The scientific name for starfish is Asteroidea. Both bipinnaria and brachiolaria larvae are bilaterally symmetrical. It casts off its stalk and becomes a free-living juvenile starfish about 1 mm (0.04 in) in diameter. , The body wall consists of a thin cuticle, an epidermis consisting of a single layer of cells, a thick dermis formed of connective tissue and a thin coelomic myoepithelial layer, which provides the longitudinal and circular musculature. Starfish of the order Paxillosida have no brachiolaria stage, with the bipinnaria larvae settling on the seabed and developing directly into juveniles. This had a cascading effect on the whole benthic community and reef-feeding fish.  They do this by autotomising some parts of their bodies or by budding. There is a reason for those names, this species come in a wide variation of colours.  Regrowth can take several months or years, and starfish are vulnerable to infections during the early stages after the loss of an arm. , Starfish do not appear to have any mechanisms for osmoregulation, and keep their body fluids at the same salt concentration as the surrounding water. Their survival is likely due to the nodular nature of their skeletons, which are able to compensate for a shortage of carbonate by growing more fleshy tissue. Starfish are carnivores that eat other forms of aquatic life that are smaller than their mouths. Sometimes at the full moon time, when the moon is really dazzling and hitting on the ocean, a starfish jumps out of the water and falls down. , "Sea Star" redirects here. Not-So-Sedentary Lifestyle – Despite their appearance, starfish can actually be quite mobile. The starfish is now pentaradially symmetrical. The stomach then envelops the prey to digest it, and finally withdraws back into the body. , Some species of starfish are able to reproduce asexually as adults either by fission of their central discs or by autotomy of one or more of their arms. , Starfish are widespread in the oceans, but are only occasionally used as food.  Some species like Labidiaster annulatus, Rathbunaster californicus and Novodinia antillensis use their large pedicellariae to capture small fish and crustaceans. ", In the Nickelodeon animated television series SpongeBob SquarePants, the eponymous character's best friend is a dim-witted starfish, Patrick Star. They also have body armour in the form of hard plates and spines. Fromia starfish consume microorganisms and an almost invisible film alga. It also looks grooved like some stony corals. Long-chain fatty acid amides of sphingosine occur frequently and some of them have known pharmacological activity. The pyloric stomach has two extensions into each arm: the pyloric caeca.  They vary in form, with some bearing external granules, tubercles and spines, but most are tabular plates that fit neatly together in a tessellated manner and form the main covering of the aboral surface. Some species have six or seven arms and others have 10–15 arms.  A few can regrow a complete new disc from a single arm, while others need at least part of the central disc to be attached to the detached part.  In these brooding species, the eggs are relatively large, and supplied with yolk, and they generally develop directly into miniature starfish without an intervening larval stage. They resemble the typical …  A study in Polynesia found that coral cover declined drastically with the arrival of migratory starfish in 2006, dropping from 50% to under 5% in three years. Scientific name: Oreaster reticulates Many species are brightly coloured in various shades of red or orange, while others are blue, grey or brown. The common starfish is found on rocky and gravelly substrates where it feeds o… , Having descended from bilateral organisms, starfish may move in a bilateral fashion, particularly when hunting or in danger. Despite the name, some starfish can have as many as 50 arms! Fluid movement is bidirectional and initiated by cilia. Starfish are most commonly seen with five arms in the traditional star shape, thus their name. Part of the gut is retained, but the mouth and anus move to new positions. It is a large starfish that preys upon hard, or stony, coral polyps. Fish have backbones, which makes them vertebrates. This arrangement enables both easy flexion of the arms by the starfish and the rapid onset of stiffness and rigidity required for actions performed under stress. Royal Starfish is found in the West Atlantic where it ranges from the United States (both the East Coast … , Apart from their function in locomotion, the tube feet act as accessory gills.  Georg Eberhard Rumpf found few starfish being used for food in the Indonesian archipelago, other than as bait in fish traps, but on the island of "Huamobel" [sic] the people cut them up, squeeze out the "black blood" and cook them with sour tamarind leaves; after resting the pieces for a day or two, they remove the outer skin and cook them in coconut milk.  Some species that prey on bivalve molluscs can transmit paralytic shellfish poisoning. The adult has from 12 to 19 arms, is typically 45 centimetres (18 inches) across, and feeds on coral polyps. , Because of this ability to digest food outside the body, starfish can hunt prey much larger than their mouths.  The ring nerves and radial nerves have sensory and motor components and coordinate the starfish's balance and directional systems. Although they are commonly called starfish, these animals aren't fish, which is why they are more commonly referred to as sea stars.. Sea stars are echinoderms, which means they are related to sea urchins, sand dollars, basket stars, brittle stars, and sea cucumbers.All echinoderms have a calcareous skeleton covered with skin. Starfish are not actually a fish at all , but are animals belonging to the Phylum Echinodermata, and are further divided into two classes Asteroidea(sea stars) and Ophiuroidea(brittle stars). The Bat Star fish, Asterina miniata, is so named because of its resemblance to a bat.  The Starfish and the Spider is a 2006 business management book by Ori Brafman and Rod Beckstrom; its title alludes to the ability of the starfish to regenerate itself because of its decentralized nervous system, and the book suggests ways that a decentralized organisation may flourish. Some live in the intertidal zone, between low and high tide. It is also often called as Spotted Linckia, Dalmatian Linckia or Multicolor Starfish. The left side of the larval body becomes the oral surface of the juvenile and the right side the aboral surface. Starfish can only survive in salty and brackish environments, therefore, you won’t find them in fresh water. Linckia Starfish (Linckia multifora) The Linckia starfish has many nicknames. Starfish have tube feet operated by a hydraulic system and a mouth at the centre of the oral or lower surface. These starfish make great display items for your beach theme room or craft project.they are very easy to paint or just leave natural.Sizes are not exact and sold in a rough range not exact and may possibly be slightly smaller or larger. Scientific Name. Some are alarm pheromones and escape-eliciting chemicals, the release of which trigger responses in conspecific starfish but often produce escape responses in potential prey. Royal StarfishOne of the most colorful types of starfish is the royal sea star. You probably know sea stars as starfish, the name sea stars are commonly known by. , Starfish may be preyed on by conspecifics, sea anemones, other starfish species, tritons, crabs, fish, gulls and sea otters. Linnaeus, 1758 Common Starfish Description Body with small disc and 5 rather short, broad and tapering arms (occasionally, specimens are found with 4, 6 or even 7-8 arms); R/r: mostly 4,5 (exceptionally 3,5-7), up to 520 mm in diameter (but usually smaller).Often coloured orange, but may vary between pale brown to violet. Echinaster, part of Valvatida, e.g. In the State of Florida, O. reticulatus is listed as endangered and its collection is illegal. The color is usually orange, often with a purple tint. Put the words together and it portrays the starfish for what they truly are.  Similar results were found in a 1971 study of Stichaster australis on the intertidal coast of the South Island of New Zealand. Experimental removals of this top predator from a stretch of shoreline resulted in lower species diversity and the eventual domination of Mytilus mussels, which were able to outcompete other organisms for space and resources. , The gut of a starfish occupies most of the disc and extends into the arms. Scientific name: Asterias rubens; Norwegian: vanlig korstroll; Characteristics: The five armed common starfish may reach a diameter of 52 cm. A syndrome known as sea star wasting disease causes the animal to lose limbs and eventually disintegrate, leaving behind a pile of white goo.  Pteraster militaris broods a few of its young and disperses the remaining eggs, that are too numerous to fit into its pouch. In others, the eggs may be stuck to the undersides of rocks.  Asterias amurensis is one of a few echinoderm invasive species. Different shades of brown is often seen as well. Only the ossicles and spines of the animal are likely to be preserved, making remains hard to locate. The first known asterozoans were the Somasteroidea, which exhibit characteristics of both groups. The color is usually orange, often with a purple tint. , The next stage in development is a brachiolaria larva and involves the growth of three short, additional arms. This is one of the largest and most frequently encountered sea stars along the Norwegian coast. Marine scientists have undertaken the difficult task of replacing the beloved starfishâs common name with sea star because, well, the starfish is not a fish. Fromia require a very long and slow acclimation period prior to introduction into the display aquarium. There are nearly 2,000 different species of starfish, all with their own unique names. Oxygen is transferred from these to the coelomic fluid, which acts as the transport medium for gasses. A set of radial canals leads off this; one radial canal runs along the ambulacral groove in each arm. The first individual of a species to spawn may release a pheromone that serves to attract other starfish to aggregate and to release their gametes synchronously. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. The class Asteroidea is named in reference to their star, or asteroid, shape. , The processes of feeding and capture may be aided by special parts; Pisaster brevispinus, the short-spined pisaster from the West Coast of America, can use a set of specialized tube feet to dig itself deep into the soft substrate to extract prey (usually clams). Fish have backbones, which makes them vertebrates. When the prey is a clam or other bivalve, the starfish pulls with its tube feet to separate the two valves slightly, and inserts a small section of its stomach, which releases enzymes to digest the prey.  The retraction and contraction of the cardiac stomach is activated by a neuropeptide known as NGFFYamide. Sea stars are typically only a few inches but … Asteroids have broad-based arms with skeletal support provided by calcareous plates in the body wall while ophiuroids have clearly demarcated slender arms strengthened by paired fused ossicles forming jointed "vertebrae". They have bony, calcified skin, which protects them from most predators, and many wear striking colors that camouflage them or scare off potential attackers. Another invagination of the surface will fuse with the tip of the archenteron as the mouth while the interior section will become the gut.  The developing young are called lecithotrophic because they obtain their nutrition from the yolk as opposed to "planktotrophic" larvae that feed in the water column. Here the food is passed on to the pyloric stomach, which always remains inside the disc. , There may also be papulae, thin-walled protrusions of the body cavity that reach through the body wall and extend into the surrounding water. There are usually two rows of tube feet but in some species, the lateral canals are alternately long and short and there appear to be four rows.  When a starfish finds itself upside down, two adjacent arms are bent backwards to provide support, the opposite arm is used to stamp the ground while the two remaining arms are raised on either side; finally the stamping arm is released as the starfish turns itself over and recovers its normal stance. Stichaster, Starfish are deuterostomes, closely related, together with all other echinoderms, to chordates, and are used in reproductive and developmental studies. , By the late Paleozoic, the crinoids and blastoids were the predominant echinoderms, and some limestones from this period are made almost entirely from fragments from these groups. Habitats range from tropical coral reefs, rocky shores, tidal pools, mud, and sand to kelp forests, seagrass meadows and the deep-sea floor down to at least 6,000 m (20,000 ft). The Asteroidea occupy several significant ecological roles. This type of tissue is called catch connective tissue and is found in most echinoderms. At the same time, a band of cilia develops on the exterior. Carrion Cactus, Carrion Flower, Starfish Cactus, Star Flower, Starfish Plant, Toad Cactus, Toad Plant  Starfish are vulnerable to high temperatures.  The loss of parts of the body is achieved by the rapid softening of a special type of connective tissue in response to nervous signals. Arms. These bulb-shaped organs are joined to tube feet (podia) on the exterior of the animal by short linking canals that pass through ossicles in the ambulacral groove. Aster means star while eidos means likeness.  The crown-of-thorns starfish consumes coral polyps, while other species are detritivores, feeding on decomposing organic material and faecal matter. During the last 6,000 years, divergence in the larval development of Cryptasterina hystera and Cryptasterina pentagona has taken place, the former adopting internal fertilization and brooding and the latter remaining a broadcast spawner. These are usually not distinguishable externally as the gonads cannot be seen, but their sex is apparent when they spawn. Some require the central body to be intact to regenerate, but a few species can grow an entirely new sea star just from a portion of a severed limb. Experiments have shown that the feeding and growth rates of P. ochraceus reduce greatly when their body temperatures rise above 23 °C (73 °F) and that they die when their temperature rises to 30 °C (86 °F). Some live in the intertidal zone, between low and high tide.  It is derived from the Greek aster, ἀστήρ (a star) and the Greek eidos, εἶδος (form, likeness, appearance). These are composed of pigmented epithelial cells that respond to light and are covered by a thick, transparent cuticle that both protects the ocelli and acts to focus light. The name of this structure came from its resemblance to a genus of stony corals called madreporite.  Starfish Prime was a high-altitude nuclear test conducted by the United States on 9 July 1962. The division of the starfish, either across its disc or at the base of the arm, is usually accompanied by a weakness in the structure that provides a fracture zone. The Classification of a Starfish! Using tiny, suction-cupped tube feet, they pry open clams or oysters, and their sack-like cardiac stomach emerges from their mouth and oozes inside the shell. There is a reason for those names, this species come in a wide variation of colours. Also, its mouth is present in the ventral side (at the near center), and eyes are located at the tips of the arms.  Grasping the shellfish, the starfish slowly pries open the prey's shell by wearing out its adductor muscle, and then inserts its everted stomach into the crack to digest the soft tissues. The tube feet latch on to surfaces and move in a wave, with one arm section attaching to the surface as another releases. , Although starfish do not have many well-defined sense organs, they are sensitive to touch, light, temperature, orientation and the status of the water around them. Most starfish have five arms that radiate from a central disc, but the number varies with the group. Which of these processes occurs depends on the genus.  In certain species of starfish, the females brood their eggs – either by simply enveloping them or by holding them in specialised structures. , The larvae of several species of starfish can reproduce asexually before they reach maturity. In particular, Oreaster reticulatus, with its easily accessed habitat and conspicuous coloration, is widely collected in the Caribbean. Archaster, Brisingida with part of Velatida, e.g. , The feeding activity of the omnivorous starfish Oreaster reticulatus on sandy and seagrass bottoms in the Virgin Islands appears to regulate the diversity, distribution and abundance of microorganisms. The Sunflower sea star (Pycnopodia helianthoides) is the largest: fully grown, its arm-span is about a metre. Create good names for games, profiles, brands or social networks. When she releases eggs into the water, he is induced to spawn. They presented a phylogenetic tree for the living Asteroidea only; using the traditional names of starfish orders where possible, and indicating "part of" otherwise, the phylogeny is shown below. 7.  Most starfish cannot move quickly, a typical speed being that of the leather star (Dermasterias imbricata), which can manage just 15 cm (6 in) in a minute. The dermis contains an endoskeleton of calcium carbonate components known as ossicles. Starfish Marine scientists have undertaken the difficult task of replacing the beloved starfish’s common name with sea star because, well, the starfish is not a fish. The aboral or upper surface may be smooth, granular or spiny, and is covered with overlapping plates.  The sensory component receives input from the sensory organs while the motor nerves control the tube feet and musculature. p35. Taxonomy. But sea stars aren’t really fish. It is characterized by …  Starfish species inhabit all of the world's oceans. Starfish. Many sea stars have five arms, … A short intestine and rectum run from the pyloric stomach to open at a small anus at the apex of the aboral surface of the disc. This is a great guide for identifying starfish you might encounter. , In his 2002 book The Divine Mystery Fort, Sri Sai Kaleshwar Swami wrote, "An eighth type of supernatural power object is a starfish.  In the World War II, Starfish sites were large-scale night-time decoys created during The Blitz to simulate burning British cities. Itâs an echinoderm, closely related to sea urchins and sand dollars. When fully developed, the brachiolaria settles on the seabed and attaches itself with a short stalk formed from the ventral arms and sucker. Echinoderms first appeared in the fossil record in the Cambrian. Most can regenerate damaged parts or lost arms and they can shed arms as a means of defense. Despite the their names individual of green, pink, and yellow colors also belong to this species , While a starfish lacks a centralized brain, it has a complex nervous system with a nerve ring around the mouth and a radial nerve running along the ambulacral region of each arm parallel to the radial canal. Nicknames, cool fonts, symbols and tags for Starfish – Pɪɴᴀᴘᴘʟᴇ, Stardust, Bubble, ραтяι¢к ♡︎, Coral, starburst. It can either be found in grey, brown or pink. The stomach and the partially digested prey are later retracted into the disc. Starfish are not actually a fish at all , but are animals belonging to the Phylum Echinodermata, and are further divided into two classes Asteroidea(sea stars) and Ophiuroidea(brittle stars). When Whale realized the trick he beat Starfish ragged, which is how Starfish still is today. The Scientific Name of Starfish and the Meaning. , An aboriginal Australian fable retold by the Welsh school headmaster William Jenkyn Thomas (1870–1959) tells how some animals needed a canoe to cross the ocean. The surface of the Linckia is rough. Caymanostella and part of Forcipulatida, e.g. They have five or more arms and can be quite large. This vessel has a blind end and there is no continuous circulation of the fluid within it. They are still quite sensitive to changes in pH, temperature, and salinity changes.  The Antarctic Labidiaster annulatus can have over fifty.  When such a larva senses that food is plentiful, it takes the path of asexual reproduction rather than normal development. The tube feet, especially those at the tips of the rays, are also sensitive to chemicals, enabling the starfish to detect odour sources such as food.  Starfish are sometimes eaten in China, Japan and in Micronesia. The entrance to this is known as the blastopore and it will later develop into the anus—together with chordates, echinoderms are deuterostomes, meaning the second (deutero) invagination becomes the mouth (stome); members of all other phyla are protostomes, and their first invagination becomes the mouth. These starfish engulf piles of sediment removing the surface films and algae adhering to the particles. In addition, foraging by these migratory starfish creates diverse patches of organic matter, which may play a role in the distribution and abundance of organisms such as fish, crabs and sea urchins that feed on the sediment. The mouth is located in the centre of the oral surface, where it is surrounded by a tough peristomial membrane and closed with a sphincter.  Research into the efficacy of these compounds for possible pharmacological or industrial use occurs worldwide.  Some starfish turn up the tips of their arms while moving which gives maximum exposure of the sensory tube feet and the eyespot to external stimuli. For other uses, see, "Asteroidea" redirects here. The surface of the Linckia is rough. Starfish can also grow to extremely large sizes- the Sunflower sea star (Pycnopodia helianthoides) is one of the largest starfishes in the world, reaching a maximum arm span of 3.3 ft. All the ossicles, including those projecting externally, are covered by the epidermal layer. , When longitudinal muscles in the ampullae contract, valves in the lateral canals close and water is forced into the tube feet. Got it? These are elongated, branched hollow tubes that are lined by a series of glands, which secrete digestive enzymes and absorb nutrients from the food. , The main nitrogenous waste product is ammonia. Despite their older common name, they are not fishes. 2020 National Geographic Partners, LLC.  There are eyespots at the ends of the arms, each one made of 80–200 simple ocelli. In Parvulastra parvivipara, an intragonadal brooder, the young starfish obtain nutrients by eating other eggs and embryos in the brood pouch. , Most species are generalist predators, eating microalgae, sponges, bivalves, snails and other small animals. For the Asteraceae subfamily, see, CS1 maint: DOI inactive as of October 2020 (, CS1 maint: multiple names: authors list (, list of the world's 100 worst invasive species, "Fossil Groups: Modern forms: Asteroids: Extant Orders of the Asteroidea", "Glossary of terms: Phylum Echinodermata", "Echinoderms don't suck: evidence against the involvement of suction in tube foot attachment", "Echinoderms have bilateral tendencies:PLoS One", "The natural history, life history and ecology of the two British species of, "Viviparity and intragonadal cannibalism in the diminutive sea stars, "Size at maturation, sex differences, and pair density during the mating season of the Indo-Pacific beach star, "Sexual reproduction and fission in the sea star, "Autotomy and regeneration of Hawaiian starfishes", "Multiple modes of asexual reproduction by tropical and subtropical sea star larvae: an unusual adaptation for genet dispersal and survival", "Effects of ionic environment on viscosity of catch connective tissue in holothurian body wall", "Purification and partial characterization of an autotomy-promoting factor from the sea star, "100 of the World's Worst Invasive Alien Species", "Densovirus associated with sea-star wasting disease and mass mortality", "An intertidal sea star adjusts thermal inertia to avoid extreme body temperatures", "Elevated water temperature and carbon dioxide concentration increase the growth of a keystone echinoderm", "Global diversity and phylogeny of the Asteroidea (Echinodermata)", "Extraordinarily rapid life-history divergence between, "Echinodermata: Spiny-skinned animals: sea urchins, starfish, and their allies", "Revision of the Atlantic Brisingida (Echinodermata: Asteroidea), with description of a new genus and family", "Phylogenomic analysis of echinoderm class relationships supports Asterozoa", "Use of sea stars to study basic reproductive processes", "Cytoskeletal dynamics and function in oocytes", "Starfish Shows Off Strange Ability To Expel Foreign Objects Through Skin". The interior of the whole canal system is lined with cilia. Many starfish also possess individual photoreceptor cells in other parts of their bodies and respond to light even when their eyespots are covered. Sea stars : Sea stars (or starfish) (scientific name Asteroidea) are a major group of the Echinoderms.There are about 2,000 species of sea stars living in the world's oceans in habitats from tropical coral reefs, kelp forests to the cold deep oceans (greater than 6 … , The starfish are a large and diverse class with about 1,500 living species. There may be good reason for this: the bodies of numerous species are dominated by bony ossicles, and the body wall of many species contains saponins, which have an unpleasant taste, and others contain tetrodotoxins which are poisonous. , Starfish sometimes have negative effects on ecosystems. Outbreaks of crown-of-thorns starfish have caused damage to coral reefs in Northeast Australia and French Polynesia. The peripheral nerve system consists of two nerve nets: a sensory system in the epidermis and a motor system in the lining of the coelomic cavity. There are short lateral canals branching off alternately to either side of the radial canal, each ending in an ampulla. A paper published in November 2014 revealed the most likely cause of this disease to be a densovirus the authors named sea star-associated densovirus (SSaDV). Got it? Starfish. Fertilization is generally external but in a few species, internal fertilization takes place. Linckia Starfish (Linckia multifora) The Linckia starfish has many nicknames. Some waste may also be excreted by the pyloric glands and voided with the faeces. , Most species of starfish are gonochorous, there being separate male and female individuals.  In 2011, on further molecular evidence, Janies and colleagues noted that the phylogeny of the echinoderms "has proven difficult", and that "the overall phylogeny of extant echinoderms remains sensitive to the choice of analytical methods". Debris Expansion Experiment", https://en.wikipedia.org/w/index.php?title=Starfish&oldid=983894900, Taxa named by Henri Marie Ducrotay de Blainville, CS1 maint: DOI inactive as of October 2020, Wikipedia indefinitely semi-protected pages, Creative Commons Attribution-ShareAlike License, This page was last edited on 16 October 2020, at 22:02. Others are antifoulants and supplement the pedicellariae to prevent other organisms from settling on the starfish's aboral surface. Starfish belong to the class Asteroidea, derived from the Greek words “aster” (a star) and “eidos“ (form, likeness, appearance). They accomplish this by housing most or all of their vital organs in their arms. For example, Leptasterias hexactis broods a small number of large-yolked eggs. The heart beats about six times a minute and is at the apex of a vertical channel (the axial vessel) that connects the three rings. Several species have specialized feeding behaviours including eversion of their stomachs and suspension feeding. , Most starfish embryos hatch at the blastula stage. What do starfish eat? Kingdom: Animalia Phylum: Echinodermata Subphylum: Asterozoa Class: Asteroidea Order : Phanaerozonia Family: Ophidiasteridae Genus: Asterias  Starfish may use environmental signals to coordinate the time of spawning (day length to indicate the correct time of the year, dawn or dusk to indicate the correct time of day), and chemical signals to indicate their readiness to breed. Female starfish produce large numbers of oocytes that are easily isolated; these can be stored in a pre-meiosis phase and stimulated to complete division by the use of 1-methyladenine. The five-arm varieties are the most common, hence their name, but species with 10, 20, and even 40 arms exist. Orbea variegata (L.) Haw.. Common Names. , Primitive starfish, such as Astropecten and Luidia, swallow their prey whole, and start to digest it in their cardiac stomachs. Belonging to the family Asteriidae, it has five arms and usually grows to between 10–30 cm across, although larger specimens (up to 52 cm across) are known. Kingdom: Animalia. The tube feet, spines and pedicellariae are sensitive to touch.  Other species protect their vulnerable tube feet and arm tips by lining their ambulacral grooves with spines and heavily plating their extremities. You probably know sea stars as starfish, the name sea stars are commonly known by. Despite this, there are a few places where accumulations of complete skeletal structures occur, fossilized in place in Lagerstätten – so-called "starfish beds". You can use it as your own power object. Scientific Name: Astropecten polyacanthus : Reef Compatible: Yes : Care Level: Beginner : Disposition: Peaceful : Minimum Tank Size: 30 gallons : Mature Size: 12 inches  In more advanced species of starfish, the cardiac stomach can be everted from the organism's body to engulf and digest food. Its larvae likely arrived in Tasmania from central Japan via water discharged from ships in the 1980s.  Asterina pectinifera, used as a model organism for this purpose, is resilient and easy to breed and maintain in the laboratory. The tropical crown-of-thorns starfish (Acanthaster planci) is a voracious predator of coral throughout the Indo-Pacific region, and the northern Pacific sea star is considered to be one of the world's 100 worst invasive species. When these grow large enough they change back into females.  Other chemicals and relaxation of the ampullae allow for release from the substrate. , Starfish is the title of novels by Peter Watts and Jennie Orbell, and in 2012, Alice Addison wrote a non-fiction book titled "Starfish - A year in the life of bereavement and depression". Purely marine animals, there are no freshwater sea stars, and only a few live in brackish water. As well as the starfish, the echinoderms include sea urchins, sand dollars, brittle and basket stars, sea cucumbers and crinoids. Although some species can tolerate relatively low salinity, the lack of an osmoregulation system probably explains why starfish are not found in fresh water or even in many estuarine environments. Their relatively large sizes, diverse diets and ability to adapt to different environments makes them ecologically important. As such, they are considered pests, and are on the Invasive Species Specialist Group's list of the world's 100 worst invasive species. Despite this, there are a few places where accumulations of complete skeletal structures occur, fossilized in place in Lagerstätten – so-called "starfish beds". They often form clusters surrounding spines. Starfish belong to the class Asteroidea, derived from the Greek words “aster” (a star) and “eidos“ (form, likeness, appearance). Some of these species are grazers, but others trap food particles from the water in sticky mucus strands that are swept towards the mouth along ciliated grooves. The water vascular system serves to transport oxygen from, and carbon dioxide to, the tube feet and also nutrients from the gut to the muscles involved in locomotion.  Gas exchange also takes place through other gills known as papulae, which are thin-walled bulges on the aboral surface of the disc and arms. Most starfish species prefer to live at roughly 6,000 meters deep, although some can also be found inhabiting sandy beds on ocean coasts.  This species has a unique ability to absorb seawater to keep itself cool when it is exposed to sunlight by a receding tide. , Several species sometimes suffer from a wasting condition caused by bacteria in the genus Vibrio; however, a more widespread wasting disease, causing mass mortalities among starfish, appears sporadically. Starfish are animals.  In temperate regions, the spring and summer brings an increase in food supplies. This website is dedicated to the appreciation of Royal Sea Star (starfish). They are found from the intertidal zone down to abyssal depths, 6,000 m (20,000 ft) below the surface. This is a great guide for identifying starfish you might encounter. , The lifespan of a starfish varies considerably between species, generally being longer in larger forms and in those with planktonic larvae.  Starfish oocytes are well suited for this research as they are large and easy to handle, transparent, simple to maintain in sea water at room temperature, and they develop rapidly. The cilia are used for locomotion and feeding, their rhythmic beat wafting phytoplankton towards the mouth.  A 2012 study found that speciation in starfish can occur rapidly. They vary between species and are typically formed from up to six sugar molecules (usually glucose and galactose) connected by up to three glycosidic chains. The cardiac stomach is glandular and pouched, and is supported by ligaments attached to ossicles in the arms so it can be pulled back into position after it has been everted.