Boulder brain coral
Colpophyllia natans
(Houttuyn, 1772)
Description:
Generally, the colonies form large rounded domes of up to 2 m in diameter, but also large rounded plates can be formed. The surface is covered with a curved system of ridges and valleys. The ridge tops have a thin, but distinct groove and a second line is located halfway down the ridge, where the slope decreases in angle and slants to form the valley. The costae between adjacent corallites are discontinuous, and all costae are equal in thickness. The valleys are long, wide and meandering, containing several polyps. Polyps are extended only at night, their tentacles forming long meandering rows along the ridges.
Color:
Typically the ridges are brown and the valleys green, tan or whitish.
Corallites:
The septa are equal in thickness, and there are less than 12 septa per cm. The columella is discontinuous and thin, less than a quarter of the valley width.
Habitat:
Inhabit reef tops and reef slopes, down to 50 meters.
Distribution:
Common in Florida, Bahamas and Caribbean.
Remarks:
In the related Closed-valley brain coral (Colpophyllia breviserialis ), the valleys are closed and hold only one or two polyps.