Wednesday, April 19, 2006

The operculum

Most snails, we are told, have an operculum. A flattened piece of hard material that acts like a door to the opening of the snail shell. While probably an effective barrier to predation, many land snails have abandoned the operculum. Instead, they seal their aperture with a mucous-based material called an epiphragm. In my opinion, the casting away of the operculum is probably the single biggest step towards being successful land invertebrates snails have taken since the evolution of the Pulmonata.

That's all I have to say about that right now - but an out loud thought I have regards extra space in the body whorl of operculates versus non. I suspect non-operculate snails have more extra space in their body whorl, but I don't have the data to back up that hypothesis. Anyone want to write a paper?

Friday, April 14, 2006

A little help?

I've got a snail that's proving hard to ID:

At first I thought it was Neohelix albolabris based on the size (it's 24mm wide) and shape/size of the reflected lip. But, its umbilicate, and Neohelix is not. So... any ideas? Burch's 1962 field guide hasn't helped me here. Perhaps it's an introduced spp? I posted an earlier pic because it has an interesting predation scar pattern.

I'm pretty sure this one is Mesodon given that it's about 2/3 the size of the first and the other characters do match with the description.

Wednesday, April 05, 2006

Beringia mollusks

Just came across an article - haven't read it beyond the abstract and a quick scan, but it's got some interesting info regarding Beringian mollusks. Primarily they suggest mollusks were introduced by migratory birds to the area. Hmmm...

LAURIOL, B., Cabana, Y., Cinq-Mars, J., Geurts, M.A., Grimm, F.W. 2002. Cliff-top eolian deposits and associated molluscan assemblages as indicators of Late Pleistocene and Holocene environments in Beringia. Quaternary International. 87, 59-79.

Reminds me of a previous post by Aydin regarding a book on a similar topic.