Search Results (133)

Yersinia pestis is the causative agent of bubonic plague, a zoonotic disease that is primarily transmitted by infectious fleas. Plague is endemic in regions around the world, including the United States, where optimal climate conditions support a stable, enzootic sylvatic transmission cycle. Epizootic outbreaks periodically occur with rapid spread of disease that increases the risk of human exposure. As fleas are ectotherms that are responsive to environmental conditions, it is likely that transmission efficiency varies under different ecological conditions, with optimal conditions capable of supporting rapid spread of disease while sub-optimal conditions may promote lower levels of transmission. To test this, we experimentally infected Xenopsylla cheopis with Y. pestis using a membrane feeder in order to define the impact of varying temperature, humidity and mammalian blood sources on infection and transmission. We show that environmental factors and host blood source are key factors influencing colonization, bacterial aggregation, and transmission rates, with variation in the responses seen depending on the experimental conditions. The combined data illustrate the impact of ecological factors on Y. pestis flea infection and suggests that optimal conditions involving the vector–host–pathogen interface are needed for enhanced transmission rates and the rapid spread of infection that occurs during epizootic outbreaks. Full article

Background/Objectives: Cardiac regenerative ability varies in vertebrates. Adult mammals cannot mount a regenerative response, while fetal mammals and some salamanders and teleosts fully regenerate the heart after a cryoinjury mimicking a myocardial infarction. This contrast is suggested to be regulated in part by metabolism, with high regenerative capacity correlating with a comparatively lower mass-specific metabolic rate, ectothermy rather than endothermy and a metabolic phenotype favoring glycolysis in cardiac muscle. Methods: In this physiological study on axolotl salamanders, we altered the housing temperatures from the standard 20 °C to 10 °C, 25 °C and 30 °C and assayed key metabolic parameters as well as cardiac function, survival and regenerative capacity. Results: Our study demonstrated that while axolotls could be housed at temperatures ranging from 10 °C to 30 °C in an uninjured state, signs of a pathological response involving cardiac and metabolic insufficiency and mortality, especially after cryoinjury, increased progressively with increasing temperatures. We observed several metabolic effects, including differences in oxygen consumption, plasma metabolites and cardiac function. Cardiac regeneration after cryoinjury progressed as expected with only a small remaining injury after 60 days at the standard housing temperature of 20 °C. Regeneration was highly reduced in a reversible manner at 10 °C while regenerative rate was not affected at 25 °C. At 30 °C, cardiac regeneration could not be evaluated as the majority of animals (five out of six) did not survive the injury, likely reflecting insufficient cardiac reserve capacity to simultaneously sustain thermal metabolic effects and support tissue repair. Conclusions: The ectothermic axolotl undergoes several metabolic changes when exposed to different housing temperatures, with heart regeneration showing a narrower permissive temperature range than survival of the axolotl in an uninjured state. Full article

Sungaya inexpectata is a tropical stick insect endemic to the Philippines, providing a useful system for investigating cold responses in tropical ectotherms. In this study, we exposed individuals to low temperature (8 °C) and normal temperature (25 °C) and characterized their transcriptomic responses. A total of 1656 differentially expressed genes were identified, including those involved in energy metabolism, cuticular proteins (CPs), and heat shock proteins. Since CP-related genes were notably enriched, we focused on this family. qPCR assessment provided preliminary expression profiles for selected candidate CP genes. Using comparative transcriptomics with eight New Zealand alpine stick insect species, we reconstructed the phylogeny of major CP families and annotated their conserved domains. Clade analysis revealed significant positive selection in the CPAP3-3 gene. In summary, this study reveals the transcriptional response of cuticular protein genes in S. inexpectata under cold exposure at 8 °C. These findings provide preliminary transcriptional data for understanding how this species responds to low temperature. Full article

Global warming is reshaping the climatic suitability of invasive ectotherms. In this study, we used an optimized Maximum Entropy (MaxEnt) model combined with GIS-based centroid tracking to quantify the spatiotemporal changes in the potential climatic suitability of Zeugodacus tau, a major polyphagous quarantine pest, in China. Projections were conducted under the historical baseline climate (1970–2000) and future climate scenarios, including SSP1–2.6, SSP2–4.5, and SSP5–8.5 for the 2050s and 2070s. Here, we projected potential climatic suitability rather than future occurrence or abundance. The model showed high predictive performance (AUC = 0.921). Annual mean temperature (Bio1) and mean diurnal range (Bio2) were identified as the primary environmental variables shaping the species’ climatic suitability. Future projections suggested contrasting spatial changes in climatic suitability, with expansion mainly in northern marginal regions and contraction of the southern highly suitable core area. As winter temperatures increased, the low- and moderate-suitability areas were projected to expand northward into temperate agricultural regions. However, under the extreme warming scenario (SSP5–8.5), the highly suitable core area in southern China was projected to decline by 31.61%, while the centroid of the highly suitable area shifted inland and northwestward by approximately 168 km toward the Wuling Mountains. These spatial patterns may be associated with increasing summer heat stress in low-altitude southern regions, although this mechanism requires further physiological validation. Overall, these findings provide a scientific basis for risk-oriented early warning, quarantine planning, and region-specific pest management under future climate change. Full article

The knowledge base for many small vertebrate species remains limited, largely because traditional manual data collection methods often overlook less charismatic species, such as reptiles. To address this, our pilot study harnesses open-source deep learning and markerless pose estimation technologies to evaluate the technical feasibility of tracking the spatial use and activity profiles of captive ectotherms. Specifically, we tracked these patterns over two months in a dynamically modified environment for Australian barking geckos (Underwoodisaurus milii). Our findings reveal descriptive changes in spatial occupancy and proximity across varying structural layouts. The system achieved a high raw detection accuracy (96.4%) and spatial categorization accuracy (91.7%) when validated against manual ground-truth data, confirming its robust technical performance and precision. Additionally, we automatically evaluated spatial proxies such as activity time budget, velocity, acceleration, and height usage, standardizing the analysis of extensive video recordings for nocturnal species. This pilot test introduces a simple, cost-effective method for rapid data extraction, offering a reliable, scalable monitoring solution for the management of understudied species. Full article

Ambient temperature strongly influences the physiology and performance of ectotherms, making it essential to understand their responses to thermal variation under climate change. We evaluated locomotor performance and thermal vulnerability in a population of Phymaturus williamsi from the Argentine Andes. Field measurements included body (T_b) and operative temperatures (T_e), while laboratory analyses assessed preferred temperature (T_pref), thermoregulatory effectiveness, critical thermal limits, and thermal sensitivity of locomotion (endurance, sprint, and long runs). P. williamsi exhibited a preferred temperature higher than field body temperatures, together with high thermoregulatory effectiveness (E = 0.83) and a broad thermal tolerance range (TT = 35.41 °C). Optimal temperatures for locomotor performance were lower than T_pref, providing no support for the thermal coadaptation hypothesis. Despite low environmental thermal quality, individuals maintained body temperatures close to performance optima through effective behavioral thermoregulation. Thermal vulnerability indices indicated relatively high tolerance to projected warming scenarios. However, our results suggest that vulnerability to climate change is constrained more by the availability of suitable thermal microhabitats than by intrinsic physiological limits. We conclude that P. williamsi is a eurythermic and effective thermoregulator with thermally sensitive locomotor performance, whose persistence will depend on habitat structure and thermal heterogeneity. Full article

Body temperature regulation in ectotherms is influenced by numerous environmental, morphological, and physiological factors, some of which operate in population-specific ways. Understanding how these factors shape thermal biology is important for species conservation. The nose-horned viper, an ecologically significant yet understudied mesopredator of southeastern Europe and Asia Minor, occupies diverse ecosystems facing ongoing degradation. Over five years, we investigated how 12 environmental, behavioral, morphological, and physiological variables influenced field body temperature across three climatically distinct populations of nose-horned vipers. Using an information-theoretic approach with model averaging, we identified important predictors and assessed population-specific effects. Air temperature at 5 cm above the snake’s position, humidity, and wind were highly important predictors across all populations, whereas physiological states (shedding and digestion) exerted weaker effects. Microhabitat type and time of day emerged as highly important population-specific predictors, while body size showed weaker, population-dependent effects. Neither sex, cloud cover, nor behavioral state contributed meaningfully to model fit. Mean body temperatures were similar across populations and sexes. By integrating environmental, behavioral, physiological, and morphological variables, this study comprehensively identifies predictors of body temperature in nose-horned vipers. Site-tailored maintenance of structurally diverse habitats is essential for preserving thermoregulatory opportunities and ensuring long-term persistence of nose-horned vipers. Full article

Climatic niche breadth is defined as the range of climatic conditions (e.g., temperature and precipitation) under which a species occurs. However, the relationship between niche breadth variation and climatic factors remains poorly studied, and existing results require more general testing. We studied spatial patterns of variation in climatic niche breadths in lizards of the family Agamidae and compared patterns within and across regions to see if they parallel or differ from each other using geo-referenced occurrence records, climatic data and phylogenetic comparative methods. We found that (1) species in warmer environments have narrower temperature niche breadths; (2) precipitation niche breadths are positively correlated with precipitation niche position, and also with temperature niche breadths; and (3) most of the variation in temperature niche breadths is explained by within-locality variation in climatic conditions, whereas most of the variation in precipitation niche breadths is explained by among-locality variation. The patterns of climatic niche breadth in agamids are consistent across regional and global scales, similar to those in other amphibians and reptiles. This suggests that this is a widespread phenomenon among ectothermic vertebrates. Full article

Climate warming can alter reproductive timing of species, yet the capacity for phenological adjustment in long-lived species, particularly marine ones, remains elusive. Using 17 years of monitoring data from one of the largest loggerhead turtle (Caretta caretta) populations, we investigated the environmental drivers of reproductive phenology and output. We found that warmer sea surface temperatures (SST) in both the feeding ground and the nesting ground advanced the start, peak, and end of the nesting season. We provide evidence for waves of arrival at the nesting ground, suggesting more turtles produce fewer clutches than previously thought. Inter-nesting intervals were shorter during episodes of higher SST, particularly in larger females, likely underpinned by metabolic scaling variation in reproductive pacing. Conversely, remigration intervals lengthened over time in all size classes, reflecting the detected continuous decrease in productivity in the feeding ground. As a result of reduced ocean productivity, both clutch size and clutch frequency also declined over the study period. Moreover, the declining trend in body size further reduces reproductive output, as smaller females produce smaller clutch sizes. Overall, we show that sea turtle population dynamics correlate with environmental parameters. The sustained decline in reproductive output underscores the need to mitigate the impacts of climate warming on the foraging area to safeguard this population, which, given its size, holds global significance. Full article

The ecology and establishment of Aedes aegypti in tropical, sub-tropical, and temperate areas makes them one of the most medically relevant mosquito species. While they have been reported to be highly anthropophilic, several studies indicate a broader host range. They also reportedly take multiple blood meals between gonotrophic cycles, which makes determination of host usage difficult when using common blood meal analysis methods. In this study, we examined host usage of Ae. aegypti in Harris County, Texas (Houston), and Maricopa County, Arizona (Phoenix), using a nanopore-based third-generation sequencing protocol to resolve host usage and multiplicity. Using this method, approximately 80% of samples from each location with evidence of blood feeding resulted in blood meal identification, with a single host blood meal identified in about 80% of samples and approximately 20% containing evidence of multiple blood meals. Overall, we observed a wide host range with human DNA being the most prevalent followed by feline (Felis catus) and canine (Canis lupus). We also identified avian, rodent, ungulate and even ectotherm usage by Ae. aegypti from Maricopa County. This study demonstrates the utility of a third-generation sequencing method to identify less common hosts, like ectotherms in Arizona, and to resolve multiple feedings which remain difficult to resolve by current Sanger-based methods. Full article

Temperature is a critical abiotic factor regulating the physiology, growth, and reproduction of ectothermic aquatic animals. In China, the rapid expansion of the red swamp crayfish Procambarus clarkii) industry faces significant challenges due to seasonal temperature fluctuations (optimal growth at 20–25 °C and reproduction favored at 18–22 °C). This review focuses specifically on TRP channels, particularly TRPA1 as a key thermosensor in crayfish, and on downstream signaling pathways involving heat shock proteins (HSPs) and antioxidant defenses. We further link these biological mechanisms to aquaculture applications by evaluating best management practices for mitigating thermal stress, including integrated rice–crayfish co-culture, recirculating aquaculture systems (RAS), molecular marker-assisted breeding for thermal tolerance, and nutritional modulation (e.g., probiotics and immunostimulants). By maintaining thermal stability within the optimal range and directly enhancing physiological resilience through genetic and nutritional interventions, these practices provide a foundation for more sustainable and climate-resilient crayfish aquaculture. Full article

Ambient temperature plays a crucial role in shaping the skin color of some lizard species. While the long-term correlation between ambient temperature and skin color changes in lizards has been well-studied, how they adjust skin color and body temperature in response to short-term thermal fluctuations remains unclear. In this study, we examined the impacts of ambient temperature on the body temperature and skin color of Anolis carolinensis. In a white background, as the ambient temperature rose from 20 °C to 40 °C, both body surface and core temperatures increased; skin brightness rose from 71.47 to 88.05 cd/m², chroma decreased from 43.55% to 36.43%, and hue dropped from 95.80° to 78.82°. Their changes against a brown background were similar to those against a white background. Correlation analysis showed that brightness was positively correlated with body temperature, chromaticity was negatively correlated with it, and hue negatively correlated with body temperature in white backgrounds but showed no significant correlation in brown backgrounds. As the ambient temperature rose from 20 °C to 40 °C, the spectral reflectance of skin in the visible (300–700 nm) and near-infrared (700–2500 nm) range increased from 26.01 ± 0.57% to 30.22 ± 0.63% and 8.61 ± 1.20% to 11.71 ± 1.48%, respectively. These results demonstrate that the skin color and spectral reflectance variations in A. carolinensis play a role in body temperature regulation. Additionally, this study offers new insights into the adaptive strategies of ectothermic organisms in balancing skin color and body temperature in fluctuating ambient temperatures. Full article

Temperature strongly influences physiological processes in ectotherms, including digestion, yet its effects on digestive enzyme activity remain poorly understood. We examined the temperature dependence of digestive performance in eight Mediterranean wall lizard species (Podarcis spp.) from mainland and island populations. Under controlled laboratory conditions, we measured the activity of three key enzymes, protease, lipase, and maltase, across a temperature gradient (20–55 °C), alongside gastrointestinal (GI) morphology. Enzyme activity generally increased with temperature up to 50 °C and declined thereafter, reflecting typical thermal kinetics. Lipase activity was consistently higher in island species, while protease and maltase showed no significant geographic or phylogenetic trends. Island lizards also exhibited longer and heavier GI tracts relative to body size (SVL), suggesting enhanced nutrient absorption capacity. Phylogenetic signal analyses (Pagel’s λ and Abouheif’s C_mean) revealed no significant evolutionary constraints on digestive traits, indicating that observed differences reflect ecological adaptation rather than ancestry. Overall, island species appear to have evolved digestive traits that improve energy extraction under resource-limited conditions, but may be more sensitive to extreme heat. These findings highlight contrasting adaptive strategies between island and mainland reptiles and underscore the importance of digestive physiology in predicting the response of species to warming climates. Full article

The environmental behavior of biodegradable plastics under long-term hydrodynamic aging processes in seawater remains poorly understood, although plastic pollution has attracted global concern. This study obtained poly(butylene adipate-co-terephthalate) (PBAT) and poly(butylene succinate) (PBS) microplastics that endured 36-month hydrodynamic aging in seawater to elucidate their physicochemical transformations and interactions with benzo(a)pyrene (BaP). Hydrodynamic aging markedly altered surface morphology, generated cracks and pores, and enriched -C=O and -OH groups, indicating oxidative degradation. Adsorption experiments showed that BaP adsorption capacity of virgin PBAT/PBS reached 213.3/235.3 μg g⁻¹, while it increased to 233.3/258.2 μg g⁻¹ after hydrodynamic aging in seawater. Elevated salinity and alkaline conditions reduced BaP adsorption on microplastics. Notably, hydrodynamic aging mitigated the risk of BaP desorption from PBAT in ectothermic organisms. Gibbs free energy calculations indicated that the adsorption process was primarily driven by hydrophobic effects, hydrogen bonding, and van der Waals forces. These findings highlight that long-term hydrodynamic aging substantially modifies the interfacial properties of biodegradable plastics to alter their capacity for mediating the environmental fate of hydrophobic organic pollutants in marine ecosystems. Full article

The fluctuating temperature poses challenges to the survival of amphibians. This study employed two cold-adapted brown frog species, Rana dybowskii and Rana amurensis, from high-latitude cold regions as research models. We explored the mechanism by which contrasting peak daily habitat temperatures affect their physiological function and symbiotic microbial community. The results indicate that these two cold-adapted brown frog species exhibit a common physiological response of enhanced immune capacity and suppressed antioxidant capacity when subjected to elevated temperatures. However, they demonstrate unique coping strategies and physiological regulatory effects on gut microbiota: R. dybowskii activates its immune system by reducing the abundance of Actinobacteria and inhibiting metabolic pathways, but the decrease in Bacteroidetes abundance impairs antioxidant efficacy. On the other hand, R. amurensis experiences impairment of antioxidant function due to the regulatory effects of a significant increase in Proteobacteria and Actinobacteria, a marked decrease in Bifidobacterium, and a decline in gut microbiota α-diversity. For the first time, this study reveals the adaptive mechanisms by which two cold-adapted amphibian species respond to the contrasting peak daily habitat temperatures, providing a scientific basis for understanding how ectotherms react to climate change and for predicting their population dynamics. Full article