14 March 2008

Sleeping Haplotrema concavum wakes up

Around noon today the dormant Haplotrema concavum that I first saw on 20 December 2007 (85 days ago) was still hibernating in its little hole in the soil. The previous posts about this particular snail are here and here and here.

I wanted to take pictures of the snail, but I was afraid that if I waited too long, it would wake up on its own and crawl away, so I decided it was time for me to wake it up. I brought it home in a little container and when I took it out about a half an hour later, the snail had already moved closer to the aperture (you can see in the pictures in the earlier posts that during hibernation, the snail's body was 1/4 whorl behind the aperture).

Here is a set of pictures of showing how H. concavum came out of its shell. About 2 minutes elapsed between the first and the last picture. Compare it with the pictures of how Pomatias elegans comes out of its shell in this post. In both snails the foot comes out first, followed by the head. In other words, the overall sequence is the same in both snails even though from an evolutionary view point they are quite distant from each other.


In the case of P. elegans, the foot has to come out first to move the operculum, which is attached to the foot, out of the way. But why does H. concavum, which doesn't have an operculum, have to put its foot out first? I can think of 2 answers. First, it wouldn't be safe for a snail to put its head out first, because if a waiting predator attacked it, the snail could get injured on its head where all the vital organs are, whereas an injury at the tip of the foot would be easier to deal with. Second, the snails without opercula are stuck with this sequence because their musculature and body plans evolved from ancestors that had opercula.

Here is the fully revived H. concavum.


Haplotrema concavum is a carnivore and this one hasn't eaten anything since December. I have some potential prey for it. If I can photograph it doing what it does best, eat another snail, I will post those pictures next week.


Anonymous said...

When the snail is out of it's shell and extended it will always pull the head back (then into it's shell) first if threatened. Again, probably to protect the most vulnerable parts. I think you will find that virtually all snails behave that way.

Another thing I've noticed about Liguus snails is that, when they are startled into their shell they always "excrete" a certain amount of water. It was reported that this liquid repels ants. I'm not sure I buy that except that it probably contains some slime which the ants might find too sticky to deal with. pete k

x said...

How long will it be before somebody comes up with a radio tracker for such tiny creatures?

Anonymous said...

I saw a tv show where they were radio tracking the two inch long Pomacea paludoso in a Florida lake. Pete K.