EFFECTS OF SEX, ENVIRONMENT, AND CONDITION ON THE MUSKING BEHAVIOR OF SYMPATRIC GARTERSNAKES (THAMNOPHIS SPP.)

Despite an abundance of studies documenting antipredator and defensive behaviors of gartersnakes (genus Thamnophis), few have quantitatively examined musking, a widely utilized antipredator tactic. In this study we quantify musking behaviors in the Terrestrial Gartersnake (Thamnophis elegans) and the Plains Gartersnake (T. radix) when hand-captured at four sites in and near Denver, Colorado, USA. Overall, Plains Gartersnakes musked significantly more often than Terrestrial Gartersnakes. Female Terrestrial Gartersnakes musked more frequently than males, a pattern not evident in the Plains Gartersnake. Additionally, we observed a positive correlation in body condition and musking propensity in Terrestrial Gartersnakes, suggesting resource-dependent behavior in this species. Musking behavior was consistent across variations in predation pressure, environmental conditions, and snake body size, all factors shown to influence other gartersnake defensive behaviors. These results corroborate other research which demonstrates that snake antipredator behaviors are determined by complex interactions of abiotic and biotic factors

Study of electron field emission from arrays of multi-walled carbon nanotubes synthesized by hot-wire dc plasma-enhanced chemical vapor deposition

International audienceMulti-walled carbon nanotubes have been grown on 7 nm Ni-coated substrates consisting of 300 lm thick highly n-doped (1 0 0) sil- icon covered with a diffusion barrier layer (10 nm thick) of SiO2 or TiN, by combining hot-wire chemical vapor deposition and direct current plasma-enhanced chemical vapor deposition at low temperature (around 620 °C). Acetylene gas was used as carbon source and ammonia and hydrogen were used either for dilution or etching. Growth of dense aligned nanotubes could be observed only if the ammonia content was minimized (rv5%). In order to improve the electron field emission properties of the films, different geometrical factors have been taken into account: average length, length/radius ratio and spacing between nanotubes. The nanotube growth rate was controlled by the substrate temperature and the pressure in the reactor, and the nanotube height by the growth time. The nanotube diam- eter was controlled by the catalyst dot volume, and the nanotube spacing was adjusted during the patterning process of the catalyst dots. Using optical lithography, 1 lm Ni dots were obtained and several multi-walled nanotubes with diameter and length in the range 60- 120 nm and rv2.3 lm were grown on each dot. Thus, based on a two-dimensional square lattice with a lattice translation vector of 4 lm, I-V characteristics yielded an onset electric field of 16 V/lm and a maximum emission current density of 40 mA/cm2, due to the large screening effect. Using electron-beam lithography, 100 nm Ni dots were obtained and individual multi-walled nanotubes were grown on each dot. Based on a square lattice with 10 lm translation vector, I-V characteristics gave an onset field of 8 V/lm and a max- imum emission current density of 0.4 A/cm2

Merging the “Morphology–Performance–Fitness” Paradigm and Life-History Theory in the Eagle Lake Garter Snake Research Project

The morphology-performance-fitness paradigm for testing selection on morphological traits has seen decades of successful application. At the same time, life-history approaches using matrix methods and perturbation studies have also allowed the direct estimate of selection acting on vital rates and the traits that comprise them. Both methodologies have been successfully applied to the garter snakes of the long-term Eagle Lake research project to reveal selection on morphology, such as color pattern, number of vertebrae, and gape size; and life-history traits such as birth size, growth rates, and juvenile survival. Here we conduct a reciprocal transplant study in a common laboratory environment to study selection on morphology and life-history. To place our results in the ecomorphology paradigm, we measure performance outcomes (feeding rates, growth, insulin-like growth factor 1 titers) of morphological variation (body size, condition) and their fitness consequences for juvenile survival?a trait that has large fitness sensitivities in these garter snake populations, and therefore is thought to be subject to strong selection. To better merge these two complementary theories, we end by discussing our findings in a nexus of morphology-performance-fitness-life history to highlight what these approaches, when combined, can reveal about selection in the wild.Fil: Addis, Elizabeth A.. University of Iowa; Estados UnidosFil: Gangloff, Eric J.. University of Iowa; Estados UnidosFil: Palacios, María Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina. University of Iowa; Estados UnidosFil: Carr, Katherine E.. Gonzaga University; Estados UnidosFil: Bronikowski, Anne M.. University of Iowa; Estados Unido

From performance curves to performance surfaces: Interactive effects of temperature and oxygen availability on aerobic and anaerobic performance in the common wall lizard

Accurately predicting the responses of organisms to novel or changing environments requires the development of ecologically-appropriate experimental methodology and process-based models. For ectotherms, thermal performance curves (TPCs) have provided a useful framework to describe how organismal performance is dependent on temperature. However, this approach often lacks a mechanistic underpinning, which limits our ability to use TPCs predictively. Furthermore, thermal dependence varies across traits, and performance is also limited by additional abiotic factors, such as oxygen availability. We test a central prediction of our recent Hierarchical Mechanisms of Thermal Limitation (HMTL) Hypothesis which proposes that natural hypoxia exposure will reduce maximal performance and cause the TPC for whole-organism performance to become more symmetrical. We quantified TPCs for two traits often used as fitness proxies, sprint speed and aerobic scope, in lizards under conditions of normoxia and high-elevation hypoxia. In line with the predictions of HMTL, anaerobically fuelled sprint speed was unaffected by acute hypoxia while the TPC for aerobic scope became shorter and more symmetrical. This change in TPC shape resulted from both the maximum aerobic scope and the optimal temperature for aerobic scope being reduced in hypoxia as predicted. Following these results, we present a mathematical framework, which we call Temperature–Oxygen Performance Surfaces, to quantify the interactive effects of temperature and oxygen on whole-organism performance in line with the HMTL hypothesis. This framework is transferrable across traits and levels of organization to allow predictions for how ectotherms will respond to novel combinations of temperature and other abiotic factors, providing a useful tool in a time of rapidly changing environmental conditions.info:eu-repo/semantics/publishedVersio