Brain coral is a type of stony coral which is named after its unusual appearance. As brain coral grows, it develops a rounded surface covered in deep meandering ridges and grooves, causing it to look eerily like a brain. This coral can be found in warm, shallow waters in many parts of the world, most notably in Australia's Great Barrier Reef. Like many other species of coral, brain coral is in danger due to changes in the marine environment, many of which have been brought about by human activity.
Like other corals, brain coral is not a single organism. Instead, it is a colony of individuals known as polyps. The polyps band together and slowly build a calcium carbonate skeleton. Each species builds a slightly different style of skeleton, which explains why corals are so physically diverse, and in fact several species including polyps in the Meandrina and Diploria genera build brain-like skeletons. Brain coral's hard layers of calcium carbonate explain why it is known as a “stony” coral.
This coral is a major player when it comes to reef building. Brain coral develops extremely slowly, sinking resources into developing a very strong skeleton and base. This means that the coral is difficult to dislodge, so it will endure turbulence, hurricanes, and other threats. Once brain coral establishes itself, it can provide shelter for other corals and organisms, contributing over time to the development of a true coral reef.
Most brain corals reproduce by “broadcasting” sperm and ova. The polyps in the coral simply release their sperm and ova into the water, counting on currents to bring reproductive material close enough to create a gamete, which then drifts through the ocean until it finds a spot to settle and start a new brain coral colony.
The polyps in brain coral have a number of food sources. They can feed on the algae which exist symbiotically with them, growing inside the sheltering grooves of the coral, and they can also use sweeper tentacles to trap passing free-floating organisms. When threatened, the polyps retract their tentacles into the grooves of the coral so that they cannot be eaten by predators or destroyed by turbulent waters. The organisms also use their tentacles to clean house now and then, removing accumulated sand and other materials.
Because this coral takes so long to grow, it should always be appreciated in situ. Harvesting brain coral almost always kills it, unless the harvesting is performed by a trained professional, and the loss of a brain coral can be a blow for a reef. For the same reason, divers should be careful around brain coral and other corals to prevent damage which could kill the coral or inhibit its growth.