Search results for "2400"
showing 10 items of 23 documents
Daphnia invest in sexual reproduction when its relative costs are reduced
2018
The timing of sex in facultatively sexual organisms is critical to fitness, due to the differing demographic consequences of sexual versus asexual reproduction. In addition to the costs of sex itself, an association of sex with the production of dormant life stages also influences the optimal use of sex, especially in environments where resting eggs are essential to survive unfavourable conditions. Here we document population dynamics and the occurrence of sexual reproduction in natural populations of Daphnia magna across their growing season. The frequency of sexually reproducing females and males increased with population density and with decreasing asexual clutch sizes. The frequency of…
A genomic map of climate adaptation in Mediterranean cattle breeds
2019
International audience; Domestic species such as cattle (Bos taurus taurus and B. t. indicus) represent attractive biological models to characterize the genetic basis of short term evolutionary response to climate pressure induced by their post-domestication history. Here, using newly generated dense SNP genotyping data, we assessed the structuring of genetic diversity of 21 autochtonous cattle breeds from the whole Mediterranean basin and performed genome-wide association analyses with covariables discriminating the different Mediterranean climate sub-types. This provided insights into both the demographic and adaptive histories of Mediterranean cattle. In particular, a detailed functional…
Pairing context determines condition-dependence of song rate in a monogamous passerine bird.
2013
Condition-dependence of male ornaments is thought to provide honest signals on which females can base their sexual choice for genetic quality. Recent studies show that condition-dependence patterns can vary within populations. Although long-term association is thought to promote honest signalling, no study has explored the influence of pairing context on the condition-dependence of male ornaments. In this study, we assessed the influence of natural variation in body condition on song rate in zebra finches ( Taeniopygia guttata ) in three different situations: during short and long encounters with an unfamiliar female, and within heterosexual mated pairs. We found consistent individual diff…
The way wear goes: phytolith-based wear on the dentine–enamel system in guinea pigs (Cavia porcellus)
2019
The effect of phytoliths on tooth wear and function has been contested in studies of animal–plant interactions. For herbivores whose occlusal chewing surface consists of enamel ridges and dentine tissue, the phytoliths might particularly erode the softer dentine, exposing the enamel ridges to different occlusal forces and thus contributing to enamel wear. To test this hypothesis, we fed guinea pigs (Cavia porcellus; n = 36 in six groups) for threeweeks exclusively on dry or fresh forage of low(lucerne), moderate (fresh timothy grass) or very high (bamboo leaves) silica content representing corresponding levels of phytoliths. We quantified the effect of these treatments with measuremen…
'Palaeoshellomics' reveals the use of freshwater mother-of-pearl in prehistory
2019
The extensive use of mollusc shell as a versatile raw material is testament to its importance in prehistoric times. The consistent choice of certain species for different purposes, including the making of ornaments, is a direct representation of how humans viewed and exploited their environment. The necessary taxonomic information, however, is often impossible to obtain from objects that are small, heavily worked or degraded. Here we propose a novel biogeochemical approach to track the biological origin of prehistoric mollusc shell. We conducted an in-depth study of archaeological ornaments using microstructural, geochemical and biomolecular analyses, including ‘palaeoshellomics’, the first…
Oxidative stress preconditioning of mouse perivascular myogenic progenitors selects a subpopulation of cells with a distinct survival advantage in vi…
2018
AbstractCell engraftment, survival and integration during transplantation procedures represent the crux of cell-based therapies. Thus, there have been many studies focused on improving cell viability upon implantation. We used severe oxidative stress to select for a mouse mesoangioblast subpopulation in vitro and found that this subpopulation retained self-renewal and myogenic differentiation capacities while notably enhancing cell survival, proliferation and migration relative to unselected cells. Additionally, this subpopulation of cells presented different resistance and recovery properties upon oxidative stress treatment, demonstrating select advantages over parental mesoangioblasts in …
Phylogenetic variation in cortical layer II immature neuron reservoir of mammals
2020
The adult mammalian brain is mainly composed of mature neurons. A limited amount of stem cell-driven neurogenesis persists in postnatal life and is reduced in large-brained species. Another source of immature neurons in adult brains is cortical layer II. These cortical immature neurons (cINs) retain developmentally undifferentiated states in adulthood, though they are generated before birth. Here, the occurrence, distribution and cellular features of cINs were systematically studied in 12 diverse mammalian species spanning from small-lissencephalic to large-gyrencephalic brains. In spite of well-preserved morphological and molecular features, the distribution of cINs was highly heterogeneou…
Nonlinear femtosecond pulse propagation in an all-solid photonic bandgap fiber
2009
Nonlinear femtosecond pulse propagation in an all-solid photonic bandgap fiber is experimentally and numerically investigated. Guiding light in such fiber occurs via two mechanisms: photonic bandgap in the central silica core or total internal reflection in the germanium doped inclusions. By properly combining spectral filtering, dispersion tailoring and pump coupling into the fiber modes, we experimentally demonstrate efficient supercontinuum generation with controllable spectral bandwidth.
Critical appraisal of tubular putative eumetazoans from the Ediacaran Weng'an Doushantuo biota
2015
Molecular clock analyses estimate that crown-group animals began diversifying hundreds of millions of years before the start of the Cambrian period. However, the fossil record has not yielded unequivocal evidence for animals during this interval. Some of the most promising candidates for Precambrian animals occur in the Weng'an biota of South China, including a suite of tubular fossils assigned to Sinocyclocyclicus, Ramitubus, Crassitubus and Quadratitubus, that have been interpreted as soft-bodied eumetazoans comparable to tabulate corals. Here, we present new insights into the anatomy, original composition and phylogenetic affinities of these taxa based on data from synchrotron radiation …
Anthropoid versus strepsirhine status of the African Eocene primates Algeripithecus and Azibius: craniodental evidence.
2009
Recent fossil discoveries have demonstrated that Africa and Asia were epicentres for the origin and/or early diversification of the major living primate lineages, including both anthropoids (monkeys, apes and humans) and crown strepsirhine primates (lemurs, lorises and galagos). Competing hypotheses favouring either an African or Asian origin for anthropoids rank among the most hotly contested issues in paleoprimatology. The Afrocentric model for anthropoid origins rests heavily on the >45 Myr old fossil Algeripithecus minutus from Algeria, which is widely acknowledged to be one of the oldest known anthropoids. However, the phylogenetic position of Algeripithecus with respect to other p…