AJP - Regulatory, Integrative and Comparative Physiology, Vol 270, Issue 5 1051-R1058, Copyright © 1996 by American Physiological Society
Metabolic and hormonal changes during the molt of captive gray seals (Halichoerus grypus)
P. Boily
Department of Zoology, University of Guelph Ontario Canada.
Body mass, resting metabolic rates (RMRs), and serum thyroid hormones
concentrations of six captive gray seals (Halichoerus grypus) were measured
at regular intervals before, during, and after the annual molt. Changes in
body mass suggested that the animals had increased energy expenditures
during the last stage of the molt. These were associated with significantly
elevated RMRs during the molt, the increase being more pronounced in
juveniles ( < or = 53%) than in adults ( < or = 17%). The increase in
RMR probably reflects the cost of generating a new pelt or to sustain a
high skin temperature. Serum total and free thyroxine concentrations were
elevated for all animals during the molt, but only juveniles had elevated
serum triiodothyronine concentration. The increase in thyroid hormones
occurred only during the last stage of the molt, suggesting that the role
of thyroid hormones during the molt may be to sustain rapid hair growth in
the last stage of molt or to maintain elevated heat production, rather than
to initiate hair growth.
