Conventional immediate and high-temperature immediate acid treatment are crucial techniques for breaking the diapause state of silkworm eggs, but their molecular mechanisms remain unclear. This study prepared diapause eggs (CK), conventional immediate acid-treated eggs (46 °C, 5 min, and CG), and high-temperature immediate acid-treated eggs (47.5 °C, 7 min, and GW) and analyzed the transcriptome and metabolome to screen for key expressed genes and key metabolites. Transcriptome results showed that 688, 823, and 222 differentially expressed genes (DEGs) were obtained from CK vs. CG, CK vs. GW, and CG vs. GW, respectively, and 12 DEGs significantly upregulated in all three comparisons (CK vs. CG, CK vs. GW, and CG vs. GW), including glycine-N-methyltransferase, choline dehydrogenase, Hsp68, and Hsp70. The LC-MS analysis results showed that 854, 711, and 506 differential metabolites (DMs) were obtained from CK vs. CG, CK vs. GW, and CG vs. GW, respectively. A total of seven DMs upregulated in all three comparisons and with |log₂Fold Change| ≥ 0.5 in CG vs. GW, including tyrosine-isoleucine-histidine, phenylalanyl-tyrosine, tyrosine-phenylalanine-glutamate-lysine, and histidylleucine, as well as 12 downregulated DMs, were identified. Additionally, it was found that γ-linolenic acid and triglycerides were upregulated in CG vs. GW. The conjoint analysis results revealed that four small peptides, including tyrosine-isoleucine-histidine, phenylalanyl-tyrosine, tyrosine-phenylalanine-glutamate-lysine, and histidylleucine, exhibited a highly significant positive correlation with Hsp70 family genes such as Hsp68 and Hsp70. This suggests that these small peptides, along with γ-linolenic acid and triglycerides, may play a crucial role in the resistance of silkworm eggs to high-temperature stress and the associated oxidative stress.

Intestinal health is critical for nutrient absorption and disease resistance in cultured fish. Yet, the effects of dietary Eucalyptus-derived biochar on the gut of largemouth bass (Micropterus salmoides) remain largely unexplored. This study evaluated whether supplementing diets with Eucalyptus biochar c profiles. In a 56-day feeding trial, M. salmoides were offered a standard diet containing either 0% (control) or graded levels of biochar. Juvenile fish (initial body weight 13.34 g) were randomly distributed into six groups with three replicates each (30 fish per replicate). Six extruded diets were formulated with 0, 2.5, 5.0, 10.0, 20.0, or 40.0 g kg⁻¹ of biochar, designated G0 through G5. Biochar had no significant effects on villus length, muscle layer thickness, villus width, or the activities of trypsin, amylase, and lipase, though goblet cell number was significantly higher in G5. mRNA expression of Claudin-3 and IL-10 was significantly upregulated in G1–G4, while IL-1β was significantly downregulated in G4 and G5, and TNF-α expression was reduced in G2 and G3. 16S rDNA sequencing showed increasing trends in the relative abundance of Firmicutes (43% to 49.17%) and Lactococcus (0% to 1.10%) in G3, accompanied by decreases in Proteobacteria and Klebsiella. Metabolomic analysis indicated significant upregulation of taurochenodeoxycholic acid-7-sulfate, apigenin, genistein, baicalein, taurocholic acid-3-sulfate, taurochenodeoxycholic acid-3-sulfate, and arginylmethionine in G3, whereas etoxazole and soyasaponin were significantly reduced. Dietary inclusion of 10 g kg⁻¹ Eucalyptus biochar improved intestinal health in largemouth bass by shaping the gut microbiota, promoting isoflavone biosynthesis and bile acid and amino acid metabolism, inhibiting the NF-κB pathway, and reinforcing the intestinal barrier.

The intestine, particularly the gut microbiota, and the liver play key roles in digestion, nutrient transformation, and immune regulation in fish. However, limited information is available regarding how different ornamental fish species regulate these systems under identical aquaculture conditions. Therefore, this study systematically compared gut microbiota diversity, structural variation, and predicted ecological functions among eight ornamental fish species reared in the same environment, using 16S rRNA high-throughput sequencing combined with digestive enzyme indices and histological analysis of intestinal and liver tissues. The results showed that goldfish (Carassius auratus) and crucian carp exhibited efficient digestive and absorptive capacities, supported by a thickened muscularis and prominent mucosal layers (p < 0.001). High goblet cell density was observed in red swordtail (Xiphophorus hellerii) and Mickey Mouse platy (Xiphophorus hellerii × X. maculatus) (p < 0.001). Larger hepatocyte perimeter and area were observed in red swordtail (p = 0.022, p = 0.015), whereas platinum mini parrot cichlid and sapphire mini parrot cichlid showed significant hepatocyte vacuolization. Microbial analysis showed that the eight fish species had similar α diversity indices, while the gut microbial profiles of Mickey Mouse platy and golden crucian carp differed the most. At the genus level, beneficial taxa such as Lactococcus, Paracoccus, and Cetobacterium were significantly enriched in red swordtail, sailfin molly, and goldfish, respectively, whereas opportunistic pathogens, including Edwardsiella, Aeromonas, and Acinetobacter, were enriched in Mickey Mouse platy, sapphire mini parrot cichlid, and golden crucian carp, respectively (p < 0.05). Functional prediction based on KEGG pathways indicated that sailfin molly and Mickey Mouse platy exhibited the broadest functional enrichment, primarily involving amino acid metabolism, fatty acid metabolism, and antibiotic biosynthesis. Crucian carp and golden crucian carp showed higher activity in amino acid biosynthesis and glycolysis/gluconeogenesis pathways. The two parrot cichlid species were characterized by enrichment in biofilm formation pathways of pathogenic bacteria and amino sugar and nucleotide sugar metabolism pathways. Goldfish and red swordtail were mainly associated with quorum sensing and ABC transporter pathways. These results provide a theoretical foundation for optimizing aquaculture conditions for ornamental fish and improving fish health and production efficiency.