Plectaster decanus (Müller & Troschel, 1843)

Identification:

Five arms rounded in cross-section, tapering to a narrow, rounded point. Aboral surface with a hexagonal network of granular ridges dividing variously coloured areas, including orange, purple and red, in a mosaic effect.

Distribution:

Temperate inshore and continental shelf areas from Julian Rocks, Byron Bay, NSW, south to Tasmania and west to Yanchep, WA. Depth range 0-200 m.

Australian Museum registration database records for the Sydney region:

3.2 km offshore between Long Reef & Dee Why; Port Jackson (Shark Island; Taylors Bay; off Georges Head); Botany Bay (Bare Island). Depth range 20-27 m.

Habitat:

Sheltered and moderately exposed reef.

Taxonomic information - synonyms and type material:

Echinaster decanus Müller, & Troschel, 1843: 114.
Type data: syntypes ZMB 751-753.
Type locality: southwestern Australia.

Links for further information:

Atlas of Living Australia

World Register of Marine Species

Remarks:

Rowe & Albertson (1988) comment that because the furrow spines occur in a comb-shaped row along the adradial edge of the ambulacral plates, the genus Plectaster Sladen, 1889 does not belong in the family Echinasteridae, however, they decline to reassign the genus.

Readily found at ‘Jolong Reef’ approximately 700m north east of Cape Banks at ~20m depth, November 2008.

Additional references:

Clark (1946); Rowe & Albertson (1988); Edgar (1997).