When their average food is unavailable, like lots of animals at the moment, they will resort to trying new foods, like animal remains, sea cucumbers, mussels, sponges, brittle stars, crinoids, etc. Occasionally they will sometimes eat a trail right through a coral. The sea urchin mainly feeds on algae on the coral and rocks, along with decomposing matter such as dead fish, mussels, sponges ans barnacles. Predators of Sea Urchins: Sea urchins are eaten by crabs, sunflower stars, snails, sea otters, some birds, fish (including wolf eels), and people. Sea urchins mainly graze on algae and undersea vegetation, such as kelp. Once at the surface, they often eat by placing the food on their stomachs, and then placing a rock on their stomachs and then smashing the prey on the rock to open it and get at the flesh inside. Sea urchins belong to echinoderm animals, at present more than 940 species are known. How to prepare sea urchins. Mostly nocturnal so you do not really see them much or moving around. One of my favorite people in France is Nancy McGee, contributor to the Barefoot Blogger’s Absolutely Southern French Food and Etiquette page. Sea urchins are omnivorous animals, which means what do sea urchins eat can be mainly categorized as plant and animal matter. Sea urchins eat endlessly as long as there is food they are eating. Diet of the Sea Urchin. Sea otters are one of the only mammals that are been known to use tools to obtain and eat their prey. Below … Sea urchins have even been found at depts greater than 6,850 meters! Red sea urchin, aka giant purple sea urchin (Strongylocentrotus or Mesocentrotus franciscanus) is the largest commonly available urchin at seven inches in diameter. Sea urchins can be found in warm waters, among corals, and also in the oceans, at a depth of up to 7 kilometers. Sea urchin These echinoderms may not look too appetizing given their spiny exteriors, but they are prized around the world for their fishy-flavored roe and flesh. Green sea urchins are the most popular for eating. Sea urchins were once known as ‘sea hedgehogs’ – urchin being an old word for hedgehog. Crabs have a feast with the urchins by picking away at their spine to get to the inside flesh. Its sharp teeth can scrape algae off rocks, and grind up plankton , kelp , periwinkles , and sometimes even barnacles and mussels . Sea urchins, which live in sandy or soft ground, eat silt and sand, swallowing with it microscopic organisms. Sea urchin primarily feed on algae attached to coral and rocks, but they also grind and eat plankton, kelp, and periwinkles. Crabs have a feast with the urchins by picking away at their spine to get to the inside flesh. They have also been known to feed on sponges, sea stars, mussels, sea cucumbers, carrion, and polychaete worms. They eat by using their 5 teeth, which are arrayed in a circular form, called an Aristotle's lantern, to scrape their food off of a hard surface, like a rock. They eat the algae growing in slat water tanks and the ocean. The mouth of the sea urchin is found in the middle on the underside of the sea urchin's body and has five tooth-like plates for feeding.