13 December 2009

Vertigo galore

Vpygmaea4

Twice a year, usually late in the fall and late in the winter, I collect all the live Vertigo pygmaea in my backyard, measure the shells of the adults and then release them in the yard. Yesterday I did the 2nd and the last part of this year's survey. I found a total of 55 snails, 49 of which were adults.

The picture above shows the snails after I revived them in a wet container. For a while after they wake up they tend to climb all over each other's shells.

Here is the most unusual specimen in the lot. It had lost most of its body whorl, but the columella—the central axis of the shell—had survived. And the snail inside was alive. The shell was 1.4 mm long. The shiny membrane is the dried mucus film that was partially covering the aperture.

Vpygmaea3

Come to think of it, this wasn't such an unusual specimen; last January during this years first survey, I found a snail with an exposed columella just like this one. I don't know what breaks their shells like that. Probably a predator slightly bigger than the snails.

1 comment:

Anonymous said...

Very cool!

Where exactly do you find them in your garden, when they are active, and when they are hibernating? And is the soil in your immediate area calcareous or not?

Susan J. Hewitt