Acclimation to temperature and death at changing lethal temperatures in the freshwater fish Chalcalburnues chalcoides

1. 1.|In the freshwater fish Chalcalburnus chalcoides, an increase in the body (standard) size caused decreases in the upper LT-50 from 36.6° to 36.0°C and lower LT-50 from 6.3° to 5.3°C

2. 2.|The fish acclimated to constant temperatures between 10°C and 30°C showed reasonable heat acclimation and also reasonable cold acclimation. Thus, an increase in the acclimation temperature from 10°C to 30°C caused increases in the upper LT-50 from 34° to 36.2°C and the lower LT-50 from 1.25 to 6.5°C.

3. 3|The mean survival time — temperature curves of 10°, 20° and 30°C acclimated fish at various constant temperatures showed decreased in the survival tim ewith increasing lethal temperatures. Furthermore, an increase in the acclimation temperature causes a shift in the survival duration-temperature curve to the right, i.e., the fish become more heat resistant. Thus, the mean survival duration of 10°, 20° and 30°C acclimated fish at 35°C were 7.5, 79.6 and 530 minutes, respectively.

4. 4.|The effect of the thermal experience to changing lethal temperatures depends on the first lethal temperature to which the fish were exposed as well as the sequence of temperature changes. In the experiments in which the first lethal temperatures were between 32° and 34°C and the temperature was varied in an ascending order, their thermal resistance was increased and the fish required 114 to 174% of the expected lethal doses to die while in the experiments in which the starting temperature were between 38° and 40°C and the temperature varied in descending order, the fish become more sensitive to the upper lethal temperature and they died after receiving only 62 to 81% of the expected lethal doses. Thus, with a gradual increase in the lethal temperature, the fish show additional acclimation in the zone of resistance which in turn causes an increase in the thermal resistance. This may have ecological significance in nature.

Effect of high temperatures and artificial sunlight on the viability of conidia of Metarhizium anisopliae

Studies on the heat resistance of the conidia of Metarhizium anisopliae showed a clear correlation to the actual moisture conditions. The medium lethal temperature for 30 min of exposure in a suspension was 42°C, but 50.5°C at 100% RH, 57.5°C at 76% RH, and 68.8°C at 33% RH. The experiments on the effect of artificial sunlight indicated an extrapolated half-life of the conidia under field conditions of 1 hr, 40 min for 24 hr incubation at 25°C in the dark following exposure and about 2 hr, 45 min for 48 hr incubation.     

The relation of changes in the individual levels of heat resistance of muscle tissue to their initial values during heat acclimation of Asellus aquaticus

1. 1.|In hog slater, Asellus aquaticus, five extremities were consecutively isolated in the course of heat acclimation to study the pattern of changes in the level of the heat resistance of muscle tissue of each single specimen.

2. 2.|The initial response of the population, during acclimation, is for the muscle resistance of different individuals to become less varied. Then a simultaneous increase in tissue resistance occurs in all ammals, which is complete by the 6th day of acclimation. Afterwards the heat resistance of muscles in the majority of animals shows little change and then, in spite of maintenance of acclimation, it starts to return to its initial level.

3. 3.|Thermal acclimation causes a temporary decrease in the variability of the heat resistance of the muscle tissue and also a temporary stabilization of this physiological characteristic to a new level. This phenomenon is a phenotypical masking of genotypic differences in a physiological characteristic in the population studied during changes in environmental temperature.

4. 4.|At all the stages of acclimation the relation of individual increases in cellular heat resistance to their initial levels follows a hyperbolic exponential equation. This implies that to a rise in environmental temperature a population responds as an integral functional system.

驯化温度与急性变温对南方鲇幼鱼皮肤呼吸代谢的影响

为了考查鱼类皮肤呼吸代谢的温度反应特征,在不同驯化温度(10、20、30℃)及双向急性变温(10→20℃、20→30℃、10→30℃;20→10 ℃、30→20℃、30→10℃)条件下采用自行设计的皮肤呼吸代谢装置测定麻醉后南方鲇(Silurus meridionalis)幼鱼的皮肤耗氧率(MO2skin)及鳃部耗氧率(MO2gill),并计算整体耗氧率(MO2total).研究显示:南方鲇幼鱼的MO2skin占MO2total 的16.4％-19.0％,随着驯化温度的升高,MO2skin上升的幅度显著低于MO2total(P＜0.05),MO2skin占MO2total的比例则呈下降趋势;急性升(降)温组的MO2skin与升(降)温前驯化温度组相比显著升高(降低)(P＜0.05),却与相应温度驯化组的MO2skin无显著性差异(P＞0.05);急性变温组MO2skin的Q10值与驯化温度组的差异不显著(P＞0.05),却显著低于MO2total的Q10值(P＜0.05).通过相关资料比较发现,南方鲇幼鱼MO2skin占MO2total的比例处于中上水平.研究表明,在驯化温度和急性变温条件下,实验鱼的MO2total分别存在代谢补偿反应和急性胁迫反应;MO2skin与MO2total的温度反应不同,它既不是一个完全的化学反应过程,也不是生物反应过程,而更倾向于是一个物理的扩散过程.     

The effect of constant and changing temperatures on the thermal resistance of Lymnaea peregra (Müller)

The effect of constant and changing temperatures on both high and low lethal temperatures of Lymnaea peregra and the time course of acclimation were investigated. Snails acclimated to 6.5°, 11.5° and 16.5°C showed paradoxical ‘adaptation’ of their high letal temperature and reasonable ‘adaptation’ of the lowlethal temperature. This combination is thus observed for the first time in molluscs. Seasonal variation in the upper lethal temperature showed parallel changes and the snails became less resistant to heat during spring and summer. Acclimation to changing temperature conditions did not extend their temperature tolerance range. During the course of acclimation of 6.5°C snails to 16.5°C, about 70% of the acclimation was completed within the first 24 h and the rest was completed within 360 h at 16.5°C.     

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.     

The effect of temperature and body size on digestive efficiency in Fundulus heteroclitus (L.)

The digestive efficiency of temperature acclimated mummichogs, Fundulus heteroclitus (L.), was determined using the amphipod Orchestia grillus Bosc as prey. Experiments were conducted on three size groups of mummichogs (<1 g, 1–3 g, > 3 g) at 5, 13, 21, and 29 °C. No difference was found in digestive efficiency by different sizes of mummichogs. There was, however, a statistically significant difference in efficiency over the range of acclimation temperatures, with the efficiencies being temperature independent from 13 to 29 °C and dropping slightly at 5 °C. From 13 to 29 °C, digestive efficiencies were the maximum possible. Temperatures in this range are normal late spring, summer, and early fall habitat temperatures in Maine estuaries. The ability to maintain a maximum efficiency of digestion over this 16°C temperature range allows mummichogs to get the maximum amount of energy from their prey during the time of year when they are utilizing substantial energy for growth (somatic and gonadal, and for activity (foraging and mating). The digestive efficiency at 5 °C was only about 13.5% less than at 21 and 29 °C. This drop is probably of little ecological or energetic significance, so that mummichogs are actually able to absorb food energy across their alimentary tract relatively independent of acclimation temperature over a 24 °C range.     

The effect of temperature on feeding,growth, and metabolism during the last larval stadium of the female house cricket, Acheta domesticus

Eighth instar female house crickets at 35°C developed faster, gained slightly more wet weight, and consumed less food, water, and oxygen than at 25°C. The duration of the 8th stadium at 25°C was 13 days (undisturbed), but was 14 days when disturbed by daily weighing. The duration of the 8th stadium at 30°C was 8 days and at 35°C was 6 days. During the first half of the 8th stadium at 25, 30, and 35°C, there was a high rate of food and water consumption resulting in statistically equal maximum dry weight achievement (124 mg). Respiratory quotients greater than one during this time indicated the conversion of ingested carbohydrate to fat. During the latter half of the 8th stadium, food and water consumption declined and the crickets lost weight. The period of weight loss was proportionally much longer at 25°C than at 30 or 35°C. Respiratory quotients lower than 1.0 during the latter half of the 8th stadium at 30 and 35°C indicated the metabolism of stored lipids. The respiratory quotient at 25°C never fell below 1.0, possibly because some food remained in the gut. The absorption efficiency was not influenced by temperature (25–35°C). Though the caloric content of the faeces was lower at 25°C than at 30 or 35°C, which correlated to the much longer time for food passage at 25°C than at 35°C, the difference in total calories egested was insufficient to alter the absorption efficiency. A longer period of reduced feeding and greater dry weight loss during the latter half of the 8th stadium at 25°C resulted in a lower metabolic efficiency at 25°C than at 30 or 35°C. Eighth instar crickets in response to a step-function transfer from 30°C–25 or 35°C showed an immediate (<1 hr) and complete metabolic adjustment which was not affected by the temperature history during the 7th stadium. House crickets did not exhibit temperature acclimation in the range 20–40°C, the metabolic rate being determined by ambient temperature. The Q₁₀ for oxygen consumption in the range 20–40°C was about 2.     

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.     

Resistance of photosynthesis to high temperature in two bean varieties (Phaseolus vulgaris L.)

The increase in the basal fluorescence (F₀) by increases in temperature has been widely used as a screening technique to assess the temperature at which plant species suffer irreversible damage in their photosynthetic apparatus. This method has been used in this study to assess the resistance to extreme high temperature in two bean varieties, Barbucho (Chilean, non commercially bred) and Blue lake (commercially available in the UK). The results suggested that the two varieties have a similar threshold for high temperature at 42–43 °C, however, at 40 °C, Barbucho maintains its photosynthetic functions for a longer period of time compared to Blue-Lake as observed by mean of simultaneous measurement of gas exchange and room temperature fluorescence. It seems likely that inhibition at 40 °C in Blue-Lake is related to the instability of Photosystem II.     

Effects of temperature and photoperiod on frost resistance of white clover (Trifolium repens) ecotypes

Effects of photoperiod and temperature on frost resistance of seedling populations and clones of white clover (Trifolium repens L.) originating from various latitudes (58°48'–69°54'N) and altitudes (up to 1100 m above sea level) were studied in a phytotron. Low-temperature-induced cold acclimation in all populations was significantly stimulated by short photoperiod and low temperature. The highest levels of frost resistance were found in the northernmost seedling populations and in clones from northern coastal locations.