The Halloween Collector Urchin (Tripneustes gratilla) is a beautiful Urchin that can be found among the South Pacific. Their color on their body is a black and white and their spines are a bright orange giving them their name. They reach a maximum size of 3-4 inches and feed on a variety of detritus, as well as algae. They are typically stationary during the day, but will come out around twilight to scavenge for food. The mouth of the Urchin is used to scrape algae from rockwork.  The spines of the urchin are a defense mechanism that are barbed like that of a fish hook and can inflict serious pain to the predator.  These spines can either come to a sharp point or can be stubby and blunt. Some fish will lay eggs among urchins, relying on the spines to keep them safe from predators.