A Change of Heart in Birds: Cardiac Response to the Onset of Endothermy
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Authors
Killpack, Tess L.
Issue Date
2005
Type
Thesis
Language
en_US
Keywords
Alternative Title
Abstract
Precocial birds, like chickens, experience a large, rapid increase in
metabolism at hatching, with the 'physiological stressor" of the establishment
of endothermy. In post-prandial pythons, a comparable upregulation of
metabolism is accompanied by a rapid increase in heart mass, though in the
absence of other body growth. Therefore, we hypothesized that heart mass
would increase between 21-day paranatal and 21-day neonatal chickens with
the establishment of endothermy. We expected other body parts to grow little
or not at all in this 12-hour period. We tested this hypothesis on chickens
(Gallus domesticus, White Mountain Broiler) by measuring metabolic rate of
18 (18) and 19-day (19) prenates, 21-day paranates (21p), and 21-day
neonates (21 n) at 25°C and 35 °C. We dissected and massed the heart, yolk,
intestine, and yolk-free carcass, and measured culmen and tibiotarsus, of the
chickens at these stages and also of 16-day incubated embryos. Results of
our experiment confirmed the onset of endothermy between 21p and 21n;
neonates had higher metabolic rates at 25°C than 35 °C, while paranates did
not. The 53% increase between the ectothermic paranates and the
endothermic neonates was the most striking change in heart mass that we
observed. The most significant increases in intestine and body mass occurred
between 19 and 21 p, prior to the metabolic increase at the onset of
endothermy. These results could lead to insights into the ontogeny of
endothermy in mammals, including humans, and into the responses of these
animals to the physiological stressors that accompany these developmental
changes.
Description
vi, 33 p.
Citation
Publisher
Kalamazoo College
License
U.S. copyright laws protect this material. Commercial use or distribution of this material is not permitted without prior written permission of the copyright holder.