Triploid Oysters?

Here is the story:

TRIPLOID OYSTERS
on Hilton's Coast Seafoods Company
http://www.coastseafoods.com/triploid_oysters.html

OK, that takes care of my idea of mammals always staying diploid and not augmenting chromosome numbers by ploidy variations, right?

Wrong. Oysters are not mammals.

I am not sure why, but tetraploid (one ploidy more than triploid, four rather than three or the normal two chromosomes in EACH pair/group) mammals, at least some mammalian types, like human chromosome setup, will either spontaneously abort or - one boy - be born very sickly and die very quickly. I suppose it is the mother's immune system. Anyway, oysters aren't developing in placentas or uteri, so the triploid oysters don't have that problem./HGL