The subtidal zone is a pleasant habitat below the intertidal zone that is home to many fish, crabs, echinoderms, and—of course—mollusks. Snails, squid, clams and octopi inhabit the region of the ocean that most people think of as the "open ocean." But one mysterious animal is "locked" in this zone—literally. And it's not boring at all. Meet...
...this guy. Now what do you think this is. Think very hard, because you've probably eaten it before. It's a clam. Not just a clam, but people call it the "boring" clam. Not "boring" as in dull and uninteresting; it means it can bore into hard surfaces. The more common name for this creature is the "Piddock."
What makes this animal in the picture a clam? Doesn't it just look like some tubes, or an anemone? What you are seeing is the clam's siphons, or tubes it uses to breathe and eat. If you look closely on other mollusks like sea snails or octopi, a siphon is present.
However, with land mollusks like slugs and snails, a similar organ is present — the pneumostome. This hole is where the animal breathes and poos.
Piddocks are able to drill into soft rock and wood, including docks and piers. Once a piddock is born as plankton, it drifts around to find a rock/surface to attach to. Piddocks have specialized shells that are flat on one portion and have striped grooves on the other. This way, the grooved side of the shell can be used to drill into the rock. Piddocks stay in their rock for their whole life. They eat algae and microscopic plankton in the water. Their siphon is most often used to eat it.
If you see a rock with a lot of holes in it, it may be from a piddock family that once lived in the rock. The piddocks in the rock are all dead, unless you see the rocks in the subtidal zone.
Do you want to see a piddock yourself? First, wait for a very low tide. Piddocks can sometimes be found in the intertidal zone. Go to a tidepool site with boulders and rocks. Then, look on rocks slanted vertically. Specifically, watch for rocks with holes because piddocks may be living. Look inside one of the holes for a siphon. Don't poke or touch it because that is the clam's breathing organ. Be sure to take a lot of pictures!
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