Thermal sensitivity in dual-breathing ectotherms: Embryos and mothers determine species' vulnerability to climate change

Understanding the life-stage specific vulnerability of ectotherms to temperature increases is crucial to accurately predicting the consequences of current and future global climate change. Here, we examined ontogeny-specific thermal vulnerability of three intertidal, bimodal (i.e., air and water) breathing crabs from tropical and warm temperate latitudes to address this issue. Spawning females and embryos of intertidal crabs from warm temperate latitudes were more vulnerable to temperature increases than tropical conspecifics, particularly in water. Our findings do not fully support the Climate Variability Hypothesis for setting upper thermal limits, but correspond with the Oxygen- and Capacity-Limited Thermal Tolerance hypothesis, suggesting ontogeny-specific aerobic capacity dictates overall species' thermal sensitivity. Bimodal breathing efficiency as an evolutionary adaptation, ontogenetic stage and local climate adaptation are therefore significant factors to consider when evaluating the vulnerability of intertidal ectotherms to temperature increases and the consequences of climate changes for intertidal organisms, populations and communities.