Saturday, 30 August 2008

In which I make an effort to learn about bivalves

Until recently, I haven't spent a lot of time on bivalves. Other than as ingredients in a marinara sauce, that is. But now I've been focussing on the crunchy bits on the outside, rather than the juicy insides. It turns out that — contrary to my gastropodal preconceptions — bivalve shells don't all look the same.

Here's one I prepared earlier.

Laternula (family Laternulidae, subclass Anomalodesmata) is a small genus of bivalves living in soft sediments in the Indo-Pacific and Southern Oceans. A few species are common in southern Australia.

Laternulids are easily distinguished from other families. The shells are thin and fragile and are attached to one another by a tricky hinge operated with a pair of ligaments. As with other bivalves, the main ligament is a wedge of elastic protein. Because the shells are so fragile, this ligament is attached to spoon-shaped chondrophores that project into the shell cavity rather than directly to the shell edge. This ligament is also strengthened by a calcareous plate, the lithodesma.

The secondary ligament, which is on the outside of the shells, is formed from a continuous layer of periostracum. Weird, huh?

Laternulids have a few other strange features, such as a fine split in each shell that allows the shells to flex. But then they have an internal buttress that reduces the potential for damage … You can see them both in the photo below.

No wonder they spend all their time sitting in soft mud.


Mosura said...

Crunchy bits! So you've strayed from malacology to conchology. While I love all shells, bivalves do tend to stress me out as there are just so many of them with minor differences. An interesting and informative post none the less.

mick said...

hah! - knowing how interesting the outsides are will this make one more or less likely to use the inside ingredients?
An interesting post.

Snail said...

Knowing what those insides feed on might influence my decisions!


Found any pearls yet?

Snail said...

Oh, I wish, Aydin. I wish.