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Maximal aerobic and anaerobic power generation in large crocodiles versus mammals: implications for dinosaur gigantothermy - PubMed

  • ️Tue Jan 01 2013

Maximal aerobic and anaerobic power generation in large crocodiles versus mammals: implications for dinosaur gigantothermy

Roger S Seymour. PLoS One. 2013.

Abstract

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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Conflict of interest statement

Competing Interests: The author has declared that no competing interests exist.

Figures

Figure 1
Figure 1. Mean rate of lactate production in exercising Crocodylusporosus .

Data are given as rates per gram of muscle and in relation to body size in 24 animals. Data from [25]. A 3-parameter regression is set to the data (see text).

Figure 2
Figure 2. Rate of anaerobic power generation in Crocodylusporosus in relation to body mass.

Lower data set (open circles) is the measured mean rate over the entire course of exercise to fatigue [25]. Upper data set (filled circles) is the calculated burst rate during the first 10% of the exercise period, assuming that the rate decreases exponentially to zero at exhaustion. This multiplies the mean rate by a factor of 5. The curves are 3-parameter regressions set to the data (see text).

Figure 3
Figure 3. Rate of energy production (power) from anaerobic glycolysis during exhaustive exercise in Crocodylusporosus .

To fit on the figure, only 1 kg and 10 kg body masses are plotted (data not shown for larger animals). The total energy produced anaerobically during the entire exercise period is related to the area under each curve. Horizontal lines indicate mean anaerobic power to the point of fatigue. Curves are assumed exponential decreases in power during the exercise period. The highest points on the left represent burst power during the first 10% of exercise and are used to estimate the maximum initial anaerobic contribution to exercise. Data are derived from [25].

Figure 4
Figure 4. Allometric analysis of power output in Crocodylusporosus compared to mammals of the same size.

SMR is the standard metabolic rate, Aerobic is the aerobic power and Total is the sum of aerobic and anaerobic power output. Equations for the lines are provided in the text.

Figure 5
Figure 5. Total power output in Crocodylusporosus compared to a mammal of the same size.

Aerobic (blue bottom) and anaerobic (red top) fractions of the total are given for animals weighing 1, 10, 100 and 200 kg.

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References

    1. Lee MSY (2001) Molecules, morphology, and the monophyly of diapsid reptiles. Contrib Zool 70: 1-22.
    1. Dodson P (2003) Allure of El Lagarto—Why do dinosaur paleontologists love alligators, crocodiles, and their kin? Anat Rec 274A: 887-890. doi:10.1002/ar.a.10098. - DOI - PubMed
    1. Farmer CG, Sanders K (2010) Unidirectional airflow in the lungs of alligators. Science 327: 338-340. doi:10.1126/science.1180219. PubMed: 20075253. - DOI - PubMed
    1. Brazaitis P, Watanabe ME (2011) Crocodilian behaviour: a window to dinosaur behaviour? Hist Biol 23: 73-90. doi:10.1080/08912963.2011.560723. - DOI
    1. Paladino FV, O’Connor MP, Spotila JR (1990) Metabolism of leatherback turtles, gigantothermy, and thermoregulation of dinosaurs. Nature 344: 858-860. doi:10.1038/344858a0. - DOI

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Supported by the Australian Research Council grant LP0882478. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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