Acanthaster planci
Encounter Rate
Spotting Difficulty
Best Season
Year-round
Depth Range
1-30 meters
The crown-of-thorns starfish is one of the most ecologically significant — and feared — invertebrates on Komodo's reefs. This large, multi-armed sea star, reaching up to 50 centimetres across, is covered in sharp, venomous spines that can deliver a painful and long-lasting sting to unwary divers. It is a voracious predator of hard corals, climbing onto living coral colonies and everting its stomach directly onto the surface to digest the coral polyps and tissue, leaving behind only the white calcium carbonate skeleton. In healthy reef systems like Komodo, crown-of-thorns starfish exist in balanced numbers and play a natural role by selectively removing faster-growing corals, thereby maintaining diversity. However, population explosions — possibly triggered by nutrient runoff and overfishing of their predators — can devastate entire reef systems. In Komodo, natural predators including the Napoleon wrasse, titan triggerfish, and giant triton snail help keep populations in check. The presence of these predators in healthy numbers is one reason Komodo's reefs remain largely intact despite the global threat these starfish pose elsewhere.
Average Size
25-35cm diameter
Size Range
10-50cm diameter
Maximum Size
50cm diameter
Specialist coral predator that feeds by everting its stomach onto living hard coral surfaces. Digests coral tissue and polyps externally, leaving behind only the white skeleton.
The crown-of-thorns starfish is one of the most ecologically significant — and feared — invertebrates on Komodo's reefs. This large, multi-armed sea star, reaching up to 50 centimetres across, is covered in sharp, venomous spines that can deliver a painful and long-lasting sting to unwary divers. It is a voracious predator of hard corals, climbing onto living coral colonies and everting its stomach directly onto the surface to digest the coral polyps and tissue, leaving behind only the white calcium carbonate skeleton. In healthy reef systems like Komodo, crown-of-thorns starfish exist in balanced numbers and play a natural role by selectively removing faster-growing corals, thereby maintaining diversity. However, population explosions — possibly triggered by nutrient runoff and overfishing of their predators — can devastate entire reef systems. In Komodo, natural predators including the Napoleon wrasse, titan triggerfish, and giant triton snail help keep populations in check. The presence of these predators in healthy numbers is one reason Komodo's reefs remain largely intact despite the global threat these starfish pose elsewhere.
This species plays an important role in the marine ecosystem of Komodo National Park. Responsible diving practices help protect these animals and their habitat for future generations.
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Very painful. The venomous spines penetrate easily and cause intense, throbbing pain, swelling, and nausea that can last for hours or days. Spine fragments can remain embedded in the skin. Immerse the wound in hot water and seek medical treatment.
