07 June 2006

A snail at the edge: Littoraria irrorata


These snails, commonly known as Marsh Periwinkles, live in salt marshes and mangrove forests at the edge of the land. I suppose the snails, if they could contemplate their own standing in the grand scheme of things, would probably consider themselves at the edge of the sea, for they evolved from completely aquatic marine ancestors. They are almost fully terrestrial, although they still have to return to the sea, their ancestors’ homeland, to reproduce.

This species has already been the subject of a previous post. I had never observed them in the wild until last weekend when I found several of them in a mangrove habitat near Tampa, Florida.

irrorata2Littoraria irrorata carries on top of its foot a thin, horny operculum that seals the aperture of its shell after the snail withdraws inside. Because the operculum is flexible and its diameter is slightly smaller than the diameter of the aperture, the snail can withdraw its body about a half a whorl beyond the aperture. The picture on the left shows the operculum within the bodywhorl.

This demonstrates that, like almost all other land snails, L. irrorata also builds slightly oversized shells. In other words, the snail’s body is smaller than the inner volume of its shell. I have explored this topic before in several posts here, here, here and here.

More information on L. irrorata is available at the Animal Diversity Web.

I will return to this species in future posts.


budak said...

Are these the snails preyed upon by the endemic Snail Kite?


No, snail kites eat the apple snails (Pomacea paludosa).