Scientific discovery on crown-of-thorns starfish communication could alleviate coral damage

April 6, 2017 Ryukyu Shimpo

Recently the Okinawa Institute of Science and Technology (OIST) Graduate University and an Australian research team sequenced the genomes of crown-of-thorns starfish (COTS) that live in Okinawa and the Great Barrier Reef, Australia. The researchers also found that COTS release a water-borne chemical substance into the ocean that attracts more COTS to aggregate. Since COTS feed on coral, a large population outbreak in Okinawa has caused a rise in the severity of coral damage. Although the COTS population is not currently being checked, using their chemical attractant could lead to development of an effective biocontrol measure.

This is the first time that COTS genomes have been sequenced, and the results were published on April 5 in the English-language scientific journal Nature.

COTS aggregate in one location during spawning season. By sequencing COTS genomes, these researchers identified specific proteins in the chemical attractant. In an experiment using water tanks, ocean water in which COTS were bred was taken and inserted into a tank of other COTS. The receiving COTS displayed the reaction of moving toward the inserted ocean water. This reaction indicates a possibility that COTS may release and receive starfish-specific proteins as a means of communication.

This research on the genomes of COTS from Okinawa and the Great Barrier Reef found that these two groups of COTS share 98.8 percent nucleotide identity. OIST Professor Noriyuki Sato, who was involved in the research, called these results “astonishing.” Professor Sato seemed to think it is quite unlikely that the COTS in Okinawa and the Great Barrier Reef, which are separated by about 5,000 kilometers but closely resemble each other, just gradually shifted their habitats apart over time. As COTS in both areas are of the same species, Sato suggested that it could be due to COTS of one origin in the past that experienced a rapid and extensive mass outbreak.

Currently, biocontrol efforts involve capturing COTS one starfish at a time. Professor Sato says that making COTS amass using their chemical attractant could make it possible to remove many COTS simultaneously in the future.

(English translation by T&CT and Erin Jones)

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