Photoperiodic effects on body size and energetics of the collared lemming, Dicrostonyx groenlandicus

1988 ◽  
Vol 66 (4) ◽  
pp. 835-841 ◽  
Author(s):  
P. S. Reynolds ◽  
D. M. Lavigne
Keyword(s):  
Body Size ◽  
Ambient Temperature ◽  
Core Temperature ◽  
Thermal Conductance ◽  
Seasonal Patterns ◽  
Metabolic Rates ◽  
Ambient Temperatures ◽  
Thermoneutral Zone ◽  
Dicrostonyx Groenlandicus ◽  
Phylogenetic Adaptation

Resting metabolic rates of adult collared lemmings, Dicrostonyx groenlandicus, acclimated from weaning to either long, "summer" (22L:2D) or short, "winter" (2L:22D) photoperiod at 15 °C were examined as a function of ambient temperature. Winter morphs were significantly heavier than summer morphs (73.8 ± 7.7 (SD) and 54.5 ± 7.2 (SD) g, respectively). However, there were no differences in mass-specific metabolic rates between treatments at 15 and 20 °C. At low ambient temperatures (0 and −10 °C), metabolic rates of summer morphs were significantly higher than those of winter morphs, indicating a shift in the thermoneutral zone with photoperiod acclimation. There were no significant differences in core temperature between morphs at any ambient temperature. Thermal conductance of winter morphs was significantly lower (0.05 mL O2 (g∙h∙°C)−1) than that of summer morphs (0.09 mL O2 (g∙h∙°C)−1). Comparisons with other myomorph rodents do not support the contention that lemmings have unusually high metabolic rates. However, minimal thermal conductances of lemmings were much lower than expected on the basis of body size. These data suggest that although lemmings may differ in seasonal patterns of energetics from other microtines, there is little evidence to support the assertion that high rates of metabolism are characteristic of all microtines, or that observed basal rates represent a phylogenetic adaptation to cold.

Thermoregulatory control during pregnancy and lactation in rats

1997 ◽  
Vol 83 (3) ◽  
pp. 837-844 ◽  
Author(s):  
Heather L. Eliason ◽  
James E. Fewell
Keyword(s):  
Oxygen Consumption ◽  
Ambient Temperature ◽  
Thermal Conductance ◽  
Thermoregulatory Response ◽  
Linear Temperature ◽  
Metabolic Chamber ◽  
Linear Temperature Gradient ◽  
Thermoneutral Zone ◽  
Pregnancy And Lactation ◽  
Near Term

Eliason, Heather L., and James E. Fewell.Thermoregulatory control during pregnancy and lactation in rats. J. Appl. Physiol. 83(3): 837–844, 1997.—Although the mechanisms remain unknown, maternal core temperature (Tc) decreases near term of pregnancy and is increased throughout lactation in rats. The purpose of our present experiments was to determine whether pregnancy and lactation shift the thermoneutral zone of rats and to investigate whether the changes in maternal Tcduring pregnancy and lactation result from “forced” or “regulated” thermoregulatory responses. Conscious, chronically instrumented nonpregnant and pregnant and lactating rats were studied both in a thermocline (a chamber with a linear temperature gradient from 12 to 36°C) and in a metabolic chamber to determine the influence of pregnancy and lactation on selected ambient temperature as well as the thermoregulatory response to changes in ambient temperature. We found that selected ambient temperature, oxygen consumption, and thermal conductance did not change in rats studied in a thermocline as Tc decreased near term of pregnancy. There was, however, a downward shift in the thermoneutral zone of rats studied in a metabolic chamber near term of pregnancy. During lactation, selected ambient temperature decreased in rats studied in a thermocline as oxygen consumption and Tc increased. The thermoneutral zone of lactating rats was not different from that of nonpregnant animals. Thus our data provide evidence that the decrease in Tc near term of pregnancy in rats results from a regulated thermoregulatory response, whereas the increase in Tc during lactation results from a forced thermoregulatory response.

The metabolic rate and thermal conductance of the eastern barred bandicoot (Perameles gunnii) at different ambient temperatures

2003 ◽  
Vol 51 (6) ◽  
pp. 603 ◽  
Author(s):  
M. P. Ikonomopoulou ◽  
R. W. Rose
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Metabolic Rate ◽  
Thermal Conductance ◽  
The Body ◽  
High Metabolic Rate ◽  
Ambient Temperatures ◽  
Reduced Body ◽  
Thermoneutral Zone ◽  
Reproductive Females

We investigated the metabolic rate, thermoneutral zone and thermal conductance of the eastern barred bandicoot in Tasmania. Five adult eastern barred bandicoots (two males, three non-reproductive females) were tested at temperatures of 3, 10, 15, 20, 25, 30, 35 and 40°C. The thermoneutral zone was calculated from oxygen consumption and body temperature, measured during the daytime: their normal resting phase. It was found that the thermoneutral zone lies between 25°C and 30°C, with a minimum metabolic rate of 0.51 mL g–1 h–1 and body temperature of 35.8°C. At cooler ambient temperatures (3–20°C) the body temperature decreased to approximately 34.0°C while the metabolic rate increased from 0.7 to 1.3 mL g–1�h–1. At high temperatures (35°C and 40°C) both body temperature (36.9–38.7°C) and metabolic rate (1.0–1.5 mL g–1 h–1) rose. Thermal conductance was low below an ambient temperature of 30°C but increased significantly at higher temperatures. The low thermal conductance (due, in part, to good insulation, a reduced body temperature at lower ambient temperatures, combined with a relatively high metabolic rate) suggests that this species is well adapted to cooler environments but it could not thermoregulate easily at temperatures above 30°C.

Energy utilization in the laying hen in relation to ambient temperature

1973 ◽  
Vol 81 (1) ◽  
pp. 173-177 ◽  
Author(s):  
R. H. Davis ◽  
O. E. M. Hassan ◽  
A. H. Sykes
Keyword(s):  
Ambient Temperature ◽  
Energy Intake ◽  
Heat Production ◽  
Egg Production ◽  
Energy Utilization ◽  
Ambient Temperatures ◽  
Thermoneutral Zone ◽  
Energy Retention ◽  
The Difference ◽  
Energy Balances

SummaryEnergy balances have been determined, using the comparative slaughter procedure, over 3-week periods on groups of laying hens kept at ambient temperatures of 7·2, 15·6, 23·9, 29·4 and 35 °C.Energy intake declined as the environment became warmer (kcal ME/kg¾/day = 203· 1·13°C); heat production, as measured by the difference between energy intake and energy retention, also declined with increasing ambient temperature (kcal/kg¾/day = 151 – 1·11°C). There was a linear relationship between heat production and ambient temperature with no thermoneutral zone or critical temperature.The energy available for egg production remained almost constant at 50 kcal/kg¾/day equivalent to a rate of egg production of 82% at each ambient temperature.

The metabolic rates of newborn pigs in relation to floor insulation and ambient temperature

1971 ◽  
Vol 13 (2) ◽  
pp. 303-313 ◽  
Author(s):  
D. B. Stephens
Keyword(s):  
Body Weight ◽  
Oxygen Consumption ◽  
Ambient Temperature ◽  
Regression Coefficients ◽  
Metabolic Rates ◽  
Similar Treatment ◽  
Concrete Floor ◽  
Ambient Temperatures ◽  
Newborn Pigs ◽  
Floor Material

SUMMARY1. The metabolic rates of 58 individual piglets kept either on a straw or on a concrete floor at ambient temperatures near to 10°, 20° or 30°C have been measured with ages ranging from newborn to 9 days, and body weight from 1·0 to 3·2 kg. The oxygen consumption was measured on each floor material at the chosen ambient temperature thus allowing paired comparisons for each animal.2. In comparison with the concrete floor, oxygen consumption on straw was reduced by 18% at 10°C, 27% at 20°C and by 12% at 30°C for pigs 2 to 9 days old. The regression coefficients of mean log (oxygen consumption) on log (body weight) were around 0·66 at 10° and 20°C. At 30°C the value was 0·99 ± 0·14. The regression coefficients were not significantly affected by the presence of a straw floor showing that its effect did not vary with body weight. Corresponding values foi piglets below 24 hours of age were 17% at 10°C, 27% at 20°C and 22% at 30°C ambient temperature.3. Moving a piglet on to a straw floor at 10°C had the same thermal effect as raising the ambient temperature to 18°C. Similar treatment at 30°C was equivalent to raising the ambient temperature to 32°C.4. Lowering ambient temperature to increase the temperature gradient between the homeothermic body of the piglet and the environment progressively increased heat loss in all cases. There was a concomitant decrease in the calculated conductance between core and environment which was more pronounced for the piglets lying on the concrete floor.

Temperature regulation and cold acclimation in the golden hamster

1965 ◽  
Vol 20 (3) ◽  
pp. 405-410 ◽  
Author(s):  
Hermann Pohl
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Ambient Temperature ◽  
Cold Acclimation ◽  
Heat Production ◽  
Golden Hamster ◽  
Thermal Conductance ◽  
Muscular Activity ◽  
The Body ◽  
Ambient Temperatures

Characteristics of cold acclimation in the golden hamster, Mesocricetus auratus, were 1) higher metabolic rate at -30 C, 2) less shivering when related to ambient temperature or oxygen consumption, and 3) higher differences in body temperature between cardiac area and thoracic subcutaneous tissues at all ambient temperatures tested, indicating changes in tissue insulation. Cold-acclimated hamsters also showed a rise in temperature of the cardiac area when ambient temperature was below 15 C. Changes in heat distribution in cold-acclimated hamsters suggest higher blood flow and heat production in the thoracic part of the body in the cold. The thermal conductance through the thoracic and lumbar muscle areas, however, did not change notably with lowering ambient temperature. Marked differences in thermoregulatory response to cold after cold acclimation were found between two species, the golden hamster and the thirteen-lined ground squirrel, showing greater ability to regulate body temperature in the cold in hamsters. hibernator; oxygen consumption— heat production; body temperature — heat conductance; muscular activity — shivering; thermoregulation Submitted on July 6, 1964

scholarly journals Collective thermoregulation in bee clusters

2014 ◽  
Vol 11 (91) ◽  
pp. 20131033 ◽  
Author(s):  
Samuel A. Ocko ◽  
L. Mahadevan
Keyword(s):  
Ambient Temperature ◽  
Core Temperature ◽  
Continuum Model ◽  
External Temperature ◽  
Ambient Temperatures ◽  
Advection Diffusion ◽  
Central Controller ◽  
Buoyancy Driven Flows ◽  
Dense Cluster

Swarming is an essential part of honeybee behaviour, wherein thousands of bees cling onto each other to form a dense cluster that may be exposed to the environment for several days. This cluster has the ability to maintain its core temperature actively without a central controller. We suggest that the swarm cluster is akin to an active porous structure whose functional requirement is to adjust to outside conditions by varying its porosity to control its core temperature. Using a continuum model that takes the form of a set of advection–diffusion equations for heat transfer in a mobile porous medium, we show that the equalization of an effective ‘behavioural pressure’, which propagates information about the ambient temperature through variations in density, leads to effective thermoregulation. Our model extends and generalizes previous models by focusing the question of mechanism on the form and role of the behavioural pressure, and allows us to explain the vertical asymmetry of the cluster (as a consequence of buoyancy-driven flows), the ability of the cluster to overpack at low ambient temperatures without breaking up at high ambient temperatures, and the relative insensitivity to large variations in the ambient temperature. Our theory also makes testable hypotheses for the response of the cluster to external temperature inhomogeneities and suggests strategies for biomimetic thermoregulation.

Sleep-waking pattern and body temperature in hypoxia at selected ambient temperatures

1984 ◽  
Vol 57 (5) ◽  
pp. 1564-1568 ◽  
Author(s):  
B. Hale ◽  
D. Megirian ◽  
M. J. Pollard
Keyword(s):  
Body Temperature ◽  
Ambient Temperature ◽  
Core Temperature ◽  
Ambient Temperatures ◽  
State Changes ◽  
Maximum Minimum ◽  
Mild Hypoxia ◽  
Low Ambient Temperature

We studied the effect of mild hypoxia (15% O2) and low ambient temperature (Ta = 15 degrees C) on the rat's sleep-waking pattern (SWP) and maximum-minimum core temperature (max-min Tb). Mild hypoxia at neutral Ta (29 degrees C) disrupted the SWP in the same way as low Ta during normoxia: both affected the pattern of frequency of state changes (P less than 0.01), not the pattern of epoch durations. Mild hypoxia and low Ta together caused a degree of disruption of the SWP which was the sum of each alone, i.e., additive. Although both mild hypoxia and low Ta significantly depressed max-min Tb, low Ta exerted a greater effect than mild hypoxia. Together they further depressed max-min Tb in an additive way. We conclude that mild hypoxia disrupts the rat's SWP independent of central thermoregulatory mechanisms at neutral Ta, that the effects of mild hypoxia and low Ta on the SWP are additive at the stimulus levels used, and that Ta, not inspired O2, determines Tb.

Factors producing elevated core temperature in spontaneously hypertensive rats

1987 ◽  
Vol 63 (2) ◽  
pp. 740-745 ◽  
Author(s):  
M. G. Collins ◽  
W. S. Hunter ◽  
C. M. Blatteis
Keyword(s):  
Core Temperature ◽  
Spontaneously Hypertensive Rats ◽  
Spontaneously Hypertensive Rat ◽  
Thermal Conductance ◽  
Evaporative Heat Loss ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Ambient Temperatures ◽  
Metabolic Heat ◽  
Wistar Kyoto

Core temperature (Tco) of the spontaneously hypertensive rat (SHR) is consistently higher by approximately 1 degree C than that of normotensive controls. To analyze factors producing the elevated Tco, mean skin temperature (Tsk), metabolic heat production (M), respiratory evaporative heat loss (Eres), effective tissue thermal conductance (K), systolic blood pressure (BP), and Tco were determined in eight male SHR and nine male normotensive Wistar-Kyoto (WKY) rats habituated to rest quietly in neck stock restraint while exposed to ambient temperatures (Ta) of 12.5, 17, 23, 28.5, 32, 34, and 35 degrees C. At all temperatures steady-state BP, Tco, and M were higher for SHR's than for WKY's. SHR's could maintain thermal balance up to Ta 32 degrees C, and WKY's up to 34 degrees C. Eres from SHR's was greater than from WKY's at Ta of 12.5, 17, and 28.5 degrees C. K of SHR's was not different from or was higher than K of WKY's, and K for both groups was 2.6 times greater at Ta 32 degrees C than at 17 degrees C. These results indicate that the high Tco of SHR's is due to increased M uncompensated by increased K or Eres.

scholarly journals Effects of Estradiol on the Thermoneutral Zone and Core Temperature in Ovariectomized Rats

Endocrinology ◽  
2010 ◽  
Vol 151 (3) ◽  
pp. 1187-1193 ◽  
Author(s):  
Penny A. Dacks ◽  
Naomi E. Rance
Keyword(s):  
Heat Loss ◽  
Core Temperature ◽  
Ovariectomized Rats ◽  
Neural Pathways ◽  
Estradiol Treatment ◽  
Ambient Temperatures ◽  
Thermoneutral Zone ◽  
Estrogen Withdrawal ◽  
Estradiol 17Β ◽  
Loss Mechanisms

Hot flushes represent a disorder of central thermoregulation characterized by the episodic activation of heat loss mechanisms. Although flushes are associated with estrogen withdrawal, there is little understanding of the effects of estrogen on thermoregulation in any species. It has been proposed that hormone withdrawal increases the sensitivity of hypothalamic neural pathways that control heat dissipation effectors. If so, we predicted that ovariectomized rats without estradiol treatment would activate tail skin vasodilatation (a major heat loss effector) at lower ambient temperatures and thereby lower the thermoneutral zone. The thermoneutral zone, defined as the range of ambient temperatures in which thermoregulation is achieved only by sensible (dry) heat loss, was evaluated based on properties of skin vasomotion. Core and tail skin temperatures were recorded in ovariectomized rats (with and without estradiol-17β) exposed to ambient temperatures from 13 to 34 C in an environmental chamber. Rats without estradiol exhibited increased skin vasodilatation and a shift in the thermoneutral zone to lower ambient temperatures. Moreover, the ambient temperature threshold for skin vasodilatation was significantly lower in rats without estradiol treatment. At most ambient temperatures, average core temperature was unaffected by estradiol. However, at ambient temperatures of 32.5 C and above, untreated ovariectomized rats exhibited higher core temperatures compared with estradiol-treated rats. Thus, estradiol-17β treatment enhanced the maintenance of core temperature during heat exposure. These findings support the hypothesis that estrogen withdrawal increases the sensitivity of thermoregulatory neural pathways and modifies the activation of heat loss mechanisms.

Thermoregulatory, metabolic and ventilatory physiology of the western barred bandicoot (Perameles bougainville bougainville) in summer and winter

2006 ◽  
Vol 54 (1) ◽  
pp. 15 ◽  
Author(s):  
Alexander N. Larcombe ◽  
Philip C. Withers
Keyword(s):  
Body Temperature ◽  
Metabolic Rate ◽  
Ambient Temperature ◽  
Thermal Conductance ◽  
Carbon Dioxide Production ◽  
Minute Volume ◽  
Evaporative Water ◽  
Ambient Temperatures ◽  
Time Of Year ◽  
High Basal Metabolic Rate

The metabolic, thermoregulatory and ventilatory physiology of western barred bandicoots (Perameles bougainville bougainville), measured in the laboratory during summer and winter at ambient temperatures of 10 and 30°C, is relatively unusual for a peramelid marsupial. It has a low thermoneutral body temperature (33.7 ± 0.2°C), a very high basal metabolic rate (0.68 ± 0.03 mL O2 g–1 h–1 at ambient temperature = 30°C), low respiratory exchange ratios (often less than 0.7) and a high thermal conductance, reflecting its high oxygen consumption rate and low body temperature. Ventilatory frequency and tidal volume were variable between seasons, although minute volume and oxygen extraction efficiency were not. Minute volume of the western barred bandicoot was higher than expected, reflecting its high metabolic rate. Time of year (i.e. season) had an effect on some aspects of metabolic, thermoregulatory and ventilatory physiology (carbon dioxide production, respiratory exchange ratio, total evaporative water loss), but this effect was not as substantial nor as general as the effect of ambient temperature.

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