An echinoderm is any deuterostomal animal of the phylum Echinodermata, which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry, and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone. The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian.
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.
Asterias amurensis, also known as the Northern Pacific seastar and Japanese common starfish, is a seastar found in shallow seas and estuaries, native to the coasts of northern China, Korea, far eastern Russia, Japan, Alaska, the Aleutian Islands and British Columbia in Canada. Two forms are recognised: the nominate and formarobusta from the Strait of Tartary. It mostly preys on large bivalve molluscs, and it is mostly preyed on by other species of starfish. Population booms in Japan can affect the harvest of mariculture operations and are costly to combat.
Mediaster aequalis is a species of sea star in the family Goniasteridae. It is native to the west coast of North America, ranging from Alaska to California. It is found in various habitats including beaches during very low tides, and at depths down to about 500 m (1,600 ft). Also known as the vermilion sea star, it is the type species of the genus Mediaster and was first described in 1857 by the American zoologist William Stimpson.
Leptasterias pusilla is a small, six-rayed sea star.
The scissortail sergeant or striptailed damselfish is a large damselfish. It earns its name from the black-striped tail and sides, which are reminiscent of the insignia of a military Sergeant, being similar to those of the sergeant major damselfish. It grows to a length of about 16 centimetres (6.3 in).
The Pacific seahorse, also known as the giant seahorse, is a species of fish in the family Syngnathidae. Their genus name (Hippocampus) is derived from the Greek word hippos, which means "horse" and campus, which means "sea monster." This species is the only seahorse species found in the eastern Pacific Ocean.
Cadlina luteomarginata, common name the yellow-edged cadlina, is a species of colorful sea slug, a dorid nudibranch, a shell-less marine gastropod mollusk in the family Cadlinidae.
Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, to spawn refers to the process of freely releasing eggs and sperm into a body of water ; the physical act is known as spawning. The vast majority of aquatic and amphibious animals reproduce through spawning. These include the following groups:
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.
Henricia leviuscula, commonly called the Pacific blood star, is a species of sea star found along the Pacific coast of North America.
Leptasterias is a genus of starfish in the family Asteriidae. Members of this genus are characterised by having six arms although five-armed specimens sometimes occur. L. muelleri is the type species. The taxonomy of the genus is confusing and Leptasterias hexactis seems to be a species complex. Some species brood their eggs.
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.
Orchitophrya stellarum is a species of single-celled marine ciliates, a member of the class Oligohymenophorea. It is found living freely in the north Atlantic and Pacific Oceans but is also parasitic, being found inside the gonads of starfish.
Leptasterias tenera is a species of starfish in the family Asteriidae. It is found on the eastern coast of North America.
Leptasterias polaris, the polar six-rayed star, is a species of starfish in the family Asteriidae. It is found in cold waters in the northwest Atlantic Ocean and in polar regions.
Pteraster militaris, the wrinkled star, is a species of starfish in the family Pterasteridae. It is found in the northern Pacific Ocean, the Arctic Ocean, the Barents Sea and the northern Atlantic Ocean.
Marthasterias is a genus of starfish in the family Asteriidae. Both species in the genus are commonly known as the spiny starfish.
Parvulastra vivipara, the Tasmanian live-bearing seastar, is a tiny, uniformly orange-yellow seastar, up to 15 mm (0.6 in) across. The species usually has five short arms and is a rounded, pentagon shape. Morphological variation is common and three, four or six arms are occasionally present. It is endemic to coastal waters in southeast Tasmania.
Pyura haustor is a species of sessile ascidian, or sea squirt, that lives in coastal waters in the north-eastern Pacific Ocean, attached to rocks or artificial structures. Common names for this species include the wrinkled seapump, the wrinkled sea squirt and the warty tunicate.
