Dear Conchlers,

With all the talk these days about freshwater mollusks as indicators of environmental health, I am moved to ask:

What kinds of changes must be made in a mollusk to let it live in fresh water?

Obviously, mollusks entered fresh water more than once (as snails and clams, at the very least). How many times did it actually happen?

Cheers,
Andy

Andrew K. Rindsberg
Geological Survey of Alabama