Warning: The magic method Iuem_Directory::__wakeup() must have public visibility in /web-space/www-iuem.univ-brest.fr/racine-lemar/lemar/wp-content/plugins/iuem_directory/iuem_directory.php on line 83
Agnès LEWDEN – Laboratoire LEMAR UMR 6539

Agnès LEWDEN

Ecophysiologie des oiseaux marins

Post-Doctorante ISblue
Université de Bretagne Occidentale

Affectation

Laboratoire LEMAR

Chibido

(version française disponible plus bas)

 

Profile

I am an eco-physiologist specialized in bird (penguins) energetics focusing on energy expenditure linked to thermoregulation. My research aims to understand heat exchange regulations between the organism and its environment but also within the organism (i.e. heterothermia) and the energetic consequences of the body/tissues temperature variations. Thus, I worked on thermoregulation processes in cold conditions with passerines wintering in Canada and on penguins spending foraging trips in cold water (see below).

In 2022, I obtained the international post-doc fellowship funding by ISblue (https://www.isblue.fr/en/) to work at the University of Brest Occidentale. My current projects aim to:

  • Investigate the redistribution of abiotic resources driven by breeding seabird from the land to the coast. Main collaborators: Aude Leynaert (CNRS), Anne Lorrain (IRD), Julien Thébault (UBO), Jill Sutton (UBO), Andréaz Dupoué (Ifremer)
  • Investigate the importance of snow surface for Arctic passerine. Main collaborators: François Vézina (Rimouski), Audrey Le Pogam (Rimouski)

Do not hesitate to contact me if you want to know more about my research projects.

Completed studies

Bird flight energetics (2018-2021)

Particularly demanding from an energetic point of view, flapping flight exhibits the highest rates of energy expenditure of any mode of locomotion (Norberg 1990 – Animal Flight). However, many of the techniques used to study avian aerodynamics, biomechanics and energetics within a laboratory setting are not easily transferable into the field. The aim of this project was to understand how indirect proxies of flight energetics can best act as indicators of metabolic rate and avian biomechanical flight performance, and thus increase our understanding of bird flight energetic in wild condition.

Related papers:

–  Lewden A, Askew GN. (Under review) How birds dissipate heat before, during and after flight

–  Lewden A, Evans A, Avery S, Bishop CM, Askew GN. (In prep.) Flight energetics in lovebirds (Agapornis personatus) measured in wind tunnel using three proxies of respirometry.

 

 King penguin (Aptenodytes patagonicus) thermoregulation in cold water (2013-2020) – Ph.D. degree

The energetic cost of foraging activities in King Penguin consists in reaching favourable areas, in realizing deep dives in search of fish and in resting in high latitude cold water. Several studies have shown that resting in cold water could represent a more expensive cost than realizing deep dives. This paradox is probably linked with contrasting thermoregulation processes. During daylight, a general hypothermia occurs and is believed to reduce energy expenditure. However, a re-warming to normothermia occurs at sunset and contributes to increase heat-loss during the night. We hypothesise an energetic conflict between thermoregulation and digestive processes. During daylight, the organism may be unable to assimilate the end product of prey digestion (free fatty acids – FFA) into the peripheral subcutaneous adipose tissues (SAT), because skin is no more blood perfused. During the night, re-warming and re-connecting to blood circulation peripheral tissues could be inevitable to enable the assimilation of FFA into the SAT.

Thus, we measured an increase of subcutaneous temperatures (used as a proxy of blood perfusion) in implanted penguins maintained in sea water tank in feeding condition (Lewden et al. 2017a) supporting this hypothesis. However, we also observed an increase of peripheral temperatures in the same birds during fasting time (Lewden et al. 2017b). Furthermore, the oxygen consumption rate of birds increased with fasting duration in water, while it was also higher when the flank tissue was warmer, indicating a thermoregulation cost due to greater perfusion. Fasting king penguins in water maintained peripheral perfusion probably to access subcutaneous fat stores. Hence, the observed normothermia in peripheral tissues of king penguins at sea, upon completion of a foraging bout, is likely explained by their nutritional needs: depositing FFA in subcutaneous tissues after profitable foraging (feeding condition) or mobilizing FFA to fuel metabolism, when foraging success was insufficient (fasting condition).

Related papers:

–  Lewden A, Nord A, Bonnet B, Chauvet F, Ancel A, McCafferty DJ 2020. Body surface rewarming in hypothermic and normothermic King penguins. Journal of Comparative Physiology B, 1-13

–  Lewden A, Bonnet B, Nord A. 2020 The metabolic cost of subcutaneous and abdominal rewarming in King Penguins after long-term immersion in cold water. Journal of Thermal Biology, 102638

–  Lewden A, Enstipp MR, Bonnet B, Bost C, Georges J-Y, Handrich Y 2017. Thermal strategies of king penguins during prolonged fasting in water. Journal of Experimental Biology 220(24), pp. 4600-4611

–  Lewden A, Enstipp MR, Picard B, Van Walsum T, Handrich Y 2017. High peripheral temperatures in king penguins while resting at sea:  thermoregulation versus  fat  deposition. Journal of Experimental

Biology 220(17), pp. 3084-3094

 

Cold acclimatization in Black-capped chickadees (Poecile atricapillus L.) (2009-2017) – M.Sc. degree

During Canadian winter, chickadees have to cope with harsh conditions marked by a decrease of daytime reducing their foraging activity with an increase of fasting time during the night, not to mention the heat lost induced by low temperature. However, although they cannot accumulate large fat reserve that would impair their ability to fly, Black-capped chickadees demonstrate an ability to survive temperature gradients (body temperature – air temperature) higher than 40°C.

Independently to social rank, all studied individuals showed similar metabolic performance (Lewden et al. 2012) with an increase of pectoralis muscle mass explaining an increase of maximal thermogenic capacity (Msum; Petit, Lewden and Vézina 2014). Furthermore, chickadees expressed intra-seasonal metabolic flexibility (Petit, Lewden and Vézina 2013) but also hypothermic events during daytime (Lewden et al. 2014) in aim to adjust their energy expenditures during winter. Finally for this small passerine, the plumage represents an efficient insulating barrier to maintain the high stable temperature (Lewden et al. 2017) characteristic of endotherms.

Related papers:

–  Lewden A, Nord A, Petit  M, Vézina  F 2017. Body temperature  responses  to  handling stress in wintering Black-capped Chickadees (Poecile atricapillus L.). Physiology & Behavior 179, pp. 49-54

–  Cortés PA, Petit M, Lewden A, Milbergue M, Vézina F 2015. Individual inconsistencies in basal and summit  metabolic  rate  highlight  flexibility  of  metabolic  performance  in  a  wintering  passerine. Journal  of Experimental Zoology Part A: Ecological Genetics and Physiology 323(3), pp. 179-190

–  Petit M, Lewden A, Vézina F 2014. How Does Flexibility in Body  Composition  Relate  to  Seasonal Changes in Metabolic Performance in a Small Passerine Wintering at Northern Latitude? Physiological and

Biochemical Zoology 87(4), pp. 539-549

–  Lewden A, Petit M, Milbergue M, Orio S, Vézina F 2014. Evidence of facultative daytime hypothermia in a small passerine wintering at northern latitudes. Ibis 156(2), pp. 321-329

–  Petit M, Lewden A, Vézina F 2013. Intra-Seasonal Flexibility in Avian  Metabolic  Performance Highlights the Uncoupling of Basal Metabolic Rate and Thermogenic Capacity. PLoS ONE 8(6), pp. 68292-

68292

–  Lewden A, Petit M, Vézina F. 2012. Dominant black-capped chickadees pay no maintenance energy costs for their wintering status and are not better at enduring cold than subordinate individuals. Journal of Comparative Physiology B 182(3), pp. 381-392

 

Biologist in Antarctica (2011-2013)

Related papers:

–  Delord  K,  Pinet  P,  Pinaud  D,  Barbraud  C,  De  Grissac  S,  Lewden  A,  Cherel  Y,  Weimerskirch H 2016. Species-specific foraging strategies and segregation mechanisms of sympatric Antarctic fulmarine petrels throughout the annual cycle. Ibis 158(3), pp. 569-586

– Lacoste-Garanger N, Lanshere J, Lewden A. 2013. Assembling  a  skeleton  of  an  Emperor  Penguin (Aptenodytes  forsteri)  in  Adelie  Land  (Antarctica):  interest  of  amphipods  in  the  bones  cleaning. Cahier d’Anatomie Comparée.

Présentation:

Après un master canadien étudiant la capacité d’acclimatation au froid de la mésange à tête noire (Poecile atricapillus), je suis partie hiverner en Antarctique en tant que biologiste/écologue. A mon retour, j’ai complété une thèse à l’Université de Strasbourg étudiant les stratégies de thermorégulation liées aux contraintes physiologiques et environnementales chez le manchot royal (Aptenodytes patagonicus). J’ai ensuite effectué un premier post-doctorat à l’Université de Leeds (Royaume-Uni) où j’ai travaillé pendant trois ans sur l’énergétique du vol des oiseaux en conditions expérimentales. Aujourd’hui je suis post-doctorante à l’Université de Brest Occidentale suite à l’obtention de la bourse « international post-doc fellowship » proposée par l’école universitaire de recherche ISblue (https://www.isblue.fr/).

Mes travaux de recherche visent à mesurer les échanges thermiques entre les individus et leurs environnements et d’en comprendre les effets sur leurs organismes, leurs dépenses énergétiques mais également sur leurs comportements et ultimement sur leurs descendants. Pour se faire, j’étudie des espèces antarctiques et arctiques dans leur milieu naturel et en condition de captivité en mesurant leurs températures corporelles, leurs métabolismes et d’autres paramètres physiologiques tels que le niveau de déshydratation, mais aussi leur succès reproducteur.