This seastar has a small
disk and 5 long rays
(total diameter is 5 to 7.6 times central disk diameter) which are not
bordered by obvious marginal plates (photo).
The rays usually narrow as they attach to the central disk and are
at a point slightly out from the central disk.
spines (less than 2 mm high, irregular pattern) and pedicellariae
make the aboral surface rough (photo).
Clusters of pedicellariae are especially visible near the ambulacral
grooves, and are usually in clumps at the bases of spines.
crossed and straight pedicellariae. Color highly
gray, blue-gray, greenish, brown, orange, reddish (especially along the
Oregon and California coast), pale purple; frequently margins of rays
a different shade than aboral surface. Radius up to 28 cm.
Common name(s): Mottled star.
ochre sea star; Troschell's
|Evasterias troschelii subtidal
Sares Head, WA. Ruler
is 6 inches
|(Photo by: Dave
How to Distinguish
Similar Species: Small
individuals look somewhat like a Pisaster
ochraceous or P. brevispinus,
but this species has longer rays in proportion to its central disk and
the rays narrow before they meet the central disk, and the aboral
are not arranged in a clustering network.
to Monterey Bay, CA; Kamchatka. Uncommon south of Puget
This is the most abundant large, intertidal star in the Juneau area.
Depth Range: Low
intertidal and subtidal
to 70 m. Mostly subtidal in the Rosario area (abundant in
rocks and cobbles (occasionally
sand); sometimes on docks and pilings. More abundant
in protected areas than along the open coast.
Feeds on a variety
of animals--bivalves, limpets, snails, brachiopods, barnacles, and
Can evert its stomach (up to a distance equal to half the length of a
Several limpets exhibit escape responses from this species.
a symbiotic scaleworm (Arctonoe fragilis) living in
groove or on the body surface (photo).
In Alaska one can often find the young of the Alaska King Crab (Paralithodes
camtschaticus) nestled between the rays of this
include gulls (especially in Alaska where they are common
and attacks by the rose star Crossaster
papposus and by Alaska King Crab Paralithodes
have been observed. Tolerant of reduced salinities down to 20
In Burrard Inlet, BC, Canada, this species became more abundant in the intertidal after seastar wasting disease while Pisaster ochraceus became less abundant. This species can be infected but seems less susceptible to infection by seastar wasting disease than is P. ochraceus (Kay et al., 2019).
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and Fairbanks, 1966
and Carlton, 1975
and Laurent, 1979
et al., 1980
and O'Clair, 1998
Kay, S.W.C., A.M. Gehman, and C.D.G. Harley, 2019. Reciprocal abundance shifts of the intertidal sea stars, Evasterias troschelii and Pisaster ochraceus,
following sea star wasting disease. Proceedings of the Royal Society of
London Part B: Biological Sciences 286:1901 p doi:
Mauzey, K.P., C. Birkeland, and P.K. Dayton, 1968. Feeding
of asteroids and escape responses of their prey in the Puget Sound
Ecology 49: 603-619
General Notes and
Observations: Locations, abundances,
This species is commonly found off Sares Head.
Another individual, with three symbiotic Arctonoe
attached. Ruler is 1 foot (30 cm). Photo by Dave
The aboral surface has large spines (1-2 mm long) arranged
Smaller spines and pedicellariae are arranged in circles around the
Photo by Dave Cowles, July 2005
There are no large marginal plates on the rays. The stomach
be everted, as it was shortly before this photo. Photo by
This view of the aboral side of the central disk shows the networklike
system of spiny ossicles. Photo by Dave Cowles, July 2008
The scaleworm Arctonoe fragilis is a common
symbiont on this
and other seastar species. Photo by Dave Cowles July 2005
This individual, with individual rays from 25-30 cm long, was collected
by otter trawl from 75 m depth in San Juan Channel.
Notice that it has lost one ray which it is beginning to
Photo by Dave Cowles, July 2008
This individual, photographed under the Keystone ferry
drawbridge, is purple in color. Photo by Dave Cowles, July
Authors and Editors of Page:
Dave Cowles (2005): Created original page