Scaling of standard metabolic rate in estuarine crocodiles Crocodylus porosus

Seymour, Roger S.; Gienger, C. M.; Brien, Matthew L.; Tracy, C. Richard; Manolis, S. Charlie; Webb, Grahame J. W.; Christian, Keith A.

doi:10.1007/s00360-012-0732-1

Cited by 27 publications

(20 citation statements)

References 51 publications

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“…Next, using the standard metabolic rate, of C. porosus , in mL/min, again with mass, m , in gram (Seymour et al. ):

SMR = 1.01 \times {((), \frac{m}{1000})}^{0.83}

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Section: Discussionmentioning

confidence: 99%

“…For Crocodyliformes, it has also been proposed that the need for increased diving capacity required larger sizes (Seymour et al 2004). Oxygen stores scale allometrically with body size with an exponent of ß0.9 (Wright and Kirshner 1987), whereas metabolic rate scales allometrically with body size with an exponent of ß0.8 (Seymour et al 2013). Therefore, the diving capacity of a crocodyliform scales allometrically with body size with an exponent of ß0.1, meaning larger species will have greater capacity to remain under water and dive for prey.…”

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confidence: 99%

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Physiological constraints on body size distributions in Crocodyliformes

Gearty

Payne

2020

Evolution

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At least 26 species of crocodylian populate the globe today, but this richness represents a minute fraction of the diversity and disparity of Crocodyliformes. Fossil forms are far more varied, spanning from erect, fully terrestrial species to flippered, fully marine species. To quantify the influence of a marine habitat on the directionality, rate, and variance of evolution of body size in Crocodyliformes and thereby identify underlying selective pressures, we compiled a database of body sizes for 264 fossil and modern species of crocodyliform covering terrestrial, semi‐aquatic, and marine habitats. We find increases in body size coupled with increases in strength of selection and decreases in variance following invasions of marine habitats but not of semiaquatic habitats. A model combining constraints from thermoregulation and lung capacity provides a physiological explanation for the larger minimum and average sizes of marine species. It appears that constraints on maximum size are shared across Crocodyliformes, perhaps through factors such as the allometric scaling of feeding rate versus basal metabolism with body size. These findings suggest that broad‐scale patterns of body size evolution and the shapes of body size distributions within higher taxa are often determined more by physiological constraints than by ecological interactions or environmental fluctuations.

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“…Next, using the standard metabolic rate, of C. porosus , in mL/min, again with mass, m , in gram (Seymour et al. ):

SMR = 1.01 \times {((), \frac{m}{1000})}^{0.83}

…”

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Physiological constraints on body size distributions in Crocodyliformes

Gearty

Payne

2020

Evolution

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“…In the morphological literature, three types are recognized: ontogenetic, static, and evolutionary (see, e.g., 62,313,371). Ontogenetic scaling considers growth trajectories of the relationship between Y and M for a single individual, although crosssectional comparisons of multiple individuals from the same species at different stages of ontogenetic development are more common than longitudinal comparisons in the physiological literature (e.g., 205,280,363,382,389). Static scaling considers the relationship between Y and M among individuals of the same developmental stage within a species, such as within an instar for insects (e.g., 342,408).…”

Section: Describing Scaling Relationshipsmentioning

confidence: 99%

Metabolic Scaling in Animals: Methods, Empirical Results, and Theoretical Explanations

White

Kearney

2014

Comprehensive Physiology

167

174

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Life on earth spans a size range of around 21 orders of magnitude across species and can span a range of more than 6 orders of magnitude within species of animal. The effect of size on physiology is, therefore, enormous and is typically expressed by how physiological phenomena scale with mass(b). When b ≠ 1 a trait does not vary in direct proportion to mass and is said to scale allometrically. The study of allometric scaling goes back to at least the time of Galileo Galilei, and published scaling relationships are now available for hundreds of traits. Here, the methods of scaling analysis are reviewed, using examples for a range of traits with an emphasis on those related to metabolism in animals. Where necessary, new relationships have been generated from published data using modern phylogenetically informed techniques. During recent decades one of the most controversial scaling relationships has been that between metabolic rate and body mass and a number of explanations have been proposed for the scaling of this trait. Examples of these mechanistic explanations for metabolic scaling are reviewed, and suggestions made for comparing between them. Finally, the conceptual links between metabolic scaling and ecological patterns are examined, emphasizing the distinction between (1) the hypothesis that size- and temperature-dependent variation among species and individuals in metabolic rate influences ecological processes at levels of organization from individuals to the biosphere and (2) mechanistic explanations for metabolic rate that may explain the size- and temperature-dependence of this trait.

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“…Standard metabolic rate (SMR, ml O 2 min -1 ) was measured at 30°C in 44 captive crocodiles in relation to body mass (M, kg) [28]. The measurements were made under carefully controlled conditions, over several days in post-absorptive animals.…”

Section: Methods and Resultsmentioning

confidence: 99%

Maximal Aerobic and Anaerobic Power Generation in Large Crocodiles versus Mammals: Implications for Dinosaur Gigantothermy

Seymour

2013

PLoS ONE

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Inertial homeothermy, the maintenance of a relatively constant body temperature that occurs simply because of large size, is often applied to large dinosaurs. Moreover, biophysical modelling and actual measurements show that large crocodiles can behaviourally achieve body temperatures above 30°C. Therefore it is possible that some dinosaurs could achieve high and stable body temperatures without the high energy cost of typical endotherms. However it is not known whether an ectothermic dinosaur could produce the equivalent amount of muscular power as an endothermic one. To address this question, this study analyses maximal power output from measured aerobic and anaerobic metabolism in burst exercising estuarine crocodiles, Crocodylusporosus , weighing up to 200 kg. These results are compared with similar data from endothermic mammals. A 1 kg crocodile at 30°C produces about 16 watts from aerobic and anaerobic energy sources during the first 10% of exhaustive activity, which is 57% of that expected for a similarly sized mammal. A 200 kg crocodile produces about 400 watts, or only 14% of that for a mammal. Phosphocreatine is a minor energy source, used only in the first seconds of exercise and of similar concentrations in reptiles and mammals. Ectothermic crocodiles lack not only the absolute power for exercise, but also the endurance, that are evident in endothermic mammals. Despite the ability to achieve high and fairly constant body temperatures, therefore, large, ectothermic, crocodile-like dinosaurs would have been competitively inferior to endothermic, mammal-like dinosaurs with high aerobic power. Endothermy in dinosaurs is likely to explain their dominance over mammals in terrestrial ecosystems throughout the Mesozoic.

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Scaling of standard metabolic rate in estuarine crocodiles Crocodylus porosus

Cited by 27 publications

References 51 publications

Physiological constraints on body size distributions in Crocodyliformes

Physiological constraints on body size distributions in Crocodyliformes

Metabolic Scaling in Animals: Methods, Empirical Results, and Theoretical Explanations

Maximal Aerobic and Anaerobic Power Generation in Large Crocodiles versus Mammals: Implications for Dinosaur Gigantothermy

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