title: Post-hatch heat warms adult beaks: irreversible physiological plasticity in Japanese quail.
abstract: Across taxa, the early rearing environment contributes to adult morphological and physiological variation. For example, in birds, environmental temperature plays a key role in shaping bill size and clinal trends across latitudinal/thermal gradients. Such patterns support the role of the bill as a thermal window and in thermal balance. It remains unknown whether bill size and thermal function are reversibly plastic. We raised Japanese quail in warm (30°C) or cold (15°C) environments and then at a common intermediate temperature. We predicted that birds raised in cold temperatures would develop smaller bills than warm-reared individuals, and that regulation of blood flow to the bill in response to changing temperatures would parallel the bill's role in thermal balance. Cold-reared birds developed shorter bills, although bill size exhibited 'catch-up' growth once adults were placed at a common temperature. Despite having lived in a common thermal environment as adults, individuals that were initially reared in the warmth had higher bill surface temperatures than cold-reared individuals, particularly under cold conditions. This suggests that blood vessel density and/or the control over blood flow in the bill retained a memory of early thermal ontogeny. We conclude that post-hatch temperature reversibly affects adult bill morphology but irreversibly influences the thermal physiological role of bills and may play an underappreciated role in avian energetics.
authors.affiliation: Department of Biology, Trent University, Peterborough, Ontario, Canada K9J 7B8. garyburness@trentu.ca
authors.forename: Gary
authors.initials: G
authors.lastname: Burness
authors.forename: Jacqueline R
authors.initials: JR
authors.lastname: Huard
authors.forename: Emily
authors.initials: E
authors.lastname: Malcolm
authors.forename: Glenn J
authors.initials: GJ
authors.lastname: Tattersall
mesh_terms: D000818:Animals; D001502:Beak / Q000033:anatomy & histology* / Q000254:growth & development / Q000502:physiology*; D001833:Body Temperature Regulation; D003370:Coturnix / Q000033:anatomy & histology* / Q000254:growth & development / Q000502:physiology*; D005260:Female; D008297:Male; D013643:Tarsus, Animal / Q000033:anatomy & histology / Q000254:growth & development; D013696:Temperature
keywords: Allen's rule; ontogeny; phenotypic plasticity; thermal window