22A key element missing from many predictive models of the impacts of climate change 23 on intertidal ectotherms is the role of individual behaviour. In this synthesis, using 24 littorinid snails as a case study, we show how thermoregulatory behaviours may 25 buffer changes in environmental temperatures. These behaviours include either a 26 flight response, to escape the most extreme conditions and utilize warmer or cooler 27 environments; or a fight response, where individuals modify their own environments 28 to minimize thermal extremes. A conceptual model, generated from studies of 29 littorinid snails, shows that various flight and fight thermoregulatory behaviours may 30 allow an individual to widen its thermal safety margin (TSM) under warming or 31 cooling environmental conditions and hence increase species' resilience to climate 32 change. Thermoregulatory behaviours may also buffer sublethal fitness impacts 33 associated with thermal stresses. Through this synthesis, we emphasise that future 34 studies need to consider not only animals' physiological limits but also their capacities 35 to buffer the impact of climate change through behavioural responses. Current 36 generalizations, made largely on physiological limits of species, often neglect the 37 buffering effects of behaviour and may, therefore, provide an over-estimation of 38 vulnerability, and consequently poor prediction of the potential impacts of climate 39 change on intertidal ectotherms. 40 41
Anticipatory changes in organismal responses, triggered by reliable environmental cues for future conditions, are key to species' persistence in temporally variable environments. Such responses were tested by measuring the physiological performance of a tropical highshore oyster in tandem with the temporal predictability of environmental temperature. Heart rate of the oyster increased with environmental temperatures until body temperature reached ∼377C, when a substantial depression occurred (∼60%) before recovery between ∼427 and 477C, after which cardiac function collapsed. The sequential increase, depression, and recovery in cardiac performance aligned with temporal patterns in rock surface temperatures, where the risk of reaching temperatures close to the oysters' lethal limit accelerates if the rock heats up beyond ∼377C, coinciding closely with the body temperature at which the oysters initiate metabolic depression. The increase in body temperature over a critical threshold serves as an early-warning cue to initiate anticipatory shifts in physiology and energy conservation before severe thermal stress occurs on the shore. Cross-correlating the onset of physiological mechanisms and temporal structures in environmental temperatures, therefore, reveals the potential role of reliable real-time environmental cues for future conditions in driving the evolution of anticipatory responses.
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