Pisaster ochraceous can be found anywhere from Alaska to Baja California. It is most commonly found in the Northeastern Pacific, being that it is a cold-water species. However, it is common in bays all year.
Biogeographic Regions: pacific ocean
Sea otters and gulls prey on this starfish. Pisaster ochraceus can retract such sensitive areas as the podia and skin papillae. Additionally, they may be able to shut the ambulacral grooves which contain the tube-feet, and then spread the spines over them protectively.
Known Predators:
The radius of P. ochraceus is anywhere from about 10 to 18 inches (25 to 45 cm) in diameter. Yellow, orange, brown, reddish or even purple make up the ranging colors of this heavy starfish. Basically it has a good size middle disk with five stout arms sticking out. On its upper side it has short, white spines in the pentagonal pattern.
Other Physical Features: ectothermic ; heterothermic ; radial symmetry
From studies in oceans and aquariums, it seems that many asteroids achieve a minimal life span of four to six years, and Pisaster ochraceous could reach an age of twenty years.
Typical lifespan
Status: wild: 20 (high) years.
Pisaster ochraceous can be found on wave-washed rocky shores, from above the low-tide zone to 90 m in depth. Because they can live in shallow water they need to survive in these living conditions, including strong surges, big temperature changes, dilution by rainfall, and dessication. Pisaster ochraceous is very resistant to dessication and it can tolerate a loss of thirty-percent of its body weight in body fluids.
Range depth: 90 (high) m.
Habitat Regions: temperate ; saltwater or marine
Aquatic Biomes: coastal
Other Habitat Features: intertidal or littoral
At the larval stage, Pisaster ochraceus are filter feeders, eating plankton.
Like all sea stars, an adult P. ochraceus has tube feet which they use for locomotion and for handling prey. Pisaster ochraceous feeds on mussels, chitons, and limpets, which they slowly pry open and devour. Snails, barnacles, echinoids, even decapod crustacea are also eaten. Pisaster ochraceous everts its stomach over the prey if it is too large to be swallowed whole, and digests the prey before swallowing it.
Animal Foods: mollusks; aquatic crustaceans; echinoderms; other marine invertebrates; zooplankton
Plant Foods: phytoplankton
Foraging Behavior: filter-feeding
Primary Diet: carnivore (Eats non-insect arthropods, Molluscivore , Eats other marine invertebrates); planktivore
Pisaster ochraceous is a predator and is a prey to sea otters and sea gulls. Its role as a keystone species has been well studied. In intertidal areas of Washington, when it was removed, the diversity of species in the area decreased.
Ecosystem Impact: keystone species
The only positive benefit for humans is that they are admired by tourists as they are clinging to the rocks on a bay area.
Positive Impacts: research and education
Pisaster ochraceous develops through several larval stages, one including the brachiolaria larva. Using ciliated arms to sweep food into its mouth, it glides through the water column. The cilia drive locomotion of the larva is supplemented by these same arms. The larva attaches itself to the substratum as it settles because each arm has a glandular tip. The five-armed adult is formed because it undergoes metamorphosis. Adults continue growing and the rate of growth is dependent on its food supply.
Development - Life Cycle: metamorphosis
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
This is the most common, large intertidal sea star and it occurs in great numbers on mussel beds on exposed coasts. Pisaster ochraceous is more tolerant to air exposure than any other Pisaster.
The neurosensory cells scattered over the asteroid body respond to mechanical, chemical, and optical stimuli. Sensory organs are developed only at the base of each terminal tentacle. At this location a great number of light-sensitive cells form an optic cushion which contains several ocelli.
Communication Channels: chemical
Perception Channels: visual ; tactile ; chemical
Pisaster ochraceous is mainly dioecious. The male gametes develop, but later only females ones are produced. During a transitional period, both eggs and sperm are produced. A pair of gonads branches into each arm off a circular genital strand located along the oral inner surface of the disc. Each gonad looks like a feathery cluster of tubules. During maturation of the gametes, the gonads greatly increase in size, pushing into the perivisceral cavity of the arms, often right up to the ends of the arms. The gonopores of the individual gonads open at the bases of the arms.
Breeding season: Spring
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); broadcast (group) spawning
There is no parental investment beyond spawning.
Parental Investment: pre-fertilization (Provisioning)
This species has a broad distribution in the Pacific from Alaska to Panama.
In Panama this species has been collected from Taboga Island (USNM E45306), Panama Bay, Gulf of Panama, eastern Pacific, North Pacific Ocean.
Fisher, W.K. (1930). Asteroidea of the North Pacific and Adjacent Waters, Pt. 3: Forcipulata (Concluded). Bulletin of the United States National Museum 76: 1-356.Pls. 1-93.
LSID urn:lsid:marinespecies.org:taxname:240755Asteracanthion margaritifer Müller & Troschel, 1842 (Synonym according to Fisher (1930))
Asterias conferta Stimpson, 1862
Asterias fissispina Stimpson, 1862 (Synonym according to Fisher (1926, 1930))
Asterias janthina Brandt, 1835 (Synonym according to Fisher (1930))
Asterias margaritifera Brandt in Fisher, 1930 (Synonym according to Fisher (1930))
Asterias ochracea Brandt, 1835
Pisaster fissispinus (Stimpson, 1862) (Synonym according to Fisher (1926, 1930))
Pisaster ochraceus broadcast spawns in the spring, from late May to mid June. Each starfish releases millions of small eggs and sperm. The larvae are planktotrophic and spend about 2 months in the water column before settling. Planktotrophic larvae are dependent on planktonic food. The timing of gamete release coincides with the spring plankton bloom to increase survival likelihood. Broadcast spawners see high pre-adult and low adult mortality. Since larvae survival depends on the quality and quantity of food, broadcast spawning is beneficial for greater dispersal to increase the chances of finding abundant and high quality food. Pisaster ochraceus reaches maturity at a wet-weight of 70-90 grams, which usually takes about 5 years. The long length of maturation is hypothesized to be so that the seastar is robust enough to produce two offpsring that survive to sexual maturity. This allows Pisaster ochraceus a greater chance of successfully replacing itself.
Pisaster ochraceus is the first sea star species observed with “starfish wasting syndrome,” a plague of significant concern to scientists, which causes sea stars along the North American Pacific coast to soften, lose their arms, and eventually disintegrate, sometimes just days after first symptoms appear.The outbreak is similar die-offs in 1970 and in 1990, however far more geographically expansive and affecting far more individuals. Scientists first sighted symptoms of the syndrome in September 2013 on sea stars on the Olympic Penninsula in Washington state; since then, massive population declines of many sea star species have been documented along much of the North American west coast, and continue to erupt in previously unaffected areas.
Known as a “keystone species” in the marine intertidal and subtidal ecosystems, the sharp population decline of P. ochraceus is expected to trigger wide-ranging changes in the relative compositions of other species, and cause a fundamental disruption at ecosystem level.Scientists still do not know the underlying cause for the wasting syndrome, and are examining potential infectious agents and environmental changes that might be implicated.
(Raimondi 2014; SeaStarWasting.org 2014 and references therein)
Pisaster ochraceus, generally known as the purple sea star, ochre sea star, or ochre starfish, is a common seastar found among the waters of the Pacific Ocean. Identified as a keystone species, P. ochraceus is considered an important indicator for the health of the intertidal zone.[2]
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This sea star has five stout rays that range in length from 10 to 25 centimeters (4 to 10 in). The rays are arranged around an ill-defined central disk. While most individuals are purple, they can be orange, orange-ochre, yellow, reddish, or brown. The aboral surface contains many small spines (ossicles) that are arranged in a netlike or pentagonal pattern on the central disk. The ossicles are no higher than 2 mm.[3][4] In Pisaster the tube feet have suckers on their distal ends which allow them to attach to the rocky substrate and live in heavily wave-swept areas.[5] P. ochraceus has a simple nervous system and does not have a brain. A nerve ring connects and relays impulses between the star's radial nerves.[6]
Two species that can be mistaken for P. ochraceus are P. giganteus, which has blue rings around white or purple spines, and P. brevispinus, which is pink with small white spines. These two species have different aboral spines and coloration which allows one to distinguish between the species. Evasterias troscheli may be confused with P. ochraceus at times as well. It can be distinguished by its smaller disk size and longer, tapering rays which are often thickest a short distance out from their base rather than at the base as in P. ochraceus.[4]
Members of Pisaster are dioecious but there is no sexual dimorphism and sexes can be separated only by the presence of eggs or sperm in the gonads. They reproduce by broadcast spawning, which occurs in the Puget Sound around May to July.[4] There is no parental investment beyond spawning.[7] Fertilization occurs in the water column and Pisaster ochraceous develops through several larval stages.[6]
The reproductive system consists of a pair of gonads branching into each ray off a circular genital strand which is along the oral inner surface of the central disc.[7] The gonads look like a feathery collection of tubules. In females there are orange gonads and in males they are whitish.[5] During maturation of the gametes, the gonads increase in size and can account for up to 40 percent of the sea star's weight.[4] The gonopores are too small to be seen, and can only be found when the sea stars are spawning.[4][6]
Many sea stars live to a minimal age of four years. P. ochraceus can live as long as twenty years.[7]
This species of seastar is often considered a keystone species in many intertidal regions. P. ochraceus is a predator of the California mussel, Mytilus californianus and reduces its abundance. This allows for other macroinvertebrates to persist. In an experimental removal of P. ochraceus, it was shown that Mytilus californianus becomes almost completely dominant of the intertidal community. When P. ochraceus is present there is a diverse intertidal community.[8]
At the larval stage, Pisaster ochraceus are filter feeders and their diet consists of plankton. As an adult, P. ochraceus feeds on mussels such as Mytilus californianus and Mytilus trossulus. They also feed on chitons, limpets, snails, barnacles, echinoids, and even decapod crustacea.[4][9][10]
P. ochraceus uses its tube feet to handle its prey. If the prey is too large to be swallowed whole, then it can use its tube feet to open shells. It can evert its stomach through its mouth and engulf its prey, liquify it with digestive enzymes and ingest the processed food. Mussels hold their valves together very securely but P. ochraceus can insert part of its everted stomach, or some digestive juices, through the narrow gap that exists where the byssal threads emerge from the shell. The mussel needs to open its valves periodically to feed and breathe and the sea star can exert a powerful traction with its tube feet, pulling the two valves further open. Once the stomach is inside the mussel, digestion takes place. It is thought one sea star can consume eighty Californian mussels in a year.[11]
_Starfish,_Oregon_coast.jpg)
Pisaster ochraceus has been described as a keystone species. Experiments by zoologist Robert T. Paine in the 1960s demonstrated that a loss of only a few individual P. ochraceus seastars had a profound impact on mussel bed population, thereby reducing the health of the intertidal environment.[2] With only a few natural predators (sea otters and seagulls) it is suggested that the principal enemies of P. ochraceus are human collectors and casual tidepool visitors.[12] Pisaster ochraceus has not been evaluated by the International Union for Conservation of Nature (IUCN).[7]
P. ochraceus can be found from Prince William Sound in Alaska to Point Sal in Santa Barbara Co., California. The subspecies found within the warmer waters from Santa Barbara County to Baja California is P. o. segnis.[13]
This sea star can be found in great numbers on mussel beds and on wave-washed rocky shores. The juveniles are often found in crevices and under rocks.[6] Its depth range is from above the low-tide zone to 90 m. P. ochraceous is very durable and can tolerate a loss of thirty percent of its body weight in body fluids.[7]
A study found that P. ochraceus will not be affected by ocean acidification in the same way as most calcareous marine animals. This normally causes decreased growth due to the increased acidity dissolving calcium carbonate. Researchers found that when P. ochraceus was exposed to 21 °C (70 °F) and 770 ppm CO2 (beyond rises expected in the next century) they survived. It is thought that this is because the animal's calcium is nodular and so it is able to compensate for the lack of carbonate by growing more fleshy tissue instead.[14][15]
Pisaster ochraceus, generally known as the purple sea star, ochre sea star, or ochre starfish, is a common seastar found among the waters of the Pacific Ocean. Identified as a keystone species, P. ochraceus is considered an important indicator for the health of the intertidal zone.
