Écologie de la reproduction et de la migration du pluvier bronzé, (Pluvialis dominica) nichant en arctique

RÉSUMÉ : Les changements globaux s'accélèrent et bouleversent le monde du vivant. Ces changements ont des répercussions sur l'abondance et la répartition de plusieurs espèces, en particulier les espèces migratrices. Les animaux migrateurs ont des particularités dont il faut tenir compte pour espérer identifier les facteurs responsables des changements d'effectifs de population. Ils utilisent souvent de grandes étendues spatiales durant leur cycle de vie annuel et fréquentent différents types d'habitats le long de leur corridor de migration. Ainsi, ils vont s'insérer temporairement dans des communautés écologiques distantes qui sont soumises à des changements de nature et d'intensité différentes. L'étude des relations trophiques indirectes, de la connectivité migratoire et des interactions saisonnières est importante afin d'améliorer notre compréhension de la dynamique de population des espèces migratrices et pour mettre en place des mesures de conservation adéquates. Ces trois concepts demeurent néanmoins peu étudiés chez la majorité des migrateurs. Cette thèse aborde ces thèmes en utilisant les oiseaux de rivage (limicoles) comme modèle d'étude. Les limicoles sont un groupe d'oiseaux migrateurs présentant de grands défis de conservation. Au Canada, près de 80 % des populations sont en déclin dont les causes restent incertaines et probablement multiples. Plusieurs espèces de limicoles nichent dans l'Arctique, où les changements climatiques sont très marqués. Les thèmes abordés dans cette thèse portent principalement sur la reproduction et la migration d'une espèce de limicole nichant dans l'Arctique, le Pluvier bronzé (Pluvialis dominica). Les objectifs spécifiques de la thèse sont de : 1- Quantifier la relation trophique indirecte entre des espèces de proies migratrices durant leur reproduction dans un écosystème arctique (oies des neiges (Anser caerulescens) et limicoles). 2- Décrire l'utilisation de l'espace et quantifier la connectivité migratoire à l'échelle de l'aire de répartition des Pluviers bronzés en considérant à la fois le temps et l'espace. 3- Relier la phénologie de la migration des individus avec la phénologie de la disponibilité de leur habitat de reproduction chez le Pluvier bronzé. Dans le premier chapitre, nous avons constaté qu'une colonie d'oies avait une forte influence sur la répartition spatiale des prédateurs et oiseaux de rivage. La présence de prédateurs de nids diminuait, tandis que la présence de pluviers bronzés nicheurs augmentait avec la distance à la colonie d'oies. De plus, le risque de prédation des nids de limicole diminuait avec la distance à la colonie. La densité des lemmings, proies fortement consommées par les prédateurs, modulait la force de ces effets indirects. Les oies affectent donc négativement les oiseaux de rivage via le partage de prédateurs communs. Dans le deuxième chapitre, le suivi de Pluviers bronzés pendant leur cycle annuel nous a permis de conclure que la connectivité migratoire est relativement faible chez cette espèce, puisque les individus provenant de sites de reproduction éloignés se retrouvent dans les mêmes secteurs pendant la majeure partie de la période non reproductrice. Ceci suggère que les populations reproductrices devraient être touchées de façon similaire par des perturbations ou changements survenant sur plusieurs haltes migratoires et aires d'hivernage communes. Le troisième chapitre montre que la phénologie de la dernière partie de la migration printanière est reliée à la phénologie moyenne de la fonte de la neige sur les sites de reproduction des Pluviers bronzés, plutôt qu'à la distance de migration restante pour rejoindre le site de reproduction ou la durée d'arrêt à la halte migratoire. Cela supporte l'hypothèse qu'une partie du calendrier migratoire des individus est adaptée à la phénologie de la disponibilité des sites de reproduction. Globalement, nos travaux démontrent que des changements qui s'opèrent dans des écosystèmes distants peuvent entraîner des cascades spatiales via des interactions trophiques indirectes entre des espèces mi ratrices se reproduisant en sympatrie dans l'Arctique. De plus, des changements survenant à des moments et des endroits très spécifiques peuvent avoir des effets sur toutes les populations reproductrices d'une espèce ayant une vaste répartition géographique. Finalement, le réchauffement climatique pourrait causer une pression de sélection très variable sur le calendrier de migration d'oiseaux qui partagent les mêmes haltes migratoires. Globalement, nos résultats contribuent à améliorer notre capacité à expliquer et prévoir l'effet des changements globaux sur les espèces migratrices. -- Mot(s) clé(s) en français : Interactions indirectes, migration, connectivité migratoire, phénologie, oiseau de rivages. -- ABSTRACT : Global changes are acceleratating and disrupt the living world. These major climatic and environmental changes have repercussions on the abundance and distribution of several species, especially migratory species. Migratory animals have particularities that must be taken into account in order to hope to identify the factors responsible for changes in population numbers. They often use large spatial areas during their annual life cycle and frequent different types of habitats along their migration corridor. Thus, they will temporarily fit into distant ecological communities that are subject to changes of different nature and intensity. The study of indirect trophic relationships, migratory connectivity and seasonal interactions is important to improve our understanding of the population dynamics of migratory species and to put in place adequate conservation measures. However, these three concepts remain little studied in the majority of migrants. This thesis addresses these themes using shorebirds (waders) as a study model. Shorebirds are a group of migratory birds presenting great conservation challenges. In Canada, nearly 80% of populations are in decline, the causes of which remain uncertain and probably multiple. Several species of waders nest in the Arctic, where climate change is acute. The topics addressed in this thesis relate mainly to the reproduction and migration of a shorebird species nesting in the Arctic, the American Golden-Plover (Pluvialis dominica). The specific objectives of the thesis are to: 1- Quantify the indirect trophic relationship between migratory prey species during their reproduction in an arctic ecosystem (snow geese [Anser caerulescens] and waders, particularly the American Golden-Plover). 2-Describe spatial use and quantify migratory connectivity across the breeding range American Golden-Plovers, considering both time and space. 3- Link the phenology of the migration of individuals with the phenology of the availability of their breeding habitat in American Golden Plover. In the first chapter, we found that a colony of geese had a strong influence on the spatial distribution of predators and shorebirds. The presence of nest predators decreased, while the presence of nesting American Golden-Plovers increased with distance from the goose colony. In addition, the risk of shorebirds nest predation decreased with distance from the colony. The density of lemmings, prey highly consumed by predators, modulated the strength of these indirect effects. Geese therefore negatively affect shorebirds through the sharing of common predators. In the second chapter, the monitoring of American Golden-Plovers during their annual cycle allowed us to conclude that the migratory connectivity is relatively low in this species because individuals coming from geographically separated breeding site were found in the same areas during most of the non-breeding period. This suggests that breeding populations should be similarly affected by disturbances or changes occurring at several common stopover and wintering areas. The third chapter demonstrates that the phenology of the latter part of the spring migration is related to the average snowmelt phenology at American Golden-Plover breeding sites, rather than to the remaining distance to reach their breeding site or to the duration of the stopover site. This supports the hypothesis that part of the migratory calendar of individuals is adapted to the phenology of the availability of breeding sites. Overall, this work demonstrates that changes in distant ecosystems can drive spatial cascades via indirect trophic interactions between sympatrically breeding migratory species in the Arctic. In addition, changes occurring at very specific times and places can affect all breeding populations of a species with a wide geographic distribution. Finally, global warming could cause highly variable selection pressure on the migration schedule of birds that share the same migratory stopovers. Overall, our results contribute to improving our ability to explain and predict he effect of global changes on migratory species. -- Mot(s) clé(s) en anglais : Indirect interactions, migration, migratory connectivity, phenology, shorebird

Transcriptomic analysis of the exit from dormancy of Aspergillus fumigatus conidia

<p>Abstract</p> <p>Background</p> <p>Establishment of aspergillosis is depending upon the exit from dormancy and germination of the conidia of <it>Aspergillus fumigatus </it>in the lung. To gain an understanding of the molecular mechanisms underlying the early steps of conidial germination, we undertook a transcriptomic analysis using macroarrays constructed with PCR fragments from > 3,000 genes (around one third of the annotated <it>A</it>. <it>fumigatus </it>genome).</p> <p>Results</p> <p>Major results of this analysis are the following: (i) conidia stored pre-packaged mRNAs transcripts (27% of genes have transcripts in the resting conidia; (ii) incubation at 37°C in a nutritive medium induced up- and down-regulation of genes: 19% of the total number of genes deposited on the array were up-regulated whereas 22% of the genes with pre-packaged mRNA in the resting conidia were down-regulated; (iii) most modifications were seen during the first 30 min of germination whereas very little modification of gene expression occurred during the following hour; (iv) one-year old conidia and one-week old conidia behaved similarly at transcriptional level.</p> <p>Conclusion</p> <p>Transcriptomic data indicate that the exit from dormancy is associated with a shift from a fermentative metabolism to a respiratory metabolism as well as a trend toward immediate protein synthesis.</p

CMB and SZ effect separation with Constrained Internal Linear Combinations

The `Internal Linear Combination' (ILC) component separation method has been extensively used on the data of the WMAP space mission, to extract a single component, the CMB, from the WMAP multifrequency data. We extend the ILC approach for reconstructing millimeter astrophysical emissions beyond the CMB alone. In particular, we construct a Constrained ILC to extract clean maps of both the CMB or the thermal Sunyaev Zeldovich (SZ) effect, with vanishing contamination from the other. The performance of the Constrained ILC is tested on simulations of Planck mission observations, for which we successfully reconstruct independent estimates of the CMB and of the thermal SZ.Comment: 7 pages, 3 figures, submitted to MNRA

Changes in physiological tremor associated with an epileptic seizure: a case report

<p>Abstract</p> <p>Introduction</p> <p>Epileptic seizures are associated with motor, sensory, somatosensory or autonomic symptoms that have all been described in varying detail over the years. Of interest in the present report is a case of normal physiological tremor, which to date has never been evaluated prior to and during an epileptic seizure. In fact, there is only anecdotal mention of pre-ictal and ictal changes in clinically noticeable tremor in the literature.</p> <p>Case presentation</p> <p>Our patient was a left-handed, 27-year-old Caucasian woman diagnosed seven years previously with partial epileptic seizures, secondarily generalized. Physiological tremor was measured simultaneously on the index finger of both hands of our patient. Electromyography as well as heart rate and respiration were also monitored. A previously performed electroencephalography examination revealed abnormal oscillations focalized to the left primary somatosensory cortex. She was also diagnosed with left frontal neuronal heterotopias. We detected subclinical changes in tremor characteristics, such as amplitude, median power frequency and power dispersion, contralateral to the localization of epileptic activity. Tremor characteristics remained relatively steady ipsilateral to the localization of the epileptic activity.</p> <p>Conclusions</p> <p>Changes in physiological tremor characteristics should be considered as another possible pre-ictal or ictal manifestation. We propose that the network associated with physiological tremor might be more sensitive to abnormal oscillations generated within the central nervous system by epileptic activity from certain structures.</p

Cross-validation of ELISA and a portable surface plasmon resonance instrument for IgG antibody serology with SARS-CoV-2 positive individuals.

We report on the development of surface plasmon resonance (SPR) sensors and matching ELISAs for the detection of nucleocapsid and spike antibodies specific to the novel coronavirus 2019 (SARS-CoV-2) in human serum, plasma and dried blood spots (DBS)

Unexpected diversity in socially synchronized rhythms of shorebirds

The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment1, 2, 3, 4. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions1, 5, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators6, 7, 8, 9, 10. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring)6, 7, 8, 9, 11. The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood5, 6, 7, 9. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization12 where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within- and between-species diversity in incubation rhythms. Between species, the median length of one parent’s incubation bout varied from 1–19 h, whereas period length—the time in which a parent’s probability to incubate cycles once between its highest and lowest value—varied from 6–43 h. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h light–dark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity5, 6, 7, 9. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms

The Planck milestone

International audiencePlanck, a European Space Agency satellite to be launched in 2007, is dedicated to surveying the full sky at sub-millimetre and millimetre wavelength. The primary goal of the mission is the final mapping of the Cosmic Microwave Background Anisotropies (CMBA). With an angular resolution of 5 arcmin and a sensitivity of Δ TCMB/ TCMB=2×10 -6, the Planck mission will be about 1000 times more sensitive than COBE-DMR and at least 20 times more than WMAP. Planck has also very good capabilites for measurements of polarization, although it will not exhaust the information contained in the CMBA polarization pattern. Two instruments share the Planck focal plane; the High Frequency Instrument (HFI) covers the wavelength ranging from 300 μm to 3 mm by using 48 bolometers cooled to 100 mK. This instrument is realized by an international collaboration, led by the IAS at Orsay. The other part of the relevant electromagnetic spectrum is covered by the Low Frequency Instrument (LFI) using HEMT radiometers cooled at 18 K and realized by a consortium led by the CNR in Milano. The first part of this article presents expected results of Planck on CMBA, both in intensity and polarization. In a second part, the global design of the Planck mission will be presented. We describe in particular the implications of Planck scientific goals on the instruments design, and especially on HFI that is the most sensitive Planck instrument. To cite this article: F.R. Bouchet et al., C. R. Physique 4 (2003)

Salt marsh width positively affects the occurrence of Least and Pectoral Sandpipers in the St. Lawrence River Estuary during fall migration

Salt marshes are vulnerable to climate change-associated sea-level rise and storm-induced surges. Their degradation will likely affect shorebirds relying on this ecosystem. Least Sandpiper (Calidris minutilla) and Pectoral Sandpiper (Calidris melanotos) migrating along coastline habitats typically use salt marshes to rest and replenish their body reserves. Our objective was to test if width of the different vegetation zones within salt marshes affects the occurrence of Least and Pectoral Sandpipers stopping along the St. Lawrence River Estuary, Quebec, Canada, during fall migration. We established 26 survey sites, each 600 m in length, along the shoreline. Shorebird surveys were conducted in 2011 and 2012. We characterized salt marshes by measuring the width of each vegetation zone (lower marsh and upper marsh). We analyzed shorebird presence/not detected data with generalized estimating equations to test the predictions that occurrence of Least Sandpipers and Pectoral Sandpipers increases with width of both the lower and upper marsh. Upper marsh width was positively associated with probability of occurrence in each species. Our results highlight the importance of protecting the integrity of salt marshes for these two species. In the St. Lawrence River Estuary, where landward migration of salt marshes is no longer possible (coastal squeeze), effective management of shorelines is much needed. Otherwise, salt marshes and these two species could be locally jeopardized