• HOME
• COURSES
• DIVING
• DIVE SITES
• EQUIPMENT
• INJURIES
• LESSONS
• SEA LIFE

Home › Sea Life Facts › Types of Coral Reefs › Sun Coral Polyps

Interesting Facts about Sun Corals

[Phylum: Cnidaria] [Class: Hexacorallia] [Order: Scleractinia (stony corals)] [Family: Dendrophylliidae]

Unlike most corals, and despite the sun-like appearance of the polyps, Tubastraea are non-photosynthetic - which means they can survive with extremely low levels of sunlight.

This page contains fun facts and information about sun corals (Tubastraea), including where they thrive best, what they eat, and how these orange cup-shaped sunflower polyps reproduce.

Sun Coral Habitats and Geographical Range

Sun polyps are azooxanthellate corals that are native in certain marine environments of the Indo-Pacific regions, but especially:

• Australia (e.g. Fiji, the Great Barrier Reef)
• Indonesia (e.g. Komodo, Raja Ampat)
• Japan (e.g. Izu Peninsula, Kerama Islands)
• The Red Sea (e.g. Hurghada, Sharm El Sheikh)
• The Philippines (Apo Reef, Tubbataha Reef)

Despite their soft luminous appearance, they are scleractinian corals.

Unlike most of the hard stony coral species, the non-reef building Tubastraea genus can survive in some extreme conditions.

For example, they live in shallow ecosystems as well as some deep water environments, from only a few metres or down to depths approaching 60 metres (200 feet) if the water is turbid (strong currents).

Here's the thing:

The typical habitats for sun corals include warm and cold water locations. As a result, it is common to see them colonising subterranean overhangs, dark caves, and deep artificial reef structures (e.g. oil rigs, piers, and sunken shipwrecks).

Interesting Fact: Excluding Antarctica, the introduction of some sun corals (e.g. Tubastraea coccinea) into other continents has resulted in them being classed as an "invasive species" - especially Caribbean reefs, the coastline of Brazil, and the Gulf of Mexico.

Sun Coral Appearance and Characteristics

Marine biologists have created some crazy fish names in the past. However, this type of stony coral (Scleractinia) gets its common name from a resemblance to the bright rays of light projected by the sun.

By and large, the base of sun polyps are orange and the body colouration is usually a blend of bright orange and "semi transparent" yellow tentacles (excluding the black sun coral which tends to be dark green).

This part is important:

They are colonial corals that house multiple polyps from a shared tissue base. Often, these polyps will be closed - especially during the daylight hours - but they will open up when they need to capture food.

Sun Coral Size

The general size of a sun coral is around thirteen (13) centimetres in diameter (5 inches) and between three (3) and eight (8) millimetres high (1 to 3 inches).

It may not have the fastest growth rate, like bubble coral. But, sun coral can grow about three (3) centimetres per year as it starts to form a large community.

What Do Sun Corals Eat?

Unlike bubble corals (Plerogyra sinuosa), most of the sun coral species can actually ingest small fishes up to one (1) centimetre long, such as silversides (Atherinopsidae).

In the wild, being typical nocturnal carnivores means the daily diet of the Tubastrae orange sun coral will include:

• Detritus (suspended organic matter sometimes known as "marine snow")
• Invertebrates (e.g. aquatic crustaceans)
• Krill
• Mysis shrimp
• Phytoplankton
• Zooplankton (e.g. copepods, rotifers)

Thus, sun corals are heterotrophic organisms and are able to absorb dissolved organic material and small particles from the water column to meet their nutritional requirements.

Pro Tip: In aquarium settings, sun corals kept in captivity will require frequent meals of at least three (3) times per week. You can target-feed them with different types of fish food like brine shrimp, cyclops, and liquid coral foods.

Sun Coral Species List

Sun Coral Reproduction

Like the vast majority of coral formations, Tubastraea are hermaphrodites, meaning each individual has male and female reproductive organs. In other words, sun corals can reproduce asexually.

After reaching the reproductive age at eighteen months, they can multiply in several different ways. The parent colony is able to produce a new polyp bud, breaking away to form a new colony - usually close by and within one (1) metre of the parental organism.

But wait - there's more:

In addition, they can also release free-swimming larvae (called planulae) into the water column. The polyps will find a suitable base to settle and "cement" itself to a solid structure to start developing new colonies.

It's also quite common for some colonies to create runners - a tissue without polyps that can grow up to ten (10) centimetres per year.

The runners extend themselves away from the colony until they reach a suitable and unoccupied place to evolve.

In marine biology words, it's fair to say this form of reproduction fails to meet the true definition. Even so, polyps that "escape" the existing colony are able to populate by settling down in a different location.

Threats and Predators

Its striking appearance means orange sun coral is a popular choice among marine aquarium enthusiasts. Even so, it requires a lot of care, limited lighting, stable water conditions, and a healthy supply of marine protein.

Sun corals are also susceptible to the destruction caused by algae on reef formations. Even so, because Tubastaea tends to thrive in dark areas, sun coral has limited impact from algal growth.

Outside of a captive environment, some of the natural predators of sun corals are butterflyfishes, parrotfishes, sea snails, and sea stars (especially the crown-of-thorns starfish).

Fun Fact: The IUCN Red List of Threatened Species is yet to assess the conservation status of sun coral. However, research shows that sun corals are displacing some native marine life, such as sea sponges and some other native coralline species.

Divers also enjoyed reading about...