In an era of striking climate change, increased marine temperature severely affects aquatic animals and cause significant ecological and socioeconomic impacts. At present, there is little information about the effects of heat stress on the physiology of greater amberjack (Seriola dumerili). This study explores the mechanisms whereby juvenile greater amberjacks cope with heat stress. An increase in water temperature (25 to 28°C and 31°C) changed the activity levels of enzymes responsible for antioxidant defense, immune function, and energy metabolism. When water temperatures increased from 25 to 28°C and 31°C, the levels of malondialdehyde (MDA) and glucose (GLU) in the greater amberjacks increased, suggesting that the fish suffered oxidative stress. During the early stage of heat stress, the levels of triglycerides (TG) and glutathione (GSH) and the activities of superoxide dismutase (SOD), catalase (CAT), alkaline phosphatase (ALP), acid phosphatase (ACP), lysozyme (LYZ), alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and succinate dehydrogenase (SDH) increased significantly suggesting that juvenile greater amberjacks adapt to heat stress by enhancing their antioxidant defense, energy metabolism, and immune defense. However, long‐term exposure to heat stress decreased the levels of TG and GSH; decreased the activities of SOD, CAT, ALP, ACP, LYZ, and AST; and increased the levels of MDA and GLU, suggesting that the energy metabolism and immune function of juvenile greater amberjack S. dumerilis are suppressed by oxidative damage. This study provides insights into the physiological adaptation of juvenile greater amberjacks to heat stress.

Despite the significance of n-3 long-chain polyunsaturated fatty acid (n-3 LC-PUFA) in fish oil in promoting the maturation of female broodstocks, the detailed mechanism of the effect on the expression of hepatic reproduction-related genes is still unclear. In this study, transcriptome sequencing was used to analyze the effect of the higher dietary n-3 LC-PUFA level on gene expression in the liver of adult females spotted scat. Two-year-old female spotted scat (average weight, 242.83 ± 50.90 g) were fed with diets containing 8% fish oil (FO) or 8% soybean oil (SO) for 40 days. The fatty acid profile in the serum, liver, and ovary was analyzed, and high proportions of n-3 LC-PUFA were observed in the FO group. The final average fish body weight and gonadosomatic index were similar between the FO and SO groups. The serum vitellogenin (Vtg) and hepatosomatic index (HSI) of the FO group were significantly higher and lower than that of the SO group, respectively. Comparatively, the liver transcriptome analysis showed 497 upregulated and 267 downregulated genes in the FO group. Among them, the expression levels of three estrogen-regulated genes (i.e., Vtga, Vtgb, and Zp4) were significantly higher in the FO than in the SO group. This expression pattern could be related to the upregulation of Hsd17b7 (the key gene for the synthesis of liver steroid hormone) and the downregulation of the Hsp90 (the estrogen receptor chaperone). The expression levels of Foxo1a and Lep, which are involved in the lipid metabolism, decreased significantly in the FO group, which may be related to the lower level of HSI in the FO group. The genes related to liver LC-PUFA absorption and transport, Fabp2 and Mfsd2ab, were significantly upregulated in the FO group, indicating that fish actively adapt to high-fish-oil diets. In brief, high-fish-oil diets can influence the expression of genes related to liver n-3 LC-PUFA metabolism and reproduction, inhibit the accumulation of liver fat, and promote the liver health and gonad development. This study will contribute to clarifying the mechanism of dietary n-3 LC-PUFA on promoting reproductive development in teleost fish.

Long non-coding RNAs (lncRNAs) play a multifaceted role in transcriptional regulation, and the potential molecular regulatory mechanisms of lncRNAs and lncRNA–miRNA–mRNA networks in body color formation are of great significance for its selective breeding. Therefore, lncRNAs and lncRNA-miRNA-mRNA ceRNA network of red- and black-colored Plectropomus leopardus were identified and analyzed. Sequencing analyses identified 167 differentially expressed lncRNAs (DELs) between red- and black-colored P. leopardus, including 89 upregulated and 78 downregulated DELs in the red-colored group (false discovery rate (FDR) < 0.05 and |log₂FC| > 1). Differentially expressed miRNA (DEM), genes (DEG), and DEL analyses found 605 and 125 negatively co-expressed miRNA–mRNA pairs and lncRNA–miRNA pairs, respectively. Further correlation analysis with Spearman’s correlation coefficient >0.9 as the threshold identified 3,721 lncRNA–mRNA pairs. Then, a competitive endogenous RNA (ceRNA) network of 325 pairs (p < 0.05) was obtained. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment of network DEGs showed that melanin metabolic process, lipid metabolism, and immune-related pathway were enriched. The ceRNA network provided interactions among lncRNAs, miRNAs, and mRNAs and extended the molecular foundation of body color formation.