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Evasterias troschelii - False ochre star
Geographic range:
Alaska to Big Sur, California
Key features:
Long, tapered rays and no pentagram of spines on the medial disk, as might be seen on the more common ochre star Pisaster ochraceus.
Similar species:
Pisaster ochraceus -- Ochre star
Habitat(s):
bay (rocky shore), exposed rocky shore, kelp forest, protected rocky shore
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Primary common name:
False ochre star |
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ITIS code:
157224 |
Synonymous name(s):
-- |
General grouping:
Sea stars, urchins, cucumbers, sand dollars, brittle stars |
| Geographic Range |
Range description:
Siberia, northern Alaska to Big Sur, Calfiornia. Most field guides indicate the southern range ends in Monterey Bay, but that is not true. Recent expeditions to the Big Sur coast found Evasterias troschelii on multiple, separate occasions and in different locations. |
Northern latitude extent:
-- |
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Southern latitude extent:
-- |
East longitude extent:
-- |
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West longitude extent:
-- |
| Intertidal Height |
Lowest intertidal height:
meters OR -2 feet |
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Highest intertidal height:
meters OR 0 feet |
Intertidal height notes:
Rarely found in the intertidal in central California, but more common intertidally in the northern part of its geographic range. |
| Subtidal Depth Range |
Minimum depth:
5 meters OR 0 feet |
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Maximum depth:
75 meters OR feet |
Subtidal depth notes:
In central California divers can find this rare species at depths <25 m. |
| Habitats |
Habitat(s):
bay (rocky shore), exposed rocky shore, kelp forest, protected rocky shore |
Habitat notes:
Evasterias troschelii has been photographed along the Big Sur coast at multiple locations (e.g., Bixby Bridge, Grimes Point, Willow Creek) during surveys of nearshore kelp forests. In each case it was found on rocky reef. |
| Abundance |
Relative abundance:
Rare. |
| Species Description |
General description:
Evasterias troschelii is called the false ochre star because of its close resemblance to the ochre star Pisaster ochraceus, which is commonly found in the intertidal and shallow subtidal of central California. Its general appearance is usually drab, except for bright orange morphs. The aboral patterning consists of irregular reticulations, lacking the typical pentagram seen on the central disc of Pisaster ochraceus.
Coloring is variable, ranging from bright orange to drab brown and gray. The long rays are tapered, and the normal number is five. |
Distinctive features:
Elongate rays and low dorsal spines. It can be distinguished from the more common ochre star Pisaster ochraceus by the elongate and tapered rays. |
Size:
Disk diameter: up to 60 cm |
| Natural History |
General natural history:
Little is known about Evasterias troschelii along the central coast of California. The Big Sur coast serves as the southern range limit for this species, and it is rarely seen by divers or in the intertidal. It is more abundant in the northern part of its range, including Oregon, Washington and Alaska. |
Predator(s):
Like other large sea stars, there are relatively few predators, although it is possible that some sea gulls prey on the stars in the intertidal, and sea otters may consume rays when the gonads are ripe. |
Prey:
Evasterias troschelii feeds on mussels and other bivalves on rocky reefs, as well as gastropods, barnacles, tunicates and even brachiopods. It also likely scavenges when carcasses are present. |
| Feeding behavior |
Feeding behavior(s):
Carnivore, Scavenger |
Feeding behavior notes:
As is true with most sea stars, tube feet are used to hold prey in place, forcing shells open via steady exertion. The stomach pouches can be everted to digest the prey in situ. |
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| January - December |
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Reproduction:
Unknown. |
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Cordell Bank National Marine Sanctuary:
-- |
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Gulf of Farallones National Marine Sanctuary:
-- |
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Monterey Bay National Marine Sanctuary:
None. |
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Listing Status:
-- |
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Monitoring Trends:
-- |
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References:
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Carlton, J.T. 2007.
The Light and Smith Manual, 4th edition
Intertidal Invertebrates from Central California to Oregon
University of California Press. 1001 p.
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| Gotshall, D. 2005. Guide to marine invertebrates : Alaska to Baja California. Sea Challengers, Monterey, CA. 117 p. |
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| Lamb, A. and B. P. Hanby. 2005. Marine life of the Pacific Northwest. Harbour Publishing. 398 p. |
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| Morris, R.H., D.P Abbott, and E.C. Haderlie. 1980. Intertidal Invertebrates of California. Stanford University Press, Stanford, California. 690 p. |
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Data supplied by SIMoN Sanctuary Integrated Monitoring Network
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