Thermoregulatory consequences of growing up during a heatwave or a cold snap

Changes in environmental temperature during the developmental period can affect growth, metabolism, and temperature tolerance of the offspring. We know little about whether such changes remain to adulthood, which is important to understand the links between climate change, development, and fitness. We investigated if phenotypic consequences of the thermal environment in early life remained in adulthood in two studies on Japanese quail (Coturnix japonica). Birds were raised under simulated heatwave-, cold snap-or control conditions, from hatching until halfway through the growth period, and then in a common garden until reproductively mature. We measured biometric and thermoregulatory (metabolic heat production [MHP], evaporative water and heat loss [EWL, EHL] and body temperature) responses to variation in submaximal air temperature at the end of the thermal acclimation period and in adulthood. Warm birds had lower MHP than control birds at the end of the thermal acclimation period and, in the warmest temperature studied (40{degrees}C), also had higher evaporative cooling capacity compared to controls. No analogous responses were recorded in cold birds, though they had higher EWL than controls in all but the highest test temperature. None of the effects found at the end of the heatwave-or cold snap period remained until adulthood. This implies that chicks exposed to higher temperatures could be more prepared to counter heat stress as juveniles, but that they do not enjoy any advantages of such developmental conditions when facing high temperatures as adults. Conversely, cold temperature does not seem to confer any priming effects in adolescence.