Search results for "RAS"
showing 10 items of 26429 documents
Dust and grit matter: abrasives of different size lead to opposing dental microwear textures in experimentally fed sheep (Ovis aries)
2020
ABSTRACT External abrasives ingested along with the herbivore diet are considered main contributors to dental wear, though how the different sizes and concentrations of these abrasives influence wear remains unclear. Dental microwear texture analysis (DMTA) is an established method for dietary reconstruction which describes a tooth9s surface topography on a micrometre scale. The method has yielded conflicting results as to the effect of external abrasives. In the present study, a feeding experiment was performed on sheep (Ovis aries) fed seven diets of different abrasiveness. Our aim was to discern the individual effects of size (4, 50 and 130 µm) and concentration (0%, 4% and 8% of dry mat…
A minimalist macroparasite diversity in the round goby of the Upper Rhine reduced to an exotic acanthocephalan lineage.
2018
AbstractThe round goby, Neogobius melanostomus, is a Ponto-Caspian fish considered as an invasive species in a wide range of aquatic ecosystems. To understand the role that parasites may play in its successful invasion across Western Europe, we investigated the parasitic diversity of the round goby along its invasion corridor, from the Danube to the Upper Rhine rivers, using data from literature and a molecular barcoding approach, respectively. Among 1666 parasites extracted from 179 gobies of the Upper Rhine, all of the 248 parasites barcoded on the c oxidase subunit I gene were identified as Pomphorhynchus laevis. This lack of macroparasite diversity was interpreted as a loss of parasites…
Grazing decreases N partitioning among coexisting plant species
2017
Herbivores play a key role in shaping ecosystem structure and functions by influencing plant and microbial community composition and nutrient cycling. This study investigated the long‐term effects of herbivores on plant resource acquisition. We explored differences in the natural δ15N signatures in plant, microbial and soil N pools, and examined mycorrhizal colonization in two tundra sites that have been either lightly or heavily grazed by reindeer for more than 50 years. The study examined changes in nutrient acquisition in five common tundra plants with contrasting traits and mycorrhiza status; the mycorrhizal dwarf shrubs, Betula nana, Vaccinium myrtillus and Empetrum hermaphroditum; a m…
Diversity of foraging strategies and responses to predator interference in seed-eating carabid beetles
2019
12 pages; International audience; The prediction of pest regulation by multi-predator communities often remains challenging because of variable and opposite effects of niche complementarity and predator interference. Carabid communities are regulating weeds in arable fields and include a mix of species ranging from granivores to predators that are obligate omnivores. It is not clear from field studies whether granivore and obligate omnivore species either contribute equally or are complementary in the process of weed suppression, and little is known about the impact of potential predator interference within carabid communities on weed suppression. We compared the weed seed foraging strategy…
Abundance–variance and abundance–occupancy relationships in a marine host–parasite system: The importance of taxonomy and ecology of transmission
2011
Abundance-occupancy and abundance-variance relationships are two of the most general macroecological patterns capturing essential fundamentals of the structuring of species distributions and are widely documented for free-living animal and plant species populations at different spatial scales. However, empirical data for parasites have been gathered using appropriate sampling designs only recently. We performed analyses across species of the variation in infection parameters and patterns of aggregation of the most widespread parasites in the marine sparid fish Boops boops across seven localities of two marine biogeographical regions, the North East Atlantic and the Mediterranean. We used a …
Prolonged diapause has sex-specific fertility and fitness costs
2019
AbstractDiapause in seasonal environments allows insects to survive adverse seasons. However, individuals can sometimes enter a prolonged diapause for more than a year, and also skip favourable seasons, which can bring additional costs through e.g. loss of metabolic resources. At the same time, prolonged diapause can be beneficial if it allows individuals to have a risk-spreading strategy to skip potentially suboptimal breeding seasons. We studied if prolonged diapause (2-year diapause) negatively affects the fertility and fitness of female and male Colorado potato beetles (Leptinotarsa decemlineata) compared to control (1-year diapause) beetles. We also tested the parental effects on the s…
Differential impact of marine debris ingestion during ontogenetic dietary shift of green turtles in Uruguayan waters
2018
Anthropogenic debris ingestion has been reported for green turtles in all their life stages worldwide. The aim of the present study is to evaluate the marine debris ingestion by green turtles stranded in Uruguayan coast between 2005 and 2013. Debris items were categorized and quantified by frequency of occurrence, relative weight, volume and number of items. A total of 96 dead stranded turtles were analyzed and 70% presented debris in their guts. The majority of debris found were plastic, being hard plastics the most abundant in weight. We found no differences in debris ingestion in stranded turtles a long the Uruguayan coast. However we detected a negative correlation between the presence …
Cyclic hantavirus epidemics in humans--predicted by rodent host dynamics.
2009
Wildlife-originated zoonotic diseases are a major contributor to emerging infectious diseases. Hantaviruses cause thousands of human disease cases annually worldwide, and understanding and predicting human hantavirus epidemics still poses unsolved challenges. Here we studied the three-level relationships between the human disease nephropathia epidemica (NE), its etiological agent Puumala hantavirus (PUUV) and the rodent host of the virus, the bank vole (Myodes glareolus). A large and long-term data set (14 years, 2583 human NE cases and 4751 trapped bank voles) indicates that the number of human infections shows both seasonal and multi-annual fluctuations, is influenced by the phase of vole…
Involvement of osmotic cell shrinkage on the proton extrusion rate in Saccharomyces cerevisiae
2001
Saccharomyces cerevisiae has been subjected to hyperosmotic shocks by using permeating (sorbitol, xylitol, glycerol, NaCl) and nonpermeating (PEG 600) solutes. The proton extrusion rate decreased as the osmotic pressure increased, whichever solute was used. However, the total inhibition of the cellular H+ extrusion depended on the solute used. A total inhibition was observed at about 20 MPa with glycerol, xylitol and sorbitol. With PEG 600, a total inhibition of extracellular acidification was obtained at 8.5 MPa. NaCl, with an extracellular pressure of 37.8 MPa (near saturation), did not completely inhibit the extracellular acidification. These results showed that the total inhibition of p…
Experimental and natural cathodoluminescence in the shell of Crassostrea gigas from Thau lagoon (France): ecological and environmental implications.
2006
We present a cathodoluminescence (CL) study of growth layer deposition in the shell of the oyster Crassostrea gigas. CL is based on the physical properties of lattice-bound manganese (Mn2+), which is the main activator in calcium carbonate. Our study involved chemical marking by immersing individuals in seawater to which manganese chloride had been added, and subsequent reading of the shell with CL microscopy coupled with numeric treatment of microphotographs; CL emission was analyzed using a scanning electron microscope coupled to a spectrometer. Since the marking did not harm the oysters, repeated markings were possible, allowing validation of the inferences made from analysis of the shel…