Thermal Minimum Research Articles

Physiological and morphological traits affect contemporary range expansion and implications for species distribution modelling in an amphibian species.

Species range shifts due to climate alterations have been increasingly well-documented. Although amphibians are one of the most sensitive groups of animals to environmental perturbations due to climate change, almost no studies have offered evidence of poleward distribution shifts in this taxon in response to climate warming. Range shifts would be facilitated by variation in traits associated with the ability of species to persist and/or shift their range in the face of climate change, but the extent and consequences of intraspecific variation in these traits is unclear. We studied the role of intraspecific variation in the ongoing range shift of green treefrogs (Hyla cinerea) in response to climate change. We explored factors that are often associated with range shifts to test the hypothesis that there are differences in these traits between recently range-expanded and nearby historical populations. We then tested the consequences of intraspecific variation for modelling climate-induced range shifts by comparing species distribution models (SDMs) that used as input either data from the entire species range or separate inputs from 'subpopulations' corresponding to the historical range or the recently expanded range. We expected that building a separate SDM for each population would more accurately characterize the species range if historical and expanded populations differed in traits related to their response to climate. We found that critical thermal minimum decreased and thermal breadth increased with latitude, but the effect of latitude was significantly stronger for expanded populations compared to historical populations. Additionally, we found that individuals from expanded populations had longer leg lengths when compared to their historical counterparts. Finally, we found higher model accuracy for one of the population-level SDMs than the species-level SDM. Our results suggest that thermal tolerance and dispersal morphologies are associated with amphibian distributional shifts as these characteristics appear to facilitate rapid range expansion of a native anuran. Additionally, our modelling results emphasize that SDM accuracy could be improved by dividing a species range to consider potential differences in traits associated with climate responses. Future research should identify the mechanisms underlying intraspecific variation along climate gradients to continue improving SDM prediction of range shifts under climate change.

Magical role of iron nanoparticles for enhancement of thermal efficiency and gene regulation of fish in response to multiple stresses

The present study addresses the challenges of uncontrolled temperature and pollution in aquatic environments, with a focus on fish ability to tolerate high temperature. The investigation aimed to determine the role of iron nanoparticles (Fe-NPs) in enhancing the thermal tolerance of Pangasianodon hypophthalmus exposed to high-temperature stress, arsenic (As), and ammonia (NH3) toxicity. Fe-NPs were synthesized using green approaches, specifically from fish gill. The dietary Fe-NPs were formulated and supplemented at 10, 15, and 20 mg kg⁻1 of feed. Notably, Fe-NPs at 15 mg kg⁻1 diet significantly reduced the critical thermal minimum (CTmin) (14.44 ± 0.21 °C) and the lethal thermal minimum (LTmin) (13.46 ± 0.15 °C), compared to the control and other treatment groups. Conversely, when Fe-NPs at 15 mg kg⁻1 were supplemented with or without exposure to stressors (As + NH3+T), the critical thermal maximum (CTmax) increased to 47.59 ± 0.16 °C, and the lethal thermal maximum (LTmax) increased to 48.60 ± 0.37 °C, both significantly higher than the control and other groups. A strong correlation was observed between LTmin and CTmin (R2 = 0.90) and between CTmax and LTmax (R2 = 0.98). Furthermore, dietary Fe-NPs at 15 mg kg⁻1 significantly upregulated the expression of stress-related genes, including HSP70, iNOS, Caspase-3a, CYP450, MT, cat, sod, gpx, TNFα, IL, TLR, and Ig. The enhanced thermal tolerance (LTmin and LTmax) can be attributed to these gene regulations, suggesting the mechanistic involvement of Fe-NPs in improving thermal resilience. Overall, the findings demonstrate that dietary supplementation with Fe-NPs, particularly at 15 mg kg⁻1, improves thermal tolerance and stress response in P. hypophthalmus by enhancing gene expression and overall thermal efficiency under stressor conditions.

Seismic evidence of an extremely thin crust along a 70 Ma slow-spreading crustal segment in the equatorial Atlantic Ocean

The oceanic crust at slow-spreading ridges is formed by a combination of magmatic and tectonic processes. Seismic tomographic studies, commonly used to determine crustal structures, indicate that mature slow-spreading crust has an average thickness of 6.1 ± 0.9 km, with a lower to upper crustal thickness ratio of 2.3. However, tomographic methods are based on high-frequency approximations and can only provide information about large-scale crustal structures. Using seismic full-waveform inversion applied to ocean bottom seismometer data, we report the presence of nearly uniform and extremely thin crust (4 ± 0.2 km) with a lower to upper crustal thickness ratio of 0.74 along an ∼100 km, 70 Ma crustal segment formed at the slow-spreading Mid-Atlantic Ridge in the equatorial Atlantic Ocean. This thin crust is underlain by a Moho transition zone that is 1 ± 0.5 km thick, resulting in a combined crustal and Moho transition zone thickness of 5 ± 0.6 km. The crustal thinning is primarily due to the thinning of the lower crust, suggesting that a significant part of the crust is formed by lava flows and dike intrusions. The presence of an extremely thin crust indicates a decrease in mantle temperature by at least 50 °C, suggesting a vast extent of the upper mantle thermal minimum in the equatorial Atlantic Ocean, and the absence of influence of the mantle from the Siera Leone mantle plume 70 m.y. ago.

A flexible model for thermal performance curves.

Temperature responses of many biological traits-including population growth, survival, and development-are described by thermal performance curves (TPCs) with phenomenological models like the Briere function or mechanistic models related to chemical kinetics. Existing TPC models are either simple but inflexible in shape, or flexible yet difficult to interpret in biological terms. Here we present flexTPC: a model that is parameterized exclusively in terms of biologically interpretable quantities, including the thermal minimum, optimum, and maximum, and the maximum trait value. FlexTPC can describe unimodal temperature responses of any skewness and thermal breadth, enabling direct comparisons across populations, traits, or taxa with a single model. We apply flexTPC to various microbial and entomological datasets, compare results with the Briere model, and find that flexTPC often has better predictive performance. The interpretability of flexTPC makes it ideal for modeling how thermal responses change with ecological stressors or evolve over time.

How hot is too hot? Thermal tolerance, performance, and preference in juvenile mangrove whiprays, Urogymnus granulatus

Mangrove habitats can serve as nursery areas for sharks and rays. Such environments can be thermally dynamic and extreme; yet, the physiological and behavioural mechanisms sharks and rays use to exploit such habitats are understudied. This study aimed to define the thermal niche of juvenile mangrove whiprays, Urogymnus granulatus. First, temperature tolerance limits were determined via the critical thermal maximum (CTMax) and minimum (CTMin) of mangrove whiprays at summer acclimation temperatures (28 °C), which were 17.5 °C and 39.9 °C, respectively. Then, maximum and routine oxygen uptake rates (ṀO2max and ṀO2routine, respectively), post-exercise oxygen debt, and recovery were estimated at current (28 °C) and heatwave (32 °C) temperatures, revealing moderate temperature sensitivities (i.e., Q10) of 2.4 (ṀO2max) and 1.6 (ṀO2routine), but opposing effects on post-exercise oxygen uptake. Finally, body temperatures (Tb) of mangrove whiprays were recorded using external temperature loggers, and environmental temperatures (Te) were recorded using stationary temperature loggers moored in three habitat zones (mangrove, reef flat, and reef crest). As expected, environmental temperatures varied between sites depending on depth. Individual mangrove whiprays presented significantly lower Tb relative to Te during the hottest times of the day. Electivity analysis showed tagged individuals selected temperatures from 24.0 to 37.0 °C in habitats that ranged from 21.1 to 43.5 °C. These data demonstrate that mangrove whiprays employ thermotaxic behaviours and a thermally insensitive aerobic metabolism to thrive in thermally dynamic and extreme habitats. Tropical nursery areas may, therefore, offer important thermal refugia for young rays. However, these tropical nursery areas could become threatened by mangrove and coral habitat loss, and climate change.

Thermal tolerance for the tropical clawed frog, Xenopus tropicalis with comments on comparative methods for amphibian studies

Thermal tolerance data are important for identifying the potential range of non-native species following introduction and establishment. Such data are particularly important for understanding invasion risks of tropical species introduced to temperate climates and identifying whether they can survive outside tropical regions. A breeding population of the tropical clawed frog (Xenopus tropicalis) was recently discovered in west-central Florida, U.S.A. This fully aquatic species is native to the rainforest belt of west Africa and has not been documented outside its native range. Because of the lack of invasion history, data are sparse on the thermal limits for this species. We used chronic lethal and critical thermal methodologies to investigate thermal tolerance on adult stages and critical thermal methods on tadpoles. Because of our use of both chronic and critical methodologies, we also examined the literature to reveal common methods used to investigate thermal minimum and maximum temperature in amphibians, which were found to be dominated by the critical maximum. Chronic lethal temperatures for adult X. tropicalis were 9.73 °C and 36.68 °C. Critical temperatures were affected by acclimation temperature and life stage; adults were more tolerant of extreme temperatures. Based on these critical thermal data and the fact that breeding tends to occur when temperatures are suitable for survival, tadpole stages are unlikely to be affected by extreme temperatures. Instead, range expansion in Florida will likely be limited by the adult stages. Our findings indicate that the tropical clawed frog could occupy much of southern Peninsular Florida and other tropical and subtropical regions worldwide.

Thermal tolerance, development, and physiological impacts of climate warming on zoea larvae of brachyuran crabs

Predicted effects of increasing ocean temperatures, due anthropogenic climate change, might be more challenging for early life history stages owing to reduced thermal tolerance. Thus, determining species responses to the projected climate warming conditions on marine ecosystems is essential to access their vulnerability. Here, we experimentally evaluated the effect of increased temperature on larval survival, development time and metabolic responses of two intertidal crab species (Menippe nodifrons and Ucides cordatus). The metabolic rate (measured as oxygen consumption), ammonia excretion and heartbeat rates were measured in standard fashion way, while the coefficient of temperature was obtained as a measure of organism's sensitivity to temperature increase. Critical thermal maximum and minimum, and thermal safety margins were also obtained. The results indicate a decrease in survival probability and development time for both species, from zoea I to zoea III stage, which was seen in higher extent to larvae of M. nodifrons. There is no significant effect of temperature increase on heartbeats and ammonia excretion rates to both species; however, increases in temperature had a differential effect on metabolic responses of two species. In addition, the critical thermal limits for the larval phase were described for the first time, suggesting that larvae of M. nodifrons are more vulnerable and have lower acclimation capacity to warming waters. Although a high sensitivity in metabolism was seen in U. cordatus, this species demonstrates higher thermal tolerance accompanied by a greater physiological plasticity. Our data emphasize that warming of coastal waters may reduce the larval survival and development time of both species, which can potentially impact its distribution and population size.

Thermal Tolerance of Larval Flannelmouth Sucker Catostomus latipinnis Acclimated to Three Temperatures

As water temperatures rise in streams due to global temperature variations, dams, and increased water usage, native fish species face uncertain futures. Our study defines the thermal limits of flannelmouth sucker larvae. By raising sucker eggs at three acclimation temperatures (11 °C, 16 °C, and 22 °C), we defined ideal conditions for larval survival and the temperature tolerance range using critical thermal maximum (CTMax) and minimum (CTMin) trials. Larvae survived best at 16 °C. Within our three acclimation temperatures, our data suggest that larvae can survive static temperatures between 6.9 °C and 26.4 °C. Beyond an upper temperature of 34.8 °C and a lower temperature of 6.3 °C, these fish may fail to adapt. While flannelmouth suckers withstand high temperatures, even small temperature decreases prove detrimental. By defining the temperature limits of the flannelmouth sucker, we can make informed management decisions to preserve the populations of this desert fish.

Predicted impact, establishment and distribution of Heikertingerella sp. (Coleoptera, Chrysomelidae), recently released for the biological control of Tecoma stans in South Africa

Abstract Biological control practitioners are required to demonstrate that candidate agents are not only safe for release, but will establish widely in their new range with a significant impact on the target weed. We conducted this study in quarantine to provide insight into the impact and distribution of the root‐feeding flea beetle Heikertingerella sp. (Chrysomelidae), released in early 2023 against the invasive tree Tecoma stans (L.) (Bignoniaceae) in South Africa. We studied the effects of low and high beetle densities on plant growth and biomass, and F1 progeny production by the beetle. There were significant reductions in plant growth and biomass accumulation in the beetle‐exposed plants, relative to the controls. P1 adults damaged significantly more leaflets, with significantly higher F1 progeny production, at high beetle densities. The MaxEnt model predictions suggested that most of South Africa is climatically highly suitable for Heikertingerella sp., particularly along the southern and eastern coasts where the weed is most prevalent. Only the inland regions of the Northern Cape Province, depicting the driest and hottest part of the country where the weed does not occur, were predicted to be unsuitable for Heikertingerella sp. The beetle's thermal physiology, as determined by its critical thermal minimum and maximum temperatures and lower and upper lethal temperatures (LT50), suggests tolerance to temperature extremes in at least four of the eight provinces that fall within the range of T. stans in South Africa. Our results further justify the release of Heikertingerella sp. in areas predicted as suitable in South Africa.

Toward new biomarkers of cold tolerance: microRNAs regulating cold adaptation in fish are differentially expressed in cold-tolerant and cold-sensitive Nile tilapia (Oreochromis niloticus)

Overcoming the negative effects of cold stress in Nile tilapia (Oreochromis niloticus) is of great interest for the overall aquaculture economy. Recent evidence suggests that microRNAs may regulate mechanisms of cold adaptation in fish and could be potential biomarkers of cold tolerance in these animals. However, information on how microRNAs regulating cold adaptation in fish are expressed in cold-tolerant and cold-sensitive fish is still scarce. Therefore, the aim of the present study is to investigate the relationship between a panel of previously identified differentially expressed microRNAs in fish exposed to low temperatures and their association with cold tolerance in Nile tilapia. To this end, fish were individualized based on their weight and length, and subjected to a critical thermal minimum (CTmin) test. Blood samples were collected before and after the CTmin test. After the CTmin, brain and liver tissues were collected. Fish were separated into cold-tolerant and cold-sensitive based on their CTmin results. Untreated fish were used as control. The relative expression of miR-9-3p, miR-135c, miR-9-5p, miR-30b, miR-122, miR-92a was assessed through qPCR. Additionally, qPCR was used to measure the mRNA relative expression of IGF-I and SCD in the tissues. Cortisol and biochemical parameters were determined in plasma samples. As a result, miR-92a was up-regulated in the liver of cold-sensitive fish and in the blood of cold-tolerant fish post-CTmin. miR-30b was up-regulated in the blood and liver of cold stressed fish. In the brain, miR-9-5p and miR-9-3p were up-regulated in cold-tolerant fish post-CTmin. Furthermore, miR-122 and miR-135c expression levels remained similar to the control post-CTmin. In addition, miR-122 and miR-92a were differentially expressed in the blood of cold-tolerant and cold-sensitive Nile tilapia pre-CTmin. Therefore, besides regulating fish cold acclimation responses differently in cold-tolerant and cold-sensitive fish, miRNAs may also regulate pre-existing physiological conditions that are determinant to cold tolerance in Nile tilapia. In the transcriptional level, SCD expression increased in both cold-tolerant and cold-sensitive fish post-CTmin. Cold-tolerant Nile tilapia post-CTmin had increased levels of plasma cholesterol and IGF-I mRNA in the liver, which could mean an adaptive advantage. The present findings provide new insights on the role of post-transcriptional regulation of cold tolerance in Nile tilapia. Furthermore, miRNAs differentially expressed in cold-tolerant Nile tilapia may be potential targets for the development of new biomarkers and aid in the breeding of cold-tolerant strains in this species.

Seasonal shifts in gut microbiota and cold tolerance metrics in a northern population of Reticulitermes flavipes (Blattodea: Rhinotermitidae).

Eastern subterranean termites, Reticulitermes flavipes (Kollar), are widely distributed across North America where they are exposed to a broad range of environmental conditions. However, mechanisms for overwintering are not well understood. Wisconsin is a unique location to study mechanisms of cold tolerance as it represents the northern boundary for persistent R. flavipes populations. In this study, we evaluated seasonal shifts in cold tolerance using critical thermal minimum (CTmin) and supercooling point (SCP) and examined how these measurements correlate to changes in the microbial community of the termite gut. Results showed seasonal acclimatization to cold, which is consistent with the use of behavioral freeze-avoidant mechanisms. However, these insects also demonstrated an increased susceptibility to freezing later in the season, which may be tied to changes in gut microbiota. Our results found shifts in the composition of the gut microbiome in R. flavipes between mid- to late summer and early to late fall. These differences may be suggestive of a change in metabolism to adjust to a period of reduced feeding and increased metabolic stress during overwintering. Specifically, results showed an increased abundance of Methanobrevibacter sp. (Euryarchaeota) associated with cold, which may be indicative of a metabolic shift from acetogenesis to methanogenesis associated with overwintering. Further work is needed focusing on specific contributions of certain gut microbes, particularly their role in metabolic adaptability and in providing protection from oxidative stress associated with changes in environmental conditions.

Experimental research of photovoltaic-valley power hybrid heating system with phase change material thermal storage

The widespread integration of high-ratio distributed photovoltaic (PV) systems in buildings calls for flexible load management to align with municipal power peaks and PV variability. To address the timing and demand mismatches between PV generation and building energy needs, energy storage systems are used to manage PV excess, aid in grid peak shaving, and support building heating. This research develops a Photovoltaic-Valley power complementary phase change energy storage heating system, designed to consume photovoltaic and valley power for the decentralized heating of individual rooms, thus optimizing distributed energy utilization. A CPCM of magnesium chloride hexahydrate, EG, and calcium hydroxide, designed for indoor heating, was created with a phase change temperature around 117.9 °C and an enthalpy of 106.2 kJ/kg. An experimental platform was established to test the system and its control strategy, showing that the PV-powered phase change energy storage heater effectively keeps indoor temperatures above the thermal comfort minimum of 18 °C. As the PV guarantee rate increases, the system improves indoor temperature regulation and significantly reduces fluctuations. Operating costs are over 30% lower than those of traditional heating networks and natural gas systems, underscoring substantial energy savings and emission reductions. This research provides an integrated approach for optimizing building PV consumption, managing grid peaks, and regulating indoor temperatures with phase change energy storage heating systems.

Thermal sensitivity of Rhinella arenarum tadpole at low concentrations of dimethoate pesticides

One of the main causes of contamination of aquatic environments, which affects biotic communities, is the use of pesticides in agricultural regions. Amphibians are considered good bio-indicators of aquatic pollution, because they are one of the most susceptible groups to pollution. Several studies suggest that both pollution and climate change produce synergistic effects in amphibians which amplify the toxicity afecting survival, and malformations with an increase in temperature. We studied the sensitivity of sublethal concentrations of dimethoate in Rhinella arenarum tadpoles on two fitness related thermal traits including locomotor swimming performance and thermal tolerance limits (CTmax = critical thermal maximum and CTmin = critical thermal minimum). The locomotor performance of R. arenarum tadpoles decreased with increasing sublethal dimethoate concentrations up to ∼60 % at intermediates dimethoate concentration. The tadpoles showed a tendency to decrease their tolerance to high temperatures (CTmax) with increasing dimethoate concentration around ∼0.5 °C, however no significant differences were found among treatments. Similarly, tadpoles showed decreases in their cold resistance (CTmin) with dimethoate concentrations, around 1 °C the high concentrations of dimethoate. The increase of atypical climatic events, such as heat waves may put R. arenarum tadpoles at greater risk when exposed to dimethoate. Our results show that the sublethal concentrations of the dimethoate pesticide may affect the fitness and survival of the larvae of R. arenarum in natural, and seminatural enviroments.

Changes in thermal sensitivity of Rhinella arenarum tadpoles (Anura: Bufonidae) exposed to sublethal concentrations of different pesticide fractions (Lorsban® 75WG).

The intensive use of agrochemicals and the rapid increase of global temperatures have modified the thermal conditions of aquatic environments, thus increasing amphibians' vulnerability to global warming and positioning them at great risk. Commercial formulations of chlorpyrifos (COM) are the pesticides most widely used in agricultural activities, with a high toxic potential on amphibians. However, little is known about the separate effects of the active ingredient (CPF) and adjuvants (AD). We studied the thermal sensitivity at different concentrations and pesticide fractions in Rhinella arenarum tadpoles, on thermal tolerance limits (CTmax = Critical thermal maximum and CTmin = Critical thermal minimum), swimming speed (Ss), Optimum temperature (Top), and Thermal breadth 50 (B50). Our results demonstrate that the pesticide active ingredient, the adjuvants, and the commercial formulation of chlorpyrifos differentially impair the thermal sensitivity of R. arenarum tadpoles. The pesticide fractions affected the heat and the cold tolerance (CTmax and CTmin), depending on the concentrations they were exposed to. The locomotor performance (Ss, Top, and B50) of tadpoles also varied among fractions, treatments, and environmental temperatures. In the context of climate change, the outcomes presented are particularly relevant, as mean temperatures are increasing at unprecedented rates, which suggests that tadpoles inhabiting warming and polluted ponds are currently experiencing deleterious conditions. Considering that larval stages of amphibians are the most susceptible to changing environmental conditions and the alarming predictions about environmental temperatures in the future, it is likely that the synergism between high temperatures and pesticide exposure raise the threat of population deletions in the coming years.

Ingestion and respiration rates of a common coastal mysid respond differently to diurnal temperature fluctuation

AbstractAnimals face strong environmental variability even on short time scales particularly in shallow coastal habitats, forcing them to permanently adjust their metabolism. Respiration rates of aquatic ectotherms are directly influenced by water temperature, whereas ingestion rates might additionally be influenced by behavior. We aim to understand how respiration and ingestion rates of an aquatic invertebrate respond to changing temperature during a diurnal thermal fluctuation cycle and how both processes are related. We studied the benthopelagic mysid Neomysis integer as an important food web component of coastal ecosystems. Mysids were collected at the southern Baltic Sea coast and exposed in the laboratory to either constant temperature of 15°C or daily temperature fluctuation of 15 ± 5°C. Short‐term (1–2 h) respiration and ingestion rates were measured at four equidistant time points within 24 h and did not differ among time points at constant temperature, but differed among time points in the fluctuating treatment. Respiration was highest at the thermal maximum and lowest at the thermal minimum. Ingestion rates showed the opposite pattern under fluctuation, likely due to differences in underlying thermal performance curves. When temperature transited the average, the direction of temperature change influenced the animals' response in respiration and ingestion rates differently. Our results suggest that respiration is not only instantaneously affected by temperature, but also influenced by the previously experienced direction of thermal change. Our experiment, using an important non‐model organism, delivered new insights on the relationship between the crucial organismal processes ingestion and respiration under thermal variability.

Temperature‐ and ration‐dependent winter growth in northern‐stock Black Sea Bass juveniles

AbstractObjectiveThe northern stock of Black Sea Bass Centropristis striata has spatially expanded over the past decade, potentially due to warming northwest Atlantic Shelf waters affecting overwintering.MethodsTo gather empirical data on temperature‐dependent energetics, we quantified winter growth and lipid accumulation in juveniles from Long Island Sound using two experiments.ResultExperiment 1 measured individual length growth (GR), weight‐specific growth (SGR), growth efficiency, and lipid content at constant food levels and three static temperatures (6, 12, 19°C), resulting in decreasing GR from 0.24 mm/day at 19°C (SGR = 0.89%/day) to 0.15 mm/day at 12°C (0.54%/day) to 0.04 mm/day at 6°C (0.17%/day). Even at the coldest temperature, most juveniles sustained positive GRs and SGRs; hence, the species' true thermal growth minimum may be below 6°C. Lipid accumulation was greatest at 12°C, which is close to what overwintering juveniles likely encounter offshore. Experiment 2 measured the same traits but combined a representative thermal overwinter profile (20°C → 13°C, October–March) with seasonally varying rations designed to mimic low and high levels of food availability offshore. Monthly GR and SGR responded in the direction of seasonal food level changes. The “winter pulse” consumption average of 1.7%/feeding elicited a mean GR of 0.15 mm/day and SGR of 0.55%/day, whereas the “winter dip” consumption average of 3.8%/feeding yielded faster GR (0.20 mm/day) and SGR (0.71%/day). Growth efficiency ranged between 15% and 30% and was inversely related to food consumption. In both experiments, juveniles disproportionally accumulated lipid over lean mass, with lipid proportions tripling in experiment 2 from 4% at 65 mm to 12% at 120 mm.ConclusionAs inshore winter waters continue to warm, the energetic trade‐offs of overwinter offshore migration are likely to shift, potentially leading to a year‐round inshore Black Sea Bass presence.

The supercooling point depression is the leading cold tolerance strategy for the variegated ladybug, [Hippodamia variegata (Goezel)

The variegated ladybug, Hippodamia variegata is one of the most effective predators of various pests that hibernate as adult beetles. During the overwintering period from April 2021 to March 2022, we examined the supercooling point (SCP), cold tolerance, and physiological adaptations of beetles in Kerman, Iran. The beetles exhibited their greatest cold tolerance (63.4% after 24h at -5°C) when their SCP was lowest (-23.2°C). Conversely, from April to October 2021, the SCP reached its peak (approximately -13.0°C), while cold tolerance was at its lowest level (6.7% after 24h at -5°C). Cryoprotectant content (trehalose, glycerol, and glucose) was at its highest level in September (11.15, 10.82, and 6.31mg/g, respectively). The critical thermal minimum (CTmin) reached its lowest point of -2.2°C in January and February. The lowest point of the lower lethal temperature (LLT) coincided with the lowest level of the SCP and the highest level of cold tolerance (in February, LT50 = -5.3°C, SCP = -23.2°C, and survival = 77.78% at -4°C/24h). Chill-coma recovery time (CCRT) was examined at five different temperatures and two different exposure durations. The CCRT increased with a decrease in exposure temperature and time (68.0s at -2°C after 2h and 102.0s at -2°C after 4h). As the majority of the overwintering beetle's mortality occurred at temperatures significantly higher than SCP, the adults of H. variegata are chill-susceptible insects that primarily rely on a depressed supercooling point to cope with unfavorable conditions during the overwintering period.

Zircon and cassiterite U-Pb geochronology and petrochemical characteristics of early Tertiary tin mineralization at Mayo Darlé, Cameroon Volcanic Line

Tin mineralization at Mayo-Darlé in the Cameroon Volcanic Line is associated with highly evolved anorogenic ferroan granite magmatism with a pervasive hydrothermal overprint. Mineralization occurs as cassiterite-quartz-muscovite stockwork and disseminated in quartz-mica and quartz-topaz greisen in low-Ca alkali feldspar granite with a composition near the 1 kbar haplogranitic thermal minimum. The trace element composition of zircon indicates elevated temperature (880 ± 55 °C) and very low oxidation state below the quartz-fayalite-magnetite buffer. Laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) identifies a partly disturbed U-Pb system for igneous zircon (U and Th contents >1000 ppm) but defines Tera-Wasserburg concordia ages and common-lead-corrected weighted 206Pb/238U ages of about 54 Ma, similar to a previous 87Rb/86Sr vs 87Sr/86Sr regression with a date of 56.1 ± 1.7 Ma (MSWD = 58; n = 9) and an initial 87Sr/86Sr ratio of 0.7085 ± 0.0035 (2 s). Hydrothermal cassiterite gives a pooled LA-ICPMS Tera-Wasserburg concordia age of 56.7 ± 0.6 Ma on two samples (each about 20 points, MSWD = 0.54 and 1.3). These new age data define a period of early Cenozoic intraplate calc-alkalic felsic magmatism as a precursor to abundant Oligocene to Recent alkali basalt volcanism along the Cameroon Volcanic Line. Geochemical and Sr–Nd–Hf isotopic data suggest that the granitic rocks from Mayo Darlé were largely derived by partial melting of Mesoproterozoic basement and modified by strong differentiation, all likely powered by heat (and possibly fluids) from the mantle. The Tertiary age of the rare-metal magmatism sets this system apart from the widespread Late Neoproterozoic to Early Paleozoic rare-metal pegmatites and granites in the Pan-African collisional belts of Africa, and also from the anorogenic Mesozoic ring complexes in Central Nigeria.

Multigrid method for the solution of thermal elastohydrodynamic lubrication point contact problem with surface asperities

The paper presents, the numerical investigation of point contact thermal elasto-hydrodynamic lubrication (EHL) with surface asperities are analyzed. The effect of temperature and surface roughness on fluid film thickness is studied in detail. The governing equations comprises Reynolds, film thickness, load balance and energy equations with appropriate boundary conditions. The second order finite difference approximation is used to discretize the governing equations and the resultant nonlinear system of algebraic equations is solved using Multigrid V-cycle with full approximation scheme (FAS) technique. Multi level multi integration (MLMI) technique is employed to solve the film thickness equation. The obtained results are illustrated in the form of graphs and tables which are comparable with earlier findings. The film thickness profiles shows dimple near to the outlet region due to temperature-viscosity wedge mechanism. Isothermal minimum film thickness is higher than the thermal minimum film thickness. Minimum film thickness is much smaller due to slide to roll ratio is positive ascompared to negative, whereas the behavior of central film thickness is contrast as that of minimum film thickness.

A neurophysiological limit and its biogeographic correlations: Cold-induced spreading depolarization in tropical butterflies.

The physiology of insects is directly influenced by environmental temperature, and thermal tolerance is therefore intrinsically linked to their thermal niche and distribution. Understanding the mechanisms that limit insect thermal tolerance is crucial to predicting biogeography and range shifts. Recent studies on locusts and flies suggest that the critical thermal minimum (CTmin) follows from a loss of CNS function via a spreading depolarization. We hypothesized that other insect taxa share this phenomenon. Here we investigate whether spreading depolarization events occur in butterflies exposed to cold. Supporting our hypothesis, we find that exposure to stressful cold induced spreading depolarization in all 12 species tested. This reinforces the idea that spreading depolarization is a common mechanism underlying the insect CTmin. Furthermore, our results highlight how CNS function is tuned to match species' environments. Further research into the physiology underlying spreading depolarization will likely elucidate key mechanisms determining insect thermal tolerance and ecology.