Sea Urchin

It is a fascinating aquatic creature that is only active at night. Sea Urchin is its name. They come in a range of colors to choose from. Guess what? Humans can eat them, just as lobster and crab. Yes, it’s high in protein and good fats. In Japan, the dish known as Uni is well-known. We have a lot of fascinating information on them. Read this blog to get to know them all.


  • It is a class of animals that have a stiff, generally spherical body with moveable spines.
  • Water Urchin is a little sea creature with spherical tests, or shells, that are frequently covered in porcupine-like spikes.
  • They’re available in a wide selection of colors, including black, white, red, orange, green, brown, purple, pink, yellow, blue, and gray.

Scientific Name



  • Echinoderms (spiny-skinned animals) include sea urchins, sand dollars, sea stars, and sea cucumbers.
  • Sea urchins, like those echinoderms, have pentamerous (or pentaradial) symmetry, which means “split into five sections,” as seen in a sea urchin test.


Sea Urchin Phylum

  • They are members of the Echinodermata phylum, which includes sea stars, sand dollars, sea lilies, and sea cucumbers.

Sea Urchin Class

  • The Echinoidea class includes over 950 extant species of spiny marine invertebrates.


Nocturnal Behavior

  • Many of them are nocturnal, going out of their shelters to graze at night.
  • This behavior is linked to visible predator avoidance, but it also increases exposure to nocturnal predators such as lobsters and asteroids.

Feeding Behavior

  • Anything that floats by will be eaten by this creature. With its sharp teeth, it can scrape algae off rocks and grind up plankton, kelp, periwinkles, and even barnacles and mussels.
  • Birds, sea stars, cod, lobsters, and foxes all hunt sea urchins for sustenance.



  • They range in size from 3 to 10 centimeters (1 to 4 inches), with the largest species reaching 36 centimeters (14 in).


  • It comes in a variety of colors, including black, red, brown, green, yellow, and pink.


  • They have small to lengthy spines covering them.
  • It weighs about one pound on average. 

Sea Urchin Mouth

  • Their mouth is hidden beneath their body.
  • With their beak-like jaws, they scrape algae off rocks.


  • They eat algae and kelp, which are both marine plants.
  • Water animals that are sessile, or stationary, such as coral and marine sponges, are also prey.


It can live for 15 to 200 years. 

Range & Habitat

  • From Northern Japan and Alaska to Baja California, they can be found.
  • The Red Sea Urchin is found predominantly on rocky shorelines throughout Alaska’s outer coast, with the highest densities in the south southeast.
  • They can live in depths of up to 90 meters in the intertidal zone.


  • They reproduce by dispersing egg and sperm clouds into the ocean.
  • Hundreds of millions of larvae are created, but only a small percentage of those reach the shore to mature into adults.
  • It may appear to be a dangerous life approach.

Sea Urchin Care

There are some the ways to care for this creature and they are as follows:

  • Water quality must be maintained with regular water changes and proper filtration to keep your urchin healthy.
  • Marine invertebrates are poisoned by copper-based drugs.
  • Avoid overcrowding, which is a major source of stress and illness. 


  • Their natural predators are crabs and lobsters. They are preyed upon by triggerfish and wrasse.
  • The Northern Hemisphere’s wolf eel is uniquely designed to hunt and ingest them.
  • Sea otters in places like British Columbia restrict urchins from overpopulating, which helps to maintain ecological equilibrium.

Red Sea Urchin 

  • Red Sea Urchin is a member of the Echinodermata phylum and the Echinoidea class.
  • Sea cucumbers and sand dollars belong to this phylum, and one of its shared characteristics is radial symmetry.
  • They are a uniform crimson to dark burgundy color and use their spines as stilts to creep slowly over the seabed.
  • With a maximum “test,” or outer skeleton, a diameter of more than 18 cm, and a maximum spine length of 8 cm, it is the largest of the sea urchins.

Sea Urchin Sushi

  • Uni is the Japanese word for the edible component of the sea urchin, which is served as nigiri sushi, sashimi, or as a sumptuous topping.
  • It is primarily consumed in Japan.
Sea Urchin Sushi
Sea Urchin Sushi
  • It has a slight brininess to it, but it isn’t excessively salty.
  • Fresh ones should have a sweet, salty flavor with a tinge of iron and zinc on the tongue. Uni has a strong mineral and seaweed flavor, and the texture should be creamy.
  • They have a similar nutritional profile to other types of seafood in that they’re high in protein and healthy fats.


The sting of this creature is painful. Puncture wounds on the skin are common, and if not treated promptly, they can easily become infections. The stung area may grow red and swollen. If the skin is penetrated (which happens frequently), the puncture site is usually a bruised blue-black appearance. As a result, it is critical to treat them as soon as possible. For treatment you should follow these steps: 

  • Soak the affected region for at least an hour in hot water. You can also soak the injured region in a vinegar solution and apply wet vinegar to it many times a day. It has the potential to help with pain relief.
  • If its spine has broken off and is caught in your flesh, use tweezers to pull it out.
  • If you have pedicellariae, apply shaving cream to the affected region and lightly scrape with a razor. Using soap and water, flush and cleanse the sting.


  • Spines and pedicellaria are the two types of poisonous organs found in this creature.
  • Puncture wounds are caused by the spine. Contact with the spines of sea urchins, as well as their venom, can cause a major inflammatory reaction, which can lead to.

Read also: Basking Shark

Human Interaction

  • Because they feed on dead species and help recycle resources into useful energy for other animals, Sea Urchins are an important element of our ecology.
  • Humans, on the other hand, do not interact with them directly. Yes, touching this creature is harmful to their health.
  • If you need to move one out of the way, for example, handle it with care and avoid placing too much pressure on the spines.


The famous reason by which they migrate is that the Juveniles outgrew their hiding places and migrated to the seagrass beds. 


  • These organisms live in dense groups in barren underwater environments, with populations closest to the coast being the densest.
  • While they can be found all over the world, the majority of them reside in temperate and tropical ocean ecosystems in shallows up to 10 meters deep, where the plants they eat are abundant.
  • A recent count discovered 350 million purple sea urchins on a single Oregon reef, a growth of over 10,000 percent since 2014.

Threats & Conservation 

  • some diseases are major death threats to these creatures. These illnesses are bald Sea Urchin and some certain kinds of bacterial illnesses. 
  • They are not extinct. 
  • Fisheries have always targeted the red sea urchin for its roe. Many fisheries have turned their attention to the purple sea urchin as Red Urchin landings have fallen, but because it’s small and yields less roe, a larger commercial demand hasn’t evolved.
  • Urchins and other sea animals are also killed by poor water quality. 

Fun Facts 

  • A circular inner shell, known as a test, gives the pin cushion its look.
  • “Aristotle’s lantern” refers to the toothlike plates that surround an urchin’s mouth.
  • Uni sushi is the animal’s gonads, which are generally referred to as roe, as in the eggs of a sea species.
  • It may walk by moving around the seafloor with its tube feet. It breathes through its feet.
  • On the West Coast of the United States, sea urchin grazing is slowly but steadily bringing down kelp forests.

Reference Link

Sea Urchin-FAQ

What is a Sea Urchin?

It is a small marine invertebrate that is spherical in shape and coated in spines or cilia and belongs to the Echinodermata phylum.

What does Sea Urchin taste like?

It is full of sugar, amino acid, and salts, giving them a salty and sweet taste. 

How to eat Sea Urchin?

The most typical way to consume sea urchin is raw, similar to how oysters or sushi are consumed. Enhancing the natural flavor with butter or lemon juice is a terrific way to go.

What organs do Sea Urchins have?

A water vascular system, found in all echinoderms, serves as a filtering mechanism and a fluid circulation system. Sea urchins have hundreds of tiny tube feet called podia that emerge from holes in the test and let them to move quickly.

What would happen if Sea Urchins were removed from the ecosystem?

Reefs would die if sea Urchins were no longer there due to an abundance of algae, kelp, and seaweed. Furthermore, creatures that rely on those reefs for existence will expire with the reefs. If the sea urchin population goes extinct, its predators will starve to death.

Do Sea Urchins have brains?

Although sea urchins lack brains, it’s possible that their entire neural system works as a brain. 

Is Sea Urchin safe to eat?

The gonads, the reproductive organs that are so highly appreciated on the dish, are the only portions of the urchin that are edible. In the beginning of the season, the texture of sea urchin is creamy and custardy, but as the roe develops in preparation for spawning, it becomes stiffer and more granular.