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Encyclopedia > Starfish
Sea Star
"Asteroidea" from Ernst Haeckel's Kunstformen der Natur, 1904
"Asteroidea" from Ernst Haeckel's Kunstformen der Natur, 1904
Scientific classification
Kingdom: Animalia
Phylum: Echinodermata
Subphylum: Asterozoa
Class: Asteroidea
Orders

Brisingida (100 species[1])
Forcipulatida (300 species[1])
Paxillosida (255 species[1])
Notomyotida (75 species[1])
Spinulosida (120 species[1])
Valvatida (695 species[1])
Velatida (200 species[1]) Image File history File links Download high resolution version (2337x3294, 1546 KB) Summary The 40th plate from Ernst Haeckels Kunstformen der Natur (1904), depicting organisms classified as Asteridea. ... Ernst Haeckel. ... The 8th print, Discomedusae. ... Scientific classification redirects here. ... For other uses, see Animal (disambiguation). ... Classes Asteroidea Concentricycloidea Crinoidea Echinoidea Holothuroidea Ophiuroidea Echinoderms (Echinodermata) is a phylum of marine animals found in the ocean at all depths. ... In scientific classification used in biology, the order (Latin: ordo, plural ordines) is a rank between class and family (termed a taxon at that rank). ... Families Sub-order:Granulosina Archasteridae Chaetasteridae Goniasteridae Odontasteridae Ophiodiasteridae Oreasteridae Sub-order:Tumulosina Sphaerasteridae Valvatida is an order of sea stars (Asteroidea), which contains 7 families. ...

Sea stars are any echinoderms belonging to the class Asteroidea. The names sea star and starfish are also (incorrectly) used for the closely related brittle stars, which make up the class Ophiuroidea. Orange Starfish at Olympic National Park Seastars are a group of marine invertebrates. ... Subphyla & Classes Homalozoa Gill & Caster, 1960 Homostelea Homoiostelea Stylophora † Ctenocystoidea Robison & Sprinkle, 1969 Crinozoa Crinoidea Paracrinoidea † Regnéll, 1945 Cystoidea †von Buch, 1846 Asterozoa Ophiuroidea Asteroidea Echinozoa Echinoidea Holothuroidea Ophiocistioidea Helicoplacoidea † Arkarua † Homalozoa † Pelmatozoa † Edrioasteroidea † Blastozoa † Blastoidea † Eocrinoidea †Jaekel, 1899 † = extinct Echinoderms (Phylum Echinodermata, from the Greek for spiny skin... A class is the rank in the scientific classification of organisms in biology below Phylum and above Order. ... Orders ME Oegophiurida Ophiurida Phrynophiurida Brittle stars are echinoderms, closely related to starfish. ... Brittle stars are echinoderms, closely related to starfish. ...


Starfish exhibit a superficially radial symmetry. They typically have five or more "arms" which radiate from an indistinct disk (pentaradial symmetry). However, the evolutionary ancestors of echinoderms are believed to have had bilateral symmetry. Starfish do exhibit some superficial remnant of this body structure, evident in their larval pluteus forms. The elaborate patterns on the wings of butterflies are one example of bilateral symmetry. ... The elaborate patterns on the wings of butterflies are one example of bilateral symmetry. ... The elaborate patterns on the wings of butterflies are one example of bilateral symmetry. ...


Starfish do not rely on a jointed, movable skeleton for support and locomotion (although they are protected by their skeleton), but instead possess a hydraulic water vascular system that aids in locomotion. The water vascular system has many projections called tube feet on the ventral face of the starfish's arms which function in locomotion and aid with feeding. For other uses, see Skeleton (disambiguation). ... The water vascular system is a hydraulic system used by echinoderms, such as starfish and sea urchins, for locomotion, food and waste transportation, and respiration[1]. The system is composed of canals connecting numerous tube feet. ... The tube feet can be clearly seen on this sea star Tube feet are the many small tubular projections found most famously on the ventral face of a sea stars arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... In biology and physics, animal locomotion is the study of how animals move, and is part of biophysics. ... Feeding is the process by which organisms, typically animals, obtain food. ...


The star fish usually hunt for shelled animals such as oysters and clams. They have two stomachs. One stomach is used for digestion, and the other stomach can be extended outward to engulf and digest prey. This feature allows the starfish to hunt prey that is much larger than its mouth would otherwise allow. Starfish are able to regenerate lost arms. A new starfish may be regenerated from a single arm attached to a portion of the central disk.

Contents

External anatomy

Red-knobbed starfish Protoreaster linckii, a starfish from the Indian Ocean
Red-knobbed starfish Protoreaster linckii, a starfish from the Indian Ocean

Starfish are composed of a central disc from which arms sprout in pentaradial symmetry. Most starfish have 5 arms, but some have more or fewer. Some starfish have shown differing numbers of limbs within a single species. The mouth is located underneath the starfish, on its ventral surface. The spiny upper surface is called the aboral or dorsal surface. On the aboral surface there is a structure called the madreporite, a small white spot located slightly off-center on the central disc which acts as a water filter and supplies the starfish's water vascular system with water to move. Porcellanasteridae employ additional cribriform organs used to generate current in the burrows made by these infaunal starfish. Image File history File links Download high resolution version (1800x1286, 744 KB) Red-knobbed Starfish Protoreaster linckii at Bristol Zoo Aquarium, Bristol, England. ... Image File history File links Download high resolution version (1800x1286, 744 KB) Red-knobbed Starfish Protoreaster linckii at Bristol Zoo Aquarium, Bristol, England. ... The term aboral refers to the side of a radially symmetrical animal, such as a starfish, that does not contain the mouth. ... Small red or yellow button-like structure that often looks like a small wart on a sea stars central disk. ...

Schmedelian pin-cushion sea star on Meedhupparu house reef in the Maldives, Culcita schmideliana
Schmedelian pin-cushion sea star on Meedhupparu house reef in the Maldives, Culcita schmideliana

While having their own basic body plan, starfish radiate diversely in shapes and colors, the morphology differing between each species. A starfish may have dense rows of spines as a means of protection, or it may have no spines at all. Ranging from nearly pentagonal (example: Indo-pacific cushion star, Culcita novaeguineae) to gracile stars like those of the Zoroaster genus. Image File history File linksMetadata Download high-resolution version (2048x1536, 593 KB)Schmedelian pin-cushion sea star. ... Image File history File linksMetadata Download high-resolution version (2048x1536, 593 KB)Schmedelian pin-cushion sea star. ... The tone of this article is inappropriate for an encyclopedia. ...

Blood star (Henricia sanguinolenta) at the New England Aquarium, displaying its tube feet.
Blood star (Henricia sanguinolenta) at the New England Aquarium, displaying its tube feet.

Surrounding the spines on the surface of the starfish are small white objects known as pedicellariae. There are large numbers of these pedicellariae on the external body which serve to prevent encrusting organisms from colonizing the starfish. The radial canal which is across each arm of the starfish has tooth-like structures called ampullae, which surround the radial canal. Image File history File linksMetadata Download high-resolution version (1728x2304, 989 KB) Blood star (Henricia sanguinolenta). ... Image File history File linksMetadata Download high-resolution version (1728x2304, 989 KB) Blood star (Henricia sanguinolenta). ... The New England Aquarium is a major aquarium located in the city of Boston, Massachusetts. ... Pedicellariae are commonly found on Echinoderms. ... The ampulla of Vater is a sphincter (a small muscle) where the common bile duct enters the duodenum. ...


On the end of each arm or ray there is a microscopic eye which allows the starfish to see, although it only allows it to see light and dark, which is useful to see movement.


Patterns including mosaic-like tiles formed by ossicles, stripes, interconnecting net between spines, pustules with bright colors, mottles or spots. These mainly serve as camouflage or warning coloration which is displayed by many marine animals as a means of protection against predation. Several types of toxins and secondary metabolites have been extracted from several species of starfish. Research into the efficacy of these compounds for possible pharmacological or industrial use occurs worldwide. The bright colours of this Yellow-winged Darter dragonfly serve as a warning to predators of its noxious taste. ... For a list of biologically injurious substances, including toxins and other materials, as well as their effects, see poison. ... It has been suggested that this article or section be merged into natural product. ...

Closeup of the top surface of a starfish
Closeup of the top surface of a starfish

Internal anatomy

Dissection of Asterias rubens.
Dissection of Asterias rubens.

The body cavity also contains the water vascular system that operates the tube feet, and the circulatory system, also called the hemal system. Hemal channels form rings around the mouth (the oral hemal ring), closer to the top of the starfish and around the digestive system (the gastric hemal ring). A portion of the body cavity called the axial sinus connects the three rings. Each ray also has hemal channels running next to the gonads. The tube feet can be clearly seen on this sea star Tube feet are the many small tubular projections found most famously on the ventral face of a sea stars arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand... For transport in plants, see Vascular tissue. ...


Digestion and excretion

Starfish digestion is carried out in two stomachs: the cardiac stomach and the pyloric stomach. The cardiac stomach is a sack like stomach located at the center of the body and may be everted out of the organism's body to engulf and digest food. Some species are able to use their water vascular systems to force open the shells of bivalve mollusks such as clams and mussels by injecting their stomachs into the shells. With the stomach inserted inside the shell, the starfish is able to digest the mollusk in place. The cardiac stomach is then brought back inside the body, and the partially digested food is moved to the pyloric stomach. Further digestion occurs in the intestine. Waste is either excreted through the anus on the aboral side of the body, or excreted through the mouth if the anus is absent as in brittle stars. For the industrial process, see anaerobic digestion. ... In anatomy, the stomach is a bean-shaped hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication. ... Orders Subclass Protobranchia Solemyoida Nuculoida Subclass Pteriomorphia - oysters Arcoida Mytiloida Pterioida Subclass Paleoheterodonta - mussels Trigoinoida Unionoida Subclass Heterodonta - clams, zebra mussels Veneroida Myoida Subclass Anomalosdesmata Pholadomyoida Animals of the Class Bivalvia are known as bivalves because they typically have two-part shells, with both parts being more or less symmetrical. ... Classes Caudofoveata Aplacophora Polyplacophora Monoplacophora Bivalvia Scaphopoda Gastropoda Cephalopoda † Rostroconchia The mollusks or molluscs are the large and diverse phylum Mollusca, which includes a variety of familiar creatures well-known for their decorative shells or as seafood. ... For other uses, see Clam (disambiguation). ... Subclasses Pteriomorpha (marine mussels) Palaeoheterodonta (freshwater mussels) Heterodonta (zebra mussels) The common name mussel is used for members of several different families of clams or bivalve molluscs, from both saltwater and freshwater habitats. ... The term aboral refers to the side of a radially symmetrical animal, such as a starfish, that does not contain the mouth. ... Orders ME Oegophiurida Ophiurida Phrynophiurida Brittle stars are echinoderms, closely related to starfish. ...


Because of this ability to digest food outside of its body, the sea star is able to hunt prey that are much larger than its mouth would otherwise allow, including arthropods, small fish, and mollusks. Subphyla and Classes Subphylum Trilobitomorpha Trilobita - trilobites (extinct) Subphylum Chelicerata Arachnida - spiders,scorpions, etc. ... For other uses, see Fish (disambiguation). ...


Some echinoderms live several weeks without food under artificial conditions. It is believed that they may receive some nutrients from organic material dissolved in seawater.


Sea stars and other echinoderms have endoskeletons, suggesting that echinoderms are very closely related to chordates; animals with a hollow nerve chord that usually have vertebrae. Endoskeleton of a swordfish An endoskeleton is an internal support structure of an animal. ... Classes See below Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates. ...


Variety

As mentioned above there are over 1800 species and many are undiscovered. Some of the better known starfish include:

A Japanese variety known locally as Gohongaze is considered an edible delicacy[2]. Binomial name Linckia laevigata (Linnaeus, 1758) Linckia laevigata (sometimes called the blue Linckia or Blue Sea Star) is a species of starfish in the shallow waters of tropical Indo-Pacific. ... The Japanese sea star is from Japan and was introduced to Tasmania recently. ... Native to southern Australia the Carpet sea star, Patiriella spp. ... Binomial name Coscinasterias calamaria (Gray, 1840) Coscinasterias calamaria, or the eleven-armed sea star, is a sea star of the family Asteriidae, endemic to southern Australia and New Zealand. ... Unlike the average five armed sea star, this sea star actualy looks more like a pentagon, or a pin cushion. ... Binomial name Astropecten polyacanthus Müller and Troschel, 1842 Astropecten polyacanthus, or the comb star, is a sea star of the family Astropectinidae. ... Binomial name Acanthaster planci (Linnaeus, 1758) The crown-of-thorns starfish (Acanthaster planci) is a red-colored starfish with thorn-like spines sprouting all over its body for protection. ... The common starfish (Asterias rubens) is the most common and familiar starfish in the north-east Atlantic. ...


Nervous system

Echinoderms have rather complex nervous systems, but lack a true centralized brain. All echinoderms have a network of interlacing nerves called a nerve plexus which lies within as well as below the skin. The esophagus is also surrounded by a number of nerve rings which send radial nerves that are often parallel with the branches of the water vascular system. The ring nerves and radial nerves coordinate the starfish's balance and directional systems. Although the echinoderms do not have many well-defined sensory inputs, they are sensitive to touch, light, temperature, orientation, and the status of water around them. The tube feet, spines, and pedicellariae found on starfish are sensitive to touch, while eyespots on the ends of the rays are light-sensitive. The nervous system is a highly specialized network whose principal components are nerves called neurons. ... For other uses, see Brain (disambiguation). ... The esophagus or oesophagus (see American and British English spelling differences), sometimes known as the gullet, is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. ...


Behavior

Diet

Sea star Pisaster ochraceus consuming a mussel in Central California
Sea star Pisaster ochraceus consuming a mussel in Central California

Most species are generalist predators, some eating clams, and oysters; or any animal too slow to evade the attack (e.g. dying fish). Some species are detritivores, eating decomposed animal and plant material or organic films attached to substrate. The others may consume coral polyps (the best-known example for this is the infamous Acanthaster planci), sponges or even suspended particles and planktons (starfish from the Order Brisingida). The processes of feeding and capture may be aided by special parts; Pisaster brevispinus or Short-spined Pisaster from the West Coast of America may use a set of specialized tube feet to extend itself deep into the soft substrata to extract prey (usually clams)[3]. Grasping the shellfish, the Starfish slowly pries open the shell by wearing out the Adductor muscle and then inserts its stomach into an opening to devour the organism. Image File history File links Size of this preview: 800 × 600 pixel Image in higher resolution (1632 × 1224 pixel, file size: 1. ... Image File history File links Size of this preview: 800 × 600 pixel Image in higher resolution (1632 × 1224 pixel, file size: 1. ... This article is about the U.S. state. ... This snapping turtle is trying to make a meal of a Canada goose, but the goose is too wary. ... Categories: Pages needing attention | Animal stubs ... The name oyster is used for a number of different groups of mollusks which grow for the most part in marine or brackish water. ... For other uses, see Fish (disambiguation). ... Extant Subclasses and Orders Alcyonaria    Alcyonacea    Helioporacea Zoantharia    Antipatharia    Corallimorpharia    Scleractinia    Zoanthidea [1][2]  See Anthozoa for details For other uses, see Coral (disambiguation). ... Binomial name Acanthaster planci (Linnaeus, 1758) The crown-of-thorns starfish (Acanthaster planci) is a red-colored starfish with thorn-like spines sprouting all over its body for protection. ... Classes Calcarea Hexactinellida Demospongiae The sponges or poriferans (from Latin porus pore and ferre to bear) are animals of the phylum Porifera. ... This article is about the real-life under-sea organisms. ... Pacific redirects here. ... The tube feet can be clearly seen on this sea star Tube feet are the many small tubular projections found most famously on the ventral face of a sea stars arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand... For other uses, see Clam (disambiguation). ... Adductor can refer to: One of the anatomical terms of motion The adductor longus, adductor magnus, and adductor brevis muscles Adductor canal Category: ...


Reproduction

Starfish are capable of both sexual and asexual reproduction. Individual starfish are male or female. Fertilization takes place externally, both male and female releasing their gametes into the environment. Resulting fertilized embryos form part of the zooplankton. Gametes (in Greek: γαμέτες) —also known as sex cells, germ cells, or spores—are the specialized cells that come together during fertilization (conception) in organisms that reproduce sexually. ... Photomontage of plankton organisms Plankton is the aggregate community of weakly swimming but mostly drifting small organisms that inhabit the water column of the ocean, seas, and bodies of freshwater. ...


Starfish are developmentally (embryologically) known as deuterostomes. Their embryo initially develops bilateral symmetry, indicating that starfish probably share a common ancestor with the chordates, which includes the fish. Later development takes a very different path however as the developing starfish settles out of the zooplankton and develops the characteristic radial symmetry. Some species reproduce cooperatively, using environmental signals to coordinate the timing of gamete release; in other species, one to one pairing is the norm. For other uses, see Embryo (disambiguation). ... Phyla Echinodermata Hemichordata Chordata Xenoturbellida Chaetognatha (uncertain) Vetulicolia † Deuterostomes (taxonomic term: Deuterostomia; from the Greek: second mouth) are a superphylum of animals. ... Typical Classes Subphylum Urochordata - Tunicates Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... For other uses, see Fish (disambiguation). ...


Some species of starfish also reproduce asexually by fragmentation, often with part of an arm becoming detached and eventually developing into an independent individual starfish. This has led to some notoriety. Starfish can be pests to fishermen who make their living on the capture of clams and other mollusks at sea as starfish prey on these. The fishermen would presumably kill the starfish by chopping them up and disposing of them at sea, ultimately leading to their increased numbers until the issue was better understood. A starfish arm can only regenerate into a whole new organism if some of the central ring of the starfish is part of the chopped off arm.


Locomotion

The underside of a sea star. The inset shows a magnified view of the tube feet.
The underside of a sea star. The inset shows a magnified view of the tube feet.

Sea stars move using a water vascular system. Water comes into the system via the madreporite. It is then circulated from the stone canal to the ring canal and into the radial canals. The radial canals carry water to the ampullae and provide suction to the tube feet. The tube feet latch on to surfaces and move in a wave, with one body section attaching to the surfaces as another releases. Most starfish cannot move quickly. However, some burrowing species like starfish from genus Astropecten and Luidia are capable of rapid, creeping motion: "gliding" across the ocean floor. This motion results from their pointed tubefeet adapted specially for excavating patches of sand. Image File history File links Stachelhaeuter_fg01. ... Image File history File links Stachelhaeuter_fg01. ... Species See text. ...

Starfish skeleton
Starfish skeleton

Image File history File links Starfish_Roentgen_X-Ray_01_Nevit. ... Image File history File links Starfish_Roentgen_X-Ray_01_Nevit. ...

Regeneration

A sunflower starfish is regenerating arms that were lost to predators

Some species of starfish have the ability to regenerate lost arms and can regrow an entire new arm in time. Most species must have the central part of the body intact to be able to regenerate, but a few can grow an entire starfish from a single ray. Included in this group are the red and blue Linckia star. The regeneration of these stars is possible due to the vital organs kept in their arms.


Geological history

The larvae of echinoderms are ciliated, free-swimming organisms. They tend to look like embryonic chordates because they organize themselves bilaterally. As the organism grows, one side of the body grows more than the other, and it is eventually absorbed by the larger side. After that, the body is formed into five parts around a central axis. Then the echinoderm has radial symmetry.


Distribution

There are about 1,800 known living species of starfish, and they occur in all of the Earth's oceans. The greatest variety of starfish is found in the tropical Indo-Pacific. Areas known for their great diversity include the tropical-temperate regions around Australia, the tropical East Pacific, and the cold-temperate water of the North Pacific (California to Alaska). Asterias is a common genus found in European waters and on the eastern coast of the United States; Pisaster, along with Dermasterias ("leather star"), are usually found on the western coast. Habitats range from tropical coral reefs, kelp forests to deep-sea floor, although none of them live within the water column; all species of starfish found are living as benthos. Echinoderms need a delicate internal balance in their body; no starfish are found in freshwater environments. Species Asterias is a genus of the Asteriidae family of starfish (also known as sea stars). ... For other uses, see Europe (disambiguation). ... The tropics are the geographic region of the Earth centered on the equator and limited in latitude by the two tropics: the Tropic of Cancer in the north and the Tropic of Capricorn in the southern hemisphere. ... Part of a coral reef. ... Kelp Forest Kelp forests are a type of marine ecosystem established around colonies of kelp; they contain rich biodiversity. ... Seagrass growing off the coast of the Florida Keys. ... Classes Asteroidea Concentricycloidea Crinoidea Echinoidea Holothuroidea Ophiuroidea Echinoderms (Echinodermata) is a phylum of marine animals found in the ocean at all depths. ... Fresh water redirects here. ...


Notes

  1. ^ a b c d e f g Sweet, Elizabeth (2005-11-22). Asterozoa: Fossil groups: SciComms 05-06: Earth Sciences. Retrieved on 2008-05-07.
  2. ^ Cooking Starfish In Japan. Retrieved on 2008-05-07.
  3. ^ Nybakken Marine Biology: An Ecological Approach, Fourth Edition, page 174. Addison-Wesley Educational Publishers Inc., 1997.

Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 326th day of the year (327th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... is the 127th day of the year (128th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... is the 127th day of the year (128th in leap years) in the Gregorian calendar. ...

References

  • Blake DB, Guensburg TE; Implications of a new early Ordovician asteroid (Echinodermata) for the phylogeny of Asterozoans; Journal of Paleontology, 79 (2): 395-399; MAR 2005.
  • Gilbertson, Lance; Zoology Lab Manual; McGraw Hill Companies, New York; ISBN 0-07-237716-X (fourth edition, 1999).
  • Shackleton, Juliette D.; Skeletal homologies, phylogeny and classification of the earliest asterozoan echinoderms; Journal of Systematic Palaeontology; 3 (1): 29-114; March 2005.
  • Solomon, E.P., Berg, L.R., Martin, D.W. 2002. Biology, Sixth Edition.
  • Sutton MD, Briggs DEG, Siveter DJ, Siveter DJ, Gladwell DJ; A starfish with three-dimensionally preserved soft parts from the Silurian of England; Proceedings of the Royal Society B - Biological Sciences; 272 (1567): 1001-1006; MAY 22 2005.
  • Hickman C.P, Roberts L.S, Larson A., l'Anson H., Eisenhour D.J.; Integrated Principles of Zoology; McGraw Hill; New York; ISBN 0-07-111593-5 (Thirteenth edition; 2006).

Resources

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Asteroidea

Image File history File links Wikispecies-logo. ... Wikispecies is a wiki-based online project supported by the Wikimedia Foundation that aims to create a comprehensive free content catalogue of all species (including animalia, plantae, fungi, bacteria, archaea, and protista). ...

Gallery


  Results from FactBites:
 
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Starfish range in size from an inch in diameter to nearly a yard in diameter.
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Starfish, also sea star, common name for 5 orders and about 1500 living species of marine invertebrate animals characterized by radially arranged arms bearing locomotory tube feet.
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