Open Brain Coral
(Trachyphyllia geoffroyi)
NT
Overview
Trachyphyllia geoffroyi can be found as a free-living polyp or colony. The raised, twisted lines and wide, deep grooves of the colony give this coral its common name ‘open brain coral.’ The smaller polyps have an hour-glass shaped appearance and the mantle, which looks like an air filled bubble, protrudes from the centre. This species has an extensive distribution across east Africa, Asia and Australia but is very rarely found. A monospecific species, the fossil records of this species date back to the Eocene period. T. geoffroyi is heavily harvested for the aquarium trade and is also at threat from coral bleaching, ocean acidification, over-fishing, sedimentation and pollution.
Urgent Conservation Actions
More research into the population of this species is required as is expansion of the global network of marine protected areas and effective management.
Distribution
Red Sea, Indian Ocean and Pacific Ocean.

 
Media from ARKive
ARKive image - Open brain coral
ARKive image - Open brain coral
Evolutionary Distinctiveness
Order: Scleractinia
Family: Trachphylliidae
Trachyphyllia geoffroyi is a monotypic genus in a paraphyletic family (a taxonomic group that does not include all of the descendents of a common ancestor) that has long evolutionary branches and a long fossil record dating back to the Eocene period. Molecular analysis of  Trachyphyllia geoffroyi places it in a large clade (XVII) along with members of the Faviidae, Merulinidae and Pectiniidae family.

 
Description
Size: 
Up to 20cm in length
Trachyphyllia geoffroyi has a distinctive appearance, although its morphology can vary. This species can be found as individual polyps or as a small colony of a few polyps growing together. The individual polyps have a distinctive hour-glass shaped appearance and a centrally located mouth. During the day a large mantle, which looks like a pillow full of air is extended but this will retract if disturbed.

Small colonies may have an extended hour-glass shape giving the edges of the colony a wavy appearance. There can be up to three mouths in a colony. Large colonies of Trachyphyllia geoffroyi are less common and can be quite different in appearance to the individual polyps and smaller colonies. The corallites in these large colonies will be arranged in thick, twisted rows with wide valleys between them, an appearance more similar to an open brain coral.

Trachyphyllia geoffroyi is usually brightly coloured and can be yellow, brown, blue or green. Sometimes it has a stripy green and blue appearance. At night several rows of pale coloured tentacles with white tips are extended from the oral disc.
Ecology
T. geoffroyi is a zooxanthellate coral which means that a symbiotic relationship with single-celled algae called zooxanthellae provides energy to the coral. These zooxanthellae live in the tissue of the coral and provide its host with energy through photosynthesis. T. geoffroyi also has well developed tentacles which catch planktonic prey when extended so this species is able to supplement its diet.

T. geoffroyi is a hermaphroditic coral which means that both female and male sex organs are located within each polyp. Sexual reproduction occurs when sperm and eggs are released from all polyps in a synchronous spawning event that increases the chance of fertilisation. Fertilised eggs develop in to planulae which will be carried by the water current to a suitable settlement site where the planulae will develop into a polyp. Asexual reproduction occurs though a process called budding. In T. geoffroyi small buds will form at the base of the colony and emerge once another polyp has died to take its place.
Habitat
Usually found at depths below 12m down to maximum of 40m Trachyphyllia geoffroyi is often found on muddy or sandy substrates around islands or in inter-reef environments rather than on the reef itself. It also shows preference for habitats with a gentle water flow.
Distribution
Trachyphyllia geoffroyi has an extensive distribution from Egypt and the Red Sea, down as far south as Somalia and Madagascar on the east coast of Africa. Heading east across the Indian Ocean, this species is also found in the Chagos Archipelago and Sri Lanka. Distribution across Asia is extensive spreading from Burma eastwards as far as the Pacific Islands such as Vanuatu, with Japan as the most northerly and Australia as the most southerly latitudes in which this species is found.
Population Estimate
There has been no global population estimates made for this species, although one study carried out around Lizard Island found Trachyphyllia geoffroyi in low densities.
Population Trend
The population of Trachyphyllia geoffroyi is thought to be decreasing. There has been a world-wide decline in coral reef populations with 19% of the reefs already destroyed with no hope of recovery.
Status
Near Threatened (NT) 2010.4 IUCN Red List of Threatened Species.
Threats
The aquarium trade is a major threat to Trachyphyllia geoffroyi with live specimens extracted from the wild and exported across the world. The 2010 CITES export quote for this species allows 4,750 live pieces to be exported from Fiji and 50,000 pieces from Indonesia. Unfortunately, this quota is not based on scientific advice and there is no way of knowing if the level of harvesting is sustainable. In addition to the pressure on the population of Trachyphyllia geoffroyi the techniques used to collect wild coral for the aquarium trade can cause physical damage to the reef.

Ocean acidification and coral bleaching are also threats to Trachyphyllia geoffroyi and both these threats are linked to increasing levels of atmospheric carbon dioxide and climate change. Current atmospheric CO2 levels are approximately 388ppm and rising and in response the ocean is absorbing an increasing amount of CO2. This uptake of CO2 is changing the pH of ocean water as the dissolved CO2 forms carbonic acid, altering the ratio of pH-maintaining buffers. Coral skeletons are vulnerable to acidification as it reduces growth rate and causes the skeletons to become more brittle and therefore more vulnerable to damage.

Thermal induced coral bleaching occurs when sea surface temperatures are higher than normal and in response to this stress the coral host expels the symbiotic algae, zooxanthellae, from its tissue. As well as leaving the coral with a white, bleached appearance it also leaves the coral without its primary source of energy. If bleaching is prolonged the coral may not recover its zooxanthellae and die. As global temperatures continue to rise bleaching will become a more frequent event and an increasing threat to coral reefs.

Direct human threats to Trachyphyllia geoffroyi are over-fishing and poor land management leading to increased sedimentation and the pollution of coastal areas. Over-fishing continues as demand for protein continues to rise and the removal of herbivorous fish can result in the rapid growth of algae which can out-compete the growth of coral and become the dominant feature of a reef.

As coastal populations grow there is increasing land development which can lead to sedimentation and pollution of coastal seas.. In particular the removal of mangroves and sea grasses, the natural bio-filters, can result in many coral reefs being smothered by sediment washed off of the land. Sedimentation is the suspension of particles in the water and this can reduce the light available for photosynthesis and smother coral, potentially suffocating it. In addition to the sedimentation, development of the coastline can increase the amounts of pollution discharged into coastal areas, often without proper treatment. This pollution may disease inducing and the additional stress caused by low water quality makes the coral more susceptible to bleaching and other diseases.

 
Conservation Underway
Trachyphyllia geoffroyi, like all corals is listed on CITES Appendix II which regulates the international trade of threatened species. In addition to this the EU Scientific Review Group has banned all imports of wild Trachyphyllia geoffroyi from Fiji and Indonesia in to the EU. This will reduce the global demand for this species by the aquarium industry and may reduce the number that is harvested.

In addition to this legislation there are a number of marine protected areas (MPAs) and regional initiatives that are helping to conserve Trachyphyllia geoffroyi. For example, the creation of the Chagos Marine Protected Area in April 2010 resulted in the largest MPA in the world protecting 544,000 square kilometres of land and ocean within the British Indian Ocean Territory.

One initiative involving the conservation and research of coral reefs is CORDIO: Coastal Research and Development in the Indian Ocean. This initiative operates in East Africa, the West Indian Ocean Islands, South Asia, Andaman Sea and Red Sea and focus’ on research on coastal and ocean ecosystems as well as social and economic aspects in order to integrate science, practice and policy so that they can educate and build capacity in Indian Ocean regions.

In the Coral Triangle which includes countries such as Malaysia, the Philippines, Papua New Guinea and the Solomon Islands and Timor Leste the ‘Coral Triangle Initiative on Coral Reefs, Fisheries and food Security’ is encouraging people-centred initiatives in conservation and sustainable development and is supported by the Australian and US Governments as well as a number of NGOs and charities.
Conservation Proposed
Further research into the population and ecology of Trachyphyllia geoffroyi would help determine if the current export quotas set by Indonesia and Fiji are sustainable. The EU has already banned the import of this species and so the exporting countries should also evaluate their quotas.

In the conservation of this species it is essential that all MPAs and conservation initiatives are effectively managed, enforced and sustained. The effectiveness of MPAs is improved by international networks and sharing of knowledge so it is essential that partnerships between all the members of an initiative are sustained. One study has found that just 2% the world’s coral reefs are within MPAs that combine the necessary factors for adequate conservation suggesting that urgent re-assessment of global strategies is required.
Links
References

Fisk, D.A. (1983) Free-living corals: distributions according to plant cover, sediments, hydrodynamics, depth and biological factors. Marine Biology 74:287-294

Mora, C. et al. 2006. Coral Reefs and the Global Network of Marine Protected Areas. Ecology 312:1750-1751

Secretariat of the Convention on Biological Diversity (2009). Scientific Synthesis of the Impacts of Ocean Acidification on Marine Biodiversity. Montreal, Technical Series No. 46, 61 pages.

Sheppard, C., Turak, E. & Wood, E. 2008. Trachyphyllia geoffroyi. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. <www.iucnredlist.org>. Downloaded on 29 November 2010.

Titlyanov, E.A. and Latypov, Y.Y. 1991. Light-dependence in scleractinian distribution in the sublittoral zone of South China Sea Islands. Coral Reefs 10:133-138

Veron J.E.N. 2000. Corals of the World. Volume 2. Townsville. Australian Institute of Marine Science

Veron, J.E.N. et al. 2009. The coral reef crises: The critical importance of <350 ppm CO2. Mar Pollut Bull. 58:1428-1436

Wilkinson, C. 2008. Status of coral reefs of the world: 2008. Global Coral Reef Monitoring Network and Center, Townsville, Australia.

 

Distribution map based on data provided by the IUCN Spatial Data Collection.

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