Climate-induced changes in water temperature, particularly diurnal thermal fluctuations, pose serious challenges to aquatic organisms, especially fish. The present study investigated the gill transcriptomic responses of the catfish Clarias magur subjected to diurnal heat stress. Fish maintained at ambient temperature (26 °C) served as the control group, whereas the treatment group was exposed to cyclic diurnal temperature fluctuation (DTF) over a 24-h period (26→28→30→32→34→32→30→28→26 °C), with 3 h at each temperature for 4 days. Gill RNA from control and DTF-exposed fish were analysed by high-throughput sequencing and differentially expressed genes (DEGs) were identified using log2 fold change criteria and adjusted p-values. Comparative transcriptome analysis revealed a clear separation between control and treatment groups, indicating extensive transcriptional modulation under diurnal heat stress conditions. Differential expression analysis identified 90,574 significantly regulated transcripts, including 6,629 upregulated and 83,945 downregulated transcripts, indicating a predominance of transcriptional suppression in heat-stressed fish. Pathway enrichment analysis pointed to MAPK signalling, endocytosis, regulation of actin cytoskeleton, mTOR signalling, autophagy and immune-related pathways. The results indicate extensive restructuring of gill gene expression during repeated thermal cycling and suggest that the gill is a major site of molecular adaptation to fluctuating thermal environments. Overall, the present study expands the available transcriptomic resources for C. magur and provides a molecular framework for investigating thermal resilience of air-breathing catfish under changing climatic conditions.
Singh, M., Saini, V.P., 2026. Gill transcriptomic insights into adaptive response of Clarias magur to diurnal thermal fluctuations. Research Biotica 8(3), 115-124. DOI: 10.54083/ResBio/8.3.2026/115-124.
Clarias magur, DEGs, Diurnal heat stress, Gill transcriptome, Heat adaptation
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