To Combat Coral-Eating Pest, UA Researcher Helps Find What They Smell

From the June 2017 Desktop News | A University of Alabama researcher is part of a team that identified genes used to communicate by a starfish that preys upon coral reefs, a promising discovery that could lead to efforts to repel the aquatic pest from sensitive reefs.

Aggregation of crown-of-thorns starfish on the back of Keeper Reef.

Aggregation of crown-of-thorns starfish on the back of Keeper Reef.

The findings, published in the journal Nature, are the first insight into what chemicals attract and repel the crown-of-thorns starfish and suggest a method of mitigating other marine nuisances.

“This sea star is an absolutely huge problem, and it’s become clear that traditional tools are never going to keep up with it,” said Dr. Kevin M. Kocot, an assistant professor of biological sciences and co-author on the paper. “Other, more clever approaches are needed to control it on a species-wide basis.”

Normally a part of a healthy coral ecosystem, the crown-of-thorns starfish has become abundant, possibly because warmer, more nutrient-rich water allows more larval starfish to survive into adulthood and because of overfishing of its main predator, a sea snail called the giant triton.

An average adult starfish roughly 16 inches across can kill about 75 square inches of live coral daily, and an outbreak of the starfish can mean thousands grazing across a coral reef. Humans have tried several ways of relieving coral during an outbreak, including removing the starfish by hand, killing them with chemical injections, and even a robot that continuously hunts them.

However, researchers at the University of Queensland and the University of the Sunshine Coast in Australia, along with collaborators at the Okinawa Institute of Science and Technology in Japan, hope to use the starfish’s own communication to keep them off coral reefs.

The crown-of-thorns starfish does not see well, but certain chemicals it releases attracts larvae to settle near adults, resulting in huge aggregations. The researchers focused on these chemicals, which make the normally sedentary starfish highly active.

Kocot, whose main research interests are bioinformatics and genomics of invertebrates, analyzed the genomes of two individuals of the crown-of-thorns starfish, one from the Great Barrier Reef, Australia, and another from Okinawa, Japan.

He focused on the genes that underlie the sea star’s sense of smell, in the hope that he and his team will be able to produce a bait that attracts sea stars away from coral reefs. The group also studied a smell produced by the predatory snail that eats the sea star because an artificial smell based on the snail could be used to scare the sea stars away from coral reefs.

More research is needed, including experimental work in aquariums, before large-scale methods can be attempted in the ocean, but Kocot said researchers are optimistic after sequencing the starfish’s genes that manipulating communication could save coral reefs from further overpopulation of this predator.