Salty things

[Raven~ <biology@ctos.com>]

archosaur@usa.net wrote:

> As for the original question, reptiles do indeed need salt just like all other
> vertebrates, and maintain the same balance as any other vertebrate.

Agreed -- all vertebrates need salt.  (Actually, all organisms need
salt.)  All vertebrates also have mechanisms for conserving salt from
the diet or from the environment.  All organisms have sodium appetites
(developed to varying degrees).  Chemoattractants (of some sort) drive a
vertebrate to satisfy its sodium appetite by eating salt (salt licks) or
eating vegetation high in sodium.  We humans do the same thing.

> 
> I'm not sure how birds deal with excess salt (are they mainly renal, like
> mammals?), 

In general to get rid of excess salt, birds have salt glands located in
the orbits of the eyes.  Ducts from these glands drain into the nasal
passages.  Naturally, the salt gland is quite well developed in the
marine birds.

Betty Cunningham wrote:
> 
> These responses all address removing EXCESS salt (though still really
> interesting).
> 
> My question was rather would dinosaurs (et all) have sought out SOURCES
> of salt to ingest it-such as a salt lick?
> 
> -Betty

Since all known vertebrates have a sodium appetite that must be
satisfied, it is not unreasonable to assume that dinosaurs (et al) would
have sought out sources of salt to ingest if they were not getting
enough salt in their regular diet.  (How much salt would be required
would be another story and to answer that we'd have to know about the
adaptive conservation mechanisms of the animals.  My suspicion would be
that there would be a great deal of variation depending on the natural
environment of the species.

Roberta M. Meehan, PhD