We investigated the effects of thermal stress on the mucosal structure and the immune response in the intestine of the whiteleg shrimp Litopenaeus vannamei (Boone, 1931). Examination of histological sections showed that thermal stress damaged the epithelium of the intestinal mucosa. The experimental shrimp were acclimated for one week before thermal stress. In response to thermal stress, there was an increase in the oxidative stress parameters, including the activity of ·O₂^- -generation capacity and the contents of lipid peroxidation and malondialdehyde, while antioxidant activities (superoxide dismutase, catalase, and glutathione peroxidase) and the expressions of the heat shock protein 70 and thioredoxin genes showed significant variations (P < 0.05). Immune activities (acid phosphatase and alkaline phosphatase) were decreased after 24–72 h of thermal stress, and the metabolic activity of lactate dehydrogenase and the expression of the hypoxia-inducible factor 1α gene were higher than those of the control group. These results revealed that thermal stress impaired the intestinal barrier of the shrimp by damaging the mucosal structure, inducing oxidative stress, and compromising the immune and metabolic status.

The present study was conducted to investigate the effects of dietary fermented cottonseed meal (FCSM) substitution for fish meal on intestinal enzymatic activity, inflammatory and physical-barrier-related gene expression, and intestinal microflora of juvenile golden pompano. The 375 golden pompanos were divided into 15 groups of 25 fish each, with three replicates for each experimental group. The fish were fed five experimental diets (0 (FM), 12.5% (CSM12.5), 25% (CSM25), 50% (CSM50), and 100% (CSM100) substitution levels) for 8 weeks. The fish were reared and fed the experimental diets under a natural-day light cycle. Compared with the control group, the activities of AMY (amylase) enzymes in the CSM12.5 group and all other groups were elevated (p < 0.05). The CSM25 group exhibited a considerable up-regulation of IL-10 (Interleukin-10) expression relative to the FM group (p < 0.05). With an increase in dietary FM substitution with FCSM from 0 to 25%, the relative expressions of NF-κB (Nuclear factor kappa-B), IL-1β (Interleukin-1 beta), and IL-8 (Interleukin-8) were down-regulated. In this study, the relative expressions of ZO-1 (zonula occluden-1) and Occludin were up-regulated, and those of Claudin-3 and Claudin-15 significantly up-regulated, when the FCSM substitution ratio was 25%. The results of high-throughput sequencing of the intestinal microflora showed that ACE indices the lowest in the CSM25 group, which was significantly different from those in the CSM100 group (p < 0.05). The CSM50 group had the highest Shannon and Simpson indices and the highest community diversity. In addition, replacing a high percentage of fish meal with FCSM can negatively affect the intestinal flora of fish. In this study, the 25% substitution ratio improved nutrient absorption, reduced intestinal inflammation, improved intestinal physical barrier damage, did not affect intestinal microecology, and had no adverse effects on fish. However, substitution of a high proportion of FM with FCSM negatively affects the intestinal microflora and nutrient absorption capacity of fish.

The nutrient, amino acid, and fatty acid compositions of Caulerpa lentillifera from various aquaculture regions were assessed to analyze their nutritional characteristics and potential for aquaculture development. The nutrient composition of C. lentillifera was determined according to the standard national nutrient determination methods of the Association of Official Analytical Chemists, and the following data were revealed. (1) The basic nutritional components of C. lentillifera were relatively more abundant in the three aquaculture areas in Guangdong Province. The crude protein content in C. lentillifera was measured at (8.70 ± 0.36)% and (18.57 ± 1.59)% for samples collected from the Dapeng and Daya areas, respectively. These values were significantly higher compared to those obtained from the Beihai, Dongshan, and Nha Trang regions (p < 0.05). Additionally, the crude lipid content of C. lentillifera from the Daya population was measured at (5.10 ± 1.59)%, which was significantly higher than that of samples from the Beihai, Dongshan, and Nha Trang areas (p < 0.05). Furthermore, the total sugar contents in C. lentillifera were quantified as (32.50 ± 4.22)% and (32.87 ± 2.59)% for samples from the Daya and Shanwei regions, respectively. These values were significantly greater (p < 0.05) compared to those observed in the other four populations. (2) The total amino acid (TAA) content of C. lentillifera ranged from 7.05% to 12.37%, with notable concentrations of the fresh amino acids aspartic acid (Asp) and glutamic acid (Glu). Significant variations in the TAA and essential amino acid (EAA) levels were observed among the cultivation regions (p < 0.05), with the Shanwei population exhibiting the highest TAA content of 12.37% and EAA content of 4.65%, surpassing all other populations except for Guangdong Province (p < 0.05). (3) The fatty acid composition analysis revealed that the total fatty acid (TFA) and unsaturated fatty acid (UFA) levels in the long-stemmed grape fern alga from Daya were 2.400% and 1.048%, respectively, and significantly greater than those in the other populations except for Dapeng (p < 0.05). These results imply that the nutritional quality of the Daya population of C. lentillifera is relatively high. C. lentillifera exhibits a palatable flavor profile, making it suitable for consumption and the development into high-quality seafood condiments, thereby contributing to the environmentally sustainable advancement of C. lentillifera aquaculture.