Activity, blood temperature and brain temperature of free-ranging springbok

We used miniature data loggers to record temperature and activity in free-ranging springbok (Antidorcas marsupialis) naturally exposed to severe nocturnal cold and moderate diurnal heat. The animals were active throughout the day and night, with short rests; the intensity of activity increased during daylight. Arterial blood temperature, averaged over many days, exhibited a circadian rhythm with amplitude <1 °C, but with a wide range which resulted from sporadic rapid deviations of body temperature. Peak blood temperature occurred after sunset. Environmental thermal loads had no detectable effect on blood temperature, even though globe temperature varied by >10 °C from day to day and >20 °C within a day. Brain temperature increased approximately linearly with blood temperature but with a slope <1, so that selective brain cooling tended to be activated at high body temperature, but without a precise threshold for the onset of brain cooling. Low activity attenuated selective brain cooling and high activity abolished it, even at high brain temperature. Our results support the concept that selective brain cooling serves to modulate thermoregulation rather than to protect the brain against heat injury. Accepted: 7 January 1997     

Effects of temperature and wind on facial temperature, heart rate, and sensation.

Skin temperature measurements of the face have shown that the cheek cools faster than the nose and the nose faster than the forehead. The cooling effect of wind is maximum at wind speeds between 4.5 and 6.7 m/s. Cold winds produce significant bradycardia, which is, however, much more pronounced during the expiratory phase of respiration. A significant correlation was noted between cooling of face and the reflex bradycardia observed. Similarly, a very significant correlation was noted between drop in skin temperature and subjective evaluation of cold discomfort. Consequently, the drop in skin temperature, reflex bradycardia, and subjective evaluation are parameters which are directly affected by cold wind and can be used as adequate indicators of the degree of discomfort. When comparing the present results with the windchill index, it was found that in the zone described as "dangerously cold" the index fits well with the physiological measurements. In the zone described as "bitterly cold," the index by comparison with actual skin temperature measurements and subjective evaluation underestimates the cooling effects of combined temperature and wind by approximately 10 degrees C.     

Chill-coma temperature in Drosophila: effects of developmental temperature, latitude, and phylogeny

We modify and apply a nonlethal technique for rapidly quantifying the cold tolerance of large numbers of Drosophila and other small insects. Flies are transferred to individual vials, cooled in groups in progressive 0.5 degrees C steps, and checked for loss of righting response (chill-coma temperature [T(cc)]). Flies recover quickly when transferred to ambient temperature, and thus this technique potentially can be used in selection experiments. We applied this technique in several experiments. First, we examined the sensitivity of T(cc) to developmental temperature. Drosophila melanogaster (Congo, France), Drosophila subobscura (Spain, Denmark), and Drosophila ananassae (India) were reared from egg to adult at 15 degrees, 18 degrees, 25 degrees, or 29 degrees C, transferred to 15 degrees C for several days, and then progressively chilled: T(cc) was positively related to developmental temperature, inversely related to latitude of the population, but independent of sex. The sensitivity of T(cc) to developmental temperature (acclimation flexibility) was marked: T(cc) shifted on average 1 degrees for each 4 degrees C shift in developmental temperature. Among 15 species of the obscura group of Drosophila, T(cc) varied from -0.1 degrees to 4.5 degrees C; T(cc) was inversely related to latitude in both nonphylogenetic and phylogenetically based ANCOVA (standardized independent contrasts) and was unrelated to body size.     

Water, temperature and life

Cold is the fiercest and most widespread enemy of life on earth. Natural cold adaptation and survival are discussed in terms of physicochemical and biochemical water management mechanisms, relying on thermodynamic or kinetic stabilization. Distinctions are drawn between general effects of low temperature (chill) and specific effects of freezing. Freeze tolerance is a misnomer because tolerance does not extend to the cell fluids. Freezing is confined to the extracellular spaces where it acts as a means of protecting the cytoplasm against freezing injury. Freeze resistance depends on the phenomenon of undercooling, a survival mechanism that relies on the long-term maintenance of a thermodynamically highly unstable state. Correct water management involves many factors, among them the control of membrane composition and transmembrane osmotic equilibrium, the biosynthesis of compounds able to afford protection against injury through freeze desiccation and the availability (or inactivation) of biogenic ice nucleation catalysts.     

Light, temperature, and anthocyanin production

Temperature affects the total amount, the time course, and the red/far-red effectiveness ratio of light-dependent anthocyanin production in Brassica oleracea L. seedlings. Some of the effects of temperature on anthocyanin production in cabbage are in agreement with the predictions of a model proposed by JK Wall and CB Johnson (1983 Planta 159: 387-397) for the effects of temperature on the state of phytochrome and on the expression of phytochrome-mediated high irradiance responses, but others are not. The lack of a complete agreement between experimental results and model predictions might be due to factors related to the experimental system used or to limitations of the model or both.     

Relationships between the circadian rhythms of finger temperature, core temperature, sleep latency, and subjective sleepiness

Skin temperature circadian rhythms have been explored relatively recently. It has been suggested that distal and proximal skin temperature changes play a role in the regulation of the core temperature circadian rhythm and sleepiness. The authors investigated the circadian finger and core temperature rhythms in conjunction with the circadian rhythms of subjective and objective sleepiness. Fourteen healthy, young, good sleepers participated in a modified constant-routine procedure in which palmar finger temperature, rectal temperature, subjective sleepiness, and objective sleep latency were measured half-hourly across a 48-h period of enforced wakeful bed rest. Individual curves were adjusted to the group mean temperature minimum time of 0500 h and averaged to create the 4 mean curves. The 5 possible cross-correlation curves between these 4 measures were calculated for half-hourly phase lags from 12 h before to 12 h after the group mean core temperature minimum time. Maximum cross-correlations for each curve suggested that finger temperature preceded core temperature by 3 h (r = -0.22), and subjective sleepiness followed core temperature by 0.5 h (r = -0.33) and objective sleepiness by 2 h (r = 0.29). Although these data are correlational, they are consistent with the notion that finger temperature changes drive core temperature changes, which determine changes of subjective and objective sleepiness.     

Naloxone, naltrexone and body temperature

The temperature effects of naloxone and naltrexone (1-30 mg/kg) were examined in well habituated male rats. These drugs had a similar time course and potency, producing a dose-dependent hypothermia followed several hours later by a hyperthermia. A subsequent study found that not only did 30 mg/kg of naloxone or naltrexone produce an equivalent hypothermia but this hypothermia was just as pronounced during the dark as in the light part of the cycle.     

Aftereffects of low and high temperature pretreatment on leaf resistance, transpiration, and leaf temperature in xanthium

Leaf resistance for water vapor (total diffusion resistance minus boundary layer resistance), transpiration, and leaf temperature were measured in attached leaves of greenhouse-grown Xanthium strumarium L. plants that had been pretreated for 72 hours with high (40 C day, 35 C night), or low (10 C day, 5 C night) air temperatures. Measurements were made in a wind tunnel at light intensity of 1.15 cal cm⁻² min⁻¹, air temperatures between 5 and 45 C, and wind speed of 65 cm sec⁻¹. Leaf resistances in low temperature pretreated plants were higher (8 to 27 sec cm⁻¹) than in controls or high temperature pretreated plants (0.5 to 3 sec cm⁻¹) at leaf temperatures between 5 and 25 C. Thus, the pretreatment influenced stomatal aperture.     

桃小食心虫的发育起点温度和有效积温

在17～29℃、RH80%±7%和光周期L:D=15:9的条件下,测定了桃小食心虫Carposina sasakii Matsumura各虫态的发育历期,计算了桃小食心虫卵、幼虫、蛹和全世代的发育起点温度和有效积温。结果表明,各虫态的发育历期随着温度的升高而缩短,各虫态的发育速率与温度之间具有良好的线性关系。桃小食心虫卵、幼虫、结茧前期、蛹及生殖前期的发育起点温度分别为10.02、9.44、10.58、10.09和9.51℃,有效积温分别为87.3、238.6、10.7、156.9和31.6日·度,全世代的发育起点温度和有效积温分别为9.22℃和543.2日·度。     

Consequences of temperature and temperature variability on swimming activity,group structure,and predation of endangered delta smelt

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Hemolymph microbiome of Pacific oysters in response to temperature,temperature stress and infection

Microbiota provide their hosts with a range of beneficial services, including defense from external pathogens. However, host-associated microbial communities themselves can act as a source of opportunistic pathogens depending on the environment. Marine poikilotherms and their microbiota are strongly influenced by temperature, but experimental studies exploring how temperature affects the interactions between both parties are rare. To assess the effects of temperature, temperature stress and infection on diversity, composition and dynamics of the hemolymph microbiota of Pacific oysters (Crassostrea gigas), we conducted an experiment in a fully-crossed, three-factorial design, in which the temperature acclimated oysters (8 or 22 °C) were exposed to temperature stress and to experimental challenge with a virulent Vibrio sp. strain. We monitored oyster survival and repeatedly collected hemolymph of dead and alive animals to determine the microbiome composition by 16s rRNA gene amplicon pyrosequencing. We found that the microbial dynamics and composition of communities in healthy animals (including infection survivors) were significantly affected by temperature and temperature stress, but not by infection. The response was mediated by changes in the incidence and abundance of operational taxonomic units (OTUs) and accompanied by little change at higher taxonomic levels, indicating dynamic stability of the hemolymph microbiome. Dead and moribund oysters, on the contrary, displayed signs of community structure disruption, characterized by very low diversity and proliferation of few OTUs. We can therefore link short-term responses of host-associated microbial communities to abiotic and biotic factors and assess the potential feedback between microbiota dynamics and host survival during disease.     

Temperature response of photosynthesis in C3, C4, and CAM plants: temperature acclimation and temperature adaptation

Most plants show considerable capacity to adjust their photosynthetic characteristics to their growth temperatures (temperature acclimation). The most typical case is a shift in the optimum temperature for photosynthesis, which can maximize the photosynthetic rate at the growth temperature. These plastic adjustments can allow plants to photosynthesize more efficiently at their new growth temperatures. In this review article, we summarize the basic differences in photosynthetic reactions in C₃, C₄, and CAM plants. We review the current understanding of the temperature responses of C₃, C₄, and CAM photosynthesis, and then discuss the underlying physiological and biochemical mechanisms for temperature acclimation of photosynthesis in each photosynthetic type. Finally, we use the published data to evaluate the extent of photosynthetic temperature acclimation in higher plants, and analyze which plant groups (i.e., photosynthetic types and functional types) have a greater inherent ability for photosynthetic acclimation to temperature than others, since there have been reported interspecific variations in this ability. We found that the inherent ability for temperature acclimation of photosynthesis was different: (1) among C₃, C₄, and CAM species; and (2) among functional types within C₃ plants. C₃ plants generally had a greater ability for temperature acclimation of photosynthesis across a broad temperature range, CAM plants acclimated day and night photosynthetic process differentially to temperature, and C₄ plants was adapted to warm environments. Moreover, within C₃ species, evergreen woody plants and perennial herbaceous plants showed greater temperature homeostasis of photosynthesis (i.e., the photosynthetic rate at high-growth temperature divided by that at low-growth temperature was close to 1.0) than deciduous woody plants and annual herbaceous plants, indicating that photosynthetic acclimation would be particularly important in perennial, long-lived species that would experience a rise in growing season temperatures over their lifespan. Interestingly, across growth temperatures, the extent of temperature homeostasis of photosynthesis was maintained irrespective of the extent of the change in the optimum temperature for photosynthesis (T _opt), indicating that some plants achieve greater photosynthesis at the growth temperature by shifting T _opt, whereas others can also achieve greater photosynthesis at the growth temperature by changing the shape of the photosynthesis–temperature curve without shifting T _opt. It is considered that these differences in the inherent stability of temperature acclimation of photosynthesis would be reflected by differences in the limiting steps of photosynthetic rate.     

Increasing temperature, not mean temperature, is a cue for avian timing of reproduction

Timing of reproduction in temperate-zone birds is strongly correlated with spring temperature, with an earlier onset of breeding in warmer years. Females adjust their timing of egg laying between years to be synchronized with local food sources and thereby optimize reproductive output. However, climate change currently disrupts the link between predictive environmental cues and spring phenology. To investigate direct effects of temperature on the decision to lay and its genetic basis, we used pairs of great tits (Parus major) with known ancestry and exposed them to simulated spring scenarios in climate-controlled aviaries. In each of three years, we exposed birds to different patterns of changing temperature. We varied the timing of a temperature change, the daily temperature amplitude, and the onset and speed of a seasonal temperature rise. We show that females fine-tune their laying in response to a seasonal increase in temperature, whereas mean temperature and daily temperature variation alone do not affect laying dates. Luteinizing hormone concentrations and gonadal growth in early spring were not influenced by temperature or temperature rise, possibly posing a constraint to an advancement of breeding. Similarities between sisters in their laying dates indicate genetic variation in cue sensitivity. These results refine our understanding of how changes in spring climate might affect the mismatch in avian timing and thereby population viability.