41 photos - 17 species


The spines of the sea urchins sit on small humps

and are partially movable by muscles.

The formation of the spines, their size,

function etc. can vary greatly depending on the species.

There are three main types of regular sea urchins

and ten to twelve types of irregular sea urchins.

The spines are mainly used as protection against predators such as starfish,

large snails and fish and in some species can even release poison when they bite, leather sea urchins (fire sea urchins) are particularly poisonous.

There are sea urchins that drill their spines into hard substrates

such as coral reefs and rocks.

In rare cases, food propelled by the spines is captured.

Inhabitants of sandy bottoms also use their spines for locomotion.

If you step on a spine, it may break off and get stuck in your foot,

which can lead to painful purulent inflammation.

In some species, the spines are also difficult to remove.

Asthenosoma marisrubri

Red sea fire urchin

 Maximum diameter with spines: 25 cm

This very beautiful sea urchin is extremely poisonous.

Active at night, white poison blisters at the tips of the spines,

their stings are very painful.

Photo 1 Johnny: Hurghada Egypt

Photos 2 - 3 Johnny: Lembeh Strait North - Sulawesi 

Asthenosoma varium

Fire urchin or Variable fire urchin

 Maximum size: 25 cm

Very beautiful sea urchins, but also very poisonous.

I can tell you a thing or two about it,

unfortunately I wasn't paying enough attention

when photographing one of these sea urchins

and touched one with my hand that was slightly in front of the one,

I was photographing. It was the most painful experience I've had underwater,

fire corals are nothing compared to that.

So be careful!!! 

They have a variable colouring.

Photo 1 Astrid: Bangka Island North Sulawesi

Astropyga radiata

Blue-spotted sea urchin, Red sea urchin or Radiant sea urchin

 Maximum size: 45 cm

Dark red spines standing in groups,

radial zones with rows of bright blue dots that are free of spines.

They are found on sandy soils, often in groups (photo 3).

The spines can cause painful injuries.

Photo 1 Astrid: Lembeh Strait North - Sulawesi

Photos 2 - 3 Johnny: Lembeh Strait North - Sulawesi

Photos 4 - 5 Johnny: Bangka island North - Sulawesi

 Diadema antillarum

Long-spined sea urchin


 Maximum size: 20 cm

Depth: 0 - 40 m

Common in Caribbean waters, it is a harmless algae eater, but divers,

snorkellers and bathers should be very careful with this animal.

Its fine prickly spines easily penetrate the skin and break off,

causing infections and painful wounds!

The spines of the sea urchin are dark purple to black, sometimes greyish to white.

The spines of young sea urchins can be banded.

Photo 1 Astrid: Bonaire Caribbean

Photo 2 Johnny: Hurghada Egypt

Photo 3 Johnny: Bonaire Caribbean

Diadema paucispinum

Diadema paucispinum

 Maximum diameter: 25 cm

Thanks to their spines, they are well protected from predators

and also offer many animals such as small fish or fry very good protection from predators.

Active at night, perfectly wedged into reef holes during the day.

Photo 1 Johnny: Bangka Island North Sulawesi

Diadema setosum

Diadema urchin, Black longspine urchin or Porcupine sea urchin

 Maximum diameter with spines: 50 cm

It causes painful wounds with its long poisonous spines.

It has 5 light sensory organs that can be recognised as white dots.

Often in dense groups.

Scrapes off algae.

Photo 1 Johnny: El Qesir Egypt

Photos 2 - 3 Johnny: Hurghada Egypt

Echinometra viridis

Reef urchin

 Size: 8 - 12 cm

Depth: 0 - 40 m

Found under rubble, in rocky areas and coral reefs, as well as in crevices.

Reddish-brown body with medium-length greenish spines,

a paler base and dark, often purple tips.

Photo 1 Astrid: Bonaire Caribbean

Echinothrix calamaris

Banded sea urchin or Double spined urchin

 Maximum diameter with spines: 30 cm

The spines are cross-banded and poisonous.

Inhabits shallow rock and coral reefs.

Photos 1 - 3 Johnny: Hurghada Egypt

Eucidaris tribuloides

Slate pencil urchin

 Maximum diameter with spines: 10 cm

Depth 3 - 23 m

Thick, cylindrical and blunt spines.

Light to dark reddish-brown body.

Their spines are often covered with various organisms.

Often hidden in sheltered places.

Photo 1 Astrid: Bonaire Caribbean

Heterocentrotus mamillatus

Slate pencil urchin

 Maximum diameter with spines: 30 cm

This species is wedged in reef crevices during the day and eats algae at night.

Photos 1 - 5 Johnny: Hurghada Egypt

Photos 6 - 7 Johnny: Moalboal Philippines

Lytechinus williamsi

Jewel urchin

 Maximum size: 5 - 8 cm

Maximum depth: 3 - 25 m

Round body, densely overgrown with short spines that fade from green to white.

Fine red lines and purple-coloured pods are clearly visible between the spines.

Food: algae

Photo 1 Astrid: Bonaire Caribbean

Mespilia globulus

Tuxedo urchin, Sphere urchin or Globe urchin

 Maximum size: 6 cm 

5 or 10 spiny bands, with a blue field without spines in between.

At home on rubble and hard ground, where it scrapes off algae.

Photo 1 Johnny: Bangka Island North - Sulawesi

Photo 2 Astrid: Moalboal Philippines

Metalia sternalis

Sea urchin

 Maximum length: 5 cm

Maximum depth: 5 - 25 m

The fine spines/hairs that the heart sea urchin has all over its body are striking,

presumably for its protection.

Like all heart urchins, it lives buried in the sand.

Photos 1 - 2 Johnny: Bangka Island North - Sulawesi

Microcyphus rousseaui

Bald-patch urchin

Maximum diameter with spines: 5 cm

It has 5 zigzag lines around its body, they have no spines at these points.

Lives among seaweed, rubble and rocks.

Rarely found.

Photos 1 - 2 Johnny: Hurghada Egypt 

Parasalenia gratiosa

Red urchin

 Maximum diameter with spines: 5 cm

This hedgehog is usually found in water depths of up to 70 metres.

Photo 1 Johnny: El Qesir Egypt

Photos 2 - 3 Johnny: Bali Indonesia

Tripneustes gratilla

Pincushion hairy urchin, Cake sea urchin or Sea lamington

 Maximum size: 12 cm

Depth: up to 25 m

Venomous, pincer-like appendages.

Variable colours: from cream to red or black.

Often camouflages itself with waste material.

Photos 1 - 2 Johnny: Hurghada Egypt

Tripneustes ventricosus

West indian sea egg

 Maximum diameter with spines: 15 cm

Depth: 0 - 10 m

Densely covered with short, white spines.

The body is mostly black, but there are also dark purple or reddish-brown ones.

Found in seagrass beds, sometimes also in shallow reefs.

Photo 1 Johnny: Bonaire Caribbean