Thermoregulation of water foraging wasps (Vespula vulgaris and Polistes dominulus)

A comparison of the thermoregulation of water foraging wasps (Vespula vulgaris, Polistes dominulus) under special consideration of ambient temperature and solar radiation was conducted. The body surface temperature of living and dead wasps was measured by infrared thermography under natural conditions in their environment without disturbing the insects’ behaviour. The body temperature of both of them was positively correlated with T_a and solar radiation. At moderate T_a (22–28 °C) the regression lines revealed mean thorax temperatures (T_th) of 35.5–37.5 °C in Vespula, and of 28.6–33.7 °C in Polistes. At high T_a (30–39 °C) T_th was 37.2–40.6 °C in Vespula and 37.0–40.8 °C in Polistes. The thorax temperature excess (T_th–T_a) increased at moderate T_a by 1.9 °C (Vespula) and 4.4 °C (Polistes) per kW⁻¹ m⁻². At high T_a it increased by 4.0 °C per kW⁻¹ m⁻² in both wasps. A comparison of the living water foraging Vespula and Polistes with dead wasps revealed a great difference in their thermoregulatory behaviour. At moderate T_a (22–28 °C) Vespula exhibited distinct endothermy in contrast to Polistes, which showed only a weak endothermic activity. At high T_a (30–39 °C) Vespula reduced their active heat production, and Polistes were always ectothermic. Both species exhibited an increasing cooling effort with increasing insolation and ambient temperature.     

Nest insulation: Energy savings to brown lemmings using a winter nest

Summary Energy metabolism of brown lemmings in summer pelage was measured over long periods at several air temperatures, with and without a real nest or artificial nest material. Resting metabolism of lemmings at T _a=-16°C was 43% higher than that of lemmings in nests. As T _a increased, the difference between resting metabolism of animals with and without nests decreased and was similar at T _a=20°C. The energy saved at rest is equivalent to a reduction of approximately 40% in the thermal conductance. Independent estimates of energy savings due to nest insulation by analysis of cooling curves of a lemming model with and without a nest suggest a 46% reduction in thermal conductance due to the nest. At T _a=0°C, baby lemmings huddled in a nest had equilibrium temperature excesses (T _b-T _a) four to five times higher than isolated nestlings outside the nest. These data indicate that there is a substantial energy savings at ecologically relevant air temperatures, and that energy savings increase as T _a decreases. If the insulative value of the nest is similar whether the animal is in summer or winter pelage, these data suggest that heat production of a resting lemming would be 0.88 W (about 1.6 times BMR), while in nests at subnivean air temperatures typical of Barrow, Alaska, during the winter.     

Responses to heat stress in two species of Australian quail,Coturnix pectoralis andCoturnix chinensis

Summary Stubble quail and King quail are both native to Australia although Stubble quail extend into more arid environments than do King quail. In this study, the responses of body temperature (T _b), heart rate (f _h), respiration rate (f _r) and rates of gular flutter (f _g) were measured in response to ambient temperatures (T _a) ranging from 20 °C to 50 °C. Both species exhibited hyperthermia atT _a in excess of 38–39 °C although both species maintainedT _b lower thanT _a atT _a above 42 °C. Respiration rate remained relatively constant until the onset of panting, just prior to the commencement of gular flutter. The onset of panting and gular flutter in both species was relatively sudden and occurred at a meanT _a of 38.1 °C for Stubble quail (meanT _b of 42.5 °C) and a significantly higherT _a of 40.9 °C but similar meanT _b of 42.1 °C for King quail. Gular flutter appeared to occur synchronously with respiration and showed some tendency to increase withT _b. The percentage of time spent in gular flutter showed a direct increase withT _b. Heart rate tended to decrease with increasingT _a in King quail while remaining relatively constant in Stubble quail. However, the relationship was not consistent and a great deal of variability existed between individuals. The two species are similar in their responses to heat stress and in general these responses do not reflect their different natural habitats.Symbols f _h heart rate - f _r respiratory rate - f _g rate of gular fluttering     

Working with what you’ve got: Changes in thermal preference and behavior in mice with or without nesting material

In laboratories mice are typically housed at ambient temperatures (T_a) of 20-24 °C, which are below their average preferred T_a of ≈30 °C. Adjusting laboratory T_a is not a solution because preferences differ depending on activity, time of the day, and gender. We tested the hypothesis that providing mice with nesting material will allow behavioral thermoregulation and reduce aversion to colder T_a. We housed C57BL/6J mice with and without nesting material in a set of 3 connected cages, each maintained at a different T_a (20, 25, or 30 °C). Mice were confined in and given free access to the T_a options to determine if thermotaxis or nest building was the primary mode of behavioral thermoregulation. As predicted, nesting material reduced aversion to 20 °C but the overall preference, in both treatments, was still 30 °C. Inactive and nesting behaviors were more likely to be seen in contact with nesting material while active behaviors were more likely to be observed when not in contact. Nest quality increased with decreasing T_a when mice could not use thermotaxis but nest quality was uncorrelated with T_a when thermotaxis was possible. Males decreased nest quality with increasing temperatures but females showed no correlation. We conclude that nesting material does not alter thermal preferences for 30 °C when thermotaxis is possible, indicating thermotaxis as the primary mode of behavioral thermoregulation. However, when thermotaxis is not possible, mice adjust nest shape depending on the T_a. Nesting material appears to partially compensate for cooler T_a and is especially important when mice are inactive. Therefore, nesting material may be a solution to the mismatch between laboratory T_a and mouse thermal preferences.     

Thermoregulation of water foraging honeybees—Balancing of endothermic activity with radiative heat gain and functional requirements

Foraging honeybees are subjected to considerable variations of microclimatic conditions challenging their thermoregulatory ability. Solar heat is a gain in the cold but may be a burden in the heat. We investigated the balancing of endothermic activity with radiative heat gain and physiological functions of water foraging Apis mellifera carnica honeybees in the whole range of ambient temperatures (T_a) and solar radiation they are likely to be exposed in their natural environment in Middle Europe.The mean thorax temperature (T_th) during foraging stays was regulated at a constantly high level (37.0-38.5 °C) in a broad range of T_a (3-30 °C). At warmer conditions (T_a = 30-39 °C) T_th increased to a maximal level of 45.3 °C. The endothermic temperature excess (difference of T_body − T_a of living and dead bees) was used to assess the endogenously generated temperature elevation as a correlate of energy turnover. Up to a T_a of ∼30 °C bees used solar heat gain for a double purpose: to reduce energetic expenditure and to increase T_th by about 1-3 °C to improve force production of flight muscles. At higher T_a they exhibited cooling efforts to get rid of excess heat. A high T_th also allowed regulation of the head temperature high enough to guarantee proper function of the bees’ suction pump even at low T_a. This shortened the foraging stays and this way reduced energetic costs. With decreasing T_a bees also reduced arrival body weight and crop loading to do both minimize costs and optimize flight performance.     

Thermoregulation in the primitively eusocial paper wasp, Polistes dominulus

Regulation of wing muscle temperature is important for sustaining flight in many insects, and has been well studied in honeybees. It has been much less well studied in wasps and has never been demonstrated in Polistes paper wasps. We measured thorax, head, and abdomen temperatures of inactive Polistes dominulus workers as they warmed after transfer from 8 to ~25°C ambient temperature, after removal from hibernacula, and after periods of flight in a variable temperature room. Thorax temperature (T _th) of non-flying live wasps increased more rapidly than that of dead wasps, and T _th of some live wasps reached more than 2°C above ambient temperature (T _a), indicating endothermy. Wasps removed from hibernacula had body region temperatures significantly above ambient. The T _th of flying wasps was 2.5°C above ambient at T _a = 21°C, and at or even below ambient at T _a = 40°C. At 40°C head and abdomen temperatures were both more than 2°C below T _a, indicating evaporative cooling. We conclude that P. dominulus individuals demonstrate clear, albeit limited, thermoregulatory capacity.     

Variability of the thermal behavior of honeybees on a feeding place

Summary The thermoregulation of honeybees (Apis mellifera carnica) was investigated under field conditions, on a feeding place 335 m away from the hive, where 0.25M or 0.5M sucrose solution was offered. By means of real-time tele-thermography, contactless body surface temperature measurements of undisturbed animals were made.The foraging bees showed highly developed individual thermoregulatory abilities. Complex behavioral patterns such as food uptake, active body temperature regulation, and preparation for flight were performed simultaneously. However, body temperature was more variable than expected. When bees drank 0.5M sucrose solution, they generally had a higher thoracic surface temperature (T _Ths) and showed smaller temperature fluctuations (e.g., cooling down after landing) than with 0.25M solution. Given 0.5M sucrose they stayed for shorter periods at the feeding place. The highest (maximum)T _Ths during the stop was positively (linearly) correlated with the ambient temperature (T _a=18–30°C) for both 0.25M and 0.5M sucrose feeding. At aT _a of 19°C the mean (interpolated) maximum values forT _Ths were 37.2°C (0.25M) and 38.5°C (0.5M); at aT _a of 27°C they were 39.2°C (0.25M) and 40.9°C (0.5M). The minimumT _Ths was correlated withT _a only with 0.5M feeding, whereas with 0.25M feeding a great variability was observed. Similarly as the maximumT _Ths,T _Ths upon landing and taking off were positively (linearly) correlated withT _a and were higher during 0.5M feeding.The quality (concentration) of the food offered to the bees obviously influenced their thermal behavior at the feeding place.Abbreviations T _a ambient temperature - T _Ths thoracic surface temperature - IR infra-red     

Pigeon flight in a wind tunnel

Summary Core temperatureT _c, breast temperatureT _s–br and leg temperatureT _s–1 were measured simultaneously in pigeons during rest and flight in a wind tunnel, using thermistors.MeanT _c at rest is 39.8±0.7°C and is independent of ambient temperatureT _a (10–30°C). In the first minutes of flight,T _c increases to 1.5–3.0°C above resting level and remains at this higher level. This hyperthermia increases withT _a (v=const.). It is±constant in the lowT _a range (10.6–13.9°C) at flight speeds v ranging from 10–18 m s^–1 and normal body mass, but increases with v and elevated body mass in the highT _a range (23.7–28.8°C). T _s–1 is adapted toT _a at rest and increases in flight up to 3–4°C belowT _c. This increase inT _s–1 is linear toT _a. T _s–br is always lower thanT _c, in extreme cases reaching restingT _c in flight.Supported by the Deutsche Forschungsgemeinschaft     

Body temperature and thermoregulation in two species of yellowjackets,Vespula germanica and V. maculifrons

In spite of the abundance and broad distribution of social wasps, little information exists concerning thermoregulation by individuals. We measured body temperatures of the yellowjackets Vespula germanica and V. maculifrons and examined their thermoregulatory mechanisms. V. germanica demonstrated thermoregulation via a decreasing gradient between thorax temperature and ambient temperature as ambient temperature increased. V. maculifrons exhibited a constant gradient at lower ambient temperatures but thorax temperature was constant at high ambient temperatures. Head temperature exhibited similar patterns in both species. In spite of low thermal conductances, a simple heat budget model predicts substantial heat loads in warm conditions in the absence of thermoregulation. Both species regurgitated when heated on the head. A smaller volume of regurgitant was produced at lower head temperatures and a larger volume at higher head temperatures. Small regurgitations resulted in stabilization of head temperature, while large ones resulted in 4°C decreases in head temperature. Regurgitation was rare when wasps were heated upon the thorax. Abdomen temperature was 3–4°C above ambient temperature, and approached ambient temperature under the hottest conditions. No evidence was found for shunting of hot hemolymph from thorax to abdomen as a cooling mechanism. The frequency of regurgitation in workers returning to the nest increased with ambient temperature. Regurgitation may be an important thermoregulatory strategy during heat stress, but is probably not the only mechanism used in yellowjackets.Abbreviations M _b body mass - M _th thorax mass - T _a ambient temperature - T _ab abdomen temperature - T _b body temperature - T _h head temperature - T _th thorax temperature - C _t thermal conductance     

Temperature and forager body size affect carbohydrate collection in German yellowjackets, Vespula germanica (Hymenoptera, Vespidae)

The classic formulation of optimal foraging theory predicts that a central-place forager will gather more food if it is required to travel farther from the nest to find that food. We examined the foraging behavior of German yellowjackets (Vespula germanica) to determine whether carbohydrate foragers follow this pattern. We trained foragers to collect 2 M fructose solution at 5 or 50 m from the nest and measured the time spent feeding, load size, and the rate of delivery. We show that as a forager’s crop fills during a foraging bout, the amount of solution ingested per second decreased. However, load size did not change as wasps collected food up to 50 m from the nest. Instead, temperature and body size were better predictors of the volume of fructose a forager carried. Finally, the rate of fructose delivered to the nest was higher at warmer temperatures. Due to the fact that wasps gather more food but feed for shorter periods of time at warmer temperatures, we found an overall negative relationship between feeding time and load size. We conclude that the strong effects temperature had on the behavior of V. germanica foragers imply that feeding time may not always be an accurate predictor of the size of the load an individual carries back to the nest. Results from this study suggest that in yellowjacket colonies, foragers can collect and bring disproportionately more food back to the nest during the warmest days of the summer, a time of year when this pest species reaches peak population size during its annual colony cycle.     

Factors affecting the daily rhythm of body temperature of captive mouse lemurs (<Emphasis Type="Italic">Microcebus murinus</Emphasis>)

Microcebus murinus, a small nocturnal Malagasy primate, exhibits adaptive energy-saving strategies such as daily hypothermia and gregarious patterns during diurnal rest. To determine whether ambient temperature (T_a), food restriction and nest sharing can modify the daily body temperature (T_b) rhythm, T_b was recorded by telemetry during winter in six males exposed to different ambient temperatures (T_a=25, 20, 15°C) and/or to a total food restriction for 3 days depending on social condition (isolated versus pair-grouped). At 25°C, the daily rhythm of T_b was characterized by high T_b values during the night and lower values during the day. Exposure to cold significantly decreased minimal T_b values and lengthened the daily hypothermia. Under food restriction, minimal T_b values were also markedly lowered. The combination of food restriction and cold induced further increases in duration and depth of torpor bouts, minimal T_b reaching a level just above T_a. Although it influenced daily hypothermia less than environmental factors, nest sharing modified effects of cold and food restriction previously observed by lengthening duration of torpor but without increasing its depth. In response to external conditions, mouse lemurs may thus adjust their energy expenditures through daily modifications of both the duration and the depth of torpor.     

Effect of torpor on the water economy of an arid-zone marsupial,the stripe-faced dunnart (<Emphasis Type="Italic">Sminthopsis macroura</Emphasis>)

Metabolic rate and evaporative water loss (EWL) were measured for a small, arid-zone marsupial, the stripe-faced dunnart (Sminthopsis macroura), when normothermic and torpid. Metabolic rate increased linearly with decreasing ambient temperature (T_a) for normothermic dunnarts, and calculated metabolic water production (MWP) ranged from 0.85±0.05 (T_a=30°C) to 3.13±0.22 mg H₂O g^–1 h^–1 (T_a=11°C). Torpor at T_a=11 and 16°C reduced MWP to 24–36% of normothermic values. EWL increased with decreasing T_a, and ranged from 1.81±0.37 (T_a=30°C) to 5.26±0.86 mg H₂O g^–1 h^–1 (T_a=11°C). Torpor significantly reduced absolute EWL to 23.5–42.3% of normothermic values, resulting in absolute water savings of 50–55 mg H₂O h^–1. The relative water economy (EWL/MWP) of the dunnarts was unfavourable, remaining >1 at all T_a investigated, and did not improve with torpor. Thus torpor in stripe-faced dunnarts results in absolute, but not relative, water savings.     

Heat balance of two starling species (Sturnus vulgaris andOnychognathus tristrami) from temperate and desert habitats

Summary Body temperature (T _b), oxygen consumption , thermal conductance (C) and evaporative water loss (EWL) were measured at various air temperatures (T _a) in two starlings which evolved in the tropics: a migratory species from a temperate climate,Sturnus vulgaris, and a resident, desert species,Onychognathus tristrami (Aves, Passeriformes, Sturnidae).AtT _a's of 4–35°C both birds hadT _b of 40.6°C. At 44°C,T _b ofSturnus was 45.8°C and that ofOnychognathus 43.3°C.T _a of 44°C was tolerated only byOnychognathus. The thermoneutral zone (TNZ) ofSturnus was in theT _a range of 29.5°C–36.5°C, that ofOnychognathus 21.5–36.5°C. ofSturnus within its TNZ (BMR) was 2.37 ml O₂ g^–1 h^–1, which is close to the expected BMR; that ofOnychognathus, 1.67 ml O₂ g^–1 h^–1, is only 74% of the expected. AtT _a'sNZ,C ofSturnus was twice as high as that ofOnychognathus and 1.68 times the expected value, whereasC ofOnychognathus was only 94% of the expected. At highT _a'sOnychognathus had higherC thanSturnus. At either low or highT _a's EWL ofSturnus was greater than ofOnychognathus.The responses shown bySturnus are typical of a tropical bird living in a moderate environment. This indicates that neither in USSR where it spends the summer, nor in Israel where it spends the winter, is this starling exposed to extreme temperatures.Onychognathus is better adapted not only to high but also to the low temperatures prevailing in mountainous regions of the desert.Symbols and abbreviations BMR basal metabolic rate - C thermal conductance - EWL evaporative water loss - HE evaporative heat loss - HP heat production - TNZ thermoneutral zone     

Capacity for sustained terrestrial locomotion in an insect: Energetics,thermal dependence,and kinematics

Summary The capacity for sustained, terrestrial locomotion in the cockroach. Blaberus discoidalis, was determined in relation to running speed, metabolic cost, aerobic capacity, and ambient temperature (T _a=15, 23, and 34°C; acclimation temperature=24°C). Steady-state thoracic temperature (T _tss) increased linearly with speed at each T _a.The difference between T _tss and T _awas similar at each experimental temperature with a maximum increase of 7°C. Steady-state oxygen consumption (VO_2ss) increased linearly with speed at each T _aand had a low thermal dependence (Q₁₀=1.0-1.4). The minimum cost of locomotion (the slope of the VO_2ss versus speed function) was independent of T _a.Cockroaches attained a maximal oxygen consumption (VO_2max). increased with T _afrom 2.1 ml O₂·g^-1·h^-1 at 15°C to 4.9 ml O₂·g^-1·h^-1 at 23°C, but showed no further increase at 34°C, VO_2max increased 23-fold over resting VO₂ at 23°C, 10-fold at 34°C, and 15-fold at 15°C. Endurance correlated with the speed at which VO_2max was attained (MAS, maximal aerobic speed). Temperature affected the kinematics of locomotion. compared to cockroaches running at the same speed, but higher temperatures (23–34°C), low temperature (15°C) increased protraction time, reduced stride frequency, and reduced stability by increasing body pitching. The thermal independence of the minimum cost of locomotion (C_min), the low thermal dependence of VO_2ss (i.e., y-intercept of the VO_2ss versus speed function), and a typical Q₁₀ of 2.0 for VO_2max combined to increase MAS and endurance in B. discoidalis when T _awas increased from 15 to 23°C. Exerciserelated endothermy enabled running cockroaches to attain a greater VO_2max, metabolic scope, and endurance capacity at 23°C than would be possible if T _tss remained equal to T _a. The MAS of B. discoidalis was similar to that of other arthropods that use trachea, but was 2-fold greater than ectotherms, such as salamanders, frogs, and crabs of a comparable body mass.Abbreviations T _a ambient temperature - T _t thoracic temperature - T _tss steady state thoracic temperature during exercise - T _trest thoracic temperature during rest - VO₂ oxygen consumption - VO_2rest oxygen consumption during rest - VO_2ss steady-state oxygen consumption during exercise - VO_2max maximal oxygen consumption; MAS maximum aerobic speed - C _min minimum cost of locomotion - t _end endurance time     

Thermoregulatory responses to egg cooling in incubating bantam hens

Summary O₂ consumption, electromyographic activity (EMG), heart rate (HR), cloacal temperature (T _b) and broodpatch temperature (T _sb) were measured in bantam hens incubating eggs of different temperatures (T _e). For comparison, the metabolic response to low ambient temperature (T _a) was measured in non-incubating hens.O₂ consumption increased nearly linearly with decreasingT _e down to 30°C. At this temperature O₂ consumption was about 3.5 x the resting level. Below 30°C O₂ consumption increased non-linearly, and reached 4.6 x the resting consumption at 15°C. Eggs of 10 and 0°C gave no further increase. Pectoral muscle EMG and HR also increased in response to egg cooling. The onset of egg cooling was associated with a decrease inT _b andT _sb. Hens exposed to lowT _a showed a lower critical temperature of about 24°C.It is concluded that heat loss from the brood-patch during incubation of cold eggs is compensated by shivering thermogenesis. AtT _e below 15°C heat production is at a maximum level, corresponding to the expected O₂ consumption at exposure to an ambient temperature of –65°C.Abbrevations EMG electromyography - T _a ambient temperature - T _b cloacal temperature - T _e egg temperature - T _sb brood-patch skin temperature     

Thermoregulatory responses of Japanese Quail to various air temperatures and humidities

Measurements of rectal temperature (T_re), feather surface temperature (T_s), heart rate (HR) and breathing rate (BR) of adult Japanese Quail were taken at combinations of four mean relative humidities (rh) and stable or rising air temperature (T_a). T_re increased about 1.7° and 2.5°C at a stable T_a of 40°C from a T_a of 25°C at low (<50%) and high (> 80%) rh, respectively. T_s passively increased with T_a while remaining above T_a as high as 41°C. Panting and gular flutter rates were synchronous and approached rates of 800/min at high rh and stable T_a of 40°C. The steady-state panting rate was a direct curvilinear function of ambient water-vapor pressure (P_w). HR was depressed at successively higher, stable T_a's or with slowly increasing T_a. This thermal bradycardia may be related to the degree of discomfort or stress experienced by the animal.

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Zusammenfassung Bei Kombinationen von 4 relativen Feuchtigkeiten (rh) und konstanter oder ansteigender Temperatur (T_a) wurden Messungen der Rektaltemperatur (T_re), Federoberflächentemperatur (T_s), Herzfrequenz (HR) und Atemfrequenz (BR) an ausgewachsenen japanischen Wachteln vorgenommen. Bei T_a 40°C stieg T_re zwischen 1,7°–2,5°C an ausgehend von T_a 25°C bei <50% und > 80% rh. Die T_s folgte diesem Anstieg von T_a und überschritt ihn bis auf 41°C. Hecheln und Gurren stiegen synchron an bis auf 800/min bei hoher rh und 40°C T_a. Die erhöhte Hechelfrequenz war eine direkte lineare Funktion des Wasserdampfdruckes. HR war verlangsamt bei erhöhter, konstanter T_a. Die Hitzebradykardie steht vermutlich in enger Beziehung zu dem Ausmass der von dem Tier empfundenen Belastung.

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Resume On a soumis des cailles du Japon adultes à 4 taux différents d'humidité relative (rh) par température constante ou en hausse et mesuré la température rectale (T_re), la température superficielle des plumes (T_s), les battements du coeur (HR) et la vitesse de respiration (BR). T_re a augmenté de 1,7°C, respectivement de 2,5°C par suite d'une hausse de T_a de 25°C à 40°C par humidité basse (<50%), respectivement élevée (>80%). T_s a suivi la hausse de T_a et l'a même dépassée jusqu'à atteindre 41°C. Halètement et palpitations ont suivi la courbe de T_a pour atteindre 800/min par rh élevée et 40°C de T_a. La vitesse de respiration s'est élevée en fonction linéaire de la pression de vapeur. HR se sont ralentis par T_a élevée, mais constante. La bradycardie de chaud est probablement étroitement liée à la contrainte ressentie par l'animal.

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This investigation was supported in part by funds provided for medical and biological research by State of Washington Initiative Measure No. 171.     

Seasonal control of energy requirements for thermoregulation in the djungarian hamster (Phodopus sungorus), living in natural photoperiod

Summary Djungarian dwarf hamsters,Phodopus s. sungorus, were kept in natural photoperiodic conditions throughout the year, either inside at a constantT _a of 23°C or outside subjected to seasonally varyingT _a. Comparisons were made between hamsters from both conditions to evaluate the significance of seasonal changes in photoperiod and/orT _a as environmental cues for seasonal acclimatization inPhodopus. Basal metabolic rate was lowest in July (1.68 ml/g·h) and highest in January (2.06 ml/g·h inPhodopus living outside), combined with a decrease inT _1c from 26°C in July to 20°C in January. This was parallelled by seasonal changes in body weight (summer 42 g, winter 25g), fur colouration, fur depth and the occurrence of short daily torpor.AtT _a below thermoneutrality total energy requirements for thermoregulation in winter acclimatizedPhodopus were found 36% lower than summer values (e.g. at O°CT _a in summer 1,160 mW, in winter 760 mW), which were effected by a combined strategy of reducing body weight (19%) together with improvements of thermal insulation of the body surface (17%). All seasonal changes were similar inPhodopus living inside or outside, suggesting that seasonal changes in photoperiod and not seasonal changes inT _a is the overriding controller for the environmental cueing of seasonality in energy requirements for thermoregulation.This research was supported by the Deutsche Forschungsgemeinschaft (He 990)     

Temporal polyethism in Korean yellowjacket foragers,Vespula koreensis (Hymenoptera,Vespidae)

We examined the foraging behavior of the Korean yellowjacket, Vespula koreensis, to determine whether this species displays temporal polyethism. Using video-recordings of the entrances of artificial nest boxes installed in the field, we investigated the association between the tasks performed by workers and age. We identified three foraging tasks (pulp, nectar and prey foraging). Pulp foraging was performed by younger foragers, while nectar and prey foraging were performed by older foragers. We measured the foraging time (time spent outside of the nest during a single foraging bout) and the weight of the materials that foragers brought into the nest for each task to estimate the cost of the task. Pulp foraging was less costly than nectar or prey foraging by both measures. Taken together, the results suggest that yellowjacket foragers tend to perform low-cost task in their early foraging days and high-cost task later. Our results add to a growing literature showing temporal polyethism in social insects.     

Life in extreme environments: Investigations on the ecophysiology of a desert bird,the Australian Diamond Dove (Geopelia cuneata Latham)

Summary The Diamond Dove, Geopelia cuneata, is the world's second smallest (ca. 35 g) species of the columbid order. The Diamond Dove is endemic in the arid and semiarid Mulga and Spinifex regions of Central and Western Australia. It regularly encounters ambient temperatures (T _a ) in its habitat above +40° C, especially when foraging for seeds on bare ground cover, and may be found at up to 40 km from water. This entails extreme thermal stress, with evaporative cooling constrained by limited water supply. Energy metabolism (M), respiration, body temperature (T _a ) and water budget were examined with regard to physiological adaptations to these extreme environmental conditions. The zone of thermal neutrality (TNZ) extended from +34° C to at least +45° C. Basal metabolic rate (BMR) was 34.10±4.19 J g^–1h^–1, corresponding to the values predicted for a typical columbid bird. Thermal conductance (C) was higher than predicted. Geopelia cuneata showed the typical breathing pattern of doves, a combination of normal breathing at a stable frequency (ca. 60 min^–1) at low T _a and panting followed by gular flutter (up to 960 min^–1) at high T _a . At T _a > +36° C, T _a increased to considerably higher levels without increasing metabolic rate, i.e. Q₁₀=1. This enabled the doves not only to store heat but also to save the amout of water that would have been required for evaporative cooling if T _a had remained constant. The birds were able to dissipate more than 100% of the metabolic heat by evaporation at T _a +44° C. This was achieved by gular flutter (an extremely effective mechanism for evaporation), and also by a low metabolic rate due to the low Q₁₀ value for metabolism during increased T _b . At lower T _a , Geopelia cuneata predominantly relied on non-evaporative mechanisms during heat stress, to save water. Total evaporative water loss over the whole T _a range was 19–33% lower than expected. In this respect, their small body size proved to be an important advantage for successful survival in hot and arid environments.Abbreviations and units Body Mass W (g) - Ambient Temperature T _a (°C) - Body Temperature T _b (°C) - Thermoneutral Zone (TNZ) - Metabolism M (J g^–1 h^–1) - Thermal Conductance C - wet Thermal Conductance C _wet (J g^–1 h^–1 °C^–1) - Evaporative Water Loss EWL (mg H₂O g^–1 h^–1) - Evaporative Heat Loss EHL (J g^–1 h^–1) - Breathing Frequency F (breaths min^–1) - Tidal Volume V _t (ml breath^–1) - Standard Temperature Pressure Dry STPD - Body Temperature Pressure Saturated BTPS - Respiratory Quotient RQ - n.s. not significant (P>0.05) - n number of experiments