Re: Tears and 'salt excre

J. Moore (
Sat, 11 Nov 95 10:31:00 -0500

Ss> Sean replied,
Ss> I think it is somewhat worthwhile to point out
Ss> that the physiological composition of sea mammals body fluids is quite
Ss> different from their terrestrial and freshwater
Ss> counterparts. While it is still necessary to eliminate
Ss> ions, their physiological ion composition is almost the same as
Ss> seawater, thus there is very little need to eliminate
Ss> sodium, potassium, chloride,..etc in the same way as we
Ss> would or say a nice piece of trout.

It would be more worthwhile if it were true... ;-)

Sea mammals, along with marine birds, reptiles, and bony fishes,
do *not* have a physiological compostion "almost the same as
seawater"; such a composition restricted to some invertebrates,
although elasmobranch fishes (non-bony fishes such as hagfish,
rays, and sharks) have plasma which is isotonic to seawater
(that of sharks and rays are actually somewhat hypertonic to
seawater due to large amounts of urea in the plasma).

Sea mammals therefore do have to be able to eliminate sodium in
the same manner as we do, which is why they have large, complex
kidneys compared to us.

Jim Moore (

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