Metabolic and behavioral responses of muskrats (Ondatra zibethicus) to elevated CO2 in a simulated winter microhabitat

1986 ◽  
Vol 64 (3) ◽  
pp. 738-743
Author(s):  
Robert A. MacArthur
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Behavioral Responses ◽  
Metabolic Responses ◽  
Foraging Activity ◽  
Ondatra Zibethicus ◽  
Daily Rate ◽  
Rate Of Oxygen Consumption ◽  
Breathing Room ◽  
Avoidance Reactions

Metabolic and behavioral responses to inspired CO2 were investigated in muskrats housed in a microhabitat designed to simulate winter field conditions. Mean daily rate of oxygen consumption [Formula: see text] declined from 1.46 mL O2∙g∙h−1 in animals breathing room air to 1.11–1.25 mL O2∙g∙h−1 in animals inhaling 4–10% CO2 in the simulated lodge. Daily patterns of [Formula: see text], abdominal body temperature (Tb), and foraging activity were minimally affected by chronic CO2 exposure, though muskrats breathing 9–10% CO2 made shorter voluntary dives. The ability of muskrats to rewarm following foraging activity was slightly depressed by hypercapnia. Abrupt exposure of resting animals to ambient CO2 levels of 10–16% often elicited avoidance reactions in the absence of any apparent change in [Formula: see text] or Tb. This study provides the first demonstration of behavioral and metabolic responses by muskrats to CO2 levels encountered in the winter microhabitat of this species.

scholarly journals The metabolic response of the Bradypus sloth to temperature

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5600 ◽  
Author(s):  
Rebecca Naomi Cliffe ◽  
David Michael Scantlebury ◽  
Sarah Jane Kennedy ◽  
Judy Avey-Arroyo ◽  
Daniel Mindich ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Energy Expenditure ◽  
High Power ◽  
Metabolic Response ◽  
Metabolic Responses ◽  
Metabolic Depression ◽  
Wide Range ◽  
Energetic Constraints ◽  
Power Costs

Poikilotherms and homeotherms have different, well-defined metabolic responses to ambient temperature (Ta), but both groups have high power costs at high temperatures. Sloths (Bradypus) are critically limited by rates of energy acquisition and it has previously been suggested that their unusual departure from homeothermy mitigates the associated costs. No studies, however, have examined how sloth body temperature and metabolic rate vary with Ta. Here we measured the oxygen consumption (VO2) of eight brown-throated sloths (B. variegatus) at variable Ta’s and found that VO2 indeed varied in an unusual manner with what appeared to be a reversal of the standard homeotherm pattern. Sloth VO2 increased with Ta, peaking in a metabolic plateau (nominal ‘thermally-active zone’ (TAZ)) before decreasing again at higher Ta values. We suggest that this pattern enables sloths to minimise energy expenditure over a wide range of conditions, which is likely to be crucial for survival in an animal that operates under severe energetic constraints. To our knowledge, this is the first evidence of a mammal provisionally invoking metabolic depression in response to increasing Ta’s, without entering into a state of torpor, aestivation or hibernation.

The heat increment of feeding and its thermoregulatory implications in the short-tailed shrew (Blarina brevicauda)

2003 ◽  
Vol 81 (8) ◽  
pp. 1445-1453 ◽  
Author(s):  
Allyson G Hindle ◽  
Ian W McIntyre ◽  
Kevin L Campbell ◽  
Robert A MacArthur
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Nutritional Status ◽  
Blarina Brevicauda ◽  
Open Flow ◽  
Metabolic Chamber ◽  
Heat Increment Of Feeding ◽  
Heat Increment ◽  
Rate Of Oxygen Consumption ◽  
Excretion Rates

The nature and potential thermoregulatory benefits of the heat increment of feeding (HIF) were investigated in short-tailed shrews (Blarina brevicauda). At thermoneutrality, the postprandial rate of oxygen consumption ([Formula: see text]O2) of shrews increased by an average of 18% beyond fasting levels for ca. 2 h following the consumption of 3.5 g of earthworms. Over the same period, body temperature increased by an average of 0.6 °C. The digesta-retention time calculated from nickel alloy tracer excretion rates (168.1 ± 11.4 min (mean ± SE); n = 7) exceeded the duration of HIF (117.5 ± 10.4 min; n = 6) by 43%. This finding suggests that the mechanical costs of feeding may be a relatively mi nor component of HIF in this species. Regression of resting [Formula: see text]O2 on ambient temperature (Ta) below thermo neutrality yielded similar slopes (P = 0.71) and intercepts (P = 0.33) for fed and fasted animals, suggesting that HIF substitutes, at least partially, for facultative thermogenesis at low Ta. We found no evidence that HIF enhanced microclimate warming of an insulated, open-flow metabolic chamber occupied by recently fed shrews. Occupancy of this chamber by shrews increased microclimate Ta from 5 to 9.0–9.5 °C regardless of their nutritional status.

Seasonal patterns of body temperature and activity in free-ranging muskrats (Ondatra zibethicus)

1979 ◽  
Vol 57 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Robert A. MacArthur
Keyword(s):  
Body Temperature ◽  
Seasonal Patterns ◽  
Foraging Activity ◽  
Ondatra Zibethicus ◽  
Winter Foraging ◽  
Body Cooling ◽  
Free Ranging ◽  
The Relationship ◽  
Foraging Time

Radiotelemetry techniques were employed to study the relationship between activity and abdominal temperature (Tb) changes in free-ranging muskrats (Ondatra zibethicus). Body cooling accompanied foraging activity by adults in winter and juveniles in summer and was retarded by periodic withdrawal from water. Net Tb decline during winter foraging rarely exceeded 2 °C and was relatively independent of foraging time for excursions exceeding 40 min duration. In addition to periodic rewarming within feeding shelters, muskrats appeared to avoid hypothermia during under-ice excursions by elevating Tb prior to entering water. This elevation was maximal (mean increase = 1.2 °C) for excursions exceeding 40 min duration. Comparable increases were not observed in summer.

CNS regulation of body temperature in euthermic and hibernating marmots (Marmota flaviventris)

1977 ◽  
Vol 232 (5) ◽  
pp. R203-R208 ◽  
Author(s):  
G. L. Florant ◽  
H. C. Heller
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Marmota Flaviventris ◽  
Hypothalamic Temperature ◽  
Proportionality Constant ◽  
Metabolic Heat ◽  
Slow Decline ◽  
Rate Of Oxygen Consumption ◽  
Hypothalamic Thermosensitivity ◽  
Deep Hibernation

Hypothalamic thermosensitivity of marmots was characterized during euthermia and hibernation. Hypothalamic temperature (Thy) was manipulated with chronically implanted, water-perfused thermodes while the animal's rate of oxygen consumption was continuously measured. The threshold Thy for eliciting an increase in metabolic heat production (MHP) and the proportionality constant (alphaMHP) relating rate of MHP to Thy were determined. In four euthermic marmots alphaMHP averaged -1.1 W-kg-1-degrees C-1. During the entrance into hibernation, as body temperature (Tb) declined from 36 to 8 degrees C, the threshold Thy for the MHP response progressively declined and was demonstrable at all times. The Thy of marmots in deep hibernation at an ambient temperature (Ta) of 5 degrees C plateaued near 7.5 degrees C, but threshold Thy for MHP showed a continuous slow decline of 0.2-0.4 degrees C a day, until one day prior to arousal. Proportional regulation of Tb was demonstrable at all times during deep hibernation. The average proportionality constant for the MHP response to hypothalamic cooling during deep hibernation in three marmots was -0.08 W-kg-1-degrees C-1. These results demonstrate that the hypothalamic regulator of Tb is active throughout hibernation and that there are progressive changes in its thermosensitivity.

Hibernation in the Eastern Pygmy Possum, Cercartetus-Nanus (Marsupialia, Burramyidae)

1993 ◽  
Vol 41 (1) ◽  
pp. 67 ◽  
Author(s):  
F Geiser
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Metabolic Rate ◽  
Air Temperature ◽  
The Body ◽  
Daily Torpor ◽  
Rate Of Oxygen Consumption ◽  
The Mean ◽  
Cercartetus Nanus ◽  
Torpor Bouts

The pattern of torpor was examined in the eastern pygmy possum, Cercartetus nanus (21 g). Animals displayed torpor regularly in the laboratory, and the occurrence of torpor increased with decreasing air temperature (T(a)). At high T(a) (18-degrees-C) animals usually exhibited daily torpor, but torpor bouts of up to 2 days were observed occasionally. The duration of torpor bouts lengthened with a lowering of T(a) and the mean bout duration at T(a) = 5-degrees-C was 17.0 +/- 2.5 days. The minimum metabolic rate (measured as rate of oxygen consumption) of torpid individuals was 0.018 +/- 0.003 mL O2 g-1 h-1, which is less than 2% of the basal metabolic rate. The body temperature (T(b)) Of torpid animals fell to a minimum of 1.3 +/- 0.4-degrees-C. These results clearly demonstrate that Cercartetus nanus is a deep hibernator.

Factorial scopes of cardio-metabolic variables remain constant with changes in body temperature in the varanid lizard, Varanus rosenbergi

2005 ◽  
Vol 288 (4) ◽  
pp. R992-R997 ◽  
Author(s):  
T. D. Clark ◽  
T. Wang ◽  
P. J. Butler ◽  
P. B. Frappell
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Oxygen Affinity ◽  
Aerobic Performance ◽  
Specific Rate ◽  
Aerobic Scope ◽  
Thermal Dependence ◽  
Hemoglobin Oxygen Affinity ◽  
Rate Of Oxygen Consumption ◽  
Metabolic Performance

The majority of information concerning the cardio-metabolic performance of varanids during exercise is limited to a few species at their preferred body temperature (Tb) even though, being ectotherms, varanids naturally experience rather large changes in Tb. Although it is well established that absolute aerobic scope declines with decreasing Tb, it is not known whether changes in cardiac output (V̇b) and/or tissue oxygen extraction, (CaO2 − Cv�[Formula: see text]), are in proportion to the rate of oxygen consumption (V̇o2). To test this, we studied six Rosenberg's goannas ( Varanus rosenbergi) while at rest and while maximally exercising on a treadmill both at 25 and 36°C. During maximum exercise both at 25 and 36°C, mass-specific rate of oxygen consumption (V̇o2kg) increased with an absolute scope of 8.5 ml min−1 kg−1 and 15.7 ml min−1 kg−1, respectively. Interestingly, the factorial aerobic scope was temperature-independent and remained at 7.0 which, at each Tb, was primarily the result of an increase in V̇bkg, governed by approximate twofold increases both in heart rate ( fH) and cardiac stroke volume (VSkg). Both at 25°C and 36°C, the increase in V̇bkg alone was not sufficient to provide all of the additional oxygen required to attain maximal V̇o2kg, as indicated by a decrease in the blood convection requirement V̇bkg/V̇o2kg; hence, there was a compensatory twofold increase in (CaO2 − [Formula: see text]). Although associated with an increase in hemoglobin-oxygen affinity, a decrease in Tb did not impair unloading of oxygen at the tissues and act to reduce (CaO2 − Cv�[Formula: see text]); both CaO2 and Cv�[Formula: see text] were maintained across Tb. The change in V̇o2kg with Tb, therefore, is solely reliant on the thermal dependence of V̇bkg. Maintaining a high factorial aerobic scope across a range of Tb confers an advantage in that cooler animals can achieve higher absolute aerobic scopes and presumably improved aerobic performance than would otherwise be achievable.

Postprandial exercise: prioritization or additivity of the metabolic responses?

2001 ◽  
Vol 204 (12) ◽  
pp. 2127-2132 ◽  
Author(s):  
Albert F. Bennett ◽  
James W. Hicks
Keyword(s):  
Oxygen Consumption ◽  
Metabolic Rate ◽  
Resting Metabolic Rate ◽  
Ventilation Rate ◽  
Oxygen Extraction ◽  
Metabolic Responses ◽  
Air Convection ◽  
Rate Of Oxygen Consumption ◽  
Monitor Lizards ◽  
The Cost

SUMMARY Monitor lizards (Varanus exanthematicus) were used to examine the prioritization or additivity of the metabolic responses associated with exercise and digestion, either of which can elevate metabolic rate independently. Rates of oxygen consumption (V̇.O2) and ventilation (V̇.E) were measured in lizards during fasting exercise, postprandial rest and postprandial exercise. In fasting animals, V̇.O2 increased with walking speed to a maximal value of 15.9mlO2kg−1min−1 at 1.25kmh−1. Postprandial resting metabolic rate was elevated significantly above fasting levels (4.1 versus 2.0mlO2kg−1min−1). During postprandial exercise, V̇.O2 increased to a maximal value of 18.8mlO2kg−1min−1 at 1.25kmh−1. At every level of exercise, V̇.O2 was significantly higher in postprandial animals by a similar increment; the maximal rate of oxygen consumption was significantly increased by 18% in postprandial individuals. Maximal V̇.E did not differ in fasting and postprandial animals and, therefore, the greater V̇.O2max of postprandial animals cannot be attributed to a higher ventilation rate. Air convection requirement (V̇.E/V̇.O2) is significantly lower in postprandial animals at rest and at all levels of exercise, indicating a relative hypoventilation and increased pulmonary oxygen extraction efficiency. We suggest that this increased oxygen extraction may be due to decreased cardiopulmonary shunts and/or to lower mixed venous oxygen content. The data unequivocally support an additivity model rather than prioritization models for the allocation of elevated metabolic rate: the postprandial metabolic increment is not suspended during exercise, but rather is added onto the cost of exercise. It is clear that fasting exercise did not elicit truly maximal levels of cardiopulmonary oxygen transport in these animals, indicating problems for design models that make this assumption.

scholarly journals Recovery heat in muscular contraction without lactic acid formation

1931 ◽  
Vol 108 (757) ◽  
pp. 279-301 ◽  
Keyword(s):  
Acetic Acid ◽  
Oxygen Consumption ◽  
Lactic Acid ◽  
Muscular Contraction ◽  
Acid Formation ◽  
Anaerobic Conditions ◽  
Spontaneous Breakdown ◽  
Rate Of Oxygen Consumption ◽  
Resting Muscle

In a comparison of muscles poisoned with mono-iodo-acetic acid (IAA) in the presence and in the absence of oxygen respectively, Lundsgaard (1930) found:- (1) That the spontaneous breakdown of phosphagen in poisoned resting muscle is much more rapid under anaerobic conditions. (2) That the onset of the characteristic contracture produced by IAA is accompanied always by an increase in the rate of oxygen consumption.

Proximal tubule dysfunction in cystine-loaded tubules: effect of phosphate and metabolic substrates

1996 ◽  
Vol 271 (3) ◽  
pp. F717-F722
Author(s):  
G. Bajaj ◽  
M. Baum
Keyword(s):  
Oxygen Consumption ◽  
Proximal Tubule ◽  
Tricarboxylic Acid Cycle ◽  
Dimethyl Ester ◽  
Proximal Tubules ◽  
Intracellular Atp ◽  
Metabolic Substrates ◽  
Rate Of Oxygen Consumption ◽  
Intracellular Phosphate

Intracellular cystine loading by use of cystine dimethyl ester (CDME) results in a generalized inhibition in proximal tubule transport due, in part, to a decrease in intracellular ATP. The present study examined the importance of phosphate and metabolic substrates in the proximal tubule dysfunction produced by cystine loading. Proximal tubule intracellular phosphorus was 1.8 +/- 0.1 in control tubules and 1.1 +/- 0.1 nmol/mg protein in proximal tubules incubated in vitro with CDME P < 0.001). Infusion of sodium phosphate in rabbits and subsequent incubation of proximal tubules with a high-phosphate medium attenuated the decrease in proximal tubule respiration and prevented the decrease in intracellular ATP with cystine loading. Tricarboxylic acid cycle intermediates have been shown to preserve oxidative metabolism in phosphate-depleted proximal tubules. In proximal tubules incubated with either 1 mM valerate or butyrate, there was a 42 and 34% reduction (both P < 0.05) in the rate of oxygen consumption with cystine loading. However, tubules incubated with 1 mM succinate or citrate had only a 13 and 14% P = NS) reduction in the rate of oxygen consumption, respectively. These data are consistent with a limitation of intracellular phosphate in the pathogenesis of the proximal tubule dysfunction with cystine loading.

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