792 research outputs found
Recreational Fishing-Related Injuries to Australian Pelicans (Pelecanus Conspicillatus ) and Other Seabirds in a South Australian Estuarine and River Area
113 seabirds treated over 5.5 years had 132 fishing-related injuries that included entanglement with line only (N=35/132; 26.5%), entanglement
with line and an associated hook (N=47/132; 35.6%), embedded hooks only (N=34/132; 25.7%) and foreign body ingestion (N=16/132; 12.1%). The percentage of fishing-related injuries ranged from 0.9% for banded stilts (Cladorhynchus leucocephalus), pacific gulls (Larus pacificus) and masked lapwing plovers (Vanellus miles), to 59.3% for Australian pelicans (Pelecanus conspicillatus). Entanglement and/or embedded hooks were present more often than injuries from ingestion; i.e. 97% (70/72) of pelicans had entanglement and/or embedded hook injuries; of these 35/72 [48.6%] were entangled with line and hooks, 24/72 [33.3%] had embedded hooks alone and 11/72 [15.3%] were entangled with lines only, with only 3% (2/72) having injuries from ingestion. A count of sea and river birds in close proximity to fishers revealed that the majority were pelicans (33.9%), compared to pied cormorants (28.6%), silver gulls (21.4%) and black swans (16.1%). Regular removal of discarded fishing material along local shores resulted in no reduction in the numbers of entangled or hooked seabirds. It appears likely, therefore, that such injuries may result from seabird proximity to active recreational fishing, rather than from entanglement in discarded material
Constraints on the shapes of galaxy dark matter haloes from weak gravitational lensing
We study the shapes of galaxy dark matter haloes by measuring the anisotropy
of the weak gravitational lensing signal around galaxies in the second
Red-sequence Cluster Survey (RCS2). We determine the average shear anisotropy
within the virial radius for three lens samples: all galaxies with
19<m_r'<21.5, and the `red' and `blue' samples, whose lensing signals are
dominated by massive low-redshift early-type and late-type galaxies,
respectively. To study the environmental dependence of the lensing signal, we
separate each lens sample into an isolated and clustered part and analyse them
separately. We also measure the azimuthal dependence of the distribution of
physically associated galaxies around the lens samples. We find that these
satellites preferentially reside near the major axis of the lenses, and
constrain the angle between the major axis of the lens and the average location
of the satellites to =43.7 deg +/- 0.3 deg for the `all' lenses,
=41.7 deg +/- 0.5 deg for the `red' lenses and =42.0 deg +/- 1.4
deg for the `blue' lenses. For the `all' sample, we find that the anisotropy of
the galaxy-mass cross-correlation function =0.23 +/- 0.12, providing
weak support for the view that the average galaxy is embedded in, and
preferentially aligned with, a triaxial dark matter halo. Assuming an
elliptical Navarro-Frenk-White (NFW) profile, we find that the ratio of the
dark matter halo ellipticity and the galaxy ellipticity
f_h=e_h/e_g=1.50+1.03-1.01, which for a mean lens ellipticity of 0.25
corresponds to a projected halo ellipticity of e_h=0.38+0.26-0.25 if the halo
and the lens are perfectly aligned. For isolated galaxies of the `all' sample,
the average shear anisotropy increases to =0.51+0.26-0.25 and
f_h=4.73+2.17-2.05, whilst for clustered galaxies the signal is consistent with
zero. (abridged)Comment: 28 pages, 23 figues, accepted for publication in A&
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Comparisons of host mitochondrial, nuclear and endosymbiont bacterial genes reveal cryptic fig wasp species and the effects of Wolbachia on host mtDNA evolution and diversity
Background
Figs and fig-pollinating wasp species usually display a highly specific one-to-one association. However, more and more studies have revealed that the "one-to-one" rule has been broken. Co-pollinators have been reported, but we do not yet know how they evolve. They may evolve from insect speciation induced or facilitated by Wolbachia which can manipulate host reproduction and induce reproductive isolation. In addition, Wolbachia can affect host mitochondrial DNA evolution, because of the linkage between Wolbachia and associated mitochondrial haplotypes, and thus confound host phylogeny based on mtDNA. Previous research has shown that fig wasps have the highest incidence of Wolbachia infection in all insect taxa, and Wolbachia may have great influence on fig wasp biology. Therefore, we look forward to understanding the influence of Wolbachia on mitochondrial DNA evolution and speciation in fig wasps.
Results
We surveyed 76 pollinator wasp specimens from nine Ficus microcarpa trees each growing at a different location in Hainan and Fujian Provinces, China. We found that all wasps were morphologically identified as Eupristina verticillata, but diverged into three clades with 4.22-5.28% mtDNA divergence and 2.29-20.72% nuclear gene divergence. We also found very strong concordance between E. verticillata clades and Wolbachia infection status, and the predicted effects of Wolbachia on both mtDNA diversity and evolution by decreasing mitochondrial haplotypes.
Conclusions
Our study reveals that the pollinating wasp E. verticillata on F. microcarpa has diverged into three cryptic species, and Wolbachia may have a role in this divergence. The results also indicate that Wolbachia strains infecting E. verticillata have likely resulted in selective sweeps on host mitochondrial DNA
Flower Development as an Interplay between Dynamical Physical Fields and Genetic Networks
In this paper we propose a model to describe the mechanisms by which undifferentiated cells attain gene configurations underlying cell fate determination during morphogenesis. Despite the complicated mechanisms that surely intervene in this process, it is clear that the fundamental fact is that cells obtain spatial and temporal information that bias their destiny. Our main hypothesis assumes that there is at least one macroscopic field that breaks the symmetry of space at a given time. This field provides the information required for the process of cell differentiation to occur by being dynamically coupled to a signal transduction mechanism that, in turn, acts directly upon the gene regulatory network (GRN) underlying cell-fate decisions within cells. We illustrate and test our proposal with a GRN model grounded on experimental data for cell fate specification during organ formation in early Arabidopsis thaliana flower development. We show that our model is able to recover the multigene configurations characteristic of sepal, petal, stamen and carpel primordial cells arranged in concentric rings, in a similar pattern to that observed during actual floral organ determination. Such pattern is robust to alterations of the model parameters and simulated failures predict altered spatio-temporal patterns that mimic those described for several mutants. Furthermore, simulated alterations in the physical fields predict a pattern equivalent to that found in Lacandonia schismatica, the only flowering species with central stamens surrounded by carpels
Numerical simulation of blood flow and pressure drop in the pulmonary arterial and venous circulation
A novel multiscale mathematical and computational model of the pulmonary circulation is presented and used to analyse both arterial and venous pressure and flow. This work is a major advance over previous studies by Olufsen et al. (Ann Biomed Eng 28:1281–1299, 2012) which only considered the arterial circulation. For the first three generations of vessels within the pulmonary circulation, geometry is specified from patient-specific measurements obtained using magnetic resonance imaging (MRI). Blood flow and pressure in the larger arteries and veins are predicted using a nonlinear, cross-sectional-area-averaged system of equations for a Newtonian fluid in an elastic tube. Inflow into the main pulmonary artery is obtained from MRI measurements, while pressure entering the left atrium from the main pulmonary vein is kept constant at the normal mean value of 2 mmHg. Each terminal vessel in the network of ‘large’ arteries is connected to its corresponding terminal vein via a network of vessels representing the vascular bed of smaller arteries and veins. We develop and implement an algorithm to calculate the admittance of each vascular bed, using bifurcating structured trees and recursion. The structured-tree models take into account the geometry and material properties of the ‘smaller’ arteries and veins of radii ≥ 50 μ m. We study the effects on flow and pressure associated with three classes of pulmonary hypertension expressed via stiffening of larger and smaller vessels, and vascular rarefaction. The results of simulating these pathological conditions are in agreement with clinical observations, showing that the model has potential for assisting with diagnosis and treatment for circulatory diseases within the lung
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