Scleractinian corals, also known as stony corals -- or just hard corals -- are the primary reef builders in the oceans. Their polyps secrete calcium carbonate to form a skeleton. A minority of species live as single polyps, but most stony coral species are colonial, and the structures they build 'grow' over time. They form a myriad of shapes: mounds, branches, fingers, plates, and encrustations.
In several previous posts I discussed and displayed photos of a number of so-called soft corals, all of which are octocorals, i.e., their polyps have eight tentacles. Stony corals are…
Caribbean Sea
Sea fans are among the most beautiful sights seen by divers. Gorgonian sea fans are Cnidarians that build colonies in branching formations that usually are fan-shaped, thus the common name.
Like the Nephtheid soft corals I wrote about recently here on Photo Synthesis, Gorgonians are octocorals: each polyp has eight pinnate tentacles which it uses to capture nutrients suspended in the water column. They are seen most often on reef crests, or jutting out from drop-offs or steep banks in locations where natural currents will sweep plankton and other organic nutrients across the polyps'…