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Patiriella gunnii (Family Asterinidae)

Six-armed Seastar

Distribution:

The Six-armed Seastar ranges from Collaroy, near Sydney, New South Wales, around Australia's southern shores (excluding southern and western Tasmania) to Dongara in south-western Western Australia. Clark considers that this species is more common in southwestern Australia. (NSW, VIC, SA, TAS, WA)

Features:

The Six-armed Seastar is a thin, flat-bodied seastar usually with six arms, resembling a hexagon, with its short arms not protruding beyond the skirt. Occasionally it has 5 to 8 arms, or may be circular in form. Grey looked at 539 specimens and found that 90% had six rays, 6.5% had seven, while 2.5% had eight and only 1% had five rays. The spines of the actinal plates are more or less cylindrical and bluntly pointed. The actinal intermediate plates occur usually with 2 spines. It grows to a diameter of 25-40 mm.

Its dorsal colour pattern is mottled and quite varied. It is as colourful as the Common Eight-armed Seastar, Patiriella calcar, but is usually more dark and dull in colouration. Its colours include varied greens and browns, orange, pink, red, blue, mauve, with little yellow or white. The ventral surface is pale in colour.

Ecology/Way of Life:

It occurs at low tide levels and below to 30 metres depth, sheltering under rocks and in crevices where it feeds on encrusting organisms. It appears to prefer the lowest tide regions.

Interaction with Humans/Threats:

If you look at the photographs in Shepherd and Thomas (p. 413) Fig. 10.7 (a) and (b), they look nothing like the photograph in Edgar (p. 346) and their text descriptions are not similar.

Other Comments:

Gray first described this species as Asterina gunni in 1840. Verrill renamed it Patiriella gunni in 1913.

Further Reading:

Davey, K. (1998). A Photographic Guide to Seashore Life of Australia. p. 130, New Holland Press.

Clark, H.L. (1946). The Echinoderm Fauna of Australia: Its composition and origin. Carnegie Institution of Washington. Publication 566. p. 135.

Edgar, G.J. (1997). Australian Marine Life: the plants and animals of temperate waters. p. 345, Reed.

Marine Research Group of Victoria. (1984). Coastal Invertebrates of Victoria: an atlas of selected species. p. 136, Museum of Victoria.

Shepherd, S.A. and Thomas, I.M. (1989). Marine Invertebrates of Southern Australia. pt. I. p.412, South Aust. Govt. Press.

Acknowledgments:

Text, map and photograph by Keith Davey.

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