Marthasterias

Marthasterias is a genus of starfish in the family Asteriidae. It is monotypic and the only species in the genus is Marthasterias glacialis, commonly known as the spiny starfish. It is native to the eastern Atlantic Ocean.

Marthasterias
Marthasterias glacialis
Scientific classification
Kingdom:
Animalia
Phylum:
Echinodermata
Class:
Asteroidea
Order:
Forcipulatida
Family:
Asteriidae
Genus:
Marthasterias

Jullien, 1878[1]
Species:
M. glacialis
Binomial name
Marthasterias glacialis
(Linnaeus, 1758)[2]

Description

Marthasterias glacialis is a fairly large starfish with a small central disc and five slender, tapering arms. Each arm has three longitudinal rows of conical, whitish spines, usually with purple tips, each surrounded by a wreath of pedicellariae. The background colour is variable and may be brownish or greenish-grey, tinged with yellow or red and sometimes with purple at the tips of the arms. This species can grow to 70 cm (28 in) but a more usual size is 25 to 30 cm (10 to 12 in). It is sometimes confused with the northern starfish Leptasterias muelleri.[3]

Distribution and habitat

Marthasterias glacialis is native to the eastern Atlantic Ocean. Its range extends from Iceland to the Azores and the Mediterranean Sea, and it has been observed in South Africa.[4] Around the British Isles it is limited to the western side of Scotland, Wales, the western part of southern England and most of Ireland. Its depth range is subtidal down to about 200 m (656 ft) and it is found on both sheltered muddy substrates and on rocks.[3]

Ecology
Detail of tip of arm showing tube feet extended

Like other starfish in the family Asteriidae, Marthasterias glacialis is a predator and feeds mostly on bivalve molluscs and other invertebrates.[5] It has been found that secondary metabolites known as saponins, found within the starfish's tissues, have a dramatic effect on the whelk Buccinum undatum. At low concentrations they cause the mollusc to withdraw from the vicinity of the starfish and at higher concentrations they cause convulsions in the mollusc's musculature.[6] The sea urchins Strongylocentrotus droebachiensis and Psammechinus miliaris are also affected by the chemicals. S. droebachiensis flees but P. miliaris has toxic pedicellariae and is able to defend itself.[7]

The reproductive biology of this starfish has been little studied but off the coast of Ireland, individuals gather together in very shallow water in July and August. A few days later, on a warm afternoon, they have been observed to arch their bodies and release spawn into the sea. A rise in the water temperature seems to have triggered the spawning. Male starfish as small as 2.5 cm (1 in) were observed to spawn, and females of at least 9 cm (3.5 in) diameter.[4]

gollark: Exactly.
gollark: And "against the 6-year-old T&C".
gollark: But under moderator logic, that's "harrasment".
gollark: Yes, exactly.
gollark: Doesn't flow like the original, but you know.

References
  1. Mah, Christopher (2014). "Marthasterias Jullien, 1878". WoRMS. World Register of Marine Species. Retrieved 2014-02-18.
  2. Mah, Christopher (2014). "Marthasterias glacialis (Linnaeus, 1758)". WoRMS. World Register of Marine Species. Retrieved 2014-02-18.
  3. "Spiny starfish - Marthasterias glacialis". Marine Life Information Network. Retrieved 2014-02-19.
  4. Minchin, D. (1987). "Sea-water temperature and spawning behaviour in the seastar Marthasterias glacialis". Marine Biology. 95 (1): 139–143. doi:10.1007/BF00447495.
  5. Barrett, John; Yonge, Charles Maurice (1958). Collins Pocket Guide to the Sea Shore. Collins & Co. p. 178. ISBN 978-0-00-219321-4.
  6. Mackie, A. M.; Lasker, R.; Grant, P. T. (1968). "Avoidance reactions of a mollusc Buccinum undatum to saponin-like surface-active substances in extracts of the starfish Asterias rubens and Marthasterias glacialis". Comparative Biochemistry and Physiology. 26 (2): 415–428. doi:10.1016/0010-406X(68)90635-X.
  7. Jensen, Margit (1966). "The response of two sea-urchins to the sea-star Marthasterias glacialis (L.) and other stimuli". Ophelia. 3 (1): 209–219. doi:10.1080/00785326.1966.10409643.
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