Differences between air and ground temperatures are expected to narrow with the advance of the season in temperate regions (aka seasonal restriction in the availability of thermal microhabitats), ...which may activate behavioral and physiological responses of ectotherm species adapted to temperate climates. However, according to cost-benefit models of ectotherm thermoregulation, we hypothesize that these responses may also carry some costs. We quantified seasonal shifts in thermoregulatory precision, concentration of fecal glucocorticoid metabolites, and load of ectoparasites in a Mediterranean lizard, Psammodromus algirus. We also tested whether the proximity to a road, a putative source of chronic stress, can facilitate the glucocorticoid-mediated response of lizards to heat stress. As expected, differences between body and environmental temperatures narrowed during the reproductive season and lizards responded by increasing their thermoregulatory precision and the secretion of glucocorticoids, as indicated by metabolites in feces. Interestingly, lizards tended to have higher glucocorticoid concentration when captured far from the road. This might reflect either a putative impairment of the glucocorticoid-mediated response of the lizards to heat stress close to the road or the plastic capability of P. algirus to acclimate to sources of moderate chronic stress. In the latter direction, the increase of both glucocorticoid metabolites and thermoregulatory precision supported that this Mediterranean species responds to environmental thermal restrictions with adaptive behavioral and physiological mechanisms. However, this was also associated with an increase in its susceptibility to ectoparasites, which represents an added cost to the current cost-benefit models of ectotherm thermoregulation.
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•Climate may impose thermal restrictions to ectotherms in Mediterranean habitats.•Lizards increased thermoregulatory activity and glucocorticoids under heat stress.•Coping responses were not influenced by the distance to a road.•Seasonal increase of ectoparasites was explained by thermal restrictions.
Porous silicon nanostructures have attracted a great deal of interest during the past few years, due to their many remarkable properties. The high-efficiency visible photo- and electro-luminescence ...of this material opened the way to the development of silicon-based optoelectronic devices fully compatible with standard industry processes. In addition to these luminescent properties, nanostructured porous silicon shows a variety of other interesting properties, including tunable refractive index, low light absorption in the visible, high internal surface, variable surface chemistry, or high chemical reactivity. All these properties, along with its ease of fabrication and the possibility of producing precisely controlled layered structures make this material adequate for its use in a wide range of fields, such as optics, micro- and optoelectronics, chemical sensing or biomedical applications, for example. This article reviews the applications of nanostructured porous silicon that exploit its unique optical properties, as in the case of light emitting devices, filtered photodetectors, optical sensors, and others.
Barium titanate is one of the most studied perovskite materials owing to its ability to the substitution in both sites, to its high dielectric constant and to its stability. It is characterized by a ...diversity of remarkable properties, especially ferroelectric and dielectric properties, which can be improved by doping, making this material suitable for many applications. We have investigated the effect of calcium ion substitution on the structural, optical, electrical and dielectric properties of this compound. Ba0.9Ca0.1TiO3 ceramic was elaborated using the solid-state diffusion method. This compound crystallized in the tetragonal phase with a crystallite size of 22 nm. Fourier transform infrared spectroscopy measurements revealed that octahedral vibrations are affected by Ca incorporation. Electrical analyses show that the compound has a semiconductor behavior, and that both grains and grain boundaries are responsible for the thermal evolution of the conduction mechanisms. Two different transition temperatures were detected. One of them coincides with the Curie temperature, which is confirmed by dielectric measurements. The compound shows a high dielectric constant up to 420 K which is seemingly constant in a wide frequency range. Such behavior is sought for the development of energy storage devices.
•Ba0.9Ca0.1TiO3 is prepared by the solid state reaction method.•The effect of Ca incorporation in Ba site on structural properties is elucidated.•Calcium incorporation affects the band gap and FTIR and Raman spectra.•Both grains and grain boundaries contribute in the electrical conduction process.•A ferroelectric-paraelectric transition is evidenced from the variation of the dielectric constant with temperature.
One of the most characteristic and abundant amphibian taxa of South American temperate forests is Eupsophus. The ten currently recognized species of the genus have been divided in two species groups, ...roseus and vertebralis, but most of them, eight, belong to the roseus group. Recent phylogeographic and phylogenetic studies have suggested that species diversity of the roseus group could be underestimated. An examination of the literature shows that species of the roseus group exhibit high levels of variation in their external characteristics, particularly those used as diagnostic characters, which compromises their taxonomy and hinders their field recognition. High levels of variation were also observed in several new populations of the roseus group discovered in southern Chile (36°-40°S), which could not be identified to the species level by their external characteristics. On the other hand, the literature reveals a scarse karyotype differentiation and a high bioacoustic uniformity among the species of the roseus group. We performed a Bayesian phylogenetic analysis using mitochondrial and nuclear genes to reevaluate the species diversity of the roseus group, including all the nominal species of Eupsophus and new populations. This analysis was complemented with three species delimitation approaches, General Mixed Yule Coalescent, multi-rate Poisson Tree Process and Automatic Barcode Gap Discovery. We favored a conservative delimitation of only four species for the roseus group, a result more consistent with the distribution of pairwise genetic distances, and the available chromosome and bioacoustic evidence. The four recognized lineages, which have nearly completely allopatric distributions, are named after the earliest nominal species that they include, but because high levels of phenotypic variation, they are not diagnosable by consistent differences in external morphology. We discuss the implications of this new proposal for the taxonomy and conservation of the genus, and the possible causes of the difficulty to estimate its species diversity.
Anthropization of insular ecosystems may have negative impacts on native populations of lizards, which provide core ecosystem services on islands. We aimed to identify environmental factors to ...explain the interlocal variation in faecal glucocorticoids, parasite intensity, and body condition in populations of insular lizards. A cross-sectional design during the summer of 2017 and 2018 was used to sample 611 adult lizards, Gallotia galloti. Interlocal variation of three stress indicators was analysed in response to environmental variables across a wide environmental gradient in Tenerife (Canary Islands): (i) concentration of faecal glucocorticoids, (ii) intensities of infection by hematic parasites, and (iii) body condition. The data, with low spatial autocorrelation, were analysed using multimodel inference and model cross-validation. Bioclimatic variables associated with the extreme hot and dry climate of summer were the most informative predictors. Interlocal variation in faecal corticosterone in males was best fitted to a model that included the maximum temperature of the warmest month, although the best predictor was habitat anthropization. The thermal annual range, associated with extreme thermal events, was positively related to faecal corticosterone in females. Extreme hot temperatures were positively related to the median parasite intensities in both sexes, while the highest mean intensities of infection were found in females from the most xeric coastal localities. None of the predictors tested, including faecal glucocorticoids, explained individual or interlocal variation in body condition. Effects of human pressure and climate change on insular populations of lizards can be additive. However, the uncoupled relationship found between body condition and the faecal glucocorticoid content suggests that current negative effects may be aggravated during drought periods in summer. Given the impact of climate change on islands, our results may be of application to other archipelagos, where lizards also play key ecological roles.
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•The impact of anthropization on insular lizards is scarcely known.•Three health/stress indicators were analysed along an environmental gradient.•Corticosterone and hematic parasites co-vary with human development and climate.•Environmental impacts are different for males and females.•Monitoring lizard populations in islands may allow anticipating cascading effects.
Reactive oxygen species (ROS) are now widely recognized as central mediators of cell signaling. Mitochondria are major sources of ROS.
It is now clear that mitochondrial ROS are essential to activate ...responses to cellular microenvironmental stressors. Mediators of these responses reside in large part in the cytosol.
The primary form of ROS produced by mitochondria is the superoxide radical anion. As a charged radical anion, superoxide is restricted in its capacity to diffuse and convey redox messages outside of mitochondria. In addition, superoxide is a reductant and not particularly efficient at oxidizing targets. Because there are many opportunities for superoxide to be neutralized in mitochondria, it is not completely clear how redox cues generated in mitochondria are converted into diffusible signals that produce transient oxidative modifications in the cytosol or nucleus.
To efficiently intervene at the level of cellular redox signaling, it seems that understanding how the generation of superoxide radicals in mitochondria is coupled with the propagation of redox messages is essential. We propose that mitochondrial superoxide dismutase (SOD2) is a major system converting diffusion-restricted superoxide radicals derived from the electron transport chain into highly diffusible hydrogen peroxide (H
O
). This enables the coupling of metabolic changes resulting in increased superoxide to the production of H
O
, a diffusible secondary messenger. As such, to determine whether there are other systems coupling metabolic changes to redox messaging in mitochondria as well as how these systems are regulated is essential.
The precise control over the interaction between cells and the surface of materials plays a crucial role in optimizing the integration of implanted biomaterials. In this regard, material surface with ...controlled topographic features at the micro- and nano-scales has been proved to affect the overall cell behavior and therefore the final osseointegration of implants. Within this context, femtosecond (fs) laser micro/nano machining technology was used in this work to modify the surface structure of stainless steel aiming at controlling cell adhesion and migration. The experimental results show that cells tend to attach and preferentially align to the laser-induced nanopatterns oriented in a specific direction. Accordingly, the laser-based fabrication method here described constitutes a simple, clean, and scalable technique which allows a precise control of the surface nano-patterning process and, subsequently, enables the control of cell adhesion, migration, and polarization. Moreover, since our surface-patterning approach does not involve any chemical treatments and is performed in a single step process, it could in principle be applied to most metallic materials.
Body size is a key organismal trait. However, the environmental and evolutionary factors that drive body size patterns at the interspecific level remain unclear. Here, we explored these relationships ...between phenotype-environment using neotropical frogs of Pristimantis, the world's most diverse vertebrate genus. We analyzed: (a) whether this group follows the Rensch's rule, a trend of sexual size dimorphism (SSD) to increase with size when males are the larger sex; (b) whether environmental constraints have influenced body size variation; and (c) how the rates of body size evolution have varied over time. Analyses were based on two information sources, the first one including body sizes of ~ 85% (495 species) of known species in the genus, and a second one incorporating molecular phylogenetic information for 257 species. Our results showed that all Pristimantis species exhibited marked SSD but did not follow Rensch's rule. We found that the models that best explained body size in males, females, and SSD contained environmental variations in temperature, precipitation, and elevation as predictors. In turn, body size has evolved toward an optimum, with a decelerating rate of evolution differentiated between the large Pristimantis clades.
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