A yellow-olive sheet spread flat over dead coral, low and unremarkable until you understand what it is doing: taking territory.
This soft coral does not build upward, it creeps sideways over hard substrate, and it wins ground chemically. Its tissue is loaded with terpenoids that kill or repel the animals it touches, so it advances over stony corals, sponges and anything else in its way, and settling larvae of other species do not survive on the surface next to it. On reefs where hard corals have died back it is one of the species that takes the space and keeps it.
Like other soft corals it feeds mainly through symbiotic algae, and the polyps retract flush with the surface, which is why a colony looks like a painted crust rather than an animal.
It reproduces both by spawning and by simply breaking - a detached fragment that lands on suitable rock keeps growing, which is how a single colony becomes a field of them.
- low sulfur-yellow to olive sheet, encrusting rather than branching
- surface finely bumpy with retracted polyps, smooth to the eye from a distance
- spreads over dead coral and rock rather than standing off it
- colonies to 50 cm across
