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Research Interests: Physiology, Biology, Ecology, Chile, Medicine, and 15 moreComparative, Seasonality, Energetics, Animals, Passerines, Physiological Response, Natural Environment, Environmental Conditions, Analysis of Variance, Acclimatization, Seasons, Cold Acclimation, Oxygen Consumption, Biochemistry and cell biology, and Basal Metabolism
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Research Interests: Geography, Ecology, Medicine, Multidisciplinary, Foraging, and 8 morePredation, Pellet, Isotope, Food Resources, Niche, Scavengers, Latitude, and anthropization
Bird species exhibit great diversity in digestive tract morphology and enzymatic activity that is partly correlated with the chemical composition of their natural diets. However, no studies have assessed whether the activities of... more
Bird species exhibit great diversity in digestive tract morphology and enzymatic activity that is partly correlated with the chemical composition of their natural diets. However, no studies have assessed whether the activities of digestive enzymes of the enterocytes correlate with dietary chemical composition data analyzed as a continuous variable at an evolutionary scale. We used a phylogenetically explicit approach to examine the effect of diet on the hydrolytic activity of three digestive enzymes (maltase, sucrase, and aminopeptidase-N) in 16 species of songbirds (Order Passeriformes) from Central Chile. The total activities (lmol/min) of these enzymes were posi-tively associated with body mass using both conventional least squares regressions and phylogenetically independent contrasts. After removing mass effects, we found a sig-nificant negative correlation between the ratio of amino-peptidase-N and maltase to the proportion of seeds found in the gizzard, but this relationship ...
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Tracing how free-ranging organisms interact with their environment to maintain water balance is a difficult topic to study for logistical and methodological reasons. We use a novel combination of triple-oxygen stable isotope analyses of... more
Tracing how free-ranging organisms interact with their environment to maintain water balance is a difficult topic to study for logistical and methodological reasons. We use a novel combination of triple-oxygen stable isotope analyses of water extracted from plasma (δ16O, δ17O, δ18O) and bulk tissue carbon (δ13C) and nitrogen (δ15N) isotopes of feathers and blood to estimate the proportional contribution of marine resources, seawater, and metabolic water used by two species of unique songbirds (genus Cinclodes) to maintain their water balance in a seasonal coastal environment. We also assessed the physiological adjustments that these birds use to maintain their water balance. In agreement with previous work on these species, δ13C and δ15N data show that the coastal resident and invertivore C. nigrofumosus consumes a diet rich in marine resources, while the diet of migratory C. oustaleti shifts seasonally between marine (winter) to freshwater aquatic resources (summer). Triple-oxygen ...
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Understanding physiological traits and ecological conditions that influence a species reliance on metabolic water is critical to creating accurate physiological models that can assess their ability to adapt to environmental perturbations... more
Understanding physiological traits and ecological conditions that influence a species reliance on metabolic water is critical to creating accurate physiological models that can assess their ability to adapt to environmental perturbations (e.g., drought) that impact water availability. However, relatively few studies have examined variation in the sources of water animals use to maintain water balance, and even fewer have focused on the role of metabolic water. A key reason is methodological limitations. Here, we applied a new method that measures the triple oxygen isotopic composition of a single blood sample to estimate the contribution of metabolic water to the body water pool of three passerine species. This approach relies on Δ\u2717O, defined as the residual from the tight linear correlation that naturally exists between δ17O and δ18O values. Importantly, Δ\u2717O is relatively insensitive to key fractionation processes, such as Rayleigh distillation in the water cycle that hav...
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SEO/BirdLife (the Spanish Ornithological Society) and the Editorial Board of Ardeola express their gratitude to the following individuals for their help in the evaluation of manuscripts submitted to the journal: [SEO/BirdLife y el Comité... more
SEO/BirdLife (the Spanish Ornithological Society) and the Editorial Board of Ardeola express their gratitude to the following individuals for their help in the evaluation of manuscripts submitted to the journal: [SEO/BirdLife y el Comité Editorial de Ardeola expresan su agradecimiento a las siguientes personas por su ayuda en la evaluación de manuscritos enviados a la revista:] DOI: 10.13157/arla.61.2.2014.471
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Variations in the availability of nutritional resources in animals can trigger reversible adjustments, which in the short term are manifested as behavioral and physiological changes. Several of these responses are mediated by Sirt1, which... more
Variations in the availability of nutritional resources in animals can trigger reversible adjustments, which in the short term are manifested as behavioral and physiological changes. Several of these responses are mediated by Sirt1, which acts as an energy status sensor governing a global genetic program to cope with changes in nutritional status. Growing evidence suggests a key role of the response of the perinatal environment to caloric restriction in the setup of physiological responses in adulthood. The existence of adaptive predictive responses has been proposed, which suggests that early nutrition could establish metabolic capacities suitable for future food-scarce environments. We evaluated how perinatal food deprivation and maternal gestational weight gain impact the transcriptional, physiological, and behavioral responses in mice, when acclimated to caloric restriction in adulthood. Our results show a strong predictive capacity of maternal weight and gestational weight gain...
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In order to maintain the energy balance, animals often exhibit several physiological adjustments when subjected to a decrease in resource availability. Specifically, some rodents show increases in behavioral activity in response to food... more
In order to maintain the energy balance, animals often exhibit several physiological adjustments when subjected to a decrease in resource availability. Specifically, some rodents show increases in behavioral activity in response to food restriction; a response regarded as a paradox because it would imply an investment in locomotor activity, despite the lack of trophic resources. Here, we aim to explore the possible existence of trade-offs between metabolic variables and behavioral responses when rodents are faced to stochastic deprivation of food and caloric restriction. Adult BALB/c mice were acclimatized for four weeks to four food treatments: two caloric regimens (ad libitum and 60% restriction) and two periodicities (continuous and stochastic). In these mice, we analyzed: exploratory behavior and home-cage behavior, basal metabolic rate, citrate synthase and cytochrome oxidase c enzyme activity (in liver and skeletal muscle), body temperature and non-shivering thermogenesis. Our...
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Due to the higher energy requirements of birds during winter, it is predicted that the activities of metabolic enzymes (e.g., citrate synthase, CS and cytochrome C oxidase, COX) should increase in tandem with increases in rates of energy... more
Due to the higher energy requirements of birds during winter, it is predicted that the activities of metabolic enzymes (e.g., citrate synthase, CS and cytochrome C oxidase, COX) should increase in tandem with increases in rates of energy expenditure (e.g., basal metabolic rate, BMR). However, there is mixed support for the hypothesis of enzymatic acclimatization. Furthermore, there is little information about the effect of ambient temperature on energetics and tissue enzyme activity levels in passerines inhabiting seasonal Mediterranean environments. In this study we evaluated the interplay between BMR and enzyme activities of freshly caught individuals of the passerine Zonotrichia capensis in winter and summer in a Mediterranean environment from central Chile, and also in warm (30°C) and cold (15°C) lab-acclimated birds. The results revealed a lack of seasonal variation in BMR, thermal conductance and in the activity of CS and COX. However, we found higher BMR and lower thermal con...
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Phenotypic flexibility in metabolic rates allows organisms to reversibly adjust their energy flow to meet challenges imposed by a variable environment. In turn, the food habits hypothesis (FHH) predicts that species or populations adjust... more
Phenotypic flexibility in metabolic rates allows organisms to reversibly adjust their energy flow to meet challenges imposed by a variable environment. In turn, the food habits hypothesis (FHH) predicts that species or populations adjust their basal metabolic rate (BMR) according to the diet attributes such as food abundance or predictability. Desert ecosystems represent a temporally heterogeneous environment because of low rain pulse predictability, which is also associated with temporal variation in food resources. In the present study, we investigated the relationship between the magnitude of BMR flexibility in response to dietary acclimation and the inter-annual rainfall variability in three populations of rufous-collared sparrows. Specifically we addressed the question of whether birds from a desert environment are more flexible in BMR than those from non-desert habitats. We found a positive trend between BMR flexibility and the inter-annual rainfall variability. In fact, dieta...
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Predictions indicate that birds worldwide will be affected by global warming and extreme climatic events which is especially relevant for passerines because the diurnal habits, small body size, and high mass-adjusted metabolic rates of... more
Predictions indicate that birds worldwide will be affected by global warming and extreme climatic events which is especially relevant for passerines because the diurnal habits, small body size, and high mass-adjusted metabolic rates of this group make it particularly susceptible to increases in temperature and aridity. Some bird species respond to conditions that stress osmoregulation by increasing their rates of energy expenditure, nevertheless, the effect of dehydration on metabolic rates in birds has produced contrasting results. It also remains unknown whether hydration state may cause shifts in tissue-specific metabolic rates or modify tissue oxidative status. We used the rufous-collared sparrow (Zonotrichia capensis), to experimentally test the effect of dehydration on metabolic enzymes in erythrocytes, tissue oxidative status, basal metabolic rate (BMR), and total evaporative water loss. We found a significant increase in mass-adjusted BMR in water restricted (WR) birds compa...
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of the oxygen diffusing capacity of the Picui Ground Gove (Columbina picui) with other doves of Chile. Int. J. Morphol., 28(1):127-133, 2010. SUMMARY: We studied the respiratory surface density and the thickness of the air-blood barrier... more
of the oxygen diffusing capacity of the Picui Ground Gove (Columbina picui) with other doves of Chile. Int. J. Morphol., 28(1):127-133, 2010. SUMMARY: We studied the respiratory surface density and the thickness of the air-blood barrier in the Picui Ground Dove (Columbina picui), and compared it with Eared Dove (Zenaida auriculata) and Blacked-winged Ground Dove (Metropelia melanoptera), two larger species. As expected, Columbina picui BMR and VO 2 max showed higher values than those of the larger species according to the expected for their body size. The respiratory surface density and the thickness of the blood-air barrier were not different among the different species of doves. However C. picui showed an anatomical diffusion factor lower than M. melanoptera and Z. auriculata. Picui Ground Dove had low values of oxygen diffusion capacity, such as cursorial birds. A differential oxygen partial pressure of 7.5 Kpa, an usual value at sea level, it can hardly meet their maximal energy...
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During the past 60 years, mammalian hibernation (i.e., seasonal torpor) has been interpreted as a physiological adaptation for energy economy. However, direct field comparisons of energy expenditure and torpor use in hibernating and... more
During the past 60 years, mammalian hibernation (i.e., seasonal torpor) has been interpreted as a physiological adaptation for energy economy. However, direct field comparisons of energy expenditure and torpor use in hibernating and active free-ranging animals are scarce. Here, we followed the complete hibernation cycle of a fat-storing hibernator, the marsupial Dromiciops gliroides, in its natural habitat. Using replicated mesocosms, we experimentally manipulated energy availability and measured torpor use, hibernacula use, and social clustering throughout the entire hibernation season. Also, we measured energy flow using daily food intake, daily energy expenditure (DEE), and basal metabolic rate (BMR) in winter. We hypothesized that when fac- ing chronic caloric restriction (CCR), a hibernator should maxi- mize torpor frequency to compensate for the energetic deficit, compared with individuals fed ad lib. (controls). However, being torpid at low temperatures could increase other burdens (e.g., cost of rewarming, freezing risks). Our results revealed that CCR animals, compared with control animals, did not promote heat conservation strategies (i.e., clustering and hibernacula use). In- stead, they gradually increased torpor frequency and reduced DEE and, as a consequence, recovered weight at the end of the sea- son. Also, CCR animals consumed food at a rate of 50.8 kJ d21, whereas control animals consumed food at a rate of 98.4 kJ d21. Similarly, the DEE of CCR animals in winter was 47:3 5 5:64 kJ d21, which was significantly lower than control animals (DEE p 88:0 5 5:84 kJ d21). However, BMR and lean mass of CCR and control animals did not vary significantly, suggesting that animals maintained full metabolic capacities. This study shows that the use of torpor can be modulated depending on energy supply, thus optimizing energy budgeting. This plasticity in the use of het- erothermy as an energy-saving strategy would explain the oc- currence of this marsupial in a broad latitudinal and altitudinal range. Overall, this study suggests that hibernation is a powerful strategy to modulate energy expenditure in mammals from tem- perate regions.
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Variations in the availability of nutritional resources in animals can trigger reversible adjustments, which in the short term are manifested as behavioral and physiological changes. Several of these responses are mediated by Sirt1, which... more
Variations in the availability of nutritional resources in animals can trigger reversible adjustments, which in the short term are manifested as behavioral and physiological changes. Several of these responses are mediated by Sirt1, which acts as an energy status sensor governing a global genetic program to cope with changes in nutritional status. Growing evidence suggests a key role of the response of the perinatal environment to caloric restriction in the setup of physiological responses in adulthood. The existence of adaptive predictive responses has been proposed, which suggests that early nutrition could establish metabolic capacities suitable for future food-scarce environments. We evaluated how perinatal food deprivation and maternal gestational weight gain impact the transcriptional, physiological, and behavioral responses in mice, when acclimated to caloric restriction in adulthood. Our results show a strong predictive capacity of maternal weight and gestational weight gain, in the expression of Sirt1 and its downstream targets in the brain and liver, mitochondrial enzymatic activity in skeletal muscle, and exploratory behavior in offspring. We also observed differential responses of both lactation and gestational food restriction on gene expression, thermogenesis, organ masses, and behavior, in response to adult caloric restriction. We conclude that the early nutritional state could determine the magnitude of responses to food scarcity later in adulthood, mediated by the pivotal metabolic sensor Sirt1. Our results suggest that maternal gestational weight gain could be an important life history trait and could be used to predict features that improve the invasive capacity or adjustment to seasonal food scarcity of the offspring.
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Understanding physiological traits and ecological conditions that influence a species reliance on metabolic water is critical to creating accurate physiological models that can assess their ability to adapt to environmental perturbations... more
Understanding physiological traits and ecological conditions that influence a species reliance on metabolic water is critical to creating accurate physiological models that can assess their ability to adapt to environmental perturbations (e.g., drought) that impact water availability. However, relatively few studies have examined variation in the sources of water animals use to maintain water balance, and even fewer have focused on the role of metabolic water. A key reason is methodological limitations. Here, we applied a new method that measures the triple oxygen isotopic composition of a single blood sample to estimate the contribution of metabolic water to the body water pool of three passerine species. This approach relies on Δ'17O, defined as the residual from the tight linear correlation that naturally exists between δ17O and δ18O values. Importantly, Δ'17O is relatively insensitive to key fractionation processes, such as Rayleigh distillation in the water cycle that h...
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During the last sixty years, mammalian hibernation (i.e., seasonal torpor) has been interpreted as a physiological adaptation for energy economy. However -and crucially for validating this idea – direct field comparisons of energy... more
During the last sixty years, mammalian hibernation (i.e., seasonal torpor) has been interpreted as a physiological adaptation for energy economy. However -and crucially for validating this idea – direct field comparisons of energy expenditure in hibernating and active free-ranging animals are scarce. Using replicated mesocosms and a combination of energy budgeting approaches (i.e., doubly labelled water, rates of CO2 production and food intake), we experimentally manipulated energy availability and quantified net energy costs of hibernation in a marsupial. We hypothesized that, when facing chronic caloric restriction (CCR), a hibernator should maximize torpor use for compensating the energetic deficit, compared to ad libitum fed individuals (=controls). However, intensifying torpor duration at low temperatures could increase other burdens (e.g., cost of rewarming, freezing risk). In order to explore this trade-off, we followed the complete hibernation cycle of the relict marsupial D...
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Specific fatty acids (FA) such as unsaturated (UFA) and saturated (SFA) fatty acids contained in foods are key factors in the nutritional ecology of birds. By means of a field and experimental approach, we evaluated the effect of diet on... more
Specific fatty acids (FA) such as unsaturated (UFA) and saturated (SFA) fatty acids contained in foods are key factors in the nutritional ecology of birds. By means of a field and experimental approach, we evaluated the effect of diet on the activity of three esterases involved in FA hydrolysis; carboxylesterase (CE: 4-NPA-CE and a-NA-CE) and butyrylcholinesterase, in two South American passerines: the omnivorous rufous-collared sparrow (Zonotrichia capensis) and the granivorous common diuca-finch (Diuca diuca). The activity of the three esterases was measured in the intestines of freshly caught individuals over two distinct seasons and also after a chronic intake of a UFA-rich or SFA-rich diet in the laboratory. In turn, we assessed the feeding responses of the birds choosing amongst diets contrasting in the kind of specific FA (UFA- vs. SFA-treated diets). During summer, field CE activities (4-NPA-CE and a-NA-CE) in the small intestine were higher in the rufous-collared sparrow (25.3 ± 3.3 and 81.4 ± 10.8 µmol min(-1) g tissue(-1), respectively) than in the common diuca-finch (10.0 ± 3.0 and 33.9 ± 13.1 µmol min(-1) g tissue(-1), respectively). Two hour feeding trial test indicated that both species exhibited a clear preference for UFA-treated diets. On average, the rufous-collared sparrow consumed 0.46 g 2 h(-1) of UFA-rich diets and 0.12 g 2 h(-1) of SFA-rich diets. In turn, the consumption pattern of the common diuca-finch averaged 0.73 and 0.16 g 2 h(-1) for UFA-rich and SFA-rich diets, respectively. After a month of dietary acclimation to UFA-rich and SFA-rich diets, both species maintained body mass irrespective of the dietary regime. Additionally, the intestinal 4-NPA-CE activity exhibited by birds fed on a UFA-rich or SFA-rich diet was higher in the rufous-collared sparrow (39.0 ± 5.3 and 44.2 ± 7.3 µmol min(-1) g tissue(-1), respectively) than in the common diuca-finch (13.3 ± 1.9 and 11.2 ± 1.4 µmol min(-1) g tissue(-1), respectively). Finally, the intestinal a-NA-CE activity exhibited by the rufous-collared sparrow was about two times higher when consuming an UFA-rich diet. Our results suggest that the rufus-collared sparrow exhibits a greater capacity for intestinal FA hydrolysis, which would allow it to better deal with fats from different sources.
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Seed-eating birds have a diet of high nutritional value; however, they must cope with plant secondary metabolites (PSM). We postulated that the detoxification capacity of birds is associated with a metabolic cost, given that the organs... more
Seed-eating birds have a diet of high nutritional value; however, they must cope with plant secondary metabolites (PSM). We postulated that the detoxification capacity of birds is associated with a metabolic cost, given that the organs responsible for detoxification significantly contribute to energetic metabolism. We used an experimental approach to assess the effects of phenol-enriched diets on two passerines with different feeding habits: the omnivorous rufous-collared sparrow (Zonotrichia capensis) and the granivorous common diuca-finch (Diuca diuca). The birds were fed with one of three diets: control diet, supplemented with tannic acid, or supplemented with Opuntia ficus-indica phenolic extract (a common food of the sparrow but not the finch). After 5 weeks of exposure to the diets, we measured basal metabolic rates (BMR), energy intake, glucuronic acid output and digestive and kidney structure. In both species, detoxification capacity expressed as glucuronic acid output was h...
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Effects of pesticides on non-target organisms have been studied in several taxa at different levels of biological organization, from enzymatic to behavioral responses. Although the physiological responses may be associated with higher... more
Effects of pesticides on non-target organisms have been studied in several taxa at different levels of biological organization, from enzymatic to behavioral responses. Although the physiological responses may be associated with higher energy costs, little is known about metabolic costs of pesticide detoxification in birds. To fill this gap, we exposed orally (diet) 15-d old Coturnix coturnix japonica individuals to sublethal doses of chlorpyrifos (10 and 20 mg active ingredient/kg dry food) for four weeks. Carboxylesterase (CbE), butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) activities were periodically measured in multiple tissues along with measurements of resting (RMR) and maximum metabolic rates (Msum). Furthermore, glucuronic acid in bird excreta was also assessed at the end of the trial. While CbE and BChE activities were inhibited by chlorpyrifos in all tissues during the third and fourth weeks following pesticide treatment, AChE activity was unaffected. At thi...
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Inhibition of blood esterase activities by organophosphate (OP) pesticides has been used as a sensitive biomarker in birds. Furthermore, compared to mammalian vertebrates, less is known about the role of these enzyme activities in the... more
Inhibition of blood esterase activities by organophosphate (OP) pesticides has been used as a sensitive biomarker in birds. Furthermore, compared to mammalian vertebrates, less is known about the role of these enzyme activities in the digestive tracts of non-mammalian vertebrates, as well as the environmental and biological stressors that contribute to their natural variation. To fill this gap, we examined butyrylcholinesterase (BChE) and carboxylesterases (CbE) in the digestive tracts of sixteen passerine species from central Chile. Whole intestine enzyme activities were positively and significantly correlated with body mass. After correcting for body mass and phylogenetic effect, we found only a marginal effect of dietary category on BChE activity, but a positive and significant association between the percentage of dietary nitrogen and the mass-corrected lipase activity. Our results suggest that observed differences may be due to the dietary composition in the case of lipases and BChE, and also we predict that all model species belonging to the same order will probably respond differently to pesticide exposure, in light of differences in the activity levels of esterase activities.
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ABSTRACT Background: Among the predictions of the effect of future climate change, the impact of thermal conditions at local levels on the physiological performance of individuals and their acclimation capacities is key to understanding... more
ABSTRACT Background: Among the predictions of the effect of future climate change, the impact of thermal conditions at local levels on the physiological performance of individuals and their acclimation capacities is key to understanding animals’ responses to global warming. Goal: Test for the effect of acclimation to environmental thermal variability, namely 24 ± 0�C, 24 ± 4�C, and 24 ± 8�C, on the metabolic performance curve in the mealworm beetle Tenebrio molitor. Results: Maximum resting metabolism and metabolic breadth were significantly different, but optimal temperature was similar, between treatments. Thus, increases in ambient thermal variability caused a reduction in maximum performance at each level of acclimation, with a decrease of almost 50% between the nil variability and ± 8�C daily variability treatments. Conclusions: If thermal variability changes in any of the directions forecast by climatologists, ecologists will have to use mechanistic and modelling approaches based on physiological and biophysical traits to predict the biodiversity consequences of climate change.
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The potential for thermal acclimation in marsupials is controversial. Initial studies suggest that the thermoregulatory maximum metabolic rate (MMR) in metatherians cannot be changed by thermal acclimation. Nevertheless, recent studies... more
The potential for thermal acclimation in marsupials is controversial. Initial studies suggest that the thermoregulatory maximum metabolic rate (MMR) in metatherians cannot be changed by thermal acclimation. Nevertheless, recent studies reported conspicuous seasonality in both MMR and in basal metabolic rate (BMR). We studied the role of thermal acclimation in the Chilean mouse-opossum, Thylamys elegans, by measuring MMR and BMR before and after acclimation to cold or warm conditions. Following acclimation we also measured the mass of metabolically active organs, and the activity of a key digestive enzyme, aminopeptidase-N. No significant effect of thermal acclimation (i.e. between cold- and warm-acclimated animals) was observed for body mass, MMR, body temperature or factorial aerobic scope. However, the BMR of cold-acclimated animals was 30 % higher than for warm-acclimated individuals. For organ mass, acclimation had a significant effect on the dry mass of caecum, liver and kidney...
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The flexibility of digestive traits characterizes a standard model of physiological flexibility, demonstrating that animals adjust their digestive attributes in order to maximize overall energy return. Using an intraspecific experimental... more
The flexibility of digestive traits characterizes a standard model of physiological flexibility, demonstrating that animals adjust their digestive attributes in order to maximize overall energy return. Using an intraspecific experimental study, we evaluated the amount of flexibility in digestive tract mass and length in individuals from field mouse populations inhabiting semi-arid and temperate rain forest habitats and acclimated for six months to diets of different qualities. In accordance with the predictions of the theory of digestion, we observed a highly significant relationship between dietary variability and digestive flexibility in both specific digestive chambers and in the total digestive tract mass and length. Specifically, we found higher digestive plasticity in response to diet quality in rodents inhabiting southern temperate ecosystems with higher dietary variability in comparison to individuals from northern semi-arid habitats.
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ABSTRACT Birds living in desert environments have been the preferred models for the study of physiological adaptations to water scarcity. Passerine birds living in marine coastal habitats face similar problems, yet physiological... more
ABSTRACT Birds living in desert environments have been the preferred models for the study of physiological adaptations to water scarcity. Passerine birds living in marine coastal habitats face similar problems, yet physiological adaptations to water conservation in such species have been poorly documented. We measured total evaporative water loss (TEWL) and rates of oxygen consumption (VO2) in three species of passerine birds dwelling in marine and fresh water habitats. Mass specific total evaporative water loss was significantly lower in the marine species, Cinclodes nigrofumosus, than in species inhabiting areas near freshwater sources. We found a positive relationship between TEWL and VO2. The ratio of TEWL to VO2 (relative evaporative water loss, RTEWL) showed significant variation among Cinclodes species, and was highest for the fresh-water living species, C. oustaleti and C. fuscus. The variation in TEWL found in Cinclodes is likely a consequence of differential exploitation of marine prey with high osmotic loads, which, in turn, may impose the need for water conservation.