This study investigated the effects of dietary iron supplementation on water quality, plant growth, and fish health in an aquaponic system over 90 days. Iron supplementation significantly improved plant growth, with increased plant height, stem diameter, leaf count, and fruit yield in tomatoes (Solanum lycopersicum) and pak choi (Brassica rapa subsp. Chinensis) (p < 0.05). The water pH fluctuated with varying iron content, and higher iron levels promoted better plant growth by improving iron availability (p < 0.05). During the first 60 days, all red blood cell counts and hemoglobin levels increased, but the growth and nutritional composition of mirror carp (Cyprinus carpio var. specularis) showed no significant differences. By day 90, fish in the T3 group (800 mg/kg iron) exhibited significantly reduced growth and feed conversion rates (p < 0.05). Histological analysis of liver tissue indicated iron-induced liver damage; additionally, excessive iron intake suppressed erythropoiesis, leading to lower red blood cell counts and hemoglobin levels (p < 0.05). The results indicate that moderate iron supplementation improves plant growth, but excessive iron can negatively impact fish health, particularly liver function and blood formation. These findings provide valuable insights for optimizing iron levels in aquaponic systems.

Poly (I:C), a viral mimic, is capable of activating the antiviral immune mechanisms in teleosts. In this study, we investigated the transcriptional responses of Ussuri Catfish (Pseudobagrus ussuriensis) to poly (I:C) stimulation at 3 and 48 h, focusing on the similarities and differences in antiviral mechanisms exhibited in the liver and spleen. At 3 h, the signaling pathways that were concurrently enriched in both the spleen and liver include JAK-STAT, TNF, NF-κB, RIG-I-like receptor, and NOD-like receptor. At 48 h, the signaling pathways that were concurrently enriched in both the spleen and liver include JAK-STAT signaling and cellular homeostasis processes. However, in the liver, the signaling pathways that responded to poly (I:C) stimulation at both 3 and 48 h are cytokine–cytokine receptor interaction and RIG-I-like receptor signaling. In the spleen, the signaling pathways that responded to poly (I:C) stimulation at both 3 and 48 h are Hippo signaling, Wnt signaling, TGF-β signaling, and ECM-receptor interaction. Ultimately, the pathways that were enriched in the intersection genes across all groups are JAK-STAT signaling, NK cell-mediated cytotoxicity, and ECM-receptor interaction, and the core genes identified in the intersection genes of all groups are PTPRS, HECW1, and ERN1 (IRE1), along with UMAD, DKK1, CSH, and RTKN2. Through this study, we identified the key signaling pathways and core genes involved in the antiviral response of Ussuri catfish. These findings provide valuable insights into the antiviral mechanisms of Ussuri catfish.