Comparative genomic analysis reveals spine formation and coral prostaglandin tolerance in crown-of-thorns starfish.

Recurring outbreaks of crown-of-thorns starfish (COTS) are one of the greatest threats to corals and have caused catastrophic damage to coral reef ecosystems in recent decades. As obligate corallivores, COTS can tolerate toxic coral mucus, and the sharp spines covering their bodies provide protection from predators. While both of these characteristics are known to contribute to the vitality of COTS and aggravate the impact of COTS outbreaks, the genetic mechanisms underlying their adaptation remain unclear. In this study, we generated a chromosome-level COTS genome and suggested the importance of chromosome fusion in coral-feeding adaptation. In addition, high expression levels of EP4 receptors in the COTS spine apex indicated their potential ability to use the coral prostaglandin PGE2, which might further activate the skeletogenic gene regulatory network responsible for the growth of the spine and body plan of COTS. A comparison of the historical population sizes of COTS from different locations revealed a unique trend in the Coral Triangle, suggesting a potentially higher risk of outbreaks in this region. Our results provide a molecular basis for the adaptive evolution of COTS and a better understanding of its interactions in coral reef ecosystems.