Re: Why does a lobster's shell change color when REMOVED from water?

Hi Miss Hunt-
        Sorry for the delay in my answer- I've had a devil of a time
trying to find somebody who knows about lobster shells.  After asking a
physicist, a chemist, and finally a crustacean physiologist, it was the
physiologist who suggested that the colour change you observe is probably
a chemical change in the pigments similar to what happens when the lobster
is boiled, as outlined in Michael Onken's post that you've already seen
(
Re: What exactly makes a lobsters exoskeleton turn red when cooked?).
        Since lobsters have an exoskeleton which is fixed in size, they
must moult (cast off their old shell and grow a new one) in order to grow.
Your lobster will continue to shed its shell as long as it's alive, in
order to grow.  The exact rate at which it will shed its shell will depend
on lots of things, such as the temperature it's living at and how old it
is (as lobsters age, they tend not to grow as much, and will moult less
often).  I used to live in Nova Scotia, Canada, and every once and a while
someone would catch a gigantic lobster, two feet long or more; these
lobsters are invariably very old- probably 25 years old or more!
	The reason your lobster eats its shell (the technical term for a
cast off shell is the exuvia) is probably very simple- it
spent a lot of energy and materials making it, and it would be a shame to
throw it all away!  Eating its exuvia is a way to get back some of that
energy and will also provide some of the "building blocks" for another
shell.

Hope that helps!
Rob Campbell, MAD Scientist