Sea Urchins : Facts, Species And Habitat

sea urchins in Marine Life
Sea Urchins are beautiful creatures that belong to a marine family known as Echinoderms and can be found in oceans almost around the world. There are almost 200 species of them has been identified but, scientists still discovering many other species. Their presence is very important for the oceanic ecosystem. Some of these spiky ocean dwellers prefer shallow coral reefs whereas others prefer deep sea rocky surfaces. They are very interesting and peculiar as you read some unknown facts about them.

1. Sea urchins can be of many sizes and colors as well. They are usually 1.2 inches in diameter and coloration differs from black, brown, purple, green and red. They have sphere like shape of the body, which is covered with large number of long spines and bony plates. These shell like structures are called ‘Test‘.

various sea urchins
Image By Jeff Rotman Via Science


The Red sea urchins are the biggest and grow at 3.9 inches in diameter. They can be found in the North Pacific Ocean, from north Alaska to south Baja and California.


Image Via Wikimedia

They have 5 rows of paired tube feet at the bottom of their body called Pedicellariae. These feet end with suckers which are used to grip on rocks, movement on the ocean floor or to hunt for food.

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4. These creatures have claw like structures on the surface of their body, scattered among the spines. Their main purpose is to protect from predators.


Flower Urchin
Image By François Michonneau Via Wikipedia

Certain species of sea urchins like the Flower Urchin have spikes filled with venom. This venom contains Contraction A, which cause red blood cells to clot, whereas Peditoxin causes anaphylactic shock, convulsions and death. Their sting can pierce through skin and inject the venom directly into bloodstream that can kill a human. These urchins can be seen in the Indo-west Pacific region.

Image By Frédéric Ducarme Via Wikipedia

Other species specifically of the families Diadematidae and Echinothuriidae also can inflict very painful stings with their venom. A typical sting can cause redness and swelling and may cause further infection if left untreated. However, multiple puncture wounds can cause muscle aches, paralysis, shock, respiratory failure and death.

Image By Candace Pratt Via Wikipedia


Image Via The Living Coast

They have specially designed mouth, called “Aristotle’s lantern“. This mouth is equipped with five sharp teeth with different jaw, which are movable independently. Also these teeth are very sharp and tough to drill holes in rock.

Also Read: Everything About Various Birds

7. Sea urchins are omnivores, meaning they eat both plants and animals. Sea weed, algae, plankton and decaying organic matter dropped by other marine creatures are usually on their menu.


baby sea urchins
Image Via Deviant Art

Mating season takes place in the spring. Just like some other sea creatures, sea urchins reproduce by external fertilization, meaning they release eggs and sperm cells in the water. Fertilized eggs undergo several stage before it becomes adult and during the larval stage, they swim with other tiny animals as a part of zooplankton.

9. They generally live up to 30 years in the wild but, much less in captivity.But, the Red sea urchin has the longest lifespan and able to survive up to 200 years in the wild.


clown fish and sea urchins
Image Via Deposit Photos

Clown fish is the only species that built their body immune to the urchin’s venom purposely. This relationship is beneficial to both creatures as the clown fish eats the parasites and the urchin has its parasites removed. So, the clown fish gets food and safety from other predators due to the urchin’s venomous sting.

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