Respiratory water loss: A predictive model

Welch, William R.; Tracy, C. Richard

doi:10.1016/0022-5193(77)90324-1

Cited by 17 publications

(11 citation statements)

References 17 publications

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“…For example, perhaps the sizes of RSA and RBT are the result of a tradeoff between maximizing gas exchange and minimizing respiratory water (or ion) loss (79). Respiratory water loss may constitute a significant fraction of total water loss among vertebrates (80), and it seems from our data that species facing greater challenges with respect to water loss (e.g., desert tortoises, lungfish, and salamanders) have relatively small respiratory surface areas and/or relatively thick respiratory barriers. A closer look at diffusion in this way may prove valuable to answering the long-standing question of why oxygen consumption rate, and thus species' energy use (i.e., metabolic rate), scales with body mass.…”

Section: Discussionmentioning

confidence: 99%

Body mass scaling of passive oxygen diffusion in endotherms and ectotherms

Gillooly

Gómez

Mavrodiev

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The area and thickness of respiratory surfaces, and the constraints they impose on passive oxygen diffusion, have been linked to differences in oxygen consumption rates and/or aerobic activity levels in vertebrates. However, it remains unclear how respiratory surfaces and associated diffusion rates vary with body mass across vertebrates, particularly in relation to the body mass scaling of oxygen consumption rates. Here we address these issues by first quantifying the body mass dependence of respiratory surface area and respiratory barrier thickness for a diversity of endotherms (birds and mammals) and ectotherms (fishes, amphibians, and reptiles). Based on these findings, we then use Fick's law to predict the body mass scaling of oxygen diffusion for each group. Finally, we compare the predicted body mass dependence of oxygen diffusion to that of oxygen consumption in endotherms and ectotherms. We find that the slopes and intercepts of the relationships describing the body mass dependence of passive oxygen diffusion in these two groups are statistically indistinguishable from those describing the body mass dependence of oxygen consumption. Thus, the area and thickness of respiratory surfaces combine to match oxygen diffusion capacity to oxygen consumption rates in both air-and water-breathing vertebrates. In particular, the substantially lower oxygen consumption rates of ectotherms of a given body mass relative to those of endotherms correspond to differences in oxygen diffusion capacity. These results provide insights into the long-standing effort to understand the structural attributes of organisms that underlie the body mass scaling of oxygen consumption.allometry | metabolic theory | respiration rate | metabolism | oxygen consumption S ince the classic debates of Krogh and Bohr (1), the relationship of passive oxygen diffusion to oxygen consumption has remained the focus of considerable research (2). Still, we have much to learn about how oxygen diffusion across respiratory surfaces relates to whole-organism oxygen consumption (3). In particular, we have much to learn about how the structural constraints on oxygen diffusion capacity, namely the thickness and area of respiratory surfaces, relate to the body mass scaling of oxygen consumption in vertebrates-a pattern that reflects the scaling of species' energy use (3).Studies on the body mass dependence of oxygen diffusion have been undertaken over the last century in all major classes of vertebrates, typically using respiratory surface area as a metric of diffusion capacity (2, 3). Less commonly, studies have also considered potentially relevant changes in respiratory barrier thickness with mass (4). In many cases, these studies have concluded that the body mass scaling of oxygen diffusion relative to that of oxygen consumption differs between endotherms and ectotherms (3,5,6). This has led to very different conclusions regarding the structure and function of respiratory systems among classes of vertebrates, as explained below.Among endotherms, particularly...

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Section: Discussionmentioning

confidence: 99%

Body mass scaling of passive oxygen diffusion in endotherms and ectotherms

Gillooly

Gómez

Mavrodiev

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…In insects that use both convective and diffusive exchange (14), fluxes occur through spiracles, which are short tubes much like those used by plant leaves and bird eggshells. Models for the uptake of gases (oxygen for animals and carbon dioxide for plants) and the loss of water vapor have been developed for all five groups (14)(15)(16)(17)(18)(19)(20)(21). Here, we show that the models are all specific statements of an underlying general model and that a common expression for respiratory water lost per unit of gas taken up can be readily developed.…”

Section: Model Of Gas Uptake and Water Lossmentioning

confidence: 90%

“…If we ignore the variation in inspired and expired volumes arising from the variation in the respiratory quotient and the water vapor added in the lungs (18)…”

Section: Model Of Gas Uptake and Water Lossmentioning

confidence: 99%

“…Because system physical structures are identical with respect to metabolic gases (CO 2 and O 2 ) and water vapor, the physical dimensions (crosssectional area, A, and length, L) in τ cancel and therefore, disappear from the model. This simple vapor-gas relationship has been developed explicitly in the plant literature (20) and in models of respiratory water loss in vertebrates (18) and insects (14), but it has never been expressed in a general form like the one expressed here. Eq.…”

Section: Model Of Gas Uptake and Water Lossmentioning

confidence: 99%

“…The diversity of gas-exchange systems among taxa has spawned a large set of models for predicting respiratory and stomatal water losses (14)(15)(16)(17)(18)(19)(20)(21). Although the models are all quite similar, they have failed to provide unification and generality as a group, because each uses different terminology and is built on taxonspecific details.…”

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Universal model for water costs of gas exchange by animals and plants

Woods

Smith

2010

Proc. Natl. Acad. Sci. U.S.A.

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For terrestrial animals and plants, a fundamental cost of living is water vapor lost to the atmosphere during exchange of metabolic gases. Here, by bringing together previously developed models for specific taxa, we integrate properties common to all terrestrial gas exchangers into a universal model of water loss. The model predicts that water loss scales to gas exchange with an exponent of 1 and that the amount of water lost per unit of gas exchanged depends on several factors: the surface temperature of the respiratory system near the outside of the organism, the gas consumed (oxygen or carbon dioxide), the steepness of the gradients for gas and vapor, and the transport mode (convective or diffusive). Model predictions were largely confirmed by data on 202 species in five taxa-insects, birds, bird eggs, mammals, and plants-spanning nine orders of magnitude in rate of gas exchange. Discrepancies between model predictions and data seemed to arise from biologically interesting violations of model assumptions, which emphasizes how poorly we understand gas exchange in some taxa. The universal model provides a unified conceptual framework for analyzing exchangeassociated water losses across taxa with radically different metabolic and exchange systems.ll terrestrial animals and plants exchange O 2 and CO 2 with the atmosphere and thereby incur costs in the currency of water vapor (1-4). The inevitability of water loss stems from universal characteristics of terrestriality-(i) adequate gas exchange requires large surface areas of high-conductance tissues, usually invaginated; (ii) high-conductance tissues saturate internal exchange spaces with water vapor; and (iii) those surfaces must be ventilated by the atmosphere, at least intermittently. Consequently, water vapor tends to escape into surrounding drier air. Terrestrial organisms-here defined to include air-breathing marine mammals-thus face a gas-water tradeoff in which higher rates of gas exchange give higher rates of water loss. For individual organisms, this tradeoff shapes patterns of ventilation and behavior. For populations and species, the tradeoff influences diverse phenomena, including the evolution of hibernation, dormancy, and diapause (5-8), the evolution of nasal physiology in vertebrate homeotherms (9-11), and the evolution and ecology of plants with different modes of carbon fixation (C3, C4, and CAM) (12). In general, the severity of the tradeoff for any species will depend on the fraction of total water lost through the gas-exchange system, which in turn is related to the temperature and aridity of its habitat (13).The diversity of gas-exchange systems among taxa has spawned a large set of models for predicting respiratory and stomatal water losses (14-21). Although the models are all quite similar, they have failed to provide unification and generality as a group, because each uses different terminology and is built on taxonspecific details. Broader conceptualization of the problem may give insight into how diverse organisms function across biome...

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Physiological Ecology and Behavior of Desert Birds

Williams

Tieleman

2001

Current Ornithology, Volume 16

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Respiratory water loss: A predictive model

Cited by 17 publications

References 17 publications

Body mass scaling of passive oxygen diffusion in endotherms and ectotherms

Body mass scaling of passive oxygen diffusion in endotherms and ectotherms

Universal model for water costs of gas exchange by animals and plants

Physiological Ecology and Behavior of Desert Birds

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