>
fish do not urinate as such.
>
> Its *roughly* like this:-
>
> "Like other fishes, sharks excrete nitrogenous wastes over
their
> gills. The teleosts, or bony fishes, excrete nitrogenous wastes in
the
> form of ammonia. Ammonia is a very toxic compound, and excretion
of
> ammonia requires passing large amounts of water over the gills.
Marine
> teleosts replace this water lost to excretion by drinking a lot
of
> seawater and using their gills to remove excess salts.
>
> Sharks, on the other hand, excrete nitrogenous wastes as urea,
which
> is a less toxic compound. A complex biochemical pathway called
the
> ornithine-urea cycle converts ammonia to urea, which can be
stored
> more safely in the blood. In a live shark, ammonia doesn't
accumulate
> because it is quickly converted to urea. When the shark dies,
the urea
> deteriorates back into ammonia, which is why shark meat often
tastes
> and smells of ammonia. Apparently you can remove much of this
ammonia
> by soaking the flesh in freswater or lemon juice before cooking
it."
>
>
> and as in the other post, urea is used in osmosis
to keep salt balance
> of the ray OK.
>
> It's illuminating
that all over the web you see Q&A's saying ammonia
> smelling skate
will be off and stuff about urinating through the skin.
>
> The
gills of a fish probably approximate to kidneys in this context.
> --
> Mike... . . . .
ornithine-urea cycle
http://www.youtube.com/watch?v=AoBbVu5rnMs