The open brain coral, or Trachyphyllia geoffroyi, is a vibrant coral species that are found mainly in the Indo-Pacific oceanic area. With a ferocious appetite and a symbiotic relationship with organisms around it, the open brain coral plays a big role in its ecosystem.


The open brain coral expresses its appearance through its name, as it does look like a human brain at times. They can come in a variety of colors and color combinations. For example, some are green and blue, while others can be a solid color. This varies from colony to colony.

Diameters of up to 20cm seem to be the limit of the coral’s size. They have large fleshy polyps, and large fleshy mantles and generally have valleys with walls on the outside. These walls tend to have a ridging look to them. They can vary from being open to being more folded. They are sometimes referred to as folded brain corals.

Remarkably, although they are relatively small creatures, they can have up to 3 mouths, and their teeth line the inside of their outside walls.

This green open brain coral is an example of the color variation within the species
This green open brain coral is an example of the color variation within the species


The open-brain coral has many ways to obtain its food. Over time they have used various strategies, and their diet includes a wide variety of foods. They are mostly passive feeders and allow plankton and other food particles, using the water flow, to float within range, and they absorb them. They also live in harmony with marine algae, or zooxanthellae, and use them to supply nutrients and energy. Other foods they eat include rotifers, Cyclopeeze, mysis, and fortified brine shrimp. They can eat larger foods but tend to process smaller foods far easier.

Despite their passive nature, they are considered voracious eaters and need a consistent food source; otherwise, they will lose a lot of their body mass.


Open brain corals can live in their habitat with others or as an individual. They are free-living creatures and tend to be found around other free-living organisms. Despite their namesake, open-brain corals are actually found primarily in lagoons, reef slopes, and around islands, rather than being directly in coral reefs.

These unique specimens mostly inhabit the Indo-Pacific oceans. They have been seen as far as the Red Sea near Egypt, all the way to New Caledonia. The Western Central Pacific and the seas around Australia are known to inhabit many of them. The Great Barrier Reef is a high-population area. They tend not to favor extreme water depths, with their limit sitting around 40 meters.

They are very sensitive creatures, and they thrive in lower moderate light areas with gentle water movement. Due to their soft tissue, they can not be surrounded by sharp objects, like rocks, or be at a significant height.

Open Brain Coral
Open brain coral comes in all shapes and sizes, not following one structure


Open brain coral is an incredible creature when it comes to reproduction. They are hermaphrodites and can reproduce both sexually and asexually. They contain the sexual capabilities of both genders. Sexual reproduction occurs when the coral releases eggs and sperm at the same time. This allows for fertilization. The fertilized planula larva then becomes a plankter, which is followed by the polyp stage of the cycle. The polyp will excrete calcium carbonate and gradually turn into a fully formed coral.


It is clear, due to their IUCN listing, that this unique-looking species is under threat. The open brain coral is classed as ‘near threatened’, and this mainly comes down to human intervention through habitat loss and coral farming for the aquarium trade.

Amazingly, 60,000 open brain corals were taken from the seas for the Indonesian market in 2005. Acts like this are highly unsustainable and are seriously harming the future outlook of these wonderful creatures.

Facts about Open Brain Coral

  • They are hermaphroditic, meaning they have the sexual capabilities of both sexes.
  • They require daily feeding as they have a big appetite.
  • They are under threat due to harvesting and being put in captivity.


How big do open brain corals get?

In general, they are relatively small corals. The maximum size is around 20 cm in diameter.

What is the lifespan of open brain coral?

As the open brain coral does not contain a brain, its biological limitations are very different from many animals. Living in the right conditions, the open brain coral can live for up to 900 years.

Are open brain corals endangered?

Open brain corals are listed on the IUCN list as ‘near-threatened’. This is largely due to human activity, such as over-fishing and habitat loss. Pollution and plastics also impact their habitat.

Where are Trachyphyllia geoffroyi found?

Trachyphyllia geoffroyi, or open brain coral, are mainly found in the Indo-Pacific areas. They range from the Red Sea to the Philippines, and all the way to Australia.

About Ocean Info

At Ocean Info, we dive deep into ocean-related topics such as sealife, exploration of the sea, rivers, areas of geographical importance, sailing, and more.

We achieve this by having the best team create content - this ranges from marine experts, trained scuba divers, marine-related enthusiasts, and more.

Sea Anemone with Clownfish

Dive into more, the ocean is more than just a surface view

Bottlenose dolphins are known to help stranded humans back to the shore

8 of the Most Intelligent Marine Animals

From dolphins' awe-inspiring communication skills to orcas' social complexity, the ocean is home to some of the most intelligent marine animals.

Share to...