Saturday, July 5, 2008
What is more pointy than a sea urchin? In addition to the spines that most people see, sea urchins have small pinchers in between their spines called pedicillaria. The pedicillaria are used to pinch off any creature which tries to settle on them (like barnacles or algae) for a free ride. They can also be used as a defense against predators who aren't deterred by the spines, like sea stars. The urchin will fold down their spines and use the pedicillaria to pinch the sea star's tube feet and stomach.
They also have super pointy teeth. There are five teeth that continuously grow and are held in a structure called Aristotle's lantern. They use these teeth to scrape algae off of rocks, and to form little pockets in the rock where they live. Sea urchins kept in aquariums can cause lots of damage to the acrylic by chewing it up, and if they are kept in a concrete and fiberglass touch tank, they can chew right through it.