The Open Brain Coral (Trachyphyllia geoffroyi) is a free-living coral species that is found mainly in the Indo-Pacific oceanic area. They are aptly named for their resemblance to a human brain, showcasing deep grooves mirroring the brain’s intricate folds.
Appearance
These hard corals come in a variety of colors, most commonly vibrant mixes of green and red. They can also be found in shades and combinations of brown, pink, and even blue, making them a visually stunning addition to any reef.
The coral’s skeleton typically forms a cone-shaped base, often developing into a figure-eight shape as it grows. However, their forms can vary considerably, ranging from perfectly round to elongated and even taking on clover-leaf or convoluted shapes with multiple lobes.
Open Brain Corals can exist as solitary individuals or form colonies. While they are small corals, rarely exceeding 20 cm in diameter, colonial formations can house multiple large polyps within their valley regions, contributing to the coral’s remarkable diversity in appearance.
During the day, a fleshy mantle extends beyond the coral’s skeleton, concealing its distinct valley regions and walls. These valleys, separated by walls with a characteristic ridged appearance, can vary in complexity, ranging from simple hourglass shapes to highly lobed structures.
Habitat
Open Brain Corals, known for their free-living nature, are typically found in the company of other unattached coral species. They can be found as solitary individuals or, in rare instances, form extensive colonies in specific protected, shallow island embayments.
While their name might suggest a preference for coral reefs, these unique stony corals primarily inhabit lagoons, reef slopes, and areas surrounding islands within the Indo-Pacific region, spanning from the Red Sea to New Caledonia.
These large polyp corals thrive on soft substrates, favoring sandy or muddy areas on sheltered reef slopes and lagoons.
The waters around Australia, particularly the Great Barrier Reef, are known to support significant populations of these corals. They prefer shallower depths and rarely venture beyond 40 meters.
They are very sensitive creatures, and they thrive in low light conditions 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, or be exposed to high light conditions.
Diet
Open Brain Corals primarily rely on photosynthesis for sustenance. They harbor symbiotic dinoflagellates called zooxanthellae within their tissues, which produce essential nutrients through photosynthesis.
These corals also supplement their diet by filter-feeding on small zooplankton and other prey from the water column, providing additional energy for themselves and vital nutrients for their symbiotic partners.
While they are passive feeders, Open Brain Corals are voracious eaters and require a consistent food source to maintain their health and vibrant appearance.
In reef tank settings, they eat a wide variety of foods including rotifers, mysis shrimp, and fortified brine shrimp. They can eat larger foods but tend to process smaller foods far easier.
Reproduction
Open Brain corals are hermaphrodites and can reproduce both sexually and asexually. They reproduce sexually by releasing both eggs and sperm into their body cavity (coelenteron), where fertilization takes place. The resulting zygote develops into a planktonic planula larva, which eventually settles and undergoes metamorphosis.
During this transformation, the larva develops tentacles, septa, and a pharynx before attaching itself to a substrate with its aboral end. As the polyp matures, it begins to excrete calcium carbonate, gradually forming the intricate skeleton that characterizes a fully developed coral.
Threats
Threats arise primarily due to human activities. This species is heavily targeted for the aquarium trade, with Indonesia being the largest exporter, shipping tens of thousands of live corals annually. This unsustainable practice, combined with habitat loss, poses a severe risk to the future of these fascinating creatures.
Furthermore, Open Brain Corals, like other coral species, are vulnerable to the broader impacts of global climate change. Rising ocean temperatures lead to coral bleaching and increased susceptibility to diseases, while the escalating frequency and intensity of storms and ocean acidification further exacerbate their plight. These combined stressors, along with localized threats such as pollution and destructive fishing practices, jeopardize the survival of Open Brain Corals.
Quick Facts about Open Brain Coral
- Open Brain Corals are hermaphrodites, possessing both male and female reproductive organs.
- They host a species of Gall Crab called Lithoscaptus semperi.
- Indonesia is the largest exporter of open Brain Corals for the aquarium trade.
- The round, flat-bottomed coral once known as Wellsophyllia radiata is a unique morphotype of the Open Brain Coral.
- They can move by inflating their tissues and using water currents.
FAQs
What are the threats to Open Brain Coral?
They are listed on the IUCN Red List as ‘Near Threatened’. This is largely due to human activity, such as over-harvesting, habitat degradation, and climate change impacts.
Can Open Brain Corals move?
Open Brain Corals, like other Brain Corals, can move. They are free-living corals, meaning they aren’t attached to the seafloor. By inflating their tissues, they can use water currents to reposition themselves if their environment becomes unsuitable.
What kills Brain Corals?
Diseases like black band disease and white plague can cause mass mortalities, leaving behind dead corals that are colorless and often covered in algae. Rising ocean temperatures trigger thermal bleaching, where corals expel their symbiotic algae, turning white and eventually dying.
