title: Increasing metabolic rate despite declining body weight in an adult parasitoid wasp.
abstract: Metabolic rate is a positive function of body weight, a rule valid for most organisms and the basis of several theories of metabolic ecology. For adult insects, however, the diversity of relationships between body mass and respiration remains unexplained. The aim of this study is to relate the respiratory metabolism of a parasitoid with body weight and foraging activity. We compared the metabolic rate of groups of starving and host-fed females of the parasitoid Eupelmus vuilleti recorded with respirometry for 7days, corresponding to the mean lifetime of starving females and over half of the lifetime of foraging females. The dynamics of carbohydrate, lipid and protein in the body of foraging females were quantified with biochemical techniques. Body mass and all body nutrients declined sharply from the first day onwards. By contrast, the CO2 produced and the O2 consumed increased steadily. Starving females showed the opposite trend, identifying foraging as the reason for the respiration increase of feeding females. Two complementary physiological processes explain the unexpected relationship between increasing metabolic rate and declining body weight. First, host hemolymph is a highly unbalanced food, and the excess nutrients (protein and carbohydrate) need to be voided, partially through excretion and partially through respiration. Second, a foraging young female produces eggs at an increasing rate during the first half of its lifetime, a process that also increases respiration. We posit that the time-varying metabolic rate contributions of the feeding and reproductive processes supplements the contribution of the structural mass and lead to the observed trend. We extend our explanations to other insect groups and discuss the potential for unification using Dynamic Energy Budget theory.
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS/Université François-Rabelais de Tours, Parc Grandmont, 37200 Tours, France; Institut Universitaire de France, UMR 7261, CNRS/Université François-Rabelais de Tours, Parc Grandmont, 37200 Tours, France. Electronic address: casas@univ-tours.fr.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Casas
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS/Université François-Rabelais de Tours, Parc Grandmont, 37200 Tours, France.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Body
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS/Université François-Rabelais de Tours, Parc Grandmont, 37200 Tours, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Gutzwiller
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS/Université François-Rabelais de Tours, Parc Grandmont, 37200 Tours, France.
authors.forename: David
authors.initials: D
authors.lastname: Giron
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS/Université François-Rabelais de Tours, Parc Grandmont, 37200 Tours, France.
authors.forename: Claudio R
authors.initials: CR
authors.lastname: Lazzari
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS/Université François-Rabelais de Tours, Parc Grandmont, 37200 Tours, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Pincebourde
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS/Université François-Rabelais de Tours, Parc Grandmont, 37200 Tours, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Richard
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS/Université François-Rabelais de Tours, Parc Grandmont, 37200 Tours, France.
authors.forename: Ana L
authors.initials: AL
authors.lastname: Llandres
mesh_terms: D000818:Animals; D001070:Appetitive Behavior / Q000502:physiology; D001481:Basal Metabolism; D001823:Body Composition; D001835:Body Weight; D002245:Carbon Dioxide / Q000378:metabolism; D001517:Coleoptera / Q000469:parasitology; D005247:Feeding Behavior; D005260:Female; D005508:Food Deprivation; D006458:Hemolymph / Q000378:metabolism; D009866:Oogenesis; D010101:Oxygen Consumption; D059467:Transcriptome; D014863:Wasps / Q000378:metabolism*
chemical_list: D002245:Carbon Dioxide
keywords: Dynamic Energy Budget (DEB); Ecological energetics; Host-feeding; Metabolic ecology; Parasitoids; Reserves; Respiratory Quotient (RQ); Respirometry; Starvation; Structural mass