Crown-of-Thorns Sea Star (Acanthaster planci)

Also known as Asteroids, Coral-eating Starfish, Coral-feeding Starfish, Crown-of-Thorns, Crown-of-Thorns Star, Crown-of-Thorns Starfish, Starfish

Description

Also known as Asteroids, Coral-eating Starfish, Coral-feeding Starfish, Crown-of-Thorns, Crown-of-Thorns Star, Crown-of-Thorns Starfish, Starfish.

Found singly or in constellations, amongst sand and rubble areas, over coral and rocky reefs. Colour varies.
They feed on algae, gorgonians, hard and soft corals.
Length - 40cm
Depth - 0-60m
Widespread Indo-Pacific

Host to the Sea Star Shrimp - Periclimenes soror - http://www.whatsthatfish.com/fish/sea-star-shrimp/3011
Also the Tubed Cardinalfish - Siphamia tubifer
http://www.whatsthatfish.com/fish/tubed-cardinalfish/3024

The Crown-of-Thorns is beautiful to look at but fairly deadly for anything else and should be avoided at all costs because they can cause severe injury.

Crown-of-Thorns has up to 21 arms and walks on the open bottom between reefs searching for live corals to eat. They climb onto the corals extrude their stomach over them, releasing digestive enzymes to break down the coral and then absorb the liquefied tissue. Feeding alone at night, maintaining a constant distance between themselves and other crown-of-thorns sea stars.
During times of food shortage, these creatures can live on their energy reserves for over six months.
This species is at least partly responsible for much loss of coral reefs. They are voracious predators that can wipe out large areas of coral, each Crown of Thorns can consume up to six square meters of living reef per year.
Although very few predators, they include the Giant Triton (Charonia tritonis), Humphead Wrasse and Pufferfish (Arthron Hystrix)

Sea Stars have remarkable regenerative powers, when attacked and damaged by predators they are able to grow new arms. They usually have five arms but have been found with 4 or 6 arms, this may be because more than one arm has been damaged at one time!
Sometimes small parasitic limpets can be found on the underside of arms which can deform the arms.
They possess a cleverly evolved arsenal of hydraulic tube feet connected to an elaborate water-vascular system that encircles the animal's mouth and extends via five radial canals down the centre of each arm.
Their mouth is underneath, but their prey is absorbed outside their mouths by forcing out their digestive organs from their stomach.
Sea Stars are carnivores and feed on almost any food including molluscs, worms, detritus and each other!
Some sea stars like the crown of thorns can be venomous. Ref: https://en.wikipedia.org/wiki/Crown-of-thorns_starfish

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