Sea Urchin

Sea Urchin Introduction

Sea Urchins are typically spiny, globular animals, echinoderms in the class Echinoidea. The Sea Urchin is found across the ocean floors worldwide, but rarely in the colder, polar regions.

Sea Urchins are commonly found along the rocky ocean floor in both shallow and deeper water and are also commonly found inhabiting coral reefs. There are nearly 200 different species of recognized Sea Urchin, that come in all shapes and sizes.

Some Sea Urchins are covered in long thin spikes where others have a hard shell that is made up of chalky plates. The Red Sea Urchin is the longest living creature on Earth, with some living more than 200 years. Sea Urchins are omnivorous animals and therefore eat both plant and animal matter.

The Sea Urchin mainly feeds on algae on the coral and rocks, along with decomposing matter such as dead fish, mussels, sponges and barnacles. Sea Urchins are preyed about by many predators that inhabit their marine environment, but also those animals that don’t.

The main predators of the Sea Urchin are crabs, large fish, sea otters, eels, birds and humans. In some countries, certain species of the Sea Urchin are hunted and served as a delicacy.

Keywords to learn

Echinoderms: A marine invertebrate of the phylum Echinodermata, such as a starfish, sea urchin, or sea cucumber.

Globular: Globe-shaped; spherical.

About Me

Hey Kids, my name is Sara the Sea Urchin and I am very happy to meet you. Learn more about me and my species @

Key Sea Urchin Data

  • Order:
  • Lifespan:
    15-200 years.
  • Class:
  • Scientific Name:
  • Mass:
    Information not widely known.
  • Length:
    3-10cm (1.2-3.9in).
  • Region found:
  • Population Status:
  • Current population trend:
  • Diet:
  • Sexual maturity:
    As little as 4.5 months.

Sea Urchins are weird and wonderful. They can also be inconvenient to humans when diving in the sea, as they can sting when coming into contact. They can also look like the coral, so they are hard to spot. Some of them we really spooky.

Now that you know more about the Sea Urchin by learning the key data above, be sure also to check out the fun facts. When you are finished learning the facts, try answering the questions in the Q&A corner on the bottom right side of the page.


Download questions about the Sea Urchin here: Sea Urchin (answers are on this page)


Teachers. For more in depth work sheets on the Sea Urchin. Click on Kidskonnect Worksheets

Sea Urchin Fun Facts for Kids

  • # 1. Sea Urchins also have little claw-like structure among their spines which the Sea Urchin uses for protection. These structures (known as pedicellarines) are small stinging structures that are not only used for defense and obtaining food but are also vital in keeping the body of the Sea Urchin clean.
  • # 2. The mouth of the Sea Urchin, (known as the Aristotle’s lantern) is found in the middle on the underside of the Sea Urchin’s body and has five tooth-like plates for feeding. The anus of the Sea Urchin is located on the top of the body.
  • # 3. As with other echinoderms, Sea Urchins do not have a brain and instead rely on their water-vascular system which is like a circulatory system and comprises of water-filled channels that run through the body of the Sea Urchin.
  • # 4. The average clutch size of the female Sea Urchin is around 2 million.
  • # 5. Due to dredging on the ocean floor and pollution in the water, the Sea Urchin populations are declining and the Sea Urchin and today thought to be threatened with extinction.

Q&A Corner

  • # 1. How many species of recognized Sea Urchins are there?
  • # 2. What is the name of the longest living species of Sea Urchin?
  • # 3. How long can Sea Urchins live for?
  • # 4. What is the population status of the Sea Urchin?
  • # 5. What are the two causes of the Sea Urchin being threatened with extinction?


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