title: Blood flow for bone remodelling correlates with locomotion in living and extinct birds.
abstract: Nutrient arteries enter limb bones through discrete foramina on the shafts. They are required for bone remodelling in response to mechanical loading and dynamic forces imposed by locomotion. The cross-sectional area of the nutrient foramen of the femur represents an index of blood flow rate to the shaft and thus provides insight into the animal's level of activity. Morphometric data on femoral length, mass and foramen size from 100 extant bird species and eight extinct moa species were analysed allometrically and phylogenetically. The nutrient foramen blood flow index (Qi) and femur mass (Mf) increase with body mass (Mb). At 1 kg body mass, cursorial species have approximately 2.1 times higher Qi and 1.9 times heavier Mf than volant species. The scaling of Qi on Mf is independent of the primary mode of locomotion, but the ratio Qi/Mf decreases significantly in larger birds, although absolute Qi increases. The overall avian equation for Qi on Mb is not significantly different from previous data from mammals, but when differences in blood pressure are accounted for, estimated blood flow to the femur is approximately 1.9 times higher in cursorial birds than in mammals, possibly in relation to bipedalism and quadrupedalism, respectively. Femoral bone blood flow in both endothermic groups is estimated to be 50-100 times higher than in ectothermic reptiles.
authors.affiliation: School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia.
authors.forename: Georgina H
authors.initials: GH
authors.lastname: Allan
authors.affiliation: School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia.
authors.forename: Phillip
authors.initials: P
authors.lastname: Cassey
authors.affiliation: School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia.
authors.forename: Edward P
authors.initials: EP
authors.lastname: Snelling
authors.affiliation: School of Anatomy, Physiology and Human Biology, The University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Shane K
authors.initials: SK
authors.lastname: Maloney
authors.affiliation: School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia roger.seymour@adelaide.edu.au.
authors.forename: Roger S
authors.initials: RS
authors.lastname: Seymour
mesh_terms: D000818:Animals; D001717:Birds / Q000033:anatomy & histology* / Q000502:physiology*; D049628:Body Size; D016723:Bone Remodeling; D005269:Femur / Q000098:blood supply* / Q000502:physiology*; D005426:Flight, Animal; D005580:Fossils / Q000033:anatomy & histology; D008124:Locomotion; D009929:Organ Size; D010802:Phylogeny; D012039:Regional Blood Flow; D016138:Walking
keywords: Allometry; Bird; Blood flow; Bone remodelling; Locomotion; Nutrient foramen