Polyplacophore (180/365)

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June 29, 2015 – Most people like showy shells, urchin tests, or sand dollars.

In my little dish of shells collected on outer coast beaches in BC, this little thing, half the length of my thumb, is my treasure.

It’s a chiton and it represents 400 million years of evolution that has almost stood still. When you have evolved to adapt perfectly to your environment, why change? Chitons have conserved their form for a very, very, long time.

Chitons have a dorsal shell which is composed of eight separate shell plates or valves. These plates overlap somewhat at the front and back edges, but still articulate well with one another. Because of this, although the plates provide good protection for impacts from above, they nonetheless permit the chiton to flex upward when needed for locomotion over uneven surfaces, and also allow the animal to slowly curl up into a ball when it is dislodged from the underlying surface.

Their cool factor lies in their poorly understood ability to home. Several species are known to exhibit homing behaviours, journeying to feed and then returning to the exact spot they previously inhabited. They will somehow find their way back to their exact location, and nestle back into their home “scar”, which fits them perfectly because they have presumably ground it into the rock they call home base.

400 million years of history and some really cool biology all hidden in such an unassuming little thing.

The most interesting things in nature are usually the things you overlook, not the flashy creatures that seem to say “Look at me!”

Rather like humans, don’t you think?