Eastern Pacific from Baja California, Mexico up the coast to Alaska [3] Life history. Pacific Purple sea urchin (Strongylocentrotus purpuratus) is smaller than red urchin at three to four inches in diameter and abundant on the Pacific Coast, especially California, where it’s threatening kelp forests. (Olhausen and Russo, 1981) Biogeographic Regions; pacific ocean. Their shells are made of rigid, bony plates. Strongylocentrotus purpuratus is primarily found in the low intertidal zone. Diet of the Sea Urchin. They are covered in pincers, tube feet, and purple spines that move via ball-and-socket joints, using these spines to grab food and protect themselves from predators. But if sea otters are abundant, they eat sea urchins and keep the urchin population in check, which allows kelp to flourish. In a kelp forest, sea urchins can graze on the kelp and eat their holdfasts, resulting in deforesting the kelp from an area. In Nature, these spines serve as their defense mechanism from predators. A sea urchin’s shell is called a test or a shell. Purple sea urchin can regenerate broken spines and can grow new teeth at rates that result in their complete exchange in about 75 days in the lab. This species thrives best in tanks with plenty of live rock to explore and feed off of. Other behaviours and adaptations In order to gain protection from predators and the elements, Purple Sea Urchins cluster together and use their sharp spines to burrow into the rock. They use these five pyramids and each pyramid has a tooth to force algae off rocks. The purple sea urchin also has five teeth which form to create Aristotle’s Lantern. They also are preyed upon by numerous fish species, such as wolf eels … Description: The Purple Short Spine Pin Cushion Urchin is a small Urchin that has sharp protruding spines. The purple sea urchin thrives amid strong wave action and areas with churning aerated water. Sea urchins mainly graze on algae and undersea vegetation, such as kelp. They have also been known to feed on sponges, sea stars, mussels, sea cucumbers, carrion, and polychaete worms. They grow to only 2-3 inches. Green sea urchins are harvested from the Atlantic, while red and purple urchins are harvested from the Pacific. Sea urchins can be many colors, including black, brown, right pink, dark purple, green, and sand colored. In 2014-15, sea stars began dying en masse from a mysterious wasting disease, which scientists believe was exacerbated by a massive blob of warm water that spread throughout the Pacific Ocean.. Because starfish prey on sea urchins, the latter population's exploded when the former's dwindled. These days, domestic supply stays domestic to meet growing demand and ethnic markets. native; Habitat. They use these five pyramids and each pyramid has a tooth to force algae off rocks. One of the NEATEST stories in sea urchin evolution is how a major sub group, the "irregularia" aka the sand dollars, sea biscuits, and spatangoid ('heart urchins') sea urchins all evolved from a more open lifestyle with the feeding modes shown above (herbivory, predation, omnivory) to a specialized series of body forms that involve plowing through sediment/mud/sand in order to obtain food. Sea urchins are an important part of the diet of sea otters. According to the California Department of Fish and Wildlife, over the past few years, about 90 percent of all coastal kelp from San Francisco to Oregon has been mowed down by a purple sea urchin population that is 6,000 percent larger than historic averages. Sea urchins have even been found at depts greater than 6,850 meters! Pacific purple sea urchins are easily identifiable on the ocean floor because of their distinctive purple color. Sea urchins feed by grabbing and biting with their five teeth. Sea urchins, and closely related sand dollars, include around 750 species worldwide. Purple Sea Urchins are found in southern Queensland, New South Wales, Victoria, South Australia and Western Australia. Purple sea urchins are found on the pacific coastline from Alaska to Cedros Island, Mexico. Domestic supply is also supplemented by imported product, mostly from Chile, during summer months.