AJP - Regulatory, Integrative and Comparative Physiology, Vol 255, Issue 5 760-R767, Copyright © 1988 by American Physiological Society
Allometry of the kidney: implications for the ontogeny of osmoregulation
C. A. Beuchat and E. J. Braun
Department of Physiology, College of Medicine, University of Arizona, Tucson 85724.
In reptiles, there are two pairs of kidneys at birth: the mesonephros and
the metanephros. The metanephric kidney in reptiles, as in all amniote
vertebrates, is retained as the functional kidney in adults. However, the
reptilian mesonephros does not degenerate until after birth, and its
function during this time is unknown. In neonates of the iguanid lizard
Sceloporus jarrovi, the metanephric kidney is only 63% as large as
predicted from the allometric relationship between kidney mass and body
mass in adults. However, the kidney mass of neonatal lizards conforms to
this prediction if the mesonephric and metanephric masses are combined.
Some other amniote vertebrates appear to follow this pattern as well: in
marsupials, which retain the mesonephros for a short period after birth,
the sum of mesonephric and metanephric mass in neonates conforms to the
allometry of kidney mass on body mass for adults. In contrast, the
mesonephros of eutherian mammals is degenerate at birth and the metanephric
kidney alone is of the predicted size. That the scaling of kidney mass in
neonatal lizards and marsupials is the same as that of adults only if the
mass of both the mesonephros and metanephros are combined suggests that the
mesonephric kidney in these vertebrates plays a significant role in the
regulation of water and ion balance during development and for at least a
short time after birth.
