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Sea urchins

The delicate ball-like skeletons of sea urchins are often found washed up on beaches and caught among seaweed in rockpools. Often some of the spines are still attached. Looking closely at the skeleton, you will find five distinct rows with holes and bumps. 

Sea urchins can be very colourful. They are covered in strong spines that often pivot where they join onto the skeleton. Some types of urchins have very long sharp spines that will snap off if they penetrate another animal. Between the spines are long tube feet used for locomotion and feeding. 

They have five small jaws surrounding their mouth. Their teeth are self-sharpening and they can chew through most things including stone. Algae make up most of their food and they also eat other sea creatures. 

They are sensitive to light, but don’t have any eyes. They are also sensitive to touch and chemical stimuli in the sea. 

Those with sharp spines are very painful when trodden on with bare feet. 

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