What Do Sea Urchins Eat?

Sea urchins are spiny animals that live on the bottom of the sea. While sea urchins aren’t known to be nimble hunters — moving slowly on tube feet – their diet may surprise you.

Let’s dig into what sea urchins eat and how this class of animals have managed to thrive for hundreds of millions of years.

How Sea Urchins Eat

Sea urchins are a class of animals with roughly 950 species, although with sea urchin species existing down to three miles below the ocean’s surface, its likely hundreds of sea urchin species have yet to be classified.

While sea urchins might not look as complex as giant species like whales or beautifully colored fish, they’re a marvel of evolution and have thrived for more than 450 million years. Sea urchins have been so successful because their spines and thick exterior efficiently protects them from many predators.

Sea urchins have a mouth on the bottom of their shell that’s surrounded by tube feet. Since the mouth is facing the ground, it’s rarely exposed to predators. The mouth of sea urchins can grasp and tear, allowing the species to eat a variety of food sources. Most sea urchins have five “teeth” that resemble plates in their mouth and a fleshy surface that is similar to a tongue.

What do Sea Urchins Eat?

Sea urchins are omnivores that eat a diverse diet. The diet of what sea urchins eat includes:

• Algae
• Plankton
• Sponges
• Mussels
• Kelp
• Feather stars
• Barnacles
• Moss animals
• Jellyfish
• Fish (Deceased)

The bottom line is that sea urchins are opportunistic. While the majority of their diet is plants, such as algae and kelp, they’ll also eat whatever prey is available. Video of sea urchins have shown them feasting on dead fish and some sea urchin species may even be far more active predators than previously thought!

What Eats Sea Urchins?

While sea urchins are protected by their shells, they do have a number of predators. There are a number of animals that eat sea urchins:

• Sea otters
• Lobsters
• Birds
• Sea stars
• Crabs
• Wolf eels
• Wrasse
• Sheephead fish

Wolf eels in particular have evolved to hunt sea urchins. Its important that sea urchins have natural predators, as they can quickly strip areas of algae and other fauna necessary for a thriving ecosystem.

In addition to all these predators, humans have developed a taste for sea urchins. Japanese cooking refers to sea urchin as uni, and the gonad (or genital gland) of sea urchins is a delicacy. The majority of worldwide sea urchin consumption is in Japan, but the species is used in cooking across many worldwide cultures.