Acute salinity stress critically impacts aquaculture efficiency by inducing physiological disruptions in fish. This study investigated the molecular adaptation mechanisms of Pseudobagrus ussuriensis exposed to 10 ppt NaCl for 96 h, integrating transcriptomic and metabolomic analyses of gill and kidney tissues. In transcriptomics, 2,554 and 1,066 differentially expressed genes (DEGs) were identified in gills and kidneys, respectively, with significant enrichment in pathways related to energy metabolism (glycolysis, oxidative phosphorylation), membrane dynamics (glycerophospholipid metabolism), and immune-osmoregulatory crosstalk (HIF-1, TNF, and Jak-STAT signaling). Metabolomics revealed 85 and 433 differential metabolites (DMs) in gills and kidneys, highlighting tyrosine metabolism, amino acid biosynthesis/degradation, and lipid remodeling (e.g., glycerophospholipids, sphingolipids). Multi-organ coordination was observed: gills prioritized short-term osmotic adaptation via membrane lipid reorganization but suffered oxidative damage due to sustained downregulation of ALDH7 A1 and AOX/HADHA , triggering a “membrane injury–oxidative stress-ATP depletion” cycle. Conversely, kidneys-maintained energy homeostasis through purine/pyrimidine-TCA cycle reprogramming and autophagy-apoptosis balance. Critically, interorgan metabolic crosstalk-mediated by lipid mediators (prostaglandins, sphingolipids) and amino acid derivatives (branched-chain keto acids, glutamine)—orchestrated substrate shuttling (e.g., lactate for energy exchange) and systemic signaling, bridging local stress responses (gill ion regulation) with global metabolic adjustments (renal energy buffering). Notably, the levels of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) in the kidney and phosphatidic acid (PA) and PC in the gills were significantly increased, while sphingomyelin (SM) decreased. Our findings demonstrate that acute salinity stress induces organ-specific metabolic reprogramming and interorgan crosstalk in P . ussuriensis , revealing a trade-off between osmotic adaptation and oxidative stress resilience mediated by lipid remodeling and energy metabolism dysregulation.

Fishes are frequently exposed to hypoxic stress, yet their tolerance to hypoxia varies significantly among species. The association between this variation and alterations in the hypoxia-inducible factor (HIF) pathway remains unclear. We discovered that otomorphs generally retain two Hif-1α paralogs (Hif-1αa and Hif-1αb), resulting from the teleost-specific genome duplication (TGD), whereas most euteleosts possess only a single Hif-1αa copy. In otomorphs, key mutations disrupt one conserved Leu-X-X-Leu-Ala-Pro (LXXLAP) motif in the oxygen-dependent degradation (ODD) domain of the Hif-1αa proteins. Molecular dynamics simulations revealed that these mutations impede the recognition of the critical proline residue by prolyl hydroxylase domain protein 2 (PHD2), suggesting enhanced normoxic stability of Hif-1αa. We also investigated the expression profiles of hif-1α and downstream genes in four fish species (two otomorphs and two euteleosts). In otomorphs, the hif-1αa genes were highly expressed specifically in the heart; concomitantly, two critical downstream genes, ldha and mct4, exhibited relatively high expression levels in vital tissues such as the heart, brain, and muscle. This coordinated expression pattern promotes a heightened glycolytic capacity and facilitates lactate shuttling in these tissues, thereby ensuring energy supply during hypoxic stress. Our integrated computational analyses indicate that otomorphs achieve enhanced hypoxia tolerance through the subfunctionalization of Hif-1α paralogs.

Pseudobagrus ussuriensis is an unscaled fish that is more susceptible to skin damage than scaled fish. To investigate the impacts of hypoxia and reoxygenation on skin and brain immunity, juvenile P. ussuriensis were subjected to hypoxia conditions (DO: 0.8 ± 0.05 mg/L) for durations of 0, 3, 6, and 12 h, followed by 12 h of reoxygenation (DO > 6 mg/L). Histological analysis showed a significant increase in the number of skin mucosal cells after 12 h of hypoxia and a significant decrease after 12 h of reoxygenation when compared to the control group. As the duration of hypoxia increased, an increase in antioxidant (SOD, CAT, GSH, MDA) and immune (cortisol, LZM) physiological parameters of the skin and brain appeared. The results of transcriptomic studies showed that the number of differential genes was greater in skin than in brain. Most of the immune pathways in both tissues under hypoxia conditions were all nonspecific immunity (TNF, IL-17, chemokines), while both tissues maintained their homeostasis through active energy supply and cell cycle regulation. Meanwhile, both physiological parameters and RNA transcriptome results showed that 12 h of reoxygenation could not completely eliminate the negative effects of 12 h of hypoxia. This study offers new insights into the immune responses of P. ussuriensis skin and brain during acute hypoxia and reoxygenation.

Scorpion venom plays an important role in scorpion predation, competition, communication, and defense. In this study, the species identification of Shandong scorpion and the analysis of venom extracted from male and female scorpion at the transcriptome level and their activity were compared. Whole de novo transcriptomes were performed on male and female scorpions and the sequences of cytochrome c oxidase subunit I were screened to identify the species. The scorpions collected were identified as Mesobuthus martensii and we have successfully annotated 16,726 (37.47%), 10,076 (22.57%), 10,878 (24.37%), and 10,187 (22.82%) unigenes with NR, Swissport, GO and KEGG database. A total of 17 kinds of toxins and 181 toxin-related unigenes were screened. There is no accurate identification of the differences between male and female scorpions at the molecular level and these need to be further explored. The difference ratio in toxins was 6.08%, and this number in unigenes was 0.78%. There are seventeen toxins and other toxins related genes were analyzed in male and female scorpions, among which the representative phospholipase, makatoxin toxin, and plancitoxin toxin were all related to the biological functions of scorpion martensii. EF chiral domain in phospholipase: helix turn helix is related to calcium channel toxin; The QWAKYGN base sequence contained in makatoxin toxin is α-toxin specific domain; It was found in plancitoxin I toxin that it contains two deoxyribonuclease II active sites, HEK, and DHSK. Since calcium channel toxins are associated with α- toxins belong to neurotoxins. Therefore, phospholipase and makatoxin are both toxins that act on the nervous system, while plancitoxin I toxin has deoxyribonucleotidase II activity and can degrade DNA in mammals. We constructed structure analysis including sequence alignment, 3D modeling, and phylogenetic analysis in phospholipase, makatoxin, and plancitoxin. There was little difference showed in GO and KEGG analysis and the differences ratio in unigenes annotated as toxins was much higher than that in all unigenes. What’s more, the evaluation of toxin activity showed that the toxicity of female scorpion was likely to be higher than that of male scorpion. The method can be used as a useful tool to evaluate the difference between male and female animals.