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| Green sea urchin, Strongylocentrus droebachiensis |
The test is pink, fading to grey when the urchin dies. Spines green; they're in constant motion, pulled back and forth by skin and muscle tissue over the test. Tube feet (brown/black) protrude through holes in the test; they're moved by water from the internal vascular system.
The five plates in the centre are like teeth; they scrape food off the surface of seaweed and rocks. The whole centre structure is called "Aristotle's lantern".
This structure was named for Aristotle, a Greek philosopher, scientist and teacher who described the structure in his book Historia Animalium, or The History of Animals. In this book, he referred to the "mouth-apparatus" of the urchin as looking like a "horn lantern." Horn lanterns at the time were five-sided lanterns made up of panes of thin pieces of horn. The horn was thin enough for light to shine out, but strong enough to protect a candle from the wind. (thought.co)
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| Tube feet, with their suction tips, looking for something to grab on to. |
I can't remember you ever having an urchin in your tank...is that because you don't try to keep them? Or is this the first time one's come in with the kelp?
ReplyDeleteI've had a few very small ones come in with the seaweeds. They haven't survived. This one was already unhappy when I collected it off the beach, and didn't last long in the tank. I don't know if the crabs get them while they're still moving about, or if they die and the crabs get them afterwards. They do end up as crab food.
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