Broad disc with five or more long arms. The aboral skeleton is meshlike; the plates bear pseudopaxillae. The marginal pseudopaxillae are larger than the aborals. Oral intermediates are present. The adambulacral spines consist of two series at right angles to each other. The mouth plates are prominent. No pedicellariae.
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Crossaster papposus is a colourful sea star with 8 to 16 arms, usually 10 or 11, up to 8.5 cm long. Its colour is varies greatly: it may be solid purple or red, but it usually has a concentric pattern of bright red, orange, white or yellow on its spiny aboral surface. The ratio of arm to disc ranges from 1.8 to 2.7. The aboral pseudopaxillae are widely spaced and bear up to 50 slender spinelets. The marginals consist of a single series of prominent pseudopaxillae. The oral interradial area has up to about 25 pseudopaxillae. The adambulacrals usually have 3 to 5 furrow spinelets with a transverse comb of 5 to 9 slightly longer stouter spinelets on the oral surface. The mouth plates have 8 to 10 marginal spines with 2 to 4 suborals.
Crossaster papposus might be mistaken for a juvenile Pycnopodia helianthoides. But P. helianthoides is generally much larger, has more arms, differs in the detail of the aboral surface, adambulacral and mouth-plate spines and ha
In British Columbia, Crossaster papposus eats the sea pen Ptilosarcus, sea slugs (opisthobranchs), bryozoa, sea squirts and bivalves. It may also attack other sea stars (such as Evasterias troschelli). In Scotland, C. papposus breeds from March to April; each sea star may spawn several times at intervals of two to ten days, shedding more than 2000 eggs at a time, 6000 altogether. The eggs (0.8 mm) are reddish-brown to clay colour and are fertilized externally. The lecithotrophic larva settles to the bottom after 18 days and attaches by a sucker. The mouth forms after about 38 days. Juveniles are often found among the tubes of the polychaete worm Phyllochaetopterus. C. papposus moves at a rate of 60 to 70 cm per minute. A well-fed Rose Star grew from 40 mm to 90 mm in one year. Richard Carlson at the Auke Bay Lab near Juneau studied a population for 17 years. He found that growth rates were quite slow, with individuals achieving a maximum diameter of 30 ern in about 10 years. Their principal prey item was the scallop Chlamys rubida. Crossaster papposus can live for at least 20 years. Mortality rates were low and recruitment of young was infrequent in that population. The scale worm Arctonoe vittata is commensal on C. papposus.
Circumpolar. In the Pacific, to Washington and the Sea of Okhotsk; in the Atlantic, to 40°N latitude on the American side, and to Scandinavia and the British Isles on the northern European coast. Found from the intertidal zone to 1200 metres deep on soft mud, gravel, sand, pebbles or rock. Common in this region (the area from Glacier Bay to Puget Sound to a depth to 200 metres).
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
22/11/2019 1:12:24 PM]
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