Limitation of size by hypoxia in the fruit fly Drosophila melanogaster

first_imgThe size of an organism is of fundamental importance in all biological processes. It dictates many of the critical interactions and physical factors that delimit the envelope within which an organism can grow. We investigated the effects of reduced oxygen on size and development in the fruit fly Drosophila melanogaster, and showed that limiting the oxygen in the environment limits both whole animal and cell size. When oxygen levels were reduced from 20% in nitrogen to 15%, 10% and 7.5%, there was a linear decrease in both male and female mass. Both cell size and cell number decreased in low oxygen, but changes in cell size accounted for a larger proportion of the overall change in fly size. Cell numbers decreased by a maximum of 11% between flies reared in 20% oxygen and those reared in 7.5% oxygen, whereas cell surface area decreased by 17%. Low oxygen levels increased development time and mortality, but reduced fecundity. Reducing the level of oxygen available significantly slowed development times, with flies reared in 10% oxygen emerging on average 1.5 days later than those in 20% oxygen. The effect of oxygen on size is reversible during embryonic and larval development up to the pupal stage, when final size is set.last_img read more

Late Glacial history of the Ross Sea sector of the West Antarctic Ice Sheet: evidence from englacial layering at Talos Dome, East Antarctica

first_imgThe timing of West Antarctic Ice Sheet (WAIS) expansion and retreat during the last glacial cycle is crucial to evaluating the processes controlling ice sheet fluctuations. There is currently debate as to whether grounded ice across what is now the Ross Ice Shelf decayed during the early Holocene or at a time coincident with meltwater pulse 1a. Here we show, from analysis of englacial radio-echo layering across Talos Dome in Oates Land, East Antarctica, that the pattern of snowfall has been relatively consistent for the past 8,000–10,000 years. This was preceded by a transition from glacial maximum-type accumulation at between 10,000 and 20,000 years. We interpret glacial maximum accumulation rates to correspond with the expansion of the grounded WAIS across the Ross shelf, so preventing storm tracks from accessing Victoria Land as they do today (as identified previously at Taylor Dome). The return to modern-type accumulation after 8,000 years is consistent with geological evidence for WAIS retreat. No large-scale alteration in accumulation is observed around 14,000 years ago, during the time of meltwater pulse 1a.last_img read more

A horizon scan of global conservation issues for 2010

first_imgHorizon scanning identifies emerging issues in a given field sufficiently early to conduct research to inform policy and practice. Our group of horizon scanners, including academics and researchers, convened to identify fifteen nascent issues that could affect the conservation of biological diversity. These include the impacts of and potential human responses to climate change, novel biological and digital technologies, novel pollutants and invasive species. We expect to repeat this process and collation annually.last_img read more

The fossil record of Limopsis (Bivalvia: Limopsidae) in Antarctica and the southern high latitudes

first_imgLimopsis is one of the most speciose and widespread bivalve genera in the Southern Ocean at the present day. However, the fossil record of the genus is poorly known from the southern high latitudes. Here, we review the fossil record in this region to help understand the evolutionary origins of the genus. Limopsis infericola sp. nov. and additional specimens of a previously described species are added to the fossil record of Antarctica. The globally distributed limopsid clade had its earliest occurrences in the Early Cretaceous of Europe and New Zealand, then radiated during the Late Cretaceous (Maastrichtian, 70.6-65.5 Ma). Fossil evidence shows that the genus underwent a second, Cenozoic, radiation related to the isolation of Antarctica and the onset of cooling in the southern hemisphere. The genus has persisted in Antarctica for the last 50 myr, adapting to extreme changes in the environmental conditions, including surviving the last glacial maximum in marine refugia.last_img read more

Modelling channelized surface drainage of supraglacial lakes

first_imgSupraglacial lakes can drain to the bed of ice sheets, affecting ice dynamics, or over theirsurface, relocating surface water. Focusing on surface drainage, we first discuss observations of lakedrainage. In particular, for the first time, lakes are observed to drain >70 km across the Nivlisen iceshelf, East Antarctica. Inspired by these observations, we develop a model of lake drainage through achannel that incises into an ice-sheet surface by frictional heat dissipated in the flow. Modelled lakedrainage can be stable or unstable. During stable drainage, the rate of lake-level drawdown exceeds therate of channel incision, so discharge from the lake decreases with time; this can prevent the lake fromemptying completely. During unstable drainage, discharge grows unstably with time and alwaysempties the lake. Model lakes are more prone to drain unstably when the initial lake area, the lake inputand the channel slope are larger. These parameters will vary during atmospheric-warming-inducedablation-area expansion, hence the mechanisms revealed by our analysis can influence the dynamicresponse of ice sheets to warming through their impact on surface-water routing and storage.last_img read more

A multi-wavelength classification method for polar stratospheric cloud types using infrared limb spectra

first_imgThe Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument on board the ESA Envisat satellite operated from July 2002 until April 2012. The infrared limb emission measurements represent a unique dataset of daytime and night-time observations of polar stratospheric clouds (PSCs) up to both poles. Cloud detection sensitivity is comparable to space-borne lidars, and it is possible to classify different cloud types from the spectral measurements in different atmospheric windows regions. Here we present a new infrared PSC classification scheme based on the combination of a well-established two-colour ratio method and multiple 2-D brightness temperature difference probability density functions. The method is a simple probabilistic classifier based on Bayes’ theorem with a strong independence assumption. The method has been tested in conjunction with a database of radiative transfer model calculations of realistic PSC particle size distributions, geometries, and composition. The Bayesian classifier distinguishes between solid particles of ice and nitric acid trihydrate (NAT), as well as liquid droplets of super-cooled ternary solution (STS). The classification results are compared to coincident measurements from the space-borne lidar Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument over the temporal overlap of both satellite missions (June 2006–March 2012). Both datasets show a good agreement for the specific PSC classes, although the viewing geometries and the vertical and horizontal resolution are quite different. Discrepancies are observed between the CALIOP and the MIPAS ice class. The Bayesian classifier for MIPAS identifies substantially more ice clouds in the Southern Hemisphere polar vortex than CALIOP. This disagreement is attributed in part to the difference in the sensitivity on mixed-type clouds. Ice seems to dominate the spectral behaviour in the limb infrared spectra and may cause an overestimation in ice occurrence compared to the real fraction of ice within the PSC area in the polar vortex. The entire MIPAS measurement period was processed with the new classification approach. Examples like the detection of the Antarctic NAT belt during early winter, and its possible link to mountain wave events over the Antarctic Peninsula, which are observed by the Atmospheric Infrared Sounder (AIRS) instrument, highlight the importance of a climatology of 9 Southern Hemisphere and 10 Northern Hemisphere winters in total. The new dataset is valuable both for detailed process studies, and for comparisons with and improvements of the PSC parameterizations used in chemistry transport and climate models.last_img read more

Automated detection of basal icequakes and discrimination from surface crevassing

first_imgIcequakes at or near the bed of a glacier have the potential to allow us to investigate theinteraction of ice with the underlying till or bedrock. Understanding this interaction is important forstudying basal sliding of glaciers and ice streams, a critical process in ice dynamics models used to con-strain future sea-level rise projections. However, seismic observations on glaciers can be dominated byseismic energy from surface crevassing. We present a method of automatically detecting basal icequakesand discriminating them from surface crevassing, comparing this method to a commonly used spectrum-based method of detecting icequakes. We use data from Skeidararjökull, an outlet glacier of theVatnajökull Ice Cap, South-East Iceland, to demonstrate that our method outperforms the commonlyused spectrum-based method. Our method detects a higher number of basal icequakes, has a lowerrate of incorrectly identifying crevassing as basal icequakes and detects an additional, spatially inde-pendent basal icequake cluster. We also show independently that the icequakes do not originate fromnear the glacier surface. We conclude that the method described here is more effective than currentlyimplemented methods for detecting and discriminating basal icequakes from surface crevassing.last_img read more

A new approach to constructing models of electron diffusion by EMIC waves in the radiation belts

first_imgElectromagnetic Ion Cyclotron (EMIC) waves play an important role in relativistic electron losses in the radiation belts through diffusion via resonant wave‐particle interactions. We present a new approach for calculating bounce and drift‐averaged EMIC electron diffusion coefficients. We calculate bounce‐averaged diffusion coefficients, using quasi‐linear theory, for each individual CRRES EMIC wave observation using fitted wave properties, the plasma density and the background magnetic field. These calculations are then combined into bounce‐averaged diffusion coefficients. The resulting coefficients therefore capture the combined effects of individual spectra and plasma properties as opposed to previous approaches that use average spectral and plasma properties, resulting in diffusion over a wider range of energies and pitch‐angles. These calculations, and their role in radiation belt simulations, are then compared against existing diffusion models. The new diffusion coefficients are found to significantly improve the agreement between the calculated decay of relativistic electrons and Van Allen Probes data.last_img read more

Bees Outlast River Cats

first_img Written by Robert Lovell Tags: Baseball/PCL/Salt Lake Bees May 18, 2018 /Sports News – Local Bees Outlast River Cats FacebookTwitterLinkedInEmail(Salt Lake City, UT)  —  The Bees’ offense piled up 17 hits in a 12-11 win over the River Cats at Smith’s Ball Park.Chris Carter finished 4-for-5 with two runs and three RBI for Salt Lake.  Akeel Morris earned the relief win for the Bees.The series continues tonight.  First pitch is at 6:35 p.m.last_img read more