Marine Invertebrates of Bermuda

Brain Coral
(Diploria strigosa)

By Joseph Evans
Dr. James B. Wood and Kim Zeeh - Editors

Abstract  Taxonomy  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links 

Brain Coral, Diploria strigosa


Diploria strigosa is a common brain coral found in the tropics of the Atlantic Ocean. It is commonly known as Brain Coral and not many people know that D. strigosa has a brother, Diploria labyrinthiformis. To the untrained eye they look similar but they are quite different. In Bermudian waters these corals are protected by many laws such as the Coral Reef Preserve Act of 1966. This law prohibits the collection and destruction of coral reefs in two main marine protected areas that boarder the north and south shores of Bermuda. D. strigosa lives on the bottom of the sea in shallow reefs. It also has a very important symbiotic relationship with many tiny zooxanthellae. These zooxanthellae use photosynthesis to feed the coral tissue and in return the zooxanthellae get the corals metabolic waste. D. strigosa is a reef building coral.  It and other species of coral are the foundation on which the next generation of reef is built on. Its unique shape and textures make D. strigosa another beautiful attraction to the underwater world of coral reefs.


Phylum: Cnidaria
   Class: Anthozoa
    Subclass: Hexacorallia
     Order: Scleratinia
      Suborder: Faviida
       Family: Faviidae


Diploria strigosa is common on the reefs of the: Bahamas, Caribbean and Bermuda. It is commonly found in shallower waters between 1-30 meters but can also be found at depths up to 47 meters (Fricke 1985) .Its distribution is similar to that of D. labyrinthiformis, with the latter being able to live in areas of higher sedimentation. The clear low nutrient water of the tropics allows light to penetrate and reach the corals supplying them with energy derived from their zooxanthellae. This boulder coral and others like it make up the foundation for the reef itself. They can grow to enormous sizes and weigh several tons, there is really no limit to how big they can get, and as long as the coral is alive it will continue to grow at the average rate of 3.3mm per year (Logan 1994). This rate however is variable due to water temperature fluxuations and water clarity changes with the seasons (Harriott 1999).


Corals in general can reproduce both asexually and sexually. When D. strigosa reproduces sexually; this involves the process of gametogenesis. Gametogenesis is the production of gametes such as sperm, which can take just a few weeks or eggs which can take over ten months to produce. D. strigosa can reproduce asexually by fragmentation (Hunter 1990). D. strigosa is also a hermaphroditic species of coral; this means that they have the ability to produce both male and female gametes. So these corals cannot be distinguished by external sexual characteristics (Fadlallah 1983). This is beneficial to the corals when the probability of finding a member of the opposite sex is low, self-fertilization is then used to reproduce. In times when self fertilization is not needed the gametes will cross with other colonies gametes. D. strigosa uses the broadcast spawning method of fertilization; this is when the sperm and eggs combine in the water column or at the surface as opposed to brooding where fertilization occurs within the maternal polyp (Hunter 1990). The spawning corals such as D .strigosa are now at great risk. Most of their cross-fertilization occurs at the surface and if pollutants such as petroleum are floating on the surface the gametes will be destroyed. Spawning in D. strigosa mainly occurs at night and appears to be seasonally cued by temperatures, and is more finely tuned by the lunar phases to certain nights. Studies indicate that D. strigosa’s spawning season occurs for a short time in mid August (Szmant 1986). Temperatures for peak fertilization are between 25-29 degrees Celsius and if the temperatures rise above 30 degrees Celsius for any extended period larval developmental problems begin to occur. The resulting planula will drift on the ocean currents and then settle upstream to achieve larval competency, which means to successfully settle on an algae free substrate and undergo metamorphose into a coral polyp and begin laying down a calcium carbonate skeleton (Fadlallah 1983). Optimum temperature ranges for an adult corals’ growth and survival is between 25-29 degrees Celsius. Brain corals in Bermuda have adapted to live in cooler temperatures because Bermudas average temp is 20 degrees (Fricke 1985).Bermuda has cold winters and hot summers so the corals must be adapted to a wide variety of temperatures. The minimum temp that some corals have adapted to live in was 18 degrees Celsius. Most corals however, often live near their upper thermal limits, and in the summer months the corals will act negatively towards extended periods of warmer temperatures. When sea surface temperatures reach 29.5 -30 degrees Celsius and stay there bleaching will occur (Bassim 2002).

Diploria strigosa and all other Hermatypic coral possess symbiotic zooxathellae that provides corals with photosynthate. This photosynthate constitutes the majority of the corals energy supply (Cook 1983). These zooxanthellae use photosynthesis to feed the coral tissue and in return the zooxanthellae get the corals metabolic waste. Very little energy is actually derived from catching planktonic organisms. These zooxathellae are what gives coral such as D. strigosa its color. The term coral bleaching refers to the loss of a corals zooxanthellae. Corals are rather susceptible to bleaching; extended periods of higher then normal temperatures can trigger a widespread bleaching event. Chemicals in the water and bacterial infections can also cause bleaching in corals. The most recognizable coral diseases which effects D. strigosa, is Black Band Disease. This disease is easily recognizable by its distinct black band that leaves a bare white skeleton behind it.

Diploria strigosas’ main mechanism of aggression is by extracoelenteric digestion with its mesenterial filaments. D. strigosa can extrude its guts and digest its enemies then retract its guts back inside (Logan 1984). This is a common coral defense system; however it only works against other corals. Most corals such as D. strigosa have no defense against coral eating fish such as parrot fishes. This coral has a few more tricks up its sleeve; sedimentation is a devastating problem for many corals. D. strigosa is a rather efficient sediment remover; it uses four mechanisms of sediment rejection; polyp distension, tentacular movement (tentacles 2-6mm in length), ciliary action (most prominent) and mucus production (Sander 1987 and Bak 1976). D. strigosa shares these traits with other corals as well: D. labyrinthiformis, Montastrea cavernosa, Siderastrea siderea, and Meandrina meandrites (Sander 1987).

Recent Research

Recent studies are suggesting that the average global atmospheric temperature will rise as time goes on. This implies that sea surface temperatures will also rise and have negative effects on coral larval development. Bassim 2003, observed and record how elevated temperatures and ammonium levels effect larval development and survivorship of Diploria strigosa. This study showed that D. strigosa planulae had exponentially decreasing survival rates as the water temp was raised from 28 degrees Celsius to 32 degrees Celsius (Bassim 2003). Other studies regarding D. strigosa involve the use of X-ray computed tomography to record and learn more about the corals skeletal growth bands. Skeletal growth bands can be an important tool for reconstructing the past climate conditions (Dodge 2000).

Commercial Importance

Tourism is the main commercial importance of Diploria strigosa, it helps bring snorkelers and divers alike to areas that are populated by this and other species of coral. Its a two million dollar industry just in the Caribbean that dive shops and charter boats all over the topics take advantage of, bringing hundreds of people a day out to experience nature’s underwater beauty. Along with this, the reef is home to many invertebrates and vertebrates that are of commercial importance as well. Lobsters, shellfish and fish all use the reefs as nurseries for their young to be protected until they get big enough to be harvested.

Bermuda Laws

The Coral Reef Preserve Act of 1966 protects marine plants and animals within the two main marine protected areas. These two areas make up most of Bermuda's fringing reef. These two marine protected areas are located on the north and south sides of the island. The South Shore Coral Reef Preserve is much smaller the Northern MPA, it consists of a thin area that stretches almost the entire length of Bermuda’s south shore. The North Shore Coral Reef Preserve is a much bigger area and encompasses a majority of the northern lagoon reef out to the rim reef. It is illegal to remove, damage, or possess any plants or animals, dead or alive, which are attached to the sea-bed or any reef in the two areas. Another law, the Protected Species Order of 1978 states that the gathering of any types of coral (including D. strigosa) as well as other types of animals within the 200 mile exclusive fishing zone is prohibited. Bermuda also has 29 No Take areas with radius sizes ranging from 100 to 1000 meters. These areas are marked with mooring buoys and are labeled with the distance from the buoy that the no take area encompasses (Wood and Jackson 2005). More information on these laws can be found online at

Personal Interest

Brain corals are some of the most unique organisms under the water. When I was young I saw a picture of a brain coral in an encyclopedia. I was in wonder of this thing that was under the water, I had no clue what it was. To be able to come here and study them is like an unrealized dream come true (LOL).


Bak, R.P.M. and Elgershuizen, J.H.B.W. (1976) Patterns of Oil-Sediment Rejection in Corals. Marine Biology Vol 37. pgs 105-113

Bassim, K.M., Sammarco, P.W., and Snell, T.L. (2002) Effects of temperature on success of (self and non-self) fertilization and embryogenesis in Diploria strigosa (Cnidaria, Scleractinia). Mar Biol 140. pgs 479-488

Bassim, K.M., Sammarco, P.W., (2003) Effects of temperature and ammonium on larval development and survivorship in scleractinian coral (Diploria strigosa). Marine Biology Vol 142. pgs 241-252

Cook, C.B. and Knap, A.H. (1983) Effects of crude oil and a chemical dispersant on photosynthesis in the brain coral Diploria strigosa. Marine Biology Vol 78. pgs 21-27

Dodge, R.E., Helmle, K.P., and Ketcham, R.A. (2000) Skeletal architecture and density banding in Diploria strigosa by X-ray computed tomography. Proceedings 9th International Coral Reef Symposium, Bali, Indonesia 23-27 October 2000, Vol 1. pgs 365-371

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Harriott, V.J. (1999) Coral growth in subtropical eastern Australia. Coral Reefs Vol 18. pgs 281-291

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Logan, A. Interspecific Aggression in Hermatypic Corals from Bermuda. Coral Reefs Vol 3. pgs 131-138

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Szmant, A. (1986) Reproductive ecology of Caribbean reef corals. Coral Reefs Vol 5. pgs 43-54

Wood, J.B. and Jackson, K.J. (2005) Caribbean Marine Biodiversity; the Known and Unknown. DEStech Publications, Inc.pgs 19-36


Brain Coral
Bermuda Marine Laws
Brain Corals