title: Body temperature changes during simulated bacterial infection in a songbird: fever at night and hypothermia during the day.
abstract: Although fever (a closely regulated increase in body temperature in response to infection) typically is beneficial, it is energetically costly and may induce detrimentally high body temperatures. This can increase the susceptibility to energetic bottlenecks and risks of overheating in some organisms. Accordingly, it could be particularly interesting to study fever in small birds, which have comparatively high metabolic rates and high, variable body temperatures. We therefore investigated two aspects of fever and other sickness behaviours (circadian variation, dose dependence) in a small songbird, the zebra finch. We injected lipopolysaccharide (LPS) at the beginning of either the day or the night, and subsequently monitored body temperature, body mass change and food intake for the duration of the response. We found pronounced circadian variation in the body temperature response to LPS injection, manifested by (dose-dependent) hypothermia during the day but fever at night. This resulted in body temperature during the peak response being relatively similar during the day and night. Day-to-night differences might be explained in the context of circadian variation in body temperature: songbirds have a high daytime body temperature that is augmented by substantial heat production peaks during activity. This might require a trade-off between the benefit of fever and the risk of overheating. In contrast, at night, when body temperature is typically lower and less variable, fever can be used to mitigate infection. We suggest that the change in body temperature during infection in small songbirds is context dependent and regulated to promote survival according to individual demands at the time of infection.
authors.affiliation: Department of Biology, Lund University, Ecology Building, Lund SE-223 62, Sweden.
authors.forename: Sandra
authors.initials: S
authors.lastname: Sköld-Chiriac
authors.affiliation: Department of Biology, Lund University, Ecology Building, Lund SE-223 62, Sweden Andreas.Nord@biol.lu.se.
authors.forename: Andreas
authors.initials: A
authors.lastname: Nord
authors.affiliation: Department of Biology, Lund University, Ecology Building, Lund SE-223 62, Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Tobler
authors.affiliation: Department of Biology, Lund University, Ecology Building, Lund SE-223 62, Sweden.
authors.forename: Jan-Åke
authors.initials: JÅ
authors.lastname: Nilsson
authors.affiliation: Department of Biology, Lund University, Ecology Building, Lund SE-223 62, Sweden.
authors.forename: Dennis
authors.initials: D
authors.lastname: Hasselquist
mesh_terms: D000818:Animals; D001424:Bacterial Infections / Q000503:physiopathology / Q000662:veterinary*; D001715:Bird Diseases / Q000503:physiopathology*; D001831:Body Temperature / Q000502:physiology*; D001833:Body Temperature Regulation / Q000502:physiology; D001835:Body Weight; D002940:Circadian Rhythm; D004435:Eating; D005334:Fever / Q000503:physiopathology / Q000662:veterinary*; D008070:Lipopolysaccharides / Q000008:administration & dosage; D008297:Male; D020308:Songbirds / Q000502:physiology*
chemical_list: D008070:Lipopolysaccharides
keywords: Acute phase response; Circadian variation; Dose dependence; Heterothermy; LPS; Sickness behaviour; Taeniopygia guttata; Zebra finch