30 March 2008

Assiminea succinea takes a dip, but doesn't like it

The tiny Assiminea succinea is one of my favorite semi-terrestrial, coastal snail species. If there were a contest to select the cutest snail, I would vote for it without a 2nd thought.

The shell of this snail was about 3 mm long.
Photographed with an Olympus E-500 with a 35 mm Zuiko lens + 25-mm extension tube; 1/160 s, f14, ISO 200; light was from an Olympus FL-36 flash; both the camera & flash were hand-held.

Despite the fact that Assiminea succinea lives by the sea and is classified as a "sea shell", it doesn't like being in the sea. I was able to demonstrate this to my own satisfaction with a simple immersion* test last week when I was in Florida. The experimental set-up consisted of a small plastic container containing sea water into which a slanted platform was placed.


I placed each of the 2 "volunteers" I had one at a time on the platform just below the meniscus and then watched them while timing them. Both crawled out of the water in about 8 minutes. They were slow crawlers and the surface tension that they had to break thru may have hindered their movements a bit.

Here is one of the little guys struggling to get out of the water.


One nice thing about staying with relatives was that I had a bathroom to myself that I turned into a snail lab and photo studio for the duration of the 5 days we were there. In a hotel room, on the other hand, I would have hesitated to leave my specimens, live snails and equipment around during the day.

The 2nd post about A. succinea is here.

*Immersion is not to be confused with emersion.


Anonymous said...

Cute indeed!

Anonymous said...

I have to say: you take the *best* pics of these small live snails!

Yes, I know what you mean Aydin: it's can be really hard trying to do research out of a hotel room. I do that every year when I go to Nevis.



Tim Pearce e-mailed the following comments:

"When I first saw the excellent photos of your Assiminea succinea, I was shocked to see that it has eyes on the tips of the tentacles. I wondered if you confused a stylommatophoran with a prosobranch. Could it be a baby of a pupillid, or maybe Pupisoma? However, it has just two tentacles (not four – although some Orthurethra seem to have only two), and it does seem to have the snout of a prosobranch. Unfortunately, your photos do not show whether it has an operculum. If you have a photo that shows both the operculum and the eyes on stalks, that would convince the skeptics like me that here is a very unusual prosobranch! If you have such a photo, please include it.
And if so, then you might change the focus of your blog post to highlight this unusual prosobranch with eyestalks. The only other prosobranchs I know with eyes on stalks are the Strombidae.
This instance of eyestalks on tips of tentacles in land snails seems to represent only the third evolutionary instance of eyestalks on tips that I know about. I am assuming that Stylommatophora and Systellommatophora acquired eyes on the tips of the tentacles independently. Then the Assimineidae would be yet a third instance.
I believe that Assimineidae from the tropics tend to be even more terrestrial than our east coast species. If natural selection favors eyes on tips in land snails, I wonder if our east coast species is a descendent of a more terrestrial species, and has gone back to the water a bit more than its ancestors. Complete speculation.
Very nice photos."


Yes, they have opercula. That will be the subject of another post.

Dave Coulter said...

Amazing photography!