Showing papers in "Physiological and Biochemical Zoology in 2018"
TL;DR: Exposure to maternal THs within naturally occurring range affected offspring fitness–related traits (growth and survival) in birds and fish, making THs an interesting mechanism underlying maternal effects, which likely shape offspring phenotypes.
Abstract: Maternal effects are currently acknowledged as important causes of transgenerational phenotypic variation and a potential mechanism to adapt offspring to predicted environments, thus having a pivotal role in ecology and evolution. Research in hormonal mechanism underlying maternal effects has focused heavily on steroid hormones. Other hormones, such as thyroid hormones (THs; thyroxine and triiodothyronine), have been largely ignored in ecological research until recently. We summarize the recent findings, identify knowledge gaps, and provide future research directions investigating the role of TH-mediated maternal effects in ecological context across taxa. Surprisingly, data on the sources of naturally occurring variation in maternal THs and their fitness effects are lacking in most vertebrate taxa. There is considerable variation in maternal TH levels in eggs across taxa. Avian egg THs show heritable variation, and data from fish and amphibians suggest female consistency in egg TH levels. In birds, variation in maternal THs was associated with important ecological factors, such as food availability and temperature. THs also showed intraindividual variation varying systematically within clutches. Importantly, exposure to maternal THs within naturally occurring range affected offspring fitness-related traits (growth and survival) in birds and fish. These findings make THs an interesting mechanism underlying maternal effects, which likely shape offspring phenotypes.
60 citations
TL;DR: The results indicate clear seasonal metabolic patterns involving oxidative stress during summer as well as winter, and oxidative stress seems to be more prominent during warming because of the increased aerobic metabolism.
Abstract: Seasonal temperature changes may take organisms to the upper and lower limit of their thermal range, with respective variations in their biochemical and metabolic profile. To elucidate these traits, we investigated metabolic and antioxidant patterns in tissues of sea bream Sparus aurata during seasonal acclimatization for 1 yr in the field. Metabolic patterns were assessed by determining lactate dehydrogenase, citrate synthase, and β-hydroxyacyl CoA dehydrogenase activities, their kinetic properties and plasma levels of glucose, lactate, and triglycerides and tissue succinate levels. Oxidative stress was assessed by determining antioxidant enzymes superoxide dismutase, catalase, and glutathione reductase activities and levels of thiobarbituric acid reactive substances. Xanthine oxidase (XO) activity was determined as another source of reactive oxygen species (ROS) production. Furthermore, we studied the antiapoptotic protein indicator Bcl-2 and the apoptotic protein indicators Bax, Bad, ubiquitin, and caspase as well as indexes of autophagy (LC3B II/LC3B I and SQSTM1/p62) in the liver and the heart to identify possible relationships between oxidative stress and cell death. The results indicate clear seasonal metabolic patterns involving oxidative stress during summer as well as winter. During cold acclimatization, lipid oxidation is induced, while during increased temperatures, warm-induced metabolic activation and carbohydrate oxidation are observed. Thus, oxidative stress seems to be more prominent during warming because of the increased aerobic metabolism. The seasonal profile of apoptosis and XO as another source of ROS matches the results obtained in the laboratory and are interpreted within the framework of oxygen- and capacity-limited thermal tolerance.
23 citations
TL;DR: Insight is offered into how coordinated transcriptional responses for ion transporters in the gill facilitate reestablishment of osmotic homeostasis after changes in environmental salinity and evidence that the teleost gill expresses two Na+-HCO3− cotransporter-1 isoforms with different roles in freshwater and seawater acclimation is provided.
Abstract: Pupfishes (genus Cyprinodon) evolved some of the broadest salinity tolerances of teleost fishes, with some taxa surviving in conditions from freshwater to nearly 160 ppt In this study, we examined transcriptional dynamics of ion transporters and aquaporins in the gill of the desert Amargosa pupfish (Cyprinodon nevadensis amargosae) during rapid salinity change Pupfish acclimated to 75 ppt were exposed to freshwater (03 ppt), seawater (35 ppt), or hypersaline (55 ppt) conditions over 4 h and sampled at these salinities over 14 d Plasma osmolality and Cl- concentration became elevated 8 h after the start of exposure to 35 or 55 ppt but returned to baseline levels after 14 d Osmolality recovery was paralleled by increased gill Na+/K+-ATPase activity and higher relative levels of messenger RNAs (mRNAs) encoding cystic fibrosis transmembrane conductance regulator (cftr) and Na+/K+/2Cl- cotransporter-1 (nkcc1) Transcripts encoding one Na+-HCO3- cotransporter-1 isoform (nbce11) also increased in the gills at higher salinities, while a second isoform (nbce12) increased expression in freshwater Pupfish in freshwater also had lower osmolality and elevated gill mRNAs for Na+/H+ exchanger isoform-2a (nhe2a) and V-type H+-ATPase within 8 h, followed by increases in Na+/H+ exchanger-3 (nhe3), carbonic anhydrase 2 (ca2), and aquaporin-3 (aqp3) within 1 d Gill mRNAs for Na+/Cl- cotransporter-2 (ncc2) also were elevated 14 d after exposure to 03 ppt These results offer insights into how coordinated transcriptional responses for ion transporters in the gill facilitate reestablishment of osmotic homeostasis after changes in environmental salinity and provide evidence that the teleost gill expresses two Na+-HCO3- cotransporter-1 isoforms with different roles in freshwater and seawater acclimation
23 citations
TL;DR: The association between CTmax and Hct found here supports the hypothesis that thermal tolerance is affected by oxygen supply to tissue and could represent an adaptive mechanism for salmon faced with climate change.
Abstract: To evaluate whether oxygen-carrying capacity influences thermal tolerance in fishes, we reared four Chinook salmon families in present-day (+0°C) and possible future (+4°C) temperatures and assessed the response of hematocrit (Hct) to acute temperature stress. In the +4°C treatment, Hct increased above control levels when juvenile fish were exposed to their critical thermal maximum (CTmax). Conversely, no effect of temperature stress on Hct was found in the +0°C treatment. Hct was positively associated with CTmax ([Formula: see text]; [Formula: see text]), contributing to the CTmax of the +4°C treatment being significantly higher than that of the +0°C treatment (mean ± SD, [Formula: see text] and [Formula: see text], respectively). The association between CTmax and Hct found here supports the hypothesis that thermal tolerance is affected by oxygen supply to tissue. Moreover, the developmental plasticity of CTmax and Hct could represent an adaptive mechanism for salmon faced with climate change.
23 citations
TL;DR: The hypothesis that the seasonal interplay among environment, host energetics, and HPA activity initiates trade-offs in the fall that drive the increase in SFD prevalence, symptom severity, and decline in condition observed in the population through winter is proposed.
Abstract: Snake fungal disease (SFD) is an emerging threat to snake populations in the United States. Fungal pathogens are often associated with a physiological stress response mediated by the hypothalamo-pituitary-adrenal axis (HPA), and afflicted individuals may incur steep coping costs. The severity of SFD can vary seasonally; however, little is known regarding (1) how SFD infection relates to HPA activity and (2) how seasonal shifts in environment, life history, or HPA activity may interact to drive seasonal patterns of infection severity and outcomes. To test the hypothesis that SFD is associated with increased HPA activity and to identify potential environmental or physiological drivers of seasonal infection, we monitored baseline corticosterone, SFD infection severity, foraging success, body condition, and reproductive status in a field-active population of pigmy rattlesnakes. Both plasma corticosterone and the severity of clinical signs of SFD peaked in the winter. Corticosterone levels were also elevated in the fall before the seasonal rise in SFD severity. Severely symptomatic snakes were in low body condition and had elevated corticosterone levels compared to moderately infected and uninfected snakes. The monthly mean severity of SFD in the population was negatively related to population-wide estimates of body condition and temperature measured in the precedent month and positively correlated with corticosterone levels measured in the precedent month. Symptomatic females were less likely to enter reproductive bouts compared to asymptomatic females. We propose the hypothesis that the seasonal interplay among environment, host energetics, and HPA activity initiates trade-offs in the fall that drive the increase in SFD prevalence, symptom severity, and decline in condition observed in the population through winter.
22 citations
TL;DR: The results showed that the Ningaloo population of C. mydas has somewhat different thermal sensitivities than other C.Mydas populations and justified why is it necessary to collect population-specific data to accurately project the impacts of global warming on focal populations.
Abstract: The thermal environment of sea turtle embryos has marked effects on many aspects of their development and energetics and has consequences for posthatching stages Here we incubated Chelonia mydas embryos from Ningaloo Reef in Western Australia at a range of temperatures (27°, 29°, 30°, 31°, 32°, and 30° ± 5°C) to determine development rates and the pivotal temperature for sex determination We also measured embryonic growth, oxygen consumption, and carbon dioxide production throughout development at 27° and 31°C Metabolic rates were higher at 31°C than at 27°C, but total energy expenditure was greater at 27°C, with 2,281 mL of oxygen consumed compared with 1,992 mL at 31°C Respiration at both temperatures showed a pattern typical of sea turtle embryos, with peak rates occurring at approximately 85% of development and then declining toward hatching Hatchlings produced at higher incubation temperatures developed faster, were smaller, and had larger residual yolk masses than hatchlings produced at lower temperatures The pivotal temperature that produced an equal sex ratio was 292°C, with mixed sexes produced between 279° and 304°C Our results showed that the Ningaloo population of C mydas has somewhat different thermal sensitivities than other C mydas populations and justified why is it necessary to collect population-specific data to accurately project the impacts of global warming on focal populations
22 citations
TL;DR: The results suggest that this large generalist predator may not necessarily be easily characterized as a pure capital breeder, as has been previously hypothesized for ectotherms, but may rely on a mix of energy stores and opportunistic feeding to support reproduction.
Abstract: To fuel the high energetic demands of reproduction, vertebrates employ different tactics of resource use. Large sharks exhibit long gestation periods and have relatively few well-developed ...
19 citations
TL;DR: The use of these loggers will make significant advances in measuring HR in unrestrained, undisturbed animals in their natural environment during extended periods of time and has the potential to lead to novel findings.
Abstract: Cardiovascular responses of decapod crustaceans to environmental challenges have received extensive attention. However, nearly all of these studies have been restricted to lab-based experim...
19 citations
TL;DR: Sampling Arctic skates across a 1,015-m depth gradient in the Beaufort Sea found that the urea-to-TMAO ratio decreased linearly with depth, with tighter correlation than that seen in interspecific studies.
Abstract: Accumulation of trimethylamine N-oxide (TMAO) by deep-sea animals is proposed to protect proteins against the destabilizing effects of high hydrostatic pressure (the piezolyte hypothesis). Chondrichthyan fishes (sharks, rays, and chimaeras) provide a unique test of this hypothesis because shallow-living species have elevated TMAO levels to counteract the destabilizing effects of high urea levels accumulated for osmoregulation. Limited interspecific studies of chondrichthyans reveal that increasing depth correlates with decreased urea and increased TMAO levels, suggesting a dynamic balance between destabilizing forces on proteins (high urea, hydrostatic pressure) and TMAO to counteract these forces. Indeed, an inability to minimize urea levels or maximize TMAO levels has been proposed to explain why chondrichthyans are absent in the vast abyssal region. An unresolved question is whether the depth-related changes in chondrichthyan osmolytes are a flexible response to depth or whether phylogenetic differences in species-specific physiological set points for osmolytes account for the differences seen with depth. Sampling Arctic skates (Amblyraja hyperborea) across a 1,015-m depth gradient in the Beaufort Sea, we measured organic osmolytes in muscle using spectrophotometry and high-performance liquid chromatography. We found that the urea-to-TMAO ratio decreased linearly with depth, with tighter correlation than that seen in interspecific studies. Minor osmolytes, including betaine, sarcosine, and some α-amino acids, also declined with depth, apparently replaced (as with urea) by TMAO (a stronger piezolyte than those solutes). These data provide the first intraspecific evidence that flexible adjustments of osmolyte combinations are a key response for deep-sea living in individual chondrichthyans, supporting the piezolyte hypothesis.
17 citations
TL;DR: It is demonstrated that seasonal changes in reproduction are dependent on fluctuations in local environmental conditions, and researchers must account for seasonal shifts in environmental factors and reproductive traits when designing experiments and drawing conclusions about how the environment influences reproduction.
Abstract: The evolution of reproductive strategies depends on local environmental conditions. When environments are seasonal, selection favors individuals that align changes in key reproductive traits with seasonal shifts in habitat quality. Offspring habitat quality can decline through the season, and increased maternal provisioning to late-produced offspring may compensate. This shift, however, may depend on environmental factors that influence reproduction and are, themselves, subject to temporal changes (e.g., food abundance). We studied the brown anole lizard (Anolis sagrei) to demonstrate how prey abundance modifies seasonal changes in key reproductive traits. We bred lizards in controlled laboratory conditions across the reproductive season and manipulated the availability of food by providing some breeding pairs high prey availability and some low. Halfway through the season, we switched half of the breeding pairs to the opposite treatment. We measured growth of male and female lizards as well as latency to oviposit, fecundity, egg size, egg content (yolk, water, shell mass), and egg quality (steroid hormones, yolk caloric content) over this period. Higher prey availability enhanced lizard growth and some key reproductive traits (egg size, fecundity) but not others (egg content and quality). Moreover, we found that seasonal patterns of reproduction were modified by prey treatment in ways that have consequences for offspring survival. Our results demonstrate that seasonal changes in reproduction are dependent on fluctuations in local environmental conditions. Moreover, researchers must account for seasonal shifts in environmental factors and reproductive traits (and their interactions) when designing experiments and drawing conclusions about how the environment influences reproduction.
16 citations
TL;DR: The glycemic response to acute handling stress in two species of free-living sparrows is characterized and a novel technique for rapid field measurement of glucose using a human blood glucose meter, FreeStyle Lite is validated, introducing a new field technique for avian field biologists.
Abstract: Organisms experience stressors, and the physiological response to these stressors is highly conserved. Acute stress activates both the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis, increasing epinephrine, norepinephrine, and glucocorticoids, collectively promoting glucose mobilization. While this is well characterized in mammals, the hyperglycemic response to stress in avian and nonavian reptiles has received less attention. A number of factors, ranging from time of day to blood loss, are reported to influence the extent to which acute stress leads to hyperglycemia in birds. Here we characterized the glycemic response to acute handling stress in two species of free-living sparrows: white-throated sparrows (WTSPs: Zonotrichia albicollis) in St. Mary's County, Maryland, and white-crowned sparrows (WCSPs: Zonotrichia leucophrys) in Tioga Pass Meadow, California. We validated a novel technique for rapid field measurement of glucose using a human blood glucose meter, FreeStyle Lite. As expected, acute handling stress elevated blood glucose at both 15 and 30 min postcapture as compared to baseline for both WTSPs and WCSPs. In addition, handling for 30 min without bleeding had the same hyperglycemic effect as handling with serial bleeds in WCSPs. Finally, body condition that was measured as abdominal fat score predicted stress-induced blood glucose in WTSPs but not in WCSPs. Our results are consistent with the mammalian literature on acute stress and energy mobilization, and we introduce a new field technique for avian field biologists.
TL;DR: It is concluded that ecological habit is the principle factor that predicts ecophysiological trait variation and the possible geographic distribution of lowland Neotropical frogs.
Abstract: A key goal of ecology and evolution is to understand the relative contributions of environment and history in determining the geographic distribution of organisms. For the Neotropical lowla...
TL;DR: A positive correlation between parental ΔTL and nestling MDA is found, an example of how parental physiological aging could affect offspring quality in terms of oxidative stress that highlights the constraints imposed by higher rates of ΔTL during reproduction and rearing.
Abstract: Oxidative stress can contribute to an acceleration of telomere erosion, leading to cellular senescence and aging. Increased investment in reproduction is known to accelerate senescence, generally resulting in reduced future reproductive potential and survival. To better understand the role played by oxidative status and telomere dynamics in the conflict between maintenance and reproduction, it is important to determine how these factors are related in parents and their offspring. We investigated the relationship between oxidative status and telomere measurements in pied flycatchers (Ficedula hypoleuca). Total antioxidant status (TAS) in plasma, total levels of glutathione in red blood cells (RBCs), and oxidative damage in plasma lipids (malondialdehyde [MDA]) were assessed in both parents and nestlings. Telomeres were measured in RBCs in adults. Our results showed sex differences in oxidative variables in adults that are likely to be mediated by sex steroids, with testosterone and estrogens increasing and reducing, respectively, the production of reactive oxygen and nitrogen species. We found a negative association between telomere length (TL) and MDA in adults in the previous season. Moreover, TL was positively associated with TAS in females, while telomere shortening (ΔTL) correlated positively with MDA in males in the current year. These associations could be reflecting differences between sexes in reproductive physiology. We found a positive correlation between parental ΔTL and nestling MDA, an example of how parental physiological aging could affect offspring quality in terms of oxidative stress that highlights the constraints imposed by higher rates of ΔTL during reproduction and rearing.
TL;DR: Repeatable interindividual variation in hypoxia tolerance, if genetically based, could influence the capacity of species to adapt as their habitats become increasingly threatened by aquatic hypoxIA.
Abstract: The capacity of fishes to tolerate low oxygen (hypoxia) through behavioral and physiological adjustments varies among species in a fashion that correlates with oxygen availability in their ...
TL;DR: It is found that both abdominal and throat patch hue follow classical thermal performance curves, suggesting that at the species level hue is a good predictor of sprinting ability, and that the bluest individuals are the fastest individuals across temperatures.
Abstract: Physiological changes in response to environmental cues are not uncommon. Temperature has strong, predictable effects on many traits, such that many traits in ectotherms follow stereotyped ...
TL;DR: The findings suggest that the melanin-based coloration of brown trout serves as a signal to communicate a better antioxidant defense to conspecifics.
Abstract: In many vertebrate species, individuals exhibit large variation in the degree of melanin-based coloration on their body. Dark and pale individuals differ in diverse physiological and behavioral traits, suggesting that melanic coloration may reveal individual quality. However, research into the relationships between physiological and skin traits, in terms of melanin-based skin coloration, in wild fish is scant. Our correlative study aimed at investigating the relationships between physiology and melanin-based coloration of the skin of free-living brown trout (Salmo trutta Linnaeus, 1758). We scrutinized the relationships between body condition (body mass and Fulton's K condition factor), oxidative status (plasma total antioxidant capacity and amount of pro-oxidant molecules), and the degree of melanin-based skin coloration assessed by digital photography and image analysis. We found heavier fish to be, on average, darker colored than paler conspecifics. Moreover, a significant covariation between plasma total antioxidant capacity and melanic coloration was noted. Our findings suggest that the melanin-based coloration of brown trout serves as a signal to communicate a better antioxidant defense to conspecifics.
TL;DR: This study studied the African striped mouse inhabiting a seasonal environment with hot dry seasons with low food availability and cold moist seasons with high food availability, and found residual RMR increased with increasing levels of food availability.
Abstract: Resting metabolic rate (RMR) influences energy allocation to survival, growth, and reproduction, and significant seasonal changes in RMR have been reported According to one hypothesis, seasonal changes in RMR are mainly attributable to seasonal changes in ambient temperature (Ta) and food availability Studies on species from the temperate zone indicated that food availability is the main driver However, whether this is generally true is unknown, because studies from the tropics and subtropics, where most species live, are rare We studied the African striped mouse (Rhabdomys pumilio) inhabiting a seasonal environment with hot dry seasons with low food availability and cold moist seasons with high food availability Using 603 RMR measurements of 277 individuals, we investigated the relative importance of food availability and Ta on RMR during selected periods, in which one extrinsic factor varied while the other factor was relatively constant At similar Ta, residual RMR increased with increasing levels of food availability In contrast, different Ta did not influence residual RMR at similar levels of food availability Thus, our study on a subtropical species gives support to the hypothesis, derived from temperate zone species, that food availability mainly drives seasonal changes in RMR
TL;DR: Sprint performance of striped bass is reduced under Hypoxia, is phenotypically plastic, and improves with repetitive hypoxia exposures but is unrelated to relative sprint performance under normoxia.
Abstract: Annual hypoxia in the Chesapeake Bay has expanded to the point where Darwinian fitness of juvenile striped bass (Morone saxatilis) may depend on their ability to perform in low-oxygen environments. The locomotion they use in predator/prey dynamics relies primarily on white (type II) muscle that is powered by anaerobic metabolic pathways and has generally been thought to be immune to aquatic hypoxia. We tested the sprint performance of 15 juvenile striped bass twice under acute hypoxia (20% air saturation [AS]) 5 wk apart and once under normoxia (>85% AS) in between. Average sprint performance was lower under the first hypoxia exposure than in normoxia and increased in the second hypoxia test relative to the first. The rank order of individual sprint performance was significantly repeatable when comparing the two hypoxia tests but not when compared with sprint performance measured under normoxic conditions. The maximum sprint performance of each individual was also significantly repeatable within a...
TL;DR: It is proposed that growth rates are subject to stabilizing selection balancing the benefits of fast development and the competing need of buffering its damaging effects to macromolecules and tissues.
Abstract: In Chernobyl, chronic exposure to radioactive contaminants has a variety of deleterious effects on exposed organisms, including genetic damage and mutation accumulation. However, the potential for such effects to be transmitted to the next generation is poorly understood. We captured lesser marsh grasshoppers (Chorthippus albomarginatus) in the Chernobyl Exclusion Zone from sites varying in levels of environmental radiation by more than three orders of magnitude. We then raised their offspring in a common garden experiment in order to assess the effects of parental exposure to radiation on offspring development and DNA damage. Offspring that reached maturity at a younger age had higher levels of DNA damage. Contrary to our hypothesis, parental exposure to radioactive contamination did not affect DNA damage in their offspring possibly because of intervening adaptation or parental compensatory mechanisms. Our results suggest a trade-off between developmental rate and resistance to DNA damage, whereb...
TL;DR: It is demonstrated that nonmigratory populations of alewife have evolved reduced swimming performance in parallel, compared with their migratory ancestor, and suggests that elimination of long-distance migration from the life cycle has shaped performance more than changes in body shape and physiological regulatory capacity.
Abstract: Whole-organism performance tasks are accomplished by the integration of morphological traits and physiological functions Understanding how evolutionary change in morphology and physiology influences whole-organism performance will yield insight into the factors that shape its own evolution We demonstrate that nonmigratory populations of alewife (Alosa pseudoharengus) have evolved reduced swimming performance in parallel, compared with their migratory ancestor In contrast to theoretically and empirically based predictions, poor swimming among nonmigratory populations is unrelated to the evolution of osmoregulation and occurs despite the fact that nonmigratory alewives have a more fusiform (torpedo-like) body shape than their ancestor Our results suggest that elimination of long-distance migration from the life cycle has shaped performance more than changes in body shape and physiological regulatory capacity
TL;DR: The results suggest that some aspects of respiratory and metabolic physiology (such as the propensity to use anaerobic metabolism but not others) underpin some variation in social behavior under environmental stress.
Abstract: Animals are bombarded with information about their environment and must select and interpret the relevant cues to make behavioral adjustments critical to survival. How animals integrate and...
TL;DR: It was found that above-water exposure duration, shark total length, and air temperature on the day of capture significantly influenced body surface temperatures of the analyzed sharks; however, thermal profiles of immature sharks (<140 cm) were significantly warmer than those of mature sharks.
Abstract: Fish physiology is significantly affected by temperature variability. During fisheries interactions, fish are often exposed to air and subjected to rapid temperature changes. Fish thermal d...
TL;DR: The observed decrease in plasma leptin levels may be necessary to allow for the observed seasonal decrease in BMR, with the similar cortisol pattern important for leptin regulation.
Abstract: In response to seasonal variation in energy availability and thermal environment, physiological and endocrine mechanisms have evolved in temperate zone animals. Seasonal changes in hormone activity affect metabolism, body temperature, and reproductive activity. We examined the seasonal regulatory role of hormones on basal metabolic rate (BMR) and regulatory nonshivering thermogenesis (RNST) in 98 female and 17 male adult Eptesicus fuscus (big brown bat). We measured BMR, RNST, and plasma levels of thyroid hormone (T3), leptin, and cortisol in bats captured in maternity colonies in eastern Massachusetts from May to August (from arousal from the hibernation phase to the prehibernation phase). We hypothesized that all three hormones are seasonally primarily metabolic hormones and secondarily thermogenic hormones. In males, only BMR significantly changed seasonally. In females, all five variables significantly changed seasonally. The seasonal pattern of plasma leptin and cortisol levels correlated with the seasonal pattern of BMR, with an initial increase followed by a decrease, suggesting that leptin and cortisol are primarily metabolic hormones. The seasonal pattern of plasma T3 levels generally paralleled the basic seasonal pattern of RNST, with both increasing at the second half of the season, suggesting that T3 is primarily a thermogenic hormone. The observed decrease in plasma leptin levels may be necessary to allow for the observed seasonal decrease in BMR, with the similar cortisol pattern important for leptin regulation. While T3 is needed to maintain BMR, it may play a more critical role in the seasonal regulation of RNST than of BMR.
TL;DR: The results suggest that parasites are relying on chemical cues not only for host finding but also to discriminate between hosts on the basis of the rate of respiration, with potentially important implications for the metabolic theory of ecology.
Abstract: Host bioenergetics and energy fluxes can be applied to measure the ecological and physiological effects of parasitism. By measuring changes in host metabolic rate, one can estimate the phys...
TL;DR: Age class effects: cubs were more susceptible to oxidative stress and oxidative damage than adults, especially very young cubs in the spring, when they also exhibited lower antioxidant biomarkers than adults and modelers against projected climate change scenarios predicted greater future risks of oxidative damage, although not necessarily exceeding antioxidant capacity.
Abstract: Wild-living animals are subject to weather variability that may cause the generation of reactive oxygen species, resulting in oxidative stress and tissue damage, potentially driving demographic responses. Our 3-yr field study investigated the effects of seasonal weather conditions on biomarkers for oxidative stress, oxidative damage, and antioxidant defense in the European badger (Meles meles). We found age class effects: cubs were more susceptible to oxidative stress and oxidative damage than adults, especially very young cubs in the spring, when they also exhibited lower antioxidant biomarkers than adults. Although previous studies have found that intermediate spring and summer rainfall and warmer temperatures favor cub survival, counterintuitively these conditions were associated with more severe oxidative damage. Oxidative damage was high in cubs even when antioxidant biomarkers were high. In contrast, adult responses accorded with previous survival analyses. Wetter spring and summer conditions were associated with higher oxidative damage, but they were also associated with higher antioxidant biomarkers. Autumnal weather did not vary substantially from normative values, and thus effects were muted. Winter carryover effects were partially evident, with drier and milder conditions associated with greater oxidative damage in the following spring but also with higher antioxidant capacity. Plausibly, warmer conditions promoted more badger activity, with associated metabolic costs at a time of year when food supply is limited. Modeling biomarkers against projected climate change scenarios predicted greater future risks of oxidative damage, although not necessarily exceeding antioxidant capacity. This interdisciplinary approach demonstrates that individual adaptive physiological responses are associated with variation in natural environmental conditions.
TL;DR: A better understanding of the evolution of bile salts and the FXR may expand the knowledge of their function in health and disease, including their function outside the gastrointestinal tract, and aid in the development of new strategies for treatment.
Abstract: In recent decades, our knowledge of bile salts has undergone a vast development, and bile salts are now known not only for their detergent properties that aid in the absorption of dietary lipids but also for their interaction with specific nuclear and membrane receptors. In particular, it has been realized that the response of the farnesoid X receptor (FXR) to bile acids provides a signal bridge between the liver and small intestine, controlling the intracellular levels, biosynthesis, and enterohepatic circulation of bile acids. Therefore, FXR and bile acid signaling has become an attractive target for treatment of, for example, cholestatic liver diseases, diabetes, and colorectal cancer. Previously, interest in the structure and chemistry of bile salts has focused on their cellular toxicity and involvement in digestion. However, insight into the extensive variation in the structure of bile salts in vertebrates and the concurrent evolution of the FXR has become increasingly important as their role as signal molecules has become clearer. In this review, we therefore focus on common structural features of bile salts as well as evolutionary aspects of bile salts and the FXR in vertebrates. Ultimately, a better understanding of the evolution of bile salts and the FXR may expand our knowledge of their function in health and disease, including their function outside the gastrointestinal tract, and aid in the development of new strategies for treatment.
TL;DR: The results suggest that endurance capacity may have a permissive effect on home range size, and individuals with larger home ranges may experience training effects (phenotypic plasticity) that increase their endurance.
Abstract: Among species of lizards, endurance capacity measured on a motorized treadmill is positively related to daily movement distance and time spent moving, but few studies have addressed such relationships at the level of individual variation within a sex and age category in a single population. Both endurance capacity and home range size show substantial individual variation in lizards, rendering them suitable for such studies. We predicted that these traits would be positively related because endurance capacity is one of the factors that has the potential to limit home range size. We measured the endurance capacity and home range size of adult male desert iguanas (Dipsosaurus dorsalis). Lizards were field captured for measurements of endurance, and home range data were gathered using visual identification of previously marked individuals. Endurance was significantly repeatable between replicate trials, conducted 1-17 d apart ([Formula: see text] for log-transformed values, [Formula: see text], [Formula: see text]). The log of the higher of two endurance trials was positively but not significantly related to log body mass. The log of home range area was positively but not significantly related to log body mass, the number of sightings, or the time span from first to last sighting. As predicted, log endurance was positively correlated with log home range area ([Formula: see text], [Formula: see text], one-tailed [Formula: see text]; for body-mass residual endurance values: [Formula: see text], one-tailed [Formula: see text]). These results suggest that endurance capacity may have a permissive effect on home range size. Alternatively, individuals with larger home ranges may experience training effects (phenotypic plasticity) that increase their endurance.
TL;DR: It is found that body mass–adjusted BMR was positively correlated with mb- and Tb-adjusted TMRmin, in a phylogenetically corrected analysis, suggesting an increase in BMR during the evolution of endothermy in homeothermic animals, which leads to the loss of their ability to enter torpor.
Abstract: The evolution of endothermic thermoregulation is rooted in the processes involving high metabolism, which allows the maintenance of high and stable body temperatures (Tb). In turn, selectio...
TL;DR: Both lower temperature and food restriction delayed regression, as if thePhotoperiod was shorter than it actually was, and both resulted in daily cycles in body temperature that reflected cycles under shorter photoperiods, implying that the daily cycle in bodyTemperature is possibly a common pathway through which nonphotoperiodic cues may operate.
Abstract: Photoperiodic control of reproduction in birds is based on two processes, a positive effect leading to gonadal maturation and an inhibitory effect subsequently inducing regression. Nonphoto...
TL;DR: There are sex differences in how incubation temperature alters organ mass and yolk energy reserve; this can lead to a difference in survival at different incubation temperatures between the sexes.
Abstract: In oviparous species, the embryonic environment—particularly temperature—can alter phenotype and survival of an individual by affecting its size as well as its metabolic rate. Previous stud...