Types of sea urchins

Author: Laura McKinney
Date Of Creation: 7 August 2021
Update Date: 6 November 2024
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Facts: The Sea Urchin
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Echinoids, commonly known as sea urchins and sea biscuits, are part of the Echinoidea class. The main characteristics of the sea urchin include its rounded and globose shape in some species and, of course, its famous spines. However, other species of sea urchins can have round and flat bodies.

The sea urchin has a limestone skeleton, which gives shape to your body, and this in turn is made up of plates that protect its interior like a shell and from where they come out thorns or spikes who have mobility. They inhabit all the world's seas, reaching the bottom of the sea up to almost 3,000 meters deep, and they feed on a wide variety of fish, algae and other invertebrates. Furthermore, they display a wide variety of colors, which makes them even more fascinating.


of about 950 existing species, two types of sea urchins can be found: on the one hand, regular sea urchins, spherical in shape and with the body covered by numerous spines of different lengths; on the other hand, the irregular, flattened urchins and with much fewer shorter spines are called sea wafers. Have you ever wondered what the types of sea urchins? If you want to know the types and characteristics of each one, as well as examples, don't miss this PeritoAnimal article!

Regular Sea Urchin Types

Among the regular sea urchins, that is, those with a spherical body and full of spines, the most common species are the following:

1. Common sea urchin (Paracentrotus lividus)

This species, also known as sea ​​chestnut, is one of the most common in the Mediterranean Sea, in addition to being present in the Atlantic Ocean, where it inhabits rocky bottoms and marine meadows. It is common to find them at depths of up to 30 meters, and they are able to break soft rocks with their thorns and then enter the holes they produce. Its spherical body measures about 7 cm in diameter and presents wide range of colors, may have shades of brown, greenish, blue and purple.


You might be interested in this other article about endangered marine animals.

2. Large sea urchin (Echinus esculentus)

Also known as edible european hedgehog, this species is found along the entire coast of Europe. It can usually live at more than 1,000 meters deep and frequent areas with hard and rocky substrates. Its diameter varies between 10 to 17 cm and has very short spines with purple tips. The rest of the body has a Red color striking, although it can vary from pink to pale purple or with greenish tones.

It is a species classified as "almost threatened" by the IUCN (International Union for the Conservation of Nature) due to the overexploitation of fishing activity, since it is a species consumed by man.


3. Green Sea Urchin (Psammechinus miliaris)

Also known as coast sea urchin, this species is distributed in the Atlantic Ocean, being very common in the North Sea. Usually this species lives up to 100 meters deep, in rocky areas with an abundance of algae. In fact, it is very common to find it associated with brown algae. It is also very common in seagrass and oyster beds. It measures about 6 cm in diameter and the color of its carapace is grayish brown, while their thorns are green with purple tips.

If, in addition to sea urchins, you are also interested in octopuses, don't miss this article with 20 fun facts about octopuses based on scientific studies.

4. Fire urchin (Astropyga radiata)

This species is distributed over the Indian and Pacific oceans, generally at depths that do not exceed 30 meters and preferably with sandy bottoms. It also inhabits barrier reef areas. It's a big species and its coloring ranges from dark red to light colors like beige, however there are also individuals that are black, purple or orange.

its long thorns red or black, that too are poisonous and they serve for defense, they are grouped in such a way that some regions of the body are uncovered, and a V-shape can be seen. The thorns also have an iridescence, in such a way that they seem to glow. The diameter of its body can exceed 20 cm and, added to its thorns of about 5 cm, makes the fire urchin a very striking and imposing species.

5. Black Sea Urchin (Antillarum diadem)

Also known as long-thorned hedgehog, this species inhabits the Caribbean Sea and the western Atlantic Ocean basin, where it lives in the shallow waters of coral reefs. plays a important ecological role, as they are responsible for keeping stable populations of many species of algae, which may otherwise cover corals. Is herbivorous species, but that sometimes, when your food is scarce, can become carnivorous. This type of sea urchin has a black color, and its most striking feature is the presence of long spines, which measure about 12 cm and in large individuals they can measure more than 30 cm.

Types of Irregular Sea Urchins

We will now move on to the types of irregular sea urchins, those whose bodies are flatter in shape and have fewer spines than normal sea urchins. These are the most common species of irregular sea urchins:

6. Echinocardium cordatum

This species, which does not have a popular name in Portuguese, is distributed in all seas of the world, with the exception of the polar zones. It lives up to a little more than 200 meters deep and on sandy bottoms, where its presence can be noticed because, when burying itself, there is a depression in the sand. Its body can measure about 9 cm, is heart-shaped and is completely covered by short, light, almost yellow thorns, which give the appearance of hair. He lives buried in chambers that he digs in the sand and which can reach 15 meters deep.

7. Echinocyamus pusillus

This sea urchin is distributed from Norway to Sierra Leone, including the Mediterranean Sea. usually lives in calm waters and can be observed up to 1,000 meters deep, on sandy or fine gravel bottoms. it's kind too small which normally does not exceed one centimeter in diameter and has a flattened oval shape. Its spines are short and densely grouped. This sea urchin is curious about its greenish color, although its skeleton is whitish.

8. Dendraster eccentricus

This species, which does not have a popular name in Portuguese, is American and is distributed across the Pacific Ocean, from Alaska to Baja California. It inhabits calm and shallow waters, generally in shallow depth, although it can reach a depth of about 90 meters, where it burrows into sandy bottoms and many individuals can group together. its shape is flat, allowing you to bury yourself in the sand. In general, these sea urchins measure about 8 cm, although they can reach more than 10. Its color varies from brown to purple, and your body is covered by fine hair-like spines.

9. Mellita quinquiesperforata

This species of sea biscuits is found off the coast of the Atlantic Ocean, in North America and from North Carolina to southern Brazil. It is common to see it both on sandy shores and rocky bottoms, as well as on coral reef areas, at depths greater than 150 meters. Is medium-sized species, as in general it does not exceed 10 cm. Like the rest of the sea biscuits, it is ventrally flat and has five openings at the top of the shell, that act as gills. It is covered with fine, short spines that give it a greenish-brown color.

You might also be interested in knowing what types of snails are: marine and terrestrial, which we present in this other article.

10. Leodia sexyesperforata

This species of hedgehog is native to the Atlantic Ocean, in tropical and subtropical areas, from North America to South America, where it reaches Uruguay. It lives in shallow waters and soft bottom seas, which it uses to bury itself in areas with little marine vegetation, and can be found up to 60 meters deep.

Like other species, this wafer is flattened dorsoventrally and its shape is almost pentagonal. Its size is variable, with individuals measuring from 5 cm to over 13. And as the name implies, has six holes called lunulas on the top of its shell, in addition to numerous short spines covering its body.

Other types of sea urchins

In addition to the species of sea urchins mentioned above, there are many others, such as:

  • echinus melo
  • Red Pencil Hedgehog (heterocentrotus mammillatus)
  • White Sea Urchin (gracilechinus acutus)
  • Cidaris Cidaris
  • purple spatangus
  • Stylocidaris affinis
  • Sea Potato (Brissus unicolor)
  • Purple Sea Urchin (Strongylocentrotus purpuratus)
  • Hedgehog Collector (gratilla tripneustes)
  • Green Sea Urchin (Lytechinus variegatus)
  • Mathaei Echinometer
  • Kina (Evechinus chloroticus)
  • Beach Cracker (Encope emarginate)
  • Placental Arachnoids
  • Red Sea Urchin (Asthenosoma marisrubri)

Now that you know different types of sea urchins, you can't miss this video where we present the 7 rarest marine animals in the world:

If you want to read more articles similar to Types of sea urchins, we recommend that you enter our Curiosities section of the animal world.