Diurnal activity, temperature responses and endothermy in three South American cicadas (Homoptera: Cicadidae: Dorisiana bonaerensis, Quesada gigas and Fidicina mannifera)

1. 1. Measurements of body temperature (T_b) in the field demonstrated that endothermic cicadas regulate T_b by behavioral mechanisms as well as by endogenous heat production.

2. 2. The T_b of endothermically active cicadas without access to exogenous heat is approximately the same as the T_b of basking cicadas.

3. 3. Dorisiana bonaerensis (Berg) and Quesada gigas (Olivier) raise T_b in the field with the heat produced in flight.

4. 4. The thermal responses of a particular species are related to its activity patterns and habitat.

5. 5. Endothermy in cicadas may serve to uncouple reproductive behavior from environmental constraints; to circumvent possible thermoregulatory problems; to permit the utilization of habitats unavailable to strictly ectothermic cicadas; to reduce predation; and to optimize broadcast coverage and sound transmission.

     

Thermoregulation by the short-horned lizard (Phrynosoma douglassi) at high elevation

The short-horned lizard Phrynosoma douglassi was studied in a montane habitat (elevation of 2290 m) in the Guadalupe Mountains of Texas. The body temperatures (T_b) of active lizards were consistently between 35–36°C (grand mean=35.5°C) in the period from 0900 to 1800 h during the months of May through September. The lizards began their spring activity during April when environmental temperatures were still low. Although T_bs in April were significantly lower than during May through September, on sunny April days the lizards were able to maintain T_bs near 30°C even when air temperatures were as low as 1.5°C. P. douglassi at this site thermoregulated very effectively whenever they were not limited by the physical environment.     

Development of autonomic and behavioural thermoregulation in turkeys (Meleagris gallopavo)

1. 1.|Heat production (HP) and body temperature (T_b) measurements were conducted at ambient temperatures (T_a) between 10 and 40°C. In addition preference temperatures (PT) were determined in a temperature channel and T_b was measured at preferred T_a

2. 2.|The influence of age on T_b at constant, as well as at PT, was proved. Increasing age was accompanied by an elevation of T_b whereas HP remained constant in the mid-range of T_a

3. 3.|The lower T_b in the first days of life is suggested to result from a lower thermoregulatory set point during the postnatal period.

4. 4.|The PT were different for the observed types of behaviour. The PT at rest was higher than the PT during locomotion, food intake and drinking.

Development of thermoregulation in Hawaiian brown noddies (Anous stolidus pileatus)

1. 1.|Oxygen consumption ( ) and body temperture (T_b) of Hawaiian brown noddies (Anous stolidus pileatus [Aves: Laridae]) during late incubation and in the first 24 h after hatching were measured at ambient temperatures (T_a) between 28 and 38°C and between 15 and 43°C, respectively. Evaporative cooling by hatchings at T_a of 36–43°C was also measured.

2. 2.|Throughout the late incubation stages studied, and T_b both varied directly with T_a in an ectothermic pattern.

3. 3.|The hatchlings successfully regulated T_b at T_a between ca. 29 and 43°C.

4. 4.|The functional basis of the abrupt increase in thermoregulatory capacity with hatching is discussed.

Thermoregulatory responses to manipulations of photoperiod in wood mice Apodemus sylvaticus from high latitudes (57°N)

1. 1. The thermoregulatory responses to manipulations of photoperiod in wood mice (Apodemus sylvaticus), which were drawn from a population living at a high latitude (57°N) were studied.

2. 2. Mice captured in spring were acclimated to two different photoperiod regimes 16L:8D and 8L:16D at a constant ambient temperature of 24°C, for 3 weeks.

3. 3. Daily rhythms of body temperature, oxygen consumption and body temperature at various ambient temperatures, nonshivering thermogenesis (the response to a noradrenaline injection) and body mass were measured. Minimal overall thermal conductance was calculated for both groups.

4. 4. Acclimation to long photophase increased the thermoregulatory abilities at relatively high ambient temperatures while that of long-scotophase increased thermoregulatory abilities at low ambient temperatures.

5. 5. Changes in photoperiod may therefore be used as cues for seasonal acclimatization of thermoregulatory mechanisms in this population of wood mice.

     

Daily rhythms of nonshivering thermogenesis and responses to photoperiod manipulations in Apodemus mystacinus from two different ecosystems

Comparative physiology is an important tool for understanding adaptation to environment. Regulatory nonshivering thermogenesis (NST) is an essential mechanism in small mammals for coping with low ambient temperatures. Because of its geographical location and its sharp climatic changes across short distances, Israel offers conducting comparative studies between different populations of the same species. The aims of this study were: (1) to compare NST-capacity daily rhythms, between the two populations of the broad-toothed field mouse Apodemus Mystacinus—that of Mount Carmel (Mediterranean) and that of Mount Hermon (Subalpinic), (2) to compare the thermoregulatory daily rhythms response to photoperiod manipulations of mice from the two populations.

Mice were acclimated for at least 3 weeks to long scotophase (16D:8L-LS) and then to long photophase (16L:8D-LP) at a constant ambient temperature (T_a) of 24±1 °C. The following variables were compared at four different times of the day (06, 12, 18, 24 h): minimal body temperature (T_bMin), minimal oxygen consumption (VO₂Min) measured at the lower critical point and their response to noradrenaline (NA), 1.5 mg/1 kg.W_b injected s.c., (VO₂NA and T_bNA). NST-capacity was calculated as the ratio between VO₂NA and VO₂Min. The measurements were carried out at T_a of 28 °C and in light conditions matching those of acclimation. NA was injected after establishing VO₂Min and T_bMin. The values mean±SD are given for each measurement for n=6.

A three-way ANOVA revealed a significant difference between the two populations. Significant differences were revealed at different hours within populations under the different photoperiod regimes for different measured variables.     

Ambient temperature limits and stability of temperature regulation in telemetered male and female rats

Knowing the ambient temperature (T_a) limits of normothermia in laboratory rodents is important because their thermoregulatory responses are useful in studies of physiology, pharmacology and toxicology. The present study assessed the T_a limits of normothermia using radiotelemetry to monitor core temperature (T_c), heart rate (HR), and motor activity (MA) in unrestrained, male and female Long-Evans rats over a 24 h period. Rats were housed individually in acrylic cages with wire-screen tops and bottoms and maintained at T'_as ranging from 12 to 33.5°C for 24 h with food and water provided ad libitum on a 12:12 L:D photoperiod. The limits of normothermia (i.e. where there was no significant change in T_c) were <12–29.5°C for females and 14.5–29.5°C for males. T_c of males at T'_as of 12, 32, and 33.5°C increased significantly above the baseline T_c. Female rats had a lower T_c than males at the warmest and coldest T'_as. HR and MA were generally higher in females at all T'_as. Males appeared to be poorly adapted to thermoregulate at T'_as above 30°C as based on their excessively high T'_cs, low MA, and marked weight loss compared to that of the females. Within the limits of normothermia the stability of T_c regulation (i.e. [(ΔT_c/ΔT_a) × 100]/2) was ±1.3 and ± 0.9% for males and females, respectively, over a 24 h period. These data on the stability of T_c in the male and female rat provide a valuable framework to study the acute and chronic effects of drugs, chemicals and other agents that affect temperature regulation.     

Errors resulting from linear approximations in energy balance equations

1. 1.|Linearization techniques commonly used to solve energy budget equations of animals and plants can result in inaccurate estimates of body temperature(T_b).

2. 2.|Errors can be large when actual T_bs differ from the temperature used in linearization techniques; this is especially true for wet-skinned animals.

3. 3.|Iterative solutions of linearized equations can give accurate calculations of T_b.

Geographic variation in field body temperature of sceloporus lizards

1. Using data from the literature, I assessed how broad climatic patterns affected field body temperatures (T_b’s) of lizards in the genus Sceloporus.

2. Sceloporus at temperate latitudes had mean T_b’s of 35°C throughout their elevational range. This pattern is associated with “tropical” temperatures that extend into high north latitudes during the summer and the relatively low elevations occupied by the lizards.

3. At tropical latitudes, mean T_b declined from 35°C at low elevations to 31°C at high elevations. This pattern is associated with low seasonal variation in temperature at tropical latitudes and the relatively high elevations occupied by the lizards.     

Control of body temperature in shuttling ectotherms

During the daily increase of ambient temperatures (T_a), a thermoregulating ectothermic animal enters three successive phases: a basking-foraging phase, a proportional control phase and a sun-shade shuttling phase. The first and third phase consist of shuttling between two different microclimates, and a model is developed describing the relation between mean body temperature (T_b) and the lower operative environmental temperature. It is shown to be a curvilinear function, not a linear one as often has been assumed. The conditions for relating T_bs of ectothermic animals to T_as in a meaningful way is discussed, and the daily course of T_bs in shuttling animals is described. The model provides a reasonable fit to empirical values of T_bs in the tiger beetle Cicindela hybrida L.     

Daily rhythms of nonshivering thermogenesis in common spiny mice Acomys cahirinus under short and long photoperiods

Daily rhythms of nonshivering thermogenesis NST were studied in common spiny mice Acomys cahirinus, acclimated to different photoperiod regimes (16L:8D and 8L:16D) at a constant ambient temperature of 26°C. Noradrenaline NA (1.5 mg/kg subcutaneous) was injected at: 06:00, 12:00, 18:00 and 24:00 h (±15 min). NST was measured as the ratio between the maximal oxygen consumption (VO₂) as response to NA — VO₂NA and VO₂ measured at 26°C — VO_{2 min}. Rectal temperatures T_bNA and T_{b min} respectively were recorded at the end of VO₂ measurements. Significant variations in T_{b min}, T_bNA, and NST were revealed, under the two different photoperiod regimes. Significant differences in VO_{2 min}, NST, T_{b min} and T_bNA were also recorded within each photoperiod acclimation group. These results suggest that daily and photoperiod depended variations in the brown adipose tissue activity, presumably emerge from amount of unoccupied receptors or changes in the receptors affinity to NA.     

Infra-red irradiance and set point temperatures in behaviourally thermoregulating lacertid lizards

1. 1. Set point temperatures at which Podarcis muralis and Lacerta vivipara ceased basking (T_move; upper set point) and commenced basking (T_bask; lower set point) increased incrementally with increasing i.r. irradiance; values for all set point temperatures were higher in the former species.

2. 2. Changing the i.r. irradiance during a bask resulted in a shift in the upper set point temperature to a level intermediate between the values expected at constant previous and new irradiances (experiment with L. vivipara only).

3. 3. The changes in set-point temperatures following changes in i.r. irradiance were not due to changes in light intensity.

4. 4. The ability to respond to immediate changes in i.r. irradiance is adaptive for lizards in areas in which rapid changes in amounts of sunshine are a feature of the climate.

     

Behavioral thermoregulation of Bulla gouldiana (Gastropoda: Opisthobranchia: Cephalaspidea)

1. 1. The preferred temperature of Bulla gouldiana is 26.7–28.7°C.

2. 2. In constant scotophase, photophase, and light and dark photoperiod the organisms do not have a diel cycle of thermoregulation.

3. 3. It takes the animal 6–16 h to reach the preferred temperature.

4. 4. The lowest and highest temperatures visited were 11 and 33°C.

5. 5. Spawning of the species occurred in the thermal gradient between 27 and 28.5°C.

     

Correlated evolution of thermal characteristics and foraging strategy in lacertid lizards

1. We investigated the association between field body temperatures (T_b), field air temperatures (T_a), and their differences (Δ) with measurements of foraging activity (percentage of time moving (PTM), number of movements per minute (MPM) and proportion of prey attacked while moving (PAM)) for 25 species of lacertid lizards.

2. Lizards active at relatively high field body temperatures tended to have higher PTM and PAM values. We found no association between temperatures and MPM. The difference Δ did not co-vary with PTM and MPM, but showed a positive trend with PAM.

3. Our results seem robust with regard to the assumptions of different models of evolution and to the phylogenetic trees used.

The influence of hypothermia on the restoration of neural activity of brain slices from hibernating ground squirrels

1. 1. Neural activity was recorded in hippocampal slices from deep hibernating Yakut ground squirrels and in hippocampal and septal slices from non-hibernating animals.

2. 2. Slices were placed immediately after preparation in hypothermic conditions (3–4°C). Their activity was tested under standard conditions at 31°C in the incubation chamber. Some of the prepared slices were tested after maintenance in hypothermia for 2 or 24 h.

3. 3. In the hippocampal slices of hibernating ground squirrels, neural activity was present, irrespective of the period in hypothermia.

4. 4. Slices from guinea-pigs and hamsters did not possess neural activity after either 2 or 24 h of hypothermic treatment.

     

Thermal responses of the fresh water turtle Mauremys caspica to step-function changes in the ambient temperature

1. 1.|The turtle Mauremys caspica cools significantly faster than it heats in air. The heating/cooling ratio is 0.49.

2. 2.|The variation of body temperature in relation to time-course in response to a step-function change of environmental temperature, fitted to a second-order system improves that of a first-order system.

3. 3.|The gradient between ambient temperature (T_a) and equilibrium body temperature (T_b) increases significantly and progressively when ambient temperature rises over 25°C.

4. 4.|At 40°C thermoregulatory hyperventilation was detected, implying an increase in air convection requirement (ventilation relative to O₂ consumption, ).

The effect of acclimation on the acid-base status of pigeons exposed to high ambient temperatures

Arterial pH, PCO₂ (P_aCO₂), plasma bicarbonate [HCO₃⁻ and respiratory frequency were measured in pigeons exposed to ambient temperatures (T_aS) of 30–60°C. Acclimated, nonpanting birds regulated acid-base balance at normal levels, when exposed to T_as) between 30 and 53°C T_a. At higher T_as (55–60°C), both nonpanting and panting acclimated pigeons regulated pH at normal levels, 7.544 ± 0.011 (SD) and 7.531 ± 0.022 (SD), respectively, accompanied by a slight hypocapnia, 24.8 ± 4.0 Torr and 23.8 ± 2.49 Torr (P_aCO₂), respectively. Nonacclimated birds, exposed to 50°C T_a, endured a severe hypocapnia (P_aCO₂ of 9.1 ± 2.52 Torr) and alkalosis (pH of 7.702 ± 0.048). Thirteen exposures to > 50°C T_a, 4–6 h a day, resulted in a significant improvement in the capacity of the panting pigeon to maintain an almost normal acid-base balance, i.e. actual and standard [HCO₃⁻ of 22.6 ± 1.22 and 25.7 ± 1.10 mM/l, respectively, and only a slight hypocapnia (P_aCO₂ of 23.6 ± 3.9 Torr) and alkalosis (pH of 7.589). The suggestion that acclimation to high T_as (50–60°C) is needed for fine adjustment between the competing needs for heat dissipation, pulmonary gas exchange, and acid-base regulation in the heat-exposed pigeon is discussed.     

A test of the accuracy of operative temperature thermometers for studies of small ectotherms

1. 1. Various devices have been used to estimate the equilibrium body temperature of ectotherms occupying natural environments. We tested the accuracy of such devices under a range of conditions.

2. 2. We measured body temperatures of lizards (Sceloporus magister) exposed to short-wave radiation under varying convective conditions and compared these to temperatures of hollow metal casts duplicating the animal's shape and reflectivity, as well as to the temperatures of cylinders similar to those used by other workers.

3. 3. Casts equilibrated within 2–3°C of live animals, yielding errors of 14–37% of the radiation-produced elevation of body temperature.

4. 4. Various cylinders differed from animal body temperature more than lizard casts did, producing errors equally 33–53% of the radiation-produced elevation.

5. 5. It is imperative that workers using operative-temperature thermometers experimentally confirm the adequacy of the devices they use for the range of conditions encountered within a specific analysis.

     

Comparative aspects of the thermal biology of the short-tailed gerbil, Desmodillus auricularis, and the bushveld gerbil, Tatera leucogaster

1. 1. The response of oxygen consumption (VO₂), thermal conductance (C_d and C_min, body temperature (T_b), and evaporative water loss (EWL) of Tatera leucogaster and Desmodillus auricularis were measured over the range of ambient temperatures (T_a) from 5–35°C.

2. 2. Basal metabolic rate (BMR) of T. leucogaster was 0.841 ± 0.049 ml O₂ g⁻¹ h⁻¹ and lower than predicted, while that of D. auricularis was similar to the expected value (1.220 ± 0.058 ml O₂ g⁻¹ h⁻¹). D. auricularis had a high, narrow thermoneutral zone (TNZ) typical of nocturnal, xerophilic, burrowing rodents.

3. 3. D. auricularis and T. leucogaster regulated T_b over the range T_a = 5–35°C and kept EWL and dry thermal conductance at a minimum below the TNZ. However, the EWL of T. leucogaster increased rapidly above T_a = 30°C.

4. 4. After comparison with data from other species, it was concluded that there is an optimum size for xeric, nocturnal, burrowing rodents.

Early age cold conditioning in broiler chickens (Gallus domesticus): thermotolerance and growth responses

The influence of short repetitive cold exposure at an early age (cold conditioning—exposure to 15°C for 3 h at 3 and 4 days of age) on chickens’ thermotolerance during cold challenge (15°C) at 21 days of age was examined. The first cold exposure elicited a dramatic decline in body temperature (T_b) and a significant elevation in stress response (plasma corticosterone concentration); the second cold exposure resulted in moderate T_b and stress responses. Thereafter, the corticosterone concentration remained at a significantly lower level. Acute cold challenge of conditioned broilers at 21 days of age revealed better T_b and stress recovery during the first 24 h, and a significantly lower mortality rate thereafter. Conditioned chickens exposed to optimal conditions (22°C) achieved significantly higher body weights than others. It may be concluded that early cold conditioning improves thermotolerance in broiler chickens in later life.