Most starfish have a rough eye at the tip of each arrow. These compound eyes contain multiple lenses (ommatidia), each of which creates one pixel in the overall image that the creature sees. Tropical starfish are able to see crude images with their own eyes, which allows the animals to stay closer to home.

Scientists have found that some species of deep-sea starfish, found at depths of up to 1 km below the surface of the water, where sunlight does not penetrate, can see despite the darkness. Most species that can see in the dark depths of the ocean have more sensitive eyes, but see grosser images. These same starfish seem to distinguish objects more clearly than their tropical counterparts living on the light shallows.

Scientists offer different explanations for this. Some species seem to see clearly in the horizontal direction, but less clearly in the vertical, which is absolutely true for an organism that lies on the seabed. In other species, it appears fewer options detect changes in what they see over time.

These two species are also bioluminescent, meaning they are capable of producing short flashes of light on the surface of their bodies. The combination of these flashes of light and the ability to see clearly allows these deep-sea starfish to communicate with potential mates.

Regeneration

Hungry predators, crabs or fish, can bite off the arrows of starfish. If a fight ensues, some species of starfish will voluntarily lose their limbs so that the rest of their body can escape. Moreover, they can regenerate an entire limb. If you find a starfish that has one arrow that is smaller than the others, there is a good chance it is a new limb.

On sea water

Starfish do not have the usual set of muscles. Instead, they move with the help of seawater, which is pressurized in the vascular system of their bodies. They draw seawater through the pores, then it passes through internal channels into the limbs, and these already set thousands of tubular “legs” in motion.

The muscles and valves inside each tube compress the water, allowing them to stretch and retract, creating movements similar to walking with your feet, but multiplied hundreds of times. At the end of each tube foot is a tiny suction cup that can stick to surfaces and help propel stars.

Gastric Ejection

Sea stars are extremely efficient seabed predators, feeding on a wide range of foods - mussels, clams, oysters. They sneak up on their prey and use their legs to simultaneously grab the prey and pin it to the seafloor.

If the prey is small enough, the starfish will swallow the entire animal by inflating its stomach, located in the center. While maintaining a death grip position, the starfish will gradually dissolve the edible soft tissue using enzymes inside the stomach and then discard the inedible hard parts of the shell.

But if the prey is too large to fit into its stomach, the starfish will first try to open the shell and then push its stomach into the gap so that it can destroy the soft tissue inside the victim and digest it right in its house, as if sucking it through a straw.

Starfish are amazing!

Sea stars- These are very unusual animals that live in the seas and oceans. They are invertebrates, belong to the phylum echinoderms and are very similar to stars, as they have rays diverging in different directions. Most often, the sea star has five rays, but there are species with three, four and six rays. The color of the body is often very bright and varied; on the surface there are special hard plates with needles or spines. The sizes of stars vary greatly and can range from 2 cm to 100 cm, but most stars have a diameter of about 20 cm.

Spreading

Starfish are widely distributed around the globe. They can be found in all oceans and seas and in all climatic zones, but in warm waters there are more starfish than in cold waters, and in fresh waters they are not found at all.

These animals prefer a bottom lifestyle, often live in shallow water, but can also live at depth, but not deeper than 8.5 km.

Now on earth there are 1.6 thousand species of starfish.

Nutrition

Almost all starfish are predators. They mainly feed on marine invertebrates - worms, mollusks, sponges, barnacles, corals and others. Some deep-sea starfish feed on the mud they find on the bottom.

The digestive system of starfish is quite unique. Their mouth opening is located on the ventral side, and two stomachs extend from it. One stomach has the ability to turn outward and envelop the victim, and the second stomach has ten processes that are located inside the rays of the starfish. This unusual digestive system allows the star to eat prey that is larger than itself.

Lifestyle

Starfish are slow, sedentary animals. They usually crawl lazily along the bottom, lie still, or may climb rocks and corals in search of prey. Their movement speed is very low - 10-30 cm per minute. Stars are considered sedentary animals. As a rule, they move no further than 0.5 km from their usual place of residence.

In their development, stars go through several stages of development. From the eggs that adults throw into the water, larvae are first formed and then they gradually turn into an adult starfish. Some species of starfish carry larvae in special brood pouches on their bodies.

Starfish can live 20 years or more.

• Starfish don't have a brain.
• Instead of eyes, starfish have light-sensitive cells located at the tips of their rays.
• Starfish are capable of regeneration - from a detached ray, a new star can develop.

Brief information about starfish.

Starfish - animals with unusual shape bodies, thanks to which they attracted the attention of people back in ancient times. Starfish belong to the phylum Echinodermata, in which they are classified as a separate class, numbering almost 1,600 species. The closest relatives of these invertebrates are brittle stars, or snaketails, which are very similar to them, and more distant relatives are sea cucumbers and sea urchins.

Starfish elegant fromia (Fromia monilis).

home distinguishing feature starfish is, of course, a body shape. In general, the body of starfish can be divided into a central part - the disk, and lateral outgrowths, which are usually 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 axes of symmetry: in some species their number can reach 6-12 and even 45-50.

Nine-armed starfish (Solaster endeca).

Each sector, accordingly, includes part of the central disk and a hand. It would seem that such a similar structure should result in the monotony of these living organisms. But the body shape of starfish is very variable. Firstly, 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 latter type of stars have a very high central disk, so they resemble pillows. Thus, in most species of sea stars, 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 the cushion-shaped ones it tends to zero.

This colorful ottoman on the seabed is actually the New Guinea starfish (Culcita novaeguineae).

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

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

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

The Linkia starfish (Linckia laevigata) is bright blue in color and has sausage-like rays.

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

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

In a young starfish, the skeletal elements are hidden under the skin, but over time the skin over some calcareous spines wears off and they become visible from the outside. It is these spines that give starfish their spiny appearance.

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

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

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

Finally, the third element influencing appearance starfish are pedicellaria. Pedicellariae are modified needles that look like tiny tweezers. They play an important role in the life of a starfish; with their help, it cleans the upper side of its body from debris and sand. All skeletal elements are connected to each other by muscles, so after the death of a starfish, its skeleton crumbles into calcareous plates and not a trace remains of the animal.

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

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

Scalloped sea stars (Patiria pectinifera) climb on the seaweed.

These animals have a special body system - ambulacral. Essentially, this system consists of 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 flex and move. The central part of this system is the ambulacral legs - 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 is able to perform miracles. For example, it is able to climb a vertical surface, can stick to the glass of an aquarium for a long time, can rear up, swelling up like an angry cat, or maybe, grabbing hold of two rays, push the valves of a mollusk shell apart. And all this is done by an animal practically devoid of a brain and eyes!

Translucent ambulacral legs are visible on the underside of the beam.

To be fair, it is worth noting that starfish do have some sense organs. These are the eyes located at the ends of each ray. The eyes are very primitive and only distinguish between light and darkness; starfish cannot see objects. Starfish are capable of detecting chemicals (similar to smell), but they sense them differently. Some species are very sensitive and can crawl to the bait for several days in a row by smell, while 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 covers them from above, and also always try to feel their way with the help of small tentacles at the end of each ray. The sense of touch tells the starfish whether it has encountered a victim or a predator. The starfish's brain is replaced by a group of loosely interconnected cells. What is surprising is that despite such a primitive structure nervous system starfish can develop elementary conditioned reflexes. For example, individuals who were often caught in nets began to get out of them faster than those who were caught for the first time.

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

Another strong, literally and figuratively, system of starfish is the digestive system. The mouth of these animals is located in the center of the disc 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 even becomes overgrown), preferring to remove undigested food residues through the mouth. The stomach of these invertebrates has outgrowths extending into rays; reserves of nutrients are deposited in them in case of famine. And starfish regularly starve because they stop feeding during reproduction. The stomach in many species can turn outward through the mouth opening, and it stretches like rubber, taking any shape. Thanks to its expandable stomach, the starfish can digest prey that is larger than itself. There is a known case when the starfish Luidia swallowed such a large sea ​​urchin that she died, unable to spit out its remains.

A tiny anal opening is visible in the middle of the central disc of Phromia monilis.

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 or lungs, so starfish are sensitive to lack of oxygen. They also cannot tolerate desalination of water, so they are found only in 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 sea star Freyella.

The name of this starfish speaks for itself - fromia elegans.

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

Starfish in shallow water.

Sea stars most time crawling along the bottom. They do this very slowly, the usual speed of a medium-sized individual is 10 cm per minute, but a starfish can “hurry up” at a speed of 25-30 cm per minute. If necessary, these animals climb onto stones, corals, and algae. If a starfish falls on its back, 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 turns its body and takes its usual position. Some species are even capable of swimming awkwardly over short distances. Starfish can be called sedentary animals; their tagging has shown that they do not move more than 500 m from the place of initial catch.

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

Despite their outward primitiveness and apparent helplessness, starfish are formidable predators. They are quite voracious and never refuse prey, with the exception of the period of gestation. Only deep-sea species feed on silt, from which they extract food particles; kulcite sea stars, which prefer to eat fouling on corals, can also be called conditionally “non-predatory”. All other species actively hunt other animals.

Not at all romantic relationship connected this pair: the sea star Solaster dawsoni eats the spiny hippasteria spinosa.

Most starfish are picky; they eat everything they can hold with their hands and whatever their “rubber” stomach can reach, not disdaining carrion. Some species can only feed on a certain type of food: sponges, corals, gastropods.

The pretty starfish (Pentagonaster pulchellus), 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 bivalves. The star catches the sea urchin by crawling and eats it with its mouth. Bivalves have shells whose valves close tightly in case of danger, so starfish treat them differently. First, the starfish sticks with two rays to the shell flaps, and then begins to move them apart. It must be said that the ambulacral legs are firmly glued to the substrate thanks to an adhesive lubricant, and one single ambulacral leg can develop a force of up to 30 g! And on each ray of the starfish there are hundreds of them, so she, like a real strongman, pushes the shells apart with an effort of several kilograms. However, the starfish does not need to spread the shell flaps to their full width; for a hearty lunch, a gap of 0.1 mm is enough for it! The starfish turns its stomach into this truly microscopic gap (it can stretch up to 10 cm) and digests the mollusk in its own home.

Asteria starfish (Asterias rubens) reaches out to a clam.

Most starfish are dioecious; very few species have both male and female gonads. The gonads are located in pairs at the base of each ray. In the asterine starfish, the young are first male and then change to female. A special exception is the ophidiaster starfish, which has no males at all! Females of this species lay eggs without fertilization, a process called parthenogenesis. During mating, males and females connect their rays and release sperm and eggs into the water. The number of eggs depends on the type of development of the larvae 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, the eggs hatch into a free-swimming larva, 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 large reserves of yolk, so it does not feed and immediately turns 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. During this period, a caring female rests only on the tips of the rays, and arches her body into a dome, under which the offspring are 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 the life cycle of sea stars; it is during this period that the young can be carried by currents over very long distances.

The starfish larva has bilateral symmetry.

In addition to sexual reproduction, starfish can also reproduce asexually. Most often this occurs in multi-rayed 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 following traumatic damage to the body. If a starfish is artificially divided into several parts, then a new organism will be formed from each. Even one beam is enough for restoration, but a piece of the central disk is required. Starfish grow slowly, so they look lopsided for many months.

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

In their natural environment, sea stars have very few enemies, since the sharp spines, which can be poisonous, scare away large predators. In addition, these invertebrates, on occasion, try to bury themselves in the sand so as not to attract attention. Most often, sea stars fall into the teeth of sea otters and seagulls.

A seagull caught a starfish.

But the starfish Astropectens is friends with polychaete worms. One individual can have up to five cohabitants, who prefer to stay on the underside of the body close to the star’s mouth. The worms pick up the remains of her prey and even stick their heads into her stomach! The echinaster sea star is inhabited by a special type of ctenophore, which cleans 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 waters, but starfish were of no economic interest to them. Only in China are they sometimes eaten, while attempts to feed starfish to domestic animals can lead to the death of the latter. This is likely due to toxins that some species accumulate by eating coral and poisonous shellfish. But with the development of the maritime economy, people began to classify these animals as their enemies. It turned out that starfish often eat bait in bottom crab traps, and also raid plantations for breeding oysters and scallops. In a few years (that’s how long it takes to grow oysters), starfish can destroy an entire oyster bank. At one time they tried to destroy the predators by cutting them into pieces, but this only increased their numbers, because from each stump a new starfish grew. Then they learned to extract starfish with special trawls and kill them with boiling water.

A very impressive mosaic starfish (Iconaster longimanus).

The worst pest was the acanthaster starfish, or crown of thorns. This very large echinoderm feeds exclusively on corals; after itself, the crown of thorns leaves only a white lifeless path on the coral reef. At one time, these stars multiplied so much that they literally ate a huge section of the Great Barrier Reef off the coast of Australia. The unique geological formation was under 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 it is not fatal. Specially trained divers collected the acanthasters into bags with sharp spikes or injected a lethal dose of formaldehyde into the body of the starfish. Only in this way was it possible to pacify the invasion of voracious predators and save the reef. Nowadays, all species of starfish are in a safe condition and do not need protection.

The crown of thorns eats the coral.

For many of us, knowledge about stars ends with the fact that they are 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 the shape of the starfish often corresponds to its name, sometimes unusual individuals with bizarre shapes are found. For example, starfish may have a sun-shaped shape, multiple rays, or their shape may be rounded. The largest starfish can reach 1 meter in diameter and their weight can reach 5 kilograms. Very interesting are solar stars, which are more active than their relatives and are able to quickly pursue their prey. Thanks to their strength, they can easily break the shell of mollusks 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 lack brains and lack blood. To get all the nutrients, oxygen and other important fluids it needs, the starfish pumps seawater 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 arms there are about 15 thousand tiny suckers, thanks to which the starfish moves.

4. Cannibalism
It turns out that these cute creatures are actually true predators. They are capable of attacking their own kind and can easily feast on the small offspring of their own species.

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

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

7. Whimsical Pillow
At first glance, pillow stars are difficult to classify as starfish because of their bizarre shape. Their swollen body looks 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 long ago, the low resistance of sea stars to infections was discovered, which is why some species began to die out at a catastrophic rate. The main reason for the death of starfish is environmental pollution.

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

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

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 on the seabed

These extraordinary decorations of the seabed have existed on the planet for quite a long time. They appeared about 450 million years ago. There are up to 1600 types of stars. These animals inhabit almost all 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.

Animals can have rays from 4 to 50, sizes range from a few centimeters to a meter. The lifespan is about 20 years.

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

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

Structural features

It is interesting how starfish reproduce and feed. Biology classifies them as invertebrate echinoderms. The starfish does not have blood as such. Instead, the star's heart pumps sea water enriched with certain microelements through its vessels. Pumping water not only saturates the animal's cells, but also by forcing fluid into 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 consists of calcite and develops inside a small star from almost a few calcareous cells. What and how starfish feed largely depends on the characteristics of their structure.

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

Cunning hunters

Many people are interested in how starfish eat. A brief description of the structure of their digestive system can be found below. These amazing beauties create the impression of complete security. In fact, they are sea predators, voracious and insatiable. Their only drawback is their low speed. Therefore, they prefer a stationary delicacy - mollusk shells. The starfish eats scallops with pleasure, and is not averse to eating sea urchins, sea cucumbers, and even fish that carelessly swim too close.

The fact is that the starfish has practically two stomachs, one of which can turn outward. An unwary prey, captured by the pedicellariae, is transferred to the mouth opening in the center of the rays, then the stomach is thrown over it like a net. After this, 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, entwines the shell with her rays, places her mouth opening opposite the slit of the shell and begins to move the shells apart.

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

Features of the structure of the digestive system

The predator does not have any devices for capturing prey. The mouth, surrounded by a ring 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 doors. In the center of the aboral side, a narrow, short intestine opens, extending from the stomach. What a starfish eats largely depends on the unusual structure of its digestive system.

Love of the stars at the bottom of the ocean

Most starfish are heterosexual. During 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 cunning creatures try to deposit nutrients in advance for the entire duration of mating.

The gonads are located in stars near the base of the rays. When mating, the female and male individuals connect the rays, as if merging in a tender embrace. Most often, eggs and male reproductive cells end up in sea water, where fertilization occurs.

If there is a shortage of certain individuals, stars can change sex to maintain the population in a certain area.

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

Reproduction by division

A completely extraordinary ability of starfish is reproduction by fission. The ability to grow a new ray arm exists in almost all animals of this species. A star caught by a beam by a predator 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 remains on the beam, after a certain time a full-fledged starfish will grow from it. Therefore, it is impossible to destroy these predators by cutting them into pieces.

Who are starfish afraid of?

Representatives of this class have few enemies. Nobody wants to mess with the poisonous needles of sea celestials. Animals are also able to secrete odorous substances to scare away particularly voracious predators. In case of danger, the star can bury itself in silt or sand, becoming almost invisible.

Among those who feed on starfish in nature, large seabirds predominate. On the shores of warm seas they become prey for seagulls. IN Pacific Ocean The star is not averse to feasting on cheerful sea otters.

Predators harm underwater plantations of oysters and scallops - what the starfish eats. Attempts to kill animals by cutting them into pieces led to an increase in the population. Then they began to fight them, bringing the stars ashore and boiling them in boiling water. But there was nowhere to use these remains. There have been attempts to make fertilizer from animals that also repels pests. But this method was not widely used.