A boulder coral with large separated corallites that stand out from the surface. The polyps are often out by day as well as at night, which is unusual.
Massive boulders and domes over 1.5 m across, flattening into plates in deeper water. The cups are large — roughly thumb-sized, widely spaced and strongly raised — which gives the colony a cratered look and makes it the most obviously star-textured of the Caribbean boulder corals. You can pick out individual polyps from a metre away, which you cannot on its relatives. Brown, grey-green or reddish.
That cup size and spacing is the separator from the other Caribbean boulder corals, whose cups are much smaller and closer together.
Its polyps are withdrawn by day and fully extended at night, when the colony looks completely different: furry rather than pitted. Some colonies fluoresce red or orange in daylight, which is put down to symbiotic cyanobacteria living alongside the algae. It occurs throughout the reef, is most abundant between about 12 and 30 m, and reaches about 90 m, which is why it is a focus of research into deep refuges.
It is one of the more robust framework corals left in the Caribbean. It is intermediately susceptible to stony coral tissue loss disease, showing symptoms about a month after the worst-affected species and then developing new lesions over years, and it is the main target of the antibiotic treatments applied to corals in Florida.
It is now the only species left in its genus, the rest having moved out in 2012.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
