely, C. carpio showed significantly higher (p < 0.05) concentrations of Pb, Cd, Cr, Mn, Cu, As, and Ni than other species. The heavy metal hierarchy in C. carpio was found to be Zn > Cu > Pb > Cr > Cd > Mn > As > Ni. While heavy metal levels in L. rohita and C. catla generally fell within reference ranges, exceptions were noted for Zn, Pb, and Cd. Conversely, in C. carpio, all metals exceeded reference ranges except for Cu and Ni. Principal Component Analysis (PCA) indicated a close relationship between water and sediment. Additionally, cluster analysis suggested that C. catla formed a distinct cluster from L. rohita and C. carpio, implying different responses to the environment. Despite concerns raised by the Geoaccumulation Index (Igeo) and Contamination Factor (CF), particularly for Cd, which exhibited a high CF. Furthermore, Hazard Index (HI) values for all three fish species were below 1, suggesting low health risks. However, elevated Igeo and CF values for Cd suggest significant pollution originating from anthropogenic sources. This study underscores the importance of monitoring heavy metals in water for both environmental preservation and human health protection. Future research efforts should prioritize pollution control measures to ensure ecosystem and public health safety.

UNASSIGNED: Red blood cells (RBCs), also known as erythrocytes, are underestimated in their role in the immune system. In mammals, erythrocytes undergo maturation that involves the loss of nuclei, resulting in limited transcription and protein synthesis capabilities. However, the nucleated nature of non-mammalian RBCs is challenging this conventional understanding of RBCs. Notably, in bony fishes, research indicates that RBCs are not only susceptible to pathogen attacks but express immune receptors and effector molecules. However, given the abundance of RBCs and their interaction with every physiological system, we postulate that they act in surveillance as sentinels, rapid responders, and messengers.
UNASSIGNED: We performed a series of in vitro experiments with Cyprinus carpio RBCs exposed to Aeromonas hydrophila, as well as in vivo laboratory infections using different concentrations of bacteria.
UNASSIGNED: qPCR revealed that RBCs express genes of several inflammatory cytokines. Using cyprinid-specific antibodies, we confirmed that RBCs secreted tumor necrosis factor alpha (TNFα) and interferon gamma (IFNγ). In contrast to these indirect immune mechanisms, we observed that RBCs produce reactive oxygen species and, through transmission electron and confocal microscopy, that RBCs can engulf particles. Finally, RBCs expressed and upregulated several putative toll-like receptors, including tlr4 and tlr9, in response to A. hydrophila infection in vivo.
UNASSIGNED: Overall, the RBC repertoire of pattern recognition receptors, their secretion of effector molecules, and their swift response make them immune sentinels capable of rapidly detecting and signaling the presence of foreign pathogens. By studying the interaction between a bacterium and erythrocytes, we provide novel insights into how the latter may contribute to overall innate and adaptive immune responses of teleost fishes.

Iron deficiency is widespread throughout the world, supplementing sufficient iron or improving the bioavailability of iron is the fundamental strategy to solve the problem of iron scarcity. Herein, we explored a new form of iron supplement, iron chelates of silver carp scales (SCSCP-Fe) were prepared from collagen peptide of silver carp scales (SCSCP) and FeCl2·4H2O, the effects of external environment and simulated gastrointestinal digestive environment on the stability of SCSCP-Fe and the structural changes of peptide iron chelates during digestion were investigated. The results of in vitro iron absorption promotion showed that the iron bioavailability of SCSCP-Fe was higher than that of FeSO4. Two potential high iron chelating peptides DTSGGYDEY (DY) and LQGSNEIEIR (LR) were screened and synthesized from the SCSCP sequence by molecular dynamics and LC-MS/MS techniques. The FTIR results displayed that the binding sites of DY and LR for Fe2+ were the carboxyl group, the amino group, and the nitrogen atom on the amide group on the peptide. ITC results indicated that the chelation reactions of DY and LR with Fe2+ were mainly dominated by electrostatic interactions, forming chelates in stoichiometric ratios of 1:2 and 1:1, respectively. Both DY and LR had a certain ability to promote iron absorption. The transport of DY-Fe chelate may be a combination of the three pathways: PepT1 vector pathway, cell bypass, and endocytosis, while LR-Fe chelate was dominated by bivalent metal ion transporters. This study is expected to provide theoretical reference and technical support for the high-value utilization of silver carp scales and the development of novel iron supplements.

Hypoxia has become one of the most critical factors limiting the development of aquaculture. Crucian carp (Carassius auratus) is widely consumed fish in China, with excellent tolerance to hypoxic environment. However, the molecular mechanisms underlying hypoxia adaptation and tolerance in crucian carp remain unclear. Compared with the control, increased T-SOD, CAT, GSH-Px, T-AOC, ALT, and AST activities and MDA, TCHO, and TG contents, and decreased TP and ATP contents were observed after hypoxia stress. Based on RNA-seq, 2479 differentially expressed (DE) mRNAs and 60 DE miRNAs were identified, and numerous DE mRNAs involved in HIF signaling pathway (hif-1α, epo, vegfa, and ho), anaerobic metabolism (hk1/hk2, pfk, gapdh, pk, and ldh) and immune response (nlrp12, cxcr1, cxcr4, ccr9, and cxcl12) were significantly upregulated after hypoxia exposure. Integrated analysis found that ho, igfbp1, hsp70, and hk2 were predicted to be regulated by novel_867, dre-miR-125c-3p/novel_173, dre-miR-181b-5p, and dre-miR-338-5p/dre-miR-17a-3p, respectively, and targets of DE miRNAs were significantly enriched in MAPK signaling pathway, FoxO signaling pathway, and glycolysis/gluconeogenesis. Expression analysis showed that the mRNA levels of vegfa, epo, ho, hsp70, hsp90aa.1, igfbp1, ldh, hk1, pfk, pk, and gapdh exhibited a remarkable increase, whereas sdh and mdh were downregulated in the H3h, H12h, and H24h groups compared with the control. Furthermore, research found that hk2 is a target of dre-miR-17a-3p, overexpression of dre-miR-17a-3p significantly decreased the expression level of hk2, while the opposite results were obtained after dre-miR-17a-3p silencing. These results contribute to our understanding of the molecular mechanisms of hypoxia tolerance in crucian carp.

The mode and outcome of fish-virus interactions are influenced by many abiotic factors, among which water temperature is especially important in poikilothermic fish. Rare minnow Gobiocypris rarus is a eurythermal small cyprinid fish that is sensitive to infection with genotype II grass carp reovirus (GCRV). HSP70, a conservative and key player in heat shock response, is previously identified as an induced pro-viral factor during GCRV infection in vitro. Here, rare minnow was subjected to heat shock treatment (HST), 1 h treatment at 32 °C followed by reverting to a normal temperature of 24 °C, and subsequently challenged with GCRV-II at a dosage of 1 × LD50. The effect of HST on GCRV virulence in vivo was evaluated by calculating virus-associated mortality and viral load in both dead and survival fish. The results revealed that HST enhanced the mortality of rare minnow infected with GCRV; the fact that viral loads in the tissue samples of HST-treated fish were significantly higher than those in samples of the control group at 6, 8 d p.i. reflected a faster infection process due to HST. Quantitative gene expression analysis was further employed to show that the expression levels of Hsp70 in intestine and liver tissues from the HST group declined faster than muscle tissue after HST. HST W/O GCRV challenge upregulated proinflammatory cytokines such as MyD88 and Nf-κB, which was in consistence with the inflammation observed in histopathological analysis. This study shed light on the complexity of the interaction between fish abiotic and biotic stress response, which suggested that HST, an abiotic stress, could enhance the virulence of GCRV in Gobiocypris rarus that involved modulating the gene expression of host heat shock, as well as a pro-inflammatory response.

Grass Carp Reovirus (GCRV) and Aeromonas hydrophila (Ah) are the causative agents of haemorrhagic disease in grass carp. This study aimed to investigate the molecular mechanisms and immune responses at the miRNA, mRNA, and protein levels in grass carp kidney cells (CIK) infected by Grass Carp Reovirus (GCRV, NV) and Aeromonas hydrophilus (Bacteria, NB) to gain insight into their pathogenesis. Within 48 h of infection with Grass Carp Reovirus (GCRV), 99 differentially expressed microRNA (DEMs), 2132 differentially expressed genes (DEGs), and 627 differentially expressed proteins (DEPs) were identified by sequencing; a total of 92 DEMs, 3162 DEGs, and 712 DEPs were identified within 48 h of infection with Aeromonas hydrophila. It is worth noting that most of the DEGs in the NV group were primarily involved in cellular processes, while most of the DEGs in the NB group were associated with metabolic pathways based on KEGG enrichment analysis. This study revealed that the mechanism of a grass carp haemorrhage caused by GCRV infection differs from that caused by the Aeromonas hydrophila infection. An important miRNA-mRNA-protein regulatory network was established based on comprehensive transcriptome and proteome analysis. Furthermore, 14 DEGs and 6 DEMs were randomly selected for the verification of RNA/small RNA-seq data by RT-qPCR. Our study not only contributes to the understanding of the pathogenesis of grass carp CIK cells infected with GCRV and Aeromonas hydrophila, but also serves as a significant reference value for other aquatic animal haemorrhagic diseases.

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.