How to Distinguish from Similar Species: This seastar is larger and has more rays than any other seastar in our area. Small individuals could be confused with Solaster dawsoni or Crossaster papposus, but both of those species have 16 or less rays, have no pedicellariae, and are not as markedly limp as Pycnopodia is.. S. dawsoni also does not have the prominent projecting spines, and C. papposus' spines are not extra prominent along the margins of the rays as they are in this species.
Geographical Range: Unalaska Island, Alaska to Baja California; uncommon south of Monterey Bay
Depth Range: Low intertidal to 435 m. Nearly always subtidal.
Habitat: Mostly subtidal, rocky, gravelly, or sandy bottoms.
Biology/Natural History: This species is a voracious subtidal predator, feeding on bivalves, snails, chitons, urchins, other asteroids, sea cucumbers, sand dollars, and crabs (in other words, just about anything it wants!). It will also scavenge dead animals. It may be the largest and fastest seastar in the world. It can move up to 3 meters per minute, and has been known to travel at least 3 km. It has over 15,000 tube feet. Tiny, newly metamorphosed juveniles of this species have only 5 rays but rays are added as the individual grows. Has very prominent spines and (crossed) pedicellariae, plus purple papulae. Loss of rays upon handling seems to be due to autotomy. In Puget Sound this species excavates butter clams (Saxidomus gigantea) by picking up sediment particles over the clam, passing them out to the ends of the rays, and dropping them. Often eat urchins such as Strongylocentrotus purpuratus, whose spines may pierce through from the stomach to the aboral surface. Can evert its stomach but more often swallows its prey whole. Predators include Alaska King crab and some large Cancer crabs. Individuals are agressive toward one another (and to almost any other seastar). Spawns March to July (some also in winter); has fertilizable eggs at least from December to June. May stand on the tips of their rays while spawning. Pelagic larvae metamorphose to benthic, 5-rayed juveniles at 9-10 weeks.
This species has a large, fleshy body with an only loosely articulated skeleton, and relies on fluid pressure to maintain its body form. It appears to rely more heavily on fluid uptake through the surface than on uptake through the madreporite. Its perivisceral fluid is more hyperosmotic than that of several other local species. This may aid in fluid uptake (Ferguson, 1994) and maintaining body form.
Flora and Fairbanks, 1966
Kozloff 1987, 1996
Smith and Carlton, 1975
Brewer, Reid and Konar, Brenda, 2005. Chemosensory responses and foraging behavior of the seastar Pycnopodia helianthoides. Marine Biology 147(3): pp 789-795 (abstract): (Pycnopodia bypassed uninjured prey of the butter clam Saxidomus giganteus in favor of injured individuals; apparently due to chemical cues.)
Ferguson, John C., 1994. Madreporite inflow of seawater to maintain body fluids in five species of starfish. pp. 285-289 in Bruno David, Alain Guille, Jean-Pierre Feral, and Michel Roux (eds). Echinoderms through time. Balkema, Rotterdam.
Greer, D., 1961. Feeding behavior and morphology of the digestive system of the seastar Pycnopodia helianthoides. M.S. Thesis, University of Washington, Seattle, WA
Mauzey, K.P., C. Birkeland, and P.K. Dayton, 1968. Feeding behavior of asteroids and escape responses of their prey in the Puget Sound region. Ecology 49: pp 603-619
Mladenova, P., S. Igdoura, S. Asotra, and R. Burke, 1989. Purification and partial characterization of an autotomy-promoting factor from the sea star Pycnopodia helianthoides. Biological Bulletin 176: pp. 169-175
Moitoza, D. and D. Phillips, 1979. Prey defense, predator preference, and nonrandom diet: The interactions between Pyconopdia helianthoides and two species of urchins. Marine Biology 53: pp 299-304
Nishizaki, Michael T. and Josef Daniel Ackerman,
2005. A secondary
chemical cue facilitates juvenile-adult postsettlement associations in
red sea urchins. Limnology and Oceanography 50(1): pp 354-362
franciscanus urchins release a chemical signal which causes
to aggregate underneath them when the adults detect the presence of Pycnopodia
General Notes and Observations: Locations, abundances, unusual behaviors:
This is a common species subtidally in the area around Rosario.
2014: This species is being especially hard-hit by seastar wasting disease. We have observed many individuals succumbing rapidly to the disease.
2015: For the first time in my memory, I have gone a whole summer without seeing a single live Pycnopodia helianthoides, either subtidally around Rosario or out on the open coast. They seem to have been thoroughly devastated by the wasting disease.
2019 summer: During the course of many dives from the marine station this summer, divers encountered individual Pycnopodia helianthoides on at least two occasions (one of them I encountered myself). Both of them were around 30 cm diameter, which is still small for a Pycnopodia but it is definitely growing up. Before the wasting disease the species was common here and even abundant in some places, so it is gratifying to see them gradually appearing again. They are primarily a subtidal species but occur occasionally in the very low intertidal zone. I have yet to encounter one intertidally since 2014.
This seastar can move extremely rapidly for a seastar. Its presence elicits an escape reaction from many species such as the spiny scallop Chlamys hastata (click here for an .MPG movie), the sea cucumber Parastichopus californicus, and limpets.
This tiny individual was in the intertidal at Cape Flattery, WA. Photo by Dave Cowles, July 2010.
Authors and Editors of Page:
Dave Cowles (2005): Created original page