Hedgehogs of the sea

This article presents information about Australian Sea Urchins. As far as looks and reputation go, sea urchins are not top contenders. These balls of pointy spines are echinoderms, echinus meaning hedgehog and derma meaning skin, and could be mistaken for a curled up hedgehog or echidna at first glance. Comprised of calcium carbonate, urchin spines rotate like a ball and socket in the same manner as human shoulder joints, giving them the flexibility to point in most directions. Spines are used in locomotion but can also be used to brace animals when wedging into crevices, to transfer food to the mouth, and in protection against predators. Among other distinguishing features of sea urchins are the pedicellariae. Found between the spines, these broccoli look-alikes are dynamic stalked structures terminating in three opposing jaws that open or close via muscular control. Their job is to clean the urchin's surface of unwanted debris and organisms. Urchins have a series of tube feet or podia that they use for locomotion. Individual sea urchins are either male or female and most reproduce by shedding their gametes into the surrounding water, a process known as external fertilization. Australia has 42 species of regular (radially symmetrical) sea urchins.