Starfish are impressive in their ability to regenerate. An individual missing one of its five limbs quickly grows a replacement. More remarkably, the servered limb will grow four tiny stumps that develop into full-size limbs to form a new starfish. In contrast, the thick and colourful spines of the Slate Pencil Sea Urchin invite a closer look. Sea urchins graze on the algae or invertebrates that encrust the surface of the dead corals by using Aristotle's lantern, a jaw-like structure in the mouth that is centrally located on the underside of the body.
Sand dollars are sea urchins that have extremely flatten bodies and tiny spines.
The rows of tube feet that extend along the underside of the body provide the means of locomotion and feeding in sea cucumbers. Sand and mud rich in organic matter are shovelled into the mouth as the sea cucumber moves across the sea floor. The processed sand is then excreted in a characteristic pattern from the anus. When alarmed, sea cucumbers eject white sticky strands from the gut to distract attacking predators. They move slowly across coral reefs or shipwrecks to find a spot where their arms are exposed to ocean current.