Depth Range: P. ochraceus occurs in the low and middle intertidal zones, and sometimes in the subtidal zone (to 88 m). Pisaster feeds by using its tube feet to pull apart bivalve shells and extruding its stomach into the shells to digest the food. Saplings in Wyoming, May 6, 1998, born in the fires of 1988 in Yellowstone National Park, covering the ground next to the charred remains of the 200-year-old lodgepole pines (. Pisaster ochraceous can be found on wave-washed rocky shores, from above the low-tide zone to 90 m in depth. Notes: This species of seastar is often considered a keystone species in many intertidal regions. Photos by Chanda Brietzke (right), Brian Starzomski (top left), and Julia Fisher. 1998). 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 found within the warmer waters from Santa Barbara County to Baja, California is Pisaster ochraceus segnis, a subspecies of Pisaster ochraceus Habitat This sea star can be found in great numbers on mussel beds and on wave-washed rocky shores Some species, called keystone species, have a disproportionately large effect on the communities in which they occur. Paine and his students from the University of Washington spent 25 years removing the sea stars from a tidal area on the coast of â¦ Other articles where Pisaster ochraceus is discussed: sea star: â¦the American Pacific coast is P. ochraceus, a five-rayed species sometimes 35 cm (14 inches) across; it is usually reddish but has other colour phases. Pisaster ochraceus has been described as a keystone species. The way in which Pisaster where the central star pattern is formed by aboral spines. This competition among guilds emphasizes the fact that, in addition to food webs, the structure of the community is built on other types of interaction. Biodiversity and the stability of communities, Community equilibrium and species diversity, Interspecific interactions and the organization of communities, Community structure and the spread of mutualism, Commensalism and other types of interaction, The coevolutionary âarms raceâ versus reduced antagonism, Coevolution and the organization of communities, The importance of interspecific interactions, The geographic mosaic theory of coevolution, Coevolution of one species with several species. While most individuals are purple, they can be orange, orange-ochre, and brown. I found that aboral spine density was significantly higher in sea stars in more physically- However, individuals living in the subtidal may greatly exceed Pisaster ochraceus in size. Guilds may consist of different insect species that collect nectar in similar ways, various bird species that employ corresponding insect-foraging techniques, or diverse plant species that have evolved comparable floral shapes with which they attract the same group of pollinators. Many species also interact cooperatively to search for food or avoid predators. While the common habitat remains the mid-to-lower rocky intertidal zone, the geographic range is from Alaska to Baja California, Mexico (1). All communities are subject to periodic disturbances, ranging from events that have only localized effects, such as the loss of a tree that creates a gap in the canopy of a forest, to those that have catastrophic consequences, which include wildfires that sweep across vast landscapes or storms that pound immense stretches of shoreline. Events such as a fire that sweeps across a grassland or a storm that uproots trees within a forest create patches of habitat that are colonized by early successional species. There are around 40 different species of sea stars that have been affected by this disease. A keystone speciesâwhich can be any organism, from animals and plants to bacteria and fungiâis the glue that holds a habitat together. This heavy echinoderm can also be reddish or purple in color. Secondary succession occurs in areas where a community that previously existed has been removed; it is typified by smaller-scale disturbances that do not eliminate all life and nutrients from the environment. The disease seems to be associated with raised water temperatures in some places, but not others. Therefore, a species can be a keystone species in some communities but not in others. Pisaster ochraceus, the intertidal sea star, is a keystone species in the northwestern portion of the United States (Figure 19.25). Figs bear fruit year-round in some of these forest communities, and a large number of birds and mammals rely heavily on this small group of plant species during the times of the year when other food resources are scarce. Ochre Sea Star (Pisaster ochraceus) KINGDOM Animalia PHYLUM Echinodermata CLASS Asteroidea ORDER Forcipulatida FAMILY Asteriidae Ochre Sea Stars are relatively large sea stars, with five arms and a rough surface, the short spines on the upper surface arranged in wavy patterns.