Divergent respiratory modes drive differences in heat tolerance and habitat use among tropical intertidal crabs

Physiological adaptations for amphibious living underpin successful sea-to-land transitions and shape thermal tolerance. Intertidal brachyurans crabs independently evolved contrasting respiratory strategies: air-breathing lungs in fiddler crabs (Gelasiminae) and water dependent gill respiration in sentinel crabs (Macrophthalmidae). How these strategies influence thermal performance, vulnerability to climate change, and habitat use remains poorly understood. We examined whether air- versus water-