Fun Crown-of-thorns Starfish Facts For Kids

Divya Raghav
Oct 20, 2022 By Divya Raghav
Originally Published on Aug 19, 2021
Edited by Isobel Murphy
Fact-checked by Deeti Gupta
Read these crown-of-thorns starfish facts about the beautiful yet venomous creatures of the ocean.
Age: 3-18
Read time: 7.1 Min

The crown-of-thorns starfish (COTS) gets its name from its appearance. It has venomous spines all over its upper surface, which looks similar to the biblical 'crown of thorns'. This marine animal reaches up to 3.2 ft (1 m) in diameter, making it the world's second-largest starfish, and, when it comes to the crown-of-thorns starfish origin, they are naturally occurring and are found in Indo-Pacific oceans including the Red Sea and the Indian and Pacific oceans.

Like most starfishes, if a crown-of-thorns starfish happens to lose an arm, it can regrow it within half a year! An adult COTS can also survive without eating for up to nine months. COTS play an important role in maintaining coral species diversities in their ecosystem with their periodic outbreaks. In some situations, these outbreaks and the resulting coral deaths are proportional to the rates at which the corals grow and recover. COTS also help to make space for slow-developing huge corals since these COTS tend to like to eat the more fast-developing corals. However, if COTS outbreaks occur frequently, their damage to coral reefs can be significant as reefs have to withstand the COTS outbreaks alongside other natural destructions too. Healthy reefs can regenerate after COTS outbreaks within 10 to 20 years. However, weaker reefs take a longer time and cannot regenerate enough before the next outbreak hits.

Crown-of-thorns starfish are an invasive species that have been able to expand on the Great Barrier Reef for multiple reasons. Lab research at AIMS has shown that the survival of COTS larvae increases drastically when phytoplankton, their food source, becomes available in large quantities. Populations of COTS producing a large number of larvae around these coral reefs are also causes of outbreaks, as are the lack of predators of these crown-of-thorns starfish due to overfishing. However, these crown-of-thorns starfish do face predators of their own. The most common crown-of-thorns starfish predators include the giant triton snail, the titan triggerfish, brilliant pufferfish, hump head Maori wrasse, yellow edge triggerfish, harlequin shrimp, and lined worm.

After reading these crown-of-thorns starfish facts, do read our wrasse and hermit crab facts too.

Crown-Of-Thorns Starfish Interesting Facts

What type of animal is a crown-of-thorns starfish?

A crown-of-thorns starfish is a large starfish sea animal.

What class of animal does a crown-of-thorns starfish belong to?

COTS belongs to the Asteroidea class of animals.

How many crown-of-thorns starfish are there in the world?

There are more than millions of these marine creatures (also known as a 'corals' eater') in the oceans.

Where does a crown-of-thorns starfish live?

The COTS is a predator of coral polyps and is an exotic animal species. It lives in the Indo-Pacific region, including in the Red Sea, the South Pacific, and in coasts of Japan and Australia. In the U.S., they are found in Hawaii too. They are found in abundance around the Great Barrier Reef in Australia.

What is a crown-of-thorns starfish's habitat?

A typical crown-of-thorns starfish habitat must include water and will be near coral reefs in the calm ocean depths. They are invertebrates that feed on corals and are known to cause huge destruction of coral habitats.

Who does crown-of-thorns starfish live with?

Crown-of-thorns starfish live in groups in oceans.

How long does a crown-of-thorns starfish live?

The life span of these species is unknown, but their growth and reproduction both decline after three to four years. An adult crown-of-thorns starfish (also known as a 'coral reefs eater') can survive nine months without feeding itself!

How do they reproduce?

COTS starfish reproduce by spawning during their breeding season. Males and females release their gametes into the sea water, and fertilization occurs. Female COTS can release more than a million eggs, and male COTS release sperm at the same time. A female can release up to 60 to 65 million eggs during a breeding season and her eggs incubate into planktonic larvae for one to two months before they settle in the ocean base. These young ocean starfish feed on coralline algae for a while before changing their diet to corals as they grow up.

What is their conservation status?

Their conservation status is currently Least Concern as the crown-of-thorns starfish population is constantly increasing, and there are no significant threats to this marine invertebrate population at the moment. Some threats that can affect the starfish outbreaks cycle are overfishing by humans and the natural predators of this marine animal (COTS) like the giant triton.

Crown-Of-Thorns Starfish Fun Facts

What do crown-of-thorns starfish look like?

A crown-of-thorns starfish (Acanthaster planci) looks like most starfish, having a central disk from which arms are extended. They have multiple soft arms (more than the typical five) that are covered in spines that make them unique. Their arms are also prehensile, which means they can grab onto things. A fully grown crown-of-thorns starfish can reach lengths of up to 10-14 in (25-35 cm) and have more than 20 arms. They also come in various colors like bluish-purple, red, gray, and green.

The crown-of-thorns starfish has a beautiful splash of colors on its body.

How cute are they?

The COTS (a predator of corals) is more intriguing and attractive than cute. Their vibrant colors like purple, gray, and green, along with its spiny body, are interesting to witness.

How do they communicate?

Not a lot is known about the way these creatures communicate. However, a recent study might shed some light as it has been observed that they communicate with each other by using chemical secretion. By studying COTS from different regions, such as COTS from the Indo-Pacific region, (who are a pest of coral reefs) and COTS around Japan, it has been concluded that both types of COTS secrete identical chemicals. They also seem to secrete different proteins when they are threatened by a predator, but a lot more is yet to be learned about these beautiful creatures of sea.

How big is a crown-of-thorns starfish?

The typical adult crown-of-thorns starfish size ranges from 10-14 in (25-35 cm). They have up to 23 arms and the long and sharp spines on the sides of the starfish's arms and upper (aboral) surface look like thistles. They make a crown-like shape, giving the animal its name. The spines can grow up to 0.13 ft (4 cm) long and are firm, sharp, and can easily penetrate through delicate surfaces.

How fast can crown-of-thorns starfish move?

A crown-of-thorns starfish (Acanthaster planci) can move at the rate of 0.013 mph (35 cm per minute).

How much does a crown-of-thorns starfish weigh?

A crown-of-thorns starfish (also known as a 'coral reef eater') weighs up to 0.4-6.6 lb (0.2-3 kg).

What are their male and female names of the species?

The species name for both male and female COTS is Acanthaster planci. They do not have gender-specific names.

What would you call a baby crown-of-thorns starfish?

A baby COTS could simply be called a baby crown-of-thorns starfish or larva.

What do they eat?

A typical crown-of-thorns starfish diet includes hard corals, soft corals such as coral polyps, algae, and sponges.

How did it get its name?

The crown-of-thorns starfish (coral reef eater) gets its name from its venomous thorn-like spines covering its upper surface. These look a little like the biblical crown of thorns.

Would they make a good pet?

No, they cannot be a pet as they live in the oceans and help to maintain a balance in their habitats. Crown-of-thorns starfish act as predators and feed on a large number of corals. They can only survive in the ocean depths, where they can feed on large quantities of corals.

Did you know...

One of the best crown-of-thorns starfish facts for kids is that crown-of-thorns starfish feed on their prey, coral reef, by expelling their stomachs out from their bodies, covering the corals!

Crown-of-thorns starfish are nocturnal and can consume 53.8-140 square ft (5-13 square m) of corals per year. COTS are the major reason for the destruction of reefs in the Australian Great Barrier Reef.

The crown-of-thorns starfish poison includes a chemical compound named saponin, which is poisonous for both humans and fish. A crown-of-thorns starfish sting can cause numbness, tingling, nausea, and body pain.

AIMS runs a significant COTS checking program on the Great Barrier Reef. This drawn-out program has shown that outbreaks start in the north and relocate toward the south over around 15 years, with the ocean moving larvae between reefs.

Why is the crown-of-thorns starfish a problem?

The crown-of-thorns starfish eating coral can be a problem. Under certain conditions, this sea star can experience outbreaks resulting in massive destruction to coral reefs, impacting the very important coral cover. Corals reefs are important for many species who live underwater, and they also help decrease the power at which the waves hit our shores.

Can a crown-of-thorns starfish kill a human?

No, crown-of-thorns starfish (coral reef eater fish) poison can not kill humans, but their spines do contain neurotoxin and starfish poison which is dangerous to both humans and marine creatures.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other arthropods, including the ground beetle or the American dagger moth.

You can even occupy yourself at home by drawing one on our crown-of-thorns starfish coloring pages.

Crown-Of-Thorns Starfish Facts

What Did They Prey On?

Great Barrier Reef stony coral polyps (Scleractinia) and algae

What Type of Animal were they?


Average Litter Size?

50 million

How Much Did They Weigh?

0.4-6.6 lb (0.2-3 kg)

What habitat Do they Live In?


Where Do They Live?

indo-pacific oceans

How Long Were They?

10-14 in (25-35 cm)

How Tall Were They?

1.4-1.9 in (4-5 cm)







Scientific Name

Acanthaster planci

What Do They Look Like?

Brown, gray, green, or purple

Skin Type

Membranous and soft

What Are Their Main Threats?

pollution, climate change, and overfishing

What is their Conservation Status?

Least Concern
We Want Your Photos!
We Want Your Photos!

We Want Your Photos!

Do you have a photo you are happy to share that would improve this article?
Email your photos

More for You


See All

Written by Divya Raghav

Bachelor of Commerce specializing in Accounting and Finance, Master of Business Administration

Divya Raghav picture

Divya RaghavBachelor of Commerce specializing in Accounting and Finance, Master of Business Administration

With a diverse range of experience in finance, administration, and operations, Divya is a diligent worker known for her attention to detail. Born and raised in Bangalore, she completed her Bachelor's in Commerce from Christ University and is now pursuing an MBA at Narsee Monjee Institute of Management Studies, Bangalore. Along with her professional pursuits, Divya has a passion for baking, dancing, and writing content. She is also an avid animal lover who dedicates her time to volunteering for animal welfare causes.

Read full bio >