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Oreaster reticulatuscushioned star

By Rachel Miranda and Shital Patel

Geographic Range

The cushion seastar, Oreaster reticulatus, ranges from around South Carolina to the Caribbean Islands, and is most common in the shallow waters in the Carribean. The cushion seastar has been introduced to the Cape Verde Islands in Western Africa. (Wulff, 1995)

Habitat

Oreaster reticulatus is found in calm, shallow, subtropical and tropical water. A majority of individuals tend to be found on coarse, calcereous sandy bottoms that are isolated or surrounded by seagrass. However, this seastar can also be located in soft sand and mud substrates that are associated with shallow reefs, mangroves, or lagoons. (Guzman and Guevara, 2002; Puglisi, 2000)

  • Range depth
    1 to 37 m
    3.28 to 121.39 ft

Physical Description

Oreaster reticulatus is a large seastar with a central disc from which its five tapered arms radiate. The cushion seastar can grow up to 0.50 m in diameter, depending on food availability. The seastar's body is covered by a hard outer shell with knobby spines, or ossicles, that extend away from the surface. Oreaster reticulatus is not polymorphic and can be easily distinguished from closely related species by their hard shell and short tapered arms. Individuals vary in color and can be brown, red, orange, or yellow. The juveniles are green, which provides camouflage from predators. (Puglisi, 2000)

  • Range length
    0.20 to 0.50 m
    0.66 to 1.64 ft

Development

Oreaster reticulatus lays large and bouyant eggs in water currents. The planktonic larvae will be completely developed but will loose their bouyancy, settle and metamorphose in seagrass beds within 23 days at 23 degrees C. Sexual maturity is reached at a radius of 0.12 m. The last juvenile stage measures 0.06-0.12 m in length. (Metaxas, et al., 2008)

Reproduction

Fertilization is external. Sperm and eggs are released when a male and a female seastar are in close proximity. The seastars will reproduce when there are dense aggregations, up to 14 per square meter. Having large numbers of males and females ensures eggs will be fertilized. ("Seastar", 2009; Puglisi, 2000)

In subtropical areas, Oreaster reticulatus reproduces synchronously during the summer. In warmer areas, asynchronous spawning can occur year round. (Puglisi, 2000)

  • Breeding interval
    The cushioned star spawns yearly during the summer in subtropical areas; it continuously spawns in warmer areas.

Parental care is negligible. The planktonic larvae are dispersed over long distances and feed on their own. (Puglisi, 2000)

  • Parental Investment
  • pre-fertilization
    • provisioning
  • pre-hatching/birth
    • provisioning

Lifespan/Longevity

The lifespan of the cushion seastar depends on food availability. If there is low food availability, the cushion star will re-absorb its own tissue, which leads to a reduction in size. (Puglisi, 2000)

Behavior

The cushion seastar is a solitary species and moves around slowly using its tube feet. It can move approximately 0.12-0.33 m per minute and is active during the day. (Freeman, 2011)

Communication and Perception

Cushion seastars recognize when a potential mate is in close proximity. To increase chances of fertilization, individuals aggregate when ready to spawn. These events rely on environmental cues, such as the length of daylight. Seastars are able to sense light and dark, and therefore movement, through a microscopic eye called an ocellus. The seastars may use chemical signals to indicate that they are ready. ("Seastar", 2009; Hutchins, 2004)

Food Habits

The cushion seastar is an omnivore and also a deposit feeder. Oreaster reticulatus feeds on echinoids, holothuroid juveniles, and other invertebrates including polychaete worms, copepods, ostracods, crab larvae and sponge tissue. The seastar piles sediments and everts its large cardiac stomach, which allows it to surround the food. Digestive juices are then excreted to break down the food. (Guzman and Guevara, 2002; Puglisi, 2000)

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

Predation

Seastars are most vulnerable to predation at the larval and juvenile stages, and are presumably preyed upon by fish or other echinoderms. Juvenile O. reticulatus are green, which provides camouflage.

The only recorded predator for an adult cushion seastar is the triton Charonia variegata, which is a gastropod. The cushion seastar's daily activities coincide with the changes in light intensity, usually around dusk and dawn. This allows them to avoid predators and arrange foraging activity with the activity of their prey. ("Seastar", 2009; Hutchins, 2004; Scheibling, 1980)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Via feeding, the cushion seastar can turn over sediment at a rate of 1.9 times in a 24-hour period. (Puglisi, 2000)

Economic Importance for Humans: Positive

Cushion seastars are large and easily seen and are thus of sight-seeing value. They have also been heavily harvested as souvenirs. (Hutchins, 2004)

Economic Importance for Humans: Negative

There are no known adverse effects of Oreaster reticulatus on humans.

Conservation Status

This species is not listed on the IUCN Red List, CITES appendices, the United States Endangered Species Act list, but it is protected in the Carribean because of over-exploitation by souvenir hunters. (Puglisi, 2000)

Contributors

Rachel Miranda (author), Rutgers University, Shital Patel (author), Rutgers University, David V. Howe (editor), Rutgers University, Renee Mulcrone (editor), Special Projects.

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

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

diurnal
  1. active during the day, 2. lasting for one day.
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

filter-feeding

a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.

herbivore

An animal that eats mainly plants or parts of plants.

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.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

native range

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

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

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

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

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.

scavenger

an animal that mainly eats dead animals

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

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.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

zooplankton

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

References

2009. "Seastar" (On-line). Accessed January 13, 2011 at http://www.absoluteastronomy.com/topics/Sea_star.

Freeman, S. 2011. "Cushion star (Oreaster reticulatus)" (On-line). Grzimek's Animal Life. Accessed January 14, 2011 at http://animals.galegroup.com/web/grzimeks/animals/Oreaster_reticulatus?searchTerms=oreaster.

Guzman, H., C. Guevara. 2002. Annual reproductive cycle, spatial distribution, abundance, and size structure of Oreaster reticulatus (Echinodermata: Asteroidea) in Bocas del Toro, Panama. Marine Biology, 141 (6): 1077-1084.

Hutchins, M. 2004. Lower metazoans and lesser deuterstomes. Pp. 367-370 in D Thorney, N Schlager, eds. Grzimek's Animal Life Encyclopedia, Vol. 1, 2nd Edition. Farmington Hills, MI: The Gale Group, Inc.

Metaxas, A., R. Scheibling, M. Robinson, C. Young. 2008. Larval development, settlement, and early post-settlement behavior of the tropical sea star Oreaster reticulatus. Bulletin of Marine Science, 83 (3): 471-480.

Puglisi, M. 2000. "Oreaster reticulatus" (On-line). Smithsonian Marine Station at Fort Pierce. Accessed March 09, 2011 at http://www.sms.si.edu/IRLSpec/Oreaster_reticulatus.htm.

Scheibling, R. 1980. Abundance, Spatial Distribution, and Size Structure of Populations of Oreaster reticulatus (Echinodermata: Asteroidea) on Sand Bottoms. Marine Biology, 57: 95-105.

Wulff, J. 1995. Sponge-feeding by the Carribean starfish Oreaster reticulatus. Marine Biology, 123: 313-325. Accessed March 09, 2011 at http://cat.inist.fr/?aModele=afficheN&cpsidt=3670445.

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