Biodiversity & Conservation

A cushion star - Asterina phylactica

Asterina phylactica

Image David Fenwick - Close-up of the aboral (top) side of a cushion star found in an intertidal rockpool. Image width ca XX cm
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Distribution map

Asterina phylactica recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

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Asterina phylactica is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Echinodermata Starfish, brittlestars, sea urchins & sea cucumbers
Class Stelleroidea Starfish, sea stars, cushion stars and brittlestars
Authority Emson & Crump, 1979
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland Found off the south-west coasts of the British Isles, but occurs as far north as the west coasts of Scotland and has been recorded off north-west Ireland.
Habitat information icon Habitat information Asterina phylactica is a benthic species often found in intertidal rock pools but may be found sublittorally down to a depth of 18 m.
Text page icon Description

The cushion star, Asterina phylactica, has the star-shaped body typical of starfish with five equal length arms originating at a central disc. The lower surface of the central disc bears the mouth. A deep furrow runs from the mouth to the end of each arm. In each furrow are two rows of tube feet. Like similar starfish species, Asterina phylactica, has inconspicuous marginal plates, papulae on the all surfaces and a sharp edge between the upper and lower surfaces.

Asterina phylactica has a flattened body only reaching 1.5 cm in diameter with small compact arms. It can be distinguished from Asterina gibbosa and similar species by its much smaller size, having very few ventral mouth plates and no radial thickenings. It has a grey-green upper surface with a conspicuous dark star-shape in the centre. It is pale underneath.
Identifying features
  • Inconspicuous marginal plates.
  • Papulae on upper and lower surfaces.
  • No crossed pedicellariae.
  • Two rows of tube feet.
  • Sharp edge between the upper and lower surfaces.
  • Dark star shape at the centre of the upper surface.
Additional information icon Additional information Asterina phylactica has an unusual reproductive strategy. Individuals are simultaneous hermaphrodites, and during breeding season will form small aggregations of up to 10 individuals to ensure cross breeding. They then brood the eggs by laying over the top them, remaining with the breeding aggregation until the eggs hatch.

This review can be cited as follows:

Morvan Barnes 2009. Asterina phylactica. A cushion star. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 20/06/2013]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=2660>