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Sea Urchin

Sea urchin


- Euechinoidea
  - Superorder Atelostomata
    - Order Cassiduloida
    - Order Spatangoida (heart urchins)
  - Superorder Diadematacea
    - Order Diadematoida
    - Order Echinothurioida
    - Order Pedinoida
  - Superorder Echinacea
    - Order Arbacioida
    - Order Echinoida
    - Order Phymosomatoida
    - Order Salenioida
    - Order Temnopleuroida
  - Superorder Gnathostomata
    - Order Clypeasteroida (sand dollars)
    - Order Holectypoida
- Perischoechinoidea
    - Order Cidaroida (pencil urchins) Cidaroida Cidaroida Cidaroida Cidaroida Cidaroida Sea urchins are spiny sea creatures of the class Echinoidea found in oceans all over the world. (The name sea urchin means sea hedgehog, hedgehog being one meaning of the word urchin). Their shell, which biologists call the test, is globular in shape, and covered with spines. The size of the test in adults is typically in the range of 3 to 10 cm. Typical sea urchins have spines 1-2 cm in length (e.g. "Sea urchin", right), a millimeter or two thick, and not terribly sharp. Diadema antillarum, familiar in the Caribbean, has thin spines that can be 10-20 cm long. Sea urchins are usually dull in color, common colors including green, olive, brown, purple, and black. Sea urchins are echinoderms (phylum Echinodermata), which also includes starfish, sea cucumbers, Brittle-stars, and crinoids. Like other echinoderms they have five-fold or pentamerous radial symmetry and move by means of hundreds of tiny, transparent, adhesive "tube feet." The pentamerous symmetry is not obvious at a casual glance, but is easily seen in the dried shell of the urchin (see picture below, right). Within the echinoderms, sea urchins are classified as echinoids (class Echinoidea). Specifically, the term "sea urchin" refers to the "regular echinoids," which are symmetrical and globular. The ordinary phrase "sea urchin" actually includes several different taxonomic groups: the Echinoida and the Cidaroida or "slate-pencil urchins", which have very thick, blunt spines (see image at right), and others (see taxonomic box on the right). Besides sea urchins, the Echinoidea also includes three groups of "irregular" echinoids: flattened sand dollars, sea biscuits, and heart urchins. heart urchin At first glance a sea urchin often appears to be an inanimate object, or one which is incapable of moving. Sometimes the most visible sign of life is the spines, which are attached at their bases to ball-and-socket joints and can be pointed in any direction. In most urchins, a light touch elicits a prompt and visible reaction from the spines, which converge toward the point that has been touched. A sea urchin has no visible eyes, legs or means of propulsion, but it can move freely over surfaces by means of its adhesive tube feet, working in conjunction with its spines. On the oral surface of the sea urchin is a centrally located jaw. It is surrounded by five horny teeth. The entire chewing organ is known as Aristotle's lantern. The name comes from Aristotle's accurate description in his History of Animals: :...the urchin has what we may call its head and mouth down below, and a place for the issue of the residuum up above. The urchin has, also, five hollow teeth inside, and in the middle of these teeth a fleshy substance serving the office of a tongue. Next to this comes the oesophagus, and then the stomach, divided into five parts, and filled with excretion, all the five parts uniting at the anal vent, where the shell is perforated for an outlet... In reality the mouth-apparatus of the urchin is continuous from one end to the other, but to outward appearance it is not so, but looks like a horn lantern with the panes of horn left out. (Tr. D'Arcy Thompson) The spines, which in some species are long and sharp, serve to protect the urchin from predators. Sea urchins feed mainly on algae. The spines can inflict a painful wound on a human who steps on one, but they are not seriously dangerous and it is not clear that the spines are truly venomous (unlike the pedicellariae between the spines, which are). Sea urchin is one of the favorite foods of sea otters. Recently the population of sea otters in the Monterey Bay of California has diminished. As a result, the population of sea urchins has multiplied and they are chewing up the kelp forest in the area and upsetting the ecosystem. Left unchecked, urchins will devastate their environment, creating what biologists call an urchin desert, devoid of aquatic plants and the fauna they support. Humans consume the reproductive organs ("roe") either raw or briefly cooked. Sea urchin roe is a popular food in Korean cuisine, and it is called "uni" in Japanese sushi cuisine. It is also a traditional food in Chile, known as an "erizo". Apart from domestic consumption, Chile and a number of other countries export the sea urchin to Japan in order to meet its demand throughout the country. The bare shells ("tests") of sea urchins are sometimes found on beaches, and are often sold in seaside souvenir shops. Dropping a sea urchin into ordinary household bleach quickly removes the spines and flesh substance, leaving a clean test. The test has a dramatic geometrical beauty and looks utterly unlike the familiar molluscan seashells. The sea urchin occupies a special place in biology due to its long-time use as a standard subject for studies in embryology. The sea urchin, particularly Arbacia punctulata, is the source of textbook descriptions of "the" egg, "the" embryo, and their early development. Theodor Boveri studied two species of sea urchin and concluded that all chromosomes were needed for normal embryonic development. At the Marine Biological Laboratory at Woods Hole, the Arbacia egg achieved almost the status of a standard "living cell" for physiological, biochemical and cytological work—resulting, of course, in overfishing and, in 1945, the near-extinction of the local Arbacia population. Sea urchins are a favored organism for studies of development using a systems biology [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11872831]approach, often in conjunction with gene knockdown studies using Morpholino antisense oligos [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12578984]. Since the sea urchin is globular and radially symmetrical, and since like other organisms its early embryological stages are globular and radially symmetrical, it is surprising that its larval stage, known as a pluteus, is not. The pluteus exhibits only bilateral symmetry. (Pluteus is Latin for "easel," to which the larvae of some species really do show a close resemblance). During development, the sea urchin must transform first itself from having radial to bilateral symmetry, and then again from having bilateral to radial symmetry. bilateral symmetryA group of pluteus larvae viewed under a dissecting microscope between crossed polarizers is a dramatic sight. The entire larva, including the calcareous skeleton, is transparent. However, the skeleton is birefringent. The result is that only the skeleton becomes visible--in glowing rainbow colors which change as the swimming larva changes its orientation with respect to the polarizers.

Geological history

The earliest known echinoids are found in the rocks of the upper part of the Ordovician period, and they have survived to the present day where they are a successful and diverse group of organisms. In well preserved specimens the spines may be present, but usually only the test is found. Sometimes isolated spines are common as fossils. Some echinoids (such as Tylocidaris clavigera which is found in the Cretaceous period Chalk Formation of England) had very heavy club-shaped spines that would be difficult for an attacking predator to break through and make the echinoid awkward to handle. Such spines are also good for walking on the soft sea-floor. England Complete fossil echinoids from the Paleozoic era are generally rare, usually consisting of isolated spines and small clusters of scattered plates from crushed individuals. Most specimens occur in rocks from the Devonian and Carboniferous periods. The shallow water limestones from the Ordovician and Silurian periods of Estonia are famous for the echinoids found there. The Paleozoic echinoids probably inhabited relatively quiet waters. Because of their thin test they would certainly not have survived in the turbulent wave-battered coastal waters inhabited by many modern echinoids today. During the upper part of the Carboniferous period there was a marked decline in echinoid diversity and this trend continued into the Permian period. They neared extinction at the end of the Paleozoic era, with just six species known from the Permian period. By the upper part of the Triassic period their numbers began to increase again. The echinoids diversified into many types throughout the Jurassic period and into the Cretaceous period. During the Mesozoic and Cenozoic eras the echinoids flourished. However most echinoid fossils are restricted to certain localities and formations, but where they do occur they are quite often abundant. An example of this is Enallaster which may be collected by the thousand in certain outcrops of limestone from the Cretaceous period in Texas. Some echinoids (such as Micraster which is found in the Cretaceous period Chalk Formation of England and France) serve as zone (or index) fossils. As they evolved rapidly over time such fossils are useful in enabling geologists to date the rocks in which they are found. However, most echinoids are not abundant enough and may be too limited in their geographic distribution to serves as zone fossils.

References and further reading


- Smith, Andrew B. (1984), Echinoid Palaeobiology (Special topics in palaeontology). London: Allen & Unwin. ISBN 0045630011
- [http://animaldiversity.ummz.umich.edu/site/accounts/classification/Echinoidea.html#Echinoidea Animal Diversity Web Classification of the Echinoidea]

External links


- [http://seaurchin.org/ Sea Urchin Harvesters Association - California] Category:Model organisms Category:Echinoderms ja:ウニ

Euechinoidea


- NOTE - UNDER CONSTRUCTION

Infra Class Acroechinoidea

Infra Class Echinothurioidea

Category:Equinodermata taxonomy

Clypeasteroida


- Clypeasterina
- Laganina
- Rotulina
- Scutellina The common sand dollar is the skeleton or test of a marine animal. By the time the test washes up on the beach, it is missing its velvety covering of minute spines and has a somewhat bleached appearance due to its exposure to the sun. Sand dollars are in the Echinoid class of marine animals. When alive, one species, Echinarachnius parma, is outfitted in a maroon-colored suit of moveable spines that encompass the entire shell. Like its close relative the sea urchin, the sand dollar has five sets of pores arranged in a petal pattern. The pores are used to move sea water into its internal water-vascular system, which allows for movement. pore Sand dollars live beyond mean low water on top of or just beneath the surface of sandy or muddy areas. The spines on the somewhat flattened underside of the animal allow it to burrow or to slowly creep through the sand. Fine, hair-like cilia cover the tiny spines. These cilia, in combination with a mucous coating, move food to the mouth opening which is in the center of the star shaped grooves on the underside of the animal. The anus is also located on the bottom, near the edge. Its food consists of plankton and organic particles that end up in the sandy bottom. On the ocean bottom, sand dollars are frequently found together. This is due in part to their preference of soft bottom areas, which are convenient for their reproduction. The sexes are separate and, as with most echinoids, gametes are released into the water column. The free-swimming larvae metamorphose through several stages before the test begins to form, and they become bottom dwellers. The name "sand dollar" is a reference to the round, flat shape of the skeleton, which is similar to a large coin. larva larva

References


- Gosner, Kenneth L., Guide to Identification of Marine and Estuarine Invertebrates; 1971 by John Wiley & Sons, Inc.
- Robbins, Sarah Fraser and Clarice Yentsch, The Sea Is All About Us; 1973 Harcourt Brace Jovanovich, Inc.
- [http://animaldiversity.ummz.umich.edu/site/accounts/classification/Clypeasteroida.html Animal Diversity Web classification of Order Clypeasteroida]

External links


- [http://www3.ns.sympatico.ca/samson3/dollar.htm The Sand Dollar Legend] - The history of the sand dollar and a legend about them.
- [http://octopus.gma.org/Tidings/sanddollar.html The Common Sand Dollar by Cheryl Page]
- [http://www.starstuffs.com/articles/sanddollar.html Sand Dollar as A Spiritual Sign of Hope]
- [http://oceanlink.island.net/ask/echino.html GREAT WEBSITE from Ask a Scientist] Category:Echinoderms

Animal shell

The hard, rigid outer calcium carbonate covering of certain animals is called a shell. While many animals, particularly those that live in the sea, produce exoskeletons, usually only those of mollusks are considered to be shells. It is sometimes erroneously claimed that shells are made of chitin, but these are unrelated materials (except for their hardness and use as a covering by animals). The shell is usually made of nacre, an organic mixture of outer layers of horny conchiolin (a scleroprotein), followed by an intermediate layer of calcite or aragonite, and then a layer of calcium carbonate (CaCO3) in the form of platy crystals. Nacre is secreted by the ectodermic cells of the mantle tissue of certain species of mollusk. Mollusk blood is rich in a liquid form of calcium. In these mollusks the calcium is concentrated out from the blood where it can crystallize as calcium carbonate. The individual crystals of each layer differ in shape and orientation. Nacre is continually deposited onto the inner surface of the animal's shell (the iridescent nacreous layer, also known as mother of pearl), both as a means to smoothen the shell itself and as a defense against parasitic organisms and damaging detritus. parasitic organisms When a mollusk is invaded by a parasite or is irritated by a foreign object that the animal cannot eject, a process known as encystation entombs the offending entity in successive, concentric layers of nacre. This process eventually forms what we call pearls and continues for as long as the mollusk lives. Shells are very durable and outlast the otherwise soft-bodied animals that produce them by a very long time. Large amounts of shells may form sediment and become compressed into limestone. Shells that wash up on beaches are called seashells, and are collected by some enthusiasts.

External links


- [http://www.seapulse.com/gallery/categories.php?cat_id=1 Shell Identification]

Related topics


- Carapace
- Coral
- Shell (material) Category:Mollusc products Category:Zoology ja:貝殻

Echinoderm



- Asteroidea
- Blastoidea (extinct)
- Concentricycloidea
- Crinoidea
- Echinoidea
- Holothuroidea
- Ophiuroidea Echinoderms (Echinodermata) is a phylum of marine animals found in the ocean at all depths. This phylum dates back to the lower Cambrian period and represents about 7000 living species and 13000 extinct ones. 6 classes made it to the Modern Era:
- Asteroidea (asteroids / starfish or sea stars): 1,500 species that capture prey for their own food.
- Concentricycloidea (sea daisies), have a unique water vascular system.
- Crinoidea (crinoids / feather stars or sea lilies): 600 species that are suspension feeders.
- Echinoidea (echinoids / sea urchins and sand dollars): 1,000 species; members of that class have movable spines.
- Holothuroidea (sea cucumbers): 1,000 species, elongated animals resembling slugs.
- Ophuiroidea (brittle stars and basket stars), the largest class of echinoderms. Fossil forms included Blastoids, Edrioasteroids and several peculiar Early Cambrian animals such as Helicoplacus, Carpoids, Homalozoa and possibly Machaerids. They evolved from bilaterally symmetric creatures. Later forms were lopsided. Echinoderms' larvae are ciliated free-swimming organisms that organize in a bilaterally symmetric fashion that makes them look like embryonic chordates. Later, the left side of the body grows at the expense of the right side, which is eventually absorbed. The left side then grows in a pentaradially symmetric fashion, in which the body is arranged in five parts around a central axis. All echinoderms exhibit fivefold radial symmetry in portions of their body at some stage of life, even if they have secondary bilateral symmetry. They also have a mesodermal endoskeleton made of tiny calcified plates and spines, that forms a rigid support contained within tissues of the organism; some groups have modified spines called pedicellariae that keep the animal free of debris. Echinoderms possess a hydraulic water vascular system, a network of fluid-filled canals that function in locomotion, feeding, and gas exchange. They also possess an open and reduced circulatory system, and have a complete digestive tube (tubular gut). They have a simple radial nervous system that consists of a modified nerve net (interconnected neurons with no central organs); nerve rings with radiating nerves around the mouth extending into each arm; the branches of these nerves coordinate the movements of the animal. Most echinoderms, with the exception of the sea cucumber, have a brain, although it is very small. The sexes are usually separate, and eggs and sperms are generally released into the water, in which case fertilization takes place externally. Many echinoderms have remarkable powers of regeneration: a starfish cut radially into a number of parts will, over the course of several months, regenerate into as many separate, viable starfish. A section as small as a single arm (with the commensurate central-body mass and neural tissue) will, in ideal circumstances, successfully regenerate in this way. Echinoderms, like chordates, are deuterostomes and are therefore thought to be the most closely related of the major phyla to the chordates, being a sister group to chordates plus hemichordates. (Some believe that acorn worms are more closely related to echinoderms than chordates.) Because of a controversial interpretation of Homalozoa, a minority of classifiers place the echinoderms into the Chordata. Echinodermata is the largest phylum to lack any fresh water or land representatives.

External links


- [http://tolweb.org/tree?group=Echinodermata&contgroup=Deuterostomia Echinodermata] from the Tree of Life website.
- [http://www.northwestdiver.com/creature_feature/echinoderms.php Echinoderms] from the Creature Feature website. Category:Animals Category:Echinoderms ja:棘皮動物

Starfish

Forcipulatida
Paxillosida
Platyasterida
Spinulosida
Valvatida
Sea stars or starfish are marine invertebrates belonging to phylum Echinodermata, class Asteroidea. The names sea star and starfish are also used for the closely related brittle stars, which make up the class Ophiuroidea. They exhibit a superficially radial symmetry, typically with five or more "arms" which radiate from an indistinct disk (pentaradial symmetry). In fact, their evolutionary ancestors are believed to have had bilateral symmetry, and sea stars do have some remnant of this body structure. Sea stars do not have movable skeletons, but instead possess a hydraulic water vascular system. The water vascular system has many projections called tube feet, on the ventral face of the sea star's arms, which function in locomotion and feeding. As these creatures are echinoderms and not actually fish, most marine biologists prefer to replace the term starfish with the less misleading term sea star.

Distribution

There are about 1,800 living species of sea star, and they occur in all of the Earth's oceans. The greatest variety of sea stars are found in the northern Pacific Ocean. Most species are 20-30 cm across, but they can vary from as little as 1 cm to as much as 65 cm. Species of the group Valvatida tends to be dominant in diversity in the shallow tropical waters of Indo-Pacific area - while Forcipulatida and an amount of Spinulosida have their greatest diversity in the colder (temperate to polar) water of the oceans. Species from the order Notomyotida are only known from the deep sea - the same applies to the order Brisingida as well.

External Anatomy

Brisingida Sea stars are composed of a central disc with (usually) five arms exhibiting pentaradial symmetry. The mouth is located underneath the sea star on the oral or ventral suface. The spiny upper surface covering the species is called the aboral or dorsal surface. On the aboral surface there is a structure called the madreporite which acts as a water filter and supplies the sea star's water vascular system with water to move. Sea stars have a simple eye at the end of each arm. The eye is able to "see" only differences of light and dark which is useful in detecting movement. On the surface of the sea star surrounding the spines 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 colonising the sea star. The radial canal which is across each arm of the sea star has what are called ampullae which surround the radial canal. The ampullae are tooth-like structures. The aboral surface is also covered with papulae that are involved with the sea stars respiratory system. Sea stars are often brightly colored, usually from reddish hues to violet, and unusual colors such as green and blue exist in some species, but come in muted colors as well. Patterns including mosaic-like tiles formed by ossicles, stripes, interconnecting net between spines, pustules with bright colors, mottles or spots. This mainly serves as camouflage or warning coloration displayed by many other marine animals as protection to the predator. Several types of toxins have been extracted from several species of sea stars and now being subjected into research worldwide for curing diseases or other uses such as pesticides.

Internal Anatomy

Inside the sea star underneath the hepatic caeca are the gonads which are involved in reproduction. The space inside the body not occupied by the internal organs is known as the perivisceral coelom. The body cavity also contains the water vascular system that operates the tube feet, and the hemal system. Hemal channels form rings around the mouth (the oral hemal ring), closer to the top of the starfish (the aboral hemal ring), and around the digestive system (the gastric hemal ring). The axial sinus, a portion of the body cavity, connects the three rings. Each ray also has hemal channels running next to the gonads. hemal

Digestion and excretion

Sea star digestion is carried out in two separate stomachs, the cardiac stomach and the pyloric stomach. The cardiac stomach, which is a sack like stomach located at the center of the body may be everted - pushed out of the organism's body and used to engulf and digest food. Some species take advantage of the great endurance of their water vascular systems to force open the shells of bivalve molluscs such as clams and mussels, and inject their stomachs into the shells. Once the stomach is inserted inside the shell it digests the mollusk in place. The sea star's anus is located at the center top of the animal. 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, and even small fish in addition to molluscs. Partially-digested food is passed to the inside of the sea star where digestion continues in the pyloric stomach. Due to all of this digestive demand, the sea star's arms are filled with digestive glands called pyloric caeca or hepatic caeca. Some echindoderms have been shown to live for several weeks without food under artificial conditions - it is believed that they may receive some nutrients from organic material dissolved in seawater.

Nervous System

Echinoderms have rather complex nervous systems. All echinoderms have a nerve plexus (a network of interlacing nerves) 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.

Circulation and respiration

esophagus There are three places on the sea star where circulation occurs. These are the perivisceral coelom (the space inside the body not occupied by the organs), the water vascular system, and the hemal system. Hemal channels form rings around the mouth (the oral hemal ring), closer to the top of the starfish (the aboral hemal ring), and around the digestive system (the gastric hemal ring). The axial sinus, a portion of the body cavity, connects the three rings. Each ray also has hemal channels running next to the gonads. There is a dorsal sac connected to the hemal system which pulsates like a very inefficient heart to help transfer nutrients from the digestive tract. The water vascular system uses cilia and the constantly contracting ampullae to keep things moving. An ionic imbalance causes water to flow into the madreporite, entering the water vascular system. Some of this water is diverted into the periviscerial coelom (the large cavity in which major organs are suspended), where it is circulated by the beating of cilia. Most oxygen enters the starfish via diffusion into the tube feet (with the water vascular system), or the papulae (small sacs covering the upper body surface.

Behaviour

Reproduction

Most starfish reproduce in a method similar to the sponge. The starfish gather in a group (using environmental signals to coordinate the timing), and release their gametes into the water, where they will hopefully connect with gametes from the opposite sex. After fertilization, there are a variety of ways that the eggs can proceed. Small eggs (those without much yolk) grow into free-swimming larvae which feed on small organisms until they metamorphose into juvenile sea stars and can begin living on the ocean floor. Eggs with larger yolks can develop into a similar larvae which is planktonic, but feeds on its yolk instead of other organisms. Some eggs may go through direct development, where the yolk is abundant and the egg passes directly into a juvenile form, without a larval stage. Sea stars are developmentally (embryologically) known as deuterostomes. Since echinoderms and chordates share this same embryological pattern, they are thought to be closely related. Nevertheless, as these creatures are invertebrates and not actually fish, most marine biologists are pushing to completely replace the term starfish with sea star.

Locomotion

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.

Regeneration

Sea stars have a remarkable ability to regenerate. Some species of sea star 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. These species will regenerate several starfish from a single one which is torn apart. One genus particularly noted for its regeneration ability is Linckia, named for naturalist J.H. Linck. These sea stars can cast off an arm that regrows into an entire organism, as a means of asexual reproduction.

Geological history

Fossil sea stars and brittle stars are first known from rocks of Ordovician age (Herringshaw, 2004; Shackleton, 2005; Blake & Guensburg, 2005), indicating that the two groups probably diverged in the Cambrian. However, Ordovician examples of the two groups show many similarites and can be difficult to distinguish (see e.g. Sutton et al, 2005). Complete fossil sea stars are very rare, but where they do occur they may be abundant. Most fossil sea stars consist of scattered individual plates or segments of arms. This is because the skeleton is not rigid, as in the case of echinoids (sea urchins), but is composed of many small plates (or ossicles) which quickly fall apart and are scattered after death and the decay of the soft parts of the creature. Scattered sea star ossicles are reasonably common in the Cretaceous Chalk Formation of England. Three famous localities where complete fossil sea stars are found are the Devonian Bundenbach slates of Bundenbach in Germany, the Jurassic lithographic Solnhofen limestone of Solnhofen in Germany, and the Jurassic 'Sea star bed' of the Middle Lias formation near Bridport, Dorset in England.

See also


- Asterias
- Ophiuroidea (Brittle stars).
- Category:Fictional Starfish

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 Manuel; 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

Resources

"starfish." Encyclopædia Britannica. 2005. Encyclopædia Britannica Premium Service 16 May 2005 . "echinoderm." Encyclopædia Britannica. 2005. Encyclopædia Britannica Premium Service 16 May 2005 . Dale, Jonathan. "Starfish Science." Madreporite Nexus. 10 May 2000. 17 May 2005 . "Sea star." Wikipedia, the free encyclopedia. 7 May 2005, 02:31 UTC. 16 May 2005 . Category:Echinoderms ja:ヒトデ simple:Sea star

Sea cucumber

Subclass Apodacea
 Apodida
 Molpadiida

Subclass Aspidochirotacea
 Aspidochirotida
 Elasipodida

Subclass Dendrochirotacea
 Dactylochirotida
 Dendrochirotida The sea cucumber is an echinoderm of the class Holothuroidea, with an elongated body and leathery skin. Mostly found on the sea floor. It is so named because of its cucumber-like shape. Like all echinoderms, sea cucumbers have an endoskeleton just below the skin. Sea cucumbers are generally scavengers, feeding on debris in the benthic layer. Their diet consist of plankton and other organic matter found in the sea. One way they might get a supply of food is to position themselves in a current where they can catch food that flow by with their tentacles when they open. Another way is to sift through the bottom sediments using their tentacles. They can be found in great numbers beneath fish farms. They have the peculiar adaptation of expelling first sticky threads, perhaps to incapacitate predators, and then their internal organs when startled by a potential predator. These organs can then be regrown. Sea cucumbers reproduce by releasing sperm and ova into the ocean water. Depending on conditions, one organism can produce thousands of gametes.

Sea cucumbers in art

Surprising as it may seem, sea cucumbers have inspired musical composition: in the first of his Embryons desséchés Erik Satie presents the "(desiccated embryo) of a Holothuroidean" and inserts a description of the animal in the score: :(...) :The Holothuroidean crawls across bolders and rocky surfaces. :This sea-animal purrs like a cat; also, it produces disgusting silky threads. :Light appears to have an incommodating effect on it. :(...) Nonetheless it are the sea cucumber's closest relatives (the echinoidea) that get more attention from scientists, both as embryos and as fossils. Sea cucumbers have also inspired thousands of haiku in Japan, where they are called "namako." In haiku, they are usually called "sea slugs," for the sake of the sluggish metaphor, and there is a book with almost 1000 holothurian haiku translated from Japanese titled "Rise, Ye Sea Slugs!" by Robin D. Gill (ISBN 0974261807). According to the OED, the "sea slug" is a holothurian first, but biologists insist on using "sea slug" only for the nudibranch, a mollusc famous for its neat little brain. The sea-cucumber itself does not mind either way, for it is famous for having no brain whatsoever, not even the start of a ganglia. The Japanese scientist-author Motokawa Tatsuo of TIT describes the sea cucumber as the opposite of us humans: We have brains and are made of dumb material, while they, lacking brains boast smart material.

Sea cucumber as food and medicine

Sea cucumber is one of the most unique foodstuffs in Chinese cuisine. It is highly valued for its supposed medicinal properties. The flesh of the animal is "cleaned" in a process that takes several days. Trepang is often purchased dried, and rehydrated before use. The product is used in Chinese stews and braised dishes due to its gelatinous texture but is unappetising on its own. In Japanese cuisine, Konowata is made of cured sea cucumber entrails from which they extract, salt, and cure. It is considered a major delicacy. Some varieties of sea cucumber (known as "gamat" in Malaysia) are said to have excellent healing properties. There are pharmaceutical companies being built based on this gamat product. Extracts are prepared and made into oil, cream or cosmetics. Some products are intended to be taken internally. The effectiveness of sea cucumber extract in tissue repair has been the subject of serious study. It not only helps a wound heal more quickly but is also said to reduce scarring.

External links


- [http://www.healwell.com.my/what.htm Healing properties of the gamat]
- [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10523072&dopt=Abstract Effects on tissue repair]
- [http://www.ansinet.org/fulltext/pjbs/pjbs6242068-2072.pdf Study of healing properties] (PDF format) Category:Chinese cuisine Category:Echinoderms ja:ナマコ

Brittle star

Oegophiurida
Ophiurida
Phrynophiurida Brittle stars are echinoderms, closely related to starfish. They crawl across the sea-floor using their flexible arms as "legs" for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to 60 centimeters (2 feet) in length on the largest specimens. Ophiuroidea contains two large clades, the Ophiurida (brittle stars) and Euryalida (basket stars). Many of the ophiuroids are rarely encountered in the relatively shallow depths normally visited by humans, but they are a diverse group. clade There are some 1,500 species of brittle stars living today, and they are largely found in deep waters more than 500 metres (1,650 feet) down.

Range/ Location

Ophiuroids can be found in all of the major marine provinces, from the poles to the tropics. In fact, crinoids, holothurians, and ophiuroids rule the floor of the deep oceans at depths below 500 meters. Basket stars usually confined to the deeper parts of this range. Ophiuroids are known even from abyssal (> 6000m) depths. However brittle stars are also common, if cryptic, members of reef communities, where they hide under rocks and even within other living organisms. A few ophiuroid species can even tolerate brackish water, an ability otherwise almost unknown among echinoderms. The ophiuroids diverged in the Early Ordovician, roughly 500 million years ago. Their fossil record is weak, since brittle stars (as their name implies) tend to break apart easily.

Disk and internal organs

Like all echinoderms, the Ophiuroidea possess a calcium carbonate (calcite) skeleton. In ophiuroids, the calcite ossicles are fused to form armor plates (collectively, the test). Of all echinoderms, the Ophiuroidea may have the strongest tendency toward 5-segment radial (pentaradial) symmetry. The body outline is similar to the Asteroidea, in that ophiuroids have five arms joined to a central disk (calyx). However the central body disk in ophiuroids is sharply marked off from the arms. The disk contains all of the viscera. That is, the internal organs of digestion and reproduction never enter the arms (in contrast to Asteroidea). The mouth is rimmed with five jaws. Behind the jaws is a short esophagus and a large, blind stomach cavity which occupies much of the dorsal half of the disk. Ophiuroids have neither an intestine nor an anus. Digestion occurs within 10 pouches or infolds of the stomach. Gas exchange and excretion occur through cilia-lined sacs called bursae; each opens onto the interambulacral area (between the arm bases) of the oral (ventral) surface of the disc. Typically there are 10 bursae, and each fits between two stomach digestive pouches. The sexes are separate in most species. Gonads in the disc open into the bursae. Gametes are then shed by way of the bursal sacs. Many species actually brood developing larvae in the bursae. The ophiuroid coelom is strongly reduced, particularly in comparison to other echinoderms. The nervous system consists of a main nerve ring which runs around the central disk. At the base of each arm, the ring attaches to a radial nerve which runs to the end of the limb. Ophiuroids have no eyes, as such. However, they have some ability to sense light through receptors in the epidermis. Ophiurid arm cross section. from Biodidac.Arms: Both the Ophiurida and Euryalida have five long, slender, flexible whip-like arms, up to 60 cm in length. They are supported by an internal skeleton of calcium carbonate plates that referred to as vertebral ossicles. These "vertebrae" articulate through ball-in-socket joints, and are controlled by muscles as shown in the figure. The body and arms are also bear calcite plates and delicate spines. Euryalids are similar, if larger, but their arms are forked and branched. Ophiuroid podia generally function as sensory organs. They are not usually used for feeding, as in Asteroidea. The vessels of the water vascular system end in tube feet. The water vascular system generally has one madreporite. However, some forms have none. Suckers and ampullae are absent from the tube feet. Ophiuroids can readily regenerate lost arms or arm segments unless all arms are lost. Ophiuroids use this ability to escape predators, like lizards who automize, or deliberately shed, part of their tails to confuse pursuers.

Locomotion

Brittle stars use their arms for locomotion. They do not, like starfishes, depend on tube feet. Brittle stars move fairly rapidly by wriggling their arms which are highly flexible and enable the animals to make either snake-like or rowing movements. Their movement has some sililarities with animals with bilateral symmetry.

Trophic

Many ophiuroids are scavengers or detritivores. Small organic particles are moved into the mouth by the tube feet. Ophiuroids may also prey on small crustaceans or worms. Basket stars, in particular may be capable of suspension feeding, using their mucous covering the branched arms to trap plankton and bacteria.

See also


- Starfish (Asteroidea) Category:Echinoderms ja:クモヒトデ

Radial symmetry

In biology, radial symmetry is a property of some multicellular organisms. Any cut through the center of a radially symmetric organism, with the plane of the cut going from the top to the bottom (dorsal to ventral), results in roughly equal halves in terms of organs and body parts. For example, wedding cakes exhibit radial symmetry. Organisms with radial symmetry only have a single orientation: dorsal-ventral (or anterior-posterior, there is no differentiation). Organisms with bilateral symmetry, on the other hand, have two orientations: dorsal-ventral, as well as anterior-posterior. Cnidaria and ctenophores are the only animals with true radial symmetry. Instead of this full rotational symmetry, Echinoderms (e.g. sea urchins and starfish) possess a variant of radial symmetry in which orientations of 72° rotation are considered equivalent (5-fold rotational symmetry); this is known as pentamerism. Category:Developmental biology Category:Symmetry

Tube feet

Tube feet are the many small tubular projections found most famously on the ventral face of a sea star's arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand dollars and sea cucumbers and many other sea creatures. sea cucumber Tube feet function in locomotion and feeding. The tube feet in a sea star are arranged in grooves along the arms. They operate by hydraulic pressure. They are used to pass food to the ventral mouth at the center, and can attach to surfaces. A sea star that is overturned simply turns one arm over and attaches it to a solid surface, and levers itself the right way up. Feet, tube



Spine (biology)

A spine is a rigid, pointed surface protuberance or needle-like structure on an animal, shell, or plant, presumably serving as a defense against attack by predators. For examples: the quills of a porcupine, the needles of a cactus, or the prickles of a shrub like the rose are all spines. Although spines generally serve as a passive defense mechanism, in some species they can be hollow and contain poisonous substances that cause lasting pain or even paralysis.

Plant spines and thorns

Botanists use several terms somewhat loosely when referring to spine- or needle-like structures on plants; however, the following differences are typically distinguished:
- prickle – a sharp outgrowth from the epidermis, also called an emergence and usually involving some subdermal tissue as well; see also hair.
- spine – a modified stipule or sharp branchlet found in a leaf axil or on the margin of a leaf.
- thorn – Sharp outgrowth from a stem other than at a node; a modified stem. Thorns and prickles, most notably those on roses, are common literary symbols for the hidden dangers or woes of something beautiful or pleasant, as in "Every rose has its thorn." Roses lack true thorns since their prickles emerge from the epidermis rather that the pericycle. Growth from the pericycle would make it a modifided stem and therefore a thorn. Some roses have been bred not to have prickles. Other examples of plants with these characteristics include: the thistle, some berry plants, and a number of plants in the weed family.

See also


- Seta

References


- Esau, K. 1965. Plant Anatomy, 2nd Edition. John Wiley & Sons. 767 pp.
- Llamas, K. A. 2003. Tropical Flowering Plants. Timber Press, Portland. 423 pp. Category:Plant anatomy

Predator

, but the goose is too wary.]] A predator is an animal or other organism (such as a carnivorous plant) that hunts and kills other organisms for food in an act called predation. Predators are either carnivores or omnivores. The difference between a predator and a parasite is that for a predator killing the prey is necessary for consuming it, but for parasites it is not even desirable because a parasite lives on or in its host. Some might consider herbivores to be predators as well, but this is arguable as most herbivores only consume parts of their food species, leaving the remainder alive. However, where the "prey" consists of single-celled algae, the activities of the herbivorous grazer is generally of the same nature as that of a carnivore. As usual in ecology as most fields of study, there is seldom consensus on the distinctions; some ecologists prefer functional definitions like the one outlined above, others rather look at the ecological dynamics the relationships between the species create. There may be hierarchies of predators; for example, though small birds prey on insects, they may in turn be prey for snakes, which may in turn be prey for hawks. A predator at the top of its food chain (that is, one that is preyed upon by no organism) is called an apex predator; examples include the Great White Shark, Tiger and Crocodile. Sometimes a predator may have a profound influence on the balance of organisms in a particular ecosystem; introduction or removal of this predator, or changes in its population, can have drastic cascading effects on the equilibrium of many other populations in the ecosystem. In this instance the organism may be described as an apex predator or keystone predator. The Volterra-Lotka equations describe a simple mathematical model of the interaction between predators and their prey. Category:Ecology

Erol Koyuncu

Milli Güreşçi. (Artvin-Hopa, 1966). Hopa’da doğdu. Kâmil Türköz, Muharrem Atik ve Rus Sapunov gibi ünlü güreşçilerin antrenörlüğünde güreş çalıştı ve güreş eğitimi aldı. Avrupa dünya çapında birçok başarı ve şampiyonluklar kazandı. Greko-romen 68 kg.da Avrupa 9. (1990, Polonya-Poznan), Greko-romen 74 kg.da Dünya 9. (1990, İtalya-Roma), Greko-romen 82 kg.da Akdeniz Oyunları 4. (1991, Yunanistan-Atina), Greko-romen 82 kg.da Avrupa 4. (1991, Almanya-Aschaffenburg), Greko-romen 74 kg.da Avrupa Şampiyonu (1994, Yunanistan-Atina), Greko-romen 74 kg.da Dünya 9. (1994, Finlandiya-Tampera), Büyükler Greko-romen stil 76 kg.da Avrupa 10. (1997, Finlandiya-Qoulu), Greko-romen 76 kg.da Akdeniz Oyunları 4. (1997, İtalya-Bari). Tek kol, çırpma, bele girme, kontra teknikler kendisine has, iyi uyguladığı güreş teknikleridir. Rize Çaykur Spor Kulübünde güreş çalışmalarına devam etmektedir.

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