Pearl bubble coral (Physogyra lichtensteini)

Physogyra lichtensteini showing tentacles extended
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Pearl bubble coral fact file

Pearl bubble coral description

GenusPhysogyra (1)

The sole member of its genus (3), Physogyra lichtensteini is a large coral, its colonies reaching up to three metres in diameter (1), and is usually pale grey or sometimes dull green in colour (3). As in other corals, the colonies are composed of numerous tiny, anemone-like animals known as polyps. In this species, the polyps are arranged in rows, separated by short but wide depressions, or ‘valleys’, which are interconnected with a light, blistery tissue known as ‘coenosteum’ (3) (4) (5). The internal skeleton of each polyp has long, solid, widely spaced septa, the radial elements that project inwards from the skeletal wall (3) (4). Colonies with very distinct septa were formerly considered a separate species, Plerogyra exerta (3). A conspicuous feature of Physogyra lichtensteini is the numerous bubble-like vesicles which cover the colony during the day. These vesicles may either be grape-like or forked in shape, and are retracted if disturbed. The tentacles of the polyps are extended only at night (3) (4) (5) (6).

Also known as
grape coral, octobubble coral, octopus coral, pearl coral, pointed bladder coral, small bubble coral, tipped bubblegum coral.
Physogyra exerta, Plerogyra exerta, Plerogyra lichtensteini.

Pearl bubble coral biology

Although it may use the stinging tentacles to capture tiny zooplankton, Pectinia lactuca, like many corals, obtains most of its nutrients from symbiotic algae, known as ‘zooxanthellae’, which live within its tissues. These produce energy-rich molecules through photosynthesis, transferring most of what is produced to the coral, which in turn provides a relatively stable and protected environment, and access to light. The individual polyps of the coral secrete a calcium carbonate skeleton, which in time builds up to form the coral reef (3) (8).

All colony-forming corals reproduce asexually by budding, a process in which the polyps divide into one or more new polyps. Sexual reproduction also occurs, with large numbers of eggs and sperm being released into the water. Once fertilised, the eggs develop into larvae, which drift in the water column until settling and developing into new polyps (3). In Physogyra lichtensteini, colonies consist of either all-male or all-female polyps. In the Great Barrier Reef, the species has been recorded spawning over just a few nights in late spring (9).


Pearl bubble coral range

Physogyra lichtensteini occurs across the Indian Ocean and western Pacific Ocean, and in the Red Sea, Arabian Gulf and Gulf of Aden (1) (3) (4).


Pearl bubble coral habitat

This species is found in shallow, tropical reefs, most commonly in turbid reef environments where light availability is low (1) (3) (5) (6). It is common in protected habitats such as crevices and overhangs (3) (4). In the South China Sea, the species has been recorded at depths of 9 to 15 metres (7), although it may occur from 1 to 20 metres in other areas (1).


Pearl bubble coral status

Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (2).

IUCN Red List species status – Vulnerable


Pearl bubble coral threats

Around a third of all reef-building corals are now believed to be threatened with extinction (10), and about 20 percent of coral reefs have already been lost to a range of threats, including disease, invasive species, overharvesting, destructive fishing practices, development and pollution. Global climate change may also pose a severe threat, potentially leading to an increase in severe storms, increased ocean acidification due to raised carbon dioxide levels, and a rise in sea temperature, which can stress the coral and cause it to expel its zooxanthellae, a process known as bleaching. These combined threats can also mean weakened corals are more susceptible to factors such as disease and parasites (1) (8) (10) (11).

Although Physogyra lichtensteini is still common and widespread, it is heavily harvested for the aquarium trade, with Indonesia being the largest exporter (1). Due to its large size, this export may involve broken pieces of coral, which have been reported to quickly expire (4).


Pearl bubble coral conservation

International trade in Physogyra lichtensteini should be monitored under its listing on Appendix II of the Convention on International Trade in Endangered Species (CITES) (2). Parts of its range also occur within Marine Protected Areas (1), although enforcement in these areas is often poor (8). Conservation measures recommended for this and other corals include the expansion and creation of new Marine Protected Areas; further research into the species’ populations, ecology, and resilience to various threats; reef monitoring and restoration activities; quotas for collection; and disease management (1) (8) (11). Artificial propagation techniques may also become an important tool for conserving coral biodiversity, particularly in light of the many threats faced by fragile reef environments (1).

View information on this species at the UNEP World Conservation Monitoring Centre.
Environment Agency - Abu Dhabi is a principal sponsor of ARKive. EAD is working to protect and conserve the environment as well as promoting sustainable development in the Emirate of Abu Dhabi.

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To learn about efforts to conserve Physogyra lichtensteini see:

For more information on corals and their conservation see:



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Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
Type of asexual reproduction (reproduction that does not involve the formation of sex cells), in which new individuals develop from the parent organism, forming a swelling similar in appearance to a bud. The ‘bud’ slowly separates from the parent as it grows.
A group of organisms living together. Individuals in the group are not physiologically connected and may not be related, such as a colony of birds. Another meaning refers to organisms, such as bryozoans, which are composed of numerous genetically identical modules (also referred to as zooids or ‘individuals’), which are produced by budding and remain physiologically connected.
The fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.
A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
Metabolic process characteristic of plants in which carbon dioxide is broken down, using energy from sunlight absorbed by the green pigment chlorophyll. Organic compounds are made and oxygen is given off as a by-product.
Typically sedentary soft-bodied component of cnidaria, a group of simple aquatic animals including the sea anemones, corals and jellyfish. A polyp comprises a trunk that is fixed at the base, and a mouth that is placed at the opposite end of the trunk and is surrounded by tentacles.
In a coral, radial elements that project inwards from the corallite wall (the skeletal wall of an individual coral polyp).
The production or depositing of large quantities of eggs in water.
Describes a relationship in which two organisms form a close association. The term is now usually used only for associations that benefit both organisms (a mutualism).
Tiny aquatic animals that drift with currents or swim weakly in water.


  1. IUCN Red List (May, 2010)
  2. CITES (May, 2010)
  3. Veron, J.E.N. (2000) Corals of the World. Australian Institute of Marine Science, Townsville, Australia.
  4. Erhardt, H. and Moosleitner, H. (1998) Marine Atlas. Volume 2. Mergus, Melle, Germany.
  5. Veron, J.E.N. (1993) Corals of Australia and the Indo-Pacific. University of Hawaii Press, Honolulu, Hawaii.
  6. Veron, J.E.N. (1995) Corals in Space and Time: The Biogeography and Evolution of the Scleractinia. Cornell University Press, Ithaca, New York.
  7. 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.
  8. Miththapala, S. (2008) Coral Reefs. Coastal Ecosystems Series (Volume 1). Ecosystems and Livelihoods Group Asia, IUCN, Colombo, Sri Lanka. Available at:
  9. Babcock, R.C., Bull, G.D., Harrison, P.L., Heyward, A.J., Oliver, J.K., Wallace, C.C. and Willis, B.L. (1986) Synchronous spawnings of 105 scleractinian coral species on the Great Barrier Reef. Marine Biology, 90: 379-394.
  10. Carpenter, KE et al. (2008) One-third of reef-building corals face elevated extinction risk from climate change and local impacts. Science, 321: 560-563.
  11. Wilkinson, C. (2008) Status of Coral Reefs of the World: 2008. Global Coral Reef Monitoring Network and Reef and Rainforest Research Center, Townsville, Australia. Available at:

Image credit

Physogyra lichtensteini showing tentacles extended  
Physogyra lichtensteini showing tentacles extended

© David Wachenfeld / Auscape International

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