Do female newts modify thermoregulatory behavior to manipulate egg size?

Reproductive females manipulate offspring phenotypes by modifying conditions during embryogenesis. In ectotherms, the environmental control over embryogenesis is often realized by changes in maternal thermoregulation during gravidity. To determine if reproduction influences thermoregulatory behavior in species where females lay eggs shortly after fertilization (strict oviparity), we compared preferred body temperatures (T_p) between reproductive (egg-laying) and non-reproductive female newts, Ichthyosaura alpestris. Next, we exposed reproductive females to temperatures mimicking T_p ranges of reproductive and non-reproductive individuals to find out whether the maternally modified thermal regime influences ovum and jelly coat volume, and early cleavage rates at the time of oviposition. In the thermal gradient, reproductive females maintained their body temperatures within a narrower range than non-reproductive individuals. The exposure of ovipositing females to temperatures preferred during their reproductive and non-reproductive period had a negligible influence on egg size and early cleavage rates. We conclude that the modification of maternal thermoregulatory behavior provides a limited opportunity to manipulate egg traits in newts.     

Adaptive accuracy of temperature oviposition preferences in newts

Oviposition-site choice has profound fitness consequences for both a mother and her offspring. The adaptive significance of oviposition behaviour for both generations depends on two rarely considered assumptions: (1) the fit of maternal oviposition preferences with local phenotypic optimum (adaptive accuracy) and (2) the predictability of future conditions for developing offspring based on conditions at the time of oviposition. We examined both assumptions using temperature oviposition preferences (T _p,o) previously measured under laboratory conditions in the alpine newt, Ichthyosaura (formerly Triturus) alpestris. Analyses of temperature time series in the newt natural environment revealed, in agreement with oviposition-site choice of female newts, that T _p,o were closer to phenotypic optima at the water surface than at the maximal depth (bottom). Temperature time series in both depths contained a high proportion of predictable variation, though bottom thermal conditions were more predictable than those at the water surface. We concluded that female newts have to trade the adaptive accuracy of T _p,o for the predictability of future thermal conditions at the time of oviposition.     

PHYLOGENETIC STUDIES OF COADAPTATION: PREFERRED TEMPERATURES VERSUS OPTIMAL PERFORMANCE TEMPERATURES OF LIZARDS

The view that behavior and physiological performance are tightly coadapted is a central principle of physiological ecology. Here, we test this principle using a comparative study of evolutionary patterns in thermal preferences and the thermal dependence of sprinting in some Australian skinks (Lygosominae). Thermal preferences (T_p) differ strikingly among genera (range 24° to 35°C), but critical thermal maxima (CTMax) (range 38° to 45°C) and optimal temperatures for sprinting (T_o, 32° to 35°C) vary less. Diurnal genera have relatively high T_p, T_o, and CTMax. In contrast, nocturnal genera have low T_p but have moderate to high T_o and CTMax. Both nonphylogenetic and phylogenetic (minimum-evolution) approaches suggest that coadaptation is tight only for genera with high T_p. Phylogenetic analyses suggest that low T_p and, thus, partial coadaptation are evolutionarily derived, indicating that low thermal preferences can evolve, even if this results in reduced performance. In one instance, thermal preferences and the thermal dependence of sprinting may have evolved in opposite directions, a phenomenon we call “antagonistic coadaptation.” We speculate on factors driving partial coadaptation and antagonistic coadaptation in these skinks.     

Miami heat: Urban heat islands influence the thermal suitability of habitats for ectotherms

The urban heat island effect, where urban areas exhibit higher temperatures than less‐developed suburban and natural habitats, occurs in cities across the globe and is well understood from a physical perspective and at broad spatial scales. However, very little is known about how thermal variation caused by urbanization influences the ability of organisms to live in cities. Ectotherms are sensitive to environmental changes that affect thermal conditions, and therefore, increased urban temperatures may pose significant challenges to thermoregulation and alter temperature‐dependent activity. To evaluate whether these changes to the thermal environment affect the persistence and dispersal of ectothermic species in urban areas, we studied two species of Anolis lizards (Anolis cristatellus and Anolis sagrei) introduced to Miami‐Dade County, FL, USA, where they occur in both urban and natural habitats. We calculated canopy openness and measured operative temperature (T_e), which estimates the distribution of body temperatures in a non‐thermoregulating population, in four urban and four natural sites. We also captured lizards throughout the day and recorded their internal body temperature (T_b). We found that urban areas had more open canopies and higher T_e compared to natural habitats. Laboratory trials showed that A. cristatellus preferred lower temperatures than A. sagrei. Urban sites currently occupied by each species appear to lower thermoregulatory costs for both species, but only A. sagreihad field T_b that were more often within their preferred temperature range in urban habitats compared to natural areas. Furthermore, based on available T_e within each species' preferred temperature range, urban sites with only A. sagrei appear less suitable for A. cristatellus, whereas natural sites with only A. cristatellus are less suitable for A. sagrei. These results highlight how the thermal properties of urban areas contribute to patterns of persistence and dispersal, particularly relevant for studying species invasions worldwide.     

Hot and not‐so‐hot females: reproductive state and thermal preferences of female Arizona Bark Scorpions (Centruroides sculpturatus)

For ectotherms, environmental temperatures influence numerous life history characteristics, and the body temperatures (T_b) selected by individuals can affect offspring fitness and parental survival. Reproductive trade‐offs may therefore ensue for gravid females, because temperatures conducive to embryonic development may compromise females' body condition. We tested whether reproduction influenced thermoregulation in female Arizona Bark Scorpions (Centruroides sculpturatus). We predicted that gravid females select higher T_b and thermoregulate more precisely than nonreproductive females. Gravid C. sculpturatus gain body mass throughout gestation, which exposes larger portions of their pleural membrane, possibly increasing their rates of transcuticular water loss in arid environments. Accordingly, we tested whether gravid C. sculpturatus lose water faster than nonreproductive females. We determined the preferred T_b of female scorpions in a thermal gradient and measured water loss rates using flow‐through respirometry. Gravid females preferred significantly higher T_b than nonreproductive females, suggesting that gravid C. sculpturatus alter their thermoregulatory behaviour to promote offspring fitness. However, all scorpions thermoregulated with equal precision, perhaps because arid conditions create selective pressure on all females to thermoregulate effectively. Gravid females lost water faster than nonreproductive animals, indicating that greater exposure of the pleural membrane during gestation enhances the desiccation risk of reproductive females. Our findings suggest that gravid C. sculpturatus experience a trade‐off, whereby selection of higher T_b and increased mass during gestation increase females' susceptibility to water loss, and thus their mortality risk. Elucidating the mechanisms that influence thermal preferences may reveal how reproductive trade‐offs shape the life history of ectotherms in arid environments.     

Evaluating thermal resource partitioning

Summary The field thermal biology of sympatric Anolis cooki and A. cristatellus were evaluated in January and in August in desert scrub forest at Playa de Tamarindo near Guanica, Puerto Rico. Data on randomly positioned copper models of lizards, each equipped with a built-in thermocouple, established null hypotheses about basking frequency and operative temperatures (T _e) against which the behavior and body temperatures (T _b) of live lizards were evaluated. Both species exhibited non-random hourly basking rates (more marked in cristatellus than in cooki), and cristatellus was virtually inactive during the warm mid-day hours. The relationship between lizards' T _b and randomly sampled T _e differed between the species: cristatellus's mean T _b was 2° to 3° C lower than randomly sampled mean T _e in both months, whereas cooki's mean T _b was slightly higher than mean T _e in January and slightly lower in August. Although cooki's mean T _b was higher than that of cristatellus in both months, the T _b's of the two species overlapped substantially over an annual cycle. Given the similarities in their field active T _b and the low thermal heterogeneity among microsites at Playa de Tamarindo, these species appear not to partition the thermal environment there in a coarse-grained way. Instead, the relatively small differences in their field active T _b probably result from small differences in their use of similar microhabitats within their mutually exclusive territories. Thermal resource partitioning by territorial animals is unlikely unless thermal heterogeneity is coarse-grained in relation to territory size.     

Diversity in amylopectin structure, thermal and pasting properties of starches from wheat varieties/lines

Structural, thermal and pasting diversity of starches from Indian and exotic lines of wheat was studied. Majority of the starches showed amylose content ranging between 22% and 28%. Endotherm temperatures (T_o, T_p and T_c) of the starches showed a range between 56–57, 60 –61 and 65.5–66.5 °C, respectively. Exotherms with T_p between 87.0 and 88.2 °C were observed during cooling of heated starches, indicating the presence of amylose–lipid complexes. Exotherm temperatures were negatively correlated to swelling power. Amylopectin unit chains with different degree of polymerization (DP) were observed to be associated with pasting temperature, setback and thermal (endothermic T_o, T_p, and T_c) parameters. Amylopectin unit chains of DP 13–24 showed positive relationship with endothermic T_o, T_p and T_c. Pasting temperature showed positive correlation with short chains (DP 6–12) while negative correlation with medium chain (DP 13–24) amylopectins. Setback was positively correlated to DP 16–18 and negatively to DSC amylose–lipid parameters.     

Micro-scale differences in thermal habitat quality and a possible case of evolutionary flexibility in the thermal physiology of lacertid lizards

We studied the thermal ecology of the lacertid lizards Lacerta oxycephala and Podarcis melisellensis on the Adriatic island of Vis (Croatia) during summer. These species obviously differ in microhabitat use: L. oxycephala climbs on rocks and stone walls, whereas P. melisellensis is mainly ground-dwelling in vegetation. Since theoretical considerations predict a difference in thermal quality between the species' microhabitats, this system seems to present a good opportunity to test the influence of thermal microhabitat quality on body temperature, thermoregulatory behaviour and evolution of thermal characteristics. Data on thermoregulatory behaviour, body temperatures (T_b) and habitat quality were collected in the field and selected temperatures (T_sel) were estimated in a laboratory thermogradient. Accuracy and effectiveness of thermoregulation were quantified. Thermoregulatory behaviour consisted of timing of activity, selection of places in full sun and near sun-shade transitions, and basking. As predicted, L. oxycephala occupied the microhabitat with the lower thermal quality and had on average a lower T_b. However, L. oxycephala also selected lower temperatures in the experimental thermogradient. Thus, if T_sel can be regarded as the thermoregulatory target, both species proved to be accurate and effective thermoregulators. These results corroborate the "labile view" on the evolution of thermal physiology: both L. oxcephala and P. melisellensis appear to be adapted to their respective thermal microhabitat. This is a surprising conclusion, since earlier studies have found the thermal characteristics of Lacertidae to be evolutionarily rigid.     

The thermal and energetic significance of clustering in the speckled mousebird,Colius striatus

Summary The effect of clustering behaviour on metabolism, body temperature, thermal conductance and evaporative water loss was investigated in speckled mousebirds at temperatures between 5 and 36°C. Within the thermal neutral zone (approximately 30–35 °C) basal metabolic rate of clusters of two birds (32.5 J·g^-1·h^-1) and four birds (28.5 J·g^-1·h^-1) was significantly lower by about 11% and 22%, respectively, than that of individuals (36.4 J·g^-1·h^-1). Similarly, below the lower critical temperature, the metabolism of clusters of two and four birds was about 14% and 31% lower, respectively, than for individual birds as a result of significantly lower total thermal conductance in clustered birds. Body temperature ranged from about 36 to 41°C and was positively correlated with ambient temperature in both individuals and clusters, but was less variable in clusters. Total evaporative water loss was similar in individuals and clusters and averaged 5–6% of body weight per day below 30°C in individuals and below 25°C in clusters. Above these temperatures total evaporative water loss increased and mousebirds could dissipate between 80 and 90% of their metabolic heat production at ambient temperatures between 36 and 39°C. Mousebirds not only clustered to sleep between sunset and sunrise but were also observed to cluster during the day, even at high ambient temperature. Whereas clustering at night and during cold, wet weather serves a thermoregulatory function, in that it allows the brrds to maintain body temperature at a reduced metabolic cost, clustering during the day is probably related to maintenance of social bonds within the flock.Abbreviations BMR basal metabolic rate - bw body weight - C _totab total thermal conductance - EWI evaporative water loss - M metabolism - RH relative humidity - T _a ambient temperature - T _b body temperature - T _ch chamber temperature - T _cl cluster temperature - TEWL total evaporative water loss - LCT lower critical temperature - TNZ thermal neutral zone     

Drosophila melanogaster infected with Wolbachia strain wMelCS prefer cooler temperatures

1. Temperature plays a fundamental role in the dynamics of host–pathogen interactions. Wolbachia is an endosymbiotic bacteria that infects about 40% of arthropod species, which can affect host behaviour and reproduction. Yet, the effect of Wolbachia on host thermoregulatory behaviour is largely unknown, despite its use in disease vector control programs in thermally variable environments. 2. Here, a thermal gradient was used to test whether Drosophila melanogaster infected with Wolbachia strain wMelCS exhibited different temperature preferences (T_p) to uninfected flies. 3. It was found that Wolbachia‐infected flies preferred a cooler mean temperature (T_p = 25.06 ± 0.25 °C) than uninfected flies (T_p = 25.78 ± 0.24 °C). 4. This finding suggests that Wolbachia‐infected hosts might seek out cooler microclimates to reduce exposure to, and lessen the consequences of, high temperatures. This finding has generated hypotheses that will be fruitful in areas of research for exploring the mechanisms by which the change in T_p occurs in this complex and significant host–pathogen–environment interaction.     

Wolbachia effects on thermal preference of natural Drosophila melanogaster are influenced by host genetic background,Wolbachia type,and bacterial titer

Temperature plays a fundamental role in the fitness of all organisms. In particular, it strongly affects metabolism and reproduction in ectotherms that have limited physiological capabilities to regulate their body temperature. The influence of temperature variation on the physiology and behaviour of ectotherms is well studied but we still know little about the influence of symbiotic interactions on thermal preference (T_p) of the host. A growing number of studies focusing on the Wolbachia-Drosophila host-symbiont system found that Wolbachia can influence T_p in Drosophila laboratory strains. Here, we investigated the effect of Wolbachia on T_p in wild-type D. melanogaster flies recently collected from nature. Consistent with previous data, we found reduced T_p compared to an uninfected control in one of two fly strains infected with the wMelCS Wolbachia type. Additionally, we, for the first time, found that Wolbachia titer variation influences the thermal preference of the host fly. These data indicate that the interaction of Wolbachia and Drosophila resulting in behavioural variation is strongly influenced by the genetic background of the host and symbiont. More studies are needed to better understand the evolutionary significance of T_p variation influenced by Wolbachia in natural Drosophila populations.     

Maximum thermal tolerance trades off with chronic tolerance of high temperature in contrasting thermal populations of Radix balthica

Thermal adaptation theory predicts that thermal specialists evolve in environments with low temporal and high spatial thermal variation, whereas thermal generalists are favored in environments with high temporal and low spatial variation. The thermal environment of many organisms is predicted to change with globally increasing temperatures and thermal specialists are presumably at higher risk than thermal generalists. Here we investigated critical thermal maximum (CT_max) and preferred temperature (T_p) in populations of the common pond snail (Radix balthica) originating from a small‐scale system of geothermal springs in northern Iceland, where stable cold (ca. 7°C) and warm (ca. 23°C) habitats are connected with habitats following the seasonal thermal variation. Irrespective of thermal origin, we found a common T_p for all populations, corresponding to the common temperature optimum (T_opt) for fitness‐related traits in these populations. Warm‐origin snails had lowest CT_max. As our previous studies have found higher chronic temperature tolerance in the warm populations, we suggest that there is a trade‐off between high temperature tolerance and performance in other fitness components, including tolerance to chronic thermal stress. T_p and CT_max were positively correlated in warm‐origin snails, suggesting a need to maintain a minimum “warming tolerance” (difference in CT_max and habitat temperature) in warm environments. Our results highlight the importance of high mean temperature in shaping thermal performance curves.     

The reproductive period of tarantulas is constrained by their thermal preferences (Araneae,Theraphosidae)

Locomotor and physiological performance of ectotherms are affected by temperature. Thermoregulation is achieved by changes in behavior and the selection of micro-habitats with adequate temperatures to maintain the body temperature (T_b) within a range of preference. Apart from this temperature dependence at spatial scales, ectotherms are also affected by temperature at temporal scale. For instance, ectotherms can only be active some months of the year, particularly in temperate environments. Tarantulas are ectotherms that live in burrows most of their life. Nevertheless, after the sexual maturation molt, males leave their refugia and start a wandering life searching for females to mate. The reproductive period varies among species. In some species walking males are seen in late spring or early summer, while in other species males are only seen during fall or winter. Apart from the differences in lifestyles after maturation, tarantulas exhibit sexual dimorphisms in longevity and body mass, having smaller, shorter-lived males. Thus, to optimize energetic budgets, decreasing thermoregulation costs, we hypothesize and examine a putative correlation between an individual's preferred body temperature (T_pref) and the environmental temperature during the reproductive period. Hence, we characterize T_pref in seven tarantula species and analyze which factors (i.e., time of day, body mass, and sex) correlated with it. Furthermore, we assess putative correlated evolution of T_pref with ambient temperature (minima, mean, and maxima) during the reproductive period by means of phylogenetic independent contrasts. We did not find differences in thermal preferences between sexes; and only one species, Acanthoscurria suina, exhibited diel differences in T_pref. We found evidence of correlated evolution between T_pref and minimum temperature during the reproductive period among all seven species studied herein. Our results show that the reproductive period is constrained by thermal preferences, dictating when males can start their wandering life to mate.     

Altitudinal variation of the thermal biology and running performance in the lizard Podarcis tiliguerta

Summary We studied, in the field and laboratory, aspects of the thermal biology in two populations of the lizard Podarcis tiliguerta along a 1450 m altitudinal gradient. Body temperatures (T_b) at high altitudes average lower, are more variable, but are more elevated above environmental temperatures than at sea level. Lizards partially reduced the impact of altitudinal changes in thermal loads through presumable subtle behavioural adjustments. A comparison of the thermal preferences in the laboratory, the maximal operative temperatures predicted from a biophysical model, and the activity T_b's at both sites, indicates that the main response to changing environmental conditions is an active shift in thermoregulatory set points. Integration of field T_b's and laboratory data on temperature specific sprint speeds, predicts that the mountainous lizards experience reduced running abilities that are especially acute in the early morning. Despite this impairment of running performance, the thermal sensitivity of running speed has not evolved to match the T_b's experienced by both populations. This result supports the view that the thermal physiology of this lizard is evolutionarily conservative, but the lack of information on the relation between running performance and fitness components impedes rejection of alternative hypotheses.     

The effects of thermal biology and refuge availability on the restricted distribution of an alpine lizard

Aim In an effort to disentangle the ecological processes that confine ectotherms to alpine environments, we studied the thermoregulatory and microhabitat selection behaviours of the rock lizard Iberolacerta cyreni, which is endemic to some mountains of central Spain, and of the wall lizard Podarcis muralis, which is a potential competitor of rock lizards. Location We chose three areas in the Sierra de Guadarrama (central Spain) that differed in their thermal quality [mean deviation of environmental operative temperatures from the lizards’ preferred thermal range (PTR)] and refuge availability: a pine forest (1770 m a.s.l.) in which P. muralis was the only species found, and two mixed shrub and rock sites (1770 and 1900 m a.s.l.) where both species were present. Methods In the field we collected data on refuge availability, sun exposure, body temperature (T_b) and operative temperature (T_e). Thus, we estimated the thermal habitat quality of the areas sampled and the thermoregulation accuracy and effectiveness of both species. Results The pine forest had the lowest thermal quality and refuge availability. The lower‐elevation shrub site offered the best thermal quality, but refuges were much scarcer than at the higher‐elevation site. Both species thermoregulated accurately, because mean deviations of body temperature (T_b) from PTR were considerably smaller than those of T_e. Podarcis muralis had higher T_b values than did I. cyreni, which had similar T_b values at both shrub sites, whereas P. muralis had lower T_b values at higher elevation. Overall, the thermoregulatory effectiveness (extent to which T_b values are closer to the PTR than are T_e values) of both species was similar, but whereas I. cyreni thermoregulated more efficiently at higher elevation, the opposite was true for P. muralis. At the lower‐elevation shrub site, I. cyreni remained closer to refuges than did P. muralis. Main conclusions Our results suggest that the pine forest belt might prevent the expansion of rock lizards towards lower elevations as a result of its low thermal quality and scarcity of refuges, that the thermoregulatory effectiveness of rock lizards in alpine environments depends more on refuge availability than on thermal habitat quality, and that competition with wall lizards is unlikely to explain either the distribution or the thermoregulatory effectiveness of rock lizards.     

Thermal dependence of locomotor performance in two cool-temperate lizards

Temperate-zone ectotherms experience varying or very low ambient temperatures and may have difficulty in attaining preferred body temperatures. Thus, adaptations to reduce the thermal dependence of physiological processes may be present. We measured the optimal temperature range for sprint speed and compared it with the selected body temperatures (T _sel) of two sympatric, cool-temperate lizards: the diurnal skink Oligosoma maccanni and the primarily nocturnal gecko Woodworthia (previously Hoplodactylus) “Otago/Southland”. We also investigated whether time-of-day influenced sprint speed. Contrary to results for other reptiles, we found that time-of-day did not influence speed in either species. For each species, the optimal temperature range for sprinting and T _sel overlapped, supporting the ‘thermal coadaptation’ hypothesis. However, the optimal range of temperatures for speed is not always attainable during activity by either species, which have limited opportunities to attain T _sel in the field. The thermal sensitivity of sprint speed in these two species does not appear to have evolved to fully match their current thermal environment. More data on cold-adapted species are needed to fully understand physiological adaptation in ectotherms.     

Torpor and thermal energetics in a tiny Australian vespertilionid,the little forest bat (<Emphasis Type="Italic">Vespadelus vulturnus</Emphasis>)

Data on thermal energetics for vespertilionid bats are under-represented in the literature relative to their abundance, as are data for bats of very small body mass. Therefore, we studied torpor use and thermal energetics in one of the smallest (4 g) Australian vespertilionids, Vespadelus vulturnus. We used open-flow respirometry to quantify temporal patterns of torpor use, upper and lower critical temperatures (T _uc and T _lc) of the thermoneutral zone (TNZ), basal metabolic rate (BMR), resting metabolic rate (RMR), torpid metabolic rate (TMR), and wet thermal conductance (C _wet) over a range of ambient temperatures (T _a). We also measured body temperature (T _b) during torpor and normothermia. Bats showed a high proclivity for torpor and typically aroused only for brief periods. The TNZ ranged from 27.6°C to 33.3°C. Within the TNZ T _b was 33.3±0.4°C and BMR was 1.02±0.29 mlO₂ g⁻¹ h⁻¹ (5.60±1.65 mW g⁻¹) at a mean body mass of 4.0±0.69 g, which is 55 % of that predicted for a 4 g bat. Minimum TMR of torpid bats was 0.014±0.006 mlO₂ g⁻¹ h⁻¹ (0.079±0.032 mW g⁻¹) at T _a=4.6±0.4°C and T _b=7.5±1.9. T _lc and C _wet of normothermic bats were both lower than that predicted for a 4 g bat, which indicates that V. vulturnus is adapted to minimising heat loss at low T _a. Our findings support the hypothesis that vespertilionid bats have evolved energy-conserving physiological traits, such as low BMR and proclivity for torpor.     

Effect of altitude on thermal responses of Liolaemus pictus argentinus in Argentina

Reptiles that live in cooler environments hibernate longer and, when active, limit daily activity times, allocate more time and energy toward thermoregulation, and consequently experience life-history constraints such as reduced fecundity and supra-annual reproductive cycles. This pattern becomes more extreme with increasing latitude and altitude. We compared the thermal biology of two populations of Liolaemus pictus argentinus living at two altitudes (771 and ∼1700 m asl). Environmental, microenvironmental, and operative temperatures were studied in order to describe the capture sites, sources of heat, and availability of microenvironments appropriate for thermoregulation. The body temperatures of L. p. argentinus at capture (T_b) and the preferred temperatures in the laboratory (T_p) were recorded and integrated with operative temperatures to calculate the effectiveness of thermoregulation. The high-altitude population was found to have a lower mean T_b (29 °C compared to 33 °C), while the T_p values for both populations were similar (36.7 °C). The analysis of operative temperatures and T_b in relation to T_p showed that L. p. argentinus behaves as a moderate thermoregulator at high altitude and as a poor thermoregulator at the low-altitude site probably due in part to the avoidance of predation risk.     

Pressure effects on thermal preference behaviour in gammarid amphipods from 600–1000m in Lake Baikal

Temperature preference behaviour of gammarid crustaceans from depths between 600–2000 m in Lake Baikal was studied in a system which provided a stable temperature gradient at pressures ranging from 50–150 atm. At the pressure of their habitat, these animals show well-defined modal distributions of sojourn temperatures around mean values from 3.0–5.5°C, av. 3.9 ± 0.3°C; mean modal T_p is estimated at 3.5°C. Year-round habitat temperatures are 3.0–3.6°C. The effect of changing pressure upon sojourn temperatures was explored over the range 50–150 atm. The slope of the mean sojourn temperature/pressure curves was 2.1°C/100 atm, significantly greater than 0. Mean nodal temperature estimates indicate that the corresponding slope in the range of 50–100 atm is 3°C/100 atm, and in the range of 100–150 atm, is likely to exceed 5°C/100 atm.     

Postprandial thermophily in the Danube crested newt, Triturus dobrogicus

(1) Preferred temperatures were compared between fed and fasted newts with respect to their locomotor activity (LA) in an aquatic thermal gradient (5–32.5°C). (2) Locations and LA of 17 newts in postabsorptive phase were recorded over 24 h. (3) Nine randomly chosen newts were fed (10% of their body mass) and behaviour of all newts was recorded over the next 24 h. (4) Fasted newts preferred similar water temperatures during periods of both LA and inactivity. (5) Newts preferred 2–3°C higher water temperatures after feeding irrespective of the behavioural state.