Odontaster validus

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Geographic Range

Red sea stars are found in the Antarctic region, most prevalently in the waters surrounding the Antarctic continent and islands. ("Odontaster validus Koehler, 1906", 2012)

Habitat

Red sea stars are unique amongst sea stars in their ability to withstand the cold environment of the Antarctic region (averaging -1.8 degrees Celsius). They live at depths of 0-914 meters and are found most often in shallower waters (14 m). ("Odontaster validus Koehler, 1906", 2012; Kidawa, 2009; Pearse, 1963; Stanwell-Smith and Clarke, 1998)

  • Range depth
    0 to 914 m
    0.00 to 2998.69 ft

Physical Description

Like most other sea stars, red sea stars have a central disk with five arms radiating outward. These sea stars are typically a dark shade of red dorsally and a light shade of pink ventrally. Red sea stars have a rather large lightly-colored, pink madreporite dorsal plate which is an opening to its water vascular system. Red sea stars grow 1-2 grams per year and range from 2-11 centimeters in diameter (average 6-8 centimeters). There are no externally visible physical features distinguishing males and females of this species. ("Odontaster validus Koehler, 1906", 2012; Janosik and Halanych, 2010; Kidawa, 2009; McClintock, et al., 2008)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    2 to 11 cm
    0.79 to 4.33 in
  • Average length
    7 cm
    2.76 in

Development

Fertilized eggs develop into planktotrophic larvae, allowing members of the species to disperse. Red sea stars have a rather slow rate of growth, typically gaining 1-2 grams per year. ("Odontaster validus Koehler, 1906", 2012; Janosik and Halanych, 2010)

Reproduction

As with most echinoderms, red sea stars reproduce via broadcast spawning and external fertilization. (Pearse, 1963; Stanwell-Smith and Clarke, 1998)

This species reaches sexual maturity at 3-6 years. Reproduction occurs once a year during the winter season, between the months of April and June, with peak spawning occurring during June. Scientists are able to determine when the sea stars are spawning by a decrease in the size of their gonads (sexual organs). Fertilization occurs from June to September. This sea star is known for releasing a large number of oocytes that, once fertilized, then mature into larva. The ova of this sea star typically take 18 months to mature. (Janosik and Halanych, 2010; Pearse, 1963)

  • Breeding interval
    Red sea stars breed once yearly.
  • Breeding season
    April to June
  • Range age at sexual or reproductive maturity (female)
    3 to 6 years
  • Range age at sexual or reproductive maturity (male)
    3 to 6 years

There is currently no evidence that red sea stars exhibit any parental investment. (Janosik and Halanych, 2010; Pearse, 1963)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

The lifespan of this sea star is not currently known, although there is evidence that they can live up to 100 years. ("Odontaster validus Koehler, 1906", 2012; Pearse, 1963)

  • Range lifespan
    Status: wild
    100 (high) hours

Behavior

This sea star is typically sedentary and often found attached to rocks in the water. They move significant distances only in times of extreme starvation or distress. Red sea stars exhibit "arm fencing," a behavior in which they compete for dominance and eating rights. ("Odontaster validus Koehler, 1906", 2012; Janosik and Halanych, 2010; Kidawa, 2009; Stanwell-Smith and Clarke, 1998)

  • Average territory size
    0.3 m^2

Home Range

These sea stars are found at an average density of 2.7 per m^2. (McClintock, et al., 2008)

Communication and Perception

Red sea stars detect their environments with using chemoreceptors, which they rely on to recognize potential prey. These chemoreceptors also have the ability to elicit an alarm response which tells the sea star to move away from the stimulus quickly. There is both interspecific and intraspecific communication using chemoreceptors. (McClintock, et al., 2008)

Food Habits

Red sea stars are omnivorous, feeding on a variety of species such as bivalves (e.g. Limatula hodgsoni and Laternula elliptica), sponges (e.g. Rossella racovitzae, Rossella nuda, Scolymastra joubini, Craniella leptoderma, and Homaxinella balfourensis), hydroids (e.g. Halecium arboreum), other echinoderms (e.g. Acodontaster conspicuus and Sterechinus neumayeri), and isopods (Glyptonotus antarcticus), as well as red algae, diatoms and seal feces. Due to the harsh environment of the Antarctic, red sea stars must be capable of surviving for long periods (potentially an entire winter) with no food. This sea star does not exhibit cannibalism; however, it is quite common for it to prey on other sea stars, particularly Acodontaster conspicuus. It is not yet known if red sea stars are more likely to search for food in groups or individually. ("Odontaster validus Koehler, 1906", 2012; Kidawa, 2009; McClintock, et al., 2008; Pearse, 1963)

  • Animal Foods
  • carrion
  • mollusks
  • aquatic crustaceans
  • echinoderms
  • cnidarians

Predation

Red sea starts tend to form larger clusters when a potential predator is sensed, as if to ward off any predators by seeming to be one large entity. This is unique because echinoderms are otherwise only known to form groups or clusters in order to better capture food or to increase the likelihood of fertilization. Known predators of red sea stars include sea anemones, sea stars, and jellyfish. ("Odontaster validus Koehler, 1906", 2012; Brueggeman, 1998; Kidawa, 2009; McClintock, et al., 2008; Pearse, 1963)

Ecosystem Roles

Red sea stars eat the larvae of several sympatric sea stars that prey on various sponge communities, sometimes so heavily as to negatively impact the sponges' populations. Therefore, these sea stars may help maintain sponge populations. (McClintock, et al., 2008)

Economic Importance for Humans: Positive

The Antarctic conditions required by red sea stars mean that they are usually not kept in captivity and so they have little economic importance for humans. ("Odontaster validus Koehler, 1906", 2012; Janosik and Halanych, 2010; McClintock, et al., 2008; Pearse, 1963; Stanwell-Smith and Clarke, 1998)

Economic Importance for Humans: Negative

There are no known negative economic impacts of this species.

Conservation Status

Despite the harsh conditions within the Antarctic, red sea star populations appear to be thriving and the species has no special conservation status. (Janosik and Halanych, 2010)

Contributors

Natalie Ramirez (author), Sierra College, Jeremy Wright (editor), University of Michigan-Ann Arbor.

Glossary

Antarctica

lives on Antarctica, the southernmost continent which sits astride the southern pole.

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

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

detritus

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

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

herbivore

An animal that eats mainly plants or parts of plants.

intertidal or littoral

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

keystone species

a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).

molluscivore

eats mollusks, members of Phylum Mollusca

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

phytoplankton

photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

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).

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

social

associates with others of its species; forms social groups.

References

2012. "Encyclopedia of Life" (On-line). Odontaster validus. Accessed August 31, 2012 at http://eol.org/pages/4704670/details.

Belgian Biodiversity platform. 2012. "Odontaster validus Koehler, 1906" (On-line). SCAR Antarctic Field Guides. Accessed March 11, 2012 at http://afg.biodiversity.aq/species/21-odontaster-validus.

Brueggeman, P. 1998. "Cnidaria – Scyphozoa: jellyfish UNDERWATER FIELD GUIDE TO ROSS ISLAND & MCMURDO SOUND, ANTARCTICA" (On-line pdf). Accessed August 31, 2012 at http://www.peterbrueggeman.com/nsf/fguide/cnidaria--scyphozoa.pdf.

Janosik, A., K. Halanych. 2010. Unrecognized Antarctic Biodiversity: A Case Study of the Genus Odontaster (Odontasteridae; Asteroidea). Integrative & Comparative Biology, 50/6: 981-992. Accessed March 11, 2012 at http://icb.oxfordjournals.org/content/50/6/981.full.

Kidawa, A. 2009. Food Selection of the Antarctic Sea Star Odontaster validus: Laboratory Experiments With Food Quality And Size. Polish Journal of Ecology, 57/1: 139-147. Accessed March 11, 2012 at http://www.pol.j.ecol.cbe-pan.pl/article/ar57_1_11.pdf.

McClintock, J., R. Angus, C. Ho, C. Amsler, B. Baker. 2008. A laboratory study of behavioral interactions of the Antarctic keystone sea star Odontaster validus with three sympatric predatory sea stars. Marine Biology Journals, 154: 1077-1084. Accessed March 20, 2012 at http://www.springerlink.com/content/jj25k262m1647w86/.

Pearse, J. 1963. The Reproductive Cycle of the Antarctic Asteroid, Odontaster validus Koehler. XVI International Congress of Zoology, 1: 111. Accessed March 28, 2012 at http://books.google.co.uk/books?id=o0IrAAAAYAAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false.

Stanwell-Smith, D., A. Clarke. 1998. Seasonality of reproduction in the cushion star Odontaster validus at Signy Island, Antarctica. Marine Biology Journals, 131/3: 479-487. Accessed March 20, 2012 at http://www.springerlink.com/content/b06nal3juljp73eu/.