AsianScientist (Apr. 11, 2017) – Researchers have sequenced the entire genome of the Crown-of-Thorns starfish (Acanthaster planci), a rapidly multiplying predator that has been blamed for the destruction of coral reefs. These findings, published in Nature, help to inform control strategies.
Known in Okinawa as onihitode or “demon starfish,” Crown-of-Thorns starfish (COTS) can be found in colonies of up to several million individuals, devouring reefs completely and becoming a major ecological concern.
To better understand COTS behavior, researchers from Australia and the Okinawa Institute of Science and Technology (OIST) sequenced the COTS genome using two individual specimens: one from the Great Barrier Reef and the other from a reef in Motobu on the western coast of Okinawa.
“Although the samples were taken from individuals found 5,000kms apart, on different sides of the equator, we confirmed they belong to the same species,” said study author Professor Noriyuki Satoh.
However, a genome by itself is like a set of furniture without the instruction manual—you have all the pieces but you do not know what they do individually, how they fit with each other and in which order to assemble them.
To identify the genes that could be used to control the COTS population, the researchers observed COTS behavior during spawning events in the hopes of identifying chemical signals that the starfish use to communicate with each other. To do this, researchers at the University of the Sunshine Coast and the Australian Institute of Marine Science built a Y-shaped aquatic maze, with a starfish starting at the end of the longest branch.
In one experiment, they fed one of shorter branches with water collected from an aggregation of COTS. Because the starfish moved towards this branch of the maze as compared to control water samples, they concluded that those water samples must have contained molecules that induced the starfish to gather with other members of its species.
The same water samples were then analyzed biochemically to identify these molecules, which were then mapped to the COTS genomic data. Because the scientists are now in possession of the full genome, they could confirm that these molecules originated from COTS.
In total, the researchers identified 26 COTS-specific genes that could be involved in secreting 107 water-borne communication signals. Moreover, the genome includes 750 genes coding for proteins akin to the starfish version of smell receptors. These findings are the first step towards understanding how to disrupt communication on a large scale and prevent reef damage by defusing mass spawning events.
“On the one hand, this report provides us with biocontrol targets that we can start testing on COTS today,” said OIST graduate student and study author Mr. Ken Baughman.
“On the other, the high quality genomic data continues to provide fundamental insights for evolutionary developmental biology. Hopefully, this report will bring attention to both areas of research.”
The article can be found at: Hall et al. (2017) The Crown-of-Thorns Starfish Genome as a Guide for Biocontrol of this Coral Reef Pest.
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