Choidavis2001

Non-shivering thermogenesis can promote negative energy balance and weight loss. In this study, we identify a contextual stimulus that induces rapid and robust thermogenesis in skeletal muscle. Rats exposed to the odor of a natural predator (ferret odor) show elevated skeletal muscle temperatures detectable as quickly as 2 min after exposure, reaching maximum thermogenesis of >1.5 °C at 10-15 min. Mice exhibit a similar thermogenic response to the same odor. Ferret odor induces a significantly larger and qualitatively different response than do novel or aversive odors, fox odor, or moderate restraint stress. Exposure to predator odor increases energy expenditure, and both the thermogenic and energetic effects persist when physical activity levels are controlled. Predator odor-induced muscle thermogenesis is subject to associative learning as exposure to a conditioned stimulus provokes a rise in muscle temperature in the absence of the odor. The ability of predator odor to induce thermogenesis is predominately controlled by sympathetic nervous system activation of β-adrenergic receptors, as unilateral sympathetic lumbar denervation and a peripherally acting β-adrenergic antagonist significantly inhibit predator odor-induced muscle thermogenesis. The potential survival value of predator odor-induced changes in muscle physiology is reflected in an enhanced resistance to running fatigue. Lastly, predator odor-induced muscle thermogenesis imparts a meaningful impact on energy expenditure as daily predator odor exposure significantly enhances weight loss with mild calorie restriction. This evidence signifies contextually provoked, centrally mediated muscle thermogenesis that meaningfully impacts energy balance. © 2020. Published by The Company of Biologists Ltd.Microclimatic variability in tropical forests plays a key role in shaping species distributions and their ability to cope with environmental change, especially for ectotherms. Nonetheless, currently available climatic datasets lack data from the forest interior and, furthermore, our knowledge of thermal tolerance among tropical ectotherms is limited. We therefore studied natural variation in the microclimate experienced by tropical butterflies in the genus Heliconius across their Andean range in a single year. We found that the forest strongly buffers temperature and humidity in the understory, especially in the lowlands where temperatures are more extreme. There were systematic differences between our yearly records and macroclimate databases (WorldClim2), with lower interpolated minimum temperatures and maximum temperatures higher than expected. We then assessed thermal tolerance of ten Heliconius butterfly species in the wild and showed that populations at high elevations had significantly lower heat tolerance than those at lower elevations. However, when we reared populations of the widespread H. erato from high and low elevations in a common-garden environment, the difference in heat tolerance across elevations was reduced, indicating plasticity in this trait. Microclimate buffering is not currently captured in publicly available datasets but could be crucial for enabling upland shifting of species sensitive to heat such as highland Heliconius Plasticity in thermal tolerance may alleviate the effects of global warming on some widespread ectotherm species, but more research is needed to understand the long-term consequences of plasticity on populations and species. © 2020. Published by The Company of Biologists Ltd.Insects produce a variety of adhesives for diverse functions such as locomotion, mating, egg or pupal anchorage to substrates. Syk inhibitor Although they are important for the biology of organisms and potentially represent a great resource for developing new materials, insect adhesives have been little studied so far. Here, we examined the adhesive properties of the larval glue of Drosophila melanogaster This glue is made of glycosylated proteins and allows the animal to adhere to a substrate during metamorphosis. We designed an adhesion test to measure the pull-off force required to detach a pupa from a substrate and to evaluate the contact area covered by the glue. We found that the pupa adheres with similar forces to a variety of substrates (with distinct roughness, hydrophilic and charge properties). We obtained an average pull-off force of 217 mN, corresponding to 15 500 times the weight of a pupa and adhesion strength of 137-244 kPa. Surprisingly, the pull-off forces did not depend on the contact area. Our study paves the way for a genetic dissection of the components of D. melanogaster glue that confer its particular adhesive properties. © 2020. Published by The Company of Biologists Ltd.An animal's body condition provides valuable information for ecophysiological studies, and is an important measure of fitness in population monitoring and conservation. While both the external body shape of an animal, as well as its internal tissues (i.e. fat content) can be used as measures of body condition, the relationship between the two is not always linear. We compared the morphological body condition (external metric obtained through aerial photogrammetry) of migrating humpback whales (Megaptera novaeangliae) with their outer blubber lipid concentration (internal metric obtained through blubber biopsy sampling) off south-west Australia early and late in the breeding season (spanning ∼4.5 months). The external body condition index of juvenile and adult humpback whales decreased with 26.9 (from 18.8 to -8.1%) and 12.0 percentage points (from 8.6 to -3.4%) between the early and late phase, respectively. In contrast, we found no intra-seasonal change in blubber lipid concentration, and no difference between reproductive classes (juveniles, adults and lactating females), however the small sample size prevented us from effectively testing these effects. Importantly however, in the 33 animals for which paired metrics were obtained, we found no correlation between the morphometric body condition index and the blubber lipid concentration of individual whales. The lack of a linear relationship suggest that changes in outer blubber lipid concentration do not reflect external changes in body shape, thus limiting the utility of outer blubber lipid reserves for individual body condition evaluation. The wider spectrum of change in body morphometry captured with aerial photogrammetry, supports the use of body morphometry as a reliable and well tested method. © 2020. Published by The Company of Biologists Ltd.