Physiological mechanisms underlying individual variation in tolerance of food deprivation in juvenile European sea bass, Dicentrarchus labrax

• Published in: Journal of Experimental Biology
• Main Authors: Mckenzie, David J., Vergnet, Alain, Chatain, Beatrice, Vandeputte, Marc, Desmarais, Erick, Steffensen, John F., Guinand, Bruno
• Other Authors: Ecologie des systèmes marins côtiers (Ecosym), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Aquaculture Languedoc-Roussillon (LALR), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Génétique Animale et Biologie Intégrative (GABI), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École Pratique des Hautes Études (EPHE), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Montpellier (UM)-Institut de recherche pour le développement IRD : UR226-Centre National de la Recherche Scientifique (CNRS), Marine Biological Section Copenhagen, Department of Biology Copenhagen, Faculty of Science Copenhagen, University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH)-Faculty of Science Copenhagen, University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: Ammonia excretion; Ammonia quotient; Energetic strategy; Respirometry; Routine metabolic rate; Specific dynamic action; NITROGENOUS WASTE EXCRETION; RESPIRATORY GAS-EXCHANGE; CATFISH SILURUS-MERIDIONALIS; GASTROINTESTINAL BLOOD-FLOW; TROUT ONCORHYNCHUS-MYKISS; STANDARD METABOLIC-RATES; SALMON SALMO-SALAR; RAINBOW-TROUT; OXYGEN-CONSUMPTION; FUEL USAGE; [SDV]Life Sciences [q-bio]; Salmo salar
• Online Access: https://hal.science/hal-01194097; https://hal.science/hal-01194097/document; https://hal.science/hal-01194097/file/3283.pdf; https://doi.org/10.1242/jeb.101857

Although food deprivation is a major ecological pressure in fishes, there is wide individual variation in tolerance of fasting, whose mechanistic bases are poorly understood. Two thousand individually tagged juvenile European sea bass were submitted to two 'fasting/feeding' cycles each comprising 3 weeks of food deprivation followed by 3 weeks of ad libitum feeding at 25 degrees C. Rates of mass loss during the two fasting periods were averaged for each individual to calculate a population mean. Extreme fasting tolerant (FT) and sensitive (FS) phenotypes were identified that were at least one and a half standard deviations, on opposing sides, from this mean. Respirometry was used to investigate two main hypotheses: (1) tolerance of food deprivation reflects lower mass-corrected routine metabolic rate (RMR) in FT phenotypes when fasting, and (2) tolerance reflects differences in substrate utilisation; FT phenotypes use relatively less proteins as metabolic fuels during fasting, measured as their ammonia quotient (AQ), the simultaneous ratio of ammonia excretion to RMR. There was no difference in mean RMR between FT and FS over 7 days fasting, being 6.70 +/- 0.24 mmol h(-1) fish(-1) (mean +/- s.e.m., N=18) versus 6.76 +/- 0.22 mmol h(-1) fish(-1) (N=17), respectively, when corrected to a body mass of 130 g. For any given RMR, however, the FT lost mass at a significantly lower rate than FS, overall 7-day average being 0.72 +/- 0.05 versus 0.90 +/- 0.05 g day(-1) fish(-1), respectively (P<0.01, t-test). At 20 h after receiving a ration equivalent to 2% body mass as food pellets, ammonia excretion and simultaneous RMR were elevated and similar in FT and FS, with AQs of 0.105 +/- 0.009 and 0.089 +/- 0.007, respectively. At the end of the period of fasting, ammonia excretion and RMR had fallen in both phenotypes, but AQ was significantly lower in FT than FS, being 0.038 +/- 0.004 versus 0.061 +/- 0.005, respectively (P<0.001, t-test). There was a direct linear relationship between individual fasted AQ and rate of ...