The complete mitochondrial genome sequence of Chinese native Dolly Varden (Salvelinus malma sp.) was sequenced. It was 16,652-nucleotide in length and consisted of 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, and 2 non-coding regions (L-strand replication origin and control region), showing conserved gene arrangement with most vertebrates. The phylogenetic analysis based on Cytb genes of Chinese native as well as four other Dolly Varden subspecies showed that Chinese native S. malma sp. had close relationships with S. curilus (formerly named as S. malma krascheninnikova) and S. malma miyabe. This result did not support the monophyletic relationship of Dolly Varden chars. Further studies are needed to determine the phylogenetic position of Chinese native Dolly Varden.

The greenfin horse-faced filefish (Thamnaconus septentrionalis) is susceptible to recurrent Amyloodinium ocellatum (AO) infestation over the grow-out production cycle. This parasite breeds mainly on the gills, causing hypoxia in the fish body, and leading to many deaths. The host-parasite response drives a complex immune reaction, which is poorly understood. To generate a model for host-parasite interaction and the pathogenesis of AO in greenfin horse-faced filefish, an RNA-seq approach, differential gene expression, GO, and KEGG analyses were employed. Overall, 624 new genes and 2076 differentially expressed genes (DEGs) were detected, including 942 upregulated and 1134 downregulated genes in the gills. Compared with the control group, the expression of leptin a, GTPase IMAP family member 4, and NLR family CARD domain-containing protein 3 was significantly higher in the AO-infected group. Conversely, cell wall integrity and stress response component 1-like, and hepcidin-like were significantly downregulated in the gills of AO-infected fish. GO and KEGG enrichment analysis indicated that DEGs were significantly enriched in signaling pathways associated with viral protein interaction with cytokine and cytokine receptor and cytokine–cytokine receptor interaction. Collectively, this transcriptomic study provides novel molecular insights into the pathology caused by AO infestation and alternative theories for future research implementing strategies to control and manage AO.

The study aimed to uncover the molecular response of juvenile Sebastes schlegelii to air exposure stress by identifying differentially expressed genes (DEGs) that may underlie their anti-stress mechanisms. Juvenile Sebastes schlegelii were subjected to varying durations of air exposure stress. The total RNA was extracted from whole tissues and sequenced using the Illumina NovaSeq 6000 platform. The transcriptome data were analyzed to identify DEGs through pairwise comparisons across a control group and two experimental groups exposed to air for 40 s and 2 min 30 s, respectively. The comparative DEG analysis revealed a significant number of transcripts responding to air exposure stress. Specifically, 5173 DEGs were identified in the 40 s exposure group (BS) compared to the control (BC), 6742 DEGs in the 2 min 30 s exposure group (BD) compared to the control (BC), and 2653 DEGs when comparing the BD to the BS group. Notably, Gene Ontology (GO) analysis showed an enrichment of DEGs associated with peptidase activity and extracellular regions, suggesting a role in the organism’s stress response. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis pointed to the involvement of metabolic pathways, which are crucial for energy management under stress. The upregulation of protein digestion and absorption pathways may indicate a physiological adaptation to nutrient scarcity during stress. Additionally, the identification of antibiotic biosynthesis pathways implies a potential role in combating stress-induced infections or damage. The identified DEGs and enriched pathways provide insights into the complex anti-stress response mechanisms in juvenile Sebastes schlegelii. The enrichment of peptidase activity and extracellular region-related genes may reflect the initiation of tissue repair and immune response following air exposure. The connection between protein digestion and absorption pathways and anti-stress capabilities could be interpreted as a metabolic readjustment to prioritize energy-efficient processes and nutrient assimilation during stress. The role of antibiotic biosynthesis pathways suggests a defensive mechanism against oxidative stress or microbial invasion that might occur with air exposure.