title: Getting into hot water: sick guppies frequent warmer thermal conditions.
abstract: Ectotherms depend on the environmental temperature for thermoregulation and exploit thermal regimes that optimise physiological functioning. They may also frequent warmer conditions to up-regulate their immune response against parasite infection and/or impede parasite development. This adaptive response, known as 'behavioural fever', has been documented in various taxa including insects, reptiles and fish, but only in response to endoparasite infections. Here, a choice chamber experiment was used to investigate the thermal preferences of a tropical freshwater fish, the Trinidadian guppy (Poecilia reticulata), when infected with a common helminth ectoparasite Gyrodactylus turnbulli, in female-only and mixed-sex shoals. The temperature tolerance of G. turnbulli was also investigated by monitoring parasite population trajectories on guppies maintained at a continuous 18, 24 or 32 °C. Regardless of shoal composition, infected fish frequented the 32 °C choice chamber more often than when uninfected, significantly increasing their mean temperature preference. Parasites maintained continuously at 32 °C decreased to extinction within 3 days, whereas mean parasite abundance increased on hosts incubated at 18 and 24 °C. We show for the first time that gyrodactylid-infected fish have a preference for warmer waters and speculate that sick fish exploit the upper thermal tolerances of their parasites to self medicate.
authors.affiliation: School of Biosciences, Cardiff University, Cardiff, CF10 3TL, UK.|Department of Life Sciences, Faculty of Science and Technology, University of the West Indies, Mona, Trinidad and Tobago.
authors.forename: Ryan S
authors.initials: RS
authors.lastname: Mohammed
authors.affiliation: School of Biosciences, Cardiff University, Cardiff, CF10 3TL, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Reynolds
authors.affiliation: School of Biosciences, Cardiff University, Cardiff, CF10 3TL, UK.
authors.forename: Joanna
authors.initials: J
authors.lastname: James
authors.affiliation: National Fisheries Services, Environment Agency, Brampton, Cambridgeshire, PE28 4NE, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: Williams
authors.affiliation: Department of Life Sciences, Faculty of Science and Technology, University of the West Indies, Mona, Trinidad and Tobago.
authors.forename: Azad
authors.initials: A
authors.lastname: Mohammed
authors.affiliation: Department of Life Sciences, Faculty of Science and Technology, University of the West Indies, Mona, Trinidad and Tobago.
authors.forename: Adesh
authors.initials: A
authors.lastname: Ramsubhag
authors.affiliation: School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
authors.forename: Cock
authors.initials: C
authors.lastname: van Oosterhout
authors.affiliation: School of Biosciences, Cardiff University, Cardiff, CF10 3TL, UK. cablej@cardiff.ac.uk.
authors.forename: Jo
authors.identifier: 0000-0002-8510-7055
authors.initials: J
authors.lastname: Cable
mesh_terms: D000818:Animals; D011036:Poecilia; D013696:Temperature; D014200:Trematoda; D014867:Water
chemical_list: D014867:Water
keywords: Behavioural fever; Climate change; Gyrodactylus; Thermal gradients; Trinidadian guppy