page_title: Marthasterias
section_title: Ecology
hierarchical_section_title: Marthasterias / Ecology
caption_attribution_description: Français&#160;: Marthasteria glacialis (Linnaeus, 1758) - Banyuls-sur-Mer&#160;: 07/91
context_page_description: 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.
context_section_description: Like other starfish in the family Asteriidae, Marthasterias glacialis is a predator and feeds mostly on bivalve molluscs and other invertebrates. 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. 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.
  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.
caption: Detail of tip of arm showing tube feet extended
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