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Sex-Specific Effects of Incubation Temperature on Embryonic Development of Zebra Finch (Taeniopygia guttata) Embryos
Get PDFIn oviparous species, the embryonic environmentparticularly temperaturecan alter phenotype and survival of an individual by affecting its size as well as its metabolic rate. Previous studies have shown that incubation temperatures can affect sex ratio in birds; specifically, low incubation temperatures were shown to produce a male-biased sex ratio in zebra finches (Taeniopygia guttata) possibly because of a higher pre- or postnatal mortality rate in females. We hypothesized that sexes respond differently to suboptimal incubation temperature, leading to a male-biased sex ratio. To test this hypothesis, zebra finch eggs were incubated at 36.1 degrees, 37.5 degrees, or 38.5 degrees C and hatching success, hatchling mass, residual yolk mass, and pectoralis mass were measured. We found that while hatchling mass was similar between the sexes at 37.5 degrees C, female hatchlings were heavier at 36.1 degrees C, and male hatchlings were heavier at 38.5 degrees C. Pectoralis muscle mass was similar between the sexes at 36.1 degrees C; however, at 37.5 degrees C, female pectoralis mass was heavier at hatching than that of males. Females at 37.5 degrees C also had lower residual yolk at hatching compared with males, reflecting a higher use of energy by female embryos compared with male embryos at this temperature. In contrast, residual yolk was similar between the sexes at 36.1 degrees and 38.5 degrees C. Our results suggest that there are sex differences in how incubation temperature alters organ mass and yolk energy reserve; this can lead to a difference in survival at different incubation temperatures between the sexes. Taken together with previous studies showing that females alter incubation behavior with ambient temperature, rising ambient temperatures could impact phenotype and survival of avian offspring in a sex-specific manner.PublishedYe
Fast Magnetosonic Waves Observed by Van Allen Probes: Testing Local Wave Excitation Mechanism
Get PDFLinear Vlasov theory and particle-in-cell (PIC) simulations for electromagnetic fluctuations in a homogeneous, magnetized, and collisionless plasma are used to investigate a fast magnetosonic wave event observed by the Van Allen Probes. The fluctuating magnetic field observed exhibits a series of spectral peaks at harmonics of the proton cyclotron frequency Omega p and has a dominant compressional component, which can be classified as fast magnetosonic waves. Furthermore, the simultaneously observed proton phase space density exhibits positive slopes in the perpendicular velocity space, partial derivative f(p)/partial derivative v(perpendicular to) > 0, which can be a source for these waves. Linear theory analyses and PIC simulations use plasma and field parameters measured in situ except that the modeled proton distribution is modified to have larger partial derivative f(p)/partial derivative v(perpendicular to) under the assumption that the observed distribution corresponds to a marginally stable state when the distribution has already been scattered by the excited waves. The results show that the positive slope is the source of the proton cyclotron harmonic waves at propagation quasi-perpendicular to the background magnetic field, and as a result of interactions with the excited waves the evolving proton distribution progresses approximately toward the observed distribution.PublishedYe
Petrology, Geochronology and Tectonic Setting of Early Triassic Alkaline Metagabbros From the Eastern Pontide Orogenic Belt (NE Turkey): Implications for the Geodynamic Evolution of Gondwana's Early Mesozoic Northern Margin
Get PDFThe Triassic geodynamic evolution of the Pontides Belt, which geographically corresponds to northern Anatolia, is still a matter of debate. We present and interpret geological, petrographical, geochemical, and geochronological data from small, discordant, metagabbroic rocks exposed in the Tokat Massif. Field and petrographic characteristics distinguish four subgroups: (i) medium-grained, slightly lineated, clinopyroxene-rich metagabbros; (ii) fine-grained, nonlineated, clinopyroxene-rich metagabbros; (iii) medium-grained, nonlineated, brown amphibole-rich metagabbros; and (iv) medium-grained, slightly lineated, brown and blue amphibole-rich metagabbros. Magmatic kaersutites give Ar-39/Ar-40 plateau ages of 244.60.5 and 243.160.92Ma and overlap the U-Pb age of titanite from a clinopyroxene-rich sample. Inherited zircons (similar to 460, similar to 880, and similar to 2600Ma) in fine-grained clinopyroxene-rich metagabbros indicate interaction with a range of crustal rocks during the intrusion. The blue amphiboles are magnesioriebeckites that formed during metamorphism or late-stage crystallization. Geochemical data, including whole rock major and trace element concentrations, and Sr-Nd-Pb isotope compositions reveal that both clinopyroxene- and amphibole-rich metagabbros are alkaline in composition but derived from distinct mantle sources. They are compositionally distinct from mafic igneous rocks in the contemporaneous Permo-Triassic Karakaya Complex that is well exposed in the western part of the Pontides Belt. Considering all data, we suggest that the Pontides Belt was shaped above a south dipping subduction zone during Permo-Triassic and the alkaline gabbros that were emplaced into crustal rocks during Early Triassic back-arc rifting of the northern margin of Gondwana.PublishedYe
Genetically determined fungal pathogen tolerance and soil variation influence ectomycorrhizal traits of loblolly pine
Get PDFSelection on genetically correlated traits within species can create indirect effects on one trait by selection on another. The consequences of these trait correlations are of interest because they may influence how suites of traits within species evolve under differing selection pressures, both natural and artificial. By utilizing genetic families of loblolly pine either tolerant (t) or susceptible (s) to two different suites of pathogenic fungi responsible for causing either pine decline or fusiform rust disease, we investigated trait variation and trait correlations within loblolly pine (Pinus taeda L.) by determining how ectomycorrhizal (EM) colonization relates to pathogen susceptibility. We detected interactions between susceptibility to pathogenic fungi and soil inoculation source on loblolly pine compatibility with the EM fungi Thelephora, and on relative growth rate of loblolly pine. Additionally, we detected spatial variation in the loblolly pine–EM fungi interaction, and found that variation in colonization rates by some members of the EM community is not dictated by genetic variation in the host plant but rather soil inoculation source alone. The work presented here illustrates the potential for indirect selection on compatibility with symbiotic EM fungi as a result of selection for resistance to fungal pathogens. Additionally, we present evidence that the host plant does not have a single “mycorrhizal trait” governing interactions with all EM fungi, but rather that it can interact with different fungal taxa independently. Synthesis. An understanding of the genetic architecture of essential traits in focal species is crucial if we are to anticipate and manage the results of natural and artificial selection. As demonstrated here, an essential but often overlooked symbiosis (that between plants and mycorrhizal fungi) may be indirectly influenced by directed selection on the host plant.Ye
Thermal spikes from the urban heat island increase mortality and alter physiology of lizard embryos
Get PDFEffects of global change (i.e. urbanization, climate change) on adult organisms are readily used to predict the persistence of populations. However, effects on embryo survival and patterns of development are less studied, even though embryos are particularly sensitive to abiotic conditions that are altered by global change (e.g. temperature). In reptiles, relatively warm incubation temperatures increase developmental rate and often enhance fitness-relevant phenotypes, but extremely high temperatures cause death. Due to the urban heat island effect, human-altered habitats (i.e. cities) potentially create unusually warm nest conditions that differ from adjacent natural areas in both mean and extreme temperatures. Such vanation may exert selection pressures on embryos. To address this, we measured soil temperatures in places where the Puerto Rican crested anole lizard (Anolis cristatellus) nests in both city and forest habitats. We bred anoles in the laboratory and subjected their eggs to five incubation treatments that mimicked temperature regimes from the field, three of which included brief exposure to extremely high temperatures (i.e. thermal spikes) measured in the city. We monitored growth and survival of hatchlings in the laboratory for 3 months and found that warmer, city temperatures increase developmental rate, but brief, thermal spikes reduce survival. Hatchling growth and survival were unaffected by incubation treatment. The urban landscape can potentially create selection pressures that influence organisms at early (e.g. embryo) and late life stages. Thus, research aimed at quantifying the impacts of urbanization on wildlife populations must include multiple life stages to gain a comprehensive understanding of this important aspect of global change.PublishedYe
Embryo development and global change: how do reptile embryos respond to ecologically relevant thermal stress?
Get PDFTwo components of global change, climate change and urbanization, both contribute to increased ambient temperatures that may induce heat stress or mortality in animals. Each phenomenon independently results in both increased mean temperatures and increased maximum day-time temperatures; however, there is also the potential for these components to act synergistically: extreme temperatures due to the urban heat island effect are likely to be exacerbated as the earth’s surface warms due to climate change. Many animals can respond to harmful temperatures behaviorally, by altering their periods of activity or shifting their habitat use. Such behavioral compensation, however, is unavailable to embryos of ectotherms which typically develop inside eggs in the ground and receive little or no parental care. Thus, this early life stage is expected to be more vulnerable to harmful temperatures caused by aspects of global change, and yet, the effects of ecologically relevant thermal stress on these embryos has received little attention. We sought to understand the consequences of such extreme temperatures on embryological development by utilizing two species of lizard (Anolis sagrei and Anolis cristatellus) that commonly inhabit urban areas. We measured ground temperatures in an urban landscape where lizards nest and modeled daily thermal fluctuations that included brief periods of extremely high temperatures. We then subjected eggs of both species to various magnitudes and frequencies of these thermal fluctuations at multiple stages of embryo development. We report results of embryo survival and highlight the potential for extreme incubation temperatures to differentially impact species.N
Embryo development and global change: how do reptile embryos respond to ecologically relevant thermal stress?
Get PDFTwo components of global change, climate change and urbanization, contribute to increased ambient temperatures that cause heat stress or mortality in animals. Many animals can respond to harmful temperatures behaviorally; however, embryos of ectotherms which develop inside eggs in the ground and receive little or no parental care cannot respond this way. This early life stage is more vulnerable to harmful temperatures, yet, the effects of ecologically relevant thermal stress on these embryos has received little attention. We measured ground temperatures in an urban landscape where lizards (Anolis sagrei and Anolis cristatellus) nest and exposed eggs to extreme nest temperatures in the lab. We determined the critical thermal maximum for embryos of each species and assessed how thermal tolerance might change through development. Our results show that the thermal tolerance of reptile embryos can differ widely among closely related species, and thermal tolerance can change through development.N
Free-Boundary Axisymmetric MHD Equilibrium
Get PDFThe calculation of equilibrium conditions is a common task in the study and modeling of magnetic-confinement experiments for con- trolled nuclear fusion, in which a high-temperature plasma is confined in a finite region of space by magnetic fields. Given the plasma shape, for toroidal devices with axial symmetry, such as tokamaks, the equilibrium calculation reduces to the solution of an elliptic PDE. In several circumstances, the plasma shape may not be known a priori, or one may desire to also compute the magnetic fields in the volume surrounding the plasma through the calculation of a free-boundary equilibrium. This requires either the coil currents or the magnetic poloidal flux on a curve in the vacuum region to be known ab initio. It is well known how to calculate both, but surprisingly until the introduction of the FREE- FIX code no general tools were available in the fusion community for this task. FREE-FIX is a general tool for calculating coil currents to be used as the input for a free-boundary equilibrium. A new formulation is presented, which considerably reduces the computational cost of the calculation. FREE-FIX performs well for different geometries and experiments. Some possible future applications are also suggested
Particle-in-Cell Simulations of the Fast Magnetosonic Mode in a Dipole Magnetic Field: 1-D Along the Radial Direction
Get PDFAn electromagnetic particle-in-cell code is used to investigate self-consistent evolution of the fast magnetosonic mode in a one-dimensional configuration along the radial direction in a dipole background magnetic field. A previous observation of this wave mode is used to select the simulation parameters. A partial shell velocity distribution of energetic protons with a moderate pitch angle anisotropy is used to excite the waves self-consistently. Consistent with local linear theory analysis, wave growth occurs only at exact harmonics of the local proton cyclotron frequency, Omega(p). However, radial propagation quickly removes the waves from the region where they can grow, leading to a time scale of wave amplification much longer than that predicted by linear theory. In addition, radial propagation from multiple wave sources makes the frequency spectrum measured at a single point much broader. The warm background plasma plays an important role in two ways. First, it increases the phase speed of the fast magnetosonic mode; and second, it causes the breakup of the extraordinary mode dispersion relation in the vicinity of the harmonics, where the broken dispersion curves are connected with multiple ion Bernstein modes. In this case, the waves propagating radially are absorbed at locations where their frequency reaches integer multiples of Omega(p) and background protons experience perpendicular heating at those locations.Publishe