Starfish Code Cracked: Key to Saving Coral Reefs

The Crown-of-Thorns Starfish (Acanthaster; CoTS) is native to reefs of the Indo-Pacific and plays a key role in maintaining ecosystem health. A single CoTS can consume up to 240 cm² of coral tissue per day, roughly 10 m² per year. On its own, this may not seem catastrophic. But during outbreaks, swarms counting thousands of starfish can strip hectares of coral tissue in just a few months. This overconsumption doesn't just degrade reef health and stability by depleting hard-bodied, reef-building corals. It also damages long-term resilience, preventing reefs from adapting to their greatest threat: climate change.

Currently, the main method of combatting CoTS outbreaks is by manually culling each starfish one-by-one, which is highly inefficient, labor-intensive, and costly. But now, a team of researchers from the Australian Institute of Marine Science (AIMS), the University of the Sunshine Coast in Australia, and the Okinawa Institute of Science and Technology (OIST) in Japan have discovered that CoTS use their characteristic spines to 'smell' peptides and communicate with one another, even outside mating seasons. Building on this finding, the team has created a synthetic peptide that consistently attracts CoTS at very low concentrations and with no toxicity. The results are published in iScience. Their discovery could lead to the further development of potent pest-management peptides - dubbed Acanthaster attractins - that prompts the starfish to congregate at one spot, enabling the efficient removal of many CoTS in one sweep.

"Through genomic and proteomic analysis, we found that the CoTS spines are used to both sense and secrete a wide range of peptides - not just defensive toxins," explains Professor Noriyuki Satoh, head of the Marine Genomics Unit at OIST. "These may promote swarming, and so we synthesized the peptides that we suspected function like pheromones for communication and found that they consistently affect the trajectories of the starfish. With these attractins, we hope to contribute to the development of an efficient and safe measure against CoTS outbreaks."

The main findings from experiments with the synthetic peptide mixture (SPM). A) shows a toxicity assay in which brine shrimp (Artemia salinia) are subjected to various concentrations of the SPM, showing a very high survival rate. The dips in survival rate at the end of the experiment are most likely caused by natural factors.B) shows cumulative heatmaps with the location of the CoTS in two separate flume assay tanks (left and right). Each tank contains two parallel, non-mixing water flows maintained under highly controlled conditions, with no turbulence or blending between the streams inside the tank. One flow - the "cue arm" - contains a steady concentration of the SPM, added to the flow at the white dot. CoTS were released at the boundary between the two flows in the tank, with warmer colors indicating areas where the starfish spend more time during the experiments.C) and D) indicate the duration spent in each 'arm' of the tanks and the amount of meandering (a type of foraging or searching movement by the CoTS to infer the source of a chemical cue) respectively.

Harris et al., 2025

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