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Fossil Museum 2012

Created By: Sarah Butler
http://www.fossilmuseum.net/Tree_of_Life/Phylum-Echinodermata.htm 

The Echinodermata, (from the Greek meaning spiny skin), is a phylum containing some 13,000 extinct and 7,000 extant species. Living representatives are only found in marine environment, making the phylum the largest lacking terrestrial and fresh water forms. Echinoderms evolved from bilaterally symmetric animals exhibiting fivefold radial symmetry in portions of their body at some stage of life. This pentameral symmetry is readily apparent in familiar adult starfish and sand dollars. Other echinoderms both extant and extinct lack the five point morphology because it was lost somewhere during development (i.e., during ontogeny).
Echinoderms have a vascular system that carries water and which in some echinoderms end in suckered feet enabling the creature to grip and move objects. Reproduction in Echinoderms reproduction is usually via external fertilization through eggs and sperm discharged into the water, and the majority of echinoderms have several planktonic larval stages before reverting to a sessile existence on the seafloor.

Since most echinoderms have some type of calcareous support exoskeleton (actually often interlocking plates of calcium carbonate), [17] there exists an extensive fossil record tracing echinoderm evolution. Yet, many aspects of their early evolutionary origins are confounded, such that the classification table below is but one of many interpretations to be found in the literature. Importantly, the Echinodermata phylogenetic relationship to other phyla is poorly understood because they were already well differentiated by the Cambrian, and their unique characteristics are not present in other groups. While echinoderms are known from the Cambrian on, the Vendian period has a few soft-bodied fossils that are putative echinoderms or their ancestors. These include Arkarua and Tribrachidium from the Ediacara Hills of Australia. Homalozoans, from which echinoderm may have descended, and eocrinoids, that are not directly ancestral to the true crinoids, are abundant in the early Cambrian fossil record.

A possible early crinoid is Echmatocrinus from the famous Burgess Shale of the middle Cambrian, though many researchers doubt it was a true crinoid. Cotyledion from the much younger early Cambrian Chengjiang Maotianshan Shale is another potential primitive crinoid. Other Cambrian echinoderms included the unusual helicoplacoids. Asterozoans (starfish and brittle stars) appeared in the Ordovician, as did the earliest echinozoans. The oldest asterozoans (the Somasteroidea) have morphological similarities to both starfish and brittle stars, supporting the theory that [18] starfish and brittle stars probably diverged from a common somasteroid ancestor. After the Ordovician, there is an extensive echinoderm fossil record dominated by crinoids and blastoids; such as this stunning Triacrinus crinoid death assemblage from the Devonian Hunsruck Slates near Bundenbach, Germany. Some Paleozoic limestone formations are comprised of almost nothing other than crinoid and blastoid pieces. All the blastoids and most of the crinoids met extinction at the end of the Permian, leaving only the Asterozoans and echinozoans that remain extant today. The Holothurians, or sea cucumbers, are prevalent echinoderms but are extremely rarely fossilized.

[20]  Complete fossil starfish are also very rare, and often are but partial plates or segments of arms. The [19] poor fossilization results because the skeleton is not ridged like echinoids (sea urchins), but comprised of numerous small plates (or ossicles) that quickly fall apart after decay of the soft parts of the animal.

Great fields (so to speak) of crinoid gardens inhabited shallower waters during the Paleozoic, essentially from the Ordovician on, and particularly in the Carboniferous (for example, see the famous Crawfordsville crinoids). However, crinoids suffered a major crisis during the Permian period (the P-T even) when most met extinction, with but few survivors into the Triassic period. The Mesozoic era realized another large crinoid radiation, with more modern forms having flexible arms becoming widespread. After another extinction event at the end of the Cenozoic they again declined, with most remaining species constrained to deep waters until present time.
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Bourton 2009

Created By: Sarah Butler
http://news.bbc.co.uk/earth/hi/earth_news/newsid_8328000/8328311.stm

One starfish has a remarkable strategy to avoid overheating in the sun, scientists have discovered.

The starfish [9] pumps itself up with cold seawater to lower its body temperature when exposed to the sun at low tide.

It is equivalent to a person drinking seven litres of water before heading into the midday sun, scientists say.

However, global climate change may drastically interfere with this vital mechanism by increasing sea temperatures, the researchers warn.

The ochre starfish or sea star (Pisaster ochraceus) is found in the intertidal zone along the Pacific North American coast. 
 
 
 It mainly feeds on mussels while underwater. During low tide it is exposed to the air and cannot move until it is submerged again at high tide.

When exposed to the warm sun at low tide, the ochre starfish can suffer heat stress.

Now scientists based in California, US reveal how it manages this excess heat in the journal American Naturalist.

Pump up the volume

"We have discovered a quite novel thermoregulation strategy in the animal kingdom," says Dr Sylvain Pincebourde, formerly of the University of South Carolina, Columbia but now at the François Rabelais University in Tours, France.

"We found that the weight of the sea stars increased during the days after exposure to high temperature at low tide."

"The sea stars were not allowed to feed. So this increase can be explained only by an increase in seawater uptake. When sucking up water, the body mass of a sea star increases," he says.

The increase in body mass allows the starfish to be buffered against environmental temperature changes in the subsequent low tide.

"Because its body mass is now higher, body temperature increases more slowly," Dr Pincebourde explains.

"The thermoregulatory strategy we have revealed in our study indicates that the sea star is well adapted to such a variable environment."
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Planet 2012

Created By: Sarah Butler
http://animals.howstuffworks.com/marine-life/starfish-info.htm

Starfish, or Sea Star, a bottom-dwelling marine animal. Despite its name, the starfish is not a fish; it is an echinoderm, a type of marine animal that is spiny-skinned. There are about 2,000 species, found in all seas, and most often near rocky shores. Starfish typically have five or more tapering arms radiating from a central point. The mouth is in the center on the underside. Extending from the mouth to the tip of each arm are grooves lined with tubelike feet. In certain species, the feet have suction disks. The starfish uses its feet to crawl along the ocean bottom. When an arm is lost, a new one soon grows in its place. Most starfish are brightly colored; red, orange, yellow, and pink are common colors. They vary in size from less than 1/2 inch (13 mm) across to more than four feet (1.2 m).
Starfish typically have five or more arms.
Starfish feed mainly on such invertebrates as coral and shellfish, especially clams and oysters. Starfish with suction disks use them to hold and force open the shells of shellfish. Once it has opened a shell, the starfish extends its stomach membranes from its mouth, inserts them into the shell opening, and secretes digestive juices that break down the shellfish's body into a form that can be absorbed into the stomach membranes. Starfish without suction disks swallow their prey whole, and eject the parts that are not digestible. Starfish are not eaten by humans.

What Makes a Sea Star an Echinoderm?

Unlike fish, sea stars don’t have backbones. Instead, sea stars and their relatives have hard plates under their skin. Some of these hard plates have spines. That’s one reason a sea star is an echinoderm.

The sea star’s center is round. Arms grow out from the center—like spokes in a wheel. The body of an adult sea star has several nearly identical sections. It can be divided into similar pieces—like the slices of a pie. Some other echinoderms have other shapes. Some look like balls. Others look like barrels. But they even have bodies with many similar sections.

Like all echinoderms, sea stars have a system of tiny tubes inside their bodies. The tubes extend outside the animal’s body. The closed tips of these tubes are called tube feet. Sea stars have rows upon rows of tube feet—as do most other echinoderms.

How Does a Sea Star Use Its Spines?

A sea star’s spines are sharp. If eaten, they can make for a very painful meal. That’s why many predators avoid sea stars. Still, a few animals—such as king crabs, sea otters, and gulls—eat sea stars. Somehow, they seem to be able to handle the sea star’s spines and bony plates.

The sea star called the crown-of-thorns has spines all over the top of its body. Like other sea stars, it also has shorter spines on its underside. Those spines lie along the rows of tube feet. If the sea star is in danger, it can close the spines together to protect its soft feet.

Sea stars use their spines for protection. Some sea stars also have tiny pinchers in between the spines on top of their bodies. These sea stars use their pinchers to snap at intruders. They can also use their pinchers to clean the sand off their bodies.

Where Is a Sea Star’s Head?

A sea star has no head. It has no brain either. But a sea star doesn’t need a brain to sense what is going on around it. Special cells on the sea star’s skin gather information about its surroundings. These cells then send signals through a network of nerves inside the sea star’s body. These signals trigger the animal to take some kind of action, such as to turn or to crawl.

A sea star also has another kind of network inside its body—a network of tubes. Tiny tubes extend from a sea star’s center to the tip of each of its arms. These tubes carry seawater throughout the animal’s body. A sea star uses the network of tubes to move its tube feet.

A sea star’s mouth is on the underside of the animal’s round center. The mouth leads directly to a large, baglike stomach. The sharp spines found all over the sea star’s body also surround its mouth. These spines help protect a sea star’s soft insides.

The Daily Starfish 
What Do Sea Stars Eat?

Many sea stars are carnivores (kahr nuh vawrz). That means they eat meat. Some sea stars prefer to eat animals such as mussels, clams, and oysters. Others like to eat snails, sponges, sea anemones (uh NEHM uh neez), coral, or other sea stars. And some will eat any kind of small animal they can get.

Some sea stars eat in a most amazing way. First, the sea stars use their arms to force open clams or oysters. Then the sea stars push their stomachs out through their mouths and into the open shells. They digest the soft bodies of their prey this way.

Other sea stars swallow their prey whole—shells and all. The sea stars don’t use the shells as food. So, once the sea stars eat the rest of the prey, they pass the empty shells back out through their mouths.

How Do Sea Stars Find Food?

Sea stars can “smell” food in the water. But, of course, they don’t use noses to do this smelling. Sea stars don’t even have noses. Instead, they use their skin. Sea stars have sensitive cells on their skin. Some of these cells can detect chemicals in the water that come from food. Some sea stars can also “smell” food with their tube feet.

Once a sea star detects food, it can move toward its prey. But a sea star isn’t going to win many races. Normally, a sea star crawls very slowly—less than 1 foot (30 centimeters) in a minute. When it is “chasing” prey, it can speed up. Then it may be able to crawl 2 1/2 feet (76 centimeters) in a minute.

Can Sea Stars See?

Sea stars do not have eyes as people do. But, they do have eyespots. These spots are groups of cells that can detect light. Sea stars have these eyespots at the tips of their arms.

Eyespots help a sea star survive. When a sea star senses light from above, it can tell which way is up. And if something suddenly blocks the light, the sea star senses that an enemy may be nearby.

Eyespots also help a sea star when it’s out of water. A sea star may end up on the beach at low tide. If it stays in the sun too long, its body may dry out. That would cause the sea star to die. With its eyespots, the sea star can find its way to shade. In the shade, the sea star can stay cool and damp until the water level rises again at high tide.

How Many Arms Does a Sea Star Have?

Most sea stars have 5 arms each. But some have as many as 40 arms. The number of arms sea stars have often is a multiple of 5—5, 10, 15, 20, and so on. Why do sea stars have so many arms? With arms on all sides, sea stars can react in almost any direction to their surroundings. This helps keep sea stars safe.

A sea star also has special sense cells all over its body. For a sea star, this is better than having a head with a brain, nose, and eyes. With sense cells getting signals from everywhere, a sea star can readily detect predators nearby. The sense cells also help a sea star find food.

Can Sea Stars Really Grow New Arms?

Yes, they can! [12] Sea stars are always in danger of losing arms, so being able to grow new ones is important to them. Sometimes predators bite the arms of sea stars. Sometimes rocks fall and crush them.

A few species of sea stars are so good at growing new arms that a cut-off arm can grow into a whole new sea star. The sea star you see here is actually growing four new arms. It is going through a process called regeneration (rih jehn uh RAY shuhn). Regeneration means replacing a body part with a new one. The process of regeneration doesn’t happen overnight, though. It can take up to a year for a sea star to replace missing parts.

How Many Feet Does a Sea Star Have?

A sea star has hundreds of tube feet. But these feet don’t look like your feet. You can see them on the underside of the animal’s body. Find the groove that runs down the middle of each arm. The sea star’s tube feet are in these grooves.

A sea star uses its tube feet for walking, clinging, and grabbing food. Some sea stars have tube feet that can grip like suction cups. Here’s how that works. First, seawater enters the sea star through a hole on top of its body. The water then flows through the tube system and into the tube feet. The water causes the tube foot to lengthen and spread out. When the foot is pressed against a hard surface, it shrinks. This helps the tube foot stick. Then the sea star releases a substance like glue from its foot.

When the sea star is ready to let go, it stretches its foot out again. It releases another substance. This new substance stops the glue from sticking.

How Are Sea Stars Born?

Female sea stars make eggs. Male sea stars produce sperm. The females release their eggs about the same time that the males send clouds of sperm into the water. The sperm fertilizes the eggs. The fertilized eggs hatch into larvae (LAHR vee).

Sea star larvae are not much bigger than pinheads. The larvae float in the water, going wherever water currents carry them. Over time, the larvae change into many odd-looking shapes. As they grow, the larvae sink to the ocean floor. There, they eventually become adult sea stars.

Do Sea Stars Care for Their Young?

Most sea stars do not care for their young. The females just release their eggs into the water. The larvae grow up on their own. Fish and other animals eat many of them. However, many females produce millions of eggs at a time. This makes it very likely that some of their young will survive.

In some species of sea stars, females do care for their young. Those mothers protect their eggs beneath their bodies. When the eggs hatch, the mothers guard the larvae until they are big enough to go off on their own.

Female sea stars that hold onto their young produce fewer eggs than those that don’t. These kinds of sea stars release only about a few hundred eggs at a time. But many of the larvae will live to be adults.

Which Sea Star Looks Good Enough to Eat?

The chocolate chip sea star may look good enough to eat, but it isn’t. That’s because it is very spiny. So, despite its name, this sea star is not a snack.

The chocolate chip sea star is covered with brown spines. But having spiny skin isn’t the only reason sea stars aren’t good food. Some of these echinoderms are poisonous. The crown-of-thorns sea star, for example, can harm even humans who touch its long spines. A sting from one of these sea stars can be very painful. A victim may lose feeling at the site of the sting.

Who Stands Out in the Sea Star Family?

You can’t always divide the number of arms a sunflower sea star has by 5. And a sunflower sea star may grow up to 24 arms. The older a sunflower sea star gets, the more arms it grows. This echinoderm grows to 3 feet (90 centimeters) across. That makes it one of the biggest sea stars in the world. This big sea star has a very large appetite. And it is not a picky eater. The sunflower sea star likes clams, mussels, and snails. It also eats other echinoderms, such as sea urchins, sea cucumbers, and other sea stars. The sunflower sea star often swallows its food whole.

Is the Leather Sea Star Made of Leather?

No, it isn’t, but the leather sea star feels as if it is. This colorful sea star lives among rocks in intertidal zones. Unlike most other sea stars, a leather sea star’s spines do not stick out from below its skin. Because of this, its skin feels smooth and leathery to the touch.

A leather sea star isn’t prickly to the touch, but it sure is slippery. This sea star releases mucus over much of its body. And this sea star isn’t just slimy—it’s also smelly. Some people think it gives off a smell just like garlic.Leather sea stars come in a variety of colors. Besides the colors you see here, these sea stars may also have gold, blue, and red on them.

Starfish make up the class Asteroidea of the phylum Echinodermata.
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Zubi 2010

Created By: Sarah Butler
http://www.starfish.ch/reef/echinoderms.html(Echinodermata) 

There are 5 related classes in the phylum Echinodermata (the Latin name means "spiny-skinned"). For a detailed list with all classifications click here:

Sea star or starfish (Asteroidea)
Brittle stars, basket stars, serpent stars (Ophiuroidea)
Sea urchins, heart urchins and sanddollars (Echinoidea)
Holothurians or sea cucumbers (Holothuroidea)
Feather stars and sea lilies (Crinoidea).
Characteristics of Echinoderms
Echinoderms are characterized by radial symmetry, several arms (5 or more, mostly grouped 2 left - 1 middle - 2 right) radiating from a central body (= pentamerous). The body actually consists of five equal segments, each containing a duplicate set of various internal organs. They have no heart, brain, nor eyes, but some brittle stars seem to have light sensitive parts on their arms. Their mouth is situated on the underside and their anus on top (except feather stars, sea cucumbers and some urchins).

Echinoderms have tentacle-like structures called tube feet with suction pads situated at their extremities. These tube feet are hydraulically controlled by a remarkable vascular system. This system supplies water through canals of small muscular tubes to the tube feet (= ambulacral feet). As the tube feet press against a moving object, water is withdrawn from them, resulting in a suction effect. When water returns to the canals, suction is released. The resulting locomotion is generally very slow.

Ecology and range of Echinoderms
Echinoderms are exclusively marine. They occur in various habitats from the intertidal zone down to the bottom of the deep sea trenches and from sand to rubble to coral reefs and in cold and tropical seas.

Behavior of Echinoderms
Some echinoderms are carnivorous (for example starfish) others are detritus foragers (for example some sea cucumbers) or planktonic feeders (for example basket stars).

Reproduction is carried out by the release of sperm and eggs into the water. Most species produce pelagic (= free floating) planktonic larvae which feed on plankton. These larvae are bilaterally symmetrical, unlike their parents (illustration of a larvae of a sea star below). When they settle to the bottom they change to the typical echinoderm features.



Echinoderms can regenerate missing limbs, arms, spines - even intestines (for example sea cucumbers). Some brittle stars and sea stars can reproduce asexually by breaking a ray or arm or by deliberately splitting the body in half. Each half then becomes a whole new animal.

Echinoderms are protected through their spiny skins and spines. But they are still preyed upon by shells (like the triton shell), some fish (like the trigger fish), crabs and shrimps and by other echinoderms like starfish which are carnivorous. Many echinoderms only show themselves at night (= nocturnal), therefore reducing the threat from the day time predators.

[6] Echinoderms serve as hosts to a large variety of symbiotic organisms including shrimps, crabs, worms, snails and even fishes.



Sea stars (starfish)
(Asteroidea)

Characteristics of sea stars (or starfish)
Sea stars are characterized by radial symmetry, several arms (5 or multiplied by 5) radiating from a central body. Mouth and anus are close together on the underside, the anus is at the center of the disc together with the water intake (madreporite). The upper surface is often very colorful. Minute pincer-like structures called pedicellaria are present. These structures ensure that the surface of the arms stay free from algae. The underside is often a lighter color.

There are a few starfish that have 6 or 7 arms, for example Echinaster luzonicus or Protoreaster, some even more like the elven-armed sea star (Coscinasterias calamaria). Others normally have 5 arms but now have more arms, because after an injury an arm divided and grew into two arms.

Ecology and range or sea stars
The starfish lives everywhere in the coral reef and on sand or rocks.

Behavior of sea stars
Regeneration
The ability of an organism to grow a body part that has been lost

Autotomy
The spontaneous self amputation of an appendage when the organism is injured or under attack. The autotomized part is usually regenerated.

Budding
Is asexual reproduction in which an outgrowth on the parent organism breaks off to form a new individual

Fission
Self-division into two parts, each of which then becomes a separate and independent organisms (asexual reproduction)



The majority of sea stars are carnivorous and feed on sponges, bryozoans, ascidians and molluscs. Other starfishes are detritus feeders (detritus = organically enriched film that covers rocks) or scavengers. Some starfish are specialized feeders, for example the crown-of-thorns that feeds on life coral polyps.

Starfish have no hard mouth parts to help them capture prey. The stomach is extruded over the prey, thus surrounding the soft parts with the digestive organs. Digestive juices are secreted and the tissue of the prey liquefied. The digested food mass, together with the stomach is then sucked back in. This method can be observed, if you turn around a starfish, that sits on prey or sand - you will see the stomach retreating.

Starfish are well known for their powers of regeneration. A complete new animal can grow from a small fragment such as a arm. In some species (Linckia multifora and Echinaster luzonicus) one of the arms will virtually pull itself away, regenerates and forms a new animal. Autotomy (self amputation) usually is a protective function, losing the body part to escape a predator rather than being eaten. But here it serves as a form of asexual reproduction. In other species of sea stars (Allostichaster polyplax and Coscinasterias calamaria) the body is broken into unequal parts (= fission) then the missing limbs regenerate. 

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Morelle 2010

Created By: Sarah Butler
http://www.bbc.co.uk/news/science-environment-11931039

Lurking in the seas of Scotland is an unlikely candidate for a medical breakthrough.

But scientists believe the [13] starfish could hold the key to finding a new treatment for inflammatory conditions such as asthma, hay fever and arthritis.

The species they are interested in is the spiny starfish (Marthasterias glacialis), and in particular the [14] slimy goo that covers its body.

The team says that chemicals in this coating could inspire new medicines.

The spiny starfish can be found on the west coast of Scotland
While most man-made structures that are placed in the water rapidly get caked with a mixture of marine life, starfish manage to keep their surface clear.

Dr Charlie Bavington, from GlycoMar, a marine biotechnology company based at the Scottish Association for Marine Science in Oban, [15] explained: "Starfish live in the sea, and are bathed in a solution of bacteria, larvae, viruses and all sorts of things that are looking for somewhere to live. 


"But starfish are better than Teflon: they have a very [16]  efficient anti-fouling surface that prevents things from sticking."

And it is this non-stick property that has grabbed medical scientists' attention, particularly in the field of inflammation.

Sticky problem

Inflammation is the body's natural response to an injury or infection, but inflammatory conditions are caused when the immune system begins to rage out of control.

White blood cells, which normally flow easily through our blood vessels, begin to build up and stick to the blood vessel wall, and this can cause tissue damage.

Advertisement
Dr Charlie Bavington shows how starfish slime is produced
The idea is that a treatment based on starfish slime could effectively coat our blood vessels in the same way the goo covers the marine creature, and prevent this problem.

Dr Bavington said: "It is a very similar situation to something sticking to a starfish in the sea.

"These cells have to stick from a flowing medium to a blood vessel wall, so we thought we could learn something from how starfish prevent this so we could find a way to prevent this in humans."

While many inflammatory conditions can be effectively treated, for example with steroids, these drugs can often cause unwanted side effects.

Continue reading the main story

Start Quote
We are learning all the time from nature about how to find new medicines”
End Quote
Professor Clive Page

KCL

But scientists at King's College London (KCL) think starfish could offer a better solution, and they have been analysing the chemicals in the creature's non-stick slime.

Clive Page, professor of pharmacology at KCL, said: "The starfish have effectively done a lot of the hard work for us.

"Normally when you are trying to find a new drug to go after a particular target in human beings, you have to screen hundreds of molecules to find something that will give you a lead.

"The starfish is effectively providing us with something that is giving is different leads: it has had billions of years in evolution to come up with molecules that do specific things."

Having identified promising compounds, the team is now working on creating their own versions of them in the laboratory. They want to create a treatment that is inspired by starfish goo rather than one that is made from it.

Professor Page said: "Conceptually we know this is the right approach.

"It's not going to happen tomorrow afternoon, but we are learning all the time from nature about how to find new medicines."

Underwater pharmacy

While the starfish-based cure might be some years off, the race to explore the oceans for its medical potential is only just beginning.

Starfish could be one of many marine creatures to inspire new medicines
A sea snail has already formed the basis of a new painkiller, and scientists are starting to look at a whole range of marine life, from sea cucumbers to seaweed.

Dr David Hughes, an ecologist from the Scottish Association for Marine Science, explained: "Some of the most widespread, widely used medicines come from nature.

"Penicillin is a mould that grows on bread, aspirin comes from willow trees, so it's not too surprising turning to nature to find useful drugs. But we've only very recently begun to look to the sea for a useful source of medicines."

And with the oceans covering nearly three quarters of the Earth's surface, scientists have likened the deep to an untapped underwater pharmacy.

Dr Hughes told the BBC: "There is such a huge diversity of animals and plants living in the oceans and very few of them have been tested and investigated in any way.

"We know marine animals and plants produce a huge range of compounds, sometimes very different compounds from those produced by animals and plants on land.

"So many might have useful properties that could be brought into medicine and other medicinal applications."
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Doubilet 2012

Created By: Sarah Butler
http://animals.nationalgeographic.com/animals/invertebrates/starfish/

Sea stars are purely marine animals, even using [2] sea water instead of blood to pump nutrients throughout their bodies. 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. It’s an echinoderm, closely related to sea urchins and sand dollars.

There are some 2,000 species of sea star living in all the world’s oceans, from [1] tropical habitats to the cold seafloor. The five-arm varieties are the most common, hence their name, but species with 10, 20, and even 40 arms exist.

They have bony, calcified skin, which protects them from most predators, and many wear striking colors that camouflage them or scare off potential attackers. Purely marine animals, there are no freshwater sea stars, and only a few live in brackish water.

Beyond their distinctive shape, sea stars are famous for their ability to regenerate limbs, and in some cases, entire bodies. They accomplish this by housing most or all of their vital organs in their arms. 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.

Most sea stars also have the remarkable ability to consume prey outside their bodies. 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. The stomach then envelops the prey to digest it, and finally withdraws back into the body.
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