AJP - Regulatory, Integrative and Comparative Physiology, Vol 236, Issue 3 188-R197, Copyright © 1979 by American Physiological Society
Some aspects of temperature regulation in newborn harp seal pups
A. S. Blix, H. J. Grav and K. Ronald
Harp seals are born on the drifting ice of the North Atlantic Ocean during
arctic winter when temperatures of -20 degrees C, occasionally in
combination with wind of 10 m/s, might prevail for days. At birth the pups
lack subcutaneous blubber and the wet infantile fur has a conductance value
of 30.0 W . m-2 . degrees C-1, as compared with only 2.0 W . m-2 . degrees
C-1 when dry. While still wet immediately after birth the pups are
nevertheless able to retain body core temperature by shivering. This
activity leads to reduction of muscle fat and glycogen stores. Nonshivering
thermogenesis commences in thermogenic adipose tissue by virtue of loosely
coupled mitochondria. Thermogenic adipose tissue is found at birth both as
a subcutaneous layer along the back and as internal deposits around venous
plexuses in the neck, on the pericardium, on the kidneys, and the abdominal
walls. After about 3 days of suckling the subcutaneous adipose tissue loses
its thermogenic function being gradually transformed into blubber, whereas
the internal deposits persist at least until the pups venture into water at
the age of 3-4 wk.
