Temperature Extremes and Sex-Related Physiology, Not Environmental Variability, Are Key in Explaining Thermal Sensitivity of Bimodal-Breathing Intertidal Crabs

Global temperature increases are predicted to have pronounced negative effects on the metabolic performance of both terrestrial and aquatic organisms. These may be even more in intertidal organisms that subject multiple, abruptly changing abiotic stressors land-sea transition zone. Of available studies targeting environment, emphasis has largely been water-breathing model this selective focus resulted limited reliable forecasts impact global warming primarily air-breathing species. We investigated thermal sensitivity six phylogenetically related fiddler crab species occupy different microhabitats shores from south America east Asia test how bimodal-breathing ectotherms cope with stress. examined physiology limits crabs by measuring their cardiac function oxygen consumption along a gradient. Their specific microhabitat was also appraised. found subtropical inhabiting vegetated lower upper lethal temperatures therefore greater comparison tropical counterparts. Additionally, females exhibited higher males. Our results contradict previous predictions latitudes experience variability broader latitudinal distributions, phenotypic plasticity sensitivity. Furthermore, demonstrated female respect males strongly suggests role gametogenesis physiological dimorphism observations ultimately, advocates for further sex-biased development-biased before drawing any generalizations based single sex or life stage.