Scientists in Australia and Japan have potentially discovered a new way of controlling outbreaks of crown-of-thorns starfish (CoTS) on coral reefs, using a synthetic version of their own ‘scent’.
Crown-of-thorns starfish (Acanthaster planci), which are found throughout the Indo-Pacific region and the Great Barrier Reef, eat coral at a rate of up to 10 square metres per year.
They prefer to eat fast-growing species of coral such as Acropora – table corals and staghorn corals – which, under normal circumstances, is thought to improve coral reef biodiversity.
Scientists estimate that a healthy coral reef can support 20-30 CoTS per hectare (10,000 square metres), but occasionally – and for reasons not yet fully understood – they grow in numbers to such an extent that their coral consumption can have a devastating effect on the surrounding reef.
Researchers have found a new, naturally derived technology that could help control outbreaks of the coral-munching crown-of-thorns starfish – by mimicking one of its own scents.
A study published in April by scientists from the University of the Sunshine Coast (UniSC), the Australian Institute of Marine Science (AIMS) and Japan’s Okinawa Institute of Science and Technology (OIST) found that CoTS use their characteristic spines to ‘smell’ chemicals secreted by other starfish.
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CoTS are well-known for their toxic spines, which contain venom that is immensely painful to humans, as many unfortunate divers have discovered.
An extensive analysis of the spines revealed they can both sense and secrete a wide range of chemicals, not just defensive toxins.
The researchers found that the chemicals, known as peptides – short chains of amino acids involved in messaging between cells and between organisms – enable the starfish to communicate with one another.
The team then created synthetic versions of the peptides, which they found consistently attracted CoTS in the laboratory.
Combatting CoTS outbreaks is not an easy task. Even in numbers, they are difficult to spot, and their spines are venomous and extremely painful to humans.
They are also not easy to kill, and can easily regenerate dismembered limbs – cutting a crown-of-thorns in half can create two new starfish.
Current methods used to cull CoTS outbreaks usually involve manually removing them from the reef, or injecting the starfish with chemicals such as sodium bisulfate and household vinegar to avoid damaging the reef.
The Australian Institute of Marine Science (AIMS), which monitors the health of the Great Barrier Reef, says that these methods have been successful, but are labour-intensive and costly.
UniSC Professor Scott Cummins said the study pointed toward a potential ‘lure-inspired’ technology to collectively remove groups of CoTS
‘Using synthetic attractants to draw starfish to a single location could support the simultaneous removal of many in one efficient sweep,’ he said.
‘Further development of these synthetic peptides holds real potential for a targeted and environmentally safe control strategy.’
Further testing in behavioural trials was conducted at the Australian Institute of Marine Science’s National Sea Simulator.
AIMS scientist Dr. Cherie Motti said the synthetic peptides, which have been confirmed as non-toxic, consistently altered the movement patterns of the starfish, even at low concentrations.
‘We saw the starfish responded in predictable and measurable ways,’ said Motti.
‘The approach has only been tested in the laboratory, but it shows real promise and demonstrates the value of innovative thinking and research in addressing this decades-old problem.’
This article has been edited from an original AIMS press release. The complete study, ‘A family of crown-of-thorns starfish spine-secreted proteins modify adult conspecific behaviour’ by Richard J Harris, et al, is published under an open access license in Science Direct.
