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1.
The degree of dietary fatty acid unsaturation affects torpor patterns and lipid composition of a hibernator 总被引:4,自引:2,他引:4
F. Geiser B. M. McAllan G. J. Kenagy 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(4):299-305
Diets rich in unsaturated and polyunsaturated fatty acids have a positive effect on mammalian torpor, whereas diets rich in saturated fatty acids have a negative effect. To determine whether the number of double bonds in dietary fatty acids are responsible for these alterations in torpor patterns, we investigated the effect of adding to the normal diet 5% pure fatty acids of identical chain length (C18) but a different number of double bonds (0, 1, or 2) on the pattern of hibernation of the yellow-pine chipmunk, Eutamias amoenus. The response of torpor bouts to a lowering of air temperature and the mean duration of torpor bouts at an air temperature of 0.5°C (stearic acid C18:0, 4.5±0.8 days, oleic acid C18:1, 8.6±0.5 days; linoleic acid C18:2, 8.5±0.7 days) differed among animals that were maintained on the three experimental diets. The mean minimum body temperatures (C18:0, +2.3±0.3°C; C18:1, +0.3±0.2°C; C18:2,-0.2±0.2°C), which torpid individuals defended by an increase in metabolic rate, and the metabolic rate of torpid animals also differed among diet groups. Moreover, diet-induced differences were observed in the composition of total lipid fatty acids from depot fat and the phospholipid fatty acids of cardiac mitochondria. For depot fat 7 of 13 and for heart mitochondria 7 of 14 of the identified fatty acids differed significantly among the three diet groups. Significant differences among diet groups were also observed for the sum of saturated, unsaturated and polyunsaturated fatty acids. These diet-induced alterations of body fatty acids were correlated with some of the diet-induced differences in variables of torpor. The results suggest that the degree of unsaturation of dietary fatty acids influences the composition of tissues and membranes which in turn may influence torpor patterns and thus survival of hibernation.Abbreviations bm
body mass
-
T
a
air temperature
-
T
b
body temperature
- FA
fatty acid
- MR
metabolic rate
- MUFA
monounsaturated fatty acids
- PUFA
polyunsaturated fatty acids
-
VO2
rate of oxygen consumption
- SFA
saturated fatty acids
- UFA
unsaturated fatty acids
- UI
unsaturation index
- SNK
Student-Newman-Keuls test 相似文献
2.
Ehrhardt N Heldmaier G Exner C 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2005,175(3):193-200
The golden spiny mouse (Acomys russatus) is an omnivorous desert rodent that does not store food, but can store large amounts of body fat. Thus, it provides a good animal model to study physiological and behavioural adaptations to changes in food availability. The aim of this study was to investigate the time course of metabolic and behavioural responses to prolonged food restriction. Spiny mice were kept at an ambient temperature of 27°C and for 3 weeks their food was reduced individually to 30% of their previous ad libitum food intake. When fed ad libitum, their average metabolic rate was 82.77±3.72 ml O2 h–1 during the photophase and 111.19±4.30 ml O2 h–1 during the scotophase. During food restriction they displayed episodes of daily torpor when the minimal metabolic rate gradually decreased to 16.07±1.07 ml O2 h–1, i.e. a metabolic rate depression of approximately 83%. During the hypometabolic bouts the minimum average body temperature Tb, decreased gradually from 32.6±0.1°C to 29.0±0.4°C, with increasing duration of consecutive bouts. In parallel, the animals increased their activity during the remaining daytime. Torpor as well as hyperactivity was suppressed immediately by refeeding. Thus golden spiny mice used two simultaneous strategies to adapt to shortened food supply, namely energysaving torpor during their resting period and an increase in locomotor activity pattern during their activity period. 相似文献
3.
X. Song G. Körtner F. Geiser 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(4):291-297
Physiological mechanisms causing reduction of metabolic rate during torpor in heterothermic endotherms are controversial. The original view that metabolic rate is reduced below the basal metabolic rate because the lowered body temperature reduces tissue metabolism has been challenged by a recent hypothesis which claims that metabolic rate during torpor is actively downregulated and is a function of the differential between body temperature and ambient temperature, rather than body temperature per se. In the present study, both the steady-state metabolic rate and body temperature of torpid stripe-faced dunnarts, Sminthopsis macroura (Dasyuridae: Marsupialia), showed two clearly different phases in response to change of air temperature. At air temperatures between 14 and 30°C, metabolic rate and body temperature decreased with air temperature, and metabolic rate showed an exponential relationship with body temperature (r
2=0.74). The Q
10 for metabolic rate was between 2 and 3 over the body temperature range of 16 to 32°C. The difference between body temperature and air temperature over this temperature range did not change significantly, and the metabolic rate was not related to the difference between body temperature and air temperature (P=0.35). However, the apparent conductance decreased with air temperature. At air temperatures below 14°C, metabolic rate increased linearly with the decrease of air temperature (r
2=0.58) and body temperature was maintained above 16°C, largely independent of air temperature. Over this air temperature range, metabolic rate was positively correlated with the difference between body temperature and air temperature (r
2=0.61). Nevertheless, the Q
10 for metabolic rate between normothermic and torpid thermoregulating animals at the same air temperature was also in the range of 2–3. These results suggest that over the air temperature range in which body temperature of S. macroura was not metabolically defended, metabolic rate during daily torpor was largely a function of body temperature. At air temperatures below 14°C, at which the torpid animals showed an increase of metabolic rate to regulate body temperature, the negative relationship between metabolic rate and air temperature was a function of the differential between body temperature and air temperature as during normothermia. However, even in thermoregulating animals, the reduction of metabolic rate from normothermia to torpor at a given air temperature can also be explained by temperature effects.Abbreviations
BM
body mass
-
BMR
basal metabolic rate
-
C
apparent conductance
-
MR
metabolic rate
-
RMR
resting metabolic rate
-
RQ
respiratory quotient
-
T
a
air temperature
-
T
b
body temperature
-
T
lc
lower critical temperature
-
T
tc
critical air temperature during torpor
-
TMR
metabolic rate during torpor
-
TNZ
thermoneutral zone
- T
difference between body temperature and air temperature
- VO2
rate of oxygen consumption 相似文献
4.
F. Wollnik B. Schmidt 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(3):171-182
Body temperature of five European hamsters exposed to semi-natural environmental conditions at 47° N in Southern Germany was recorded over a 1.5-year period using intraperitoneal temperature-sensitive radio transmitters. The animals showed pronounced seasonal changes in body weight and reproductive status. Euthermic body temperature changed significantly throughout the year reaching its maximum of 37.9±0.2°C in April and its minimum of 36.1±0.4°C in December. Between November and March the hamsters showed regular bouts of hibernation and a few bouts of shallow torpor. During hibernation body temperature correlated with ambient temperature. Monthly means of body temperature during hibernation were highest in November (7.9±0.8°C) and March (8.2±0.5°C) and lowest in January (4.4±0.7°C). Using periodogram analysis methods, a clear diurnal rhythm of euthermic body temperature could be detected between March and August, whereas no such rhythm could be found during fall and winter. During hibernation bouts, no circadian rhythmicity was evident for body temperature apart from body temperature following ambient temperature with a time lag of 3–5 h. On average, hibernation bouts lasted 104.2±23.8 h with body temperature falling to 6.0±1.7°C. When entering hibernation the animals cooled at a rate of -0.8±0.2°C·h-1; when arousing from hibernation they warmed at a rate of 9.9±2.4°C·h-1. Warming rates were significantly lower in November and December than in January and February, and correlated with ambient temperature (r=-0.46, P<0.01) and hibernating body temperature (r=-0.47, P<0.01). Entry into hibrnation occured mostly in the middle of the night (mean time of day 0148 hours ±3.4 h), while spontaneous arousals were widely scattered across day and night. For all animals regression analysis revealed free-running circadian rhythms for the timing of arousal. These results suggest that entry into hibernation is either induced by environmental effects or by a circadian clock with a period of 24 h, whereas arousal from hibernation is controlled by an endogenous rhythm with a period different from 24 h.Abbreviations
bw
body weight
-
CET
central European time
-
T
a
ambient temperature
-
T
b
body temperature
-
TTL
transistor-transistor logic 相似文献
5.
G. T. H. Ellison J. D. Skinner J. W. H. Ferguson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(1):62-68
The daily activity and energy metabolism of pouched mice (Saccostomus campestris) from two localities in southern Africa was examined following warm (25 °C) and cold (10 °C) acclimation under long (LD 14:10) and short (LD 10:14) photoperiol. There was no differential effect of photoperiod on the daily activity or metabolism of pouched mice from the two localities examined, which suggests that reported differences in photoresponsivity between these two populations were not the result of differences in daily organisation. Neverthe-less, there was a significant increase in metabolism at 10 °C, irrespective of photoperiod, even though seven cold-acclimated animals displayed bouts of spontaneous torpor and saved 16.4–36.2% of their daily energy expenditure. All but one of these bouts occurred under short photoperiod, which suggests that short photoperiod facilitated the expression of torpor and influenced the daily energy metabolism of these individuals. As expected for a noctureal species, the amount of time spent active increased following acclimation to short photoperiod at 25 °C. However, there was a reduction in mean activity levels under short photoperiod at 10 °C, possibly because the stimulation of activity by short photoperiod was masked by a reduction in activity during bouts of spontaneous torpor. Cold temperature clearly had an overriding effect on the daily activity and metabolism of this species by necessitating an increase in metabolic heat production and eliciting spontaneous torpor which overrode the effect of short photoperiod on activity at an ambient temperature of 10 °C.Abbreviations 3-ANOVA
three-way analysis of variance
- %ACT
percentage of time spent active
- ADMR
average daily metabolic rate
-
M
b
body mass
- MR
metabolic rate
- MRdark
metabolic rate recorded during the dark phase
- MRlight
metabolic rate recorded during the light phase
- NST
non-shivering thermogenesis
- RQ
respiratory quotient
- STPD
standard temperature and pressure, dry
-
T
a
ambient temperature
-
T
b
body temperature
-
VO2
oxygen consumption 相似文献
6.
E. Król 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(6):503-507
Body temperature and oxygen consumption were measured in the eastern hedgehog,Erinaceus concolor Martin 1838, during summer at ambient temperatures (T
a) between-6.0 and 35.6°C.E. concolor has a relatively low basal metabolic rate (0.422 ml O2·g-1·h-1), amounting to 80% of that predicted from its body mass (822.7 g). Between 26.5 and 1.2°C, the resting metabolic rate increases with decreasing ambient temperature according to the equation: RMR=1.980-0.057T
a. The minimal heat transfer coefficient (0.057 ml O2·g-1·h-1·°C-1) is higher than expected in other eutherian mammals, which may result from partial conversion of hair into spines. At lower ambient temperature (from-4.6 to-6.0° C) there is a drop in body temperature (from 35.2 to 31.4° C) and a decrease in oxygen consumption (1.530 ml O2·g-1·h-1) even though the potential thermoregulation capabilities of this species are significantly higher. This is evidenced by the high maximum noradrenaline-induced non-shivering thermogenesis (2.370 ml O2·g-1·h-1), amounting to 124% of the value predicted. The active metabolic rate at ambient temperatures between 31.0 and 14.5° C averages 1.064 ml O2·g-1·h-1; at ambient temperatures between 14.5 and 2.0° C AMR=3.228-0.140T
a.Abbreviations AMR
active metabolic rate
- bm
body mass
- BMR
basal metabolic rate
-
h
heat transfer coefficient
- NA
noradrenaline
- NST
non-shivering thermogenesis
- NSTmax
maximum rate of NA-induced non-shivering thermogenesis
- RMR
resting metabolic rate
- RQ
respiratory quotient
- STPD
standard temperature and pressure (25°C, 1 ATM)
-
T
a
ambient temperature
-
T
b
body temperature 相似文献
7.
S. Marhold A. Nagel 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,164(8):636-645
Body temperature, oxygen consumption, respiratory and cardiac activity and body mass loss were measured in six females and four males of the subterranean Zambian mole rat Cryptomys sp. (karyotype 2 n=68), at ambient temperatures between 10 and 35°C. Mean body temperature ranged between 36.1 and 33.2°C at ambient temperatures of 32.5–10°C and was lower in females (32.7°C) than in males (33.9°C) at ambient temperatures of 10°C but dit not differ at thermoneutrality (32.5°C). Except for body temperature, mean values of all other parameters were lowest at thermoneutrality. Mean basal oxygen consumption of 0.76 ml O2·g-1· h-1 was significantly lower than expected according to allometric equations and was different in the two sexes (females: 0.82 ml O2·g-1·h-1, males: 0.68 ml O2·g1·h-1) but was not correlated with body mass within the sexes. Basal respiratory rate of 74·min-1 (females: 66·min1, males: 87·min-1) and basal heart rate of 200·min-1 (females: 190·min-1, males: 216·min-1) were almost 30% lower than predicted, and the calculated thermal conductance of 0.144 ml O2·g-1·h1·°C-1 (females; 0.153 ml O2·g-1·h-1·°C-1, males: 0.131 ml O2·g-1·h-1·°C-1) was significantly higher than expected. The body mass loss in resting mole rats of 8.6–14.1%·day-1 was high and in percentages higher in females than in males. Oxygen consumption and body mass loss as well as respiratory and cardiac activity increased at higher and lower than thermoneutral temperatures. The regulatory increase in O2 demand below thermoneutrality was mainly saturated by increasing tidal volume but at ambient temperatures <15°C, the additional oxygen consumption was regulated by increasing frequency with slightly decreasing tidal volume. Likewise, the additional blood transport capacity was mainly effected by an increasing stroke volume while there was only a slight increase of heart frequency. In an additional field study, temperatures and humidity in different burrow systems have been determined and compared to environmental conditions above ground. Constant temperatures in the nest area 70 cm below ground between 26 and 28°C facilitate low resting metabolic rates, and high relative humidity minimizes evaporative water loss but both cause thermoregulatory problems such as overheating while digging. In 13–16 cm deep foraging tunnels, temperature fluctuations were higher following the above ground fluctuations with a time lag. Dominant breeding females had remarkably low body temperatures of 31.5–32.3°C at ambient temperatures of 20°C and appeared to be torpid. This reversible hypothermy and particular social structure involving division of labour are discussed as a strategy reducing energy expenditure in these eusocial subterranean animals with high foraging costs.Abbreviations BMR
basal metabolic rate
- br
breath
-
C
thermal conductance
- HR
neart rate
- LD
light/dark
-
M
b
body mass
- MR
metabolic rate
- OP
oxygen pulse
- PCO2
partial pressure of carbon dioxide
- PO2
partial pressure of oxygen
- RMR
resting metabolic rate
- RR
respiratory rate
-
T
a
ambient temperature
-
T
b
body temperature
- TNZ
thermal neural zone
-
O2
oxygen consumption 相似文献
8.
D. A. Croll E. McLaren 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(2):160-166
The diving and thermoregulatory metabolic rates of two species of diving seabrid, common (Uria aalge) and thick-billed murres (U. lomvia), were studied in the laboratory. Post-absorptive resting metabolic rates were similar in both species, averaging 7.8 W·kg-1, and were not different in air or water (15–20°C). These values were 1.5–2 times higher than values predicted from published allometric equations. Feeding led to increases of 36 and 49%, diving caused increases of 82 and 140%, and preening led to increases of 107 and 196% above measured resting metabolic rates in common and thick-billed murres, respectively. Metabolic rates of both species increased linearly with decreasing water temperature; lower critical temperature was 15°C in common murres and 16°C in thick-billed murres. Conductance (assuming a constant body temperature) did not change with decreasing temperature, and was calculated at 3.59 W·m-2·oC-1 and 4.68 W·m-2·oC-1 in common and thick-billed murres, respectively. Murres spend a considerable amount of time in cold water which poses a significant thermal challenge to these relatively small seabirds. If thermal conductance does not change with decreasing water temperature, murres most likely rely upon increasing metabolism to maintain body temperature. The birds probably employ activities such as preening, diving, or food-induced thermogenesis to meet this challenge.Abbreviations ADL
aerobic dive limit
- BMR
basal metabolic rate
- FIT
food-induced thermogenesis
- MHP
metabolic heat production
- MR
metabolic rate
- PARR
post-absorption resting rate
- RMR
resting metabolic rate
- RQ
respiratory quotient
- SA
surface area
- STPD
standard temperature and pressure (25°C, 1 ATM)
-
T
a
ambient temperature
-
T
b
body temperature
-
T
IC
Iower critical temperatiure
- TC
thermal conductance
-
V
oxygen consumption rate
-
W
body mass 相似文献
9.
Daily and seasonal cycles of body temperature and aspects of heterothermy in the hedgehog Erinaceus europaeus 总被引:1,自引:1,他引:0
P. A. Fowler P. A. Racey 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(3):299-307
Summary Intra-abdominal temperature-sensitive radio transmitters were used to collect more than 350 sets of body temperature (T
b
) data from 23 captive adult hedgehogs over a 3-year period. Each data set comprised measurements made every 1/2 h for 24-h periods. Between 20 and 60 such data sets were recorded every calendar month, and a total of 17400 measurements of T
b
were collected. The hedgehogs were exposed to natural environmental conditions at 57°N in NE Scotland. Hedgehogs showed seasonal changes in mean daily euthermic T
b
,with a July maximum of 35.9±0.2°C, a September minimum of 34.7±0.9°C, and a marked circadian T
b
cycle that correlates closely with photoperiod. Maximal T
b
occurred within 2 h of midnight and this pattern of nocturnal maximum and diurnal minimum T
b
was most marked between April and September. The circadian T
b
cycle was least correlated with photoperiod during winter. Hibernal T
b
during winter correlated with ambient temperature (T
a
),it was maximal in September (17.7±1.0°C) and minimal in December (5.2±0.9°C). Apart from the tracking of T
a
and T
b
during hibernal bouts, with a time-lag of 4–6 h, circadian rhythmicity of hibernal T
b
was not evident. However, the T
b
of hibernating hedgehogs rose significantly when T
a
fell below — 5°C, although the animals did not neccessarily arouse. Although hibernal bouts occurred between September and April, 89.5% of such bouts were recorded between November and February. The mean time of entry into hibernation was 01:45±5.1 h GMT while the mean time of the start of spontaneous arousal from hibernation was 11:53±4.8 h GMT. Therefore, during hibernation hedgehogs were either fully aroused at night, when euthermic hedgehogs have maximalT
b
,or in deep hibernation around midday, when euthermic hedgehogs have minimal T
b
.Since wild hedgehogs will feed during spontaneous arousal from hibernation, these timings are probably adaptive, and suggest that entry into, and arousal from, hibernation may be extensions of circadian cyclicity. Spontaneous bouts of transient shallow torpor (TST) were recorded throughout the year, with nearly 80% of observations occurring during August and September, at the start of the hibernal period. TST bouts lasted for 4.9±2.9 h, with T
b
falling to 25.8±3.1 °C. Only 20% of TST bouts immediately preceded hibernation and their duration did not correlate with T
a
or body mass. TST bouts started at 06:51±4.7 h GMT, significantly later than entry into hibernation, and ended at 13:04±5.4 h GMT. The function of TST bouts is unclear, but they may be preparation for the hibernation season or a further energy conservation strategy. When arousing from hibernation hedgehogs warmed at a rate of 1.9±0.4°C·h-1, and when entering hibernation cooled at 7.9±1.9°C·h-1. Warming rates were slightly higher during mid-winter when T
b
and body mass were minimal, but cooling rates were 44% higher at the end of the hibernal period compared to the start. Cooling and warming rates were strikingly similar to those measured in hedgehogs at 31°N. These results demonstrate that thermoregulation in the hedgehog is closely regulated and changes on a seasonal basis, in meeting with requirements of surviving food shortages and low temperature during winter.Abbreviations
T
a
ambient temperature
-
T
b
body temperature
-
CSD
circular standard deviation
-
SWS
slow wave sleep
-
TST
transient shallow torpor 相似文献
10.
S. Saarela R. Hissa 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(7):546-555
Wood lemmings (Myopus schisticolor) were captured during their autumnal migration in September and October. The animals were maintained at 12°C and under 12L:12D photoperiod. Basal metabolic rate and thermogenic capacity of the wood lemming were studied. Basal metabolic rate was 3.54 ml O2·g-1·h-1, which is 215–238% of the expected value. The high basal metabolic rate seems to be typical of rodents living in high latitudes. The body temperature of the wood lemming was high (38.0–38.8°C), and did not fluctuate much during the 24-h recording. The high basal metabolic rate and the high body temperature are discussed with regard to behavioural adaptation to a low-quality winter diet. Thermogenic capacity, thermal insulation and non-shivering thermogenesis of the wood lemming displayed higher values than expected: 53.0 mW·g-1, 0.53 mW·g-1·C-1 and 53.2 mW·g-1, respectively. Brown adipose tissue showed typical thermogenic properties, although its respiratory property was fairly low, but mitochondrial protein content was high compared to other small mammals. The 24-h recording of body temperature and motor activity did not reveal whether the wood lemming is a nocturnal animal. Possibly, the expression of a circadian rhythm was masked by peculiar feeding behaviour. It is concluded that the wood lemming is well adapted to living in cold-temperature climates.Abbreviations BAT
brown adipose tissue; bm, body mass
- BMR
basal metabolic rate
-
C
conductance
- Cox
cytochrome-c-oxidase
- HP
heat production
- HPmax
maximum heat production
-
M
metabolism
- NA
noradrenaline
- NST
non-shivering thermogenesis
- NSTmax
maximum non-shivering thermogenesis
- RMR
resting metabolic rate
- RQ
respiratory quotient
-
T
a
anibient temperature
-
T
b
body temperature
-
T
lc
lower critical temperature
- UCP
uncoupling protein
- vO2
oxygen consumption
- vO2 max
maximum oxygen consumption 相似文献
11.
F. Geiser X. Song G. Körtner 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(3):190-196
Recently it was proposed that the low metabolic rate during torpor may be better explained by the reduction of thermal conductance than the drop of body temperature or metabolic inhibition. We tested this hypothesis by simultaneously measuring body temperature and metabolic rate as a function of ambient temperature in both torpid and normothermic stripe-faced dunnarts, Sminthopsis macroura (Marsupialia; approx. 25 g body mass), exposed to either air or He–O2 (21% oxygen in helium) atmospheres. He–O2 exposure increases the thermal conductance of homeothermic mammals by about twofold in comparison to an air atmosphere without apparent side-effects. Normothermic S. macroura exposed to He–O2 increased resting metabolic rate by about twofold in comparison to that in air because of the twofold increase in apparent thermal conductance. Torpid S. macroura exposed to He–O2 at ambient temperatures above the set-point for body temperature showed a completely different metabolic response. In contrast to normothermic individuals, torpid individuals significantly decreased or maintained a similar metabolic rate as those in air although the apparent thermal conductance in He–O2 was slightly raised. Moreover, the metabolic rate during torpor was only a fraction of that of normothermic individuals although the apparent thermal conductance differed only marginally between normothermia and torpor. Our study shows that a low thermal conductance is not the reason for the low metabolic rates during torpor. It suggests that interrelations between metabolic rate and body temperature of torpid endotherms above the set-point for body temperature differ fundamentally from those of normothermic and homeothermic endotherms.Abbreviations
T
a
ambient temperature
-
T
b
body temperature
-
BMR
basal metabolic rate
-
C
apparent thermal conductance
-
He–O
2
21% oxygen in helium
-
MR
metabolic rate
-
MSe
mean square-error
-
RMR
festing metabolic rate
-
TMR
metabolic rate during torpor
-
T
difference T
b-T
a
-
TNZ
thermoneutral zone
-
T
set
set-point for body temperature
-
O
2
rate of oxygen consumption 相似文献
12.
C. R. Brown G. G. Foster 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(7):658-664
Summary The effect of clustering behaviour on metabolism, body temperature, thermal conductance and evaporative water loss was investigated in speckled mousebirds at temperatures between 5 and 36°C. Within the thermal neutral zone (approximately 30–35 °C) basal metabolic rate of clusters of two birds (32.5 J·g-1·h-1) and four birds (28.5 J·g-1·h-1) was significantly lower by about 11% and 22%, respectively, than that of individuals (36.4 J·g-1·h-1). Similarly, below the lower critical temperature, the metabolism of clusters of two and four birds was about 14% and 31% lower, respectively, than for individual birds as a result of significantly lower total thermal conductance in clustered birds. Body temperature ranged from about 36 to 41°C and was positively correlated with ambient temperature in both individuals and clusters, but was less variable in clusters. Total evaporative water loss was similar in individuals and clusters and averaged 5–6% of body weight per day below 30°C in individuals and below 25°C in clusters. Above these temperatures total evaporative water loss increased and mousebirds could dissipate between 80 and 90% of their metabolic heat production at ambient temperatures between 36 and 39°C. Mousebirds not only clustered to sleep between sunset and sunrise but were also observed to cluster during the day, even at high ambient temperature. Whereas clustering at night and during cold, wet weather serves a thermoregulatory function, in that it allows the brrds to maintain body temperature at a reduced metabolic cost, clustering during the day is probably related to maintenance of social bonds within the flock.Abbreviations BMR
basal metabolic rate
- bw
body weight
-
C
totab
total thermal conductance
- EWI
evaporative water loss
-
M
metabolism
- RH
relative humidity
-
T
a
ambient temperature
-
T
b
body temperature
-
T
ch
chamber temperature
-
T
cl
cluster temperature
- TEWL
total evaporative water loss
- LCT
lower critical temperature
- TNZ
thermal neutral zone 相似文献
13.
Westman W Geiser F 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2004,174(1):49-57
The physiological signal for torpor initiation appears to be related to fuel availability. Studies on metabolic fuel inhibition in placental heterotherms show that glucose deprivation via the inhibitor 2-deoxy-D-glucose (2DG) initiates a torpor-like state, whereas fatty acid deprivation via mercaptoacetate (MA) does not. As previous studies using inhibitors were limited to quantifying body temperature in placentals, we investigated whether inhibition of glucose or fatty acids for cellular oxidation induces torpor in the marsupial hibernator Cercartetus nanus, and how the response of metabolic rate is related to body temperature. Glucoprivation initiated a torpor-like state in C. nanus, but animals had much higher minimum body temperatures and metabolic rates than those of torpid food-deprived animals and arousal rates were slower. Moreover, 2DG-treated animals were thermoregulating at ambient temperatures of 20 and 12 °C, whereas food-deprived torpid animals were thermo-conforming. We suggest that glucoprivation reduces the hypothalamic body temperature set point, but only by about 8 °C rather than the approximately 28 °C during natural torpor. Reduced fatty acid availability via MA also induced a torpor-like state in some C. nanus, with physiological variables that did not differ from those of torpid food-deprived animals. We conclude that reduced glucose availability forms only part of the physiological trigger for torpor initiation in C. nanus. Reduced fatty acid availability, unlike for placental heterotherms, may be an important cue for torpor initiation in C. nanus, perhaps because marsupials lack functional brown adipose tissue.Abbreviations BAT brown adipose tissue - BMR basal metabolic rate - 2DG 2-deoxy-D-glucose - FD food deprived - GLM general linear models - MA mercaptoacetate - MR metabolic rate - RQ respiratory quotient - Ta ambient temperature - Tb body temperature - Tset body temperature set pointCommunicated by I.D. Hume 相似文献
14.
Fritz Geiser 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(6):590-597
Summary Dieary lipids strongly influence the pattern of torpor and the body lipid composition of mammalian hibernators. The object of the present study was to investigate whether these diet-induced physiological and biochemical changes also occur in species that show shallow, daily torpor. Deer mice, Peromyscus maniculatus, were fed with rodent chow (control diet) or rodent chow with either 10% sunflower seed oil (unsaturated diet) or 10% sheep fat (saturated diet). Animals on the unsaturated diet showed a greater occurrence of torpor (80–100% vs 26–43%), longer torpor bouts (4.5 vs 2.25 h), a lower metabolic rate during torpor (0.96 vs 2.25 ml O2·g-1·h-1), and a smaller loss of body mass during withdrawal of food (2.35 vs 3.90 g) than animals on the saturated diet; controls were intermediate. These diet-induced physiological changes were associated with significant alterations in the fatty acid composition of depot fat, leg muscle and brain total lipids, and heart mitochondrial phospholipids. Significant differences in the total unsaturated fatty acid (UFA) content between animals on saturated and unsaturated diet were observed in depot fat (55.7% vs 81.1%) and leg muscle (56.4% vs 72.1%). Major compositional differences between diet groups also occurred in the concentration of n6 and/or n3 fatty acids of brain and heart mitochondria. The study suggests that dietary lipids may play an important role in the seasonal adjustment of physiology in heterothermic mammals.Abbreviations EDTA
ethylenediaminetetra-acetic acid
- HEPES
N-2 hydroxyethylpiperazine-N1-2-ethanesulphonic acid
- MUFA
monounsaturated fatty acids
- PUFA
polyunsaturated fatty acids
- RMR
Testing metabolic rate
- SD
standard deviation
- SFA
saturated fatty acids
- SNK
Student-Newman-Keuls test
- T1
air temperature
- Tb
body temperature
- UFA
unsaturated fatty acids
-
rate of oxygen consumption
Dedicated to the late John K. Raison 相似文献
15.
Daily torpor in the gray mouse lemur (Microcebus murinus) in Madagascar: energetic consequences and biological significance 总被引:5,自引:0,他引:5
J. Schmid 《Oecologia》2000,123(2):175-183
Patterns and energetic consequences of spontaneous daily torpor were measured in the gray mouse lemur (Microcebus murinus) under natural conditions of ambient temperature and photoperiod in a dry deciduous forest in western Madagascar. Over a
period of two consecutive dry seasons, oxygen consumption (VO2) and body temperature (T
b) were measured on ten individuals kept in outdoor enclosures. In all animals, spontaneous daily torpor occurred on a daily
basis with torpor bouts lasting from 3.6 to 17.6 h, with a mean torpor bout duration of 9.3 h. On average, body temperatures
in torpor were 17.3±4.9°C with a recorded minimum value of 7.8°C. Torpor was not restricted to the mouse lemurs’ diurnal resting
phase: entries occurred throughout the night and arousals mainly around midday, coinciding with the daily ambient temperature
maximum. Arousal from torpor was a two-phase process with a first passive, exogenous heating where the T
b of animals increased from the torpor T
b minimum to a mean value of 27.1°C before the second, endogenous heat production commenced to further raise T
b to normothermic values. Metabolic rate during torpor (28.6±13.2 ml O2 h–1) was significantly reduced by about 76% compared to resting metabolic rate (132.6±50.5 ml O2 h–1). On average, for all M. murinus individuals measured, hypometabolism during daily torpor reduced daily energy expenditure by about 38%. In conclusion, all
these energy-conserving mechanisms of the nocturnal mouse lemurs, with passive exogenous heating during arousal from torpor,
low minimum torpor T
bs, and extended torpor bouts into the activity phase, comprise an important and highly adapted mechanism to minimize energetic
costs in response to unfavorable environmental conditions and may play a crucial role for individual fitness.
Received: 8 July 1999 / Accepted: 3 December 1999 相似文献
16.
The roles of energetics,water economy,foraging behavior,and geothermal refugia in the distribution of the bat,Macrotus californicus 总被引:1,自引:0,他引:1
Gary P. Bell George A. Bartholomew Kenneth A. Nagy 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1986,156(3):441-450
Summary Energy metabolism, thermoregulation, and water flux ofMacrotus californicus, the most northerly representative of the Phyllostomidae, were studied in the laboratory using standard methods, and energy metabolism and water fluxes were studied in the field using the doubly labelled water method together with a time budget. Daily energy expenditures of free-living bats averaged 22.8 kJ during the winter study period. Approximately 60% of this was allocated to resting metabolism costs while in the primary roosts (22 h/day).Macrotus californicus is unable to use torpor. The thermoneutral zone (TNZ) in this species is narrow (33 to 40 °C) and metabolic rate increased rapidly as ambient temperature decreased below the TNZ. Basal metabolic rate was 1.25 ml O2/g·h, or 24 J/g·h. Total thermal conductance below the TNZ. was 1.8 mW/g·°C, similar to values measured for other bats. Evaporative water loss showed a hyperbolic increase with increasing ambient temperature, and was approximately 1% of total body mass/h in the TNZ. The success of these bats as year-round residents in deserts in the southwestern United States is probably not due to special physiological adaptations, but to roosting and foraging behavior. They use geothermally-heated winter roost sites (stable year-round temperatures of approximately 29 °C) which minimize energy expenditures, and they have an energetically frugal pattern of foraging that relies on visual prey location. These seem to be the two major factors which have allowedM. californicus to invade the temperate zone.Abbreviations
BMR
basal metabolic rate
-
FMR
field metabolic rate
-
T
a
ambient temperature
-
T
b
body temperature
-
T
lc,T
uc
lower and upper critical temperature, respectively
-
TBW
total body water
-
TNZ
thermoneutral zone 相似文献
17.
E. Hohtola A. Pyörnilä H. Rintamäki 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(6):430-437
The energetic adaptations of non-breeding Tengmalm's owls (Aegolius funereus) to temperature and fasting were studied during the birds' autumnal irruptions in western Finland. Allometric analysis (including literature data and two larger owl species measured in this study) indicates that the basal metabolic rate of owls is below the mean level of non-passerine birds. However, the basal metabolic rate of the 130-g Tengmalm's owl (1.13 W) is higher than in other owls of similar size. This is probably related to its northern distribution and nomadic life history. Relative to its size, Tengmalm's owl has excellent cold resistance due to effective insulation (lower critical temperature +10°C, minimum conductance 0.19 mW·cm-2·°C-1). Radiotelemetric measurements of body temperature showed that the level of body temperature is lower than for birds in general (39.4°C at zero activity) and that the amplitude of the diurnal cycle is also low (0.2–0.6°C). In contrast to many other small birds, Tengmalm's owls do not enter hypothermia during a 5-day fast at thermoneutrality or in cold. Moreover, while the metabolic rate per bird shows the expected mass-dependent decrease, the mass-specific rate decreases only slightly during the fast. In line with this, there was no decrease in the plasma triiodothyronine concentration during the fast in the owl, whereas a dramtic drop was observed in the pigeon and Japanese quail that were used as a reference. Despite this, the owl has an excellent capacity for fasting because of its ability to accumulate extensive fat depots and its low overall metabolic rate. Fasting reduced evaporative water loss to 50% of that in the fed state. Calculations show that the oxygen consumption observed in fasting birds would involve a production of metabolic water barely sufficient to compensate for evaporative water loss. The threat of dehydration may thus set a limit to the decrease in metabolic rate in fasting owls (owls rely totally on water either ingested with food or produced metabolically). We conclude that the metabolic strategy in Tengmalm's owl is largely dictated by an evolutionary pressure for fasting endurance. With the restrictions set by small body size and water economy, this bird has apparently taken these adaptations to an extreme. The constraints that preclude hypothermia, which could increase the capacity for fasting even more, remain unknown.Abbreviations BM
body mass
- BMR
basal metabolic rate
- EWL
vaporative water loss
- MR
metabolic rate
- T3
triiodothyronine
-
T
a
ambient temperature
-
T
b
body temperature
-
VO2
oxygen consumption 相似文献
18.
Bozinovic F Ruiz G Rosenmann M 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2004,174(4):293-297
We examined the energetics of the living fossil microbiotheriid Dromiciops gliroides, a nocturnal and rare small marsupial, endemic to the northern portion of the temperate forest of southern South America. We investigated the effects of changes at ambient temperature and food restriction on the energetics and patterns of torpor. We determined whether they exhibit shallow daily torpor or deep prolonged torpor like some Australian marsupials. Thermal conductance was 92.5% of the expected value for a similarly sized eutherian and basal metabolic rate was 82.9 and 58.6% of the predicted value for standard metatherians and eutherians, respectively. Euthermic D. gliroides showed daily fluctuations in body temperature, being significantly higher during the night. Dromiciops gliroides entered torpor and aroused spontaneously. The duration of torpor bouts increased in response to decreasing ambient temperature; torpor bout duration ranged from 10 h at 20 °C to 120 h at 12.5 °C. This study is the first record of deep torpor or hibernation for a South American mammal. Torpor in this species as well as in marsupials in general appears to be an opportunistic response to unpredictable biotic and abiotic conditions.Abbreviations VO2 metabolic rate - Tb body temperature - Ta ambient temperature - BMR basal metabolic rate - C thermal conductance - Tm temperature differentialCommunicated by I.D. Hume 相似文献
19.
S. K. Maloney T. J. Dawson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(6):473-481
Ventilation was studied in the emu, a large flightless bird of mass 40kg, within the range of ambient temperatures from-5 to 45°C. Data for the emu and 21 other species were used to calculate allometric relationships for resting ventilatory parameters in birds (breath frequency=13.5 mass-0.314; tidal volume=20.7 mass1.0). At low ambient temperatures the ventilatory system must accommodate the increased metabolic demand for oxygen. In the emu this was achieved by a combination of increased tidal volume and increased oxygen extraction. Data from emus sitting and standing at-5°C, when metabolism is 1.5x and 2.6x basal metabolic rate, respectively, indicate that at least in the emu an increase in oxygen extraction can be stimulated by low temperature independent of oxygen demand. At higher ambient temperatures ventilation was increased to facilitate respiratory water loss. The emu achieved this by increased respiratory frequency. At moderate heat loads (30–35°C) tidal volume fell. This is usually interpreted as a mechanism whereby respiratory water loss can be increased without increasing parabronchial ventilation. At 45°C tidal volume increased; however, past studies have shown that CO2 washout is minimal under these conditions. The mechanism whereby this is possible is discussed.Abbreviations BMR
basal metabolic rate
- BTPS
body temperature, ambient pressure, saturated
-
EO
2
oxygen extraction
- EWL
evaporative water loss
-
f
R
ventilation frequency
- RH
relative humidity
- RHL
respiratory heat loss
- SEM
standard error of the mean
- SNK
student-Newman-Keuls multiple range test
- STPD
standard temperature and pressure, dry
-
T
a
ambient temperatures(s)
-
T
b
body temperature(s)
-
T
ex
expired air temperature(s)
-
T
rh
chamber excurrent air temperature
-
V
J
ventilation
-
VO2
oxygen consumption
-
V
T
tidal volume
-
V/Q
air ventilation to blood perfusion ratio 相似文献
20.
Gusztak RW Macarthur RA Campbell KL 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2005,175(2):87-95
Rates of O2 consumption and CO2 production, telemetered body temperature (Tb) and activity level were recorded from adult and subadult water shrews (Sorex palustris) over an air temperature (Ta) range of 3–32°C. Digesta passage rate trials were conducted before metabolic testing to estimate the minimum fasting time required for water shrews to achieve a postabsorptive state. Of the 228 metabolic trials conducted on 15 water shrews, 146 (64%) were discarded because the criteria for inactivity were not met. Abdominal Tb of S. palustris was independent of Ta and averaged 38.64±0.07°C. The thermoneutral zone extended from 21.2°C to at least 32°C. Our estimate of the basal metabolic rate for resting, postabsorptive water shrews (96.88±2.93 J g–1 h–1 or 4.84±0.14 ml O2 g–1 h–1) was three times the mass-predicted value, while their minimum thermal conductance in air (0.282±0.013 ml O2 g–1 h–1) concurred with allometric predictions. The mean digesta throughput time of water shrews fed mealworms (Tenebrio molitor) or ground meat was 50–55 min. The digestibility coefficients for metabolizable energy (ME) of water shrews fed stickleback minnows (Culaea inconstans) and dragonfly nymphs (Anax spp. and Libellula spp.) were 85.4±1.3% and 82.8±1.1%, respectively. The average metabolic rate (AMR) calculated from the gas exchange of six water shrews at 19–22°C (208.0±17.0 J g–1 h–1) was nearly identical to the estimate of energy intake (202.9±12.9 J g–1 h–1) measured for these same animals during digestibility trials (20°C). Based on 24-h activity trials and our derived ME coefficients, the minimum daily energy requirement of an adult (14.4 g) water shrew at Ta = 20°C is 54.0 kJ, or the energetic equivalent of 14.7 stickleback minnows. 相似文献