Diadema antillarum

Geographic Range

Diadema antillarum is found in the shallow waters of the Atlantic Ocean, in the Bahamas, and the Western Atlantic from eastern Florida to Brazil. In the Eastern Atlantic D. antillarum is found in Madeira, the Gulf of Guinea, and the Canary, Cape Verde, and Annabon islands.

• Biogeographic Regions
• atlantic ocean atlantic ocean
  • native native

Habitat

Diadema antillarum favors quiet waters, and is found most often in coral reefs. This species can also be found in turtle grass beds and on rock bottoms.

• Habitat Regions
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• reef reef

Physical Description

Diadema antillarum is a regular (round) urchin, and displays the pentamerism of echinoderms . Mature individuals of D. antillarum can reach up to 500 mm in diameter. Diadema antillarum has thin spines that range from 300-400 mm in length and can be up to four times the diameter of the test (skeleton formed inside the body). The spines are thin, hollow, and break easily. The test is rigid and there is a reduced amount of soft tissue in the body wall as compared to other species in the family Diadematidae .

The test and spines of a mature adult are typically black, but lighter colored spines may be intermixed, and in rare cases the urchin will be almost entirely white. The spines of juveniles are always banded with black and white. When the urchin dies, the spines falls off and the test remains.

At the base of the urchin are branched tentacles called tube feet, which help in gathering food, respiration, locomotion, and mucous production.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• radial symmetry radial symmetry

Development

The fertilized egg has two forms: the blastula and the gastrula. These swim close to the surface of the water with the aid of cilia, and can be dispersed quite far, depending on currents. These larvae are known as the echinopluteus, and can remain in the larval stage for an average of 4-6 weeks. As the larvae mature, a vestibule is created in what will be the oral side of the urchin. Tentacles grow from this opening, on which suction areas eventually emerge. When the tentacles have suckers, they are primary poda, which serve as locomotive tools when the larva sinks to the ocean floor. At this point the skeletal plates begin to develop. When the 5 ambulical plates are developed and the terminal plate lies next to the genital plates, the urchin is fully developed, though it will continue to grow for the rest of its life.

• Development - Life Cycle
• metamorphosis metamorphosis

Reproduction

Some populations of D. antillarum have been observed to congregate during their spawning season. There is no mating of individuals as fertilization and gestation occur in the open water.

The spawning of D. antillarum appears to be connected to the lunar calendar. During the summer season, the egg and sperm are released once during each lunar month. This spawning period is dependant upon temperature; populations in different hemispheres may spawn at different times depending on when the warm season occurs.

The egg and sperm are released into the water where they are fertilized and develop into the larval echinopluteus. Egg size has also been observed to change during the month. Spawning occurs when the eggs are largest.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • external external

There is no parental involvement post-spawning.

• Parental Investment
• pre-fertilization
  • provisioning

Lifespan/Longevity

The lifespan of D. antillarum is closely related to temperatures and food availability. Populations in warmer climates tend to have a quicker rate of development and shorter lifespan than those in colder climates.

Behavior

Extremely sensitive to light, D. antillarum remains in darker areas, like crevices in the reef, during the day, and emerges at night to feed. Groups of individuals can be found in open areas, and densities can reach up to 20 per square meter. This group size corresponds to the abundance of predators in the area.

A very active urchin, D. antillarum has a high reactivity and sensitivity to changes in light and water disturbances. The urchin will wave its spines in the direction of the upsetting occurence, and retreat to sheltered areas quickly, if need be.

• Key Behaviors
• nocturnal nocturnal
• motile motile

Communication and Perception

Diadema antillarum has a highly developed light sensitivity. When a shadow appears, the urchin waves its spines in the direction of the shadow and moves away from the shadow, often into a more protected area. In this sense, D. antillarum can almost 'see' predators. It is not known how individuals communicate with each other to aggregate.

• Communication Channels
• chemical chemical

• Other Communication Modes
• photic/bioluminescent photic/bioluminescent

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

Diadema antillarum grazes on the algal turf of coral reefs primarily during the night. Foods eaten include algal turf, young corals and zoanthids.

• Primary Diet
• carnivore carnivore
  • eats non-insect arthropods
  • eats other marine invertebrates
• herbivore herbivore
  • algivore
• omnivore omnivore

• Animal Foods
• aquatic or marine worms
• cnidarians
• other marine invertebrates
• zooplankton zooplankton

• Plant Foods
• algae

Predation

The spines of Diadema antillarum are brittle and will fragmentize if wounded. The pieces are difficult to remove, and often cause infections as they carry bacteria. The mucous coating of the spines, normally used to kill organisms that live in the spines, carries a mild poison that also aids in deterring smaller predators. Diadema antillarum has been observed to gather in groups as an added protection.

Ecosystem Roles

Diadema antillarum feeds on the algal turf of the coral reefs. The algal turf grows rapidly, and without the urchin's control, can destroy the reefs. Diadema antillarum clears the reefs, making room for coral larvae to settle and grow. However, the urchin actually wears away at the calcium carbonate of the reef, too.

Economic Importance for Humans: Positive

The gonads of sea urchins are considered a delicacy in many coastal regions, but D. antillarum is not one of the more preferred species.

Sea urchin eggs are used extensively in embryological research.

• Positive Impacts
• food food
• research and education

Economic Importance for Humans: Negative

The spines of D. antillarum are very sharp and can easily pierce skin, shoes, and wetsuits. Contact with a spine is not extremely painful, but the shattering of the spine leaves organic material in the wound that can cause intensely painful infections. The poisonous mucous seems to have very little effect on humans.

• Negative Impacts
• injures humans
  • bites or stings

Conservation Status

Other Comments

In 1983 D. antillarum experienced a massive die-off all across the Caribbean; some areas lost up to 97% of mature individuals. The die-off is thought to be due to a water-borne pathogen that has not yet been identified. The great reduction of D. antillarum in the reefs caused an extreme increase in the algal cover, and thus a reduction of larval coral settlement. Microalgae has become more abundant in the time since the die-off; the greater amount of algae allows the reefs to support a greater number of herbivorous fish, which can result in more damage to the reefs.

Additional Links

Encyclopedia of Life

Contributors

Renee Sherman Mulcrone (editor).

Erin Puckett (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

References

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