Odontaster validus

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Odontaster validus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Echinodermata
Class: Asteroidea
Order: Valvatida
Family: Odontasteridae
Genus: Odontaster
Species:
O. validus
Binomial name
Odontaster validus
Koehler, 1906 [1]
Synonyms[1]
  • Cycethra verrucosa Bell, 1908
  • Gnathaster tenuis (Koehler, 1920)
  • Gnathaster validus Koehler, 1920
  • Odontaster tenuis Koehler, 1906

Odontaster validus is a

sea star in the family Odontasteridae. Its range includes the Southern Ocean and the seas around the mainland and islands of Antarctica
.

Description

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

Odontaster validus is the most common sea star found in Antarctica. Its

Shag Rocks, the Prince Edward Islands and Bouvet Island. It is found at depths down to 900 metres.[2]

Biology

Odontaster validus in Tokyo Sea Life Park

Odontaster validus is an

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 sea star.[2]

Research

Odontaster validus does not attack members of its own species but can attack sea star of other species. This seems to be due to

chemoreceptors which can identify conspecifics by their odour.[6] Sea star 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 sea star 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.

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

  1. ^ a b c Mah, Christopher (2010). "Odontaster validus, Koehler, 1906". WoRMS. 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. S2CID 42760159. Archived from the original
    on 2012-09-06.
  4. S2CID 52850808
    .
  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. ^
    S2CID 837982. Archived from the original
    on 2013-01-28. Retrieved 2011-11-26.
  7. ^
    doi:10.3354/meps07336
    . Retrieved 2011-11-26.
  8. ISBN 978-0-9800423-5-1
    .
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