title: Encystment of parasitic freshwater pearl mussel (Margaritifera margaritifera) larvae coincides with increased metabolic rate and haematocrit in juvenile brown trout (Salmo trutta).
abstract: Gill parasites on fish are likely to negatively influence their host by inhibiting respiration, oxygen transport capacity and overall fitness. The glochidia larvae of the endangered freshwater pearl mussel (FPM, Margaritifera margaritifera (Linnaeus, 1758)) are obligate parasites on the gills of juvenile salmonid fish. We investigated the effects of FPM glochidia encystment on the metabolism and haematology of brown trout (Salmo trutta Linnaeus, 1758). Specifically, we measured whole-animal oxygen uptake rates at rest and following an exhaustive exercise protocol using intermittent flow-through respirometry, as well as haematocrit, in infested and uninfested trout. Glochidia encystment significantly affected whole-animal metabolic rate, as infested trout exhibited higher standard and maximum metabolic rates. Furthermore, glochidia-infested trout also had elevated levels of haematocrit. The combination of an increased metabolism and haematocrit in infested fish indicates that glochidia encystment has a physiological effect on the trout, perhaps as a compensatory response to the potential respiratory stress caused by the glochidia. When relating glochidia load to metabolism and haematocrit, fish with low numbers of encysted glochidia were the ones with particularly elevated metabolism and haematocrit. Standard metabolic rate decreased with substantial glochidia loads towards levels similar to those of uninfested fish. This suggests that initial effects visible at low levels of encystment may be countered by additional physiological effects at high loads, e.g. potential changes in energy utilization, and also that high numbers of glochidia may restrict oxygen uptake by the gills.
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE 413 90, Gothenburg, Sweden.|Department for Environmental and Life Sciences, Karlstad University, SE 651 88, Karlstad, Sweden.
authors.forename: Karl
authors.initials: K
authors.lastname: Filipsson
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE 413 90, Gothenburg, Sweden.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Brijs
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE 413 90, Gothenburg, Sweden.
authors.forename: Joacim
authors.initials: J
authors.lastname: Näslund
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE 413 90, Gothenburg, Sweden.|Swedish Anglers Association, Sjölyckan 6, SE 416 55, Gothenburg, Sweden.
authors.forename: Niklas
authors.initials: N
authors.lastname: Wengström
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE 413 90, Gothenburg, Sweden.
authors.forename: Marie
authors.initials: M
authors.lastname: Adamsson
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE 413 90, Gothenburg, Sweden.|Laboratoire Évolution & Diversité Biologique (EDB UMR 5174), CNRS, Université de Toulouse, Toulouse, France.
authors.forename: Libor
authors.initials: L
authors.lastname: Závorka
authors.affiliation: Department for Environmental and Life Sciences, Karlstad University, SE 651 88, Karlstad, Sweden.
authors.forename: E Martin
authors.initials: EM
authors.lastname: Österling
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE 413 90, Gothenburg, Sweden. johan.hojesjo@bioenv.gu.se.
authors.forename: Johan
authors.initials: J
authors.lastname: Höjesjö
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000502:physiology*; D005393:Fish Diseases / Q000469:parasitology*; D005880:Gills / Q000469:parasitology; D006400:Hematocrit; D007814:Larva / Q000502:physiology; D010273:Parasitic Diseases, Animal / Q000469:parasitology*; D014337:Trout / Q000097:blood / Q000378:metabolism* / Q000469:parasitology*
keywords: Glochidia; Haematocrit; Host; Margaritifera; Metabolic rate; Parasite