These massive, multi-armed predators crawl across tropical reefs, everting their stomachs to digest living coral tissue directly off the limestone skeleton. Covered in hundreds of sharp, venom-tipped spines, they play a dual role as natural reef sculptors and devastating pests during population explosions. Healthy reefs can support small numbers, but massive outbreaks can strip entire coral communities bare in a matter of weeks.
Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Key facts
Diet & prey
Stony corals
Acropora corals
Pocillopora corals
Predators
Giant Triton
Harlequin Shrimp
Humphead Wrasse
ThreatsAgricultural runoff, coastal development, and overfishing of natural predators
HabitatsTropical coral reefs, lagoons, and seaward reef slopes
Life span15 to 17 years
Size / weightNot available
Classification
FamilyAcanthasteridae
SpeciesAcanthaster planci
Range & activity
Range data is not available yet.
Safe observation
Interaction riskVery high
Low
Moderate
High
Very high
Why interaction risk is very high
Spines contain venom that causes severe pain and swelling; do not touch.
Why it is dangerous
The sharp spines are coated with a toxic mucus containing saponins and plancitoxins, which cause intense pain, nausea, and potential secondary infections if they puncture the skin.
How to recognize a risky encounter
Look for a large, multi-armed starfish covered in long, reddish-brown or purplish spines, often found directly on bleached or damaged coral heads.
What to do
Never touch or step on this starfish; if punctured, seek immediate medical attention and submerge the wound in hot water to help denature the venom.
Responsible observation
Keep your distance: Maintain at least two meters of clearance while diving to avoid accidental contact with the spines.
Report outbreaks: Log sightings with local reef management authorities to help track population surges.
Do not handle: Never attempt to touch, move, or harvest these starfish without professional training and equipment.
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