Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are key long-chain omega-3 fatty acids in fish nutrition, but their differential effects on Atlantic salmon under unpredictable chronic stress (UCS) remain unclear. This study compared hepatic responses to DHA- and EPA-rich diets under unstressed and UCS conditions. Atlantic salmon post-smolts were fed a low-EPA+DHA, DHA-rich, or EPA-rich diet for 10 weeks, followed by 3 weeks of UCS. Liver transcriptomes were analyzed by RNA sequencing, and selected genes were validated by quantitative reverse transcription PCR. Growth did not differ among dietary groups. Under unstressed conditions, the DHA-rich diet induced more differentially expressed genes than the EPA-rich diet (67 vs. 29) and affected pathways related to fatty acid metabolism, autophagy, cholesterol homeostasis, and antioxidant defense. After UCS, the EPA-rich diet induced a broader hepatic transcriptional response than the DHA-rich diet (205 vs. 57 differentially expressed genes), with only 12 genes shared between the two comparisons. Both diets affected fatty acid- and steroid-biosynthesis-related pathways, while gene-level responses were diet-specific. These findings reveal distinct, stress-dependent hepatic responses to dietary DHA and EPA and may inform future optimization of their nutritional provision in Atlantic salmon production.

Tussah immunoreactive pupa powder (IPP) is composed of various active substances. We speculated that it has the potential to improve key economic traits of sea urchins. Therefore, we conducted a 60-day experiment to examine the effects of IPP on growth, antioxidant capacity, gonad quality, and gut microbiota of sea urchins (Strongylocentrotus intermedius). The experiment involved the preparation of a kelp group and four types of feed containing 0% (the control group), 0.5%, 1.0%, and 1.5% IPP. The results indicated that IPP had no significant impact on the survival of sea urchins (p > 0.05). Firstly, adding IPP promoted the growth of sea urchins. The 1.0% IPP group showed the highest weight gain rate among the feed group, significantly higher than that of the control group (p < 0.05). Secondly, compared with the kelp group, the addition of IPP significantly improved the growth and quality of sea urchin gonads (p < 0.05), which demonstrated certain industrial value. Thirdly, following the addition of IPP, the activities of SOD, CAT, and POD significantly increased in comparison to the control group (p < 0.05). Lastly, added IPP increased the abundance of Firmicutes, Bacteroidetes, and Rhodobacteraceae, while reducing the abundance of Ralstonia and Vibrio. This indicates that added IPP may improve the digestive function and gut health of sea urchins. Overall, added IPP can improve certain economic traits and antioxidant capacity of sea urchins. This manuscript provides a theoretical reference for the healthful aquaculture of S. intermedius.

No. 0 diesel oil may pose a serious threat to sea cucumber (Apostichopus japonicus) aquaculture by inducing skin ulceration. This study aimed to evaluate the protective efficacy and mechanism of a previously developed inhibitor composition against diesel-induced injury. The inhibitor composition significantly alleviated skin ulceration in the experimental group (Eg), reducing the lesion area to 14.44 ± 1.79% after 96 h, compared to 33.19 ± 2.94% in the diesel-exposed control group (Cg) (p < 0.05). It effectively suppressed the overactivation of autolytic enzymes (cathepsin L and B) while enhancing the activities of acetylcholinesterase, superoxide dismutase, and catalase. Transcriptomic profiling revealed 3137 differentially expressed genes, with functional enrichment in pathways related to Notch signaling, ECM–receptor interaction, glycosaminoglycan biosynthesis, and detoxification. The upregulation of genes such as HES-C, CYP1A1, GST, and UGT may be linked to the regulation of apoptosis inhibition, xenobiotic metabolism, and antioxidant defense. Furthermore, enhanced expression of NAD kinase and PNLIPRP may indicate a potential strengthening of energy metabolism and lipid utilization during stress adaptation. This study suggests that the inhibitor composition may exert a multi-level protective effect against diesel-induced injury by coordinating tissue repair, oxidative balance, and detoxification processes, offering a potential strategy to mitigate pollution impacts in sea cucumber aquaculture.