Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish are also known as asteroids due to being in the class Asteroidea. About 1,900 species of starfish live on the seabed in all the world's oceans, from warm, tropical zones to frigid, polar regions. They are found from the intertidal zone down to abyssal depths, at 6,000 m (20,000 ft) below the surface.
A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance. The concept was introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. Some keystone species, such as the wolf and lion, are also apex predators.
A tide pool or rock pool is a shallow pool of seawater that forms on the rocky intertidal shore. These pools typically range from a few inches to a few feet deep and a few feet across. Many of these pools exist as separate bodies of water only at low tide, as seawater gets trapped when the tide recedes. Tides are caused by the gravitational pull of the sun and moon. A tidal cycle is usually about 25 hours and consists of two high tides and two low tides.
The California mussel is a large edible mussel, a marine bivalve mollusk in the family Mytilidae.
Ecological extinction is "the reduction of a species to such low abundance that, although it is still present in the community, it no longer interacts significantly with other species".
Pisaster giganteus, the giant sea star, giant spined star, or knobby sea star is a species of sea star that lives along the western coast of North America from Southern California to British Columbia. It makes its home on rocky shores near the low tide mark. It preys on mollusks. It can grow as large as 24 in (61 cm) in diameter. Its color varies from brown to red or purple.
The Davenport Tide Pools are located just past the town of Davenport, California in the United States. They are located where Davenport Landing Road loops to the sea off Highway 1. Parallel ridges running perpendicular to the sea separate the tide pools from each other and make them unique, producing communities in which organisms which normally could not live in close proximity to each other can do so. The beach is day use only, open sunrise to sunset.
Pisaster is a genus of Pacific sea stars that includes three species, P. brevispinus, P. giganteus, and P. ochraceus. Their range extends along the Pacific coast from Alaska to southern California in the intertidal zone. The largest individuals of Pisaster can reach diameters of up to 70 cm (28 in) across; they all develop five arms, but some may be lost from injury or disease, and occasionally the re-growth of an injured arm will result in an individual with more than five arms.
Dendraster excentricus, also known as the eccentric sand dollar, sea-cake, biscuit-urchin, western sand dollar, or Pacific sand dollar, is a species of sand dollar in the family Dendrasteridae. It is a flattened, burrowing sea urchin found in the north-eastern Pacific Ocean from Alaska to Baja California.
Nucella emarginata, common name the emarginate dogwinkle, is a species of medium-sized predatory sea snail, a marine gastropod mollusk in the family Muricidae, the murex snails or rock snails.
Nucella lamellosa, commonly known as the frilled dogwinkle or wrinkled purple whelk, is a species of sea snail, a marine gastropod mollusk in the family Muricidae, the murex snails or rock snails. This species occurs in the eastern Pacific Ocean, its range extending in the intertidal zone from the Aleutian Islands southward to central California.
Nucella ostrina, the northern striped dogwinkle, is a species of sea snail, a marine gastropod mollusk in the family Muricidae, the murex snails or rock snails. Other common names for this mollusk include emarginate dogwinkle, short-spired purple dogwinkle, striped dogwinkle, ribbed dogwinkle, emarginate whelk, ribbed rock whelk, rock thais, short-spired purple snail and rock whelk.
Pollicipes polymerus, commonly known as the gooseneck barnacle or leaf barnacle, is a species of stalked barnacle. It is found, often in great numbers, on rocky shores on the Pacific coasts of North America.
Leptasterias hexactis is a species of starfish in the family Asteriidae, commonly known as the six-rayed star. It is found in the intertidal zone of the western seaboard of the United States. It is a predator and is unusual among starfish in that it broods its eggs and young.
Evasterias troschelii is a species of starfish in the family Asteriidae. Its common names include the mottled star, false ochre sea star and Troschel's true star. It is found in Kamchatka and the north western coast of North America.
Sea star wasting disease or starfish wasting syndrome is a disease of starfish and several other echinoderms that appears sporadically, causing mass mortality of those affected. There are approximately 40 species of sea stars that have been affected by this disease. At least 20 of these species were on the Northwestern coast of Mexico to Alaska. The disease seems to be associated with increased water temperatures in some locales, but not others. It starts with the emergence of lesions, followed by body fragmentation and death. In 2014 it was suggested that the disease is associated with a single-stranded DNA virus now known as the sea star-associated densovirus (SSaDV). However, this hypothesis was refuted by recent research in 2018 and 2020. Sea star wasting disease is still not fully understood.
Ptilosarcus gurneyi, the orange sea pen or fleshy sea pen, is a species of sea pen in the family Pennatulidae. It is native to the northeastern Pacific Ocean where it lives in deep water anchored by its base in sand or mud. It has received its common name because of its resemblance to a quill in a bottle of ink.
Semibalanus cariosus, commonly known as the thatched barnacle, rock barnacle or horse barnacle, is a species of acorn barnacle occurring in the northern Pacific Ocean.
Lottia instabilis is a species of sea snail, a true limpet, a marine gastropod mollusk in the family Lottiidae. Common names include the unstable limpet, the unstable seaweed limpet and the rocking chair limpet. It is native to the northern Pacific Ocean where it feeds on kelp in the intertidal zone and the shallow sub-littoral zone.
The green world hypothesis proposes that predators are the primary regulators of ecosystems: they are the reason the world is 'green', by regulating the herbivores that would otherwise consume all the greenery. It is also known as the HSS hypothesis, after Hairston, Smith and Slobodkin, the authors of the seminal paper on the subject.
