Paul Monfils wrote, "Imported snails interbreeding with local snails?  Very
interesting! Presumably they were closely related forms?  Same genus?  At
least same family?  Any additional information on this would be welcomed.
Another consideration - are there some species that can reproduce
hermaphroditically?"

I don't know the specific names, but the classic example is that of an
edible landsnail that was imported from France to California many years ago.
When I lived in California in the 70's, I was told that they had interbred
with the native snails, reducing their size. They were certainly present in
overwhelming numbers, and did enormous damage to gardens. If anyone could
affirm or deny this little story with details, I'd appreciate it.

Getting back to James Cheshire's innocent question: Another good reason not
to transport living snails away from their habitats is that some freshwater
snails carry parasites (viruses, bacteria, worms, etc.), some of which cause
serious diseases in people. Even if the parasites do not affect humans, they
might well be able to infest native snails, birds, domestic or wild animals,
etc.

Well, folks, I have to step out of this discussion awhile and get back to
other work... have fun! And listen to what Kurt has to say. He knows!

Andrew K. Rindsberg
Geological Survey of Alabama