Citrate synthase activity does not account for age-related differences in maximum aerobic performance in House Sparrows (Passer domesticus).

We measured basal (BMR) and peak metabolic rates (PMR) in juvenile and adult House Sparrows. Juvenile birds had significantly higher BMR, but lower PMR than adult birds, despite having statistically indistinguishable body masses. We then evaluated the relation between PMR and masses of central and peripheral organs and found that pectoral muscle mass best correlated with PMR in both groups, accounting for about 35% of the variation in PMR. Because citrate synthase (CS) has such major importance in affecting the first committed step in the tricarboxylic acid cycle, we characterized CS activity levels In extracted muscles to see if this better explained age-related differences in peak aerobic performance. Surprisingly, juvenile sparrows had significantly higher CS activity levels than adults (197.8 vs. 179.0 μM g-1 min -1, respectively).This higher enzyme activity in juveniles was completely offset by their significantly smaller proportion of flight musculature relative to body mass (17.7 % in adults vs. 15.3% in juveniles). Consequently, ontogenetic changes in relative sizes of organs best accounts for agerelated differences in peak metabolic rate

Membrane fatty acid composition and longevity of mammals and birds

The fatty acid composition of membrane lipids varies systematically among species in a manner that is consistent with their metabolic rate and longevity. Because the susceptibility of fatty acids to peroxidation relates directly to their extent of unsaturation, it is possible to calculate a peroxidation index (PI) for membranes through characterization of their specific fatty acid composition. Long-living mammals and birds have membrane lipids with a lower PI than shorter-living species. Bird and mammal species with the same maximum life span also have membrane lipids with essentially the same PI. Exceptionally long-living mammals and birds usually have membrane lipids high in monounsaturates, but low in polyunsaturates, with the consequence that the PI of their membrane lipids is as low as expected for their respective longevity. Longevity variation within species (whether due to calorie-restriction, extended longevity associated with specific strains, queen-worker differences in honey bees or inherited longevity differences among humans) is also associated with differences in membrane composition and PI. Membrane composition is specific for each species and PI appears to generally be resistant to dietary manipulation. It is postulated that membrane fatty acid composition is an important influence on aging and the determination of maximum life span

Effect of temperature on the rate of ageing : an experimental study of the Blowfly Calliphora stygia

All organisms age, the rate of which can be measured by demographic analysis of mortality rates. The rate of ageing is thermally sensitive in ectothermic invertebrates and we examined the effects of temperature on both demographic rates of ageing and on cellular senescence in the blowfly, Calliphora stygia. The short lifespan of these flies is advantageous for demographic measurements while their large body size permits individual-based biochemical characterisation. Blowflies maintained at temperatures from 12°C to 34°C had a five to six-fold decrease in maximum and average longevity, respectively. Mortality rates were best described by a two-phase Gompertz relation, which revealed the first-phase of ageing to be much more temperature sensitive than the second stage. Flies held at low temperatures had both a slower first-phase rate of ageing and a delayed onset of second-phase ageing, which significantly extended their longevity compared with those at high temperatures. Blowflies that were transferred from 29°C to 15°C had higher first-phase mortality rates than those of flies held at constant 15°C, but their onset of second-phase ageing was deferred beyond that of flies held constantly at this temperature. The accumulation of fluorescent AGE pigment, a measure of cellular oxidative damage, increased steadily over time in all blowflies, irrespective of the temporal pattern of mortality. Pigment accumulated steadily during periods of ‘negligible senescence’, as measured by minimal rate of mortality, and the rate of accumulation was significantly affected by temperature. Thus accumulation of AGE pigment is more representative of chronological age than a reflection of biological age or a cause of mortality

Ten ways to get a grip on resident co-production within medical education change

The Royal College of Physicians and Surgeons of Canada (RCPSC) is transforming its national approach to postgraduate medical education by transitioning all specialty programs to competency based medical education (CBME) curriculums over a seven-year period. Queen’s University, with special permission from the RCPSC, launched CBME curricula for all incoming residents across its 29 specialty programs in July 2017. Resident engagement, empowerment, and co-production through this transition has been instrumental in successful implementation of CBME at Queen’s University. This article aims to use our own experience at Queen’s in the context of current literature and rooted in change leadership theory, to provide a guide for educators, learners, and institutions on how to leverage the interest and enthusiasm of trainees in the transition to CBME in postgraduate training. The following ten tips provides a model for avoiding the “black ice” type pitfalls that can arise with learner involvement and ensure a smoother transition for other institutions moving forward with CBME implementation

Geographical variation in the standard physiology of brushtail possums (Trichosurus): implications for conservation translocations

Identifying spatial patterns in the variation of physiological traits that occur within and between species is a fundamental goal of comparative physiology. There has been a focus on identifying and explaining this variation at broad taxonomic scales, but more recently attention has shifted to examining patterns of intra-specific physiological variation. Here we examine geographic variation in the physiology of brushtail possums (Trichosurus), widely distributed Australian marsupials, and discuss how pertinent intra-specific variation may be to conservation physiology. We found significant geographical patterns in metabolism, body temperature, evaporative water loss and relative water economy. These patterns suggest that possums from warmer, drier habitats have more frugal energy and water use and increased capacity for heat loss at high ambient temperatures. Our results are consistent with environmental correlates for broad-scale macro-physiological studies, and most intra-generic and intra-specific studies of marsupials and other mammals. Most translocations of brushtail possums occur into Australia\u27s arid zone, where the distribution and abundance of possums and other native mammals have declined since European settlement, leading to reintroduction programmes aiming to re-establish functional mammal communities. We suggest that the sub-species T. vulpecula hypoleucus from Western Australia would be the most physiologically appropriate for translocation to these arid habitats, having physiological traits most favourable for the extreme Ta, low and variable water availability and low productivity that characterize arid environments. Our findings demonstrate that geographically widespread populations can differ physiologically, and as a consequence some populations are more suitable for translocation to particular habitats than others. Consideration of these differences will likely improve the success and welfare outcomes of translocation, reintroduction and management programmes

A \u27slow pace of life\u27 in Australian old-endemic passerine birds is not accompanied by low basal metabolic rates

Life history theory suggests that species experiencing high extrinsic mortality rates allocate more resources toward reproduction relative to self-maintenance and reach maturity earlier (\u27fast pace of life\u27) than those having greater life expectancy and reproducing at a lower rate (\u27slow pace of life\u27). Among birds, many studies have shown that tropical species have a slower pace of life than temperate-breeding species. The pace of life has been hypothesized to affect metabolism and, as predicted, tropical birds have lower basal metabolic rates (BMR) than temperate-breeding birds. However, many temperate-breeding Australian passerines belong to lineages that evolved in Australia and share \u27slow\u27 life-history traits that are typical of tropical birds. We obtained BMR from 30 of these \u27old-endemics\u27 and ten sympatric species of more recently arrived passerine lineages (derived from Afro-Asian origins or introduced by Europeans) with \u27faster\u27 life histories. The BMR of \u27slow\u27 temperate-breeding old-endemics was indistinguishable from that of new-arrivals and was not lower than the BMR of \u27fast\u27 temperate-breeding non-Australian passerines. Old-endemics had substantially smaller clutches and longer maximal life spans in the wild than new arrivals, but neither clutch size nor maximum life span was correlated with BMR. Our results suggest that low BMR in tropical birds is not functionally linked to their \u27slow pace of life\u27 and instead may be a consequence of differences in annual thermal conditions experienced by tropical versus temperate species

Inexplicable inefficiency of avian molt? Insights from an opportunistically breeding arid-zone species, Lichenostomus penicillatus.PLoSONE

Abstract The majority of bird species studied to date have molt schedules that are not concurrent with other energy demanding life history stages, an outcome assumed to arise from energetic trade-offs. Empirical studies reveal that molt is one of the most energetically demanding and perplexingly inefficient growth processes measured. Furthermore, small birds, which have the highest mass-specific basal metabolic rates (BMR m ), have the highest costs of molt per gram of feathers produced. However, many small passerines, including white-plumed honeyeaters (WPHE; Lichenostomus penicillatus), breed in response to resource availability at any time of year, and do so without interrupting their annual molt. We examined the energetic cost of molt in WPHE by quantifying weekly changes in minimum resting metabolic rate (RMR min ) during a natural-molt period in 7 wild-caught birds. We also measured the energetic cost of feather replacement in a second group of WPHEs that we forced to replace an additional 25% of their plumage at the start of their natural molt period. Energy expenditure during natural molt revealed an energy conversion efficiency of just 6.9% (60.57) close to values reported for similar-sized birds from more predictable north-temperate environments. Maximum increases in RMR min during the molt of WPHE, at 82% (65.59) above individual pre-molt levels, were some of the highest yet reported. Yet RMR min maxima during molt were not coincident with the peak period of feather replacement in naturally molting or plucked birds. Given the tight relationship between molt efficiency and mass-specific metabolic rate in all species studied to date, regardless of life-history pattern (Efficiency (%) = 35.720N10 20.494BMRm ; r 2 = 0.944; p = ,0.0001), there appears to be concomitant physiological costs entrained in the molt period that is not directly due to feather replacement. Despite these high total expenditures, the protracted molt period of WPHE significantly reduces these added costs on a daily basis

Temporal pattern of foraging and microhabitat use by Galápagos marine iguanas, Amblyrhynchus cristatus

We observed a colony of marine iguanas ( Amblyrhynchus cristatus ) on Isla Fernandina, Galápagos, Ecuador, while measuring local micrometeorological and tidal conditions. We found size-related differences in foraging mode, with smaller iguanas feeding intertidally during daytime low tides and larger iguanas feeding subtidally. Despite having greater opportunity, subtidal foragers did not time their foraging bouts or exploit their environment in ways that optimized their period at high body temperature. Instead, the foraging schedule of these iguanas served to maximize their rate of rewarming following emergence from the cool sea. Intertidal feeders, by contrast, showed much greater behavioral flexibility in attempting to exploit their thermal environment. We suggest that size-ordered differences in marine iguana thermoregulatory behavior reflect underlying ontogenetic changes in costs and benefits of thermoregulation due to differences in predator pressure, quantity of food and electrolytes taken at each feeding, mode of foraging, and agonistic tendencies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47800/1/442_2004_Article_BF00318031.pd

Low intensity blood parasite infections do not reduce the aerobic performance of migratory birds

Blood parasites (Haemosporidia) are thought to impair the flight performance of infected animals, and therefore, infected birds are expected to differ from their non-infected counterparts in migratory capacity. Since haemosporidians invade host erythrocytes, it is commonly assumed that infected individuals will have compromised aerobic capacity, but this has not been examined in free-living birds. We tested if haemosporidian infections affect aerobic performance by examining metabolic rates and exercise endurance in migratory great reed warblers (Acrocephalus arundinaceus) experimentally treated with Plasmodium relictum pGRW04 and in naturally infected wild birds over consecutive life-history stages. We found no effect of acute or chronic infections on resting metabolic rate, maximum metabolic rate or exercise endurance in either experimentally treated or free-living birds. Oxygen consumption rates during rest and while undergoing maximum exercise as well as exercise endurance increased from breeding to migration stages in both infected and non-infected birds. Importantly, phenotypic changes associated with preparation for migration were similarly unaffected by parasitaemia. Consequently, migratory birds experiencing parasitaemia levels typical of chronic infection do not differ in migratory capacity from their uninfected counterparts. Thus, if infected hosts differ from uninfected conspecifics in migration phenology, other mechanisms besides aerobic capacity should be considered