While I was in the process of moving one of my 10 gallon tanks to a different shelf I noticed a funky critter inching, yes, inching, up the glass of the tank where the water level was at gravel level. At first I thought it was a snail because I first spotted it from the outside of the tank. I reached in to grab it, but there was no shell. There was a knobby area where the shell would have been, but it was fleshy feeling.
I grabbed my camera and took some pics so I could figure out what it was. At first I thought it was some sort of planarian because of the shape of the head and the eye spots as well as the way it moved. Now I'm not so sure.
I learned that snails will move in an inching manner when they are either tangled in something like vegetation or when they are out of water. So that explains that.
I haven't been able to find any documentation related to a snail being able to survive without a shell. I'm guessing if this is a shell-less snail, that its been that way for some time. The reason I say that is because when I grabbed him he didn't have an automatic constricting as if he were trying to retreat into a shell. He instead held tight to the glass.
At this point the little info that I was able to find points to it being a Lymnaea, a pond snail. I do have a few pond snails in that tank. I just didn't think it would be possible to survive without a shell because of the lung.
Here's some pics. The last pic is a pic of the posterior end. What looks like poo is actually part of him. Anyone have any ideas?