1 Energetic costs in the relationship between bitterling and mussels in East Asia 2 3 Caroline Methling1, Karel Douda2, Huanzhang Liu3, Romain Rouchet1, Veronika Bartáková1, 4 Dan Yu3, Carl Smith1,4,5, Martin Reichard1* 5 6 1The Czech Academy of Sciences, Institute of Vertebrate Biology, Brno, Czech Republic 7 2Department of Zoology and Fisheries, Czech University of Life Sciences Prague, Prague, Czech 8 Republic 9 3The Key Lab of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese 10 Academy of Sciences, Wuhan, China 11 4Department of Ecology and Vertebrate Zoology, University of Łódź, Łódź, Poland 12 5School of Biology and Bell-Pettigrew Museum of Natural History, University of St Andrews, St 13 Andrews, UK 14 15 *Corresponding author: Martin Reichard, Institute of Vertebrate Biology, Academy of Sciences 16 of the Czech Republic, Květná 8, 603 65 Brno, Czech Republic; E-mail:
[email protected] 17 18 Running title: Energetic costs in bitterling-mussel relationship 1 19 Abstract 20 Bitterling fishes and unionid mussels are involved in a two-sided coevolutionary association. On 21 one side, bitterling exploit unionids by ovipositing in their gills. On the other side, unionids develop 22 via a larval stage (glochidium) that attach to fish gills. Both interactions are parasitic and expected 23 to have negative consequences for the host. Here we examined the effects of this association on the 24 metabolic rates of mussel and fish hosts by measuring oxygen uptake rates (MO2). Measurements 25 were performed on two widespread and broadly coexisting species; the rose bitterling Rhodeus 26 ocellatus and Chinese pond mussel Sinanodonta woodiana.