Scolymia

Lore & Background

Scolymia corals are believed to date back to the Miocene. Their morphology is diverse, with both interspecific and intraspecific variation in shape; polyps may be concave, convex, or flat depending on species and environmental conditions. Species are generally distinguished based on differences in septa number, thickness, and orientation. Scoly corals range from brown to bright fluorescent greens, reds, and purples. They are commonly found in reef aquariums because of their slow growth, though separation from other corals is necessary due to intense competition. The slow growth rate is not well understood, but researchers have proposed that cyanobacterial mats may inhibit their growth or even cause shrinkage.

Scolymia harness energy mainly through a symbiotic relationship with zooxanthellate, a group of photosynthetic dinoflagellates, and to a lesser degree feed heterotrophically using tentacles to catch plankton at night. All species are located in the Atlantic Ocean along the east coast of the Americas between Florida, through the Caribbean Sea and Gulf of Mexico, and as far south as Brazil. At higher latitudes, Scolymia tends to grow faster than at lower latitudes, likely due to annual mean temperature differences. They are typically found at the base of a reef between 10-80 m deep in turbid, low-light waters, anchoring in soft substrates where sediment accumulates. They have adapted sediment-shifting abilities by growing upward on nearly-vertical surfaces and using a mucus exterior to prevent sedimentation from above, filling an ecological niche where other corals cannot survive.

Reader's Guide

Scolymia corals are notable for their solitary growth form, which distinguishes them from most other Scleractinia. Their ability to thrive in turbid, low-light conditions at the base of reefs, where sediment continuously accumulates, allows them to occupy a niche that other corals cannot. They have adapted to this environment by growing upward on nearly-vertical surfaces and using a mucus exterior to prevent sedimentation. Their slow growth rate, while not fully understood, has made them popular in reef aquariums, though they require separation from other corals due to intense interspecific competition. Some scoly corals exhibit interspecific aggression, with Scolymia lacera known to defeat and kill Scolymia cubensis. Scolymia reproduce sexually through broadcast spawning, and because of their lack of immune-recognition, gametes from the same individual can fertilize each other, resulting in less genetic diversity. When two or more Scolymia cubensis larvae settle near one another, they usually fuse to form one complex coral with distinct genotypes. According to the IUCN Red List, Scolymia cubensis and Scolymia lacera are Critically Endangered, and Scolymia wellsii is Vulnerable. While no specific threats are known, corals in general are sensitive to rising temperatures from climate change, causing coral bleaching; Scolymia's relatively deep habitat preference may help protect it from temperature-related damage.

Did You Know?

• Scolymia are solitary corals, unlike most other Scleractinia.
• Their slow growth rate may be inhibited by cyanobacterial mats.
• Scolymia cubensis and Scolymia lacera are listed as Critically Endangered on the IUCN Red List.
• When two or more Scolymia cubensis larvae settle near each other, they usually fuse into one complex coral.