Search Results (39)

Polydeoxyribonucleotide (PDRN) has emerged as a potent bioactive compound with proven efficacy in wound healing, tissue regeneration, and anti-inflammatory applications and is predominantly derived from salmonid gonads. However, this study presents a groundbreaking advancement by successfully extracting and characterizing PDRN from microbial sources, specifically Lactobacillus rhamnosus, marking the first report to utilize microbial-, biome-, or Lactobacillus-derived PDRN (L-PDRN). The findings demonstrate the enhanced biological properties of L-PDRN over traditional salmon-derived PDRN across several assays. L-PDRN exhibited superior antioxidant activity, with significantly higher SOD-like and DPPH radical scavenging activities compared to PDRN, particularly at higher concentrations. In wound-healing assays, L-PDRN demonstrated superior efficacy in promoting cell migration and wound closure, even under inflammatory conditions induced by tumor necrosis factor (TNF-α). Additionally, L-PDRN demonstrated the potential for enhanced immunostimulatory effects under non-inflammatory conditions while maintaining anti-inflammatory properties under lipopolysaccharide (LPS) stimulation. Electrophoretic analysis revealed that L-PDRN consists of smaller DNA fragments (under 100 bp) compared to salmon-derived PDRN (200–800 bp), suggesting greater bioavailability and skin absorption. Mechanistic studies confirmed that L-PDRN activates the focal adhesion kinase (FAK) and protein kinase B (AKT) signaling pathway through the A2A receptor, similar to PDRN, while also engaging alternative pathways for p38 and ERK phosphorylation, highlighting its signaling versatility. This study underscores the potential of L-PDRN as a multifunctional and sustainable alternative to salmon-derived PDRN, offering enhanced bioactivity, scalability, and environmental benefits. The novel approach of utilizing microbial-derived PDRN opens new avenues for therapeutic applications in oxidative stress management, tissue regeneration, and immune modulation, paving the way for a paradigm shift in PDRN sourcing and functionality. Full article

The major histocompatibility complex (MHC) consists of genes involved in immune response and molecular discrimination between self and non-self. MHC genes are the most polymorphic in vertebrates. The origin and maintenance of polymorphism in MHC genes in populations is still unresolved. Mechanisms such as sexual selection and heterozygote advantage have been suggested as explanations for this high variability. In this study, a farmed population of rainbow trout (Oncorhynchus mykiss) characterized by the presence of specific MHC class IIB gene haplotypes at a frequency higher (30%) than that expected from random matings was investigated. Therefore, it was hypothesized that disassortative matings occur with an adaptive advantage for females, resulting in improved reproductive performance when mated with individuals with similar MHC haplotypes. Genetic analyses of the breeders were performed to define the MHC haplotypes and to perform specific matings. The effect of mating was evaluated by analyzing the survival rate of the offspring at various stages of incubation until swim-up. The reproductive performance of the offspring derived from specimens with similar haplotypes showed a better survival trend during the first life stages and reduced malformations. The results obtained are in contrast with the heterozygous advantage theory, therefore it was hypothesized, as for other salmonid species, the presence of a positive selection towards locally adapted MHC genes that promotes reproduction between genetically similar individuals. Full article

Salmonid fishes provide an important indicator of climate change given their reliance on cold water. We evaluated temporal changes in the density of stream-dwelling brook trout (Salvelinus fontinalis) from surveys conducted over a 36-year period (1988–2023) by the Maryland Department of Natural Resources in Eastern North America. Nonparametric trend analyses revealed decreasing densities of adult fish (age 1+) in 19 sites (27%) and increases in 5 sites (7%). In contrast, juvenile fish (age 0) densities decreased in 4 sites (6%) and increased in 10 sites (14%). Declining adult brook trout trends were related to atmospheric warming rates during the study period, and this relationship was stronger than the effects of land use change or non-native brown trout. In contrast, juvenile fish trends generally increased with elevation but were not related to air temperature trends or land use change. Our analysis reveals significant changes in several brook trout populations over recent decades and implicates warming atmospheric conditions in population declines. Our findings also suggest the importance of temperature for adult survival rather than recruitment limitation in brook trout population dynamics. Full article

Our study demonstrates the first application of the salmonid alphavirus-based replicon vector system (pSAV) as a DNA vaccine in a non-salmonid fish species, in common carp (Cyprinus carpio) against spring viraemia of carp virus (SVCV). SAV replicon encoding the glycoprotein of the SVCV was used as a DNA-layered plasmid, and its efficacy was compared with a previously described conventional DNA vaccine construct (pcDNA3.1 based vector) and with a control group (pcDNA3.1-empty-plasmid) in an SVCV challenge at a water temperature of 14 ± 1 °C. Vaccine prototypes were administered intramuscularly at a dose of 0.1 µg/g of fish (n = 25 per group). The DNA-layered SAV replicon resulted in 88% survival, compared to around 50% in all other groups. The DNA-layered pSAV vaccination induced the innate immune genes at the injection site, and increased IgM upregulation was also observed. Our preliminary results show that the SAV-based replicon construct may serve as a potential vaccine candidate for the protection of non-salmonid fish in the future provided that further clinical and field trials confirm its efficiency. Full article

The bacterium Yersinia ruckeri causes enteric redmouth disease in salmonids and hence has substantial economic implications for the farmed fish industry. The Norwegian Y. ruckeri outbreak isolate NVH_3758 carries a relatively uncharacterized plasmid, pYR4, which encodes both type 4 pili and a type 4 secretion system. In this study, we demonstrate that pYR4 does not impose a growth burden on the Y. ruckeri host bacterium, nor does the plasmid contribute to twitching motility (an indicator of type 4 pilus function) or virulence in a Galleria mellonella larval model of infection. However, we show that pYR4 is conjugative. We also reveal, through mutagenesis, that pYR4 encodes a functional post-segregational killing system, HigBA, that is responsible for plasmid maintenance within Y. ruckeri. This is the first toxin–antitoxin system to be characterized for this organism. Whilst further work is needed to elucidate the virulence role of pYR4 and whether it contributes to bacterial disease under non-laboratory conditions, our results suggest that the plasmid possesses substantial stability and transfer mechanisms that imply importance within the organism. These results add to our understanding of the mobile genetic elements and evolutionary trajectory of Y. ruckeri as an important commercial pathogen, with consequences for human food production. Full article

Background: This study was conducted to investigate whether mRNA vaccine technology could be adapted for the ectothermic vertebrate Atlantic salmon (Salmo salar). Lipid nanoparticle (LNP) technology has been developed and optimized for mRNA vaccines in mammals, stabilizing mRNA and facilitating its delivery into cells. However, its utility at the temperatures and specific biological environments present in ectotherms remains unclear. In addition, it is unknown if modified mRNA containing non-canonical nucleotides can correctly translate in salmonid cells. Methods: We used an mRNA transcript coding for enhanced green fluorescence protein, flanked by the untranslated regions of the hemagglutinin-esterase gene of the infectious salmon anemia virus, and a 120-base-long poly(A) tail. The mRNA was generated via in vitro transcription where uridine residues were replaced with N1-methyl-pseudouridines, and then encapsulated in LNPs. Results: When transfected into the salmonid cell line CHH-1, the mRNA-LNP construct induced expression of EGFP. Furthermore, when mRNA-LNPs were injected intramuscularly into salmon, in vivo protein expression was demonstrated via immunohistochemistry. EGFP was observed in cells infiltrating the spaces between muscle cells in a focal inflammatory response. Conclusion: The results indicate that N1-methyl-pseudouridine-modified mRNA encapsulated in LNPs can be used to express antigens of interest in salmonid fish. Full article

The production and release of cortisol during stress responses are key regulators of growth in teleosts. Understanding the molecular responses to cortisol is crucial for the sustainable farming of rainbow trout (Oncorhynchus mykiss) and other salmonid species. While several studies have explored the genomic and non-genomic impacts of cortisol on fish growth and skeletal muscle development, the long-term effects driven by epigenetic mechanisms, such as cortisol-induced DNA methylation, remain unexplored. In this study, we analyzed the transcriptome and genome-wide DNA methylation in the skeletal muscle of rainbow trout seven days after cortisol administration. We identified 550 differentially expressed genes (DEGs) by RNA-seq and 9059 differentially methylated genes (DMGs) via whole-genome bisulfite sequencing (WGBS) analysis. KEGG enrichment analysis showed that cortisol modulates the differential expression of genes associated with nucleotide metabolism, ECM-receptor interaction, and the regulation of actin cytoskeleton pathways. Similarly, cortisol induced the differential methylation of genes associated with focal adhesion, adrenergic signaling in cardiomyocytes, and Wnt signaling. Through integrative analyses, we determined that 126 genes showed a negative correlation between up-regulated expression and down-regulated methylation. KEGG enrichment analysis of these genes indicated participation in ECM-receptor interaction, regulation of actin cytoskeleton, and focal adhesion. Using RT-qPCR, we confirmed the differential expression of lamb3, itga6, limk2, itgb4, capn2, and thbs1. This study revealed for the first time the molecular responses of skeletal muscle to cortisol at the transcriptomic and whole-genome DNA methylation levels in rainbow trout. Full article

Winter ulcer disease is a health issue in the Atlantic salmonid aquaculture industry, mainly caused by Moritella viscosa. Although vaccination is one of the effective ways to prevent bacterial outbreaks in the salmon farming industry, ulcer disease related to bacterial infections is being reported on Canada’s Atlantic coast. Here, we studied the immune response of farmed immunized Atlantic salmon to bath and intraperitoneal (ip) M. viscosa challenges and evaluated the immunogenicity of M. viscosa cell components. IgM titers were determined after infection, post boost immunization, and post challenge with M. viscosa. IgM⁺ (B cell) in the spleen and blood cell populations were also identified and quantified by 3,3 dihexyloxacarbocyanine (DiOC6) and IgM-Texas red using confocal microscopy and flow cytometry. At 14 days post challenge, IgM was detected in the serum and spleen. There was a significant increase in circulating neutrophils 3 days after ip and bath challenges in the M. viscosa outer membrane vesicles (OMVs) boosted group compared to non-boosted. Lymphocytes increased in the blood at 7 and 14 days after the ip and bath challenges, respectively, in OMVs boosted group. Furthermore, a rise in IgM titers was detected in the OMVs boosted group. We determined that a commercial vaccine is effective against M. viscosa strain, and OMVs are the most immunogenic component of M. viscosa cells. Full article

Furunculosis, caused by Aeromonas salmonicida, poses a significant threat to both salmonid and non-salmonid fish in diverse aquatic environments. This study explores the genomic intricacies of re-emergent A. salmonicida outbreaks in Atlantic salmon (Salmo salar). Previous clinical cases have exhibited pathological characteristics, such as periorbital hemorrhages and gastrointestinal abnormalities. Genomic sequencing of three Chilean isolates (ASA04, ASA05, and CIBA_5017) and 25 previously described genomes determined the pan-genome, phylogenomics, insertion sequences, and restriction-modification systems. Unique gene families have contributed to an improved understanding of the psychrophilic and mesophilic clades, while phylogenomic analysis has been used to identify mesophilic and psychrophilic strains, thereby further differentiating between typical and atypical psychrophilic isolates. Diverse insertion sequences and restriction-modification patterns have highlighted genomic structural differences, and virulence factor predictions can emphasize exotoxin disparities, especially between psychrophilic and mesophilic strains. Thus, a novel plasmid was characterized which emphasized the role of plasmids in virulence and antibiotic resistance. The analysis of antibiotic resistance factors revealed resistance against various drug classes in Chilean strains. Overall, this study elucidates the genomic dynamics of re-emergent A. salmonicida and provides novel insights into their virulence, antibiotic resistance, and population structure. Full article

Salmon lice are one of the biggest challenges to sustainable salmonid aquaculture. The species display high evolutionary potential, which is evident by its development of resistance to numerous chemical compounds used for delousing. In response to this, salmon farms now use non-chemical delousing methods to minimize the damage done by salmon lice, including heavy reliance on cleaner fish. Anecdotal reports from farmers and fish health personnel in areas where cleaner fish are used have suggested that salmon lice are becoming less pigmented, potentially making them harder for cleaner fish to visually detect. This experiment investigated changes in the pigmentation of salmon lice in relation to the use of cleaner fish, louse stage and sex, temperature, preferred salmon swimming depth, daylength, and salinity. Salmon lice were sampled from snorkel cages on a commercial salmon farm where three cages were stocked with farmed lumpfish and ballan wrasse, and three cages were without cleaner fish. Water temperature, salinity, and depth were recorded using a conductivity, temperature, and depth recorder. Pigmentation was measured via photographic analysis of individual lice. Although louse pigmentation varied considerably throughout the experiment, using cleaner fish throughout a single production cycle did not reduce average louse pigmentation compared to control cages. On average, male lice were significantly darker pigmented than females, but otherwise there were no patterns in louse pigmentation in relation to life stage, salinity, temperature, or daylength. Salmon lice exhibit a high degree of evolvability and have become resistant to every chemical removal treatment developed thus far. The present data suggest that, with the densities and species of cleaner fish commonly used in commercial salmon production, there is not strong directional selection on louse pigmentation. Lice, at least with regard to visual appearance, are not likely to adapt in a way which reduces cleaner fish efficacy anytime soon. Full article

NF-κB signalling is largely controlled by the family of ‘inhibitors of NF-κB’ (IκB). The relevant databases indicate that the genome of rainbow trout contains multiple gene copies coding for iκbα (nfkbia), iκbε (nfkbie), iκbδ (nkfbid), iκbζ (nfkbiz), and bcl3, but it lacks iκbβ (nfkbib) and iκbη (ankrd42). Strikingly, three nfkbia paralogs are apparently present in salmonid fish, two of which share a high sequence identity, while the third putative nfkbia gene is significantly less like its two paralogs. This particular nfkbia gene product, iκbα, clusters with the human IκBβ in a phylogenetic analysis, while the other two iκbα proteins from trout associate with their human IκBα counterpart. The transcript concentrations were significantly higher for the structurally more closely related nfkbia paralogs than for the structurally less similar paralog, suggesting that iκbβ probably has not been lost from the salmonid genomes but has been incorrectly designated as iκbα. In the present study, two gene variants coding for iκbα (nfkbia) and iκbε (nfkbie) were prominently expressed in the immune tissues and, particularly, in a cell fraction enriched with granulocytes, monocytes/macrophages, and dendritic cells from the head kidney of rainbow trout. Stimulation of salmonid CHSE-214 cells with zymosan significantly upregulated the iκbα-encoding gene while elevating the copy numbers of the inflammatory markers interleukin-1-beta and interleukin-8. Overexpression of iκbα and iκbε in CHSE-214 cells dose-dependently quenched both the basal and stimulated activity of an NF-κB promoter suggesting their involvement in immune-regulatory processes. This study provides the first functional data on iκbε—versus the well-researched iκbα factor—in a non-mammalian model species. Full article

Environmental stressors can disrupt the relationship between the microbiota and the host and lead to the loss of its functions. Among them, bacterial infection caused by Aeromonas salmonicida, the causative agent of furunculosis, results in high mortality in salmonid aquaculture. Here, rainbow trout were exposed to A. salmonicida achromogenes and its effects on the taxonomic composition and structure of the microbiota was assessed on different epithelia (gills, skin, and caudal fin) at 6 and 72 h post-infection (hpi) using the V1–V3 region of the 16S rRNA sequencing. Moreover, the infection by the pathogen and immune gene responses were evaluated in the head kidney by qPCR. Our results suggested that α-diversity was highly diverse but predominated by a few taxa while β-diversity was affected very early by infection in the gills after 6 h, subsequently affecting the microbiota of the skin and caudal fin. A dysbiosis of the microbiota and an increase in genera known to be opportunistic pathogens (Aeromonas, Pseudomonas) were also identified. Furthermore, an increase in pro-inflammatory cytokines and virulence protein array (vapa) was observed in trout head kidney as soon as 6 hpi and remained elevated until 72 hpi, while the anti-inflammatory genes seemed repressed. This study suggests that the infection by A. salmonicida achromogenes can alter fish microbiota of gills in the few hours post-infection. This result can be useful to develop a non-invasive technique to prevent disease outbreak in aquaculture. Full article

In recent years, the hydropower development of the lower Mekong River has accelerated, accompanied by habitat loss and fragmentation. We conducted two experiments using video recordings and traps to evaluate the effectiveness of a nature-like rock ramp bypass in the Sesan River in 2019 and 2021. The results show that the fishway provides both upstream and downstream passage for at least 24 non-salmonid species of fish. The vast majority of fish choose to ascend from July to September, especially in August, and hardly between October and November. The fish inside the fishway prefer to move during the daytime (6:00–18:00), especially during August and September. An excessive water depth at the entrance can lower the number of ascending fish, whereas a higher water depth at the exit can cause the opposite result. Nevertheless, the size of fish monitored exhibits a decreasing trend, suggesting the nature-like bypass cannot completely mitigate the impact caused by this impassable Sesan Ⅱ dam. Therefore, a quantitative assessment of the bypass is highly encouraged, whereas the selection of the tracked fish species and experimental period requires considerable deliberation. This study alleviates the dilemma of insufficient fishway evaluation in tropical countries, which can provide researchers with data support on future non-salmonid fishway designs. Full article

The precision fish farming concept has been widely investigated in research and is highly desirable in aquaculture as it creates opportunities for precisely controlling and monitoring fish cultivation processes and increasing fish welfare. The automatic identification of individual fish could be one of the keys to enabling individual fish treatment. In a previous study, we already demonstrated that the visible patterns on a fish’s body can be used for the non-invasive individual identification of fishes from the same species (with obvious skin patterns, such as salmonids) over long-term periods. The aim of this study was to verify the possibility of using fully-automatic non-invasive photo-identification of individual fish based on natural marks on the fish’s body without any obvious skin patterns. This approach is an alternative to stressful invasive tagging and marking techniques. Scale patterns on the body and operculum, as well as lateral line shapes, were used as discriminative features for the identification of individuals in a closed group of fish. We used two fish species: the European seabass Dicentrarchus labrax and the common carp Cyprinus carpio. The identification method was tested on four experimental data sets for each fish species: two separate short-term data sets (pattern variability test) and two long-term data sets (pattern stability test) for European seabass (300 individual fish) and common carp (32 individual fish). The accuracy of classification was 100% for both fish species in both the short-term and long-term experiments. According to these results, the methods used for automatic non-invasive image-based individual-fish identification can also be used for fish species without obvious skin patterns. Full article

During the last 150 years, the trout-culture industry focused on enhancing trout populations by stocking, in response to the growing anglers’ demand and the habitat degradation associated to the rapid urbanization and hydropower development. The industrialized north of Italy, home to the Italian Alpine and subalpine trout populations, is the source of most of the revenues of the national trout-culture industry. Its rapid growth, and the massive introduction of non-native interfertile trouts eroded the genetic diversity of native lineages, leading to harsh confrontations between scientists, institutions, and sportfishing associations. We review here the state of the art of the taxonomy and distribution of the northern Italian native trouts, presenting both scientific results and historical documentation. We think the only native trouts in this region are Salmo marmoratus, widespread in this region, plus small and fragmented populations of S. ghigii, present only in the South-western Alps. We strongly recommend the interruption of stocking of domesticated interfertile non-native trouts in this area, and recommend the adoption of Evolutionary Significant Units for salmonid fishery management. We further propose future research directions for a sustainable approach to the conservation and ecosystem management of the fishery resources and inland waters of northern Italy. Full article