Abstract
Abstract
Torpor is a physiological strategy used by which some species conserve energy by lowering metabolic rates and body temperatures. While mammalian hibernation is well-studied, the molecular mechanisms governing the rapid entry into avian torpor remain poorly understood. This study represents the first multi-tissue whole-transcriptomic analysis of torpor entry in an avian system. By combining real-time thermal imaging and respirometry with transcriptomic profiling across seven tissues, we identified the key molecular pathways orchestrating this transition in Anna’s hummingbirds (
Calypte anna
). Our results reveal that avian torpor entry is characterised by a subtle transcriptomic change (
Significance Statement
Torpor allows animals to dramatically reduce energy expenditure during periods of energetic deficit, yet its molecular regulation in non-mammals remains poorly understood. Using multi-tissue transcriptomics, we examined the transition from normothermy to deep torpor in Anna’s hummingbirds. Surprisingly, tissues undergo limited transcriptomic remodeling (1–4% of genes differentially expressed per tissue), unlike mammalian hibernators (∼15–60%). Hummingbirds regulate key pathways shared with mammals—arresting translation, transcription, and the cell cycle while priming mitochondrial metabolism for rapid arousal—but achieve them with minimal transcriptomic reorganization. The degree of transcriptomic changes observed, despite these interesting findings, suggest that avian torpor may rely more heavily on post-transcriptional and post-translational regulation than previously appreciated and provides a molecular framework for understanding the evolution of dormancy across vertebrates.