Lower temperature tolerance in the temperate,ambush foraging lizard Pseudocordylus melanotus melanotus

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An organism's thermal tolerance to the environment may indicate a thermal limit to its geographical distribution.     

Thermal tolerance and altitudinal distribution of two Sphenomorphus lizards in Taiwan

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We compared the thermal tolerances of a high-altitude skink, Sphenomorphus taiwanensis with that of the lowland S. incognitus to test whether their thermal tolerances correspond to their altitudinal distributions.     

Comparative ecology of Ostracoda (Crustacea) in two rheocrene springs (Bolu,Turkey)

A total of ten taxa belonging to the class Ostracoda of the Crustacea (Darwinula stevensoni, Candona neglecta, Cypria ophthalmica, Ilyocypris bradyi, Prionocypris zenkeri, Herpetocypris chevreuxi, Psychrodromus olivaceus, Heterocypris incongruens, Scottia pseudobrowniana, Eucypris sp.) were collected from two rheocrene Darwinula stevensoni springs (Çetin Bey and Çaygökp?nar springs) on 15 separate occasions between November 2002 and November 2004. Almost all of the species identified exhibit cosmopolitan distributions – at least in the Holarctic region. The presence of Scottia pseudobrowniana represents the second recording of this species in the ostracod fauna of Turkey. The dominant taxa in both springs was Cy. ophthalmica, I. bradyi, Pr. zenkeri and Ca. neglecta. Correlation analyses suggested a significant positive relationship in relative abundance between I. bradyi, Pr. zenkeri and Cy. ophthalmica. Species composition differed significantly between the upper and lower study sites for each spring, but differences could not be detected between sites at the same elevation across sites. Environmental tolerance index (ETI) values suggest that species with high optima and tolerance ranges show cosmopolitan characteristics.     

Diversity in growth patterns among strains of the lethal fungal pathogen <Emphasis Type="Italic">Batrachochytrium dendrobatidis</Emphasis> across extended thermal optima

The thermal sensitivities of organisms regulate a wide range of ecological interactions, including host–parasite dynamics. The effect of temperature on disease ecology can be remarkably complex in disease systems where the hosts are ectothermic and where thermal conditions constrain pathogen reproductive rates. Amphibian chytridiomycosis, caused by the pathogen Batrachochytrium dendrobatidis (Bd), is a lethal fungal disease that is influenced by temperature. However, recent temperature studies have produced contradictory findings, suggesting that our current understanding of thermal effects on Bd may be incomplete. We investigated how temperature affects three different Bd strains to evaluate diversity in thermal responses. We quantified growth across the entire thermal range of Bd, and beyond the known thermal limits (T _max and T _min). Our results show that all Bd strains remained viable and grew following 24 h freeze (?12 °C) and heat shock (28 °C) treatments. Additionally, we found that two Bd strains had higher logistic growth rates (r) and carrying capacities (K) at the upper and lower extremities of the temperature range, and especially in low temperature conditions (2–3 °C). In contrast, a third strain exhibited relatively lower growth rates and carrying capacities at these same thermal extremes. Overall, our results suggest that there is considerable variation among Bd strains in thermal tolerance, and they establish a new thermal sensitivity profile for Bd. More generally, our findings point toward important questions concerning the mechanisms that dictate fungal thermal tolerances and temperature-dependent pathogenesis in other fungal disease systems.     

Thermal Preference of the Bush Cricket <Emphasis Type="Italic">Isophya rizeensis</Emphasis>; Testing the Effect of Countergradient Selection

Thermal preference is one of the most crucial components of behavioral thermoregulation in ectotherms, and documenting the adaptation of thermal preference carries great importance for studying the evolution of thermal biology. However there are not many studies focusing on the adaptation of thermal preference in elevational and latitudinal gradients. Isophya rizeensis is a color polymorphic bush cricket species endemic to the mountainous region of northeastern Turkey. Populations of this species are distributed in a wide elevational range between 350 and 2300 m. In this study, we hypothesized that the thermal preference of Isophya rizeensis might follow a countergradient variation where crickets from higher altitudes have higher temperature preferences compared to crickets from lower altitudes. To test this hypothesis, thermal preference values (T _pref ) of crickets from three altitudes groups (low, middle and high) were measured with a thermal gradient experiment. Additionally, body temperatures (T _b ) and environmental temperatures (T _a ) were measured in field. Deviation values of T _b and T _a from T _pref were calculated to investigate the extent of thermoregulation. As Isophya rizeensis is color polymorphic species where morphology pattern changes from lighter to darker types with increasing altitude we also tested whether coloration has any effect on temperature excess (T _ex ) and thermoregulation. Thermal preference values did not differ significantly between three groups and also colouration does not influence the extent of thermoregulation in this species. These results indicate that there is not sufficient evidence for the existence of a countergradient selection related with thermal behavior. However, the deviation of body (D _b ) and environmental (D _a ) temperatures suggest that at higher altitudes thermoregulation might be more efficient than lower altitudes.     

Informative Value of Temperatures in Different Areas of the Human Body for Correcting Body Thermal Imbalance during Extravehicular Activities

Identification of noninvasive and informative sites on the body reflecting the development of body thermal imbalance during extravehicular activities (EVAs) is highly important for enhancing astronaut safety. Temperature changes were evaluated on several areas of the head (the mastoid fossa (T _mf ), the forehead (T _fo ), and the cheek (T _ch )) and on the fingers (T _fing ). Subjects were dressed in a multicompartment liquid cooling/warming garment. Studies I and II consisted of different combinations of hood versus garment cooling or warming imposed across stages; studies III and IV involved sagittally divided cooling or warming regimes with the hood worn (study III) or with the head uncovered (study IV). In studies I and II, T _mf significantly (P < 0.05) differed between stages 2, when the head was cooled and the rest of the body heated, and 3, when the head was heated and the rest of the body cooled. The T _mf changes were consistent with the thermal conditions imposed on the head but not reflective of the developing body heat deficit. In study III, the T _mf at stages 2 and 3 on the right or the left followed the thermal conditions on the ipsilateral side of the body (P < 0.01). In study IV, T _fing showed no significant differences across stages. In studies I–IV, T _fing showed consistent changes across stages (P < 0.05), reflecting the developing body heat deficit. In all studies, there were no significant differences in rectal temperature (T _re ) across stages. T _mf and temperatures at other head skin sites did not respond in accordance with the actual intensity of a heat or cold flux from the garment and were not reflective of the overall development of body thermal imbalance. T _fing was a more adequate indicator of initial thermal destabilization and provided information that would be useful for monitoring the thermal balance and comfort during EVAs.     

Proteome-wide Analysis of Protein Thermal Stability in the Model Higher Plant Arabidopsis thaliana

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Highlights

• •Over 1700 Arabidopsis proteins with thermal models in multiple replicates.
• •Melting temperature correlates with 1°, 2°, and 3° protein characteristics.
• •Ligand-induced thermal shifts are evident in complex protein extracts.

     

Sex differences in thermal detection and thermal pain threshold and the thermal grill illusion: a psychophysical study in young volunteers

Background

Sex-related differences in human thermal and pain sensitivity are the subject of controversial discussion. The goal of this study in a large number of subjects was to investigate sex differences in thermal and thermal pain perception and the thermal grill illusion (TGI) as a phenomenon reflecting crosstalk between the thermoreceptive and nociceptive systems. The thermal grill illusion is a sensation of strong, but not necessarily painful, heat often preceded by transient cold upon skin contact with spatially interlaced innocuous warm and cool stimuli.

Methods

The TGI was studied in a group of 78 female and 58 male undergraduate students and was evoked by placing the palm of the right hand on the thermal grill (20/40 °C interleaved stimulus). Sex-related thermal perception was investigated by a retrospective analysis of thermal detection and thermal pain threshold data that had been measured in student laboratory courses over 5 years (776 female and 476 male undergraduate students) using the method of quantitative sensory testing (QST). To analyse correlations between thermal pain sensitivity and the TGI, thermal pain threshold and the TGI were determined in a group of 20 female and 20 male undergraduate students.

Results

The TGI was more pronounced in females than males. Females were more sensitive with respect to thermal detection and thermal pain thresholds. Independent of sex, thermal detection thresholds were dependent on the baseline temperature with a specific progression of an optimum curve for cold detection threshold versus baseline temperature. The distribution of cold pain thresholds was multi-modal and sex-dependent. The more pronounced TGI in females correlated with higher cold sensitivity and cold pain sensitivity in females than in males.

Conclusions

Our finding that thermal detection threshold not only differs between the sexes but is also dependent on the baseline temperature reveals a complex processing of “cold” and “warm” inputs in thermal perception. The results of the TGI experiment support the assumption that sex differences in cold-related thermoreception are responsible for sex differences in the TGI.

     

A multi-trait systems approach reveals a response cascade to bleaching in corals

Background

Climate change causes the breakdown of the symbiotic relationships between reef-building corals and their photosynthetic symbionts (genus Symbiodinium), with thermal anomalies in 2015–2016 triggering the most widespread mass coral bleaching on record and unprecedented mortality on the Great Barrier Reef. Targeted studies using specific coral stress indicators have highlighted the complexity of the physiological processes occurring during thermal stress, but have been unable to provide a clear mechanistic understanding of coral bleaching.

Results

Here, we present an extensive multi-trait-based study in which we compare the thermal stress responses of two phylogenetically distinct and widely distributed coral species, Acropora millepora and Stylophora pistillata, integrating 14 individual stress indicators over time across a simulated thermal anomaly. We found that key stress responses were conserved across both taxa, with the loss of symbionts and the activation of antioxidant mechanisms occurring well before collapse of the physiological parameters, including gross oxygen production and chlorophyll a. Our study also revealed species-specific traits, including differences in the timing of antioxidant regulation, as well as drastic differences in the production of the sulfur compound dimethylsulfoniopropionate during bleaching. Indeed, the concentration of this antioxidant increased two-fold in A. millepora after the corals started to bleach, while it decreased 70% in S. pistillata.

Conclusions

We identify a well-defined cascading response to thermal stress, demarking clear pathophysiological reactions conserved across the two species, which might be central to fully understanding the mechanisms triggering thermally induced coral bleaching. These results highlight that bleaching is a conserved mechanism, but specific adaptations linked to the coral’s antioxidant capacity drive differences in the sensitivity and thus tolerance of each coral species to thermal stress.