Sensible heat transfer and thermal windows in Dasyprocta leporina (Mammalia,Rodentia)

This study aimed to evaluate the diurnal variation of the sensible heat transfer in red-rumped agoutis (Dasyprocta leporina) bred in captivity in a semi-arid environment. In addition, we seek to identify thermal windows by infrared thermography during the daytime period (07:00, 09:00, 11:00, 14:00, and 16:00). The body surface temperature was higher in the pinna (36.84 ± 0.11 °C), followed by the hind limbs (36.55 ± 0.11 °C). These body regions were primarily responsible for heat loss by radiation (which was 10.13 ± 1.17 W m^?2 and 11.19 ± 1.17 W m^?2, respectively), and acted like biological thermal windows. Heat transfer by convection was more intense in the body trunk and hind limbs at all times of the day. Thus, sensible heat transfer is important for maintaining homeothermy in red-rumped agouti in hot environments. In conclusion, these rodents use specialized body regions (pinna and hind limbs) for heat transfer.     

Thermal orientation of Anthonomus pomorum (Coleoptera: Curculionidae) in early spring

Abstract. The selection of habitats with favourable temperature by the apple blossom weevil Anthonomus pomorum (L.) is investigated in a temperature gradient arena with a range of approximately 0–15 °C. Single female and male weevils are tested in the arena 2, 4 and 6 days after termination of diapause, during photophase and during scotophase. During photophase, weevils of both sexes choose the warmest part of the temperature gradient arena, irrespective of the time elapsed after diapause. During scotophase, high temperature is favoured by male weevils, as well as by females 2 and 4 days after diapause. However, 6 days after termination of diapause, females show no thermal preference in the temperature gradient arena during scotophase, indicating that thermal choice of female A. pomorum in the scotophase changes with time after the termination of diapause. The results suggest that both sexes benefit from thermoregulation by habitat choice during photophase when the weevils are flight active and colonize apple trees.     

Maize leaf temperature responses to drought: Thermal imaging and quantitative trait loci (QTL) mapping

Leaf temperature has been shown to vary when plants are subjected to water stress conditions. Recent advances in infrared thermography have increased the probability of recording drought tolerant responses more accurately. The aims of this study were to identify the effects of drought on leaf temperature using infrared thermography. Furthermore, the genomic regions responsible for the expression of leaf temperature variation in maize seedlings (Zea mays L.) were explored. The maize inbred lines Zong3 and 87-1 were evaluated using infrared thermography and exhibited notable differences in leaf temperature response to water stress. Correlation analysis indicated that leaf temperature response to water stress played an integral role in maize biomass accumulation. Additionally, a mapping population of 187 recombinant inbred lines (RILs) derived from a cross between Zong3 and 87-1 was constructed to identify quantitative trait loci (QTL) responsible for physiological traits associated with seedling water stress. Leaf temperature differences (LTD) and the drought tolerance index (DTI) of shoot fresh weight (SFW) and shoot dry weight (SDW) were the traits evaluated for QTL analysis in maize seedlings. A total of nine QTL were detected by composite interval mapping (CIM) for the three traits (LTD, RSFW and RSDW). Two co-locations responsible for both RSFW and RSDW were detected on chromosomes 1 and 2, respectively, which showed common signs with their trait correlations. Another co-location was detected on chromosome 9 between LTD and shoot biomass, which provided genetic evidence that leaf temperature affects biomass accumulation. Additionally, the utility of a thermography system for drought tolerance breeding in maize was discussed.     

Mitigating thermal effect of behaviour and microhabitat on the intertidal snail Littorina saxatilis (Olivi) over summer

High shore intertidal ectotherms must withstand temperatures which are already close, at or beyond their upper physiological thermal tolerance. Their behaviour can provide a relief under heat stress, and increase their survival through thermoregulation. Here, we used infrared imaging to reveal the thermoregulatory behavioural strategies used by the snail Littorina saxatilis (Olivi) on different microhabitats of a high shore boulder field in Finistère (western France) in summer. On our study site, substrate temperature is frequently greater than L. saxatilis upper physiological thermal limits, especially on sun exposed microhabitats. To maintain body temperatures within their thermal tolerance window, withdrawn snails adopted a flat posture, or elevated their shells and kept appended to the rock on the outer lip of their aperture with dried mucous (standing posture). These thermal regulatory behaviours lowered snail body temperatures on average by 1–2 °C. Aggregation behaviour had no thermoregulatory effect on L. saxatilis in the present study. The occupation of biogenic microhabitats (barnacles) was associated with a 1 °C decrease in body temperatures. Barnacles and microhabitats that experienced low sun exposure, low thermal fluctuations and low thermal maxima, could buffer the heat extremes encountered at high shore level especially on sun exposed microhabitats.     

Basking behavior predicts the evolution of heat tolerance in Australian rainforest lizards

There is pressing urgency to understand how tropical ectotherms can behaviorally and physiologically respond to climate warming. We examine how basking behavior and thermal environment interact to influence evolutionary variation in thermal physiology of multiple species of lygosomine rainforest skinks from the Wet Tropics of northeastern Queensland, Australia (AWT). These tropical lizards are behaviorally specialized to exploit canopy or sun, and are distributed across marked thermal clines in the AWT. Using phylogenetic analyses, we demonstrate that physiological parameters are either associated with changes in local thermal habitat or to basking behavior, but not both. Cold tolerance, the optimal sprint speed, and performance breadth are primarily influenced by local thermal environment. Specifically, montane lizards are more cool tolerant, have broader performance breadths, and higher optimum sprinting temperatures than their lowland counterparts. Heat tolerance, in contrast, is strongly affected by basking behavior: there are two evolutionary optima, with basking species having considerably higher heat tolerance than shade skinks, with no effect of elevation. These distinct responses among traits indicate the multiple selective pressures and constraints that shape the evolution of thermal performance. We discuss how behavior and physiology interact to shape organisms’ vulnerability and potential resilience to climate change.     

荒漠昆虫光滑鳖甲的耐寒性季节变化及其生理机制

光滑鳖甲Anatolica polita borealis生活于温差大的新疆荒漠环境, 为探讨其耐寒性及耐寒机制, 本研究测定了其3-9月份成虫在－10℃的耐寒性、过冷却点（SCP）、含水量、甘油含量和血淋巴热滞活性(thermal hysteresis activity, THA)以及冷驯化对增强光滑鳖甲成虫耐寒性的效果, 还测定了光滑鳖甲不同发育阶段幼虫的SCP。结果表明: 光滑鳖甲成虫的耐寒性和SCP具有明显的季节性变化, 3月初SCP为－12.5℃, 7月为－6℃, 9月底为－13.6℃。4℃冷驯化能够提高光滑鳖甲成虫在－10℃的存活率, 未驯化组在40 min的存活率为50%, 而驯化2 h的为70%, 驯化24 h的为90%。虫体含水量在夏季有显著降低, 3月、7月和9月结合水与自由水的比值分别为10.8∶1,2.6∶1和5.4∶1。成虫甘油含量与SCP的回归方程为y=－0.6204x－5.681, R²=0.7714。成虫血淋巴THA与过冷却点的回归方程为y=－5.26x－1.713, R²=0.9049。血淋巴THA比甘油浓度更能影响过冷却点降低的程度。随着幼虫的发育, 其SCP逐渐降低。结果提示, 光滑鳖甲通过提高结合水与自由水的比值、增加抗冻蛋白和甘油的含量使虫体保持较低的SCP, 因而具有较高的耐寒性。     

Evolutionary potential of thermal preference and heat tolerance in Drosophila subobscura

Evolutionary change of thermal traits (i.e., heat tolerance and behavioural thermoregulation) is one of the most important mechanisms exhibited by organisms to respond to global warming. However, the evolutionary potential of heat tolerance, estimated as narrow‐sense heritability, depends on the methodology employed. An alternative adaptive mechanism to buffer extreme temperatures is behavioural thermoregulation, although the association between heat tolerance and thermal preference is not clearly understood. We suspect that methodological effects associated with the duration of heat stress during thermal tolerance assays are responsible for missing this genetic association. To test this hypothesis, we estimated the heritabilities and genetic correlations for thermal traits in Drosophila subobscura, using high‐temperature static and slow ramping assays. We found that heritability for heat tolerance was higher in static assays (h² = 0.134) than in slow ramping assays (h² = 0.084), suggesting that fast assays may provide a more precise estimation of the genetic variation of heat tolerance. In addition, thermal preference exhibited a low heritability (h² = 0.066), suggesting a reduced evolutionary response for this trait. We also found that the different estimates of heat tolerance and thermal preference were not genetically correlated, regardless of how heat tolerance was estimated. In conclusion, our data suggest that these thermal traits can evolve independently in this species. In agreement with previous evidence, these results indicate that methodology may have an important impact on genetic estimates of heat tolerance and that fast assays are more likely to detect the genetic component of heat tolerance.     

Thermal body patterns for healthy Brazilian adults (male and female)

The aim of this study was to establish the skin temperature (T_sk) thermal profile for the Brazilian population and to compare the differences between female and male Brazilian adults. A total of 117 female and 103 male were examined with a thermographic camera. The T_sk of 24 body regions of interest (ROI) were recorded and analyzed. Male T_sk results were compared to female and 10 ROI were evaluated with respect to the opposite side of the body (right vs. left) to identify the existence of significant contralateral T_sk differences (ΔT_sk). When compared right to left, the largest contralateral ΔT_sk was 0.3 °C. The female vs. male analysis yielded significant differences (p<0.05) in 13 of the 24 ROI. Thigh regions, both ventral and dorsal, had the highest ΔT_sk by sex (≈1.0 °C). T_sk percentile below P₅ or P₁₀ and over P₉₀ or P₉₅ may be used to characterize hypothermia and hyperthermia states, respectively. Thermal patterns and T_sk tables were established for Brazilian adult men and women for each ROI. There is a low T_sk variation between sides of the body and gender differences were only significant for some ROIs.     

Thermal tolerance and geographical range size in the Agabus brunneus group of European diving beetles (Coleoptera: Dytiscidae)

Aim Within clades, most taxa are rare, whilst few are common, a general pattern for which the causes remain poorly understood. Here we investigate the relationship between thermal performance (tolerance and acclimation ability) and the size of a species’ geographical range for an assemblage of four ecologically similar European diving beetles (the Agabus brunneus group) to examine whether thermal physiology relates to latitudinal range extent, and whether Brown’s hypothesis and the environmental variability hypothesis apply to these taxa. Location Europe. Methods In order to determine the species tolerances to either low or high temperatures we measured the lethal thermal limits of adults, previously acclimated at one of two temperatures, by means of thermal ramping experiments (± 1°C min^?1). These measures of upper and lower thermal tolerances (UTT and LTT respectively) were then used to estimate each species’ thermal tolerance range, as total thermal tolerance polygons and marginal UTT and LTT thermal polygons. Results Overall, widespread species have higher UTTs and lower LTTs than restricted ones. Mean upper lethal limits of the Agabus brunneus group (43 to 46°C), are similar to those of insects living at similar latitudes, whilst mean lower lethal limits (?6 to ?9°C) are relatively high, suggesting that this group is not particularly cold‐hardy compared with other mid‐temperate‐latitude insects. Widespread species possess the largest thermal tolerance ranges and have a relatively symmetrical tolerance to both high and low temperatures, when compared with range‐restricted relatives. Over the temperature range employed, adults did not acclimate to either high or low temperatures, contrasting with many insect groups, and suggesting that physiological plasticity has a limited role in shaping distribution. Main conclusions Absolute thermal niche appears to be a good predictor of latitudinal range, supporting both Brown’s hypothesis and the environmental variability hypothesis. Restricted‐range species may be more susceptible to the direct effect of climate change than widespread species, notwithstanding the possibility that even ‘thermally‐hardy’, widespread species may be influenced by the indirect effects of climate change such as reduction in habitat availability in Mediterranean areas.     

Heat tolerance may determine activity time in coprophagic beetle species (Coleoptera: Scarabaeidae)

Although reports have documented loss of species diversity and ecological services caused by stressful temperature changes that result from climate change, some species cope through behavioral compensation. As temperatures and magnitudes of temperature extremes increase, animals should compensate to maintain fitness (such as through temporary behavioral shifts in activity times). Appropriate timing of activity helps avoid competition across species. Although coprophagic dung beetles exhibit species-specific temporal activity times, it is unknown whether temperature drives evolution of these species-specific temporal activity times. Using nine dung beetle species (three each of diurnal, crepuscular, and nocturnal species), we explored differences in heat stress tolerance measured as critical thermal maxima (CT_max; the highest temperature allowing activity) and heat knockdown time (HKDT; survival time under acute heat stress) across these species, and examined the results using a phylogenetically informed approach. Our results showed that day-active species had significantly higher CT_max (diurnal > crepuscular = nocturnal species), whereas crepuscular species had higher HKDT (crepuscular > nocturnal > diurnal species). There was no correlation between heat tolerance and body size across species with distinct temporal activity, and no significant phylogenetic constraint for activity. Species with higher CT_max did not necessarily have higher HKDT, which indicates that species may respond differently to diverse heat tolerance metrics. Acute heat tolerance for diurnal beetles indicates that this trait may constrain activity time and, under high acute temperatures with climate change, species may shift activity times in more benign environments. These results contribute to elucidate the evolution of foraging behavior and management of coprophagic beetle ecosystem services under changing environments.     

Thermal biology of bonefish (Albula vulpes) in Bahamian coastal waters and tidal creeks: An integrated laboratory and field study

Little is known about the thermal tolerances of fish that occupy tropical intertidal habitats or how their distribution, physiological condition, and survival are influenced by water temperature. We used a combination of laboratory and field approaches to study the thermal biology of bonefish, Albula vulpes, a fish species that relies on nearshore intertidal habitats throughout the Caribbean. The critical thermal maximum (CTMax) for bonefish was determined to be 36.4±0.5 and 37.9±0.5 °C for fish acclimated to 27.3±1.3 and 30.2±1.4 °C, respectively, and these tolerances are below maximal temperatures recorded in the tropical tidal habitats where bonefish frequently reside (i.e., up to 40.6 °C). In addition, daily temperatures can fluctuate up to 11.4 °C over a 24-h period emphasizing the dramatic range of temperatures that could be experienced by bonefish on a diel basis. Use of an acoustic telemetry array to monitor bonefish movements coupled with hourly temperature data collected within tidal creeks revealed a significant positive relationship between the amount of time bonefish spent in the upper portions of the creeks with the increasing maximal water temperature. This behavior is likely in response to feeding requirements necessary to fuel elevated metabolic demands when water temperatures generally warm, and also to avoid predators. For fish held in the laboratory, reaching CTMax temperatures elicited a secondary stress response that included an increase in blood lactate, glucose, and potassium levels. A field study that involved exposing fish to a standardized handling stressor at temperatures approaching their CTMax generated severe physiological disturbances relative to fish exposed to the same stressor at cooler temperatures. In addition, evaluation of the short-term survival of bonefish after surgical implantation of telemetry tags revealed that there was a positive relationship between water temperature at time of tagging and mortality. Collectively, the data from these laboratory and field studies suggest that bonefish occupy habitats that approach their laboratory-determined CTMax and can apparently do so without significant sub-lethal physiological consequences or mortality, except when exposed to additional stressors.     

The physical mechanism of cuticular color in Phelotrupes auratus (Coleoptera,Geotrupidae)

The physical mechanism of cuticular color in Phelotrupes auratus was investigated by polarized inspection, spectrophotometry and transmission electron microscopy (TEM). No color change was observed when viewed through either a right‐ or left‐handed circular polarizer. Further, under the incidence of linearly polarized light, the reflected intensity was markedly reduced when observed through a linear polarizer set with its optical axis perpendicular to that of the incident light. These results indicate that P. auratus does not possess any circularly polarizing reflectors. TEM observations revealed a total of ten or twelve thin layers (about 60–120 nm in thickness) of two types of material (electron‐dense and electron‐lucent) alternately stacked in the epicuticle. The thickness of the layers in the different color forms of the beetle corresponded to the peak wavelengths in the reflectance spectra, λmax(α), with thicker layers found in beetles exhibiting reflectance peaks at longer wavelengths and vice versa. Based on these findings, we concluded that all the cuticular color forms of P. auratus were not produced by a circularly polarizing reflector but by a simple multilayer reflector.     

Partitioning variance in a physiological trait: desiccation resistance in keratin beetles (Coleoptera, Trogidae)

1. Although variation in physiological traits forms the substance of evolutionary physiology, the way that this variation is partitioned among different hierarchical levels (e.g. population, species, genus) is not well known.
2. In this study variance partitioning is examined in body size, water content, lipid content, rate of water loss, maximum tolerable water loss and survival time at four levels (individual, population, species, genus) in southern African keratin beetles.
3. It is found that most variance in body size, and the physiological traits that are strongly influenced by body size (water and lipid content, maximum tolerable water loss, rate of water loss), is partitioned at the generic level (50–70%), then at the species level (20–50%) and finally at the population (1–9%) and individual (2–18%) levels.
4. On the other hand, variance in survival time, and variance in rate of maximum water loss once the effects of body size have been taken into account, are partitioned mostly at the species level (40–70%), whereas maximum tolerable water loss and lipid and water content show greatest variance at the individual level (63–75%). This is largely a consequence of differences in the extent of scaling of these traits.
5. The results suggest that where possible the effects of phylogeny should be controlled for when examining desiccation resistance in insects using comparative methods, but that confidence in conclusions from previous studies, which have used mass-specific data, is not unwarranted.     

Thermal behaviour of crustaceans

Specific thermoreceptors or putative multimodal thermoreceptors are not known in Crustacea. However, behavioural studies on thermal avoidance and preference and on the effects of temperature on motor activity indicate that the thermosensitivity of crustaceans may be in the range 0.2-2 degrees C. Work on planktonic crustaceans suggests that they respond particularly to changes in temperature by klinokinesis and orthokinesis. The thermal behaviour of crustaceans is modified by thermal acclimation among other factors. The acclimation of the critical maximum temperature is an example of resistance acclimation, while the acclimation of preference behaviour may be classified as capacity acclimation of some other function. In crustaceans, the use of the concepts stenothermy and eurythermy at the species level is questionable, and it is not possible to divide crustacean species into thermal guilds as suggested for fishes. Thermal preference behaviour contributes to fitness in different ways in different species, often by maximising the aerobic metabolic scope for activity. In crustaceans the peripheral nervous system seems to have retained the capacity for thermosensitivity and thermal acclimation independently of the central nervous system control of behaviour.     

小菜蛾的耐热性

小菜蛾是世界范围内十字花科蔬菜上的重要害虫.临界高温(critical thermal maxi-mum,CTMax)是昆虫耐热性的常用指标.采用动态加热方法,利用自行组装的装置测定了小菜蛾的临界高温,以此作为其耐热性指标,研究发育阶段、饲养温度、世代、性别和热激对小菜蛾耐热性的影响.结果表明:25℃下饲养的小菜蛾4龄幼虫的CTMax均值为50.31℃,显著高于1龄幼虫(43.03℃)、2龄幼虫(46.39℃)、3龄幼虫(49.67℃)以及雌性成虫(45.76℃)和雄性成虫(47.73℃);不同饲养温度(20、25和30℃)下成虫耐热性无显著差异;30℃下饲养1代、3代及6代的不同世代成虫CTMax也无显著变化;所有处理雌雄成虫的CTMax无显著差异;40℃下45 min热激可使5日龄雄成虫的CTMax值从45.51℃增加到46.49℃.     

Morphology of the prothoracic discs and associated sensilla of Acanthocnemus nigricans (Coleoptera, Acanthocnemidae)

The Australian ‘little ash beetle’ Acanthocnemus nigricans (Coleoptera, Cleroidea, Acanthocnemidae) is attracted by forest fires. A. nigricans has one pair of unique prothoracic sensory organs and it has been speculated that these organs may play a role in fire detection. Each organ consists of a cuticular disc, which is fixed over an air-filled cavity. On the outer surface of the disc, about 90 tiny cuticular sensilla are situated. The poreless outer peg of a sensillum is 3–5 μm long and is surrounded by a cuticular wall. One ciliary sensory cell innervates the peg. As a special feature, the outer dendritic segment is very short already terminating below the cuticle. A massive electron-dense cylindrical rod, which most probably represents the hypertrophied dendritic sheath, extends through the cuticular canal connecting the tip of the outer dendritic segment to the peg. The dendritic inner segment and the soma are fused indistinguishably. Thin, leaflike extensions of glial cells deeply extend into that conjoint and considerably enlarged compartment which also contains large numbers of mitochondria. In summary, the sensilla of the sensory disc of A. nigricans represent a new type of insect sensillum of hitherto unknown function. The possible role of the prothoracic sensory organ in fire detection is discussed.     

Thermal tolerance, acclimatory capacity and vulnerability to global climate change

Despite evidence that organismal distributions are shifting in response to recent climatic warming, we have little information on direct links between species' physiology and vulnerability to climate change. We demonstrate a positive relationship between upper thermal tolerance and its acclimatory ability in a well-defined clade of closely related European diving beetles. We predict that species with the lowest tolerance to high temperatures will be most at risk from the adverse effects of future warming, since they have both low absolute thermal tolerance and poor acclimatory ability. Upper thermal tolerance is also positively related to species' geographical range size, meaning that species most at risk are already the most geographically restricted ones, being endemic to Mediterranean mountain systems. Our findings on the relationship between tolerance and acclimatory ability contrast with results from marine animals, suggesting that generalizations regarding thermal tolerance and responses to future rapid climate change may be premature.     

Delineation of temperature-humidity index (THI) as indicator of heat stress in riverine buffaloes (Bubalus bubalis) of a sub-tropical Indian region

The erstwhile developed temperature-humidity index (THI) has been popularly used to indicate heat stress in dairy cattle and often in buffaloes. However, scientific literature suggests differences in thermotolerance and physiological responses to heat stress between cattle and buffalo. Therefore, THI range used to indicate degree of heat stress (mild, moderate, and severe) in cattle should be recalibrated for indicating heat stress in buffaloes. The present study was carried out to delineate THI range to indicate onset and severity of heat stress in buffaloes based on physiological, biochemical, and expression profiling of heat shock response (HSR) genes in animals at different THI. The result indicated early onset of heat stress in buffaloes as compared to cattle. Physiological and biochemical parameters indicated onset of mild signs of heat stress in buffaloes at THI 68-69. Significant deviation in these parameters was again observed at THI range 73-76. At THI 77-80, the physiological and biochemical responses of animals were further intensified indicating extreme alteration in homeostasis. The in vivo expression profiling of HSR genes indicated that members of Hsp70 gene family are expressed in a temporal pattern over different THIs, whereas expressions of Hsf genes were evident during intense heat stress. Overall, the study established that amplitude of heat shock response and THI range for indicating severity of thermal stress for buffaloes are not in unison to cattle. The study also suggests skin temperature of the poll region could be used as non-invasive tool for monitoring heat stress in dairy buffaloes.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12192-021-01209-1.