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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!
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