Rare giant sea snail may help save Great Barrier Reef

A rare species of giant marine snails could help protect Australia's iconic Great Barrier Reef by attacking the crown-of-thorns starfish - one of the biggest natural threats to corals at the World Heritage Site, scientists said. The crown-of-thorns starfish is known for its incredible appetite for coral and the damage that it causes on coral reefs.

Mike Hall, Principal Research Scientist at the Australian Institute of Marine Science, explained how the rarity of the giant triton sea snail may be one reason why the crown-of- thorns is now such a threat to the survival of the Great Barrier Reef. Scientists including those from the University of the Sunshine Coast in Australia, are investigating the potential of natural predators of COTS to curb populations.

They are investigating the possibility that giant tritons may play a significant role as a natural control agent for COTS outbreaks. The crown-of-thorns starfish (COTS), Acanthaster planci, is a specialist, feeding only upon the flesh of live corals. This animal has several biological attributes that contribute to its ability to undergo massive population fluctuations through time.

With adults consuming up to 10 square metres of live coral per year, a population outbreak of hundreds of thousands to millions of COTS can deal a significant blow to coral reefs. COTS are a major biological cause of coral loss on the Great Barrier Reef and statistical analyses show that they are second only to the destructive power of tropical cyclones which periodically criss-cross the reef. Surprisingly few predators feed upon the vast coral covered seascapes of the Great Barrier Reef but COTS are an exception.

As corals are fixed in one location, they have no defence against an approaching aggregation of hunting COTS. The giant triton (Charonia tritonis) is one of the world's largest marine snails reaching a length of up to half a metre. Due to the beauty of their shell, the giant triton has long been unsustainably harvested from coral reefs, primarily for sale to shell collectors. While the giant triton was declared a protected species in the 1960s, after a century of heavy fishing pressure, they remain quite rare on the Great Barrier Reef.

They are also known to eat other sea stars and echinoderms such as sea cucumbers. Giant tritons typically only eat one COTS per week so they have little application in feeding down a population of COTS numbering in hundreds of thousands. However, their very presence in the vicinity of COTS disperses aggregations. As aggregations are dispersed, and fertilisation success rates decline, the likelihood of massive recruitment in a spawning season may well be reduced.