What Do Sea Urchins Eat?

Written by AZ Animals Staff
Updated: September 18, 2022
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What do Sea Urchins Eat
Sea urchins are omnivores that eat a diet that includes algae, barnacles, jellyfish, and much more!

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Key Points 

  • When they are not being used as a suit of armor by the carrier crab, sea urchins seek out their favorite foods.
  • These echinoderms enjoy a wide range of variety and nibble on algae and even marine mollusks.
  • Incidentally, they’re also in high demand by several species which consider them a tasty delicacy.

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 urchin eat - sea urchin mouth
A close up of a sea urchin’s mouth showing its five teeth

narupong sooknatee/Shutterstock.com

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 do sea urchins eat - purple sea urchin
Sea urchins come in a variety of shapes and sizes

HotFlash/Shutterstock.com

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:

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.

As a matter of fact the archipelago is believed to import 80% of the global catch.

Considered to be a creamy, savory, and salty delicacy, sea urchins are also enjoyed in California where indulging in them is actually considered a worthy conservation effort.

This is due to the fact that these ravenous echinoderms have been reported to have decimated 95% of the algae underwater forests along Mendocino’s coastline.

Where else are sea urchins enjoyed as a local staple?

The Mediterranean coast, Korea, and China.

What do sea urchins eat - Uni
Uni is a delicacy in many cultures, but is especially popular in Japan

Sabino Parente/Shutterstock.com

Up Next…

Keep reading these posts for more incredible information about key animal facts.

  • What Do Whale Sharks Eat?: They’re sharks, but not the vicious predators everyone’s used to. Sedate and slow-moving, they love to tuck tons of food away. Find out their favorite as well as other stuff they love to eat. 
  • What Do Hammerhead Sharks Eat?: Like other members of their vast family, these sharks love to eat. Discover all about their dietary habits here and that one species with a penchant for snacking on vegetation.

Top 10 Animals That Have Shells - sea urchin
Sea urchins use their spiked shells to protect themselves from predators.
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AZ Animals is a growing team of animals experts, researchers, farmers, conservationists, writers, editors, and -- of course -- pet owners who have come together to help you better understand the animal kingdom and how we interact.

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