Caribbean Coral Identification: Brain Coral

Chances are the first time you went scuba diving or snorkeling you saw a brain coral. They grow in large mounds that can be several feet across and strongly resemble the human organ for which they’re named. You’ll find these corals in the shallowest parts of the reef, down to 100 feet (30 m).

There are four types of this distinctive coral in the Caribbean. The boulder brain coral is the largest and most common, and an important reef-building species. To identify the four different types you must look closely at the size of the ridges and valleys. If you’re new to coral identification, check out our post about coral-biology basics to learn about ridges, valleys and, other important terms.

Boulder brain coral

The ridges of Colpophyllia have fine lines running from the peak of the ridge to the center of the valley.

Colpophyllia forms large boulders and is an important reef-building species

Colpophyllia natans can grow to a truly enormous size, forming large domes, boulders, and thick encrusting plates. The common name for this coral is the boulder brain coral because of its size. As the coral dies and the tissue recedes, the skeleton remains behind, adding rocky structure to the reef. This makes the boulder brain coral one of the most important reef-building species.

Colpophyllia has short ridges that twist and turn their way across the surface of the coral, making it look like a brain. The fine grooves running from the top of each ridge down toward the center of the valleys into the corallites make this species unique. If you spot a brain coral with these thin markings on the ridges, you’ve found a boulder brain coral.

Grooved brain coral 

From left to right: Pseudodiploria clivosa; Pseudodiploria strigosa; Diploria labyrinthiformis. To tell these corals apart take note of the ridge size and texture of the coral surface.

Grooved brain corals can have narrow or wide ridges depending on the colony. Ridges will always have a groove in the center.

Grooved brain corals

Diploria labyrinthiformis is the most recognizable brain-coral species. This coral has wide ridges with a central groove. Valleys between ridges are deep and vary in width. It’s also one of the most photogenic, as you can find a wide diversity of ridge thicknesses and intricate folding patterns.

Grooved brain coral ridges can be wide with shallow grooves and rounded edges or the ridge edges can come to a slight peak with deep grooves. This all depends on the colony, which is what makes looking for this coral like an underwater treasure hunt. 

Symmetrical brain coral 

Pseudodiploria strigosa has a smooth surface texture and symmetrical ridges.

Pseudodiploria strigosa is a common sight for snorkelers and scuba divers in the Caribbean. This coral grows into round, brain-like colonies and lives everywhere from the shallowest part of a reef down to 100 feet (30 m).

There are two species of Pseudodiploria, and to tell them apart you must look at the surface texture of the colony. P. strigosa has a smooth surface compared to the rough or knobby texture of P. clivosa (knobby brain coral). You can also tell them apart by looking at the spacing between the ridges. P. strigosa has taller narrow ridges, while P. clivosa has short ridges.

Knobby brain coral 

Sometimes you need to look past the ridge sizes and see the surface texture of a coral. The knobby brain coral has short knobs projecting from the coral’s surface.

Pseudodiploria clivosa is the final Caribbean brain coral species. If you’re looking for this coral in an older guidebook, it’s classified under Diploria. Scientists reclassified both knobby brain coral and symmetrical brain coral as Pseudodiploria, as they share small, narrow ridges.

Diploria clivosa can grow into large, encrusting mounds that appear to be melting onto the rocks. Knobby horns and bumps, characteristic of cactus coral, cover the mounds. This species of coral is most common in shallow water.