E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Solaster dawsoni Verrill, 1880
Morning Sun Star
Family: Solasteridae
Photo of species

© Neil McDaniel  Email the photographer   (Photo ID #15917)

E-Fauna BC Static Map
Distribution of Solaster dawsoni in British Columbia
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Introduction


Family Description:

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.

Species Information


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Solaster dawsoni is usually a homogeneous brown, with an evenly textured aboral surface. It has 11 or 12 arms (sometimes 8 to 13) and can grow up to 20 cm in radius. The ratio of arm to disc is from 2.5 to 3.4. Its body is occasionally red, orange, or mottled brown and beige. When viewed from above, the inferomarginals appear as serrated edges of the arms. The aboral pseudopaxillae are round and flat-topped with 30 tiny spine lets on the perimeter and up to 15 central spinelets. The superomarginals are similar in shape but larger. The oblong inferomarginals are three to four times wider than their length. The oral interradial area is small (only 20 to 25 plates) when compared with the three other species in this genus. The adambulacrals have a furrow series of 3 or 4 long, tapering spines; the oral surface bears a straight transverse series of 3 to 6 long spines that stand about twice as high as the spines on the adjoining inferomarginals and slightly higher than the furrow series. Each pair of mouth plates is rather broad and shovel-like with 9 to 11 marginal spines, the apical spine being largest. Spines on the oral surface can vary, from 1 or 2 suborals to a double row of 5 to 10 spines.

Similar Species

The living colour and body shape of the four species of Solaster in British Columbia are fairly distinctive, but if specimens are dried you may need to consult the descriptions of the adambulacral spines.

Biology


Solaster dawsoni is carnivorous. In 36 of 55 feeding observations in Puget Sound, it preyed on S. stimpsoni and consumed the sea star in an average of 4.5 days. This predator ate about 17 S. stimpsoni per year. In the Strait of Georgia, Dermasterias imbricata seems to be the prey of choice based on diver observations. S. dawsoni also attacks its own species, but its success rate is low because of a well-developed escape response. S. dawsoni bends its arms back and pushes the attacker off while rapidly moving away (10 cm/min.). This sea star also preys upon Crossaster papposus, Leptasterias hexactis, Mediaster aequalis, Evasterias troschelii, Henricia leviuscula, Asterina miniata, small Pisaster ochraceus and Pycnopodia helianthoides. When attacking, S. dawsoni can reach a speed of 12 cm per minute. In a Bodega Bay study, D. imbricata, Pisaster brevispinus and large P. ochraceus appeared to avoid predation; the latter two used their pedicellaria to ward off S. dawsoni. The strongest escape responses are shown by A. miniata, H. leviuscula, L. hexactis and Pycnopodia helianthoides; and the California Sea Cucumber (Parastichopus califomicus) swims away when contacted.

S. dawsoni breeds from late February to early March. Large buoyant eggs (0.94-1.05 mm) undergo total and equal cleavage to a planktonic lecithotrophic larva with three brachiolarian arms. Settlement occurs 8-10 days after fertilization and metamorphosis 40-50 days after. The juvenile has five arms initially and adds the remaining arms in sequence between the first and fifth. I observed three specimens spawning on April 13 1977 near Victoria. Juveniles have been reported to be quite common among tubes of the polychaete Phyllochaetopterus. S. dawsoni has two commensal scale worms: Arctonoe fragilis and A. vittata.

Distribution

Distribution

From Point Franklin on the north side of Alaska to Monterey Bay, California, and on the Asiatic side to the Yellow Sea. Found from the intertidal zone to 420 metres deep on rocky substrates. Uncommon.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
UnlistedUnlistedUnlistedUnlisted
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. 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: 2021-11-28 8:52:53 PM]
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