Sun corals, also known as Tubastraea coccinea, belong to a genus of corals known as large-polyp stony corals. These stony corals produce a hard skeleton; they do not create reefs. Most corals contain the symbiotic algae zooxanthellae, which is used for photosynthesis to turn sunlight into food. These corals are different in that they catch all their food using long tentacles, extending their tentacles at night to feed, not by using sunlight. This specialized carnivorous feeding system makes Sun Corals heterotrophic, feeding mainly on zooplankton.
This species is known by many names, including Orange Sun Coral, Sun Polyp Coral, Sunflower Coral, Orange Cup Coral, and more.
Sun Corals have an orange body with orange and yellow transparent tentacles. These corals live in colonies with multiple polyps or individual bodies. The mass of growing corals maintains connection by a shared tissue base. This is a large-polyp stony coral, creating its own calcium carbonate skeleton. This skeleton is covered in corallites which are skeletal cups formed by the individual stony coral. The polyp sits in and can retract into the corallite.
Colonies of Sun Coral grow to about five to six inches in diameter. These colonies grow by spreading out at a rate of one inch per year, forming larger communities. Individual polyps are about one inch in diameter and range from one to three inches in height.
Most coral species house a symbiotic algae called zooxanthellae. This algae is how those corals use photosynthesis to turn sunlight into food. These corals do not contain zooxanthellae, so they must catch all of their food using long tentacles. These corals eat zooplankton, generally extending their tentacles at night to feed.
The Sun Coral was first documented on the reefs of Curaçao and Puerto Rico in 1943. Since then, they have become known as an invasive species in many areas. It is commonly found in Caribbean reefs and is native to the Indo-Pacific, and they have been introduced to every continent, except Antarctica. This is due to their unique ability to live and thrive without sunlight in many different habitats.
Sun Corals are highly adaptive and can be found in waters that are sunny and shallow, displacing other native reef species, to depths of over 200 feet and colonizing many different surfaces in the darkness, such as metal, artificial structures, caves, overhangs, and shipwrecks.
This coral was first introduced to the Gulf of Mexico in 1945. By the 1980’s the species had spread throughout the Caribbean and western Atlantic oceans. Because of their ability to survive on foreign surfaces, their invasive behavior has been highly correlated with the oil and gas industry. The stony coral attaches itself on oil platforms which are then transported between the Indo-Pacific and the Gulf of Mexico.
Since Sun Corals do not photosynthesize for food, they have to catch all their food using long tentacles. They are known to extend their tentacles at night to consume zooplankton. Zooplankton consists of small animals and immature stages of larger animals, and other particles that are unable to swim against currents. Because of this unique filter-feeding system, these corals need to live in areas with strong currents and water flow.
Upon reaching sexual maturity at about 1.5 years old, the Sun Coral has three ways it can reproduce. Firstly, each colony is capable of creating a polyp bud or ball. These buds will eventually break away to form their own separate colony. Secondly, this species is capable of hermaphroditic reproduction by delivering larvae of both sexes into the water column. These will settle elsewhere, as polyps, forming their own colonies. Thirdly, this coral is able to release a thin tissue with no polyps, called a runner. These runners grow up to 4 inches per year, sometimes growing for years, until they reach an open area to start growing polyps and forming a colony.
The Sun Coral Project of Brazil
In Brazil, the first documented record of the Sun Coral arriving as an invasive species was in the 1980s and arriving on an oil platform. Since then their adaptations to survive on multi-surfaces, at varying depths and their ability to reproduce early have allowed the corals to become widespread along the Brazilian coast. In 2006, the Sun Coral Project began to assess the threats to local diversity among the reefs and the ocean floor. The project aims to monitor the spread of the coral and it’s impact on native species, provide education about invasive species and their threats, and provide the management of coral populations by removing colonies.
Keeping Sun Corals in Aquariums
The Sun Coral is a popular species for aquarium keepers due to their stunning displays of color and their lack of need for special lighting. Their special feeding style requires that the corals be fed often and by hand. They appear to do best when mimicking their natural environment, such as reef ledges and next to power heads for water flow, when placing them in the tank. Keepers will need to hand feed their corals with items such as brine shrimp, very small fish, copepods, mysis shrimp, and small pieces of clam and scallops.
What eats Sun Coral?
Specific snails and nudibranch species are known to predate many coral species, including the Sun Coral.
Do Sun Corals sting?
Sun Corals have a large number of nematocysts, stinging cells, lining their tentacles, though they are rarely aggressive.
Do Sun Corals need sunlight?
No, Sun Corals do not contain the algae zooxanthellae, which is what the specimen would use to photosynthesize food. Instead, they catch their food with their tentacles.
Are Sun Corals easy to care for?
Sun Corals are relatively east to care for in captivity as long as you keep them near a water current and hand feed each polyp often.
How fast do Sun Corals grow?
Sun Coral colonies reach about six inches in diameter and grow just over one inch per year. The height of individual polyps can reach from one to over three inches.