Exploring the Fascinating Diet of Sea Urchins: Nature’s Spiny Omnivores

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 has managed to thrive for hundreds of millions of years.

How Sea Urchins Eat: Hidden Mouths

Sea urchins are a class of animals with roughly 950 species. However, with sea urchin species existing down to three miles below the ocean’s surface, there are likely hundreds of sea urchin species that 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 successful due to their protective spines, diverse diet, and adaptability to various marine environments.

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 sea urchins 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. Videos of sea urchins have shown them feasting on dead fish. 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, including:

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

Wolf eels in particular have evolved to hunt sea urchins. It’s 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. Japan is one of the major consumers of sea urchins, along with countries like South Korea, China, and Italy.