title: Functional capacities of marsupial hearts: size and mitochondrial parameters indicate higher aerobic capabilities than generally seen in placental mammals.
abstract: This study of marsupial hearts explored the aerobic capacities of this group of mammals; recent information suggests that marsupials possess higher aerobic abilities than previously accepted. Characteristics such as heart mass, mitochondrial features and capillary parameters were examined. A comprehensive study of the heart of red kangaroos was included because of the high maximum oxygen consumption of this species. Goats were also included as a reference placental mammal. Marsupials have a heart that is generally larger than that of placentals. The allometric equation for the relationship between heart mass and body mass for marsupials was M(h)=7.5M(b)(0.944) (M(h) in g and M(b) in kg); the equivalent equation for placental mammals was M(h)=6.0M(b)(0.97). Mitochondrial volume density and inner mitochondrial surface density do not differ between the two mammal groups; although capillary parameters indicated a lower capillary volume in marsupials. Heart size appears to be the major difference between the two groups. The overall pattern seen in marsupials is similar to that of "athletic" placentals and indicates a relatively high aerobic potential.
authors.affiliation: School of Biological, Earth and Environmental Sciences, University of New South Wales, 2052, Sydney, NSW, Australia. t.dawson@unsw.edu.au
authors.forename: T J
authors.initials: TJ
authors.lastname: Dawson
authors.forename: K N
authors.initials: KN
authors.lastname: Webster
authors.forename: B
authors.initials: B
authors.lastname: Mifsud
authors.forename: E
authors.initials: E
authors.lastname: Raad
authors.forename: E
authors.initials: E
authors.lastname: Lee
authors.forename: A D
authors.initials: AD
authors.lastname: Needham
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight / Q000502:physiology; D002196:Capillaries / Q000502:physiology / Q000648:ultrastructure; D006041:Goats / Q000033:anatomy & histology / Q000502:physiology; D006321:Heart / Q000033:anatomy & histology / Q000502:physiology*; D006325:Heart Atria / Q000033:anatomy & histology / Q000648:ultrastructure; D006346:Heart Septum / Q000502:physiology / Q000648:ultrastructure; D006352:Heart Ventricles / Q000648:ultrastructure; D008394:Marsupialia / Q000502:physiology*; D008854:Microscopy, Electron; D008929:Mitochondria, Heart / Q000502:physiology* / Q000648:ultrastructure; D009206:Myocardium / Q000166:cytology / Q000648:ultrastructure; D009929:Organ Size / Q000502:physiology; D016276:Ventricular Function