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Various echinoderms, starfish at the top left, hairy stars at the top right, a sea urchin in the middle right, sea rollers at the bottom right and brittle stars at the bottom left.

Various echinoderms, starfish at the top left , hairy stars at the top right , a sea ​​urchin in the middle right , sea ​​rollers at the bottom right and serpentine stars at the bottom left .

without rank: Holozoa
without rank: Multicellular animals (Metazoa)
without rank: Tissue animals (Eumetazoa)
without rank: Bilateria
Over trunk : Neumünder (Deuterostomia)
Trunk : Echinoderms
Scientific name
Bruguière , 1791 [ex Klein , 1734]

The echinoderms ( Echinodermata ) (from Greek ἐχῖνος echinos "hedgehog" and δέρμα derma "skin") are an animal strain belonging to the deuterostomians . About 6300 recent species of echinoderms are known worldwide , making them the second largest group of animals within the new mouth animals (deuterostomia) after the chordates (chordata).

They are consistently sea ​​creatures that, with the exception of a few deep-sea species, are pure bottom dwellers - i. H. live mainly in the shallow sea . In addition to their widespread distribution, they are also of geological importance because their dead shells and skeletal parts contribute significantly to the formation of limestone . If one type of skeleton predominates, they are given names such as trochitic or crinoid limestone , which can be found in the limestone Alps , among other places . In terms of quantity, however, the deposits of the tiny, floating calcareous algae predominate .

The Echinodermata are traditionally divided into the mostly stalked Pelmatozoa and the free-living Eleutherozoa . The Pelmatozoa include several taxa grouped as " sea ​​lilies " as well as the secondary free- living hair stars (Crinoidea). The Eleutherozoa include the more well-known groups of echinoderms: the starfish (Asteroidea) and brittle stars (Ophiuroidea), the sea urchins (Echinoidea) and cucumbers (Holothuroidea). The sea ​​daisies (Concentricycloidea), identified as a further class since 1986, are now placed among the starfish.

general characteristics

Most echinoderms reach sizes less than ten centimeters in length or in diameter. However, there are also very large species. For example, some sea rollers can reach lengths of up to two meters and some starfish have a diameter of up to one meter. The largest echinoderms were some extinct species of sea ​​lily with trunk lengths of up to 20 meters. In terms of body shape, star-shaped animals predominate with the sea and brittle stars . The sea urchins mostly have a spherical shape, which, like the sand dollars, can also be flattened, in addition to which they often have very differently shaped spines. The sea rollers have an elongated, sometimes almost worm-shaped shape. The sea lilies, in turn, represent sessile animals (grown on the ground) with a body equipped with many legs sitting on a long handle and filtering food particles from the water.

The spines, which give it its name and are so diverse, are articulated, flexible hollow forms that have grown out of the skeleton and are covered with an epidermis . They have several important functions: Above all, they serve to protect the animals from predators, as well as for digging, for fixing on the seabed and for locomotion. The spines can contain poisons (as in sea urchins) and also sensory organs - for example photoreceptors in starfish. As a special form of special pedicellariums , they can even be used to eliminate parasites or to catch prey.


Although the echinoderms belong to the bilateria and thus to the bilaterally symmetrical animals, a form of symmetry has developed in them that is based on five axes of symmetry (secondary pentamerism or five-ray radial symmetry ). This is particularly clear in the five-armed starfish, but can also be found in all other representatives of the animal group. With many Pelmatozoa and also with some starfish the five-pointedness is multiplied, so that starfish like Heliaster spec. Can have 50 arms, sea carnations like Comanthina schlegelii even 200. These symmetry properties only develop in the course of individual development ( ontogenesis ), which begins with a bilaterally symmetrical larva. The center of symmetry is formed by five radii that contain a canal system and radial nerves. The interradia are located between these.

At the same time, the mouth and anus also migrate from the former front and rear ends of the animals to the top and bottom. In the free-living Eleutherozoa, the mouth opening is on the underside of the animals (oral side) on the substrate, the anal opening correspondingly on the upper side (aboral side). In the case of the sea whales, a front and a rear pole with mouth and anus were formed again as a result of the stretching, but these correspond to the top and bottom of other echinoderms (the sea whales are on their side). With sea lilies, both the mouth and the anus are turned away from the substrate and lie next to each other.

The symmetry is broken by the madrepor or sieve plate. This lies on the aboral side next to the anus in an interradius. This plate defines the nomenclature of the body as a visible point, the radius opposite to it is called radius A and all subsequent ones are named from B to E in a clockwise direction. The Madreporenplatte thus always lies in the interradius CD.

Outer skin and calcareous skeleton

A selection of differently colored starfish

Even if the name echinoderms suggest otherwise, the animals do not have an exoskeleton. The outermost layer is rather formed by a thin and single-layer epidermis, which consists mainly of poorly differentiated supporting cells, each with a cilia . In between there are gland cells , mechanoreceptors and pigment cells. The gland cells produce mucus and adhesive secretions and they are particularly common in the area of ​​the suction feet of sea urchins, starfish and sea cubs and on the mouth tentacles of sea cows. In some sea urchins, especially the representatives of the Toxopneustidae , the glandular cells can also contain toxins that also act as neurotoxins in humans and are dangerous.

The pigment cells are responsible for the coloring of the animals. They can react to light, so that many species have different day and night drawings. This reaction can take place very quickly - the sea urchin Centrostephanus longispinus changes color from gray-brown to deep black in just 50 minutes if it is suddenly exposed to light. The colors themselves come from a mixture of different dyes , including the dark melanins , red carotenoids and carotene proteins, which can be blue, green or purple. In addition, there are naphthoquinones and, in the case of the diadem sea urchins , physical effects from reflective iridophores.

Pronounced spines of a sea urchin

The skeleton is located below the epidermis in the mesoderm and consists of calcite with a magnesium oxide content of three to fifteen percent. Since magnesium ions are smaller than the predominant calcium ions in calcite, they increase the packing density of the calcite crystals and strengthen the chemical bonds , which in turn increases the hardness and strength of the material. This effect is particularly evident in the teeth of the echinoderms. Due to its peripheral location, the skeleton largely determines the shape of the animals. The calcareous skeleton is not created by the simple separation of epidermal cells, but is created within a cell group of skeletal cells ( sclerocytes ). The resulting structure, called the stereom , is highly porous, which creates a structure that is both light and solid. The stereoma grows together to form plates called ossicles. The growth can take place in all directions, so that if a part of the body is lost, it can be replaced. Joints in the skeleton form larger elements , which are made mobile by muscles.

The spines of starfish and sea urchins are also articulated to the skeleton and can be moved against the skeletal plates below. The spines themselves are special formations of the stereome that only consist of a hollow, rolled up skeletal plate. Like all other skeletal elements, they are covered by epidermis. A special formation of the skeleton in sea urchins and starfish are the tweezer-like pedicellarians , which probably developed from spines. They consist of several elements and can be used to ward off parasites and the larvae of other marine animals that have established themselves as well as to catch prey. Further skeletal elements are the jaw apparatus of the sea urchins ( Aristotle's lantern ) made of 40 individual skeletal plates and the chalk ring of the sea rollers, which stabilizes the mouth opening. The epidermis of the sea rollers is also studded with microscopic calcareous needles (spiculae). The stem of the sea lilies also consists of individual skeletal elements, the disc-shaped trochites .

Ambulacral system

The inner canal system ( ambulacral system ) is unique , the outer projections of which serve as suction feet for the animals to move or as tentacles for food acquisition. In ontogeny, it developed primarily from the hydrocoel and consists of a ring canal around the intestine and the ambulacral or radial canals leading into the individual radii. The Madreporenplatte is also connected to the system via a hardened channel, the stone channel, and (with the exception of some sea rollers) represents the connection to the free water.

The animal's feet and tentacles are located on the radial canals. These are extensions that are arranged to the right and left of the radial duct and are connected to it by a thin feed duct. They can be led to the outside through the lime armor of the animals and serve here for food acquisition, gas exchange, locomotion, excretion and osmoregulation . They are structured differently in the different groups of echinoderms. In the case of sea lilies and hair stars, for example, they are mainly located on the transport channels for food intake, the pinnulae, and transport the food particles to the mouth opening. In the case of the starfish, sea urchins and sea cubs, they form little feet with a muscular inner ampoule that controls movement by regulating the pressure of the fluid.

Other organ systems

Sea roller

The intestines of the echinoderms have a very simple structure. In the brittle stars and starfish it moves directly from the mouth to the anus, while in the sea whales and sea lilies it is wound clockwise and in the sea urchins first clockwise and then counterclockwise. It is held in position by the mesenteries of the somatocoel. As a rule, the intestine can be divided into an area of ​​the mouth with a throat (esophagus), a stomach , an inner intestinal area and a rectal area with an anus. The surface area is enlarged by villi of the inner intestine; there are also areas with special functions such as the rectal gills of the sea rollers or the breathing siphons of burrowing sea urchins.

The blood vessel system or better the hemal system consists of a central ring (hemal ring) with five channels along the ambulacral canals. Another channel leads to the axial organ , which represents the connection point between the hemal system and the ambulacral system and, as a contractive organ, regulates the fluid circulation. The excretion via the ambulacral.

The echinoderm's nervous system is essentially a complex network of nerves beneath the epidermis and around the intestine. There is a ring of nerves around the throat, from which nerves also lead along the radial canals. Echinoderms have very few sense organs . The epidermis in particular reacts to light, temperature, direction of movement and flow through embedded sensory cells. The pedicellarians and spines also respond to various stimuli. Eye-like photoreceptors have developed from ambulacral feet at the ends of the arms of the starfish in particular ; Similar sensory cells are also found in sea urchins and sea cubs.

The gonads fill the entire body cavity, especially in the sea urchins and sea cubs, in the sea lilies and starfish they lie in the arms, in the starfish there are two fanned gonads per arm that end between the arms at a genital opening. Sea urchins have between three and five gonads that are attached to the interradii and open outwards. There is only one gonad in the sea rollers, which branches out in the body and ends in a genital duct with a genital opening at the rear end. Since many extinct echinoderms also had only one genital opening, this condition is considered to be original.

Reproduction and development

Sexual reproduction and brood care

Individual development from the release of the sex cells to metamorphosis
using the example of the sand dollar Clypeaster subdepressus . Running time: approx. 3 min.

Echinoderms become sexually mature after about two to three years, depending on the species and environmental conditions. The eggs and sperm are released into the open water where fertilization takes place. In some species in dense populations this happens in a timed manner. A pairing with internal fertilization has so far only been described in three brittle stars, three starfish and one deep-sea sea roller.

With some hair stars, the embryos develop in special brood pouches ( marsupia ), with these only the sperm get into the open water and fertilize the eggs in the brood pouches. Brood care is also required for some sea urchins and starfish . Different lance sea ​​urchins carry the young between the spines on the oral side, heart sea urchins have specially designed breeding chambers. In the case of starfish, special chambers can be formed in the area of ​​the breathing chambers on the aboral side or stomach pockets in which the youth development takes place. With some sea cubs, brood care takes place in areas of the crawl floor, between the tentacles or even in the body cavity. Most echinoderms do not care for their brood.

Larval development

Pluteus of a sea urchin

The beginning of the development is a radial furrow with an approximately equal division. First a coeloblastula develops, which turns into a gastrula by invagination . Mesoderm cells migrate into the cavity and later form skeletal elements. The secondary body cavity ( coelom ) is formed by the constriction of three paired bladders ( enterocoelia ).

With the metamorphosis different typical larval forms develop for the different taxa of the echinoderms. The Pelmatozoa (sea lilies and starfish) are always the yolk-rich Doliolaria or Vitellaria larvae, which after they have settled in them form an edible pentacrinus stage from which the finished animal later develops. The basic larval form of all Eleutherozoa is the Dipleurula larva, which in the starfish develops into an adult animal via a Bipinnaria larva and a Brachiolaria larva. In sea cucumbers, the first larval form is the auricularia larva with a uniform eyelash band, from which the doliolaria develops with three to five eyelash rings. The most conspicuous larvae are the sea urchins and brittle stars. These are Pluteus larvae with long floating spines. The larval shape is determined by the yolk content of the egg cell and the associated lifestyle. Larvae that emerge from an egg cell that is poor in yolk are generally planktotrophic, which means that they feed on plankton organisms in the free-swimming larval stage. In contrast, larvae that emerge from a yolk-rich egg cell live lecithotrophically, which means that they feed on their own yolk and therefore do not need an intestine. With the exception of Crinoida, since these only have lecithotrophic larval forms, all other classes have representatives with planktotrophic as well as representatives with lecithotrophic larvae.

During larval development, the already mentioned metamorphosis occurs, in which the five-pointed animals emerge from the initially bilaterally symmetrical larvae. The coelom, originally laid out in three paired cavities, forms the essential part of this. This is caused by a constriction on both sides in the roof of the primitive intestine , i.e. by the enterocoelia common in deuterostomia , as vesicles. The vesicles grow and divide into three sections towards the rear pole. The protocoel forms the uppermost, the mesocoel the middle and the metacoel the rearmost section. The left and right metacoel are superimposed as somatocoels and form the actual body cavity, which surrounds the intestine and contains the sex glands. The axocoel develops from the left protocoel, which opens out via a canal and the madrepora plate. The left mesocoel forms a hydrocoel into a ring canal as the center of the ambulacral system, which surrounds the intestine and is connected to the axocoel via the stone canal. Radial channels grow out of the ring channel into the later radii. The right hydrocoel disappears completely and the right axocoel is reduced to a small dorsal bubble. In most animals, the oral side forms accordingly on the left side of the body. There are changes to this development in the sea lilies, hair stars and the sea rollers.

Regeneration and asexual reproduction

A great many echinoderms can recreate lost body parts. Starfish and brittle stars also actively cut off body parts ( autotomy ) when they are in danger. The sea cucumbers expel parts of the internal organs, and sea urchins are constantly losing pedicellariums or spines. The regenerative capacity for all of these body parts is very well developed.

The ability to regenerate also allows the animals a form of asexual reproduction known as fissiparia . Starfish reproduce through the loss of arms, for example, whereby a new starfish can arise from each part of the arm. In some species, such as the Coscinasterus species, fissiparie causes the arms to multiply, with no new animals emerging. Some brittle stars reproduce in some populations apparently exclusively fissiparously over long periods of time.

distribution and habitat

Sea caster Stichopus fuscus off the coast of the Galápagos Island Champion

Echinoderms can be found in all seas and oceans worldwide, some species also live in brackish water . They are very common regionally and represent the most frequent inhabitants of the seabed in many areas. The different species are mostly specifically adapted to certain environmental conditions and are therefore only regionally limited. There are many species of echinoderms that can only be found in the tropics , while others live in the polar waters of the Arctic or the Antarctic . Among the tropical species are many that are always tied to coral reefs , but are found in all reefs throughout the Indian and Pacific Oceans .

Most echinoderms live entirely on the ocean floor and on other, similar structures such as rock structures or coral reefs. Many species also bury themselves in the sea floor. Only a few species of sea caterpillar in the deep sea are free swimming and live in the lower ocean layers. With the exception of the sessile sea lilies, all forms are very mobile and can actively cover long distances. The sea urchins and brittle stars in particular also use their free-swimming larvae to spread, which allow them to spread further. Their depth distribution is in turn dependent on the species. Some brittle stars live by the thousands in the tube systems of tropical sponges . Some sea cubs also live on other organisms, for example between the spines of large sea urchins in the Antarctic. One type of sea roller even attaches its body to the skin of deep sea fish and can be transported in this way.

The types of shallow water zones and sea coasts rarely occur at depths greater than 100 meters. Deep sea species can be found at depths of 1,000 to 5,000 meters. The deep sea species also include the sea daisies , which were only found in submerged wood in the deep sea. From areas with a depth of 10,000 meters and more, only sea roller species are known to date. In some areas, these represent up to 90 percent of all living organisms.

Way of life


The eating habits of the echinoderms are very diverse. The spectrum ranges from the sea lilies, which exude food particles from the surrounding water, to active hunters among the starfish. Most echinoderms feed primarily at night, but many also eat continuously.

The sea lilies and the feather stars belong to the filter feeders, which filter out the food from the surrounding water with the help of sieve structures. These are formed by the arms of the animals, which are often present in large numbers. The food particles, especially plankton organisms, get stuck in a slime that is formed and released by the ambulacral feet. The mucus, actively transported by cilia and feet, flows through channels in the arms to the central mouth opening.

Most sea urchins are omnivores or herbivores and use their sharp teeth to graze on algae and other nutrients from rocks on the sea floor. Other species, such as the toothless Irregularia , dig in the ground and attack smaller organisms with their pedicellarians. The sand dollars in particular absorb suspended matter that is transported over them by the movement of the water.

Brave star actively hunting for eggs from corals

Sea rollers use different types of food ingestion. Most species simply swallow large amounts of the seabed and extract organic components from it while excreting the remains. Some other species use their mouth tentacles to actively seek food to ingest from the sea floor. A third group uses their mouth tentacles as a net in which swimming organisms get caught.

There are also species of starfish that eat mud and extract the organic components. However, many species are also active hunters and hunt, among other things, other starfish and mussels , whose shells they open with their powerful arms. They often wrap their entire stomach around the prey and digest it outside of the body. Brittle stars usually actively catch small organisms out of the water, others have strongly fanned out arms and filter food out of the water like sea lilies.

Brittle stars have been seen actively preying on squid.

Enemies and defense

Although the echinoderms are well protected from enemies by their armor and spines, there are quite a number of predators that feed on them. The predators include stone fish , bottom sharks and other fish, as well as various crabs , sea slugs and, above all, larger starfish that eat smaller relatives and brittle stars. Sea urchins in particular are also hunted and eaten by sea birds such as the eider ducks as well as by sea ​​otters , arctic foxes and finally humans.

The main protection of echinoderms is provided by the sea urchins' already mentioned spines and their hard skeleton. In addition, some sea urchins have poisons that they can release via their pedicellariums. Many species of sea whale emit a tangle of sticky threads in danger, the Cuvier's tubes, while others produce strong poisons with the holothurines .


Sea urchins moving with the help of their ambulacral feet
Underside of a starfish with clearly recognizable ambulacral feet

Starfish and sea urchins move mainly through their ambulacral feet and the spines. This enables you to hike in any direction. These feet are also used as suction cups, which means that the animals can climb vertical structures. The brittle stars use their arms to move by weaving them around and slapping them in the direction of movement. The sea rollers also use the ambulacral feet to move. In doing so, they usually wander towards the front end and support the movement through contractions of their body. The Synaptidae also anchor themselves with their sticky tentacles and pull themselves forward.

The sea lilies usually do not move at all, although there are also species that can detach from their fixed point and fix again at another point. The hair stars swim by flapping their arms up and down, but they too are mostly loyal to their place. A swimming locomotion is also known with some brittle stars and especially with specially flattened sea rollers in the deep sea. These usually have a gelatinous body and no longer have a skeleton.

Many species of echinoderms dig in the ground and accordingly move around by digging. The sea urchins use their spines, pedicellarians and ambulacral feet to dig, and some species also have the option of digging through their teeth and spines into rock. The sea rollers dig in with the help of their tentacles and contracting movements. Sea urchins and brittle stars use their arms to dig.

Most echinoderms have a live position with the mouth opening toward the ground. If they are turned around, they try to return to their original position by stretching and twisting them.


Many echinoderms form large clusters, especially various sea urchins and brittle stars. This phenomenon has already been handed down in fossil form, as many fossil forms are found in large fossil deposits from one or a few species. These accumulations can mainly be traced back to various environmental conditions that offer the animals optimal living conditions. The distribution of food plays a major role here, with large collections of brittle stars often found in areas with high levels of plankton.

Ecological role and danger

Keyhole sea urchin

Echinoderms live on the one hand from organic waste on the sea floor and from parts of plants, on the other hand they represent effective predators of smaller animals. In doing so, they ensure the breakdown of organic material and the regulation of the small animal populations. In coral reefs, various starfish control the growth of algae mats and thus prevent the coral sticks from overgrowing. Sea rollers change the sea floor in a way that earthworms do on land. They eat large amounts of substrate and excrete this again after they have passed through the intestine. This frees the substrate from organic substances and at the same time changes it chemically and physically. Through burial activity, various burrowing starfish, sand dollars and heart sea urchins mix the ground at depths of up to 30 centimeters, and sea ​​urchins even drill holes in solid rock.

The large numbers of echinoderms larvae also provide a rich source of food for other animal species. The adult echinoderms are also eaten by various animals, such as sea otters, sea birds and some fish. Some echinoderms, especially sea walnuts, are the habitat for other animals. Various worms, but also crabs and marine snails, live in their bodies . Various gobies , which live in the intestines of sea rollers and use the anus as an entrance hole in their “burrows”, are particularly well known . Most of these inhabitants are commensals , but some are also parasitic , such as the snails of the Eulimidae family .

However, especially when the animals get out of hand, their feeding behavior can lead to an imbalance. For example, the mass populations of starfish in some kelp forest regions lead to the death of the large kelp plants, other species feed on coral polyps and lead to the death of entire reefs when they occur in large numbers .

Due to their calcareous skeleton, which reacts sensitively to changes in the pH value, the development of the larval form can serve as an indicator in research into the increased acidity of the oceans due to global warming . Experiments showed that a reduction in the pH value led to a smaller larval size and an increase in malformations during larval development, while an increase in temperature led to greater growth of the larvae and thus partially compensated for the smaller larvae size due to the lower pH value . This clearly shows the intense influence of climatic changes on echinodermates. Evidence has also been observed that the pollution of the seas by waste containing xenoestrogens may have an impact on the gender distribution ratio within a population of some echinoderms, but this has not yet been clearly proven.


Fossil sea lily crowns

The first reliable finds of echinoderms have been known since the early Cambrian, over 540 million years ago. However, there are also fossils from the late Precambrian ( Arkarua , Tribrachidium ) that are often assigned to this group of animals. During a first radiation in the Cambrian, several large groups that no longer exist today emerged. The Helicoplacoidea , spirally built animals, died out again in the early Cambrian. The asymmetrical carpoidea , which existed in several probably not closely related taxa, are more successful . Two of the four taxa survived the Cambrian, but these also disappeared in the course of the Paleozoic. So far, the representatives of the genera Peridionites and Cymbionites , which lived during the middle Cambrian, have not been classified .

With the less successful groups of the Cambrian, the already five-pointed Eocrinoidea and Edrioasteroidea emerged , from which the modern representatives of the echinoderms can be derived. These represent the basis for a further radiation of the echinoderms in the lower Ordovician . The Eocrinoidea were characterized by an upward mouth opening and the acquisition of body appendages in the form of brachioles (rarely real arms). Within this group, the cystoid and blastoid as well as the parablastoid and paracrinoidea developed . It is not known whether the sea lilies and hair stars that still exist today can also be traced back to this group.

The Edrioasteroidea had no anchoring organs and also no brachioles, but with them there was a reorientation of the mouth opening on the underside of the animals, while the anus migrated to the top. These animals formed the root of the Eleutherozoa, which also includes the starfish, brittle stars, sea urchins and sea whales that are still alive today.


In the classical system of echinoderms, a classification was established in the 1980s that deviates from the original categorization of animals into the predominantly fixed Pelmatozoa and the freely moving Eleutherozoa. The main argument against such a classification is the lack of reference to the extinct groups, in which both ways of life can be found in the various groups, both among the Eleutherozoa and the Pelmatozoa. The following system divides the fossil and recent echinoderms into several sub-tribes:

  • Trunk echinoderms (Echinodermata)
    • Sub- tribe Homalozoa † - Middle Cambrian to Middle Devonian (570–365 million years ago)
      • Class Stylophora † - Middle Cambrian to Upper Ordovician (540-460 million years ago)
      • Class Homostelea † - Middle Cambrian (540 million years ago)
      • Class Homoiostelea † - Upper Cambrian to Lower Devonian (510–400 million years ago)
      • Class Ctenocystoidea † - Middle Cambrian (540 million years old)
    • Sub- tribe Blastozoa † - Cambrian to Permian (570–280 million years)
      • Class Eocrinoidea † - Lower Cambrian to Silurian (570-430 million years)
      • Class bud radiators (Blastoidea) † - Silurian to Permian (430–280 million years)
      • Class Paracrinoidea † - Middle Ordovician (460 million years old)
      • Class Parablastoidea † - Lower to Middle Ordovician (500–400 million years ago)
      • Class Rhombifera † - Lower Ordovician to Upper Devonian (500–350 million years ago)
      • Class Diploporita † - Lower Ordovician to Lower Devonian (500–400 million years)
    • Sub- tribe Crinozoa - since the Lower Ordovician (500 million years until today)
    • Sub- tribe Asterozoa - since the Lower Ordovician (500 million years until today)
      • Class Somasteroidea † - Lower Ordovician to Upper Devonian (500–350 million years old)
      • Class starfish (Asteroidea) - since the Middle Ordovician (460 million years until today)
      • Class brittle stars (Ophiuroidea) - since the Middle Ordovician (460 million years to the present)
    • Sub- tribe Echinozoa - since the Lower Cambrian (570 million years to date)
      • Class Cyclocystoidea † - Middle Ordovician to Middle Devonian (460-375 million years ago)
      • Class Edrioasteroidea † - Lower Cambrian to Upper Carboniferous (570-340 million years)
      • Class Helicoplacoidea † - Lower Cambrian (570 million years old)
      • Class Ophiocistioidea † - Lower Ordovician to Upper Silurian (500–395 million years)
      • Class sea cucumbers (also: sea ​​cucumbers ) (Holothuroidea) - since the Ordovician (460 million years until today)
      • Class sea ​​urchin (Echinoidea) - since the Ordovician (460 million years ago until today)

In the phylogenetic system , the sea lilies and hair stars (Crinoidea) with around 620 recent species are compared to all other groups ( Eleutherozoa ) as sister groups . The starfish (Asteroidea) with around 1500 species living today and the brittle stars (Ophiuroidea) with around 2000 species form a group called asterozoa within the Eleutherozoa, the Echinozoa, the common taxon from sea urchins (Echinoidea) with around 950 species and sea cucumbers (Holothuroidea ) with about 1200 species.

   Echinodermata (Echinodermata)   

  “ Sea lilies ”: 4 taxa, systematics unclear.


  Feather stars (Comatulida)


  Starfish (asteroidea)


  Brittle stars (Ophiuroidea)


 Sea urchin (Echinoidea)


 Sea whales (Holothuroidea)

Template: Klade / Maintenance / Style

In the past, the brittle stars were not regarded as relatives of the starfish, but were placed together with the Echinozoa in a group called Cryptosyringida (hidden tubes). The reason was the hidden ambulacral system of the animals, which has recently been understood as convergence rather than synapomorphism .

Echinoderms and humans

Most people know the echinoderms from the unpleasant side: when you are near the coast - z. B. on rocks or a reef - many poisonous spines of a sea ​​urchin enter. Because of their fine, ring-shaped structure, these usually break off when they are removed - and then you need patience ( festering out ) or a doctor. However, echinoderms are special delicacies in the cuisine of some countries . Their skeletons are a popular collector's item for children.

Economical meaning

Sea urchin orange eggs

The economic importance of echinoderms is primarily local. Around 50,000 tons of sea urchins are caught each year, of which the gonads or eggs are eaten, particularly in Japan , Peru and France . In Japan the eggs are known as uni and are an ingredient in sushi cuisine. The taste is described as soft and melting. The quality depends on the color, which can range from light yellow to bright orange.

Sea rollers are also a delicacy in some countries in Southeast Asia. They are best known as trepang or bêche-de-mer in China and Indonesia . For this purpose, the sea rollers are freed from the (often poisonous ) entrails and dried. The pineapple sea roller ( Thelenota ananas ) (susuhan) and the red Halodeima edulis are particularly popular . The strong toxins of the sea whale, known as holothurins , are mildly psychoactive, but there are no known uses of the entheogenic effects. However, it has been found that holothurine has an inhibitory effect on the growth rate of various tumor cells , which makes it interesting for cancer medicine .

Ground starfish find their way into industrial animal feed as a lime additive , around 4,000 tons of the animals are used for this purpose every year. Especially in areas where mussels , especially oysters , are grown commercially , large numbers of starfish can cause great economic damage.


  • DT Anderson: Invertebrate Zoology. Oxford University Press, Oxford 2001, ISBN 0-19-551368-1 .
  • RSK Barnes, P. Calow, PJW Olive, DW Golding, JI Spicer: The invertebrates - a synthesis. Blackwell, Oxford 2001, ISBN 0-632-04761-5 , p. 151.
  • RC Brusca, GJ Brusca: Invertebrates. Sinauer, Sunderland Mass 2003, ISBN 0-87893-097-3 .
  • H. Fechter, E. Thenius: The echinoderms. In: Grzimek's animal life. Kindler, Zurich 1962.
  • A. Goldschmid: Echinodermata, echinoderms. In: W. Westheide, R. Rieger: Special Zoology. Part 1: Protozoa and invertebrates. Spectrum, Heidelberg 1996, 2003, ISBN 3-8274-0998-5 .
  • J. Moore: An Introduction to the Invertebrates. Cambridge University Press, Cambridge 2001, ISBN 0-521-77914-6 .
  • EE Ruppert, RS Fox, RP Barnes: Invertebrate Zoology. A functional evolutionary approach. Brooks / Cole, Belmont 2004, ISBN 0-03-025982-7 .
  • RA Raff, M. Byrne: The active evolutionary lives of echinoderm larvae. In: Heredity. 97, 2006, pp. 244-252.
  • HS Brennand, N. Soars, SA Dworjanyn, AR Davis, M. Byrne: Impact of Ocean Warming and Ocean Acidification on Larval Development and Calcification in the Sea Urchin Tripneustes gratilla. In: PLoS ONE. 5 (6), 2010, p. E11372.

Individual evidence

  1. US Department of Commerce, National Oceanic and Atmospheric Administration: Okeanos Explorer | Expeditions | NOAA Ship Okeanos Explorer: Mountains in the Deep: Exploring the Central Pacific Basin | Mission Logs | May 6. Retrieved May 16, 2017 (American English).
  2. ^ A b Alfred Goldschmid: Echinodermata, echinoderms. In: Wilfried Westheide, Reinhard Rieger: Special Zoology Part 1: Protozoa and invertebrates. 2nd Edition. Spektrum Akademischer Verlag, Heidelberg / Berlin 2007, ISBN 978-3-8274-1575-2 , p. 804 and 824.

Web links

Commons : Echinoderms  - Collection of images, videos, and audio files
This article was added to the list of excellent articles on May 5, 2005 in this version .