Ophiopholis aculeata

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Geographic Range

The most common of all brittle stars, they can usually be found worldwide in marine environments. A specific area to see these creatures is the Arctic South to Cape Cod and sometimes to East Long Island Sound.(Gosner 1978)

Habitat

Because brittle stars tend to be shy, they are usually found hidden within or beneath rocks in tidepools, or burrowing in the sand and mud. Usually they can be found in the lower intertidal zones up to almost 5000 feet deep.(Gosner 1978)

Physical Description

The daisy brittle star has a star-shaped body that is radially symmetrical and supported by a hard endoskeleton made of calcium. Its 5-7 spiny, jointed arms are attached to a central disk that contains the mouth and jaws, stomach, and saclike body cavities called bursa.

A characteristic of all echinoderms is the water vascular system. Water-filled canals branch out from a ring canal that encircles the gut. The canals lead to the brittle star's tube feet, which it uses for grasping and moving objects. Special sensory tube feet are used for sensory perception.

The mouth is made up of five moveable jaw segments, and food enters the mouth and goes directly into the stomach. There is no intestine and no anus, thus absorption and excretion is carried out by the bursa located at the base of each of the arms. Like all the echinoderms, the brittle star has no head and eyes, nor do their bodies contain a brain or a heart.

Daisy brittle stars have a disc diameter of up to 2 cm and its arms grow to about 8 cm long. It can grow a diameter of 5-7 mm in two years. Usually a reddish shade, the daisy brittle star frequently has dark bands on the arms, although colors and markings may vary. The upper arm plate of this species is ringed by small scales and 5-6 arm spines. The disk is covered with fine, blunt spines and large oval plates. When handled by humans or predators, the brittle star's arms can detach, hence the name.(Bernhard 1972, Gosner 1978, Kistner 1999)

Reproduction

Sexes are separate, and brittle stars tend to spawn at the end of the summer. The walls of the bursa are coelomic and contain gonads that discharge sex cells into the water for fertilization. The larvae is called the ophiopluteus and freely swims in the plankton until it transforms into the juvenile stage, when it settles on the ocean bottom. Brittle stars can also reproduce asexually; if a portion of the star breaks off and contains the central disk, it can regenerate into a new brittle star.(Balser 1998, Kistner 1999)

Behavior

Out of all the species of echinoderms, brittle stars are the most active and can move easily and quickly. The arms reach out in pairs to pull the animal along the ocean floor, similar to a slithering motion, which is where they are given the name serpent stars. These creatures tend to be shy and are normally nocturnal and hide in the crevices of rocks or in the sand during the day.(Bernhard 1972, Waggoner 1995)

Food Habits

Their main source of food are small bits of decaying matter and microscopic organisms. Sometimes they feed upon larger prey such as polychaete worms and small crustaceans.(Gosner 1978)

Economic Importance for Humans: Positive

Brittle stars have not had much of an impact upon humans. During the eighteenth century, Indonesians would cook and eat the brittle stars, but today they are simply more of an ornamental species, mostly enjoyed through observation in their habitats. Unlike the starfish, brittle stars are not harvested for souvenirs due to the fragile nature of their structure.(Kistner 1999)

Conservation Status

The greatest concern for brittle stars involves the conservation of their habitats. Pollution and disruption of the shores that they live in is harmful to not only the brittle stars but also to all the other marine animals dependent on this lifestyle. Currently hundreds of conservation organizations across the world are working to lower the level of risk being inflicted upon the marine environment. As long as people can be made aware of the dangers of pollution and the importance of conservation, the amount of marine life being destroyed can be minimized.

  • IUCN Red List [Link]
    Not Evaluated

Contributors

Celestine Kan (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

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

coastal

the nearshore aquatic habitats near a coast, or shoreline.

ectothermic

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

native range

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

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.

References

Balser, E. 1998. Cloning by Ophiuroid Echinoderm Larvae. Biological Bulletin, 194: 187-193.

Bernhard, .. 1972. Grzimek's Animal Life Encyclopedia Volume 3: Mollusks and Echinoderms. New York: Van Nostrand Reinhold Company.

Gosner, .. 1978. A Field Guide to the Atlantic Seashore. Boston: Houghton Mifflin Company.

Kistner, .. "Echinoderms" (On-line). Accessed February 17, 2000 at http://www.personal.psu.edu/users/g/c/gck106/.

Waggoner, .. "The Ophiuroidea" (On-line). Accessed February 17, 2000 at http://www.ucmp.berkeley.edu/echinodermata/ophiuroidea.html.