Sea Shells On The Sea Shore

There’s more to limpets than meets the eye. From their remarkable homing instinct to body-slamming defence mechanisms and super-strong teeth, these sea snails are amazing creatures

- Helen Scales

Peer through the waterline in a rockpool and you might see a seashell shaped like a miniature volcano, gliding slowly by. And no matter how familiar you are with the wildlife that lives between the tides, you might still be amazed to see a little head and two tentacles peeping out from under the shell and sweeping from side to side.

Commonly, you’ll see limpets clamped tightly to rocks, often encrusted with barnacles and showing no signs of moving any time soon – almost like they’re part of the rock itself. But if you encounter them when the tide is high, and their world is flooded, these humble beachside molluscs reveal themselves to be far more animated.

As the waters rise, limpets set off in search of food. They spend much of their time roaming around rockpools and wet rocks, rasping at microalgae and seaweed sporelings with a prickly tongue, known as a radula, that’s covered in dozens of tiny, sharp teeth. Imagine a cat licking a bowl of frozen milk. Were you to have a stethoscope to hand and place it on a rock nearby, you might be able to make out an intermittent, sandpapery scratching as each limpet gathers its food. Even if you don’t spot limpets out and about, you can see the tell-tale trails they leave behind, in the artistic zigzag marks they scrape into green films on the rocks.

DEALING WITH DANGER

And if you’re lucky enough to time your rockpool visit with the arrival of an aquatic predator, such as a starfish or whelk, you might witness a surprising scene unfold. Sensing danger is near, a limpet won’t immediately clamp down and hide inside its shell. Instead, it uses its muscular foot to push the shell skywards until it looks like a mushroom, which is why biologists call this behaviour ‘mushrooming’.