Brittle Stars (Starfish)

People used to feel sorry for me because I didn’t have eyes. Well, I’ve been seeing all the time—and in all directions at once—thanks to my wonderful Designer! Yes, my half-inch disc-shaped body is literally covered with crystalline lenses that work together like one big eye! Scientists now find that these lenses my Designer crafted “have exceptional optical performance,” superior to any manufactured lenses! Designed with just the right curvature to focus light to the nerve centers inside my body, they make it possible for me to get information whenever there is daylight. Predator nearby? Or some delicious morsel for dinner? Or a good place to hide? I see it right away!

With five thin, long arms extending from my half-inch size body, altogether about the size of your outstretched hand—you guessed it. I’m a type of starfish, and a close cousin of the sea urchins, sea cucumbers, and sea stars.

You think my long bony arms are just for swimming around? Oh, no! Besides being my means of getting food into my mouth, they are part of my “eye” system. You see, my Designer put clear “windows” in my bony arms. Each of the bones in my arms is a single calcite crystal, with a “window” in the shape of a double lens. Special cells (called chromatophores) clustered around these “windows” contain light sensitive pigment that controls the amount of light that enters my body. The result: I change color twice a day, much like you change your clothes! During the daytime I’m a darkish red, and at night I change to blackish brown and gray.

What do we brittle stars of the sea do all the time? We’re part of the sea’s housekeeping team. I just lay on the sand at the bottom of the sea, and let my arms wave in the flowing water above me. The curling tips of my waving arms catch organic particles, little sea animals and worms, and pass them down to my central mouth—you’d call it scavenging, but it’s food for me.

What if a hungry fish grabs my arm? Snap! He can have it—but that’s all he gets! No tugging me off by my arm! Just a few weeks, and I’ll have grown a new arm.

When I want to move, the spines on my arms provide traction to help me grasp the bottom. Someone watching might think I am lunging awkwardly. But I’m very agile. Turn me upside down, and flip! I’ll be right side up in seconds!

I’m not particular where I live, whether in shoreline shallows or 6000 feet down in the sea. You wonder that I’m not crushed by the weight of the water over my head? I wonder, too. Even a large bucket of water on your head would feel pretty heavy. But picture a bucket 6000 feet high—that’s what you have on top of your head when you’re at the bottom of the sea at that level. And if you humans want to explore at that depth, you have to build a device to withstand the water pressure. You build it with plates of steel several inches thick to take the pressure.

Now think about little me with all that water on top of my head, and I don’t even get a headache! No, I just lie on the ocean bottom waving my arms. How can I do it? You will have to ask my Designer! These wonders are beyond me!

Sometimes we multiply in incredible numbers, making a carpet on the sea floor up to an inch thick. And if you come by you’ll find all our little arms waving together, a living carpet of arms, all waving praise to our awesome Designer as we housekeep our part of the sea!

All praise be to Him!

Source of Information:
National Geographic News
Monterey Bay Aquarium: Online Field Guide
Biomes Marine Biology Center