Three antioxidant properties (corresponding to the enzymes superoxide dismutase (SOD), catalase, and glutathione peroxidase) were measured in the livers of Scophthalmus maximus under different salinities/temperatures (5, 10, 20, 30, and 40‰/17, 20, 23, 25, and 28 °C). Split-plot (SP) analysis, additive main effects, and multiplicative interaction (AMMI) and genotype × environment interaction (GGE) biplots were used to analyze genotype × salinity/temperature interactions for antioxidant properties. The results of the SP analysis show that the activity of the three antioxidant properties was significantly (p < 0.01) affected by salinity/temperature, antioxidant, and salinity/temperature × antioxidant interaction. The results of the AMMI analysis for salinity reveal that the effect of genotype, salinity, and genotype × salinity interaction on antioxidant properties reached a significant level (p < 0.001); 92.1065%, 2.6256%, and 4.4360% of the total sum of squares for antioxidant property activity were attributable to the effects of genotype, salinity, and genotype × salinity interaction, respectively. The results of GGE biplot analysis for salinity reveal differences in the activity ranking of the three antioxidant properties under five salinities; this difference expands with an decrease or increase in salinity from 30‰ (optimum salinity). A salinity of 5‰ had the strongest ability to identify the three antioxidant properties. The five experimental salinities were divided into one region, and SOD activity was the highest in this region. In a comprehensive analysis of stability and activity, SOD had the best activity and stability. The results of AMMI analysis for temperature reveal that genotype, temperature, and genotype × temperature interaction had significant effects on the antioxidant properties (p < 0.001); 82.4720%, 4.0666%, and 12.0968% of the total sum of squares for antioxidant property activity were attributable to the effects of genotype, temperature, and genotype × temperature interaction, respectively. The results of GGE biplot analysis for temperature reveal a large difference in the activity ranking of antioxidant properties between 17 °C and the other four temperatures, while only small differences in the activity rankings were detected among the other four temperatures. The difference in the activity ranking of antioxidant properties was greatest between the temperatures of 17 and 20 °C. A temperature of 17 °C showed the strongest ability to distinguish the three antioxidant properties. Additionally, the five test temperatures were grouped into one region, and comprehensive analysis of activity and stability showed that SOD had the best activity and stability.

Genetic improvement, including improving the growth rate, survival rate and feed efficiency ratio (FER), can maximize the production efficiency of turbot. Genetic evaluations of the growth rate, survival rate and FER are required for determining the practicability of including these three traits in a breeding programme. In this study, 20 full-sib families were produced. A method involving a small sample was used to calculate the growth rate, survival rate and FER to represent the corresponding data of an individual. Then, the genetic parameters of the three economic traits were evaluated. The heritabilities for the survival rate, growth rate and FER in turbot were 0.109001, 0.232335 and 0.101866, respectively. The heritabilities of the survival rate and FER were low, while that of the growth rate was moderate. The phenotypic correlations between the survival rate and growth rate, the survival rate and FER, and the survival rate and FER were 0.0919, 0.4609 and 0.2472, respectively. The genetic correlations between the growth rate and survival rate, the survival rate and FER, and the growth rate and FER were 0.0984, 0.3732 and 0.5654, respectively. Apart from a low phenotypic and genetic correlation between the survival rate and growth rate, the correlations among the other traits were moderate.

To elucidate the physiological and molecular mechanisms underlying cold tolerance in the mangrove species Kandelia obovata Sheue & al, this study measured the antioxidant enzyme activities and photosynthetic pigment contents of two populations—cold-tolerant and -sensitive—under natural overwintering conditions. In addition, transcriptome sequencing was performed to analyze differentially expressed genes (DEGs), transcription factor families, single nucleotide polymorphisms (SNPs), and alternative splicing events. The results showed that catalase activity was significantly elevated in the cold-tolerant population, which enhanced the efficiency of hydrogen peroxide scavenging. In contrast, although the superoxide dismutase activity was relatively high in the cold-sensitive population, its downstream scavenging capacity was insufficient, resulting in an overall lower antioxidant efficiency. The KEGG enrichment analysis indicated that pathways such as phenylpropanoid biosynthesis, amino sugar metabolism, and plant hormone signal transduction might be involved in the response to low-temperature stress. Further analysis revealed that transcription factors such as WRKY, NAC, MYB, and ERF were differentially expressed at significant levels in the cold-tolerant population, suggesting that they may play important roles in low-temperature adaptation. In addition, the diversity of SNPs and alternative splicing events may enhance protein function and contribute to improved cold tolerance. In summary, the cold-tolerant K. obovata population achieves low-temperature tolerance through multiple mechanisms, including antioxidant defense, metabolic regulation, and transcriptional as well as post-transcriptional regulation. This study provides a theoretical basis for elucidating the molecular foundations of cold tolerance in K. obovata.

Mass mortality outbreaks threaten cultured big-belly seahorses (Hippocampus abdominalis), but gut microbial changes associated with disease and host sex remain unclear. We analyzed 36 seahorses from a single aquaculture system, classified as apparently normal males (NMHA), diseased males (EMHA), apparently normal females (NFMHA), and diseased females (EFMHA). Intestinal contents from three individuals were pooled per biological replicate, yielding three pooled replicates per group and 12 microbiome samples in total (effective n = 3 per group). The V3–V4 region of the 16S rRNA gene was sequenced, and ASVs were inferred using DADA2 in QIIME 2. α-diversity showed marginal overall group differences, whereas exploratory two-way ANOVA indicated effects of health status and Health × Sex interactions on observed ASVs, Shannon, and Simpson indices. Bray–Curtis PERMANOVA also detected significant effects of health status and the Health × Sex interaction on community structure. Pseudomonadota dominated all groups, while Vibrio was strongly enriched in diseased females, reaching 86.94 ± 13.03%. LEfSe identified Vibrio/Vibrionaceae as biomarkers of diseased females, whereas Arcobacteraceae and Litoreibacter characterized diseased males. PICRUSt2-based prediction suggested higher predicted representation of pathways related to signal transduction, membrane transport, biofilm formation, chemotaxis, and flagellar assembly in diseased groups. Overall, gut microbiota dysbiosis during the outbreak showed sex-stratified patterns, with pronounced Vibrio enrichment representing a prominent disease-associated microbial feature, particularly in females.