1,385 research outputs found
Provenance does matter: links between winter trophic segregation and the migratory origins of European robins
Amongst migratory species, it is common to find individuals from different populations or geographical origins sharing staging or wintering areas. Given their differing life histories, ecological theory would predict that the different groups of individuals should exhibit some level of niche segregation. This has rarely been investigated because of the difficulty in assigning migrating individuals to breeding areas. Here, we start by documenting a broad geographical gradient of hydrogen isotopes (δ2H) in robin Erithacus rubecula feathers across Europe. We then use δ2H, as well as wing-tip shape, as surrogates for broad migratory origin of birds wintering in Iberia, to investigate the ecological segregation of populations. Wintering robins of different sexes, ages and body sizes are known to segregate between habitats in Iberia. This has been attributed to the despotic exclusion of inferior competitors from the best patches by dominant individuals. We find no segregation between habitats in relation to δ2H in feathers, or to wing-tip shape, which suggests that no major asymmetries in competitive ability exist between migrant robins of different origins. Trophic level (inferred from nitrogen isotopes in blood) correlated both with δ2H in feathers and with wing-tip shape, showing that individuals from different geographic origins display a degree of ecological segregation in shared winter quarters. Isotopic mixing models indicate that wintering birds originating from more northerly populations consume more invertebrates. Our multi-scale study suggests that trophic-niche segregation may result from specializations (arising in the population-specific breeding areas) that are transported by the migrants into the shared wintering grounds
Avaliação do conjunto de acessos da coleção de trabalho de variedades tradicionais de abóbora para características quantitativas da polpa.
Anais do 1º Simpósio da Rede de Recursos Genéticos Vegetais do Nordeste (I RGVNE), Cruz das Almas, nov. 2013
A new gravitational N-body simulation algorithm for investigation of cosmological chaotic advection
Recently alternative approaches in cosmology seeks to explain the nature of
dark matter as a direct result of the non-linear spacetime curvature due to
different types of deformation potentials. In this context, a key test for this
hypothesis is to examine the effects of deformation on the evolution of large
scales structures. An important requirement for the fine analysis of this pure
gravitational signature (without dark matter elements) is to characterize the
position of a galaxy during its trajectory to the gravitational collapse of
super clusters at low redshifts. In this context, each element in an
gravitational N-body simulation behaves as a tracer of collapse governed by the
process known as chaotic advection (or lagrangian turbulence). In order to
develop a detailed study of this new approach we develop the COsmic LAgrangian
TUrbulence Simulator (COLATUS) to perform gravitational N-body simulations
based on Compute Unified Device Architecture (CUDA) for graphics processing
units (GPUs). In this paper we report the first robust results obtained from
COLATUS.Comment: Proceedings of Sixth International School on Field Theory and
Gravitation-2012 - by American Institute of Physic
Competition among european robins Erithacus rubecula in the winter quarters: Sex is the best predictor of priority of access to experimental food resources
Competition for resources by individuals of different sexes, ages, body sizes or geographical
originsmay have varied implications, from demography to the evolution ofmigratory
systems. European robins Erithacus rubecula display segregation by habitat in relation to
sex, age, body size and geographic origin in the winter quarters. Here we report on an experiment
to investigate the existence of asymmetries in the priority of access to food resources
among unconstrained individuals in their natural environment. Feeders with
mealwormswere provided in an areawith a high density of wintering robins and, after 15
days of provisioning, were replaced by a spring trap thatwas operated during a whole day.
The first individuals to be caught in each trap were heavier and had higher fat andmuscle
scores than last-caught individuals. Based on this and on behavioural observations, we
conclude that first-caught individuals had priority of access to feeders. First- and lastcaught
individuals did not differ in body size, wingtip shape or age ratios. However,
whilst 35% of the first-caught individuals weremales, only 6%of the last-caught individuals
weremales. This suggests that sex is an important predictor of the outcomes of competition
in an area where multiple robin populations coexist in winter, while, at least on
sites where no strictly sedentary individuals are present, geographic origin may be relatively
unimportant
Obtention and characterization of microcrystalline cellulose from industrial melon residues following a biorefinery approach
Residual melon by-products were explored for the first time as a bioresource of microcrystalline cellulose (MCC) obtention. Two alkaline extraction methods were employed, the traditional (4.5% NaOH, 2 h, 80 °C) and a thermo-alkaline in the autoclave (2% NaOH, 1 h, 100 °C), obtaining a yield of MCC ranging from 4.76 to 9.15% and 2.32 to 3.29%, respectively. The final MCCs were characterized for their chemical groups by Fourier-transform infrared spectroscopy (FTIR), crystallinity with X-ray diffraction, and morphology analyzed by scanning electron microscope (SEM). FTIR spectra showed that the traditional protocol allows for a more effective hemicellulose and lignin removal from the melon residues than the thermo-alkaline process. The degree of crystallinity of MCC ranged from 51.51 to 61.94% and 54.80 to 55.07% for the thermo-alkaline and traditional processes, respectively. The peaks detected in X-ray diffraction patterns indicated the presence of Type I cellulose. SEM analysis revealed microcrystals with rough surfaces and great porosity, which could remark their high-water absorption capacity and drug-carrier capacities. Thus, these findings could respond to the need to valorize industrial melon by-products as raw materials for MCC obtention with potential applications as biodegradable materials.info:eu-repo/semantics/publishedVersio
FISH and DAPI staining of the synaptonemal complex of the Nile tilapia (Oreochromis niloticus) allow orientation of the unpaired region of bivalent 1 observed during early pachytene
Bivalent 1 of the synaptonemal complex (SC) in XY male Oreochromis niloticus shows an unpaired terminal region in early pachytene. This appears to be related to recombination suppression around a sex determination locus. To allow more detailed analysis of this, and unpaired regions in the karyotype of other Oreochromis species, we developed techniques for FISH on SC preparations, combined with DAPI staining. DAPI staining identified presumptive centromeres in SC bivalents, which appeared to correspond to the positions observed in the mitotic karyotype (the kinetochores could only be identified sporadically in silver stained EM SC images). Furthermore, two BAC clones containing Dmo (dmrt4) and OniY227 markers that hybridize to known positions in chromosome pair 1 in mitotic spreads (near the centromere, FLpter 0.25, and the putative sex determination locus, FLpter 0.57, respectively) were used as FISH probes on SCs to verify that the presumptive centromere identified by DAPI staining was located in the expected position. Visualization of both the centromere and FISH signals on bivalent 1 allowed the unpaired region to be positioned at Flpter 0.80 to 1.00, demonstrating that the unpaired region is located in the distal part of the long arm(s). Finally, differences between mitotic and meiotic measurements are discussed
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