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Crown-of-thorns starfish vision revealed for the first time

Crown-of-thorns starfish vision revealed for the first time


“All the better to see the reef with, my dear.” Crown-of-thorns starfish (Acanthaser planci) vision has been examined for the first time, revealing their ability to discern reef structures from open water.

Scientists are looking for physical vulnerabilities in the coral-eating Crown-of-Thorns Starfish (COTS) in order to mitigate their harmful impacts on coral reefs when in plague numbers. In their pursuit of an Achilles heel, scientists have focussed on the animal’s ability to perceive its environment through its senses. Research has already demonstrated that adult COTS have a well-developed sense of smell, touch and taste. Better understanding these aspects of COTS biology may lead to new methods to either disperse or attract them in order to control their numbers.

Recently, research collaborators working with AIMS scientists discovered that adult COTS also have a well-developed sense of sight. At the end of each of their 12 to 15 arms there is an eye which can form rudimentary images of its immediate environment. In effect, a COTS has ‘surround vision’, and can detect large stationary objects against a blue ocean background. Although they are not capable of high resolution image formation, they are capable of seeing where a suitable hideout might be to avoid open areas and minimise exposure to predators. 

 

A COTS can see areas of contrast in its immediate environment, allowing it to distinguish between open environments and places to shelter over short distances. Images 'c' and 'd' simulate what a COTS perceives of the environments in images 'a' and 'b'. Images: Anders Garm and Ronald Petie

The study also found that COTS can see slow moving objects, such as the predatory snail, the Pacific triton (Charonia tritonis). Using their sense of sight, COTS are capable of detecting an approaching object, which is to its benefit as it could be it primary predation, the triton snail. If needed, they can coordinate their thousands of tube feet to escape from the approaching object – which might be planning on making a meal of it.

More information about COTS research at AIMS can be found on our website.

This research appears in the open-access paper, ‘Visual orientation by the crown-of-thorns starfish (Acanthaster planci)' in Coral Reefs and was a collaboration between the University of Copenhagen and AIMS.

Dr Mike Hall

Research Scientist

Australian Institute of Marine Science

P: +61 (7) 4753 4308 M: +61 (0) 407 553 408

m.hall@aims.gov.au 

A close-up image of a COTS eye. COTS have lens-less, simple, compound eyes that can form rudimentary images of their immediate environment. Image: Anders Garm

A COTS eye located at the tip of the starfish’s arm. The eye is near the base of a modified tube foot. Image: Anders Garm