Wondernose: What animal stands on its head and kicks food into its mouth?

by Rebecca Martin | May 1, 2022 | 0 comments

Barnacles on costal rocks
Barnacles on rock. Photo © iStockPhoto.com.

You would have to be quite lively in order to eat in this manner, wouldn’t you, Wondernose? And maybe you would have to live in the water like our mystery animal. Also, if you really wanted to be like our mystery animal, you would have to live in the exact same spot for your entire adult life, because you’d cement your head to a solid surface. I guess such a lifestyle doesn’t sound very appealing.

This is quite the animal. Its life cycle includes three stages. When the eggs hatch, out come tiny swimmers with one eye and three pairs of legs. By tiny, I mean like one five-hundredth of an inch, for some of the species anyway. If you’d see one, you would think it was a miniature water flea. But actually, this newly-hatched creature is called a “nauplius” by scientists.

No, no, I haven’t given away our mystery animal’s name, Wondernose. That’s only the name for the first stage of its life.

Eating away, the nauplius larva grows bigger and bigger. Six times it has to molt (called an instar) because it grows too big for its skin. Finally it changes shape entirely, becoming a cypris larva. A cypris looks like a miniature shellfish with six pairs of two-branched legs, two more eyes, and two big feelers.

The cypris larvae don’t eat. They seem to have only one thing in mind—finding a place to settle down. Drifting in toward shore, the larvae feel around till they reach a rock or a timber. They can spend days searching for the perfect place to attach themselves.

Now they transition rapidly into the third, or adult, stage of their lives. This means each one will lose all its eyes and form a hard, lime-like box around itself—a box with a lid, mind you, that can be closed when there’s danger.

So what you have now is a sort of clam-like creature shut up in a prison of its own making. Its legs are constantly waving out through the box’s lid, catching food from the passing current. Then, as our riddle has said, the legs sweep the food through the shell’s opening into the animal’s mouth.

On some of the world’s seashores, these animals are very numerous. Not only do they settle on rocks, but they also colonize on docks and the bottoms of boats. Crowded close together, they can form quite a crust, which creates drag. This slows boats, and decreases fuel efficiency by as much as forty percent.

Correct, Wondernose. Our mystery animal is the barnacle. Years ago, barnacles were much hated by ship owners. Ships were sometimes purposely run aground to scrape barnacles off the bottom. Nowadays special paints are used to discourage barnacles.

Even whales and turtles are claimed by barnacles for their colonies. Barnacles like it when there’s a good current, you see, because a moving current will bring more food their way. It’s a little hard for us to imagine—bound to one spot, getting to eat only the food that happens our way.

Scientists used to think barnacles are mollusks, since their shells resemble those of clams and mussels. But once scientists discovered that barnacles have a free-swimming larval stage, they started calling them crustaceans. This means they’re comparable to shrimps or lobsters.

There are two main types of barnacles, the acorn type and the goose type. Acorn barnacles have five hard plates that are opened and closed as needed by a muscle running across the body. When the plates are closed, you could think the barnacle is just a single hard shell. Often barnacles live at spots where the tide goes in and out, so they spend hours out of water. They can’t live without water, can they?

But the barnacle knows what to do. As the tide goes out, it closes the plates, shutting in enough water for comfort.
What about breathing? A tiny opening allows air inside. The oxygen dissolves into the trapped water and is absorbed by the barnacle.

Goose barnacles are funny creatures. Their name comes from the long rubbery stalks that grow out of the head. The ends of the stalks are fastened to the rocks. Picture these hard-shelled animals, looking as if they’re growing on thick goose-necks from the rocks. Interestingly enough, Wondernose, sometimes you’ll find a big acorn barnacle, maybe 3 inches (7.5 m) across, upon which several goose barnacles have taken up residence!

Barnacles on rocks
Barnacles. Photo © iStockPhoto.com.

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