Question of the Week: Why is brain coral shaped like a brain?

By Ruth Blackburn

The aptly named brain coral is a dome-shaped member of the family Faviidae which has distinct sinuous valleys (that’s the wibbly ridgey bits that look like the surface of a brain).

So why the dome shape?  This is largely driven by the position of the coral within the reef: brain coral is found in shallow parts of reef at a depth of about 1-15 metres. At this depth there is substantial wave action, which corals with a compact spheroid shape are much more resilient to than those with thin antler-like projections.

Brain coral from the
Grant Museum collection.

The sinuous valleys on the surface of the brain coral can also be explained.  These mark the areas in which polyps – soft bodied marine creatures – are most densely found.  Polyps are able to secrete calcium carbonate (just like the scale that builds up in your kettle) to form a hard and protective exoskeleton that it can live in: this exoskeleton is what you actually see when you visit the Grant Museum.