Life of a starfish. All about the starfish in exotic countries What's inside the starfish

In the world there are about 1600 modern species sea ​​stars (lat. Asteroidea) and they are found at almost any depth of the oceans.

Sea stars belong to the type of echinoderms, which include both invertebrates and vertebrates.

These star-shaped have from 5 to 50 rays-arms and usually their number is a multiple of five.

The ancestors of the starfish had six arms, and according to Dr. Marc de Lussane of the Institute of Psychology at the University of Münster, their structure was symmetrical. However, their sixth ray has long been lost in the process of evolution.

Like most marine life, stars, are brightly and variously colored, but there are species that merge with the bottom surface.

Sea stars range in size from 2 cm to 1 meter, although most will easily fit in the hand of an adult.

Stars have gills, which are hollow, thin outgrowths of the body wall that are ventilated sea ​​water on the outside and coelomic fluid (not blood) on the inside.

Most starfish feed on carrion or are predators that prey on various animals, especially snails, bivalves, crustaceans, polychaetes, other echinoderms, and even fish.

Some soft-bottom starfish, including species of the genera Luidia and Astropecten, are able to locate burrowed prey and then excavate the substrate to reach it.

Most starfish detect and locate prey through substances that the prey releases into the water, and many starfish prey species have evolved avoidance responses from slow moving starfish.

Some starfish are able to turn their stomach inside out through their mouths. The star envelops the prey that it cannot swallow with its stomach, and thus carries out external digestion. If their prey is protected by a shell, such as a mollusc, a gap of only 0.1 mm is enough for the predator to squeeze its stomach through and secrete a digestive enzyme that softens the muscles holding the shell flaps. Japanese species Astreias takes from 2.5 to 8 hours, depending on the type of mollusk, to digest the entire prey.

A small number of starfish species feed on plankton suspended in the water column (Echinaster, Henricia, Porania), while others absorb sedimented material (Ctenodiscus, Goniaster) that comes into contact with the body surface. This material is captured by the mucus and then transported by the cilia of the epidermis towards the oral surface.

The inside-out stomach is an efficient feeding organ for many omnivorous and non-predatory starfish. Starfish Patiria miniata from the west coast of America spreads its stomach along the bottom, digesting organic matter that comes across. Similarly, the tropical cushion star Culcita and Oreaster, which inhabit coral reefs, feed on sponges, algal felt, and organic films.

The body cavity is filled with coelomic fluid containing numerous amoeboid cells. These cells absorb waste products and foreign bodies and leave the body through the integument. Thus, they perform excretory and immune functions.

Sea stars have eyes located at the ends of their rays.

The movement of blood in Asteroidea occurs due to muscle contraction. The study of blood circulation in holothurians demonstrates that the blood flow through the vessels periodically increases and decreases (which indicates the presence of a rhythm similar to that of the heart). At a temperature of 25 °C, the heart of Asterias forbesi makes approximately 6 beats per minute.

The body fluids of all sea stars, as well as those of all echinoderms, are similar in composition to sea water. Their inability to regulate salt prevents most species from living in estuaries and fresh waters.

Lavender starfish. This starfish of absolutely incredible coloration lives on the reefs of Bunaken Island in Sulawesi, Indonesia.

Deltoid starfish between emerald corals in the Western Pacific.

Starfish devour oysters, causing economic damage to fisheries. From time to time, starfish have to be removed from commercial oyster jars with a tool that looks like a wide mop that drags along the bottom. Starfish get tangled or grab the mop threads with their pedicellariae, they are brought to the surface and destroyed.

For some starfish, reproduction by splitting apart is the normal form of asexual reproduction. At the same time, softening of the connective tissue occurs in the division plane. The most common form of fission is the splitting of a star in half. Each half then regenerates the missing portions of the disk and arms, although extra arms often appear along the way.

Damaged starfish regenerate very easily, rebuilding lost arms and damaged disk parts. Completion of regeneration is slow and sometimes takes a whole year to complete.

Species of the starfish genus Linckia, common in pacific ocean and other areas of the oceans, are unique in their ability to throw their hands entirely. Each individual hand, if not eaten by a predator, can regenerate a new body.

The rays (hands) contain the digestive outgrowths of the stomach and the processes of the genital organs; inside the arms is located along the longitudinal row of vertebrae.

The legs of starfish are flexible tubular outgrowths, usually with suction cups at the end, and are driven by water pressure in the internal channels and ampullae of the ambulacral system.

The tropical Pacific star Acanthaser planci ("") is known for its rate of consumption of coral polyps. Due to their high density (about 15 adults per 1 m2), these stars have already been destroyed by now. a large number of reef corals in some areas.

These echinoderm marine animals belong to the class Asteroidea. People often call them starfish.

Echinoderm marine animals, in addition to starfish, include sea urchins, sea ​​lilies and sea cucumbers (holothurians).

Sea stars are not fish. They do not have gills or fins, and they move in a completely different way than fish. Starfish have tiny tube-legs.

If you carefully turn a living starfish over, you will see its tubular legs moving towards you.

Starfish move with the help of hundreds of tubes that are located on their underside. The starfish's tubular legs also help it hold its prey, which includes bivalves, mussels, microalgae, snails and sponges, as well as small fish.

Starfish live all over the world, in the intertidal zone and in the deep layers, in warm and cold water. But they do not live in fresh water.

More than 1500 types of starfish. Depending on the species, the skin of the starfish can be leathery or slightly prickly. Starfish have a tough coating on their upper side, which is made up of calcium carbonate plates with tiny spikes on the surface.

The spines of starfish are used to protect against predators, including birds and fish.

Starfish are beautiful animals that come in a variety of colors, shapes, and sizes, but they all resemble a star. Some of them are relatively smooth, but all of them have spikes covering their upper surface, while their lower surface is soft.

A starfish usually has five rays with a central disc. The number of limbs in starfish depends on the species. Some of them have many rays. For example, the Sun-Star can have up to 40 rays!

The largest sea stars live in the Pacific Northwest.

Here the sun-stars are 1 meter (3 feet) in diameter and can weigh 5 kilograms (11 pounds). Sunstars are more active than many other starfish species, capable of chasing fast-moving prey. Although they come from cold waters, they have truly tropical colors.

Starfish are painted in a variety of colors: blue, red, orange, gray, brown ... These marine invertebrates are considered the most beautiful marine animals in the ocean.

If you have ever tried to open the shell of a clam or mussel, you know how difficult it is. Starfish open the shells of a mollusk quite simply.

And how they eat, you can't even imagine it - they push their stomach through their mouth, then digest the caught prey, and then pull their stomach back into their body.

This unique feeding mechanism allows the starfish to eat larger prey than can fit through its tiny mouth. The mouth (mouth) of a starfish is located in the center of its lower surface.

The main food for the starfish is benthic invertebrates. The feeding behavior of the starfish is unique. Starfish eat with their stomachs inside out.

The average lifespan of a starfish is 35 years. The life cycle of a starfish can be performed sexually and asexually.

Starfish can regenerate their lost limbs.

If a starfish is threatened by a predator, it may lose an arm, but then it is able to grow a new organ.

Sea stars have most of their vital organs at their tips. Some can even create a completely new body of their own, with only one limb and part of the central disk left of the starfish. Recovery does not happen quickly - regeneration takes about a year.

They have no blood, no brains and no problems

Sea stars have eyes - the place of the eyes at the end of each arm. This is a very simple eye that looks like a red spot. The eye does not see many details, but distinguishes light and dark tones.

starfish filters sea ​​water to pump nutrients into your nervous system.

Lacking blood flow, starfish pump sea water through their bodies, take in oxygen and other essential fluids. Sea water serves as a substitute for blood.

The starfish's radiation body is channels filled with sea water that moves through a complex spiral system of particles.

Sea water is circulated through the body almost mechanically, with muscles and a system of lymph nodes working to move the water.

The sinuses and the various corpuscles and tubal systems all work together with maximum efficiency, without the presence of blood. The body of a star is still a mystery, and we still cannot understand how it works.

For scientific researchers, the starfish body remains one of the most interesting biological objects on this planet.

• People in the Indonesian archipelago, Japan, China and Micronesia eat starfish.
• They are kept in an aquarium or as souvenirs.

Most of us think of starfish as an ornament to the ocean, but starfish are voracious predators, not passive herbivores. It may come as a great surprise to you to learn that cannibalism is a well-documented fact in the life of these strange creatures.

Sea stars look attractive, but they are voracious predators with exceptional hunting abilities.

The ecology of the sea would not be complete without mentioning the ecological danger that the crown-of-thorn starfish represents. Covered in venomous spines, these creatures are half a meter across, endangering the lives of careless divers and swimmers, and destroying coral reefs.

The doubling of phytoplankton levels was associated with a 10-fold increase in the populations of these animals. Changes in ocean temperature and currents, as well as a decrease in natural predators, have also occurred due to booms in the population of crown-thorn starfish. The spikes in the population of these echinoderms cause significant damage to coral reefs. One of the most serious cases is damage to the Great Barrier Reef.

A 50% decrease in total coral cover on surveyed reefs older than 30 years showed that half of this decline can be attributed to an increase in starfish thorn populations.

They raise many questions, among which the following are of particular interest: "What does a starfish eat?", "For whom does it pose a mortal threat?".

Stars at the bottom of the sea

These unusual decorations of the seabed have existed on the planet for a long time. They appeared about 450 million years ago. There are up to 1600 types of stars. These animals inhabit almost all the seas and oceans of the earth, the water of which is quite salty. Stars do not tolerate desalinated water; they cannot be found in the Azov and Caspian Seas.

Rays in animals can be from 4 to 50, sizes range from a few centimeters to a meter. The life span is about 20 years.

Marine inhabitants do not have a brain, but on each ray there is an eye. The organs of vision resemble insects or crustaceans, they distinguish between light and shadow well. Many eyes help animals hunt successfully.

Stars breathe almost through their skin, so a sufficient amount of oxygen in the water is very important for them. Although some species can live at decent depths of the ocean.

Structural features

It is interesting how they breed, how starfish feed. Biology classifies them as invertebrate echinoderms. The starfish has no blood as such. Instead, the heart of the star pumps sea water enriched with some microelements through the vessels. The pumping of water not only saturates the cells of the animal, but also, by pumping fluid in one place or another, helps the star move.

Starfish have a ray structure of the skeleton - rays extend from the central part. The skeleton of sea beauties is unusual. It is composed of calcite and develops inside a small star from almost a few calcareous cells. What and how starfish eat depends largely on the characteristics of their structure.

These echinoderms have on their tentacles special pedicellaria in the form of tweezers at each end of the outgrowth. With their help, the stars hunt and clean their skins from litter clogged between the needles.

Sly hunters

Many are interested in how starfish eat. Briefly about their structure digestive system can be found below. These amazing beauties give the impression of perfect security. In fact they marine predators, voracious and insatiable. Their only drawback is their low speed. Therefore, they prefer a motionless delicacy - shells of mollusks. With pleasure, the starfish eats scallops, is not averse to eating sea urchin, trepang, and even a fish that has inadvertently swam too close.

The fact is that the starfish has almost two stomachs, one of which can turn outward. A careless victim, seized by pedicellaria, is transferred to the mouth opening in the center of the rays, then the stomach is thrown over it like a net. After that, the hunter can release the prey and slowly digest it. For some time, the fish even drags its executioner along with it, but the victim can no longer escape. Everything that a starfish eats is easily digested in its stomach.

She acts somewhat differently with shells: she slowly approaches the dish she likes, braids the shell with her rays, places the mouth opening opposite the slit of the shell and begins to push the valves apart.

As soon as a small gap appears, the external stomach immediately pushes into it. Now the sea gourmet calmly digests the owner of the shell, turning the mollusk into a jelly-like substance. Such a fate awaits any victim eaten, no matter whether the starfish feeds on scallops or small fish.

Features of the structure of the digestive system

The predator does not have any devices for capturing prey. The mouth, surrounded by an annular lip, connects to the stomach. This organ occupies the entire interior of the disc and is highly flexible. A gap of 0.1 mm is enough to penetrate the shell flaps. In the center of the aboral side, a narrow short intestine opens from the stomach. What a starfish eats largely depends on the unusual structure of the digestive system.

The love of the stars at the bottom of the ocean

Most starfish are heterosexual. At the time of love games, individuals are so busy with each other that they stop hunting and are forced to fast. But this is not fatal, because in one of the stomachs these sly ones tend to deposit nutrients for the entire time of mating in advance.

The sex glands are located near the stars near the base of the rays. When mating, the female and male individuals connect the rays, as if merging in a gentle embrace. Most often, caviar and male sex cells fall into sea water, where fertilization occurs.

In the event of a shortage of certain individuals, the stars can change sex to maintain the population in a certain area.

These eggs most often remain on their own until the larvae hatch. But some stars turn out to be caring parents: they carry eggs on their backs, and then larvae. In certain types of starfish, for this, during mating, special bags for caviar appear on their backs, which are well washed with water. There she can stay with the parent until the larvae appear.

Reproduction by division

A completely unusual ability of starfish is reproduction by division. The ability to grow a new hand-ray exists in almost all animals of this species. A star caught by a predator by the beam can throw it away like a lizard's tail. And after a while grow a new one.

Moreover, if a small particle of the central part is preserved on the beam, a full-fledged starfish will grow out of it after a certain time. Therefore, it is impossible to destroy these predators by cutting them into pieces.

Who are the starfish afraid of?

The representatives of this class have few enemies. No one wants to mess with the poisonous needles of sea celestials. Animals still know how to secrete odorous substances to scare off especially voracious predators. In case of danger, the star can burrow into the silt or sand, becoming almost invisible.

Among those who feed on starfish in nature, large sea birds predominate. On the banks warm seas they become prey for gulls. In the Pacific Ocean, cheerful sea otters are not averse to feasting on stars.

Predators harm underwater plantations of oysters and scallops - what the starfish eats. Attempts to kill animals by cutting them apart have led to an increase in the population. Then they began to fight with them, bringing the stars to the shore and boiling them in boiling water. But there was nowhere to use these remains. There have been attempts to make fertilizer from animals that repels pests at the same time. But this method has not received wide distribution.

Sea stars - animals with unusual shape body, thanks to which they attracted the attention of people in ancient times. Sea stars belong to the phylum Echinodermata, in which they are separated into a separate class, numbering almost 1600 species. The closest relatives of these invertebrates are the ophiurs, or serpenttails, which are very similar to them, and the more distant holothurians and sea urchins.

Fromia elegant starfish (Fromia monilis).

home distinguishing feature starfish is, of course, the shape of the body. In general, the body of starfish can be divided into central part- disk, and lateral outgrowths, which are commonly called rays or arms. These animals are characterized by radial symmetry, so their body is divided into symmetrical sectors, the number of which is usually five. However, among starfish there are organisms with a large number of axes of symmetry: in some species their number can reach 6-12 and even 45-50.

Nine-armed starfish (Solaster endeca).

Each sector, respectively, includes a part of the central disk and a hand. It would seem that such a structure of the same type should result in the uniformity of these living organisms. But just the shape of the body of starfish is very variable. First, the relative length and thickness of the rays varies greatly: in some species they are elongated and thin, in others they have a triangular shape, sharply tapering towards the end, in others the rays are so short that they practically do not protrude beyond the edges of the central disk. The stars of the last type have a very high central disk, so they resemble pillows. Thus, in most types of starfish, the length of the rays is 3-5 times greater than the diameter of the central disk, in the longest-armed ones it is 20-30 times, and in pillow-shaped ones it tends to zero.

This bright ottoman seabed in fact, the New Guinean culcita starfish (Culcita novaeguineae).

Secondly, starfish differ in surface texture and color. Here the variety simply defies description - smooth, spiny, prickly, rough, velvety, mosaic; monochrome and patterned, bright and faded. The color scheme of these animals includes almost all colors, but most often there are various shades of red, less often blue, brown, pink, purple, yellow, black. Pale starfish usually live in deep water, while shallow water species are bright.

This is the same New Guinea culcite, but of a different color.

At first glance, starfish seem primitive, because they do not have any noticeable sensory organs, brain, are poorly differentiated internal organs but this simplicity is deceptive.

Linkia starfish (Linckia laevigata) is bright blue in color, its rays look like sausages.

First of all, it should be noted that starfish have an internal skeleton. They do not have a backbone and separate bones, but there are many calcareous plates connected to each other in an openwork system.

Openwork plexus of skeletal elements on the surface of a starfish.

A young starfish has skeletal elements hidden underneath skin, but over time, the skin over some of the calcareous spikes wears off and they become visible from the outside. It is these spikes that give starfish prickly look.

The spikes on the surface of the starfish are covered with skin, but some of them are already exposed and have a shiny surface.

In addition, calcareous plates can be seen on the upper side of the body in many species, fused together or forming a network.

A bizarre pattern formed by the skin and skeletal elements of the starfish.

Finally, the third element affecting appearance starfish are pedicellariae. Pedicellaria are modified needles that look like tiny tweezers. They play an important role in the life of the starfish, with their help it cleans the upper side of the body from debris and sand. All skeletal elements are interconnected by muscles, therefore, after the death of a starfish, its skeleton crumbles into lime plates and there is not a trace left of the animal.

The starfish acanthaster, or the crown of thorns (Acanthaster ellisii) has prickly and poisonous thorns.

The muscular system of starfish is relatively poorly developed. Each ray has a muscle cord that can bend the ray upwards, and this, in fact, is what the muscle movements of the stars are limited to. But mobility is not limited at all. Starfish can crawl, dig, bend, swim, but they do not do this with the help of muscles.

Starfish scalloped patiria (Patiria pectinifera) climb algae.

These animals have a special body system - ambulacral. In essence, this system is channels and cavities connected together and filled with liquid. The starfish can pump this fluid from one part of the system to another, causing its body parts to bend and move. The centerpiece of this system is the ambulacral pedicles, tiny blind outgrowths of the ambulacral canals on the underside of the starfish. Each leg moves independently of the others, but their actions are always coordinated. With the help of these microscopic elements, the starfish can work wonders. For example, it is able to climb a vertical surface, it can stick to the glass of an aquarium for a long time, it can stand on its hind legs, swelling up like an angry cat, or it can, grabbing two beams, push the shells of a mollusk apart. And all this is done by an animal practically devoid of a brain and eyes!

On the underside of the beam, translucent ambulacral pedicles are visible.

In fairness, it should be noted that starfish still have some sense organs. These are eyes located at the ends of each beam. The eyes are very primitive and distinguish only between light and darkness; starfish do not see objects. Starfish are able to capture chemicals (analogous to scent), but they feel them differently. Some species are very sensitive and can crawl to the bait by smell for several days in a row, others can crawl past the victim a couple of centimeters and not smell it. Sea stars have a very developed sense of touch, they try to get rid of the sand that fills them from above, and they also always try to feel their way with the help of small tentacles at the end of each beam. The sense of touch tells the starfish whether it is a prey or a predator. The brain of a starfish is replaced by a group of loosely interconnected cells. Surprisingly, despite such a primitive structure nervous system starfish can produce elemental conditioned reflexes. For example, individuals that were often caught with nets began to get out of them faster than those that were caught for the first time.

At the end of the ray of the starfish asterodiscus (Asterodiscus truncatus) a decorated eye is visible. The beam itself is covered with relief lime plates.

Another strong, literally and figuratively, system in starfish is the digestive system. The mouth of these animals is located in the center of the disk on the underside of the body, and the tiny anus is located on the back. By the way, starfish rarely use it (in some species, it generally overgrows), preferring to remove undigested food residues through the mouth. The stomach of these invertebrates has outgrowths extending into rays, they store food reserves in case of hunger. And starfish starve regularly, because during breeding they stop eating. The stomach in many species can turn outward through the mouth opening, and it stretches like rubber, taking any shape. Thanks to the expandable stomach, the starfish can digest prey that is larger than it is. A case is known when the starfish luidia swallowed such a large sea urchin that it died, unable to spit out its remains.

In the middle of the central disk of fromia monilis, a tiny anus is visible.

Other body systems are poorly developed in starfish. They breathe through special outgrowths of the skin on the upper side of the body washed by sea currents. They do not have gills and lungs, so starfish are sensitive to lack of oxygen. They also cannot stand desalination, so they are found only in the seas and oceans. The sizes of these animals range from 1-1.5 cm for the miniature spherical star Podosferaster to 80-90 cm for the Freyella starfish.

The name of this starfish speaks for itself - elegant fromia (Fromia elegans).

Sea stars have a global distribution. They are found everywhere in all seas and oceans from the tropics to the poles. Of course, in warm waters species diversity higher than in the cold. Most species prefer to live in shallow waters, some even end up on the shore at low tide. But among these animals there are also deep-sea species, including those that live at depths of more than 9 km!

Sea stars in shallow water.

Starfish crawl along the bottom most of the time. They do this very slowly, the usual speed of a medium-sized individual is 10 cm per minute, but a starfish can also “hurry up” at a speed of 25-30 cm per minute. If necessary, these animals climb stones, corals, algae. If a starfish falls on its back, then it immediately turns over with its ventral side down. To do this, the animal bends two rays so that the ambulacral legs on the lower side touch the ground, and then the starfish twists its body and assumes its usual position. Some species are even able to clumsily swim short distances. Sea stars can be called sedentary animals, their tagging has shown that they do not move more than 500 m from the place of the original catch.

The starfish granular coriaster (Coriaster granulatus) looks like a bun.

Despite the outward primitiveness and seeming helplessness, starfish are formidable predators. They are quite gluttonous and never refuse prey, except for the period of gestation of eggs. Only deep-sea species feed on silt, from which they extract food particles; culcite starfish, which prefer to nibble on coral fouling, can also be called conditionally “non-predatory”. All other species actively prey on other animals.

By no means romantic relationship connected this couple: the starfish Solaster (Solaster dawsoni) eats spiny hippasteria (Hippasteria spinosa).

Most starfish are not picky, they eat everything they can hold with their hands and what their “rubber” stomach can get, without disdaining carrion. Some species can only eat a certain type of food: sponges, corals, gastropods.

Pretty starfish pentagonaster (Pentagonaster pulchellus), which is also called the biscuit starfish for its biscuit-like body shape.

The favorite prey of sea stars are sedentary animals like themselves - sea urchins and bivalve molluscs. sea ​​urchin the star catches up with a crawl and eats with its mouth. Bivalve mollusks have shells that close tightly in case of danger, so they are treated differently by starfish. First, the starfish is glued with two rays to the shell valves, and then begins to push them apart. I must say that the ambulacral legs are firmly glued to the substrate due to the adhesive lubricant and one single ambulacral leg can develop a force of up to 30 g! And on each ray of a starfish there are hundreds of them, so she, like a real strongman, pushes the shells apart with a force of several kilograms. However, the starfish does not need to push the shell flaps to its full extent; for a hearty dinner, a gap of 0.1 mm is enough for it! In this truly microscopic gap, the starfish twists its stomach (it can stretch 10 cm) and digests the mollusk in its own home.

Asteria starfish (Asterias rubens) stretches its hand towards a mollusk.

Most sea stars have separate sexes, very few species have both male and female gonads. The gonads are arranged in pairs at the base of each ray. In the starfish asterina, young individuals are first male, and then change it to female. A special exception is the ophidiaster starfish, which has no males at all! Females of this species lay eggs without fertilization, such reproduction is called parthenogenesis. During mating, males and females combine their rays and sweep sperm and eggs into the water. The number of eggs depends on the type of development of the larva and ranges from 200 in those species that bear offspring, and up to 200 million in species with free-swimming larvae.

Mating starfish.

Starfish larvae come in three types. In some species, a free-swimming larva hatches from the eggs, which feeds on microscopic algae, and then attaches to the bottom and gradually turns into a small star. In others, the free-swimming larva has a large supply of yolk, so it does not feed and immediately transforms into an adult form. In starfish that live in cold waters, the larvae do not separate from the mother's body at all, but accumulate near her mouth or even in special stomach pockets. A caring female during this period relies only on the tips of the rays, and the body arches in a dome, under which the offspring is located. Since the larvae are located near the mouth opening, the female does not feed during this period. The larval form is the most mobile in life cycle starfish, it is during this period that the young can be carried by currents over very long distances.

The starfish larva is bilaterally symmetrical.

In addition to sexual reproduction, starfish can also reproduce asexually. Most often this occurs in multi-beam species, the body of the animal is divided into two halves, each of which builds up the missing rays. In other species, asexual reproduction may be the result of regeneration after traumatic injury to the body. If a starfish is artificially divided into several parts, then each will form new organism. Even one beam is enough to restore, but a piece of the central disk is required. Sea stars grow slowly, so for many months they look one-sided.

A new individual is formed from the cut off ray of a starfish. This shape is often called a comet.

AT natural environment starfish have very few enemies, as sharp spikes, which can be poisonous, scare away large predators. In addition, these invertebrates, on occasion, try to burrow into the sand so as not to attract attention. Most often, starfish fall on the teeth of sea otters and gulls.

The seagull caught a starfish.

But the starfish astropecten is friends with polychaete worms. Up to five cohabitants can be found on one individual, who prefer to stay on the underside of the body closer to the mouth of the star. The worms pick up the remains of her prey and even put their head in her stomach! A special type of ctenophores live on the Echinaster starfish, which clean the surface of the star from fouling.

These bright spots on the Luzon starfish (Echinaster luzonicus) are ctenophores (Coeloplana astericola).

Since ancient times, people have paid attention to the colorful animals of shallow water, but starfish have not been of any economic interest to them. Only in China are they sometimes eaten, while feeding starfish to pets can lead to their death. This is probably due to the toxins that some species accumulate by eating corals and poisonous shellfish. But with the development of the marine economy, people began to classify these animals as their enemies. It turned out that starfish often eat the bait in bottom crab traps, and also raid oyster and scallop plantations. In a few years (that's how many oysters need to be grown), starfish can destroy an entire oyster jar. At one time, they tried to destroy predators by cutting them into pieces, but this only increased their numbers, because a new starfish grew from each stump. Then they learned how to extract starfish with special trawls and kill them with boiling water.

Very spectacular mosaic starfish (Iconaster longimanus).

The most malicious pest was the starfish acanthaster, or the crown of thorns. This very large echinoderm feeds exclusively on corals, after which the crown of thorns leaves only a white lifeless path on the coral reef. At one time, these stars multiplied so much that in literally words have eaten away a huge section of the Great Barrier Reef off the coast of Australia. The unique geological formation was under the threat of destruction. The fight against the crown of thorns was complicated by the fact that its thorns are poisonous to humans, the prick of the crown of thorns causes burning pain, although not fatal. Specially trained divers collected acanthasters with sharp spikes in bags or injected a lethal dose of formalin into the body of a starfish. Only in this way it was possible to pacify the invasion of voracious predators and save the reef. Now all types of starfish are in a safe condition and do not need protection.

The crown of thorns eats the coral.

For many of us, the knowledge about stars ends with the fact that this is some kind of bizarre creature that inhabits the oceans. In fact, these creatures are not only unusual and unique, but also very interesting.
1. Star shape
Although often the shape of a starfish corresponds to its name, sometimes there are unusual individuals of a bizarre shape. For example, starfish may be sun-shaped, with numerous rays, or their shape may be rounded. The largest starfish can reach 1 meter in diameter and weigh up to 5 kilograms. Very interesting solar stars, which are more active than their relatives, and are able to rapidly pursue their prey. Due to their strength, they can easily break the shell of molluscs and crustaceans.

2. Lack of blood and brain
Although the shape of starfish is quite complex, their bodies are very primitive. Although they have a highly adapted digestive system and advanced skin, they are noted to be deficient in brains and lack blood. To get all the necessary nutrients, oxygen and other important fluids, the starfish pumps sea water through its body. It is the resulting water that is distributed throughout the body and forms the “water-vascular system”.

3. Starfish suckers
What many perceive as tentacles are actually the arms of a starfish. On each of the hands, there are about 15 thousand tiny suckers, thanks to which the starfish moves.

4. Cannibalism
It turns out that these cute creatures are actually real predators. They are able to attack their own kind and can easily feast on the small offspring of their species.

5. Two stomachs
These greedy predators have two stomachs, one of which they can even push out to digest shellfish. The digestive process of the starfish is an incredible example of evolutionary progress, especially given the primitiveness of these creatures in other respects.

6. Crown of thorns
Many of the starfish are very dangerous. For example, the crown-of-thorns starfish, common throughout the Indo-Pacific Ocean, is covered in poisonous spines. Growing up to almost half a meter in length, these creatures become dangerous not only for coral reefs, but also for divers and swimmers.

7. Fancy Pillow
At first glance, pillow stars are difficult to classify as starfish because of their bizarre shape. Their swollen body is more like a pillow, and their arms are completely absent. These stars often feed on algae and occasionally corals, and small fish can even live in their water-filled cavity.

8 Starfish Diseases
Not so long ago, the low resistance of starfish to infections was discovered, which is why some species began to die out catastrophically quickly. The main reason for the death of starfish is environmental pollution.

9 Starfish Eyes
Starfish have eyes and are located on the tips of their arms. Thanks to the eyes, starfish can collect all the necessary visual information and move in the required direction.

10 Stars Can Change Gender
Starfish are able to easily change gender, and then switch back. Such changes may occur for reproduction as a response to water quality, temperature, and food availability.