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Fish & sea life · Habitats

Crown-of-thorns starfish

It doesn’t eat reefs—it eats coral polyps, one colony at a time, with venomous spines that make it impossible to ignore.

Worth your time?4/5Yes.See the whole thing.What works, what does not, who it is for ↓
9:04in productionCh. 1 · Why it’s called ‘crown-of-thorns’/ 9:04 · ceiling 15 min
4 chapters · 9:04Ceiling 15:00

The brief is written and checked. The video joins this page when it is cut.4 chapters · 1 min read · 9:04 planned

Read the brief

The crown-of-thorns starfish is a large, venom-spined, corallivorous echinoderm found exclusively on Indo-Pacific coral reefs. It feeds solely on hard coral polyps. Its morphology and ecology are tightly coupled to coral survival. Nothing in the sources describes its reproduction, lifespan, population trends, or human management responses.

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Chapters & takeaways4
  1. 0:52
    Why it’s called ‘crown-of-thorns’

    Its name comes from long, sharp, venomous spines that form a crown-like shape across its upper surface and arms.

  2. 2:17
    Where it lives and what it eats

    It only lives where hard coral communities exist—and only eats hard coral polyps.

  3. 3:55
    How far it spreads—and how big it gets

    It ranges from the Red Sea to Central America’s Pacific coast—and adults reach 25–35 cm.

  4. 5:26
    Size and structure

    It is one of the largest starfish in the world—and has up to 21 arms.

1 more chapterFewer chapters
Worth your time?

Yes. See the whole thing.

4/ 5
What works
  • Feeds on hard coral polyps.
  • Moves across reefs.
  • Uses venomous, thornlike spines for defence.
  • Grows to 25–35 cm with up to 21 arms.
What does not
  • It does not occur outside coral reef or hard coral communities.
  • It does not feed on soft corals, algae, or fish.
  • It does not inhabit temperate or polar waters.
  • It does not have fewer than 5 arms or exceed 35 cm as an adult.
See it if
  • Reef divers.
  • Marine biologists.
  • Coral reef managers working from the Red Sea to Central America’s Pacific coast.
Skip it if
  • Freshwater ecologists.
  • Temperate-zone naturalists.
  • Anyone studying non-coral benthic systems.
Who should see it, and who should skipHide who it is for
The written brief1 min read

What the species is and where it came from

Acanthaster planci is a large, corallivorous starfish native to the tropical and subtropical Indo-Pacific. It is named for venomous, thornlike spines covering its upper surface and arms.

How it works, in terms someone would actually use

It feeds on hard coral polyps. It moves across reefs. Its venomous, thornlike spines cover its upper surface and arms. It grows to 25–35 cm. It has up to 21 arms.

What it gets right

It gets right the morphological defence: long, sharp, venomous spines that form a crown-like shape. It gets right the ecological niche: strict dependence on hard coral polyps for food and on coral reef habitats for survival.

What it does not

It does not occur outside coral reef or hard coral communities. It does not feed on soft corals, algae, or fish. It does not inhabit temperate or polar waters. It does not have fewer than 5 arms or exceed 35 cm as an adult.

What it changed

Nothing is stated in the sources about what it changed.

Who it is for, and who it is not

It is for reef divers, marine biologists, and coral reef managers working from the Red Sea to Central America’s Pacific coast. It is not for freshwater ecologists, temperate-zone naturalists, or anyone studying non-coral benthic systems.

Is it worth your time

Yes—if you are diving or snorkelling on Indo-Pacific coral reefs and want to recognise a major coral predator by sight, spine shape, and feeding behaviour.

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