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Gorgonia ventalinaCommon sea fan

By Lee Goetz

Geographic Range

The geographic range of Gorgonia ventalina is from Bermuda to Curacao, including the Florida Keys and Western Caribbean. However, it is not found in the Gulf of Mexico. In geographic ranges, it is found in the southeastern part of the of the nearctic region and the northwestern part of the neotropical region. (Colin, 1978)

Habitat

Gorgonia ventalina is distributed in a clumped, non-random distribution on coral reefs. Usually the most common gorgonian in coral reef habitats, it is primarily found on band and patch reefs. In addition, the G. ventalina can be found in near-shore areas with heavy wave action and also on deeper reefs (depths greater than 15 m). (Colin, 1978)

Physical Description

Gorgonia ventalina is usually purple but can vary to its less common colors of yellow-orange, yellow, and brown. In some cases, the color of the sea fan is a result of the environment and the chemicals in the enviroment. The principle pigments of the sea fan are fixed in the spicules (needle-like parts of solid calcium carbonate). Colors result from chemical pigments produced in the spicules. Since the color of the fan varies, the shape of the spicules is the only positive identifier of G. ventalina. The spicules are small and fusiform. The polyps of the G. ventalina protrude from the spicules as tiny fragile white flowers. It is these individual polyps that form the sea fan.

Gorgonia ventalina can be up to 180 cm tall and 150 cm wide, with anastomose branches, which form uniplanar, reticulate, fan-shaped colonies. The branches are round or slightly compressed in the plane of the fan branch. (Colin, 1978; Kester, 1900; Sterrer, 1986)

  • Range length
    180 (high) cm
    70.87 (high) in

Development

Once a planulae polyp is settled on a hard surface, the young polyp creates a horizonatal layer of aragonite called the basal disk. As the polyp grows upward, the base's margin also turns upward, forming a cup called the epitheca, which contains daily growth bands. These and other sturctures called septa form the skeletal boundaries found at the bottom of the coral polyps, which are left behind as a result of the upward growth of the polyp. (Cary, May 15, 1915; Druffel, August 5, 1997)

Reproduction

Gorgonian corals reproduce asexually by cloning or fragmentation, with external fertilization. The larvae typically spend several days as plankton before settling on a hard surface to begin formation of a colony. (Druffel, August 5, 1997; Gotelli, April 1991)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

There are several potential causes of death for G. ventalina. The greatest cause of mortality is the disattachment of a colony from the substrate, most likely by wave action and storms. The overgrowth of the sea fan by other organisms is also another leading cause of death, especially by the hydrocoralline Millipora alcicornis and some encrusting bryozoa. The cause of death is attributed to the lack of food and oxygen to the polyp. Recently, mortality has also been attributed to tumor growth. The tumors observed on G. ventalina exposed to environmental stresses include the presence of pollutants, rising water temperature, increased nutrient concentrations, and increased turbidity. The large tumor masses, which were most often concentrated at the axial bases of the affected clonies were clearly associated with tissue death (necrosis) and erosion of the affected coral. According to Cary, there is no evidence that gorgonian colonies ever die from old age. (Cary, May 15, 1915; Morse, et al., 1977)

Behavior

Gorgonia ventalina will orient according so that the "fan" is perpendicular to the motion of the waves. This orientation only occurs in the adult sea fans. The young will grow in any direction, but as they mature will slowly shift until they are facing the current. (Grigg, March 1972)

Communication and Perception

In Anthozoans, specialized sensory organs are absent and nerves are arranged in nerve nets. Most nerve cells allow impulses to travel in either direction. Hairlike projections on individual cells are mechanoreceptors and possible chemoreceptors. Some Anthozoans show a sensitivity to light. (Brusca and Brusca, 2003)

Food Habits

Gorgonia ventalina is carnivourous, feeding on zooplankton, especially at night. A passive feeder, Gorgonia ventalina orients itself in the path of the sea current, so that the current flows past the fan and the zooplankton in the current are caught and eaten. In addition to being a carnivorous passive feeder, G. ventalina also has zooxanthellae, which extensively colonize the sea fan, especially in the epidermis, polyps, and gastrodermal canals and the anthocodial septae. These zooxanthellae, usually Symbiodinium sp., are also able to provide the sea fan with nutrients through its photosynthetic activities. (Morse, et al., 1977)

Predation

Gorgonia ventalina contains secondary metabolites and calcified sclerites that act as anti-predator defenses. These anti-predator defenses act as successful feeding deterrents to the Cyphoma gibbosum, a common predator of the G. ventalina. Cyphoma gibbosum feeds on gorgonian polyps by crawling slowly over the skeleton. Trotonia hamnerorum is a specialized predator on G. ventalina. (Cronin, et al., March 1995; Van Alstyne and Paul, September 1992)

  • Known Predators

Ecosystem Roles

Gorgonia ventalina has several ecosystem roles, primarily by serving as a substrate for many other organisms. For example, bivavle molluscs, sponges, and algae may grow on dead sections of the sea fan. However, it is not known if the growth of these organisms kills the sections or if they invade after the coral is already dead. Certain organisms, such as the brittle star and the basket starfish, use the tall G. ventalina to climb to a more advantageous position for filter feeding in reef areas. There have been studies into the role that sea fans, including G. ventalina, have in the formation of coral reefs. Conclusions were the limestone inner structure provides some of the base where other corals may attach to form more colonies. (Cary, May 15, 1915; Colin, 1978)

  • Ecosystem Impact
  • creates habitat
Mutualist Species
  • Symbiodinium sp.

Economic Importance for Humans: Positive

Compounds have been separated from G. ventalina to make antibiotics. These compounds include octacoral.

Gorgonia ventalina is popularly collected for use in aqauriums and as souvenirs.

As a colorful addition to coral reef habitats, its presence also is important to ecotourism. (Morse, et al., 1977)

Economic Importance for Humans: Negative

Could not find any adverse effects on humans.

Conservation Status

No current conservation details available.

Contributors

Renee Sherman Mulcrone (editor).

Lee Goetz (author), Hood College, Maureen Foley (editor), Hood College.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

asexual

reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

planktivore

an animal that mainly eats plankton

radial symmetry

a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sessile

non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

Bennett, I. 1974. The Great Barrier Reef. New York: Scribner.

Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc..

Cary, L. May 15, 1915. The Alcyonaria as a factor in reef limestone formation. Proceedings of the National Academy of Sciences of the United States of America, 1, (5): 285-289.

Colin, P. 1978. Caribbean Reef Invertebrates and Plants. Neptune City, NJ: TFH Publications.

Cronin, G., M. Hay, W. Finical, N. Lindquist. March 1995. Distribution, density, and sequestration of host chemical defenses by the specialist nudibranch *Tritonia hamnerorum* found at high densities on the sea fan *G. ventalina*. Marine Ecology - Progress Series, 119 (1-3): 177-189.

Druffel, E. August 5, 1997. Geochemistry of corals: proxies of past ocean chemistry, ocean circulation, and climate. Proc. Natl. Acad. Sci USA, Vol. 94, No. 16: 8354-8361.

Gotelli, N. April 1991. Demographic models for *Leptogorgia virgulata*, a shallow-water gorgonian. Ecology, 72 (2): 457-467.

Grigg, R. March 1972. Orientation and growth form of sea fans. Limnology and Oceanography, 17(2): 185 - 192.

Guthrie, M., J. Anderson. 1961. General Zoology. New York: John Wiley & Sons.

Kester, E. 1900. A Treatise on Zoology Part II. London: Adam and Charles Black.

Longhurst, A., D. Pauly. Ecology of Tropical Oceans.

Morse, D., A. Morse, H. Duncan. 1977. Algal tumors in the Caribbean sea fan *G. ventalina*. 3rd International Coral Reef Symposium Proceedings.

Sterrer, W. 1986. Marine Flora and Fauna of Bermuda. New York: Wiley.

Van Alstyne, K., V. Paul. September 1992. Chemical and structural defenses in the sea fan *G. ventalina* - effects against generalist and specialist predators. Coral Reefs, 11 (3): 155-159.

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