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.

     

Respiratory heat loss and core temperatures during submaximal exercise

1. 1. This study examined the effect of inhaling air supersaturated with water on changes of core temperatures in submaximally exercising males.

2. 2. During exercise with inhalation of supersaturated relative to low-air-humidity air, a significant elevation in tympanic temperature (P = 0.009) and a significant decrease in esophageal temperature (P = 0.004) were observed.

3. 3. Forehead skin temperatures significantly decreased during humidified air inhalation (P = 0.02) supporting that this treatment induced greater thermolytic responses that cooled the skin.

4. 4. The results are consistent with the conclusion that heat loss from the upper airways directly influenced human cerebral temperatures as indexed by tympanic temperatures.

     

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.

     

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.

     

Temperature and the life-history strategies of sea turtles

1. 1. Sea turtles have a high fecundity, high mortality, great longevity life history strategy.

2. 2. With the exception of the leatherback, turtle distribution is constrained by the 20°C surface isotherm.

3. 3. All sea turtles exhibit temperature-dependent sex determination (TSD) with pivotal temperatures close to 29°C.

4. 4. It is suggested that hatchling sex ratio will vary chaotically because of TSD.

5. 5. Because of TSD and natal homing, sea turtles are likely to be adversely affected by global warming.

6. 6. TSD and global warming have implications for conservation/management of sea turtles.

     

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.

     

Changes in lipid peroxidation, superoxide dismutase activity, ascorbic acid and phospholipid content in liver of freshwater catfish Heteropneustes fossilis exposed to elevated temperature

1. 1. Lipid peroxidation, superoxide dismutase (SOD) activity, ascorbic acid (AsA) and individual phospholipid contents in liver of fresh water cat fish Heteropneustes fossilis were measured after exposure to different temperatures (25, 27, 32, 37°C) at various times (1–4 h).

2. 2. Lipid peroxidation and superoxide dismutase activity were significantly increased with increases in temperature at various times.

3. 3. Ascorbic acid content was depleted when temperature was increased.

4. 4. After temperature exposure, phosphatidyl inositol was increased while phosphatidyl choline, phosphatidyl serine and phosphatidyl ethanolamine were depleted. Phosphatidic acid level did not change.

5. 5. The findings indicated an increased oxidative stress in liver following increases in temperature at various times. Concurrent with the increase in lipid peroxidation, superoxide dismutase activity and ascorbic acid from the liver of fish varied. It is suggested that depletion of major individual phospholipids following temperature exposure could be due to superoxide created oxidative stress in the liver.

     

Reproductive status and torpor of the marsupial Sminthopsis crassicaudata: Effect of photoperiod

1. 1. We investigated the effects of photoperiod on the reproductive state and the occurrence and pattern of torpor in male Sminthopsis crassicaudata.

2. 2. Testes regressed when animals were exposed to a short photoperiod (L:D 8:16) and recrudesced under a long photoperiod (L:D 16:8).

3. 3. Animals entered torpor under both photoperiods and no significant differences were observed in the frequency or physiological variables of torpor of S. crassicaudata between the short and long photoperiods.

4. 4. The differences in the response to photoperiod in thermal physiology and reproduction suggest that, unlike in many rodent species, torpor and reproduction in S. crassicaudata are controlled by separate environmental cues and mechanisms.

     

Response of brown mussel, Perna indica, to elevated temperatures in relation to power plant biofouling control

1. 1. Results of a study on lethal and sublethal responses of different size groups of the tropical brown mussel, Perna indica, when exposed to different temperatures are presented.

2. 2. Exposure to a temperature of 38°C showed 100% mortality of 9 mm size group mussels in 120 min.

3. 3. Mortality was dependent on age (size) of the mussels, young ones being more susceptible than older ones.

4. 4. All size groups showed a progressive reduction in physiological activities such as filtration rate, foot activity and byssus thread production when temperature was increased from 30°C.

5. 5. This study suggests that heat treatment is an attractive alternative to chlorination for mussel fouling control in tropical power stations.

     

How are the life history strategies of Antarctic terrestrial invertebrates influenced by extreme environmental conditions?

1. 1. Features of life history strategies of Antarctic terrestrial invertebrates are reviewed and compared with the predictions of two widely-used general life history models.

2. 2. Many features observed are consistent with the predictions of “adversity-” or “stress-selected” life histories, although “ruderal” characteristics are also observed.

3. 3. Many features are plesiotypic for the taxonomic groups concerned, suggesting a lack of evolved adaptations within the Antarctic biota.

4. 4. A large degree of flexibility is found in the life histories; this flexibility itself may allow passage of environmentally-imposed selective filters limiting colonisation and development in isolated and extreme terrestrial habitats.

5. 5. In general, Antarctic terrestrial invertebrates may be regarded as pre-adapted for survival of the various stresses imposed by their extreme environment.

     

The effect of shielding the parietal eye of Podarcis muralis on behavioral thermoregulation

1. 1. Body temperatures (T_bs) and thermoregulatory precision of 7 sham shielded and 7 parietal eye shielded Podarcis muralis were measured in a linear thigmothermal gradient over a 24 h period.

2. 2. Shielding the parietal eye did not alter the mean T_b selected over the 24 h period.

3. 3. Both groups selected T_bs that did not differ between photophase and scotophase.

4. 4. Shielding the parietal eye did not influence thermoregulatory precision when measured over the 12 h of photophase, but from 0600–1200 h EST parietal eye shielded lizards thermoregulated more precisely than sham shielded lizards.

     

Interactions of environmental temperature with photoperiod in determining age at maturity in a semelparous polychaete Nereis (neanthes) virens sars

1. 1. Larger members of the Polychacta exhibit two contrasting life cycles: semelparous in the Nereidae, iteroparous in most others.

2. 2. In semelparous forms environmental interaction determines age at reproduction and fecundity in the single spawning event whereas in iteroparous forms such interaction influences the variable age specific reproductive effort.

3. 3. Development of aquaculture has created conditions where organisms are grown under conditions of optimum temperature for growth and unlimited food.

4. 4. We present data on the life history responses (reaction norms) of the semelparous Nereis virens in which age at death in natural populations varies between 3 to 8+ years.

5. 5. In Nereis virens minimum life span (= generation time) in culture is one year but the lifespan remains modular 12 months without manipulation of photoperiod.

6. 6. Environmental temperature plays two roles: i) in conjunction with energy availability to determine “age at first/only reproduction” and secondly as an element (with photoperiod) in the control of gametogenic processes imposing seasonality on the life cycle.

7. 7. The observations suggest that long generation time in natural populations of N. virens is associated with reduced growth rate and that low growth rate is associated with reproduction at a larger size.

     

Carp expresses fast skeletal myosin isoforms with altered motor functions and structural stabilities to compensate for changes in environmental temperature

1. 1. Myosin and its subfragment-1 (Sl) from carp acclimated to 10°C showed higher actin-activated Mg²⁺-ATPase activity and lower thermostability than their counterparts from carp acclimated to 30°C. Accordingly, filament velocity for the 10°C-acclimated carp myosin was higher at any measuring temperatures from 3 to 23°C than that for the 30°C-acclimated carp myosin.

2. 2. Three types of cDNA clones encoding myosin heavy chains were isolated from thermally acclimated carp. The 10 and 30°C types were predominating in carp acclimated to 10 and 30°C, respectively, whereas the intermediate type was found as a minor component in the 10°C-acclimated carp with an intermediate feature in both DNA nucleotide and deduced amino acid sequences between those of the 10 and 30°C types.

3. 3. The three types of myosin rod all showed a typical coiled-coil structure of -helices. DSC scans demonstrated that myosin rod prepared from carp acclimated to 10°C had a lower thermostability than that from carp acclimated to 30°C, showing that low thermostability in cold-acclimated carp myosin prevails over the entire molecule.

4. 4. cDNA clones encoding myosin alkali light chains were isolated from thermally acclimated carp. Northern blot analysis showed that the ratios of LC3/LC1 mRNAs were significantly higher (3.92) in the 30°C- than 10°C-acclimated (3.10) carp.

     

Temperature and water relations in desert bees

1. 1. Desert bees do not show significant differences in most thermal parameters; mean endothermic warm-up rates are similar to those of temperate species, with no special cooling mechanisms, and normal upper critical temperatures (unlike desert ants and beetles). Thermoregulatory abilities may however be improved.

2. 2. They show the whole range of possible water balance problems; small species are acutely water-stressed when foraging, but large bees suffer from excessive generation of metabolic water in flight.

3. 3. Activity patterns are therefore either matinal, crepuscular or bimodal; essentially desert bees avoid heat and adapt to cold desert dawns and dusks. Desert plants must be coevolved to offer appropriate rewards and match the physiological constraints on their pollinators.

4. 4. Endothermy in bees may have evolved primarily in arid zones, and served as a pre-adaptation for subsequent invasion of cool temperate biomes.

     

Anergy or cell death induced by low physiological temperature in mitogen-stimulated human T lymphocytes

1. 1. Human T cell proliferation is suppressed at 27°C, and is both diminished and delayed at 32°C.

2. 2. Temperature shift-up and viability assays indicated that concanavalin A stimulation at 27°C induced cell death in contrast to a transient unresponsiveness (anergy) induced by monoclonal anti-CD3 antibody (CD3) and the superantigen, staphylococcal exterotoxin B.

3. 3. Phytohemagglutinin also induced cell death at 27°C; however, some cells remained viable and proliferation occurred when such cultures were subsequently moved to 37°C.

4. 4. Low temperature suppression of T cell activation was not overcome by a mixture of phorbol ester and calcium ionophore indicating a probable block post-protein kinase C activation. This was confirmed in temperature shift-down assays where incubation for 18–24 h at 37°C was required to bypass the block at 27°C.

5. 5. With the exception of CD3, stimulation at 27°C with the mitogens resulted in interleukin-2 secretion, indicating that the low temperature block(s) is a relatively late event in cell activation.

     

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.

     

Dehydration and food deprivation exacerbate mouse cerebral microvascular responses to local hyperthermia

1. 1. Effects of 1-day deprivation from water, food or both on responses of mice pial microvessels to local cerebral hyperthermia were compared to fed mice and with access to water.

2. 2. A set of protocol for all groups was followed, which involved microsurgery and utilized intravital videomicroscopy. Core body temperature was kept at 37°C and hyperthermic exposure was applied locally by heating the artificial cerebrospinal fluid irrigating the brain surface, at 45°C for 25 min.

3. 3. Monitored responses included intravascular thrombo-embolic events and changes in microvascular diameter. Dehydration and food deprivation shortened the time for appearance of passing emboli and lowered the thermal threshold at which thrombo-embolic processes occur.

4. 4. Arteriolar constriction was observed in all groups, coupled with full occlusion.

5. 5. Data of this study revealed that dehydration and food deprivation exacerbate pial microcirculatory responses to local hyperthermia.

     

How to measure the thermal death of Daphnia? A comparison of different heat tests and effects of heat injury

1. 1. The thermal death point of the water flea Daphnia magna (age < 24 h, cultured at 20°C) varied considerably depending on the method used. The median lethal dose (LD₅₀), induced by an acute 24 h heat exposure was 34.8°C. It was 37.8°C following a thermal shock for 15 min, and it was 39.4°C when a continuous temperature increase (0.2°C/min) was used.

2. 2. Heat death temperature of daphnids was related to the acute heating rate.

3. 3. The logarithm of median lethal time (Lt₅₀) of daphnids, kept at a constant high temperature, had a linear relationship to temperature (°C) within the range of 28.0–38.5°C.

4. 4. The mortality after heat exposure increased with recovery time at 20°C for up to 3 days.

5. 5. The animals which survived the heat exposure produced eggs and offspring. Furthermore, no time lag in development between the control and heat exposure group was observed.

6. 6. The comparison of the results made by different heat tests categorized to Methods 1 and 2 by Precht (1973), for use in the determination of lethal limits of ectotherms, has been discussed.

     

A simple index of standard operative temperature for mule deer and cattle in winter

1. 1. Scientists often use ambient temperature, relative humidity, or windspeed alone to describe an animal's thermal environment. Standard operative temperature (T_es) incorporates solar and thermal radiation, ambient temperature, and windspeed with a species' resistance to heat loss; thus it more accurately represents an animal's thermal environment. Standard operative temperature is not often recorded in the field because of instruments needed to measure short- and long-wave radiation.

2. 2. Our objective was to determine if regression equations could relate simple micrometeorological measurements to T_es for mule deer and cattle in winter.

3. 3. Blackglobe and ambient temperatures, windspeed, net radiation, total radiation, albedo, and ground surface temperature were recorded during one winter in a field in Bozeman, Montana. We used species specific resistance values for mule deer and cattle in winter to calculate T_es for both species. Then, we regressed T_es with blackglobe and ambient temperatures, and windspeed. The mule deer regression model was applied to an independent data set to determine if it worked well under varying weather conditions.

4. 4. The mule deer and cattle regression models represented T_es for both species well (adjusted R² 0.96 and 0.94, respectively). The mule deer regression model also represented the independent data set well. Standard operative temperatures predicted by our model and those predicted by the independent data set were highly correlated (r > 0.96 for four different comparisons). Our simple micrometeorological measurements are suitable predictors of T_es for mule deer and cattle in winter.

     

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.