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Overview

Distribution

Red sea stars are found in the Antarctic region, most prevalently in the waters surrounding the Antarctic continent and islands.

Biogeographic Regions: antarctica (Native )

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O. validus is distributed throughout Antarctica and the Antarctic Peninsula, South Shetland Islands, South Orkney Islands, South Sandwich Islands, South Georgia Island, Shag Rocks, Marion and Prince Edward Islands, and Bouvet Island at depths from 0 to 914 meters (Clark, 1962; Clark, 1963; Bernasconi, 1970)
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Physical Description

Morphology

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.

Range length: 2 to 11 cm.

Average length: 7 cm.

Other Physical Features: ectothermic ; radial symmetry

Sexual Dimorphism: sexes alike

  • 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.
  • 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/.
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Ecology

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).

Range depth: 0 to 914 m.

Habitat Regions: polar ; saltwater or marine

Aquatic Biomes: benthic ; coastal

Other Habitat Features: intertidal or littoral

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Depth range based on 119 specimens in 1 taxon.
Water temperature and chemistry ranges based on 78 samples.

Environmental ranges
  Depth range (m): 0 - 2902
  Temperature range (°C): -1.951 - 12.221
  Nitrate (umol/L): 6.335 - 36.002
  Salinity (PPS): 33.660 - 35.088
  Oxygen (ml/l): 4.036 - 8.053
  Phosphate (umol/l): 0.761 - 2.502
  Silicate (umol/l): 2.840 - 135.683

Graphical representation

Depth range (m): 0 - 2902

Temperature range (°C): -1.951 - 12.221

Nitrate (umol/L): 6.335 - 36.002

Salinity (PPS): 33.660 - 35.088

Oxygen (ml/l): 4.036 - 8.053

Phosphate (umol/l): 0.761 - 2.502

Silicate (umol/l): 2.840 - 135.683
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Dispersal

The starfish O. validus has a demersal feeding larva with a brief pelagic phase to allow the dispersion without exposing the larvae to the hazardous surface waters.
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Trophic Strategy

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.

Animal Foods: carrion ; mollusks; aquatic crustaceans; echinoderms; cnidarians

Plant Foods: algae; phytoplankton

Other Foods: detritus ; dung

Primary Diet: carnivore (Eats non-insect arthropods, Molluscivore , Eats other marine invertebrates, Scavenger ); herbivore (Algivore); omnivore

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O. validus is an omnivorous. Its diet includes the bivalves Limatula hodgsoni and Laternula elliptica, the sponges Rossella racovitzae, Rossella nuda, Scolymastra joubini, Tetilla leptoderma, and Homaxinella balfourensis, the hydroid Halecium arboreum, the sea star Acodontaster conspicuus, the sea urchin Sterechinus neumayeri, the isopod Glyptonotus antarcticus, bryozoans, suspended matter, animal dtritus, red algae, amphipods, crustacean nauplii larvae, ostracods, shrimp, ectoprocts, diatoms, and seal feces (Conlan et al., 2006).
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Associations

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.

Ecosystem Impact: keystone species

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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.

Known Predators:

  • Desmonema glaciale (Family Cyaneidae, Phylum Cnidaria)
  • Macroptychaster accrescens (Order Paxillosida, Class Asteroidea)
  • Urticinopsis antarctica (Order Actiniaria, Class Anthozoa)

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O. validus is prey of the sea anemone Urticinopsis antarcticus and the sea star Macroptycaster accrescens (Conlan et al., 2006).
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General Ecology

Odontaster validus is the commonest and most abundant sea star inhabiting the shallow environment around the Antarctic continent (Dearborn, 1977; McClintock et al., 1988).
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Life History and Behavior

Behavior

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.

Communication Channels: chemical

Perception Channels: chemical

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Life Cycle

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.

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The larval development of Odontaster is extremely slow; it remains in the bipinnaria larval stage for about 2 months in the laboratory condition (Chia, 1970). In McMurdo Sound the period of spawning is from June to mid October (Pearse et al., 1986; Bosch & Pearse, 1990).
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Life Expectancy

The lifespan of this sea star is not currently known, although there is evidence that they can live up to 100 years.

Range lifespan

Status: wild:
100 (high) hours.

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O. validus may live for about 100 years (Pearse, 1969).
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Reproduction

As with most echinoderms, red sea stars reproduce via broadcast spawning and external fertilization.

Mating System: polygynandrous (promiscuous)

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.

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.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); broadcast (group) spawning

There is currently no evidence that red sea stars exhibit any parental investment.

Parental Investment: no parental involvement

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Growth

Odontaster validus has a late sexual maturity and slow rate of growth. This starfish may grow only 1-2 g year-1, takes 3-6 years to reach sexual maturity (Pearse, 1969).
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Odontaster validus

The following is a representative barcode sequence, the centroid of all available sequences for this species.


No available public DNA sequences.

Download FASTA File
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Statistics of barcoding coverage: Odontaster validus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

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.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

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Relevance to Humans and Ecosystems

Benefits

There are no known negative economic impacts of this species.

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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.

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Wikipedia

Odontaster validus

Odontaster validus is a species of starfish in the family Odontasteridae. Its range includes the Southern Ocean and the seas around the mainland and islands of Antarctica.

Description[edit]

Odontaster validus can grow to about 10 cm (4 in) in diameter. The disc is broad, thick and cushion-like, creased by interambulacral grooves. There is a large madreporite near the centre and the surface is covered in small granulations organised in radial rows. The five short arms are wide at the base tapering sharply and the tip is often raised off the substrate showing the pale coloured tube feet beneath. The colour of the upper or aboral surface is plain red while the underside is pink.[1]

Distribution[edit]

Odontaster validus is the commonest starfish found in Antarctica. Its range includes the Antarctic Peninsula, the South Shetland Islands, the South Orkney Islands, South Georgia and the South Sandwich Islands, the Shag Rocks, the Prince Edward Islands and Bouvet Island. It is found at depths down to 900 metres.[2]

Biology[edit]

Odontaster validus is an omivorous scavenger and consumes anything it finds including carrion, detritus, the faeces of seals, red algae, bivalve shells, sponges, hydroids, other starfish, sea urchins, isopods, bryozoans, amphipods, crustacean larvae, ostracods, shrimps and diatoms.[2] They have been observed aggregating on banks of mussels that have been exposed and damaged and on injured starfish, Acodontaster conspicuus.[3] In turn, they are preyed upon by sea anemones and other species of starfish.[2] It is an ecologically important species because of its consumption of benthic larvae and the control it exerts on the starfish Acodontaster conspicuus and the nudibranch Doris spp. which themselves tend to limit the growth of sponges that tend to dominate the seabed.[4]

Odontaster validus takes 3 to 6 years to reach maturity but may live for 100 years.[2] This is a consequence of the animal being cold-blooded, the harsh environmental conditions in which it lives and the low metabolic rate that ensues.[2] In McMurdo Sound, where it has been extensively studied, the water temperature is about −1.8 °C (28.8 °F).[5] The initiation of oogenesis occurs from August to February and the eggs take about 18 months to mature. Spawning takes place between May and September and may be linked to seasonal changes in light levels, sunrise taking place in McMurdo Sound in August.[5] The larval development is also slow with the first, bipinnaria, stage lasting 2 months. The larvae remain near the seabed during this time but become pelagic for up to 6 months as brachiolaria larvae which allows them to disperse widely. They then return to the seabed, undergo metamorphosis and develop into juvenile starfish.[2]

Research[edit]

Odontaster validus does not attack members of its own species but can attack starfish of other species. This seems to be due to chemoreceptors which can identify conspecifics by their odour.[6] Starfish often converge on food sources and a study was undertaken to examine how they do this. It was found that food-deprived individual Odontaster validus could distinguish between the odours emitted by satiated and by starved starfish of the same species. They were strongly attracted to the former and took little notice of the latter.[6]

Odontaster validus is much less sensitive to higher water temperatures than the other Antarctic marine species on which it feeds which mostly find temperatures above 3 °C lethal. Even when not killed at higher temperatures, many organisms cease to feed, may remain immobile or fail to reproduce and others started metabolising anaerobically.[7] A study was undertaken to examine the implications of this for the Antarctic marine environment if water temperatures rise as a result of global warming.[7]

Another research study examined the parameters required for successful fertilisation of the eggs of Odontaster validus compared to similar temperate water sea stars. It was found that a density of sperm of 105 sperm per millilitre was sufficient to cause a high proportion of eggs to be fertilised and that this was at least ten times the density required by comparable species in less harsh environments. The sperm still retained a minimal fertilisation ability after 24 hours but had a narrow tolerance to variations in water temperature.[8]

References[edit]

  1. ^ a b c Mah, Christopher (2010). "Odontaster validus, Koehler, 1906". World Register of Marine Species. Retrieved 2012-02-15. 
  2. ^ a b c d e f Odontaster validus; Koehler, 1906 Antarctic Field Guide. Retrieved 2011-11-26.
  3. ^ Kidawa, Anna (2005). "Behavioural and metabolic responses of the Antarctic sea star Odontaster validus to food stimuli of different concentration". Polar Biology 28 (6): 449–455. doi:10.1007/s00300-004-0705-2. 
  4. ^ Alexis M. Janosik, Alexis M.; A.R. Mahon; K.H. Halanych (2011). "Evolutionary history of Southern Ocean Odontaster sea star species (Odontasteridae; Asteroidea)". Polar Biology 34 (4): 575–586. doi:10.1007/s00300-010-0916-7. 
  5. ^ a b Pearse, J. S. (1963). The reproductive cycle of the Antarctic asteroid Odontaster validus Koehler. Proceedings of the International Congress of Zoology. p. 111. 
  6. ^ a b Kidawa, Anna (2001). "Antarctic starfish, Odontaster validus , distinguish between fed and starved conspecifics". Polar Biology 24 (6): 408–410. doi:10.1007/s003000100229. Retrieved 2011-11-26. 
  7. ^ a b Peck, Lloyd S, Karen E Webb, Andrew Miller, Melody S Clark, Tim Hill (2008). "Temperature limits to activity, feeding and metabolism in the Antarctic starfish Odontaster validus". Marine Ecology Progress Series 358: 181–189. doi:10.3554/meps07336. Retrieved 2011-11-26. 
  8. ^ Grange, Laura J.; P.A. Tyler; L.S. Peck (2011). "Fertilization success of the circumpolar Antarctic seastar Odontaster validus (Koehler, 1906): a diver-collected study". Proceedings of the American Academy of Underwater Sciences, 30th Scientific Symposium: 140–150. ISBN 978-0-9800423-5-1. 
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