76 research outputs found
Bern, Burgerbibliothek, Cod. A 95.5 : Robin Comtet: Panégyrique de Blanche de Navarre (fragment)
No full textFragment of a panegyric on Queen Blanche of Navarre (1331–1398), consisting of almost 400 verses. The author Robin Comtet - who mentions himself toward the end of the piece - is not otherwise known. The poem seems to have been preserved only in this copy and has not yet been published.Online Since: 2018-06-1
Population structure and recruitment in mytilid bivalves from the Lucky Strike and Menez Gwen hydrothermal vent fields (37°17'N and 37°50'N on the Mid-Atlantic Ridge)
No full textPopulation structure and recruitment pattern of undescribed mytilid bivalves that dominate the animal communities associated with vents of the Lucky Strike and Menez Gwen hydrothermal vent fields (37 degrees 17' N and 37 degrees 50' N on the Mid-Atlantic Ridge) were studied from size-frequency analyses. Intra-site comparisons reveal that length-frequency distributions differ significantly from one location to the other. This spatial segregation of the sizes could be due to spatio-temporal variability in environmental conditions and to intraspecific competition processes, especially adult-larval interactions (competition for space and food resources, intraspecific larviphagy) that could prevent larvae from settling on surfaces covered by adults. A modal decomposition analysis was conducted after pooling samples collected from different locations at the same site. Polymodal structure of length-frequency distributions indicates that recruitment is likely discontinuous in time. The presence of postlarvae in each population of the Lucky Strike vent field suggests that a recruitment event took place just before sampling in June 1994, and that mytilid recruitment is synchronized between sites, which is confirmed by the comparison of modal values. Length-frequency distribution of the Menez Gwen mytilid population displays similar modal values, especially for the smallest mode. This suggests a synchronization of the recruitment between the 2 vent fields, which are separated by a distance of 60 km, No seasonal pattern in recruitment could be identified although newly recruited individuals were observed in June 1993 on Lucky Strike sites
Influence des conditions trophiques sur le développement larvaire de l'espèce invasive Crepidula fornicata (conséquences sur ses capacités de dispersion)
No full textLes introductions d espèces exotiques constituent l une des causes majeures d altération des écosystèmes marins côtiers. La phase larvaire pélagique des invertébrés à cycle bentho-pélagique joue un rôle majeur à toutes les étapes du processus d'introduction et peut contribuer au succès ou à l'échec d'une introduction. L'étude des mécanismes modulant les traits d'histoire de vie larvaires est donc primordiale pour la compréhension des processus d'introduction. L'objectif général de mon travail de thèse est de déterminer quelle est l'influence de la disponibilité en nourriture (en termes de quantité et de qualité) sur les capacités de développement des larves de Crepidula fornicata, gastéropode emblématique des introductions biologiques sur les côtes européennes. Cette problématique est complexe car dans son aire d introduction, C. fornicata présente une période de reproduction longue (de février à novembre) qui implique (1) que l investissement maternel pour la descendance peut varier tout au long de cette période et (2) que les larves émises se trouvent en présence de sources de nourriture variables. Les résultats obtenus ont mis en évidence, grâce au traçage isotopique enrichi (13C), que les embryons encapsulés dépendaient majoritairement de l investissement maternel pour leur développement. L'étude de la composition en acides gras (source énergétique essentielle pour les descendants et biomarqueurs de la qualité) des femelles, des embryons et des larves a mis en évidence une meilleure qualité des femelles et des embryons en milieu de période de reproduction. L'étude de la nutrition larvaire, à l aide du double marquage isotopique (13C, 15N) et d'expériences de broutage sur des communautés planctoniques naturelles, a montré que les larves de C. fornicata (1) utilisent préférentiellement le nanoplancton (dont les diatomées), et (2) ont la capacité de se nourrir à partir du compartiment bactérien. Ces résultats, combinés aux données de suivi in situ et aux résultats issus de l'utilisation des biomarqueurs lipidiques, témoignent de la capacité des larves de C. fornicata à se nourrir sur une large gamme de sources nutritives, tant sur le plan qualitatif que quantitatif. Il est proposé que ces capacités trophiques aient contribué à favoriser l expansion de cette espèce sur les côtes européennes.PARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocROSCOFF-Observ.Océanol. (292393008) / SudocSudocFranceF
Data from: Unexpected collective larval dispersal but little support for sweepstakes reproductive success in the highly dispersive brooding mollusk Crepidula fornicata
No full textIn many marine invertebrates, long-distance dispersal is achieved during an extended pelagic larval phase. Although such dispersal should result in high gene flow over broad spatial scales, fine-scale genetic structure has often been reported, a pattern attributed to interfamilial variance in reproductive success and limited homogenization during dispersal. To examine this hypothesis, the genetic diversity of dispersing larvae must be compared with the post-dispersal stages, i.e. benthic recruits and adults. Such data remain however scarce due to the difficulty to sample and analyze larvae of minute size. Here we carried out such an investigation using the marine gastropod Crepidula fornicata. Field sampling of three to four larval pools was conducted over the reproductive season and repeated over three years. The genetic composition of larval pools, obtained with 16 microsatellite loci, was compared with that of recruits and adults sampled from the same site and years. Conversely to samples of juveniles and adults, large genetic temporal variations between larval pools produced at different times of the same reproductive season were observed. In addition, full- and half-sibs were detected in early larvae and post-dispersal juveniles, pointing to correlated dispersal paths between several pairs of individuals. Inbred larvae were also identified. Such collective larval dispersal was unexpected given the long larval duration of the study species. Our results suggest that each larval pool is produced by a small effective number of reproducers but that, over a reproductive season, the whole larval pool is produced by large numbers of reproducers across space and time
Evidence of a sexual pause in <i>Bathymodiolus azoricus</i> (Bivalvia: Mytilidae) from hydrothermal vents of the Mid-Atlantic Ridge
No full textHistological sections of the gonad of Bathymodiolus azoricus from the Lucky Strike and Menez Gwen hydrothermal vent fields (Mid-Atlantic Ridge) demonstrated a spawning event in this species in May 1994, synchronous between the two vent fields located 60 km apart, and a sexual pause in gametogenesis. As reported for other vent mytilid species, B. azoricus from Lucky Strike and Menez Gwen could exhibit hermaphroditism.</jats:p
Preparation of mollusc larval shells for individual geochemical analysis v1
No full textThis protocol describes the digestion process of mollusc larvae and is modified from the procedure found in Becker et al. (2005). Here, we indicate the entire process to obtain the digestion solution, as well as cleaning glassware, actual larval digestion and extraction of shells until storage for subsequent geochemical analysis or observation. This protocol is applicable to shelly larvae of any species, once they are collected and brought to the laboratory. The goal of this preparation is to isolate each larval shell to perform individual geochemical analyses, instead of dissolving several specimens for bulk analysis. To do this, great care needs to be taken to the handling of the shells using ultra-pure solutions and acid-washed glassware to avoid chemical contamination of all kind. Reference: Becker, B.J., Fodrie, F.J., McMillan, P.A., Levin, L.A., 2005. Spatial and temporal variation in trace elemental fingerprints of mytilid mussel shells: a precursor to invertebrate larval tracking. Limnology and Oceanography, 50, 48-61. doi: 10.4319/lo.2005.50.1.0048
Seasonal Variations in Maternal Provisioning of Crepidula fornicata (Gastropoda): Fatty Acid Composition of Females, Embryos and Larvae
No full textInternational audienceRecruitment success of marine invertebrate populations not only depends on the number of recruits but also on their quality which affects their survival. In species characterized by a mixed development (encapsulated embryonic development and release of planktotrophic larvae), the offspring quality depends on both maternal provisioning and larval feeding. Here, we investigated potential changes of maternal provisioning over the whole reproductive period in a gastropod with a mixed development: Crepidula fornicata. In its introduction area, C. fornicata reproduces from February to October, which implies that both adults and larvae are exposed to different food availabilities. Maternal provisioning was assessed by measuring the fatty acid (FA) composition of females, encapsulated embryos and larvae, in February, May, July and September 2009. FA are essential resources for the development of embryos and larvae, and are key biomarkers of offspring quality. Our results showed differences in FA composition between muscles, visceral masses, and encapsulated embryos. In particular, FA composition of embryos was similar to that of the visceral mass. Seasonal variations in FA composition were observed: in the middle of the reproductive season (May and July), female tissues and embryos showed a higher proportion of polyunsaturated fatty acids and especially.3, as compared to the beginning and end of the reproductive season (February and September). This showed that through maternal provisioning the quality of C. fornicata offspring was higher in the middle of the reproductive season. Whether this would result in an increase of recruitment success and juvenile performance would require further investigations
Perturbative equation of state for a gas of anyons
No full textThe work of art in the age of its digitized reproduction Digitizing puts the finishing touches to reproductibility, which was already involved in mechanical and analogical techniques. Inspired by Walter Benjamin's aesthetic theories about that issue, we point out that digitizing changes deeply the relations between understanding and feeling, and our approach in terms of time and archives. These digital documents are considered as opus in a new meaning, as far as collective receiving conditions, but also the political author profile, are concerned with this tranformation. A complex situation is coming, with new creating possibilities, through traditional culture subversion, and towards new ways of publishing added-value
Meroplankton distribution and its relationship to coastal mesoscale hydrological structure in the northern Bay of Biscay (NE Atlantic)
No full textInternational audienceThe relationship between meroplankton distribution and spatio-temporal variabil- ity of coastal mesoscale hydrological structure was investigated in the northern Bay of Biscay, North-East Atlantic. For the three coastal polychaetes studied, i.e. Pectinaria koreni, Owenia fusiformis and Sabellaria alveolata, the highest larval abun- dances were sampled in low-salinity, low-density and high-temperature river plume waters. For two species (P. koreni and O. fusiformis), maximal abundances were observed in the surface and thermocline layers due to ontogenic migrations. Variance partitioning based on multiple regression and redundancy analyses was used to assess the relative roles played by the hydrological environment alone, the geographical space alone and their interactions, i.e. the spatial structure of the hydrological environment. These analyses demonstrate the key role played by the hydrological spatial structure in the distribution of larval abundances. The hydrological environment alone was insignificant, whereas geographical space alone explained a significant part of the variability in meroplankton distribution, probably in conjunction with ecological processes. For species whose benthic populations are spatially structured, the distribution and the size of adult popu- lations and the timing of spawning events can significantly affect larval distribution and dispersal
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