sea star

sea star
n.
starfish.
[1560-70]

* * *

also called  starfish 
 any marine invertebrate of the class Asteroidea (phylum Echinodermata) having rays, or arms, surrounding an indistinct central disk. Despite their older common name, they are not fishes.

      The roughly 1,600 living species of sea stars occur in all oceans; the northern Pacific has the greatest variety. Most species are 20 to 30 cm (8 to 12 inches) across; some are only 1 cm (0.4 inch), and others are as much as 65 cm (25 inches) across.

      Sea star arms—typically five in number—are hollow and, like the disk, covered with short spines and pedicellariae (pincerlike organs); on the lower side are grooves with rows of tube feet, which may be sucker-tipped or pointed. A sea star can lose one or more arms and grow new ones. Its tube feet enable it to creep in any direction and cling to steep surfaces.

 Primitive sea stars feed by sweeping organic particles that collect along the arm grooves into the mouth on the underside of the disk. Advanced forms either evert (turn outward) the stomach upon the prey (bivalve mollusks, coral polyps, other echinoderms) for external digestion or swallow the prey whole (see video of sea star preying upon a mussel). The internal skeleton of the sea star consists of limy plates. Respiration usually is through skin structures. Light-sensitive spots occur at the tips of the arms.

 Sea star reproduction typically is heterosexual, but hermaphroditism (reproductive organs of both sexes in one animal) occurs, and a few sea stars reproduce asexually by division of the body (fission). Some brood their eggs and young; nonbrooders may release into the water as many as 2.5 million eggs at a time (see video of sea star life cycle).

      Sea stars belong to three orders: Phanerozonia, Spinulosa, and Forcipulata. Edged sea stars, order Phanerozonia, have distinct marginal plates and therefore tend to be rigid. Members of the order have suction-tube feet; the anus may be lacking. Most of the deep-sea sea stars belong to this order, and many are burrowers. Albatrossaster richardi has been taken at a depth of 6,035 m (19,800 feet) near the Cape Verde Islands. The mud star (Ctenodiscus crispatus), about 10 cm (4 inches) across, with blunt, short arms and a broad, yellow disk, is abundant worldwide on mud bottoms of northern coasts. A number of sea star genera distributed throughout the Northern Hemisphere have longer, more pointed, spine-fringed arms; among these genera are Astropecten, Psilaster, and Luidia. The largest West Indies sea star, Oreaster reticulatus, is sometimes 50 cm (20 inches) across. Members of the chiefly Indo-Pacific genus Linckia can grow a new individual from a small piece of a single arm.

      Spiny sea stars, order Spinulosa, typically have clusters of spines; they have suction-tube feet but rarely pedicellariae. A common example in stony-bottomed European waters is the gibbous starlet (Asterina gibbosa). The sea bat (Patiria miniata) usually has webbed arms; it is common from Alaska to Mexico. Sun stars of the genera Crossaster and Solaster are found in northern waters; they have numerous short rays and a broad, often sunburst-patterned disk. The widely distributed S. endeca is 10-rayed and sometimes 50 cm across; the very common spiny sun star (Crossaster papposus) has as many as 15 arms. Cushion stars, of the circumboreal genus Pteraster, are plump five-rayed forms with raised tufts of spines and webbed, short, blunt arms.

      Sea stars with long-stalked, two-valved pedicellariae comprise the order Forcipulata—the “forceps carriers.” The pedicellariae have protective and, sometimes, food-taking functions. In most species the arms are long and rounded, and the disk is small. The order includes common shallow-water species worldwide—among them predators on bivalves such as clams, oysters, and mussels—such as Asterias rubens of northern Europe, A. vulgaris from Labrador to Long Island Sound, A. forbesi from Maine to the Gulf of Mexico, and A. amurensis from the Bering Sea to Korea. They use their suction feet to force open the bivalve's shell, then insert the stomach, and digest the prey. Pisaster brevispinus—at 65 cm (26 inches) one of the world's largest sea stars—inhabits the western coast of North America; it preys on other echinoderms known as sand dollars, which burrow to escape it. Perhaps the most common sea star of 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. The many-rayed sunflower sea star (Pycnopodia helianthoides) of Alaska to California has 15 to 24 arms and is often 60 cm (24 inches) across. Heliaster, a broad-disked, short-rayed genus of the western coast of Central America, may have as many as 50.

      For other echinoderms of similar name, see brittle star; feather star. For a species of special interest, see crown-of-thorns starfish.

* * *


Universalium. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • Sea star — (Zo[ o]l.) A starfish, or brittle star. [1913 Webster] …   The Collaborative International Dictionary of English

  • Sea Star — es un proyecto de cohete lanzador de microsatélites (hasta 13 kg) y banco de pruebas para el lanzador Neptune. Fue diseñado en 2005 por la empresa Interorbital y no ha pasado de la etapa de estudio. El lanzador tiene un diseño de etapa y media,… …   Wikipedia Español

  • sea star — sea′ star n. ivt starfish • Etymology: 1560–70 …   From formal English to slang

  • Sea Star — Die Sea Star war ein südkoreanischer Öltanker. Auf dem Weg vom saudiarabischen Ras Tanura nach Rio de Janeiro kollidierte das Schiff am 19. Dezember 1972 mit dem Tanker Horta Barbosa im Golf von Oman; beide gerieten in Brand. Auf der Sea Star… …   Deutsch Wikipedia

  • sea star — noun echinoderms characterized by five arms extending from a central disk • Syn: ↑starfish • Hypernyms: ↑echinoderm • Member Holonyms: ↑Asteroidea, ↑class Asteroidea * * * noun …   Useful english dictionary

  • sea star — Starfish Star fish ( f[i^]sh ), n. 1. (Zo[ o]l.) Any one of numerous species of echinoderms belonging to the class Asterioidea, in which the body is star shaped and usually has five rays, though the number of rays varies from five to forty or… …   The Collaborative International Dictionary of English

  • Sea Star Hotel — (Алания,Турция) Категория отеля: 3 звездочный отель Адрес: Elikesik Köyü Ulas Mevki …   Каталог отелей

  • Sea Star House — (Ао Нанг Бич,Таиланд) Категория отеля: 2 звездочный отель Адрес: 379 Moo 2 Ao Nang, Muang, Krab …   Каталог отелей

  • Sea Star Apartments — (Эйрли Бич,Австралия) Категория отеля: 4,5 звезд Адрес: 2 Nara Avenue, Whitsunda …   Каталог отелей

  • Sea Star Apartments Podstrana — (Подстрана,Хорватия) Категория отеля: Адрес: Grljevačka 142, 21312 По …   Каталог отелей

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”