Determination of water balance maintenance in Orcinus orca and Tursiops truncatus using oxygen isotopes

• Published in: Journal of Experimental Biology
• Main Authors: Séon, Nicolas, Brasseur, Isabelle, Scala, Christopher, Tacail, Théo, Catteau, Sidonie, Fourel, François, Vincent, Peggy, Lécuyer, Christophe, Suan, Guillaume, Charbonnier, Sylvain, Vinçon-Laugier, Arnauld, Amiot, Romain
• Other Authors: Centre de Recherche en Paléontologie - Paris (CR2P), Muséum national d'Histoire naturelle (MNHN)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), ANR-18-CE31-0020,Oxymore,Rapports isotopiques de l'oxygène des océans mésozoïques revisités(2018)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: [SDV]Life Sciences [q-bio]; Orca; Orcinus orca
• Online Access: https://mnhn.hal.science/mnhn-04266511; https://doi.org/10.1242/jeb.245648

International audience The secondary adaptation of Cetacea to a fully marine lifestyle raises the question of their ability to maintain their water balance in a hyperosmotic environment. Cetacea have access to four potential sources of water: surrounding salt oceanic water, dietary free water, metabolic water and inhaled water vapor to a lesser degree. Here, we measured the 18O/16O oxygen isotope ratio of blood plasma from thirteen specimens belonging to two species of Cetacea raised under human care (four killer whales Orcinus orca, nine common bottlenose dolphins Tursiops truncatus) to investigate and quantify the contribution of preformed water (dietary free water, surrounding salt oceanic water) and metabolic water to Cetacea body water using a box-modelling approach. The oxygen isotope composition of Cetacea blood plasmas indicates that dietary free water and metabolic water contribute to more than 90% of the total water inputs in weight for cetaceans, with the remaining 10% consisting of inhaled water vapor and surrounding water accidentally ingested or absorbed through the skin. Moreover, the contribution of metabolic water appears to be more important in organisms with a more lipid-rich diet. Beyond these physiological and conservation biology implications, this study opens up questions that need to be addressed, such as the applicability of the oxygen isotope composition of cetacean body fluids and skeletal elements as an environmental proxy of the oxygen isotope composition of present and past marine waters.