Oscillatory pattern in oxygen consumption of Hummingbirds

Chauí‐Berlinck, José Guilherme; Bicudo, J. Eduardo P. W.; Monteiro, Luiz Henrique Alves; Navas, Carlos A.

doi:10.1016/s0306-4565(02)00005-0

Cited by 11 publications

(14 citation statements)

References 26 publications

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“…Within this temperature range, T b was constant, but metabolic rate was twice the minimum recorded. Our own studies of hummingbirds in an open-respirometry system designed for the fast acquisition of metabolic rate data also revealed unusual features (Chaui-Berlinck et al, 2002a): the birds did not show a steady-state condition of T b and metabolic rate. Time-series analysis revealed that the observed oscillatory pattern of metabolic rate exhibited long-range correlation, an observation that is compatible with the existence of control mechanisms operating to maintain such a pattern.…”

Section: Accepted 30 November 2005mentioning

confidence: 84%

Control of metabolic rate is a hidden variable in the allometric scaling of homeotherms

Chauí‐Berlinck

Navas

Monteiro

et al. 2005

Journal of Experimental Biology

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SUMMARY The allometric scaling exponent of the relationship between standard metabolic rate (SMR) and body mass for homeotherms has a long history and has been subject to much debate. Provided the external and internal conditions required to measure SMR are met, it is tacitly assumed that the metabolic rate(B) converges to SMR. If SMR does indeed represent a local minimum, then short-term regulatory control mechanisms should not operate to sustain it. This is a hidden assumption in many published articles aiming to explain the scaling exponent in terms of physical and morphological constraints. This paper discusses the findings of a minimalist body temperature(Tb) control model in which short-term controlling operations, related to the difference between Tb and the set-point temperatures by specific gains and time delays in the control loops,are described by a system of differential equations of Tb,B and thermal conductance. We found that because the gains in the control loops tend to increase as body size decreases (i.e. changes in B and thermal conductance are speeded-up in small homeotherms), the equilibrium point of the system potentially changes from asymptotically stable to a centre,transforming B and Tb in oscillating variables. Under these specific circumstances the very concept of SMR no longer makes sense. A series of empirical reports of metabolic rate in very small homeotherms supports this theoretical prediction, because in these animals B seems not to converge to a SMR value. We conclude that the unrestricted use of allometric equations to relate metabolic rate to body size might be misleading because metabolic control itself experiences size effects that are overlooked in ordinary allometric analysis.

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Section: Accepted 30 November 2005mentioning

confidence: 84%

Control of metabolic rate is a hidden variable in the allometric scaling of homeotherms

Chauí‐Berlinck

Navas

Monteiro

et al. 2005

Journal of Experimental Biology

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“…The tissue oxygenation is determined by an interplay of metabolism and supply. Fluctuations in the consumption of oxygen by mitochondria may also contribute to the 1/f-like dynamics both at the single cell level [134][135][136][137] and at the system level [138]. Moreover, measurements in awake and sleeping cats have shown that existence of spontaneous oscillating metabolic phenomenon in cortex that is not directly related to neural activity [139].…”

Section: Discussionmentioning

confidence: 99%

Origins of 1/f-like tissue oxygenation fluctuations in the murine cortex

Zhang

Gheres

Drew

2020

Preprint

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The concentration of oxygen in the brain spontaneously fluctuates, and the power distribution in these fluctuations has 1/f-like dynamics. Though these oscillations have been interpreted as being driven by neural activity, the origins of these 1/f-like oscillations is not well understood. Here, to gain insight of the origin of the 1/f-like oxygen fluctuations, we investigated the dynamics of tissue oxygenation and neural activity in awake behaving mice. We found that oxygen signal recorded from the cortex of mice had 1/f-like spectra. However, band-limited power in the local field potential, did not show corresponding 1/f-like fluctuations. When local neural activity was suppressed, the 1/f-like fluctuations in oxygen concentration persisted. Two-photon measurements of erythrocyte spacing fluctuations (‘stalls’) and mathematical modelling show that stochastic fluctuations in erythrocyte flow and stalling could underlie 1/f-like dynamics in oxygenation. These results show discrete nature of erythrocytes and their irregular flow, rather than neural activity, could drive 1/f-like fluctuations in tissue oxygenation.

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“…Birds are considered to be homeothermic endotherms, which implies the ability to maintain a constant body temperature over a broad range of ambient temperatures by adjusting their metabolism (Chaui-Berlinck et al, 2002). However small homeotherms have higher energetic demands at colder temperatures and require physiological adjustments in metabolic rate or insulation to counteract this (Downs and Brown, 2002;Soobramoney et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Physiological variation in amethyst sunbirds (Chalcomitra amethystina) over an altitudinal gradient in winter

Lindsay

Downs

Brown

2009

Journal of Experimental Biology

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SUMMARYFlexibility of metabolic rates within a species allows for the colonization of different habitats along an altitudinal and thus temperature gradient. The distribution range of amethyst sunbirds (Chalcomitra amethystina) within southern Africa includes an altitudinal gradient from the Drakensberg to the coast of KwaZulu-Natal. We expected that over this altitudinal gradient amethyst sunbirds would exhibit variation in winter metabolic rates, particularly basal metabolic rates (BMR) and resting metabolic rate (RMR) pre-and post-acclimation. Sunbirds from three locations, Underberg (1553 m above sea level; asl), Howick (1075 m asl) and Oribi Gorge (541 m asl) were used for this study. Upon capture, metabolic rate was measured indirectly by quantifying oxygen consumption (V O2 ) using flow-through respirometry, at 5 and 25°C. Birds were then acclimated at 25°C for 6 weeks on a 12 h:12 h L:D cycle. V O2 was measured post-acclimation at eight different temperatures (15, 5, 10, 20, 30, 28, 25 and 33°C). We found little variation in winter V O2 between individuals from the same locality, whereas significant variation was observed in V O2 at the same temperatures between individuals from the different localities and thus between altitudes. In particular, winter BMR decreased significantly with decreasing altitude post-acclimation. This study emphasizes the need to understand plasticity/flexibility in metabolic rates and to acknowledge altitudinal differences within a species, to make accurate predictions about the thermal physiology of a species and its responses to changes in ambient temperatures.

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Oscillatory pattern in oxygen consumption of Hummingbirds

Cited by 11 publications

References 26 publications

Control of metabolic rate is a hidden variable in the allometric scaling of homeotherms

Control of metabolic rate is a hidden variable in the allometric scaling of homeotherms

Origins of 1/f-like tissue oxygenation fluctuations in the murine cortex

Physiological variation in amethyst sunbirds (Chalcomitra amethystina) over an altitudinal gradient in winter

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