Thermal Activity Thresholds Research Articles

Development and thermal activity thresholds of European mirid predatory bugs

Generalist predators belonging to Dicyphini (Hemiptera: Miridae) play an important role in pest control in vegetable crops. Temperature is one the most important factors affecting their efficacy as biological control agents (BCAs) and a better understanding of temperature effects can help to select the best performing species for certain climatic conditions. In this study we assessed the thermal requirements of six dicyphine species: Dicyphus bolivari (2 different strains), Dicyphus eckerleini, Dicyphus errans, Dicyphus flavoviridis, Nesidiocoris tenuis and Macrolophus pygmaeus. Two experimental methods were used: one static, by recording the developmental times at six temperatures (15–40 °C) and one dynamic, by determining low and high temperature thresholds for movement. Based on the results of both methods we identified two groups: N. tenuis, M. pygmaeus and D. bolivari showed the best performance at high temperatures and the species D. errans, D. eckerleini and D. flavoviridis were most active at low temperatures. Dicyphus bolivari and N. tenuis were the only species able to reach adulthood at the constant temperature of 35 °C. At low temperatures, D. eckerleini and D. errans were the only species still able to walk below 0 °C.The species less vulnerable for lower temperatures were more vulnerable for higher temperatures and vice-versa. Among the tested species, the larger sized species seem to be better adapted to lower temperature and the and smaller sized species better to higher temperatures. Females and males in all species differed in their cold and heat tolerance. Males were in general beter adapted to higher temperatures and females beter adapted to lower temperatures.

Unique high sensitivity to heat of axolotl TRPV1 revealed by the heterologous expression system

The thermosensation mechanism plays critical roles in various animals living in different thermal environment. We focused on an axolotl, which is a tailed amphibian originally from Lake Xochimilco area in the Vally of Mexico, and examined its behavior response to heat stimulation. Mild heat at 33 °C induced noxious locomotive activity to axolotls, but the noxious response of another tailed amphibian, Iberian ribbed newt, was not observed at 33 °C. To explore the mechanism for the temperature sensitivity of axolotls, we isolated a cDNA of TRPV1. Using the degenerate primer PCR method, we identified the DNA fragment encoding axolotl TRPV1 (axTRPV1), and then cloned a full-length cDNA. We studied the chemical and thermal sensitivities of axTRPV1 by two-electrode voltage clamp method using Xenopus oocyte expression system. Capsaicin, acid, and 2-aminoethoxydiphenylborane apparently activated axTRPV1 channels in a dose-dependent manner. The analysis of thermal sensitivity showed that axTRPV1 was significantly activated by heat but not by cold. The average temperature threshold for heat-activation was 30.95 ± 0.12 °C. This thermal activation threshold of axTRPV1 is unique and significantly low, when compared with the known thresholds of TRPV1s from various animals. Further, this threshold of axTRPV1 is well consistent with the observation of heat-induced behavior of axolotls at 33 °C, demonstrating that axolotl shows noxious response to mild heat mediated through axTRPV1.

Morphological traits are linked to the cold performance and distribution of bees along elevational gradients

AbstractAimIdentifying traits that enhance the success of animals in unhospitable climates helps to understand biogeographical patterns and to predict the consequences of climatic changes. On temperate mountains, traits that increase cold performance potentially allow species to colonize higher elevations. We first tested the importance of morphological traits for the cold performance of bees. Second, we assessed the relevance of these traits for species distributional patterns by analysing intraspecific and interspecific trait shifts along elevational gradients.LocationNational Park Berchtesgaden, Germany; Würzburg, Germany.MethodsWe determined thermal activity thresholds by measuring signs of immobility along temperature gradients under laboratory conditions and related them to morphometric traits. We sampled bee communities at 34 sites along an elevation gradient in the northern Alps, measured for all species morphometric traits and thermal activity limits in the field, and analysed how trait measures changed with elevation within and across species.ResultsLaboratory and field experiments revealed that bees with larger body size, longer hair and relatively short wings tolerated lower temperatures before reaching immobility and started being active in the field at lower temperatures than small, short‐haired and long‐winged species. In correspondence to these results, we found that morphometric traits increased (body size, hair length) or decreased (relative wing length) with increasing elevation in communities and, in case of body size, also within species.Main conclusionsResults of laboratory and field experiments and their reflectance in community‐ and species‐level trends of morphological traits along elevational gradients underscore the adaptive nature of large body size, long hair and short wings for bees’ thermal performance. Morphological traits expanding lower thermal limits probably contribute to the fitness of bees in cold environments and may simultaneously be under selection in a warming world.

Thermal thresholds of the predatory mite Balaustium hernandezi.

The lower and upper thermal activity thresholds of adult and larval Balaustium hernandezi von Heyden (Acari: Erythraeidae) are compared with those of its prey Tetranychus urticae Koch (Acari: Tetranychidae). Adult female B. hernandezi retain ambulatory function (CTmin) and movement of appendages (chill coma) at significantly lower temperatures (5.9 and −2.1 °C, respectively) than those of larval B. hernandezi (8.1 and −1.7 °C) and T. urticae (10.6 and 10.3 °C). There is no significant difference between the temperature at which adult and larval B. hernandezi and T. urticae cease walking as the temperature is raised (CTmax) (46.7, 46.3 and 47.3 °C, respectively). However, both life stages of B. hernandezi cease movement (heat coma) below the upper locomotory limits of T. urticae (46.8, 46.7 and 48.7 °C, respectively). Adult B. hernandezi have significantly faster walking speeds than larvae and T. urticae across a range of temperatures. The lower thermal activity threshold data indicate that B. hernandezi would make an effective biological control agent in temperate climates; however, the extent of the low temperature tolerances of the species suggests the potential to establish in a northern European climate.

Calixarene-Mediated Synthesis of Cobalt Nanoparticles: An Accretion Model for Separate Control over Nucleation and Growth.

The nucleation and growth of crystalline cobalt nanoparticles (Co NPs) under solvothermal conditions can be separated into distinct stages by using (i) polynuclear clusters with multivalent capping ligands to initiate nucleation, and (ii) thermolabile organometallic complexes with low autonucleation potential to promote crystalline growth. Both nucleation and growth take place within an amorphous accretion, formed in the presence of polyvalent surfactants. At the pre-nucleation stage, a calixarene complex with multiple Co2-alkyne ligands (Co16-calixarene 1) undergoes thermal decomposition above 130 °C to form "capped cluster" intermediates that coalesce into well-defined Co nanoclusters, but are resistant to further aggregation. At the post-nucleation stage, a monomer (pentyne-Co4(CO)10, or PTC) with a low thermal activation threshold but a high barrier to autonucleation is introduced, yielding ε-Co NPs with a linear relationship between particle volume and the Co mole ratio ([Cofinal]/[Coseed]). Co nanocrystals can be produced up to 40 nm with a 10-12% size dispersity within the accretion, but their growth rate depends on the activity of the supporting surfactant, with an octapropargyl calixarene derivative (OP-C11R) providing the most efficient transport of reactive Co species through the amorphous matrix. Post-growth digestion with oleic acid releases the Co NPs from the residual accretion, which can then self-assemble by magnetic dipolar interactions into flux-closure rings when stabilized by calixarene-based surfactants. These studies demonstrate that organometallic complexes can be designed to establish rational control over the nucleation and growth of crystalline NPs within an intermediate accretion phase.

The effect of acclimation temperature on thermal activity thresholds in polar terrestrial invertebrates

In the Maritime Antarctic and High Arctic, soil microhabitat temperatures throughout the year typically range between −10 and +5°C. However, on occasion, they can exceed 20°C, and these instances are likely to increase and intensify as a result of climate warming. Remaining active under both cool and warm conditions is therefore important for polar terrestrial invertebrates if they are to forage, reproduce and maximise their fitness. In the current study, lower and upper thermal activity thresholds were investigated in the polar Collembola, Megaphorura arctica and Cryptopygus antarcticus, and the mite, Alaskozetes antarcticus. Specifically, the effect of acclimation on these traits was explored. Sub-zero activity was exhibited in all three species, at temperatures as low as −4.6°C in A. antarcticus. At high temperatures, all three species had capacity for activity above 30°C and were most active at 25°C. This indicates a comparable spread of temperatures across which activity can occur to that seen in temperate and tropical species, but with the activity window shifted towards lower temperatures. In all three species following one month acclimation at −2°C, chill coma (=the temperature at which movement and activity cease) and the critical thermal minimum (=low temperature at which coordination is no longer shown) occurred at lower temperatures than for individuals maintained at +4°C (except for the CTmin of M. arctica). Individuals acclimated at +9°C conversely showed little change in their chill coma or CTmin. A similar trend was demonstrated for the heat coma and critical thermal maximum (CTmax) of all species. Following one month at −2°C, the heat coma and CTmax were reduced as compared with +4°C reared individuals, whereas the heat coma and CTmax of individuals acclimated at +9°C showed little adjustment. The data obtained suggest these invertebrates are able to take maximum advantage of the short growing season and have some capacity, in spite of limited plasticity at high temperatures, to cope with climate change.

The impact of salinity exposure on survival and temperature tolerance of theAntarctic collembolanCryptopygus antarcticus

AbstractThe collembolanCryptopygus antarcticusWillem is potentially exposed to habitat salinities equal to (or greater than) sea water, as a result of sea spray, drying of littoral habitats, dispersal or temporary entrapment on the surface of sea water, or exposure to localized salt deposits from dense vertebrate populations on terrestrial habitats. To test the impact of this exposure onC. antarcticus, the tolerance of the collembolan to being placed on the surface of sea water and solutions of higher salt concentrations is investigated. The effects of acclimation to exposure to liquids of different salinities [44, 100 and 200 parts per thousand (ppt) sea salt] on cold and heat tolerance, as well as thermal activity thresholds, are also explored.Cryptopygus antarcticusshows > 75% survival after 10 days of exposure to both sea water and 100‐ppt salt, whereas it exhibits significantly lower survival after 5 days (60% survival) and 10 days (40%) of exposure to a 200‐ppt solution. Body water content also decreases after exposure to all salinities, and particularly to the 200‐ppt solution, in which > 50% of body water is lost after 10 days. Acclimation results in greater cold tolerance, although heat tolerance at 33, 35 and 37 °C is either unaltered or reduced. The thermal activity thresholds ofC. antarcticusat both high and low temperatures are also negatively affected by saline exposure. The data demonstrate the capacity ofC. antarcticusto tolerate periods of exposure to saline conditions, and also show that this exposure can enhance cross‐tolerance to low temperatures. The present study also demonstrates that salinity‐associated stress at moderately low and high temperatures narrows the thermal range of activity, thus reducing the ability of collembolans to forage, develop and reproduce. © 2013 The Royal Entomological Society

Influence of variable current on the plasma frequency, barrier height, and thermal activation threshold in the Josephson junction

The problem of simultaneous renormalization of the plasma frequency, barrier height, and thermal activation threshold by high-frequency current passing through a Josephson junction is solved exactly. Renormalization is accomplished by a single universal function.

Comparison of thermal activity thresholds of the spider mite predators Phytoseiulus macropilis and Phytoseiulus persimilis (Acari: Phytoseiidae)

The lower and upper thermal activity thresholds of the predatory mite Phytoseiulus macropilis Banks (Acari: Phytoseiidae) were compared with those of its prey Tetranychus urticae Koch (Acari: Tetranychidae) and one of the alternative commercially available control agents for T. urticae, Phytoseiulus persimilis Athias-Henriot. Adult female P. macropilis retained ambulatory function (CTmin) and movement of appendages (chill coma) at significantly lower temperatures (8.2 and 0.4°C, respectively) than that of P. persimilis (11.1 and 3.3°C) and T. urticae (10.6 and 10.3°C). As the temperature was raised, P. macropilis ceased walking (CTmax) and entered heat coma (42.7 and 43.6°C), beyond the upper locomotory limits of P. persimilis (40.0 and 41.1°C), but before T. urticae (47.3 and 48.7°C). Walking speeds were investigated and P. persimilis was found to have significantly faster ambulation than P. macropilis and T. urticae across a range of temperatures. The lower thermal activity threshold data indicate that P. macropilis will make an effective biological control agent in temperate climates.

Ganglion-specific splicing of TRPV1 underlies infrared sensation in vampire bats

Vampire bats (Desmodus rotundus) are obligate blood feeders that have evolved specialized systems to suit their unique sanguinary lifestyle 1–3. Chief among such adaptations is the ability to detect infrared radiation as a means of locating hot spots on warm-blooded prey. Among vertebrates, only vampire bats, boas, pythons, and pit vipers are capable of detecting infrared radiation 1,4. In each case, infrared heat is detected by trigeminal nerve fibers that innervate specialized pit organs on the animal’s face 5–10. Thus, vampire bats and snakes have taken thermosensation to the extreme by developing specialized systems for detecting infrared radiation. As such, these creatures provide a window into the molecular and genetic mechanisms underlying evolutionary tuning of thermoreceptors in a species or cell type specific manner. Previously, we have shown that snakes co-opt a non-heat sensitive channel (vertebrate TRPA1) to produce an infrared detector 6. Here we show that vampire bats tune an already heat sensitive channel (TRPV1) by lowering its thermal activation threshold to ~30°C. This is achieved through alternative splicing of TRPV1 transcripts to produce a channel with a truncated C-terminal cytoplasmic domain. Remarkably, these splicing events occur exclusively in trigeminal ganglia (TG), and not dorsal root ganglia (DRG), thereby maintaining a role for TRPV1 as a detector of noxious heat in somatic afferents. This reflects a unique organization of the bat TRPV1 gene that we show to be characteristic of Laurasiatheria mammals (cows, dogs, and moles), supporting a close phylogenetic relationship with bats. These findings reveal a unique molecular mechanism for physiological tuning of thermosensory nerve fibers.

High-speed, clinical-scale microfluidic generation of stable phase-change droplets for gas embolotherapy

In this study we report on a microfluidic device and droplet formation regime capable of generating clinical-scale quantities of droplet emulsions suitable in size and functionality for in vivo therapeutics. By increasing the capillary number-based on the flow rate of the continuous outer phase-in our flow-focusing device, we examine three modes of droplet breakup: geometry-controlled, dripping, and jetting. Operation of our device in the dripping regime results in the generation of highly monodisperse liquid perfluoropentane droplets in the appropriate 3-6 μm range at rates exceeding 10(5) droplets per second. Based on experimental results relating droplet diameter and the ratio of the continuous and dispersed phase flow rates, we derive a power series equation, valid in the dripping regime, to predict droplet size, D(d) approximately equal 27(Q(C)/Q(D))(-5/12). The volatile droplets in this study are stable for weeks at room temperature yet undergo rapid liquid-to-gas phase transition, and volume expansion, above a uniform thermal activation threshold. The opportunity exists to potentiate locoregional cancer therapies such as thermal ablation and percutaneous ethanol injection using thermal or acoustic vaporization of these monodisperse phase-change droplets to intentionally occlude the vessels of a cancer.

Thermal activity thresholds of the parasitic wasp Lysiphlebus testaceipes and its aphid prey: implications for the efficacy of biological control

Adult parasitoids Lysiphlebus testaceipes Cresson (Hymenoptera: Aphidiidae) lose locomotory function and enter chill coma at significantly lower temperatures (−0.1 and −8.0 °C, respectively) than their second-instar hosts, the black bean aphid Aphis fabae Scop. (Hemiptera: Aphididae) (5.6 and 2.3 °C, respectively). Parasitoids are also more heat tolerant, stop walking at 41.4 °C, with heat coma at 44.1 °C, than the aphid (39.1 and 43.0 °C, respectively). Furthermore, across a range of temperatures (0–20 °C), L. testaceipes has considerably faster walking speeds than A. fabae. These data are discussed in relation to the climatic conditions under which L. testaceipes would be an effective control agent, and the likelihood of establishment and spread in northern European climates.

Thermal activity thresholds of the predatory mirid Nesidiocoris tenuis: implications for its efficacy as a biological control agent

This study investigates the thermal activity thresholds of the predatory mirid Nesidiocoris tenuis Reuter (Hemiptera: Miridae) and two spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae). Adult N. tenuis lost locomotory function and entered chill coma at significantly lower temperatures (4.0°C and 0.3°C, respectively) than adult T. urticae (7.0°C and 5.7°C, respectively). However, the mirids were more adversely affected by high temperatures, with T. urticae losing the ability to walk and entering heat coma at higher temperatures (47.3°C and 49.7°C, respectively) than N. tenuis (43.5°C and 46.6°C, respectively). Across a range of temperatures (2.5–20°C) adult N. tenuis had faster walking speeds than T. urticae. These data are discussed in relation to the climatic conditions under which N. tenuis would be an effective biocontrol agent.

Neutron spectral measurement of the Ohio state research reactor pneumatic tube

Pneumatic irradiation facilities are used for neutron activation analysis, materials testing, electronics hardening, and radioisotope production. The application of these facilities can benefit from a greater understanding of the neutron energy profile inside the irradiation cavities as often only the cadmium ratio is known. A program to measure the energy-dependent neutron fields inside the pneumatic tube at the Ohio State University Research Reactor was undertaken using wires consisting of thermal activation materials and threshold reaction materials with and without thermal and resonance absorbers surrounding them. The measured activities were unfolded using the MAXED unfolding code to reconstruct the neutron energy spectra and compared to the MCNP-calculated flux.

TRPV1 Gene Required for Thermosensory Transduction and Anticipatory Secretion from Vasopressin Neurons during Hyperthermia

Increases in core body temperature promote thermoregulatory cooling by stimulating sweat production and preemptive renal water reabsorption through the release of vasopressin (VP, antidiuretic hormone). The mechanism by which the hypothalamus orchestrates this anticipatory VP release during hyperthermia is unknown but has been linked to a central thermosensory mechanism. Here, we report that thermal stimuli spanning core body temperatures activate a calcium-permeable, ruthenium red- and SB366791-sensitive nonselective cation conductance in hypothalamic VP neurons. This response is associated with a depolarizing receptor potential and an increase in action potential firing rate, indicating that these neurons are intrinsically thermosensitive. The thermosensitivity of VP neurons isolated from trpv1 knockout (Trpv1(-/-)) mice was significantly lower than that of wild-type counterparts. Moreover, Trpv1(-/-) mice showed an impaired VP response to hyperthermia in vivo. Channels encoded by the trpv1 gene thus confer thermosensitivity in central VP neurons and contribute to the thermal control of VP release in vivo.

Plasticity and superplasticity in the acclimation potential of the Antarctic mite Halozetes belgicae (Michael)

The plasticity of an organism's phenotype may vary spatially and temporally, and across levels of physiological organisation. Given the adaptive value of plasticity in heterogeneous environments, it might be expected that it will be expressed most in a phenotype's most significant adaptive suites; at high latitudes, one of these is low temperature adaptation. This study examines the phenotypic plasticity of cold acclimation in the Antarctic mite, Halozetes belgicae (Michael). Both plastic and 'superplastic' (extreme plasticity) acclimation responses were found. Plastic responses were evident in responses to laboratory acclimation and field acclimatisation. 'Superplasticity' was found in its ability to rapidly cold harden (RCH) at 0, -5 and -10 degrees C. For example, after just 2 h of acclimation at 0 degrees C, mites acclimated at 10 degrees C shifted their supercooling points (SCPs) by approx. 15 degrees C. In terms of the combined speed of induction and lowering of lethal temperature, this is the most potent RCH response yet reported for a terrestrial arthropod. RCH was also expressed in thermal activity thresholds. Mechanisms responsible for significant differences in recovery from chill torpor are unknown; however, analysis of gut nucleator abundance suggest that the dynamic management of supercooling potential is largely achieved behaviourally, via evacuation. Comparisons with the literature reveal that plasticity in this species varies latitudinally, as well as temporally. The high degree of plasticity identified here is coincident with H. belgicae's occupation of the most exposed spatial niche available to Antarctic terrestrial arthropods.

The effect of alternating current on the thermal activation threshold of the tunnel Josephson junctions

The process of thermal activation in the tunnel Josephson junctions simultaneously carrying both constant (dc) and alternating (ac) currents has been studied. The presence of the ac component leads to a decrease in the potential barrier for a metastable state of the Josephson junction. The thermal activation threshold is expressed as a function of the ac current amplitude. The results agree with the data of recent experiments on the statistics of switching from a superconducting to resistive state in the Josephson tunneling junctions.

Theoretical calculations of product percentage yields for the thermal decomposition of 2-chloro-1,1-difluoroethane

Theoretical calculations of the product percentage yields for the thermal decomposition of CHF 2CH 2Cl are consistent with the experimental percentage product yields supporting the proposal that the unexpected formation of 1,2-difluoroethene can be explained by a 1,2-FCl interchange converting CHF 2CH 2Cl into CHFClCH 2F, which then undergoes a 2,1-HCl elimination. Thermal activation rate constants and threshold energy barriers for dominant reactions in this system were calculated. Theoretical product percentage yields varied greatly because different basis sets produced a wide range of threshold energy barriers, but the computational results were generally consistent with a recent experimental report.

Effects of mesalamine on the hsp72 stress response in rat IEC-18 intestinal epithelial cells

BACKGROUND & AIMS: Mesalamine has many effects and is commonly used for the treatment of inflammatory bowel diseases. Because sodium salicylate, a related compound, modulates the heat shock protein (hsp72) response in nonepithelial cells, the possibility that mesalamine confers cell protection by increasing intestinal epithelial hsp72 expression was examined.METHODS: Rat intestinal IEC-18 cells were treated with 0.3-3 mmol/L mesalamine and thermally stressed (39 degrees C-42 degrees C) for 23 minutes. The effects of mesalamine on basal expression and the threshold and time course of hsp72 thermal induction were determined.RESULTS: Although mesalamine had no effects on the basal hsp72 expression or its thermal activation threshold in IEC-18 cells, it accelerated and augmented thermal induction of hsp72 within the first 2 hours of exposure. This was associated with a transient increase in heat shock factor-heat shock element binding and enhanced cellular protection against oxidant-induced injury. In contrast, both mesalamine and sodium salicylate have been shown to lower the thermal induction threshold but not to enhance the hsp72 response in HeLa cells.CONCLUSIONS: Mesalamine augments thermal induction of the intestinal epithelial hsp72 expression in a manner that differs from that in nonintestinal epithelial cells. This effect is accompanied by increased cellular protection against oxidant injury.(Gastroenterology 1997 Nov;113(5):1474-9)

Thermal preference and activity thresholds in populations of Argia vivida (Odonata: Coenagrionidae) from habitats with different thermal regimes

The hypothesis was tested that isolated populations of Argia vivida Hagen living in habitats with different thermal regimes would show similar larval temperature preferenda, similar distributions in a temperature gradient, similar larval upper temperature acitivity thresholds, and similar adult minimum temperature flight thresholds. The hypothesis was supported in all cases, except for distribution within the gradient, where there were significantly fewer observations below 22°C in a population from a habitat with a fluctuating diel and annual temperature regime than in a population from a more thermally stable habitat. Larval modal temperature preferendum was 28°C; escape temperature (EST) was 35.4–36.4°C, critical thermal maximum (CTM) was 39.1–41.0°C, and upper lethal temperature (ULT) was 44.4–46.0°C. While technical difficulties affected the estimates of flight thresholds, there was no difference between the field estimates from different sites. Minimum body temperature for flight appears to be about 25°C, apparently higher than for several other zygopterans, while larval activity thresholds and 96 hr LD50 of 36.8°C are similar to those recorded for other odonates.