Pearl Bubble Coral
(Physogyra lichtensteini)
Physogyra lichtensteini is a physically and genetically distinct coral species whose colonies can grow to extraordinary sizes. Throughout the day, a colony surface is adorned with spherical fleshy vesicles. These have been found to provide refuge for small crustaceans such as the bubble coral shrimp and are known to be an important food source for some populations of hawksbill turtles. At night, the species extends thick fleshy tentacles in order to catch food suspended in surrounding waters. This coral is widely distributed across the Indian and Pacific Oceans where it often favours turbid and shallower waters. Colonies reaching 3 metres in length can be found growing at depths of 1-20 metres.
Urgent Conservation Actions
No species specific conservation is ongoing for Physogyra lichtensteini.
A wide ranging species spanning from East African coastlines to the Central West Pacific.

The commensal shrimp species Vir philippinesis is highly reliant on the pearl bubble coral as a source of refuge against predation.
Associated Blog Posts
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8th Mar 13
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13th Jul 12
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Evolutionary Distinctiveness
Order: Scleractinia
Family: Euphyllidae
The family Euphyllidae consists of five zooxanthellae genera, all found in Indo-Pacific regions. Physogyra is one of these genera and Physogyra lichtensteini is its only member meaning it is monospecific. This species retains a high degree of evolutionary distinctiveness as a result of its few close relatives.

Colonies up to 3m across
Physogyra lichtensteini is a colonial species that can form massive (spherical) colonies with a bubble like appearance. Corallites, the skeletons of individual polyps, are arranged side by side in rows separated by wide valleys which are interconnected with blister-like tissue. During the day the surface of the entire colony is covered with many small vesicles, structures that look like bubbles and protrude outwards. The shape of these vesicles can be smooth and rounded like a bubble or have a fork shaped edge. These vesicles will retract when disturbed. During the night tentacles are extended and the colony has a pale grey, almost white colour.
An overview of hard coral ecology can be found here.

Physogyra lichtensteini is a colonial, stony species meaning that as the individual animals (polyps) of this species grow, they exude calcium carbonate to form exoskeletons (corallites) for protection. Specific oceanic conditions are required for polyps to synthesize and exude calcium carbonate

As a zooxanthellate coral Physogyra lichtensteini obtains much of its energy from a symbiotic relationship with algae called zooxanthellae. Zooxanthellae live in the tissue of coral and require sunlight for photosynthesis, a process that produces energy for the algae and its host coral. Additional nourishment is provided through the catching of prey using fleshy tentacles which this species extends day and night.

Along with just 25% of coral species, colonies of Physogyra lichtensteini are gonochoristic.  As broadcast spawners each colony will release eggs or sperm into the water where fertilization occurs. To increase chances of fertilisation spawning is synchronised with all colonies releasing their eggs and sperm at similar times. Spawning occurs after sunset a few days after a full moon in late spring.

The structure of Physogyra lichtensteini colonies makes them suitable for small crustaceans such as shrimp to inhabit. Shrimp are able to use spaces between the individual vesicles as a place to hide from larger predators making it can ideal refuge. In Aldabar reserve in the Seychelles, research has shown that this species is also a preferred food source for hawksbill turtles.

Species associated with the Pearl bubble coral include Commensal shrimp such as Vir philippinesis (bubble coral shrimp), crabs such as Achaeus japonicus (orang-utan crab) and Hawksbill turtles, Eretmochelys imbricata.
Associated Species

Commensal shrimp such as Vir philippinesis (Bubble coral shrimp)

Crabs such as Achaeus japonicus (orang-utan crab)

Hawksbill turtles, Eretmochelys imbricata

This species displays a preference for shallow, turbid tropical waters at depths ranging from 1-20m. The species is also commonly found in crevices and overhangs and less frequently in other reef habitats.
The Pearl bubble coral has a wide distribution from the Red Sea and Southeast African coastline across the Indo-Pacific to Fiji in the Western Pacific Ocean. In terms of latitude, colonies are found growing as far north as Japan and as far south as New South Wales, Australia.
Population Estimate
There is no species specific population estimate for this species. It is considered relatively common.
Population Trend
Whilst a species specific population trend has not been researched, coral reefs in general have declined with 19% already lost globally and some 75% of the remaining systems subject to at least one serious threat. As such the population of this species is likely in decline.
Vulnerable (VU) 2012.2 IUCN Red List
A major threat to this species in particular is that of their export in the live coral trade. As of 2012, 11,000 specimens were permitted to be extracted annually from the wild. This figure has been consistent over recent years and it is not currently known whether this is a sustainable level of trade. It is also likely that additional specimens are traded under the radar of CITES, the agreement under which quotas are set for trade in coral.

A range of other threats are likely to impact this species to varying extents. The vast majority of coral reefs in the Indo-Pacific for example are threatened by overfishing and destructive fishing practices. With some 138 million people living close to the coast in this region, there is a high level of coastal development and deforestation, which will undoubtedly impact reefs through introducing pollution and increasing sedimentation amongst other threats.

Numerous additional stressors undoubtedly impact this species although the extent of their impacts will vary spatially and temporally. To read more on the threats to coral reefs, click here.

Conservation Underway
Physogyra lichtensteini, as with all corals is offered some protection through their inclusion in CITES Appendix II which manages the export of threatened species.

Additionally parts of the species range do overlap within marine protected areas (MPAs) and Locally Managed Marine Areas (LMMAs). One major marine reserve within which this species is known to persist is the Chagos Marine Protected Area (MPA) which, when implemented was the largest marine reserve in the world.

Some protection is also granted to this species through regional initiatives. Schemes such as the ‘Coral Triangle Initiative on Coral Reefs, Fisheries, and Food Security’ and the UNEP/Global Environment Facility South China Sea project ‘Reversing Environmental Degradation in South China Sea and Gulf of Thailand’ are multi-national developments that have worked to encourage sustainable marine development as well as effective conservation and management.

Additionally, the work of EDGE Fellows focusing on alternative coral species within the range of the Pearl bubble coral may well have positive implications for the conservation of this species.

This project supports in-country EDGE Fellows to help conserve relevant EDGE species

The project will develop and implement a conservation action plan for the mushroom coral (Heliofungia actiniformis), in the Polillo Islands in Luzon. This will act as a flagship for broader marine conservation action, including community and local government engagement and capacity building, as well as the implementation of coastal marine resource management plans.

This project will investigate the use of Marine Protected Areas for conserving three EDGE coral species in the Seychelles. It will investigate the presence/absence of the three species on carbonate and granitic reefs within Protected Areas. It will compare size distribution of EDGE corals within and outside of MPAs to establish whether MPAs are sufficient to protect these corals. Surveys will be carried out at two different depths to compare EDGE coral depth preference, to provide information to the government on the effectiveness of MPAs, for EDGE corals.

Conservation Proposed
With no suggested conservation measures, the species would benefit from further research into all aspects of its ecology, therefore allowing for scientifically informed conservation proposals.

The continued development of new marine reserves as well as the enhancement and improved management of existing areas would also benefit this species.

More must also be done to curb global emissions of greenhouse gases in order to prevent climate change and ocean acidification.

Finally, having timely access to trade analysis reports will allow for more effective monitoring of the species and allow for quicker responses to fluctuating populations. This in turn will allow efficient implementation of relevant management policies for the benefit of both the species and its habitat.
Associated EDGE Community members

Working on EDGE Coral Species in Southern Leyte, Philippines

A marine Research Officer working on the effectiveness of MPAs in protecting three EDGE coral species.

IUCN Red List of Threatened Species


Convention on International Trade in Endangered Species.

Babcock, R.C. et al. 1986. Synchronous spawning of 105 scleractinian coral species on the Great Barrier Reef. Marine Biology90:379-394.

Bauman, al. 2010. Tropical harmful algal blooms: An emerging threat to coral reef communities? Mar. Pollut. Bull.

Burke, L et al. 2011. Reefs at Risk Revisited. World Resources Institute. Washington DC.

Côté, I.M. and Reynolds, J.D. 2006. Coral Reef Conservation. Cambridge University Press, Cambridge.

Fransen, C.H.J.M. and Holthius, L.B. 2007. Vir smiti spec. nov., a new scleractinian associated pontoniine shrimp (Crustacea: Decapoda: Palaemonidae) from the Indi-West Pacific. Zool.Med.Leiden. 81(4) 8:101-114.

Fukami, H., Chen, C.A., Budd, A.F., Collins, A. Wallace, C. Et al. 2008. Mitochondrial and Nuclear Genes Suggest that Stony Corals are Monophyletic but Most Families of Stony Corals Are Not (Order Scleractinia, Class Anthozoa, Phylum Cnidaria). PLoS ONE 3(9):e3222. Doi:10.1371/journal.pone.0003222.

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.

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.

Turak, E., Sheppard, C. & Wood, E. 2008. Physogyra lichtensteini. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <>. Downloaded on 14 December 2012.

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

Wabnitz, C. et al. 2003. From ocean to aquarium. UNEP-WCMC, Cambridge, UK.

Veron, J.E.N. et al. 2009. The coral reef crises: The critical importance of <350 ppm CO2. Mar Pollut Bull58:1428-1436.

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

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