Snail species - one or two?

[SirT]

Hi, just came across a BBC news item about some Japanese snails here:
http://news.bbc.co.uk/earth/hi/earth_ne ... 264808.stm

The question is - why do researches still consider those snails to be the same species? I always thought the classical definition requires them (the snails I mean ) to be able to produce a fertile offspring. In this case the snails are not able to cross-breed at all. So why not separate?

[Darby]

They probably aren't 2 separate populations - it isn't clear whether the coiling trait breeds true or not.