01 September 2007

A small survivor

The huge and pretty Australian land snail Hadra bipartita was the subject of a recent post at A Snail's Eye View. These snails can grow up to a rather respectable shell diameter of 68 mm.

In stark contrast, tonight I was measuring a tiny, tiny snail, Vertigo pygmaea from my backyard. At least 2 times a year, I collect all the live adults I can find, measure their shells and then return them to the yard. The sample averages are about 1.8-1.9 mm (details here and here).

Usually once a year I also mark* the shells of a number of snails. That helped me determine that adult snails can survive the winter (details here). The last time I marked some snails was on 25 December 2006 when I used red ink on 20 adult snails. To my surprise, one of the 12 adults I found today had a red mark on its shell. Prior to last December, I had used red ink also in March 2006. I will assume that an ink mark on a shell would not last that long. Therefore, the marked adult found today was probably marked last December and has been alive as an adult for at least 8 months.

vertigo under scope
Those dots in the container under the microscope are the snails I measured tonight.

*I have been using various colors of Pigma Micron pens. The ink survives on snail shells for at least 3 months. In the case of one of the snails collected today, the ink was visible after 8 months.


Kevin Z said...

I see you sporting the Olympus SZ60. I use the SZ40 myself. Nice scope! Great to have the trinocular for the camera.


Unfortunately, mine is not trinocular.

Brenda said...

Fantastic! What beautiful creatures! How do you manage to collect them without damaging their shells?

Harry G. Lee said...

Aydin, this is a fine example of what a "citizen scientist" can do without breaching the pale of his backyard and "conchological den," as Walter F. Webb referred to it.


Brenda: Their shells are not that fragile actually. The blue plastic tweezers visible in the picture work well. For very small juveniles, which have thinner shells, I use the ol' wet-the-tip-with-saliva method: you get a very fine stick, like a pine needle, lick the tip & then used that to pick up tiny shells. It's the magic of surface tension.

Harry: Thanks for the compliments.