Sesquiterpenes
The chemistry that keeps soft corals from being eaten and stops competitors settling next to them - and a standing source of drug leads.
Soft corals have no stony skeleton to hide behind and no serious sting, and they are nonetheless left largely alone by animals that eat everything else on the reef. The reason is chemistry. Their tissues are loaded with terpenoids - sesquiterpenes and their relatives - which are bitter, deter feeding and inhibit competitors trying to settle nearby.
It is chemical warfare over space as much as over predators. A soft coral leaks compounds that stop stony coral larvae from settling within reach and slow the growth of what is already there, which is one reason soft corals hold their ground on a crowded reef.
These molecules are of standing interest to drug research - anti-inflammatory and antitumor activity keeps turning up in them, and new ones are still being described from common species, such as the compound isolated from the Broccoli Coral of this sea in 2018.
