High caloric intake can increase production of reactive oxygen and nitrogen species. We examined whether the emergence of the migratory phenotype, primarily signalled by increased food intake and fuelling, is accompanied by changes in oxidative status. We induced autumn migration followed by a non-migratory wintering phase in common quails (Coturnix coturnix). We compared three markers of oxidative status - oxidative damage to lipids expressed as thiobarbituric acid reactive substances (TBARS); superoxide dismutase (SOD); and glutathione peroxidase (GPx) - between birds sampled during the migratory and non-migratory phase. We found that the emergence of the migratory phenotype was associated with (i) higher levels of TBARS in the liver; (ii) lower levels of SOD in red blood cells and, marginally, in the liver; (iii) higher levels of GPx in the pectoral muscle; and (iv) sex-specific changes in red blood cells and liver. We found no link between food intake and variation in markers of oxidative status in any of the tissues examined, despite food intake being higher in the migratory birds. However, the increase in body mass was positively correlated with muscle GPx activity as birds entered the pre-migratory fattening phase, while the amount of decrease in body mass was negatively correlated with muscle GPx as birds transitioned to the non-migratory phase. Such correlations were absent in red blood cells and liver. Our work suggests that during the emergence of the migratory phenotype, birds might strategically displace oxidative costs on the liver in order to safeguard the pectoral muscles, which have a fundamental role in successfully completing the migratory flight.The aerial hunting behaviours of birds are strongly influenced by flight morphology and ecology, but little is known of how this relates to the behavioural algorithms guiding flight. Here, we used GPS loggers to record the attack trajectories of captive-bred gyrfalcons (Falco rusticolus) during their maiden flights against robotic aerial targets, which we compared with existing flight data from peregrine falcons (Falco peregrinus). The attack trajectories of both species were well modelled by a proportional navigation (PN) guidance law, which commands turning in proportion to the angular rate of the line-of-sight to target, at a guidance gain N However, naive gyrfalcons operate at significantly lower values of N than peregrine falcons, producing slower turning and a longer path to intercept. Gyrfalcons are less manoeuvrable than peregrine falcons, but physical constraint is insufficient to explain the lower values of N we found, which may reflect either the inexperience of the individual birds or ecological adaptation at the species level. For example, low values of N promote the tail-chasing behaviour that is typical of wild gyrfalcons and which apparently serves to tire their prey in a prolonged high-speed pursuit. Likewise, during close pursuit of typical fast evasive prey, PN will be less prone to being thrown off by erratic target manoeuvres at low guidance gain. The fact that low-gain PN successfully models the maiden attack flights of gyrfalcons suggests that this behavioural algorithm is embedded in a guidance pathway ancestral to the clade containing gyrfalcons and peregrine falcons, though perhaps with much deeper evolutionary origins.The periwinkle snail Echinolittorina malaccana, for which the upper lethal temperature is near 55°C, is one of the most heat-tolerant eukaryotes known. We conducted a multi-level investigation - including cardiac physiology, enzyme activity, and targeted and untargeted metabolomic analyses - that elucidated a spectrum of adaptations to extreme heat in this organism. All systems examined showed heat intensity-dependent responses. Under moderate heat stress (37-45°C), the snail depressed cardiac activity and entered a state of metabolic depression. The global metabolomic and enzymatic analyses revealed production of metabolites characteristic of oxygen-independent pathways of ATP generation (lactate and succinate) in the depressed metabolic state, which suggests that anaerobic metabolism was the main energy supply pathway under heat stress (37-52°C). The metabolomic analyses also revealed alterations in glycerophospholipid metabolism under extreme heat stress (52°C), which likely reflected adaptive changes to maintain membrane structure. Small-molecular-mass organic osmolytes (glycine betaine, choline and carnitine) showed complex changes in concentration that were consistent with a role of these protein-stabilizing solutes in protection of the proteome under heat stress. This thermophilic species can thus deploy a wide array of adaptive strategies to acclimatize to extremely high temperatures.Runners are commonly modeled as spring-mass systems, but the traditional calculations of these models rely on discrete observations during the gait cycle (e.g. maximal vertical force) and simplifying assumptions (e.g. leg length), challenging the predicative capacity and generalizability of observations.  https://www.selleckchem.com/products/pt2385.html  We present a method to model runners as spring-mass systems using nonlinear regression (NLR) and the full vertical ground reaction force (vGRF) time series without additional inputs and fewer traditional parameter assumptions. We derived and validated a time-dependent vGRF function characterized by four spring-mass parameters - stiffness, touchdown angle, leg length and contact time - using a sinusoidal approximation. Next, we compared the NLR-estimated spring-mass parameters with traditional calculations in runners. The mixed-effect NLR method (ME NLR) modeled the observed vGRF best (RMSE155 N) compared with a conventional sinusoid approximation (RMSE 230 N). Against the conventional methods, its estimations provided similar stiffness approximations (-0.2±0.6 kN m-1) with moderately steeper angles (1.2±0.7 deg), longer legs (+4.2±2.3 cm) and shorter effective contact times (-12±4 ms). Together, these vGRF-driven system parameters more closely approximated the observed vertical impulses (observed 214.8 N s; ME NLR 209.0 N s; traditional 223.6 N s). Finally, we generated spring-mass simulations from traditional and ME NLR parameter estimates to assess the predicative capacity of each method to model stable running systems. In 6/7 subjects, ME NLR parameters generated models that ran with equal or greater stability than traditional estimates. ME NLR modeling of the vGRF in running is therefore a useful tool to assess runners holistically as spring-mass systems with fewer measurement sources or anthropometric assumptions. Furthermore, its utility as statistical framework lends itself to more complex mixed-effects modeling to explore research questions in running.