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Free-ranging, juvenile thirteen-lined ground squirrels (Ictidomys tridecemlineatus) in southwestern Michigan were fitted in late summer or fall with external skin-temperature loggers. Data were obtained the following spring for five males and three females. During the heterothermal period, all squirrels exhibited 11-29 prolonged ([bar.x] = 9.4 d) torpor bouts punctuated by typically brief ([bar.x] = 14.3 h) arousal bouts, with mean monthly torpor bouts becoming longer and deeper until Feb. and reversing thereafter. Torpor-bout duration increased as minimum skin and soil temperatures decreased. On average, males initiated the first torpor bout later in fall, terminated the last torpor bout significantly earlier in spring and thus spent less time in the heterothermal period than did females. Three males displayed relatively short torpor bouts and long arousal bouts as they approached the end of hibernation. Squirrels gained weight variably in fall and spring, and one female lost 39% of body mass during hibernation., INTRODUCTION Hibernation has been intensively studied in ground-dwelling squirrels (family Sciuridae) within the tribe Marmotini. In captivity, marmotine and other mammalian hibernators studied at controlled ambient temperatures in cold chambers [...]

For organisms living in the intertidal zone, temperature is an important selective agent that can shape species distributions and drive phenotypic variation among populations. Littorinid snails, which occupy the upper limits of rocky shores and estuaries worldwide, often experience extreme high temperatures and prolonged aerial emersion during low tides, yet their robust physiology--coupled with morphological and behavioral traits--permits these gastropods to persist and exert strong grazing control over algal communities. We use a mechanistic heat-budget model to compare the effects of behavioral and morphological traits on the body temperatures of five species of littorinid snails under natural weather conditions. Model predictions and field experiments indicate that, for all five species, the relative contribution of shell color or sculpturing to temperature regulation is small, on the order of 0.2-2 °C, while behavioral choices such as removing the foot from the substratum or reorienting the shell can lower body temperatures by 2-4 °C on average. Temperatures in central California rarely exceeded the thermal tolerance limits of the local littorinid species during the study period, but at sites where snails are regularly exposed to extreme high temperatures, the functional significance of the tested traits may be important. The mechanistic approach used here provides the ability to gauge the importance of behavioral and morphological traits for controlling body temperature as species approach their physiological thresholds., Introduction Within the narrow band of habitat between the low and high tidemarks on seashores, the distribution of individual species and the structure of ecological communities are dictated by a [...]

A 120-d feedlot study using 164 Angus steers (BW = 396.7 [+ or -] 7.0 kg) was undertaken in Queensland Australia (24[degrees]84' S, 149[degrees]78' N) to determine the effect of shade on body temperature ([T.sub.B]) and performance. Cattle were allocated to 20 pens: 16 with an area of 144 [m.sup.2] (8 steers/pen) and 4 with an area of 168 [m.sup.2] (9 steers/pen). Treatments (10 pens/treatment) were unshaded (NS) vs. shaded (SH). Shade (3.3 [m.sup.2]/ steer) was provided by 80% solar block shade cloth. Before the study (d -31), 63 steers were implanted (between the internal abdominal muscle and the peritoneum at the right side flank) with a [T.sub.B] transmitter. Within each pen, 3 steers had a [T.sub.B] transmitter. Individual [T.sub.B] was obtained every 30 min. The cattle were fed a feedlot diet and had ad libitum access to water. Water usage and DMI were recorded daily on a pen basis. Average daily gain and G:F were calculated on a pen basis. Climatic variables were obtained from an onsite weather station every 30 min. Individual panting scores (PS) were obtained daily at 0600, 1200, and 1600 h. From these, mean PS (MPS) were calculated for each pen. At slaughter (d 121), individual HCW, loin muscle area (LMA), rump fat depth (PS), 12th-rib fat depth, and marbling score were obtained. Mean TB was not affected (P > 0.05) by treatment (SH = 39.58[degrees]C; NS = 39.60[degrees]C). However, during a 21-d heat wave when cattle were exposed to a mean ambient temperature ([T.sub.AM]) > 30[degrees]C for 8 h each d ([T.sub.AM] between 0800 and 1800 h = 29.7[degrees]C, and 23.4[degrees]C between 1830 and 0730 h), the [T.sub.B] of SH steers (40.41 [+ or -] 0.10[degrees]C) was less (P < 0.01) than the TB of NS steers (41.14 [+ or -] 0.10[degrees]C). During this period, pen-MPS were greater (P < 0.05) for the NS cattle at all observation times. Over the first 6 d of the heat wave, MPS of NS steers at 1200 h was 2.47 (P < 0.01) vs. 1.39 for SH steers. Hip height, DMI, ADG, and G:F were greater (P < 0.05) for SH cattle. Exit BW (final BW) of SH steers (596.1 kg) was greater (P < 0.05) when compared with NS steers (578.6 kg). During the heat wave, DMI was 51% less for NS steers and 39% less for SH steers when compared with the pre-heat wave period (P < 0.01). The HCW of SH steers (315.4 [+ or -] 0.8 kg) was greater (P < 0.05) than for NS steers (321.4 [+ or -] 0.8 kg). No treatment differences (P > 0.05) were found for LMA, P8, or marbling score. Access to shade improved (P < 0.05) ADG and G:F, increased HCW, and decreased MPS; however, shade did not completely eliminate the impact of high heat load. Key words: body temperature, Bos taurus, shade doi: 10.2527/jas.2010-2987

Cold environments are challenging for small endotherms because they must increase heat production to compensate for increased heat loss to the environment. Mammals that endure cold without entering torpor may have thicker fur and a lower body temperature ([T.sub.b]) than those in warm environments to save energy. Activity levels also may be reduced in the cold. We aimed to determine whether activity level, exposure to chronic cold, or an interaction between the 2 could reduce the [T.sub.b] of an endotherm. Wild bush rats (Rattus fuscipes) were brought into captivity and acclimated to cold (12[degrees]C) or warm (22[degrees]C) ambient temperatures and were either sedentary or exercised. Daily exercise increased maximum [T.sub.b] in cold-acclimated bush rats but also decreased minimum [T.sub.b]. Mean ([+ or -] SE) daily [T.sub.b] was significantly lower in cold-acclimated bush rats (sedentary: 36.5[degrees]C [+ or -] 0.1[degrees]C; exercised: 36.4[degrees]C [+ or -] 0.2[degrees]C) compared to warm-acclimated bush rats (sedentary: 37.3[degrees]C [+ or -] 0.2[degrees]C; exercised: 37.0[degrees]C [+ or -] 0.1[degrees]C). Body temperature decreased significantly over the time of cold acclimation. Thicker fur and lower [T.sub.b]s in cold-acclimated bush rats conferred an energy saving equivalent to 11% of daily food intake in exercised rats and 22% of daily food intake in sedentary rats. The lower [T.sub.b]s recorded in some small mammals in winter are not necessarily due to lower levels of activity but can result from a regulated reduction in [T.sub.b] in response to cooler ambient temperatures. DOI: 10.1644/10-MAMM-A-003.1. Key words: body temperature, bush rat, exercise, fur thickness, heat generation model, Rattus fuscipes, thermal acclimation

The Brazilian free-tailed bat (Tadarida brasiliensis) experiences challenging thermal conditions while roosting in hot caves, flying during warm daylight conditions, and foraging at cool high altitudes. Using thermal infrared cameras, we identified hot spots along the flanks of free-ranging Brazilian free-tailed bats, ventral to the extended wings. These hot spots are absent in syntopic cave myotis (Myotis velifer), a species that forages over relatively short distances, and does not engage in long-distance migration. We hypothesized that the hot spots, or 'radiators,' on Brazilian free-tailed bats may be adaptations for migration, particularly in this long-distance, high-flying species. We examined the vasculature of radiators on Brazilian free-tailed bats with transillumination to characterize the unique arrangements of arteries and veins that are positioned perpendicular to the body in the proximal region of the wing. We hypothesized that these radiators aid in maintaining heat balance by flushing the uninsulated thermal window with warm blood, thereby dissipating heat while bats are flying under warm conditions, but shunting blood away and conserving heat when they are flying in cooler air at high altitudes. We also examined fluid-preserved specimens representing 122 species from 15 of 18 chiropteran families and radiators appeared present only in species in the family Molossidae, including both sedentary and migratory species and subspecies. Thus, the radiator appears to be a unique trait that may facilitate energy balance and water balance during sustained dispersal, foraging, and long-distance migration. doi: 10.1093/icb/icq033

This study investigated whether the estimation error of volume-weighted mean body temperature ([DELTA][[bar.T].sub.b]) using changes in core and skin temperature can be accounted for using personal and environmental parameters. Whole body calorimetry was used to directly measure [DELTA][[bar.T].sub.b] in an Experimental group (EG) of 36 participants (24 males, 12 females) and a Validation group (VG) of 20 (9 males, 11 females) throughout 90 min of cycle ergometry at 40[degrees]C, 30% relative humidity (RH) (n = 9 EG, 5 VG); 30[degrees]C, 30% RH (n = 9 EG, 5 VG); 30[degrees]C, 60% RH (n = 9 EG, 5 VG); and 24[degrees]C, 30% RH (n = 9 EG, 5 VG). The core of the two-compartment thermometry model was represented by rectal temperature and the shell by a 12-point mean skin temperature ([DELTA][[bar.T].sub.sk]). The estimation error ([X.sub.o]) between [DELTA][[bar.T].sub.b] from calorimetry and [DELTA][[bar.T].sub.b] from thermometry using core/shell weightings of 0.66/0.34, 0.79/0.21, and 0.90/0.10 was calculated after 30, 60, and 90 min of exercise, respectively. The association between Xo and the individual variation in metabolic heat production (M - W), body surface area (BSA), body fat percentage (%fat), and body surface area-to-mass ratio (BSA/BM) as well as differences in environmental conditions (Oxford index) in the EG data were assessed using stepwise linear regression. At all time points and with all core/shell weightings tested, M - W, BSA, and Oxford index independently correlated significantly with the residual variance in [X.sub.o], but %fat and BSA/BM did not. The subsequent regression models were used to predict the thermometric estimation error ([X.sub.o-pred]) for each individual in the VG. The value estimated for [X.sub.o-pred] was then added to the [DELTA][[bar.T].sub.b] estimated using the two-compartment thermometry models yielding an adjusted estimation ([DELTA][[bar.T].sub.b_adj]) for the individuals in the VG. When comparing [DELTA][[bar.T].sub.b_adj] to the [DELTA][[bar.T].sub.b] derived from calorimetry in the VG, the best performing model used a core/shell weighting of 0.66/0.34 describing 74%, 84%, and 82% of the variation observed in [DELTA][[bar.T].sub.b] from calorimetry after 30, 60, and 90 min, respectively. body heat storage; calorimetry; core temperature; heat stress; skin temperature doi: 10.1152/ajpregu.00546.2009.

The typical core temperature ([T.sub.c]) profile displayed during heatstroke (HS) recovery consists of initial hypothermia followed by delayed hyperthermia. Anecdotal observations led to the conclusion that these [T.sub.c] responses represent thermoregulatory dysfunction as a result of brain damage. We hypothesized that these [T.sub.c] responses are mediated by a change in the temperature setpoint. [T.sub.c] ([+ or -] 0.1 [degrees]C; radiotelemetry) of male C57BL/6J mice was monitored while they were housed in a temperature gradient with ambient temperature ([T.sub.a]) range of 20-39 [degrees]C to monitor behaviorally selected [T.sub.a] ([T.sub.s]) or an indirect calorimeter ([T.sub.a] = 25 [degrees]C) to monitor metabolism ([Vo.sub.2]) and calculate respiratory exchange ratio (RER). Responses to mild and severe HS (thermal area 249.6 [+ or -] 18.9 vs. 299.4 [+ or -] 19.3 [degrees]C x min, respectively) were examined through 48 h of recovery. An initial hypothermia following mild HS was associated with warm [T.sub.s] (~32 [degrees]C), ~35% [Vo.sub.2] decrease, and RER ~0.71 that indicated reliance on fatty acid oxidation. After 24 h, mild HS mice developed hyperthermia associated with warm [T.sub.s] (~32 [degrees]C), ~20% Vo2 increase, and RER ~0.85. Severe HS mice appeared poikilothermic-like in the temperature gradient with [T.sub.c] similar to [T.sub.s] (~20 [degrees]C), and these mice failed to recover from hypothermia and develop delayed hyperthermia. Cellular damage (hematoxylin and eosin staining) was undetectable in the hypothalamus or other brain regions in severe HS mice. Overall, decreases and increases in [T.sub.c] were associated with behavioral and autonomic thermoeffectors that suggest HS elicits anapyrexia and fever, respectively. Taken together, [T.sub.c] responses of mild and severe HS mice suggest a need for reinterpretation of the mechanisms of thermoregulatory control during recovery. heat stress; fever; hypothermia; poikilothermia; metabolism doi: 10.1152/ajpregu.00309.2009.

What the body temperature and thermoregulation processes of extinct vertebrates were are central questions for understanding their ecology and evolution. The thermophysiologic status of the great marine reptiles is still unknown, even though some studies have suggested that thermoregulation may have contributed to their exceptional evolutionary success as apex predators of Mesozoic aquatic ecosystems. We tested the thermal status of ichthyosaurs, plesiosaurs, and mosasaurs by comparing the oxygen isotope compositions of their tooth phosphate to those of coexisting fish. Data distribution reveals that these large marine reptiles were able to maintain a constant and high body temperature in oceanic environments ranging from tropical to cold temperate. Their estimated body temperatures, in the range from 35[degrees] [+ or -] 2[degrees]C to 39[degrees] [+ or -] 2[degrees]C, suggest high metabolic rates required for predation and fast swimming over large distances offshore. 10.1126/science.1187443

Neurons in the rostral raphe pallidus (RPa) play an essential role in the regulation of sympathetically mediated metabolism and thermogenesis in brown adipose tissue (BAT). The presence of serotonergic neurons in the RPa that are retrogradely labeled following pseudorabies virus injections into BAT suggests that these neurons play a role in the regulation of BAT. In urethane/chloralose-anesthetized rats, whole body cooling decreased skin (-5.7 [+ or -] 2.3[degrees]C) and core (-1.3 [+ or -] 0.2[degrees]C) temperatures and resulted in an increase in BAT sympathetic nerve activity (SNA; +1,026 [+ or -] 344% of baseline activity). Serial microinjections of the 5-hydroxytryptamine (5-HT) receptor antagonist, methysergide (1.2 nmol/site), but not saline vehicle, into the intermediolateral cell column (IML) in spinal segments T2-T5 markedly attenuated the cooling-evoked increase in BAT SNA (remaining area under the curve, AUC: 36 [+ or -] 9% of naive cooling response). Microinjections of the [5-HT.sub.1A] receptor antagonist, WAY-100635 (1.2 nmol/site), or the [5-HT.sub.7] receptor antagonist, SB-269970 (1.2 nmol/site), into the T2-T5 IML also attenuated the cold-evoked increase in BAT SNA (remaining activity at peak inhibition: 47 [+ or -] 8% and 39 [+ or -] 12% of the initial cold-evoked response, respectively). The increases in BAT SNA evoked by microinjection of N-methyl-D-aspartate (NMDA) ( 12 pmol) or bicuculline (30 pmol) into the RPa were attenuated following microinjections of methysergide, but not saline vehicle, into the T2-T5 IML (NMDA remaining AUC, 64 [+ or -] 13% of naive response: bicuculline remaining AUC, 52 [+ or -] 5% of naive response). These results are consistent with our earlier demonstration of a potentiating effect of 5-HT within the IML on BAT SNA and indicate that activation of [5-HT.sub.1A] and [5-HT.sub.7] receptors in the spinal cord contributes to increases in BAT SNA and thermogenesis. thermoregulation; sympathetic premotor neurons; raphe; serotonin; metabolism doi:10.1152/ajpregu.00614.2009

The current study investigated the effects of a pre-cooling intervention on physiological and performance responses to team-sport training in the heat. Seven male lacrosse players performed a familiarization session and 2 randomized, counterbalanced sessions consisting of a 30-minute intermittent-sprint conditioning session. Prior to the sessions, players performed a 20-minute mixed-method, part-body cooling intervention (consisting of cooling vests, cold towels to the neck, and ice packs to the quadriceps) or no cooling intervention. Performance was determined from collection of 1 Hz global positioning system (GPS) data and analyzed for distance and speed. Prior to, during, and following the sessions, core temperature, heart rate, rating of perceived exertion (RPE), and thermal sensation scale (TSS) were measured; additionally, a venous blood sample was collected before and after each session for measurement of interleukin-6 (IL-6), insulin-like growth factor (IGF-1) and insulin-like growth factor-binding protein3 (IGF-BP3). Results indicated that a greater distance was covered during the pre-cooling condition (3.35 [+ or -] 0.20 vs. 3.11 [+ or -] 0.13 km; p = 0.05). Further, most of this improvement was evident from a greater distance covered during moderate intensities of 7 to 14 km/h (2.28 [+ or -] 0.18 vs. 2.00 [+ or -] 0.24 km; p = 0.05). Peak speeds and very-high-intensity efforts (20 km/h [+ or -]) were not different between conditions (p > 0.05). The increase in core temperature was blunted following cooling, with a lower core temperature throughout the cooling session (38.8 [+ or -] 0.3 vs. 39.3 [+ or -] 0.4[degrees]C; p < 0.05). However, there were no differences in heart rate, RPE, TSS, IL-6, IGF-1, or IGF-BP3 between conditions (p > 0.05). Accordingly, the use of a mixed-method, part-body cooling intervention prior to an intermittent-sprint training session in the heat can assist in reducing thermoregulatory load and improve aspects of training performance for team sports. KEY WORDS pacing, intermittent-sprint exercise, thermoregulation

Primary human aging may be associated with augmented Rho kinase (ROCK)-mediated contraction of vascular smooth muscle and ROCK-mediated inhibition of nitric oxide synthase (NOS). We hypothesized that the contribution of ROCK to reflex vasoconstriction (VC) is greater in aged skin. Cutaneous VC was elicited by 1) whole body cooling [mean skin temperature ([T.sub.sk]) = 30.5[degrees]C] and 2) local norepinephrine (NE) infusion (1 x [10.sup.-6] M). Four microdialysis fibers were placed in the forearm skin of eight young (Y) and eight older (O) subjects for infusion of 1) Ringer solution (control), 2) 3 mM fasudil (ROCK inhibition), 3) 20 mM [N.sup.G]-nitro-L-arginine methyl ester (NOS inhibition), and 4) both ROCK + NOS inhibitors. Red cell flux was measured by laser-Doppler flowmetry over each site. Cutaneous vascular conductance (CVC) was calculated as flux/mean arterial pressure and normalized to baseline CVC (%[DELTA][CVC.sub.baseline]). VC was reduced at the control site in O during cooling (Y, -34 [+ or -] 3; and O, -18 [+ or -] 3%[DELTA][CVC.sub.baseline]; P < 0.001) and NE infusion (Y, -53 [+ or -] 4, and O, -41 [+ or -] 9%[DELTA][CVC.sub.baseline]; P = 0.006). Fasudil attenuated VC in both age groups during mild cooling; however, this reduction remained only in O but not in Y skin during moderate cooling (Y, -30 [+ or -] 5; and O, -7 [+ or -] 1%[DELTA][CVC.sub.baseline]; P = 0.016) and was not altered by NOS inhibition. Fasudil blunted NE-mediated VC in both age groups (Y, -23 [+ or -] 4; and O, -7 [+ or -] 3%[DELTA][CVC.sub.baseline]; P < 0.01). Cumulatively, these data indicate that reflex VC is more reliant on ROCK in aged skin such that approximately half of the total VC response to whole body cooling is ROCK dependent. skin blood flow; aging; temperature regulation; norepinephrine doi: 10.1152/ajpheart.00509.2009.

Cyclooxygenase-1 or -2--which one mediates lipopolysaccharide-induced hypothermia? Am J Physiol Regul Integr Comp Physio1297: R485--R494, 2009. First published June 10, 2009; doi: 10.1152/ajpregu.91026.2008.--Systemic inflammation is associated with either fever or hypothermia. Fever, a response to mild systemic inflammation, is mediated by cyclooxygenase (COX)-2 and not by COX-1. However, it is still disputed whether COX-2, COX-l, neither, or both mediate(s) responses to severe systemic inflammation, and, in particular, the hypothermic response. We compared the effects of SC-236 (COX-2 inhibitor) and SC-560 (COX-1 inhibitor) on the deep body temperature ([T.sub.b]) of rats injected with a lower (10 [micro]g/kg iv) or higher (1,000 [micro]g/kg iv) dose of LPS at different ambient temperatures ([T.sub.a]s). At a neutral [T.sub.a] (30[degrees]C), the rats responded to LPS with a polyphasic fever (lower dose) or a brief hypothermia followed by fever (higher dose). SC-236 (2.5 mg/kg iv) blocked the fever induced by either LPS dose, whereas SC-560 (5 mg/kg iv) altered neither the febrile response to the lower LPS dose nor the fever component of the response to the higher dose. However, SC-560 blocked the initial hypothermia caused by the higher LPS dose. At a subneutral [T.sub.a] (22[degrees]C), the rats responded to LPS with early (70-90 min, nadir) dose-dependent hypothermia. The hypothermic response to either dose was enhanced by SC-236 but blocked by SC-560. The hypothermic response to the higher LPS dose was associated with a fall in arterial blood pressure. This hypotensive response was attenuated by either SC-236 or SC-560. At the onset of LPS-induced hypothermia and hypotension, the functional activity of the COX-1 pathway (COX-1-mediated [PGE.sub.2] synthesis ex vivo) increased in the spleen but not liver, lung, kidney, or brain. The expression of splenic COX-1 was unaffected by LPS. We conclude that COX-1, but not COX-2, mediates LPS hypothermia, and that both COX isoforms are required for LPS hypotension. body temperature; thermoregulation; fever; inflammation

Some dinosaurs reached masses that were [approximately equal to] 8 times those of the largest, ecologically equivalent terrestrial mammals. The factors most responsible for setting the maximal body size of vertebrates are resource quality and quantity, as modified by the mobility of the consumer, and the vertebrate's rate of energy expenditure. If the food intake of the largest herbivorous mammals defines the maximal rate at which plant resources can be consumed in terrestrial environments and if that limit applied to dinosaurs, then the large size of sauropods occurred because they expended energy in the field at rates extrapolated from those of varanid lizards, which are [approximately equal to] 22% of the rates in mammals and 3.6 times the rates of other lizards of equal size. Of 2 species having the same energy income, the species that uses the most energy for mass-independent maintenance of necessity has a smaller size. The larger mass found in some marine mammals reflects a greater resource abundance in marine environments. The presumptively low energy expenditures of dinosaurs potentially permitted Mesozoic communities to support dinosaur biomasses that were up to 5 times those found in mammalian herbivores in Africa today. The maximal size of predatory theropods was [approximately equal to] 8 tons, which if it reflected the maximal capacity to consume vertebrates in terrestrial environments, corresponds in predatory mammals to a maximal mass less than a ton, which is what is observed. Some coelurosaurs may have evolved endothermy in association with the evolution of feathered insulation and a small mass. ectothermy | endothermy | energy expenditure | varanid lizards

Females may engage in extrapair copulations to receive indirect benefits in the form of more immunocompetent young. Nestling quality is often assessed by examining immune function using the phytohemagglutinin (PHA) skin test, which can be a predictor of nestling recruitment. However, the PHA test can also be influenced by factors such as nest temperature. We tested the prediction that extrapair young mount greater immune responses to a PHA challenge and recruit at a greater rate than within-pair young in a wild population of Savannah Sparrows (Passerculus sandwichensis). We also investigated ambient temperature and its relationship with immune response. Extra- and within-pair young did not significantly differ with respect to PHA-induced immune response or with respect to recruitment. In contrast to other studies, we found that PHA-induced immune response was not associated with nestling recruitment rates. However, it was positively correlated with minimum ambient temperature for males hatched in 2002 and 2003, and for females in 2003 (with a similar, but marginally nonsignificant, trend in 2002). Immune response to PHA also was positively correlated with nestling mass for males hatched in 2002 and for females hatched in 2002 and 2003. We concluded that given the lack of relationship among immune responses, paternity, and recruitment rates in this population of Savannah Sparrows, nestling immune response to PHA injection should not be considered predictive of recruitment in populations where this relationship has not been explicitly explored, and environmental variables such as nest temperature may be an important covariate in immunoresponsiveness. Key words: extrapair paternity, Passerculus sandwichensis, phytohemagglutinin, recruitment, Savannah Sparrow, temperature.

Dehydrated mammals conserve body water by reducing thermoregulatory evaporative cooling responses e.g., panting and sweating. Increased core temperature (Tc) may result. Following rehydration and correction of fluid deficits, panting and sweating commence. We investigated the role of oropharyngeal/esophageal, postabsorptive and thermal signals in the panting response, and reduced Tc that occurs when unshorn sheep drink water following water deprivation for 2 days (ambient temperature 20[degrees]C). Ingestion of water (at body temperature) resulted in increased respiratory rate (panting) and reduced Tc within 4 min that persisted for at least 90 min. Initially, a similar panting response and reduced Tc occurred following rehydration by drinking isotonic saline solution, but panting was not sustained after 20 min, and Tc began to rise again. Rehydration by intrarnminal administration of water, without any drinking, resulted in delayed panting and fall in Tc. Intraruminal infusion of saline was ineffective. Rehydration by drinking cool water (20[degrees]C) resulted in a rapid fall in Tc without increased panting. Shorn sheep had lower basal Tc that did not increase during 2 days of water deprivation, and they did not pant on rehydration by drinking water. Our results indicate that signals from the oropharyngeal and/or esophageal region associated with the act of drinking play a crucial role in the initial 20-30 min of the panting response to rehydration. Postabsorptive factors most likely reduced plasma tonicity and cause continued panting and further reduction in Tc. Tc also influences rehydration-induced panting. It occurs only if sheep incur a heat load during bodily dehydration. water; plasma tonicity; heat loss; dehydration

This work describes and presents results from a new three-dimensional whole-body model of human thermoregulation. The model has been implemented using a version of the 'Brooks Man' anatomical data set, consisting of 1.3 x [10.sup.8] cubic volume elements (voxels) measuring 0.2 cm/side. The model simulates thermoregulation through passive mechanisms (metabolism, blood flow, respiration, and transpiration) and active mechanisms (vasodilatation, vasoconstriction, sweating, and shivering). Compared with lumped or compartment models, a voxel model is capable of high spatial resolution and can capture a level of anatomical detail not achievable otherwise. A high spatial resolution model can predict detailed heating patterns from localized or nonuniform heating patterns, such as from some radio frequency sources. Exposures to warm and hot environments (ambient temperatures of 33-48[degrees]C) were simulated with the current voxel model and with a recent compartment model. Results from the two models (core temperature, skin temperature, metabolic rate, and evaporative cooling rate) were compared with published experimental results obtained under similar conditions. Under the most severe environmental conditions considered (47.8[degrees]C, 27% RH for 2 h), the voxel model predicted a rectal temperature increase of 0.56[degrees]C, compared with a core temperature increase of 0.45[degrees]C from the compartment model and an experimental mean rectal temperature increase of 0.6[degrees]C. Similar, good agreement was noted for other thermal variables and under other environmental conditions. Results suggest that the voxel model is capable of predicting temperature response (core temperature and skin temperature) to certain warm or hot environments, with accuracy comparable to that of a compartment model. In addition, the voxel model is able to predict internal tissue temperatures and surface temperatures, over time, with a level of specificity and spatial resolution not achievable with compartment models. The development of voxel models and related computational tools may be useful for thermal dosimetry applications involving mild temperature hyperthermia and for the assessment of safe exposure to certain nonionizing radiation sources. [DOI: 10.1115/1.3002765] Keywords: thermoregulation, computational models, environmental heating, human models

Increasing concern about the impacts of global warming on biodiversity has stimulated extensive discussion, but methods to translate broad-scale shifts in climate into direct impacts on living animals remain simplistic. A key missing element from models of climatic change impacts on animals is the buffering influence of behavioral thermoregulation. Here, we show how behavioral and mass/energy balance models can be combined with spatial data on climate, topography, and vegetation to predict impacts of increased air temperature on thermoregulating ectotherms such as reptiles and insects (a large portion of global biodiversity). We show that for most 'cold-blooded' terrestrial animals, the primary thermal challenge is not to attain high body temperatures (although this is important in temperate environments) but to stay cool (particularly in tropical and desert areas, where ectotherm biodiversity is greatest). The impact of climate warming on thermoregulating ectotherms will depend critically on how changes in vegetation cover alter the availability of shade as well as the animals' capacities to alter their seasonal timing of activity and reproduction. Warmer environments also may increase maintenance energy costs while simultaneously constraining activity time, putting pressure on mass and energy budgets. Energy- and mass-balance models provide a general method to integrate the complexity of these direct interactions between organisms and climate into spatial predictions of the impact of climate change on biodiversity. This methodology allows quantitative organism- and habitat-specific assessments of climate change impacts. Australia | biophysical model | climate change | terrestrial ectotherm | GIS

Sexual segregation during the breeding season is common in many temperate bat species, and may be related to sex-specific thermoregulatory, microclimatic, or energetic requirements. We compiled capture data for 3 species of Nyctalus (noctule bats) obtained over >20 years to study reproductive and migratory strategies of these species in southwestern Europe. Within the Iberian Peninsula, several different strategies regarding sex distribution and migratory behavior were observed within each of the 3 Nyctalus species. In the northern part of Iberia there are populations of the 3 species composed of males all year-round with females appearing only during the mating season. Reproduction by females in this area has not been confirmed. In central and southern Iberia there are breeding populations in which sexual segregation occurs only at the roosts or at a regional scale, possibly with females located at lower elevations during the breeding season. Female-biased, long-distance migration is likely to be the cause of sexual segregation in populations of N. noctula and N. leisleri in northern and central Iberia, but not of N. lasiopterus, absent in central Europe. For this latter species, segregation by elevation also could occur in northern Iberia. The Iberian Peninsula is a good example of how breeding strategies and migratory behavior in bats can be very flexible and vary across relatively small geographical scales. Key words: migration, Nyctalus lasiopterus, Nyctalus leisleri, Nyctalus noctula, segregation by elevation, sex ratio, sexual segregation

Three studies were conducted to evaluate the effects of supplemental fat and salt (sodium chloride) on DMI, daily water intake (DWI), body temperature, and respiration rate (RR) in Bos taurus beef cattle. In Exp. 1 and 2, whole soybeans (SB) were used as the supplemental fat source. In Exp. 3, palm kernel meal and tallow were used. Experiment 1 (winter) and Exp. 2 (summer) were undertaken in an outside feedlot. Experiment 3 was conducted in a climate-controlled facility (mean ambient temperature = 29.9[degrees]C). In Exp. 1, three diets, 1) control; 2) salt (control + 1% sodium chloride); and 3) salt-SB (control + 5% SB + 1% sodium chloride), were fed to 144 cattle (BW = 327.7 kg), using a replicated 3 x 3 Latin square design. In Exp. 2, 168 steers (BW = 334.1 kg) were used. In Exp. 2, the same dietary treatments were used as in Exp. 1, and a 5% SB dietary treatment was included in an incomplete 3 x 4 Latin square design. In Exp. 3, three diets, 1) control; 2) salt (control + 0.92% NaCl); and 3) salt-fat (control + 3.2% added fat + 0.92% NaCl) were fed to 12 steers (BW = 602 kg) in a replicated Latin square design. In Exp. 1, cattle fed the salt-SB diet had elevated (P < 0.05) tympanic temperature (TT; 38.83[degrees]C) compared with cattle fed the control (38.56[degrees]C) or salt (38.50[degrees]C) diet. In Exp. 2, cattle fed the salt and salt-SB diets had less (P < 0.05) DMI and greater (P < 0.05) DWI than cattle in the control and SB treatments. Cattle fed the salt-SB diet had the greatest (P < 0.05) TT (38.89[degrees]C). Those fed only the salt diet or only the SB diet had the least (P < 0.05) TT, at 38.72 and 38.78[degrees]C, respectively. Under hot conditions (Exp. 3), DMI of steers fed the salt and salt-fat diets declined by approximately 40% compared with only 24% for the control cattle. During hot conditions, DWI was greatest (P < 0.05) for steers on the salt-fat diet. These steers also had the greatest (P < 0.05) mean rectal temperature (40.03 [+ or -] 0.1[degrees]C) and RR (112.7 [+ or -] 1.7 breaths/min). The RR of steers on the control diet was the least (P < 0.05; 98.3 [+ or -] 1.7 breaths/min). Although added salt plus fat decreased DMI under hot conditions, these data suggest that switching to diets containing the combination of added salt and fat can elevate body temperature, which would be a detriment in the summer but a benefit to the animal during winter. Nevertheless, adding salt plus fat to diets resulted in increased DWI under hot conditions. Diet ingredients or the combination of ingredients that can be used to regulate DMI may be useful to limit large increases in DMI during adverse weather events. Key words: beef cattle, environmental stress, fat, salt

Nutritional adenosine receptor antagonists can enhance endurance exercise performance in temperate environments, but their efficacy during heat stress is not well understood. This double-blinded, placebo-controlled study compared the effects of an acute dose of caffeine or quercetin on endurance exercise performance during compensable heat stress (40[degrees]C, 20-30% rh). On each of three occasions, 10 healthy men each performed 30-min of cycle ergometry at 50% [Vo.sub.2peak] followed by a 15-min performance time trial after receiving either placebo (Group P), caffeine (Group C; 9 mg/kg), or quercetin (Group Q; 2,000 mg). Serial blood samples, physiological (heart rate, rectal, and mean skin body temperatures), perceptual (ratings of perceived exertion, pain, thermal comfort, motivation), and exercise performance measures (total work and pacing strategy) were made. Supplementation with caffeine and quercetin increased preexercise blood concentrations of caffeine (55.62 [+ or -] 4.77 [micro]M) and quercetin (4.76 [+ or -] 2.56 [micro]M) above their in vitro inhibition constants for adenosine receptors. No treatment effects were observed for any physiological or perceptual measures, with the exception of elevated rectal body temperatures (0.20-0.30[degrees]C; P < 0.05) for Group C vs. Groups Q and P. Supplementation did not affect total work performed (Groups P: 153.5 [+ or -] 28.3, C: 157.3 [+ or -] 28.9, and Q: 151.1 [+ or -] 31.6 kJ; P > 0.05) or the self-selected pacing strategy employed. These findings indicate that the nutritional adenosine receptor antagonists caffeine and quercetin do not enhance endurance exercise performance during compensable heat stress. caffeine; quercetin; thermoregulation; central fatigue; dietary supplements

Allen's Rule documents a century-old biological observation that strong positive correlations exist among latitude, ambient temperature, and limb length in mammals. Although genetic selection for thermoregulatory adaptation is frequently presumed to be the primary basis of this phenomenon, important but frequently overlooked research has shown that appendage outgrowth is also markedly influenced by environmental temperature. Alteration of limb blood flow via vasoconstriction/vasodilation is the current default hypothesis for this growth plasticity, but here we show that tissue perfusion does not fully account for differences in extremity elongation in mice. We show that peripheral tissue temperature closely reflects housing temperature in vivo, and we demonstrate that chondrocyte proliferation and extracellular matrix volume strongly correlate with tissue temperature in metatarsals cultured without vasculature in vitro. Taken together, these data suggest that vasomotor changes likely modulate extremity growth indirectly, via their effects on appendage temperature, rather than vascular nutrient delivery. When combined with classic evolutionary theory, especially genetic assimilation, these results provide a potentially comprehensive explanation of Allen's Rule, and may substantially impact our understanding of phenotypic variation in living and extinct mammals, including humans. Allen's Rule | bone growth | bone tissue culture | cartilage biology | thermoregulation

California sea lions (Zalophus californianus) occur along much of the Pacific coast of North America, but the number of breeding areas that are occupied is relatively small. Our understanding of the attributes that make these few sites preferable is currently limited. We quantified habitat characteristics--substrate type and coloration, aspect, slope, curvature of shoreline, and availability of shade, water pools, and resting areas--at 26 sites (7 islands) occupied by sea lions and 33 unused sites (8 islands) distributed throughout the Gulf of California, Mexico. Logistic regression models were used to explore how habitat characteristics explained sea lion occupancy patterns. Models discriminated very well between occupied and unused sites, and showed that occupied locations were more often located in sites with larger-size rocks (odds ratio [OR] = 1.209), lighter-color substrates (OR = 0.219), and convex shorelines (OR = 1.067). All of these preferred characteristics are likely to play a role in the prevention of heat stress in sea lions, suggesting that increases in temperature, such as those expected from global warming, may pose an additional risk for this already declining sea lion population. To partially offset this risk, our results may be used to identify, and protect, unused but suitable (i.e., thermally favorable) habitat. In addition, we recommend effective protection and monitoring of the currently occupied areas and their populations. Key words: conditional logistic regression, habitat selection, pinniped, Sea of Cortes, thermoregulation

Denning and resting site use by radiocollared eastern spotted skunks (Spilogale putorius) in the Ouachita Mountains of western Arkansas was investigated from May through August 2005 and 2006. We identified and characterized microhabitat and landscape characteristics of 127 resting and den sites. Sites were located in burrows excavated by other mammal species (48%), in decayed or burned root systems (22%), in rocky outcrops (14%), in eastern woodrat (Neotomafloridana) nests (9%), or in ground-level tree or log cavities (7%). Reuse of sites by the same individual was common (32.3%), but use of the same site by different individuals was rare, as was communal use of sites (< 1.0% each). Contrasting used and putatively available dens and resting sites, we found that sites were selected based primarily on increased vegetative cover, which supports hypotheses that thermal regulation and predator avoidance may underlie den and resting site selection. Higher rock and vine densities, younger pine forest stands, older hardwood stands, steeper slope, and smaller site entrance also positively influenced resting and den site selection. These findings suggest that eastern spotted skunks select structurally complex sites, likely to enhance protection from predators. Eastern spotted skunks may thus be vulnerable to habitat alterations that reduce this structural complexity. Key words: carnivore, den site, eastern spotted skunk, habitat selection, Ouachita Mountains, resting site, Spilogale putorius

Twin-bearing Targhee ewes (Exp. 1, 1 yr, n = 42) and 1,182 single- and twin-bearing whiteface range ewes (Exp. 2, n = 8 experimental units over 2 yr) were used in a 2 x 2 factorial arrangement of treatments to determine the effect of supplemental energy source and level of vitamin E supplement on lamb serum metabolites and thermogenesis (Exp. 1) and on lamb growth (Exp. 2). During late gestation, ewes were individually fed (Exp. 1) or group-fed (Exp. 2) a daily supplement. Supplements were 226 g/ewe of daily safflower seed (DM basis; SS) with either 350 IU/ewe daily (VE) or no added supplemental (VC) vitamin E; or 340 g/ewe daily of a barley-based grain supplement (DM basis; GC) and either VE or VC. One hour postpartum in Exp. 1, twin-born lambs were placed in a 0[degrees]C dry cold chamber for 30 min. Lamb rectal temperature was recorded every 60 s and blood samples were taken immediately before and after cold exposure. In Exp. 2, lambs were weighed at birth, at turnout from confinement to spring range (32 d of age [+ or -] 7; turnout), and at weaning (120 d of age [+ or -] 7). Ewes were weighed at turnout and weaning. In Exp. 1, a level of vitamin E x energy source interaction was detected (P < 0.10) for body temperature and change in NEFA and glucose concentrations. Lambs from SSVC ewes had the lowest (P = 0.01) body temperature and had decreased (P = 0.08) NEFA concentration. The SS lambs tended to have decreased (P < 0.11) concentrations of blood urea N (BUN) and thyroxine at 0 min than did lambs born to GC ewes. After 30 min of cold exposure, SS lambs had increased and GC lambs had decreased BUN, triiodothyronine, and triiodothyronine:thyroxine concentrations (P< 0.10). In Exp. 2, kilograms of lamb per ewe at turnout and weaning and lamb survival at weaning were greater (P < 0.07) for GC than SS lambs. Based on the decreased body temperature in SSVC lambs at birth, the greater change in BUN during the cold exposure for SS than GC lambs, and the decreased survival rate for SS than GC lambs, SSVC-supplemented ewes appeared to give birth to lambs with an apparently decreased energetic capacity. This may compromise the ability of the newborn lamb to adapt to extreme environmental conditions. Key words: gestation, lamb survival, safflower seed, sheep, thermogenesis, vitamin E

In plants, heat stress responses are controlled by heat stress transcription factors that are conserved among all eukaryotes and can be constitutively expressed or induced by heat. Heat-inducible transcription factors that are distinct from the 'classical' heat stress transcription factors have also been reported to contribute to heat tolerance. Here, we show that bZIP28, a gene encoding a putative membrane-tethered transcription factor, is up-regulated in response to heat and that a bZIP28 null mutant has a striking heat-sensitive phenotype. The heat-inducible expression of genes that encode BiP2, an endoplasmic reticulum (ER) chaperone, and HSP26.5-P, a small heat shock protein, is attenuated in the bZIP28 null mutant. An estradiol-inducible bZIP28 transgene induces a variety of heat and ER stress-inducible genes. Moreover, heat stress appears to induce the proteolytic release of the predicted transcription factor domain of bZIP28 from the ER membrane, thereby causing its redistribution to the nucleus. These findings indicate that bZIP28 is an essential component of a membrane-thethered transcription factor-based signaling pathway that contributes to heat tolerance. BiP2 | bZIP28 | endoplasmic reticulum | signal transduction | thermotolerance

This paper examines evidence for the hypothesized connection between solar thermal properties of butterfly and moth (Lepidoptera) wings, iridescence/structural color, and thermoregulation. Specimens of 64 species of Lepidoptera were measured spectrophotometrically, their solar absorptances calculated, and their habitat temperatures determined. No correlation was found between habitat temperature and the solar absorptance of the wings. It was found, however, that the iridescent specimens exhibited, on average, substantially higher solar absorptance than noniridescent ones. OCIS codes: 240.0240, 300.6540, 300.6550, 300.6340, 350.6050.

Hypothalamic neurons are regarded as essential for integrating thermal afferent information from skin and core and issuing commands to autonomic and behavioral effectors that maintain core temperature ([T.sub.c]) during cold exposure and for the control of energy expenditure more generally. Caudal brain stem neurons are necessary elements of the hypothalamic effector pathway and also are directly driven by skin and brain cooling. To assess whether caudal brain stem processing of thermal afferent signals is sufficient to drive endemic effectors for thermogenesis, heart rate (HR), [T.sub.c], and activity responses of chronic decerebrate (CD) and control rats adapted to 23[degrees]C were compared during cold exposure (4, 8, or 12[degrees]C) for 6 h. Other CDs and controls were exposed to 4 or 23[degrees]C for 2 h, and tissues were processed for norepinephrine turnover (NETO), a neurochemical measure of sympathetic drive. Controls maintained [T.sub.c] for all temperatures. CDs maintained [T.sub.c] for the 8 and 12[degrees]C exposures, but [T.sub.c] declined 2[degrees]C during the 4[degrees]C exposure. Cold exposure elevated HR in CDs and controls alike. Tachycardia magnitude correlated with decreases in environmental temperature for controls, but not CDs. Cold increased NETO in brown adipose tissue, heart, and some white adipose tissue pads in CDs and controls compared with their respective room temperature controls. These data demonstrate that, in neural isolation from the hypothalamus, cold exposure drives caudal brain stem neuronal activity and engages local effectors that trigger sympathetic energetic and cardiac responses that are comparable in many, but not in all, respects to those seen in neurologically intact rats. energy balance; thermoregulation; anterior hypothalamus; heart rate; body temperature; sympathetic drive; norepinephrine turnover; white adipose tissue; brown adipose tissue

Torpor minimizes energy expenditure and water loss during periods of inclement weather, low prey availability, or both, and appears especially important in harsh environments such as deserts. We investigated use of torpor by free-ranging adult male pallid bats (Antrozous pallidus) at the northern limit of their range in the semiarid Okanagan Valley in British Columbia, Canada. We predicted that males would use torpor frequently during the active season and that ambient temperature ([T.sub.a]) as well as nutritional condition (body condition index [BCI]) would affect torpor use. We expected roost microclimate to be conducive to daily heterothermy given that roosts had cool morning temperatures that increased in the afternoon. We used temperature-sensitive radiotransmitters to measure skin temperature ([T.sub.skin]) of 8 bats from June to August 2003. Seven individuals used torpor each day (n = 54 tracking days) but not at night. Torpor duration increased as mean daytime [T.sub.a] decreased albeit the relationship differed between individuals. There was no significant effect of individual on the relationship between minimum [T.sub.skin] during torpor and [T.sub.a]. BCI was significantly and inversely correlated with torpor bout duration. Mean daytime temperatures in rock crevice roosts approached 30[degrees]C and fluctuated less than [T.sub.a]. Key words: ambient temperature, arid habitat, arousal, body condition index, Chiroptera, heterothermy, rewarming, roost temperature, skin temperature

The activity patterns, thermal biology and the torpor of the free-living mulgaras (Dasycercus blythi) in arid zone Australia during the winter reproductive season are studied. Different sexes of the mulgaras are shown to exhibit different torpor patterns during the different seasons of the year.

The genes encoding prokineticin 2 polypeptide (Prok2) and its cognate receptor (Prokr2/ Gpcr7311) are widely expressed in both the suprachiasmatic nucleus and its hypothalamic targets, and this signaling pathway has been implicated in the circadian regulation of behavior and physiology. We have previously observed that the targeted null mutation of Prokr2 disrupts circadian coordination of cycles of locomotor activity and thermoregulation. We have now observed spontaneous but sporadic bouts of torpor in the majority of these transgenic mice lacking Prokr2 signaling. During these torpor bouts, which lasted for up to 8 h, body temperature and locomotor activity decreased markedly. Oxygen consumption and carbon dioxide production also decreased, and there was a decrease in respiratory quotient. These spontaneous torpor bouts generally began toward the end of the dark phase or in the early light phase when the mice were maintained on a 12:12-h light-dark cycle and persisted when mice were exposed to continuous darkness. Periods of food deprivation (16-24 h) induced a substantial decrease in body temperature in all mice, but the duration and depth of hypothermia was significantly greater in mice lacking Prokr2 signaling compared with heterozygous and wild-type littermates. Likewise, when tested in metabolic cages, food deprivation produced greater decreases in oxygen consumption and carbon dioxide production in the transgenic mice than controls. We conclude that Prokr2 signaling plays a role in hypothalamic regulation of energy balance, and loss of this pathway results in physiological and behavioral responses normally only detected when mice are in negative energy balance. metabolic rate; thermoregulation; CLAMS; radiotelemetry

The dorsomedial hypothalamus (DMH) has been proposed to play key roles in both the defense reaction to acute stress and in the thermoregulatory response to cold. We reasoned that the autonomic/respiratory motor patterns of these responses would be mediated by at least partly distinct DMH neuron populations. To test this, we made simultaneous recordings of phrenic nerve and plantar cutaneous vasoconstrictor (CVC) activity in 14 vagotomized, ventilated, urethane-anesthetized rats. Microinjections of D,L-homocysteic acid (DLH; 15 nl, 50 mM) were used to cause localized, short-lasting (< 1 min) activation of DMH neuron clusters. Cooling the rat's trunk skin by perfusing cold water through a water jacket-activated plantar CVC activity but depressed phrenic burst rate (cold-response pattern). The expected 'stress/defense response' pattern would be phrenic activation, with increased blood pressure, heart rate, and possibly CVC activity. DLH microinjections into 76 sites within the DMH region never reduced phrenic activity. They frequently increased phrenic rate and/or plantar CVC activity, but the magnitudes of those two responses were not significantly correlated. Plantar CVC responses were evoked most strongly from the dorsal hypothalamic area and most dorsal part of the dorsomedial nucleus, whereas peak phrenic rate responses were evoked from more caudal sites; their relative magnitudes varied systematically with rostrocaudal position. Tachycardia correlated with plantar CVC responses but not phrenic rate. These findings indicate that localized activation of DMH neurons does not evoke full 'cold-response' or stress/defense response patterns, but they demonstrate the existence of significant functional topography within the DMH region. cutaneous vasoconstrictor; phrenic; cold; defense; stress