02 August 2009

Cepaea nemoralis in Maryland—Part 2


Yesterday was a good day for a field trip, despite the heat and the humidity—and the abundant poison ivy everywhere. We surveyed the vicinity of the location where Cepaea nemoralis had recently been discovered (see part 1). We found additional colonies constituting what appears to be one widespread population.

The shell colors and band numbers of Cepaea nemoralis are notoriously polymorphic (Evolution MegaLab has a brief introduction). Various environmental (temperature, etc.) and biological (predators) factors are believed to influence the distributions of shell color and banding types in different habitats. The evolutionary implications of Cepaea nemoralis polymorphism have been studied for decades (again, check out the Evolution MegaLab pages for introductory information).

We found both empty shells and live specimens of 3 banding varieties all with yellow shells. There were unbanded snails and 5-banded snails.


And then there were 1-banded snails.


To better delineate the range of the species in our study area, we are planning further field trips on future hot and humid days. Watch this blog for updates.


xoggoth said...

Oi! Stop nicking our snails!

That certainly looks a more typical one, brighter.

Kevin Bonham said...

I have just had a very similar experience here with a somewhat less attractive and perhaps more unwelcome introduction here, Cernuella virgata. Someone sent me a pic and it turned out to be the species in question, only its second truly "wild" colony in the state (Tasmania). Reported it to biosecurity and I haven't heard back from them, so don't know if they have been out to clear it up with implements of destruction or not. I will leave a comment about a good reason to obscure the locality of such infestations (as you are doing) on the previous thread.

jaimie said...

Aha! I found some of these snails in a neighborhood in Providence, RI, there were at least ten of them, dormant, stuck to the branches of this small tree (or shrub?) approximately 5 ft. tall. The tree was planted between the side of somebody's house and the sidewalk, and I thought it odd because the ground beneath the tree was mulched with that reddish orange stuff and there were no other plants nearby. On top of that, the tree had no signs of being nibbled upon.

Edward Baker said...

I've seen a lot of these this year, although being in the UK that's not too worrying!

Deniz Bevan said...

I saw one of those (the last photo) on the sidewalk yesterday! I'm always afraid that someday I'll hear a crunch and find I've stepped on one of these things...

School for Us said...

Beautiful snails!