9 Fascinating Facts About Sea Urchins

A group of collectors discovered a new species of sea urchin in 2006 through eBay after photos were uploaded and discussed.

Sea urchins are magnificent marine creatures that inhabit various parts of the world.

There are more than 200 species of sea urchin, and new ones are still being discovered.

These creatures play a vital role in the ocean’s ecosystem, but some species are increasingly threatened.

Here are nine intriguing facts about sea urchins that you may not have known.

The red sea urchin is the largest of all species.

Sea urchins typically grow to between 1.18 inches (3 cm) and 3.93 inches (10 cm) in diameter.

The red sea urchin is the largest species, reaching adulthood at 1.96 inches (5 cm) in diameter and continuing to grow to around 3.93 inches (10 cm).

Unlike most other sea urchins, which stop growing at around 1.96 inches (5 cm), the red sea urchin can be found in the North Pacific Ocean, from Alaska to Baja, California.

They have no bones in their body.

Sea urchins do not rely on a bone structure to support their bodies, unlike humans.

They have a shell-like structure called a “test,” which is made of calcium carbonate, similar to the structure of starfish and sand dollars, and serves as their primary form of protection.

This structure consists of small plate segments that enclose the urchin, resembling the segments of an orange.

In addition to the “test,” they have spines that help to defend them against predators.

The flower urchin is the world’s most deadly.

The flower urchin, also known as Toxopneustes pileolus, is the deadliest of all sea urchins.

The flower urchin’s venom, described in the Guinness Book of Records, contains two poisonous elements that can kill humans: Contractin A, which can cause red blood cells to clot and muscle spasms, and Peditoxin, which can cause anaphylactic shock, convulsions, and death.

When a predator steps on, touches, or brushes past the flower urchin, its “flower-shaped” spines break or pierce the predator’s skin, allowing the venom to enter the bloodstream.

Although they are a threat, adequate treatment can help victims survive a sting.

The flower urchin is most commonly found in the Indo-West Pacific region.

Some fish can develop immunity to the flower urchin’s venom.

The clownfish is one of the few species that intentionally try to build up immunity to the flower urchin’s venom.

Clownfish dance around the flower urchin, brushing themselves lightly against the spines.

This exposes them to a small amount of venom, but not enough to kill them.

After repeating this process a few times, they become immune to the venom.

You may be curious as to why clownfish choose to live among the spines of flower urchins. The reason is that the clownfish can feed on the parasites that live on the urchin, which is beneficial to both creatures. The urchin has its parasites removed, and the clownfish gets a meal.

Not only do animals eat the parasites off of sea urchins, but there are also species that eat them whole. Despite their spines and venom, sea urchins have many predators, including sea otters, crabs, fish, eels, and birds. However, humans also pose a threat to urchin populations because they are considered a delicacy in some places, particularly their roe (eggs). Overfishing has caused some species of sea urchins to become endangered.

In 2006, a British marine biologist discovered a new species of sea urchin on eBay, which he later named Coelopleurus Exquisitus, or The Exquisite Urchin, due to its striking colors and patterns. Sea urchins have just five teeth, which are held together in the center of their body and made of calcium carbonate. They also have hundreds of tiny feet called pedicellariae, which they use to grip surfaces and catch food. The oldest living sea urchin species found was the red sea urchin, which was estimated to be around 200 years old.

Sea urchins have a life expectancy of over 30 years in the wild, but in captivity, it is reduced to around 30 years. It is believed that the species may have been able to live longer in the past, but due to the changing conditions of the ocean, it has become increasingly difficult for them to survive. Despite this, they remain an important part of the ocean’s ecosystem and are a significant part of many marine creatures’ diets. However, the increasing fishing from humans and pollution of the oceans pose a significant threat to their survival. As their habitat is destroyed, some species have been listed as endangered. By reducing pollution, we can help to increase the numbers of these fascinating creatures.


1. What are urchins?

Urchins are a type of marine animal that belong to the phylum Echinodermata, which also includes starfish, sea cucumbers, and brittle stars. They are characterized by their spiny, spherical or flattened bodies and their ability to move using hundreds of tiny, tube-like feet. Urchins can be found in oceans all over the world, from shallow reefs to deep sea trenches.

2. How do urchins defend themselves?

Urchins have a unique defense mechanism that involves their spines. If they feel threatened, they can use their spines to inject a toxic substance into their predator. Some species of urchins also have sharp, venomous spines that can cause pain and swelling in humans if they are stepped on or touched.

3. What do urchins eat?

Urchins are omnivores and feed on a variety of things, including algae, seaweed, and small invertebrates. Some species of urchins are notorious for their voracious appetites and can decimate entire kelp forests if their populations are not kept in check.

4. How do urchins reproduce?

Urchins reproduce sexually, with males releasing sperm into the water and females releasing eggs. Fertilization takes place in the water, and the resulting larvae develop into juveniles before settling on the ocean floor. Some species of urchins are also capable of reproducing asexually, which allows them to quickly colonize new areas.

5. Can you eat urchins?

Yes, urchins are considered a delicacy in many parts of the world, particularly in Japan, where they are known as uni. The edible part of the urchin is the gonads, which are typically bright orange in color and have a creamy, rich flavor. However, harvesting urchins for food can have negative impacts on their populations, and overfishing has led to declines in some areas.

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