What Do Sea Urchins Eat and How?

Sea Urchins are from a family of omnivores, which means they will eat plants and animals. They love to have jellyfish, barnacles, algae, and much more in their diet. On the bottom of the shell, they have a mouth, including sharp teeth, which enables them to eat.

Exciting and adventurous, right? Yes, knowing more about this ocean creature relieves one from the thirst for mystery. So, let’s dive into the sea of mystery and discover more about Sea Urchins’ eating habits and eating systems.

Sea Urchins Eating Adaptation

The sea urchin is a slow-moving animal with a prominent appearance. It is covered with hundreds of sharp spines that protect it from potential predator attacks.

How Are the Parts of Sea Urchins’ Anatomy Adapted for Eating?

As an herbivore, the sea urchin has adapted to rocky tidepools by developing five very sharp, hard teeth to scrape minute algae plants off the rocks. It also uses its hard teeth to grind away the stones and burrow a home in the rock.

Scraping can wear down their plate-like teeth. So, the urchins grow new teeth to replace their worn-out ones.

sea urchin

It uses the burrowed home and its long suction tube feet and spines to protect itself when the waves come.

Sea urchins have tubed feet that hang on to the bottom as they eat. ~ WHOI.edu

What is a Sea Urchin’s Favorite Food?

All sea creatures depend on its food cycle and among the food cycle, they love to have their favorite food item in their daily diet.

But do you know what is recognized as the favorite food of sea urchins?

Here I will show you a list of sea urchin’s favorite food I found in my research.

Also See: Do Sea Urchins Feel Pain? What do Scientists Say?

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A List of sea urchins’ favorite food:

Sea urchins are opportunistic feeders that feed on anything that passes by. Here are some of the common foods constituting a sea urchins’ diet:

a) Kelp:

Sea urchins are commonly found in areas where kelp is in abundant supply. These animals live in crevices and eat loose bits of kelp floating nearby.

They use their webbed feet to keep themselves anchored to the bottom of the ocean and eat kelp plants, eating through their holdfasts.

b) Phytoplankton/ Seaweed:

Sea urchins are browsing animals. They eat organic matter, including phytoplankton, in the sand or mud.

These animals eat seaweed which keeps coral reefs healthy and thriving.

Did you know? Seaweed and algae are sea urchins’ most common sources of food. ~ Source

c) Algae:

Research suggests that a single sea urchin can eat nearly 30 grams of algae daily. ~ Source

Sea urchins are important pieces of the ecosystem that control the growth of algae in the ocean.

d) Periwinkles:

A Periwinkle is an edible whelk, also known as a sea snail. Sea urchins have sharp teeth, which help them grind and eat periwinkle.

e) Barnacles:

Barnacles belong to the crustacean family. These tiny sticky beings are related to crabs and lobsters. They tend to live in shallow water and grow on solid surfaces.

Sea urchins use their sharp teeth to scrape them off rocks.

g) Mussels:

Sea urchins feed on creatures that are smaller than them. In some cases, they may even eat mussels, commonly known as clams.

What Do Baby Sea Urchins Eat?

Baby sea urchins have a natural tendency to eat large amounts of food. Even if they are bred in captivity, they eat a lot.

They primarily eat algae and tiny sea creatures such as barnacles, mussels, chitons, limpets, etc. Baby sea urchins prefer to eat seaweed. Baby sea urchins help eliminate excess algae.

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Younger sea urchins don’t hunt their prey. Instead, they consume the smaller sea creatures floating around them. ~ American Tarantula and Animals

How Do Sea Urchins Eat? Do Sea Urchins Have Teeth?

Sea urchins have sensory receptors in their tube feet which helps them detect the presence of kelp and carry it to their mouth for feeding.

sea urchin

Do sea urchins have mouths?

Yes, sea urchins have mouths that are located underneath their bodies. Sea urchins excrete any waste through their anuses which are situated on top of their bodies.

Where is the mouth located?

Sea urchins depend on Aristotle’s lantern, a structure consisting of five hard plates, to consume their food. These plates connect together like a beak.

They use these plates to scrape off algae from rocks and other hard structures, which may wear them out. So, the urchins grow a new set of these plates as a replacement. ~ WHOI.edu

How Much do Sea Urchins Eat?

Sea urchins eat varying amounts of food, whether alone or in herds. They eat kelp at a rate of 30 feet per month in herds.

In one day, individual sea urchins eat 30 grams of algae which is equal to 2 cups of seaweed.

These animals play a vital role in maintaining the sea’s growth of seaweed and algae.

What Do Sea Urchins Eat in An Aquarium?

Sea urchins are primarily vegetarians, while some subspecies are omnivores. When bred in captivity, brown seaweed is the best food to give them. They will also eat giant kelp, egregia, and laminaria.

You can also feed them carrots or potatoes as a substitute for brown seaweed. Meat should be avoided because it will leave the tank foul and messy.

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Did you know? If not fed enough, sea urchins will eat each other. So, it’s important to ensure they are given adequate quantities of food to keep them full. They reabsorb their gametes if they are not given food for long periods ~ Stanford.edu.pk.

What Do Purple Sea Urchins Eat?

The diet of brown urchins consists of brown and red algae. They also feed on decaying plant and animal matter.

Their tube feet help in eating and detecting the presence of food, thanks to the sensory receptors.

What Do Red Sea Urchins Eat?

Red sea urchins eat smaller foods and diatoms at young ages. As adults, their preferred food is kelp and forms of algae found on kelp beds. They mostly eat Nereocystis or Macrocystis kelp.

Did you know? Larvae of red sea urchins use cilia to wipe off kelp into their mouths. ~ Alaska Department of Fish and Game


Do sea urchins eat meat? 

Sea urchins are considered omnivores and may eat meat in some cases.

What do sea urchins eat in Alaska?

In the wild, sea urchins eat kelp and other algae. They may also eat fish and invertebrates.

How does kelp affect sea urchins?

Sea urchins completely wipe off kelp from the ocean. They live in crevices and eat loose bits of kelp.


Who doesn’t like sea urchins? They are not just great-tasting seafood, but they also maintain marine ecosystems all over the world. Sea urchins are mesmerizing creatures that perform fascinating actions.

But sometimes, we must remember to research the basics: what sea urchins eat and how? I hope this article cleared your confusion and answered these questions.

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