Effect of thermal acclimation on thermal preference,resistance and locomotor performance of hatchling soft-shelled turtle

The significant influence of thermal acclimation on physiological and behavioral performance has been documented in many ectothermic animals, but such studies are still limited in turtle species. We acclimated hatchling soft-shelled turtles Pelodiscus sinensis under three thermal conditions （10, 20 and 30~C） for 4 weeks, and then measured selected body temperature （Tsel）, critical thermal minimum （CTMin） and maximum （CTM~x）, and locomotor performance at different body temperatures. Thermal acclimation significantly affected thermal preference and resistance of P sinensis hatchlings. Hatchling turtles accli- mated to 10~C selected relatively lower body temperatures and were less resistant to high temperatures than those acclimated to 20~C and 30~C. The turtles＇ resistance to low temperatures increased with a decreasing acclimation temperature. The thermal re- sistance range （i.e. the difference between CTM~x and CTMin, TRR） was widest in turtles acclimated to 20~C, and narrowest in those acclimated to 10~C. The locomotor performance of turtles was affected by both body temperature and acclimation tem- perature. Hatchling turtles acclimated to relatively higher temperatures swam faster than did those acclimated to lower temperatures. Accordingly, hatchling turtles acclimated to a particular temperature may not enhance the performance at that temperature. Instead, hatchlings acclimated to relatively warm temperatures have a better performance, supporting the ＂hotter is better＂ hypothesis.     

Metabolic enzymes in seasonally acclimatized and cold acclimated rufous-collared sparrow inhabiting a Chilean Mediterranean environment

Due to the higher energy requirements of birds during winter, it is predicted that the activities of metabolic enzymes （e.g., citrate synthase, CS and cytochrome C oxidase, COX） should increase in tandem with increases in rates of energy expendi ture （e.g., basal metabolic rate, BMR）. However, there is mixed support for the hypothesis of enzymatic acclimatization. Fur thermore, there is little information about the effect of ambient temperature on energetics and tissue enzyme activity levels in passerines inhabiting seasonal Mediterranean environments. In this study we evaluated the interplay between BMR and enzyme activities of freshly caught individuals of the passerine Zonotrichia capensis in winter and summer in a Mediterranean environment from central Chile, and also in warm （30℃） and cold （15℃） labacclimated birds. The results revealed a lack of seasonal variation in BMR, thermal conductance and in the activity of CS and COX. However, we found higher BMR and lower thermal conductance in coldacclimated than in warmacclimated birds. Also, total CS activity was higher in the flight muscles of coldacclimated than in warmacclimated birds. We found also a significant correlation between BMR and total CS activity in pectoral muscle. Although some authors have suggested that BMR mainly depends on the metabolic intensity and mass of internal organs, our results revealed that skeletal muscles such as the flight muscles may also affect BMR. Finally, differences in the accli mation and acclimatization responses in Rufouscollared sparrows suggest that largescale oscillations in the physical environment might maintain the capacity for flexibility in thermogenic traits through generations .     

The effects of wind and thermal radiation on thermal responses during rest and exercise in a cold environment

1. 1. The purpose of this study was to investigate the effects of thermal radiation and wind on thermal responses at rest and during exercise in a cold environment.

2. 2. The experimental conditions were radiation and wind (R + W), no radiation and wind (W), radiation and no wind (R), no radiation and no wind (C).

3. 3. The air temperature was −5°C. Thermal radiation was 360 W/m². Air velocities were 0.76, 1.73 and 2.8 m/s. Rectal and skin temperatures, heart rate and oxygen consumption were recorded. Thermal and comfort sensations were questioned.

4. 4. There are no significant effects of thermal radiation and wind on the physiological responses except the mean skin temperature. There are significant effects on the mean skin temperature (P < 0.01) and thermal sensation (P < 0.05).

Surface temperatures of growing pigs in relation to the duration of acclimation to air temperature or draught

The aim of this work was to study to what extent surface temperatures of growing pigs are altered during acclimation to a change of the air temperature and to exposure to draught.

4 groups of 10 pigs (Large White × Dutch Landrace) of approximately 10 weeks old were used. They were housed in 2 calorimeters with 2 pens each. In the reference chamber air temperature was kept constant at 25°C, in the other chamber air temperature could be lowered to 15°C, and a draught was also applied. Surface temperatures of the pigs were measured by means of Probey® Thermal Video System, with an accuracy of ±0.3°C.

Surface temperatures of growing pigs were obviously related to air temperature, draught and the duration of food withdrawal. Acclimation to air temperature or draught as measured by surface temperatures was not observed between days, but within and between night periods.

Also indications of huddling, vasocontriction and even cold-induced vasodilatation within the neck, chest and abdomen region of the pigs' body surface were observed.     

The Seasonal Acclimatisation of Locomotion in a Terrestrial Reptile,Plestiodon chinensis （Scincidae）

Studies of the seasonal acclimatisation of behavioural and physiological processes usually focus on aquatic or semi-aquatic ectotherms and focus less effort on terrestrial ectotherms that experience more thermally heterogeneous environments. We conducted comparative studies and thermal acclimation experiments on the locomotion of the Chinese skink （Plestiodon chinensis） to test whether seasonal acclimatisation in locomotion exists in these terrestrial ectothermic vertebrates, and whether seasonal acclimatisation is predominantly induced by thermal environments. In natural populations, skinks ran faster during the summer season than during the spring season at high-test temperatures ranging from 27℃ to 36℃ but not at low-test temperatures ranging from 18℃ to 24℃. In contrast, the thermal acclimation experiments showed that the cold-acclimated skinks ran faster than the warm-acclimated skinks at the low- test temperatures but not at high-test temperatures. Therefore, the seasonal acclimatisation occurs to P chinensis, and may be induced by temperature as well as other factors like food availability, as indicated by the seasonal variation in the thermal dependence of locomotion, and the discrepancy between seasonal acclimatisation and thermal acclimation on locomotion.     

Effects of photoperiod and temperature on diapause induction in Conogethes punctiferalis （Lepidoptera： Pyralidae）

The yellow peach moth, Conogethes punctiferalis （Guenee）, a multivoltine species that overwinters as diapausing larvae, is one of the most serious insect pests on maize in China. Effect of photoperiod and temperature on larval diapause was examined under empirical laboratory conditions. Short-day treatments caused larval diapause at 25℃, and the critical photoperiod was between 12 and 13 h （or 12 h 51 min） light per day. No sensitive instar was identified for diapause induction under alternated short- （L ： D 11 ： 13 h） and long-day （L ： D 14 ： 10 h） treatments at different larval stages. However, accumulative treatment of three instars and 10 d under short-day treatment was required for the induction of 50% larval diapause. All larvae entered diapause at 20℃, whereas less than 3% did so at 30℃, irrespective of the long- or short-day treatment. Furthermore, under the short-day treatment, more than 90% of larvae went into diapause with temperatures ≤ 25℃, but less than 17% did so at 28℃. In contrast, under the long-day treatment, less than 19% of larvae went into diapause with temperatures ≥23 ℃. The forward shift （5℃） of critical temperature under the long-day regime demonstrated the compensatory effect of temperature and photoperiod on diapause induction. In conclusion, C. punctiferalis had a temperature-dependent type Ⅰ photoperiodic diapause response; there was no sensitive instar for diapause determination, but the photoperiodic accumulation time countermeasures both of the short-day cycles and the number ofinstars exposed, and the photoperiodic diapause response, was a temperature-compensated phenomenon.     

Heat flow of the paraplegic and able-bodied lower limb during resting heat exposure

1. The heat flow of paraplegic (PA) and able-bodied (AB) subjects were determined at rest in cool and warm conditions.

2. During heat exposure upper body sites for both groups showed heat loss, whereas the lower body sites of the PA groups showed heat gain.

3. During heat exposure, a systematic difference between groups in the relationship between heat flow and calf-skin temperature existed.

4. In conclusion, heat storage appears to be localised in PA subjects at rest and centralised for AB subjects.

Thermal sensations during simultaneous warming and cooling at theh forearm: A human psychophysical study

1. 1.The forearm of 5 female subjects ws thermally stimulated by 2 sets of interposed servo-thermodes that respectively drove skin temperature at ±0.1°C.s⁻¹ for 25 s and then held it constant. Mean skin temperature remained constant. The sequence was repeated at adapting temperatures between 22.5 and 37.5°C.

2. 2.Thermal sensations, continuously reported by the position of a dial, were warmer for heterogeneous thermal stimuli than for homogeneous stimuli when mean skin temperature was greater than 30°C and cooler when less than 27.5°C.

3. 3.This phenomenon is inconsistent with a single additive contribution of “warm” and “cold” information to thermal sensations.

Diurnal change in psychological and physiological responses to consistent relative humidity

Diurnal changes in physiological and psychological responses to consistent relative humidity (RH) conditions were investigated in the present study. Lightly clothed six male and six female subjects participated in the first experiment at 40% and 50% RH, and seven male and seven female subjects participated in the second experiment at 60%, 70%, and 80% RH. Both experiments were conducted at 28 °C air temperature (T_a) from 9:00–18:30. Skin temperatures, local heat flux rates and tympanic temperature (T_ty) were monitored at 2-min intervals throughout the experimental period. Body weight loss and oxygen consumption rate were measured during the 9:30–10:30, 13:30–14:30, and 17:30–18:30 periods. Thermal sensation and thermal comfort responses were recorded at the same periods. The amount of heat loss was greater than metabolic heat production (M) in the male subjects but was well balanced with M in the female subjects. A morning increase in T_ty at 50%–80% RH was observed, and mean skin temperature (${\bar{\text{T}}}_{\text{sk}}$) at 70% and 80% RH was significantly higher (p < 0.05) than T_sk at 40% and 50% RH in both subject groups. Although difference in the relationship between thermal sensation and ${\bar{\text{T}}}_{\text{sk}}$ based on sex was confirmed, diurnal changes in thermal sensation were observed in both subject groups based on the responses of “warm” in the morning but “neutral” or “slightly warm” in the evening at 70% and 80% RH. This result demonstrates that high RH may be acceptable in the late afternoon and evening at 28 °C and indicates that dynamic control of RH during the daytime (e.g., low RH in the morning and high RH in late afternoon) may be beneficial to save energy when using air-conditioning.     

The effect of acclimation temperature and the removal of peripheral temperature receptors on body temperature preference in the cockroach, Periplaneta americana

1. 1.|Body temperature preferences were compared between cockroaches acclimated to different ambient temperatures and between 25°C acclimated cockroaches and cockroaches deprived of their peripheral temperature receptors.

2. 2.|Acclimation to 35°C resulted in a significantly higher mean body temperature and low body temperature selected compared with 25°C acclimated cockroaches.

3. 3.|Cockroaches deprived of their peripheral temperature receptors showed a significantly higher mean high body temperature selected when compared to normal 25°C acclimated cockroaches.

4. 4.|It is concluded that cockroach temperature regulation is more precise than expected and that central temperature receptors are the primary sensing elements for cockroach thermoregulation.

Phenotypic plasticity in thermal tolerance in the Glanville fritillary butterfly

Ambient temperature is an ubiquitous environmental factor affecting all organisms. Global climate change increases temperature variation and the frequency of extreme temperatures, which may pose challenges to ectotherms. Here, we examine phenotypic plasticity to temperature and genotypic effects on thermal tolerance in the Glanville fritillary butterfly (Melitaea cinxia). We found no significant difference in heat or cold tolerance in populations originating from a continental climate in China and from Finland with moderate temperature variation. Acclimation to large-amplitude temperature variation increased heat tolerance in both populations, but decreased cold tolerance and increased hsp70-2 expression in the Chinese population only. The latter result indicates a genotypic effect in the response to temperature variation. In the Finnish population, a non-synonymous SNP in the phosphoglucose isomerase (Pgi) gene was associated with heat knock-down time.     

Thermal avoidance and preference in Daphnia magna

1. Water fleas (Daphnia magna) bred at 23°C were non-responsive to temperatures between 13 and 25°C.

2. At the lower (11°C) and upper limits (30°C) their klinokinetic avoidance behaviour showed a larger intraindividual than interindividual variation.

3. Thermal sensitivity for avoidance responses in D. magna was about 1.5°C.

4. For D. magna bred for one parthenogenetic generation at 14°C heat avoidance temperature was about 8°C lower, and cold avoidance temperature was about 1°C higher than in D. magna from 23°C.

5. In group experiments the animals showed some preference for the acclimation temperature.

6. Cold induced stenothermy and warm induced eurythermy in D. magna were related to the mode of reproduction.

大气CO2浓度和气温升高对麦田节肢动物群落的影响

为了预测气候变化对麦田节肢动物群落多样性的影响, 本研究在麦田开放环境中设置4种处理, 分别是高温(高于当时气温2℃和当前CO₂浓度)、高CO₂浓度(500 μL/L和当时气温)、高温+高CO₂浓度和对照(当前CO₂浓度和气温)等, 采用定期随机抽样方法调查节肢动物群落的多样性, 用经典的多样性指数对整体节肢动物群落以及不同食性节肢动物群落多样性进行分析。共采到节肢动物3纲10目42科52种。仅“高温”和“高温+高CO₂”处理显著增大节肢动物群落的均匀度, 其余处理均无显著影响。“高温+高CO₂”处理的影响随小麦生长发育期不同而略有差异, 在苗期可增大Shannon-Wiener多样性指数, 而在后期使该指数减小; “高温+高CO₂”与“高温”处理的群落多样性较为相似。对不同食性节肢动物群落的分析表明, 与对照相比, 植食性昆虫群落在“高CO₂”下丰富度显著增大; 寄生性昆虫群落的多度在“高温”下显著增大; 腐食性等节肢动物群落的多度在“高CO₂+高温”和“高温”处理下有所增大、均匀度在“高温”下略降低, 但均未达统计上的显著水平; 捕食性节肢动物群落不受影响。本研究说明, CO₂浓度和气温升高不同程度地影响麦田节肢动物群落的物种多样性, 两类因素同时升高与各自单独升高的影响不完全一致。     

Acclimation of isoprene emission and photosynthesis to growth temperature in hybrid aspen: resolving structural and physiological controls

Acclimation of foliage to growth temperature involves both structural and physiological modifications, but the relative importance of these two mechanisms of acclimation is poorly known, especially for isoprene emission responses. We grew hybrid aspen (Populus tremula x P. tremuloides) under control (day/night temperature of 25/20 °C) and high temperature conditions (35/27 °C) to gain insight into the structural and physiological acclimation controls. Growth at high temperature resulted in larger and thinner leaves with smaller and more densely packed chloroplasts and with lower leaf dry mass per area (M_A). High growth temperature also led to lower photosynthetic and respiration rates, isoprene emission rate and leaf pigment content and isoprene substrate dimethylallyl diphosphate pool size per unit area, but to greater stomatal conductance. However, all physiological characteristics were similar when expressed per unit dry mass, indicating that the area‐based differences were primarily driven by M_A. Acclimation to high temperature further increased heat stability of photosynthesis and increased activation energies for isoprene emission and isoprene synthase rate constant. This study demonstrates that temperature acclimation of photosynthetic and isoprene emission characteristics per unit leaf area were primarily driven by structural modifications, and we argue that future studies investigating acclimation to growth temperature must consider structural modifications.     

Effect of temperature and thermal acclimation on locomotor performance of Macrobiotus harmsworthi Murray (Tardigrada, Macrobiotidae)

We investigated the effects of acute and acclimation temperature on the locomotor performance and behavior of the tardigrade Macrobiotus harmsworthi collected from Qinling Mountains in central China. Tardigrades were acclimated to either 10 or 25 °C for 2 weeks. Then we recorded their walking speed, percentage of time moving, and the maximum distance covered by continuous locomotion at either 10 or 25 °C as the rate parameters of locomotor performance. The walking speeds of M. harmsworthi varied from 1.98 to 4.8 mm min^–1. The locomotor performance rates were significantly influenced by both acclimation temperature and performance temperature and by the interaction of the performance temperature and acclimation temperature. The data from our studies support the Beneficial Acclimation Hypothesis (BAH) which predicts that animals acclimated to a particular temperature have enhanced performance or fitness at that temperature in comparison with animals acclimated to other temperatures. The data, at least potentially, also support the Warmer is Better Hypothesis which predicts that organisms raised at high temperatures have higher relative fitness across all temperatures than do those raised at intermediate or cool temperatures. Some of the results from our studies testify the inference from the BAH that performance temperature that deviates from the acclimation temperature could cause the reduction of the locomotor performance rate.     

The effect of temperature and acclimation period on repeat swimming performance in cutthroat trout

Hatchery cutthroat trout Oncorhynchus clarki clarki were used to examine the effects of 48 h and 3 week temperature acclimation periods on critical swimming speed ( U _crit). The U _crit was determined for fish at acclimation temperatures of 7, 14 and 18° C using two consecutive ramp‐ U _crit tests in mobile Brett‐type swim tunnels. An additional group was tested at the stock's ambient rearing temperature of 10° C. The length of the temperature acclimation period had no significant effect on either the first or the second U _crit( U _crit‐1 and U _crit‐2, respectively) or on the recovery ratio (the quotient of U _crit‐2  U _crit‐1⁻¹). As anticipated, there was a significant positive relationship between U _crit‐1 and temperature ( P  < 0·01) for both acclimation periods, and an increasing, though non‐significant, trend between U _crit‐2 and temperature ( P  = 0·10). Acclimation temperature had no significant effect ( P  = 0·71) on the recovery ratio. These results indicate that a 48 h acclimation to experimental temperatures within the range of −3 to +8° C of the acclimation temperature may be sufficient in studies of swimming performance with this species. This ability to acclimate rapidly is probably adaptive for cutthroat trout and other species that occupy thermally variable environments.     

Higher daytime leaf temperatures contribute to lower freeze tolerance under elevated CO2

Elevated atmospheric CO2 adversely affects freezing tolerance in many evergreens, but the underlying mechanism(s) have been elusive. We compared effects of elevated CO2 with those of daytime warming on acclimation of snow gum (Eucalyptus pauciflora) to freezing temperatures under field conditions. Reduction in stomatal conductance g(c) under elevated CO2 was shown to cause leaf temperature to increase by up to 3 degrees C. In this study, this increase in leaf temperature was simulated under ambient CO2 conditions by using a free air temperature increase (FATI) system to warm snow gum leaves during daytime, thereby increasing the diurnal range in temperature without affecting temperature minima. Acclimation to freezing temperatures was assessed using measures of electrolyte leakage and photosynthetic efficiency of leaf discs exposed to different nadir temperatures. Here, we show that both elevated CO2 and daytime warming delayed acclimation to freezing temperatures for 2-3 weeks after which time freeze tolerance of the treated plants in both the FATI and open top chamber (OTC) experiments did not differ from control plants. Our results support the hypothesis that delayed development of freezing tolerance under elevated CO2 is because of higher daytime leaf temperatures under elevated CO2. Thus, potential gains in productivity in response to increasing atmospheric CO2 and prolonging the growing season may be reduced by an increase in freezing stress in frost-prone area.     

Phenotypic plasticity of thermal tolerances in five oribatid mite species from sub-Antarctic Marion Island

The extent to which phenotypic plasticity might mediate short-term responses to environmental change is controversial. Nonetheless, theoretical work has made the prediction that plasticity should be common, especially in predictably variable environments by comparison with those that are either stable or unpredictable. Here we examine these predictions by comparing the phenotypic plasticity of thermal tolerances (supercooling point (SCP), lower lethal temperature (LLT), upper lethal temperature (ULT)), following acclimation at either 0, 5, 10 or 15 degrees C, for seven days, of five, closely-related ameronothroid mite species. These species occupy marine and terrestrial habitats, which differ in their predictability, on sub-Antarctic Marion Island. All of the species showed some evidence of pre-freeze mortality (SCPs -9 to -23 degrees C; LLTs -3 to -15 degrees C), though methodological effects might have contributed to the difference between the SCPs and LLTs, and the species are therefore considered moderately chill tolerant. ULTs varied between 36 degrees C and 41 degrees C. Acclimation effects on SCP and LLT were typically stronger in the marine than in the terrestrial species, in keeping with the prediction of strong acclimation responses in species from predictably variable environments, but weaker responses in species from unpredictable environments. The converse was found for ULT. These findings demonstrate that acclimation responses vary among traits in the same species. Moreover, they suggest that there is merit in assessing the predictability of changes in high and low environmental temperatures separately.     

Effect of environmental temperature on biosynthesis of liver phosphatidyl-choline in the trout (Salmo gairdnerii)

1. 1.The changes in fatty acid composition of trout liver phosphatidyl-choline, when the environmental temperature was increased, resulted in modifications in the amounts of the different molecular species.

2. 2.In vivo, incorporation of ³²P occurred more rapidly in the molecular species with high degree of unsaturation.Temperature acclimation did not modify the relative proportions of label shown in the five subfractions.

3. 3.In vitro incorporation of ¹⁴C-methyl-choline also occurred more rapidly in the most unsaturated molecular species. However, when the incubation temperature was raised, the proportion of label decreased in the unsaturated fractions.

Thermal response of juvenile Hawaiian mullet Mugil cephalus (L.) to acclimation time and fluctuating low temperatures*

Rates of acclimation and the response to fluctuating low temperatures of juvenile striped mullet Mugil cephalus (L.) have been described in terms of changes in heat resistance over a period of time. Fish changed from 25.5 to 27 or 29° C were acclimated within seven days. Acclimation to 23 or 15° C required a maximum of 11 days. Thermal responses to fluctuating low temperatures were lower than responses to constant temperature levels. Cyclic variations in heat resistance were present in all experimental and control tests.