A 56-day feeding trial to evaluate the responses of red seabream (initial weight: 1.8 ± 0.02 g) to the substitution of fish oil (FO) with camelina oil (CO) at different ratios was conducted. The control diet formulated at 46% CP (6F0C) contained only FO without CO; from the second to the fifth diet, the FO was substituted with CO at rates of 5:1 (5F1C), 4:2 (4F2C), 3:3 (3F3C), 2:4 (2F4C), and 0:6 (0F6C). The results of the present study showed that up to full substitution of FO with CO showed no significant effect on growth variables BW = 26.2 g–28.3 g), body weight gain (BWG = 1275.5–1365.3%), specific growth rate (SGR = 4.6–4.7), feed intake (FI = 25.6–27.8), feed conversion ratio (FCR = 1.0–1.1), biometric indices condition factor (CF = 2.2–2.4), hepatosomatic index (HSI = 0.9–1.1), viscerasomatic index (VSI = 7.5–9.5), and survival rates (SR = 82.2–100) with different FO substitution levels with CO. Similarly, there were no significant differences (p < 0.05) found in the whole-body composition except for the crude lipid content, and the highest value was observed in the control group (291 g/kg) compared to the other groups FO5CO1 (232 k/kg), FO4CO2 (212 g/kg), FO2CO4 (232 g/kg) and FO0CO6 (244 g/kg). Blood chemistry levels were not influenced in response to test diets: hematocrit (36–33%), glucose (Glu = 78.3–71.3 mg/dL), total protein (T-pro = 3.1–3.8 g/dL), total cholesterol (T-Chol = 196.0–241 mg/dL), blood urea nitrogen (BUN = 9.0–14.6 mg/dL), total bilirubin (T-Bil = 0.4–0.5 mg/dL), triglyceride (TG = 393.3–497.6 mg/dL), alanine aminotransferase test (ALT = 50–65.5 UL/L), aspartate aminotransferase test (AST = 38–69.3 UL/L). A remarkable modulation was observed in catalase (CAT) and superoxide dismutase (SOD) activities in the liver, as CAT and SOD values were lower with the complete FO substitution with CO (0F6C), and the highest values were observed in the control and (4F2C). This study indicates that red seabream may have the ability to maintain LC-PUFAs between tissues and diets, and CO substitution of FO could improve both lipid metabolism and oxidation resistance as well as maintain digestibility. In conclusion, dietary FO can be replaced up to 100% or 95% by CO in the diets of red seabream as long as n-3 HUFA, EPA, and DHA are incorporated at the recommended level.

The intestine is an important immune organ of aquatic animals and it plays an essential role in maintaining body health and anti-oxidative stress. To investigate the toxic effects of deltamethrin in intestinal tissue of Chinese mitten crabs (Eriocheir sinensis), 120 healthy crabs were randomly divided into two experimental groups (blank control group and deltamethrin-treated group), with three replicates in each group. After being treated with deltamethrin for 24 h, 48 h, 72 h, and 96 h, intestinal tissues were collected aseptically to assess the effects of deltamethrin on oxidative stress, immunity, apoptosis-related genes, and the structure of microflora in intestinal tissues. Additionally, correlations between gut microbiota composition and intestinal tissue damage-associated genes were analyzed. The results demonstrated that prolonged exposure to deltamethrin induced oxidative stress damage in intestinal tissue. Compared with the blank control group, the expression of autophagy-related genes B-cell lymphoma/Leukemia-2 (bcl-2), c-Jun N-terminal kinase (jnk), Microtuble-associated protein light chain 3 (lc3c), Cysteine-dependent Aspartate-specific Protease 8 (caspase 8), BECN1(beclin1), oxidative stress damage-related genes MAS1 proto-oncogene (mas), Glutathione Peroxidase (gpx), kelch-like ECH-associated protein 1 (keap1), Sequestosome 1 (p62), Interleukin-6 (il-6), and immune-related genes Lipopolysaccharide-induced TNF-alpha Factor (litaf), Heat shock protein 90 (hsp90) and prophenoloxidase (propo) in the deltamethrin treatment group were significantly up-regulated at 96 h (p < 0.05 or p < 0.01). Additionally, 16S rRNA sequencing showed that the diversity of intestinal flora in the deltamethrin-treated group was significantly higher compared with the blank control group (p < 0.01). Analysis of the differences in the composition of intestinal flora at the genus level showed that the relative abundance of Candidatus Bacilloplasma in the deltamethrin treatment group was significantly lower than that in the blank control group (p < 0.01). In contrast, the relative abundances of Flavobacterium, Lachnospiraceae_NK4A136_group, Acinetobacter, Chryseobacterium, Lacihabitans, Taibaiella, Hydrogenophaga, Acidovorax, and Undibacterium were significantly higher than those in the blank control group (p < 0.05 or p < 0.01). Pearson correlation analysis revealed that Malaciobacter, Shewanella, and Prevotella exhibited significant positive correlations with gene indicators (jnk, gpx, lc3c, litaf, hsp90), while Dysgonomonas, Vibrio, and Flavobacterium demonstrated significant negative correlations with multiple gene indicators (caspase 8, p62, il-16, keap1, jnk, etc). These results demonstrate that deltamethrin significantly impacts the gut microbiota, immune function, and antioxidant capacity of E. sinensis. The changes in gut microbiota have correlations with the biomarkers of intestinal tissue injury genes, indicating that gut microbiota plays a crucial role in deltamethrin-induced intestinal tissue damage. These insights contribute to a better understanding of the ecological risks associated with deltamethrin exposure in aquatic organisms.