title: The trade-off between heat tolerance and metabolic cost drives the bimodal life strategy at the air-water interface.
abstract: The principle of oxygen and capacity limitation of thermal tolerance in ectotherms suggests that the long-term upper limits of an organism's thermal niche are equivalent to the upper limits of the organism's functional capacity for oxygen provision to tissues. Air-breathing ectotherms show wider thermal tolerances, since they can take advantage of the higher availability of oxygen in air than in water. Bimodal species move from aquatic to aerial media and switch between habitats in response to environmental variations such as cyclical or anomalous temperature fluctuations. Here we tested the prediction that bimodal species cope better with thermal stress than truly aquatic species using the crab Pachygrapsus marmoratus as a model species. When in water, oxygen consumption rates of P. marmoratus acutely rise during warming. Beyond a temperature threshold of 23 °C the crab's aerobic metabolism in air remains lower than in water. In parallel, the haemolymph oxygen partial pressure of submerged animals progressive decreases during warming, while it remains low but constant during emersion. Our results demonstrate the ability of a bimodal breathing ectotherm to extend its thermal tolerance during air-breathing, suggesting that there are temperature-related physiological benefits during the evolution of the bimodal life style.
authors.affiliation: King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Thuwal, 23955-6900, Saudi Arabia.|Department of Biology, University of Florence, Sesto Fiorentino, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Fusi
authors.affiliation: Department of Biology, University of Florence, Sesto Fiorentino, Italy.|The Swire Institute of Marine Science and the School of Biological Sciences, the University of Hong Kong, Pokfulam Road, Hong Kong.
authors.forename: Stefano
authors.initials: S
authors.lastname: Cannicci
authors.affiliation: King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Thuwal, 23955-6900, Saudi Arabia.
authors.forename: Daniele
authors.initials: D
authors.lastname: Daffonchio
authors.affiliation: Department of Zoology and Entomology, Rhodes University, Grahamstown, Africa.
authors.forename: Bruce
authors.initials: B
authors.lastname: Mostert
authors.affiliation: Department Integrative Ecophysiology, Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Hans-Otto
authors.initials: HO
authors.lastname: Pörtner
authors.affiliation: Department Integrative Ecophysiology, Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Folco
authors.initials: F
authors.lastname: Giomi
mesh_terms: D000388:Air; D000818:Animals; D003386:Brachyura; D004734:Energy Metabolism; D005260:Female; D006458:Hemolymph / Q000378:metabolism; D006358:Hot Temperature; D008297:Male; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D010313:Partial Pressure; D000071436:Thermotolerance; D014867:Water
chemical_list: D014867:Water; D010100:Oxygen