Subject: Water for Animals in Water

Phil Colla (pcolla@cts.com)
Sun, 15 Feb 1998 13:40:16 -0800

>I would like to know how animals that live in and/or depend upon the oceans
>obtain their fresh water?".  I would really appreciate it if you could help
>me.

Hmmm, that's a broad question.  My understanding is that most aquatic
animals satisify their water needs through the food that they eat, although
some can actually ingest sea water and digest/process it to their benefit
while bypassing the salts.  I believe that pinnipeds (sea lions, etc) can
drink sea water in times of need, such as when food is scarce, and not
become sick as a direct consequence.  Many
(most?) have evolved special adaptations that allow their bodies to
conserve what little water they do obtain through food -- one example
might be not using much fresh water in their waste or urine.  Also,
aquatic mammals (and most animals in general, I think) have circulatory
and cellular systems that use selective permeability, so that where it is
advantageous, fresh water can "come in" but can't "get out",
through a cell wall for instance.
This allows a higher salt content to exist on one side of the barrier than on
the other, which helps animals that live in salt water.

Since different families of aquatic animals have differing strategies for
obtaining and retaining fresh water, it is necessary to consult specific
texts / experts for the animals in which you are most interested.

Does that answer your question?

Phil Colla

-----------------------------------------------------
Phillip Colla                          pcolla@cts.com
Humpback Whales: http://www.earthwindow.com/hwrf