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Thermodynamics is a major factor determining rates of energy expenditure, rates of biochemical dynamics, and ultimately the biological and ecological processes linked with resilience to global warming in ectothermic organisms. Nonetheless, whether ectothermic organisms exhibit general adaptive metabolic responses to cope with worldwide variation in thermal conditions has remained as an open question. Here we combine a model comparison approach with a global dataset of standard metabolic rates (SMR), including 1,160 measurements across 788 species of aquatic invertebrates, insects, fishes, amphibians and reptiles, to investigate the association between metabolic rates and environmental temperatures in their respective habitats. Our analyses suggest that variation in SMR after removing allometric and thermodynamic effects is best explained by the temperature range encountered across seasons, which always provided a better fit than the average temperature for the hottest and coldest month and mean annual temperatures. This pattern was consistent across taxonomic groups and robust to sensitivity analyses. Nonetheless, aquatic and terrestrial lineages responded differently to seasonality, with SMR declining – 6.8% °C−1 of thermal range across seasons in aquatic organisms and increasing 2.8% °C−1 in terrestrial organisms. These responses may reflect alternative strategies to mitigate the impact of increments in warmer temperatures on energy expenditure, either by means of metabolic reduction in thermally homogeneous water bodies or effective behavioral thermoregulation to exploit temperature heterogeneity on land. • Energy turnover rates in ectothermic organisms are sensitive to environmental temperatures, yet it remains unclear how different lineages adapt to contrasting thermal environments. • We studied how metabolism varies geographically across ectotherms taxa, providing evidence of adaptation to temperature variability across ectothermic lineages. • Whereas terrestrial organisms exhibit elevated metabolic rates to take advantage of environmental heterogeneity in temperatures, aquatic organisms adopt a strategy of metabolic reduction to save energy during warm seasons. [ABSTRACT FROM AUTHOR]

Abstract: The zooplankter Daphnia exilis was found recently in reservoirs of central Chile. This species has been described as being tolerant to osmotic stress and chemical pollution, although the available information about its ecological properties is limited. Motivated by likelihood of being witnesses to a biological invasion, in this study we contribute to expand the knowledge of this exotic species through evaluating its ability to respond phenotypically to two major ecological factors: predation risk and food availability. Specifically, we analysed shifts in life-history and morphological traits of D. exilis in response to fish-released infochemicals, at different food densities. Our results revealed that the organisms were affected in their temporal trajectories of body size and shape, as well as in maturation time and fertility, in response to both predator cues and food availability. The presence of fish kairomones led to a decrease of age at maturity, and an increase of reproduction size and fecundity, especially at lower levels of resources. Our analyses indicated that asymptotic body size was affected only by food level, but the rate of increase in body size was sensitive to both fish kairomones and food level. The relative length of the tail spine decreased during early ontogenetic states, reaching a minimum around the age at maturity. This pattern was significantly enhanced in the presence of fish kairomones. However, our results did not match completely the typical responses of daphnids to fish kairomones. [Copyright &y& Elsevier]

Abstract: Subterranean mammals show lower than–allometrically expected–basal metabolic rates (BMR), and several competing hypotheses were suggested to explain how physical microenvironmental conditions and underground life affect subterranean mammalian energetics. Two of these are the thermal-stress and the cost-of-burrowing hypotheses. The thermal-stress hypothesis posits that a lower mass-independent BMR reduces overheating in burrows where convective and evaporative heat loss is low, whereas the cost-of-burrowing hypothesis states that a lower mass-independent BMR may compensate for the extremely high energy expenditure of digging during foraging activity. In this paper we tested both hypotheses at an intraspecific level. We compared seven populations of the subterranean rodent Spalacopus cyanus or cururo from different geographic localities with contrasting habitat conditions. We measured BMR and digging metabolic rate (DMR) through open flow respirometry. Our results support neither the thermal-stress nor the cost-of-burrowing hypothesis. Cururos from habitats with contrasting climatic and soil conditions exhibited similar BMR and DMR when measured under similar semi-natural conditions. It is possible that S. cyanus originated in Andean locations where it adapted to relatively hard soils. Later, when populations moved into coastal areas characterized by softer soils, they may have retained the original adaptation without further phenotypic changes. [Copyright &y& Elsevier]

Abstract: What are the consequences of the natural variation in maternal body mass on offspring energetic performance? How are performance traits related to thermal physiology and energetics phenotypically integrated on offspring? To answer these questions, fifty breeding pairs of the common terrestrial isopod Porcellio laevis were set up in the lab. Physiological performance, thermal tolerance and thermal sensitivity were measured in F1 adults. Maternal effects were estimated as: the direct influence of maternal body mass and the variation associated with mothers. Phenotypic integration was evaluated using path analysis. Our results show that: (1) maternal body size affects positively offspring long-term metabolism, (2) maternal variation was significant in many of the physiological traits and (3) there is an intricate set of relationships among traits and importantly, that offspring exhibited compensational strategies among metabolism, thermal sensitivity and thermal tolerance traits. Even if we cannot clearly state whether these maternal influences were because of the genes or the environment that mothers provided and thus no predictions can be done regarding their evolutionary consequences, it seems clear that the role of maternal effects on physiology can no longer be ignored. In this sense, there''s a lot to be gained by incorporating explicit experimental protocols to test for maternal effects. [Copyright &y& Elsevier]