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Genomic prediction utilizes relationships between phenotypes and thousands of genetic markers dispersed across the genome of a species under selection to estimate an individual's breeding value. Viral hemorrhagic septicemia (VHS) is a devastating disease that causes high mortality in the olive flounder (Paralichthys olivaceus). Selection of VHS resistant individuals using traditional pedigree-based approaches is slow and ineffective; therefore, we investigated the potential of genomic selection to identify superior VHS-resistant individuals. In this study, various statistical models and algorithms, including the multilayer perceptron (MLP) and convolutional neural network (CNN), were compared for their prediction accuracy of breeding values. Other models assessed include pedigree-based best linear unbiased prediction (PBLUP), genomic best linear unbiased prediction (GBLUP), Bayesian A (BA), Bayesian B (BB), Bayesian C (BC), Bayesian Lasso (BL), Bayesian ridge regression (BRR), elastic net (EN), ridge regression (RR), and random forest (RF). These models were assessed for their ability to predict VHS resistance based on genomic data obtained from high-quality 70 K single nucleotide polymorphism (SNP) Affymetrix® Axiom® myDesign™ Genotyping Array from 865 animals. Furthermore, we investigated the population structure of the selected flounder population using a genomic relatedness matrix, PCA analysis, kinship coefficients, and multidimensional scaling. The results revealed that RF had the highest prediction accuracy for the three VHS-resistance traits (binary survival, days to death, and time of death), followed by BRR and GBLUP. PBLUP exhibits the lowest accuracy for these traits. Machine learning (ML) models, such as RF, outperformed traditional PBLUP and GBLUP, showing the greatest improvement over other Bayesian methods (BA, BB, and BC). The optimal parameters were determined for the best models, including specific marker sizes and sample size recommendations. The selected models and their parameters significantly improved the prediction of VHS resistance, demonstrating the potential of genomic selection to outperform the traditional pedigree-based methods. Our findings indicate that genomic selection can be more effective using ML models than conventional approaches in predicting VHS resistance and offers a means to enhance the genetic resistance of olive flounder in aquaculture to this disease. • Identifying disease resistance traits are necessary for breeding programs to create better animals. • A 70 K high density SNP array was used in the genomic prediction for VHSV traits. • The prediction accuracy ranged from 0.53 to 0.69 (lowest for PBLUP and highest for RF and CNN) • Machine learning models outperformed traditional PBLUP, GBLUP, and Bayesian models. • Increasing marker and population numbers also increase the genomic prediction ability. [ABSTRACT FROM AUTHOR]

Pink salmon (Oncorhynchus gorbuscha , Walbaum 1792) is an invasive alien species in the Fennoscandian rivers, and its growing populations cause concern for their impact on the native salmonids and river ecosystems. One of the major concerns is fish diseases and the potential ability of pink salmon to transmit pathogens to the native salmonid species. In this study, pink salmon were sampled during their spawning migration in the Rivers Tana and Neiden in northern Norway and Finland in 2021. The fish were surveyed for viral hemorrhagic septicemia virus (VHSV), infectious pancreatic necrosis virus (IPNV), infectious salmon anemia virus (ISAV), salmonid alphavirus (SAV), piscine orthoreovirus (PRV), Renibacterium salmoninarum , and Gyrodactylus salaris. No viral diseases or infections with R. salmoninarum or G. salaris were detected. However, 23 % of the fish were found infected with a parasitic roundworm, Hysterothylacium aduncum. Additionally, external anomalies, such as hemorrhages or lesions in the skin, were observed in 35 % of the fish studied, and some of the fish exhibited degenerative myopathy. Based on this study, pink salmon appears not to pose a high infection risk to the native salmonid fish populations in the Rivers Tana and Neiden. Nevertheless, the results demonstrate that pink salmon have the potential to carry salmonid pathogens. More information on the susceptibility of pink salmon to different pathogens and on the overall effect this invasive species has on native fish species is needed. As the number of migrating pink salmon in the Fennoscandian rivers appears to increase, the potential risk of parasites and other pathogens spreading between fish species will also rise. [ABSTRACT FROM AUTHOR]

In this study, the Peroxiredoxin-5 (PRDX5) gene from starry flounder (Platichthys stellatus , PsPRDX5) was identified through next-generation sequencing (NGS) and verified via cloning and sequencing. The predicted amino acid sequence, derived from the cDNA, was confirmed by multiple sequence alignment and phylogenetic analysis, establishing its homology with related sequences. PsPRDX5 mRNA was expressed across all examined tissues in healthy starry flounder, with distinct tissue-specific expression profiles. Following artificial infection with viral hemorrhagic septicemia virus (VHSV) and Streptococcus parauberis PH0710, significant alterations in PsPRDX5 mRNA expression were observed. VHSV infection resulted in a pronounced downregulation of PsPRDX5 in most major tissues, except for a significant upregulation in the intestine at 7 days post-infection. Conversely, infection with S. parauberis PH0710 led to a significant upregulation of PsPRDX5 in nearly all tissues. These results suggest that the differential expression of PsPRDX5 in response to VHSV and S. parauberis PH0710 reflects pathogen-specific immune and antioxidant defense mechanisms, highlighting the role of PsPRDX5 in the immune response of starry flounder to both viral and bacterial infections. • PRDX5 was identified from starry flounder and its expression was detected in all tissues examined. • Tissue- and gene-specific expression levels of PRDX5 mRNA were confirmed in healthy starry flounder. • PsPRDX5 mRNA expression was significantly regulated by S. parauberis PH0710 and VHSV infections. [ABSTRACT FROM AUTHOR]

Membrane-associated Ring-CH 5 (MARCH5) is a mitochondrial E3 ubiquitin ligase playing a key role in the regulation of mitochondrial dynamics. In mammals, MARCH5 negatively regulates mitochondrial antiviral signaling (MAVS) protein aggregation during viral infection and hampers downstream type I interferon signaling to prevent excessive immune activation. However, its precise functional role in the teleost immune system remains unclear. This study investigated the molecular characteristics and immune response of the MARCH5 ortholog in Amphiprion clarkii (A. clarkii ; AcMARCH5). The predicted AcMARCH5 protein sequence consists of 287 amino acids with a molecular weight of 32.02 kDa and a theoretical isoelectric point of 9.11. It contains four C-terminal transmembrane (TM) domains and an N-terminal RING cysteine-histidine (CH) domain, which directly regulates ubiquitin transfer. Multiple sequence alignment revealed a high level of conservation between AcMARCH5 and its orthologs in other vertebrate species. Under normal physiological conditions, AcMARCH5 showed the highest mRNA expression in the muscle, brain, and kidney tissues of A. clarkii. Upon stimulation with polyinosinic:polycytidylic acid (Poly I:C), lipopolysaccharide (LPS), and Vibrio harveyi , AcMARCH5 expression was drastically modulated. Functional assays showed that overexpression of AcMARCH5 in fathead minnow (FHM) cells downregulated antiviral gene expression, accompanied by enhanced viral hemorrhagic septicemia virus (VHSV) replication. In murine macrophages, AcMARCH5 overexpression markedly reduced the production of pro-inflammatory cytokines in response to poly I:C treatment. Additionally, AcMARCH5 exhibited an anti-apoptotic effect in H 2 O 2 -treated FHM cells. Collectively, these results suggest that AcMARCH5 may play a role in maintaining cellular homeostasis under disease and stress conditions in A. clarkii. • The membrane-associated Ring-CH5 (MARCH5) from Amphiprion clarkii (AcMARCH5) was identified and characterized. • Temporal expression of AcMARCH5 in blood, spleen and head kidney is drastically modulated by various immune stimuli. • AcMARCH5 overexpression suppressed antiviral gene expression and promoted VHSV viral replication. • AcMARCH5 overexpression reduced pro-inflammatory cytokine production in Poly I:C stimulated macrophages. • AcMARCH5 showed an anti-apoptotic property during H 2 O 2 induced oxidative stress. [ABSTRACT FROM AUTHOR]