Big starfish. How starfish reproduce. Interesting facts about starfish

Mysterious animal - starfish. First, STAR. Where else can you find such a natural configuration. Secondly, for some reason it initially seemed to me that it was some kind of algae or coral. Look at the variety and beauty of these stars! However, watch further video about how they eat 🙂

(Total 28 photos)

Post sponsor: Become one of us and many problems will be solved by themselves! Details

1. Starfish are veterans of the seabed, they appeared more than 450 million years ago, ahead of many forms of modern inhabitants of the underwater depths.

2. They belong to the class Echinoderms, being relatives of sea cucumbers, brittle stars, sea lilies, holothurians, sea urchins - at present there are about 1600 species that have a star-shaped or pentagonal shape.

4. In a starfish, despite its inactivity and lack of a head as such, the nervous and digestive systems are well developed. And why, in fact, "echinoderms"? It's all about the hard skin of the starfish - on the outside it is covered with short needles or spikes. Conventionally, these bizarre creatures can be divided into three groups: ordinary starfish; feather stars, named for their writhing rays (up to 50!), and "fragile" stars that cast their rays in case of danger.

5. True, it will not be difficult for this animal to grow new ones for itself, and new stars will soon appear from each beam. How is this possible? - Due to the characteristic feature of the structure of the star - each of its rays is arranged in the same way, and contains: two digestive outgrowths of the stomach, performing the function of the liver, a red eye spot at the tip of the beam, protected by a ring of needles, radial bundles of nerves, organs of smell (they are also suckers and a way of movement), papules located in a groove on the ventral side of the papules - skin gills in the form of thin short villi located on the back and producing gas exchange processes of the genital organs (usually two gonads on each ray) a skeleton consisting of a longitudinal row of vertebrae inside, and hundreds of calcareous plates with spikes, covering the skin and connected by muscles, which not only protects the animal from damage, but also makes its rays very flexible. The bodies of starfish are 80% calcium carbonate.

6. Thus, each ray of a starfish, once separated from its body, is quite viable and quickly regenerates. Well, connected together, the rays form closed systems in the center of the animal: the digestive system passes into the stomach from two sections and opens with a button-shaped disk that performs the function of the mouth; bundles of nerves are combined into a nerve ring. The main system of the starfish, which we deliberately left "for dessert" - ambulacral. This is the name of the water-vascular system, which serves as an echinoderm simultaneously for breathing, excretion, touch and movement, together with the muscles providing the musculoskeletal function. Channels extend from the perioral ring into each ray, from which, in turn, lateral branches lead to hundreds of cylindrical tubes on the surface of the body - ambulacral legs containing special ampoules and ending with suckers. An opening on the back, called the mandreopor plate, serves to connect this system to the external aquatic environment.

7. So how does the ambulacral system work? - It is filled with water under slight pressure, which, getting through the mandreopor plate into the near-oral canal, is divided into five channels of rays and fills the ampoules at the base of the legs. Their compression, in turn, fills the legs with water and stretches them. In this case, the suckers of the legs are attached to various objects of the seabed - and then sharply reduced - the ambulacral legs are shortened, and thus the body of the animal moves in smooth jerks.

8. Starfish are voracious predators, although there are exceptions in the form of herbivorous species that feed on algae and plankton. In general, the favorite delicacies of these animals are clams, mussels, oysters, scallops, littorins, sea ducks, reef-building corals and various invertebrates. The star finds its prey by smell. Having found a mollusk, it sticks with two rays to one shell valve, the remaining three - to the other valve - and a many-hour struggle begins, which the starfish always wins. When the mollusk gets tired, and the doors of its dwelling become pliable, the predator opens them and literally throws its stomach on the victim, turning it out! By the way, the digestion of food takes place outside the body of the animal. Some starfish are even capable of digging up prey hiding in the sand.

9. As for reproduction, for the most part, starfish are divided into males and females. Fertilization occurs in water, after which free-swimming larvae are formed, called brachiolaria. Unlike adults, their structure is subject to the laws of symmetry, and includes a ciliary cord necessary for collecting food particles (exclusively unicellular planktonic algae), a stomach, esophagus and hindgut. Usually, the larvae swim near an adult starfish of the same species - and after several weeks, under the influence of its pheromones, metamorphosis takes place with them: having fixed on the bottom, they turn into tiny (0.5 mm in diameter), but already five-link starfish. And these kids will be able to give offspring only after two or three years. If the larvae perform the function of dispersal of the species, and drift over long distances, they are able to delay their transformation into adults and not settle to the bottom for several months - while they can grow up to nine cm in length. There are also hermaphrodites among starfish - they bear their young in a special hatching bag or cavities on their backs.

10. Taking into account the large number of starfish, it is clear that they also affect the growth of populations of the species that are hunted. No one risks hunting them, since their bodies contain extremely poisonous substances - asteriosaponins. Being practically invulnerable, starfish are at the top of the marine food pyramid, and therefore their lifespan can reach 30 years. According to scientists, these brightly colored legendary inhabitants of the seas also make a significant contribution to the process of utilization of carbon dioxide produced, among other things, by industrial facilities on the planet - their share is about 2% CO2, that is, more than 0.1 gigatons of carbon per year , which for such seemingly small creatures, you see, is not at all weak!

Sunflower starfish, or pycnopodia (lat. Pycnopodia helianthoides) is the largest and fastest starfish in the world. This giant owner of two dozen tentacles, growing up to one meter in diameter, lives in the northeast Pacific Ocean, from the Aleutian Islands to the coast of California.

Pycnopodia, despite their impressive size, are very active and mobile creatures, as well as experienced hunters. Their favorite prey is sea urchins, which they catch with tenacious tentacles, almost as dexterous as the hands of octopuses. In the excitement of the chase, the pycnopodia develops a speed of 1 m / min., Covering a space of 0.5 sq.m with its body. At the same time, 15 thousand small legs, densely dotted with suction cups, sway under her body.

All this arsenal of a predator turns a starfish into a real machine for destruction, leaving no chance for the victim to escape. She swallows the sea ones whole, and after having dinner, she spits out the shell, completely devoid of needles.

In addition to hedgehogs, pycnopodia just as easily deal with hermit crabs, weakened fish, and snails. If the prey is too large, the predator simply opens its mouth wider, and if this does not help, it pushes its stomach out and digests the victim on the spot.

Once at the place of prey, the pycnopodia, forced to flee, sheds part of the tentacles. However, this is not a cause for concern - new ones grow back in just a few weeks.

Sunflower starfish can come in a variety of colors, from bright orange, red and yellow to brown or purple. Large specimens weigh more than 4.5 kilograms, and the number of tentacles varies from 16 to 24.

Sea stars are echinoderm invertebrates. The top of the starfish consists of a protective outer shell, below is a mouth and numerous ambulacral legs, which the star uses for locomotion and feeding. Most stars reproduce sexually, but asexual reproduction is also quite common.
Let's dwell on the methods of reproduction in more detail!

Damaged starfish regenerate very easily, rebuilding lost arms and damaged disk parts. Species of the genus Asterias can throw off their arm when injured. Experiments on Asterias vulgaris show that regeneration of the entire star can take place if there is one arm and one fifth of the central disk. If the disc fragment includes a madrepore plate, then regeneration will be successful even if there is less than a fifth of the disc. Once the disc and intestines are restored, the animal is able to resume feeding even before the intestines and hands are completely regenerated. Completion of regeneration is slow and sometimes takes a whole year to complete.

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. Species of the starfish genus Linckia, common in the Pacific Ocean and other areas of the World Ocean, are unique in their ability to throw off their arms entirely. Each individual hand, if not eaten by a predator, can regenerate a new body. Some starfish species reproduce clonally in the larval stage. They develop buds on their larval arms, which differentiate into new larvae.
With a few exceptions, starfish are dioecious. The ten gonads, two in each arm, resemble bunches or bunches of grapes. In non-breeding individuals, the gonads are wrinkled and occupy the bases of the arms. However, the gonads of sexually mature specimens fill the arms almost completely. Each gonad releases gametes through its own gonopore, usually located between the bases of the arms, although the gonopores of some starfish open sequentially along the arms or on the oral surface. There are several hermaphroditic species. These species include, for example, the common European starfish Asterina gibbosa, which is a protandric hermaphrodite. Most starfish release eggs and sperm into sea water, where fertilization takes place. They usually breed once a year and a single female can lay 2.5 million eggs.

Most starfish have hatched eggs and subsequent developmental stages are planktonic. Some starfish, especially those that live in cold waters, incubate large, yolk-rich eggs under an arcuate body, in aboral disk pockets, in brooding baskets formed by needles between the bases of the arms, under the paxilla, or even in the cardial stomach. In all species that bear eggs, development is direct. Asterina gibbosa is not an egg-bearing species, although it attaches its eggs to rocks and other objects, which is also unusual for this group of animals.

Development

Starfish embryos in most cases hatch from eggs and begin to swim at the blastula stage. The coelom arises from the terminal part of the developing primary gut as two lateral sacs that extend backward towards the blastopore (=anus). A small tubular process of the left coelom (protocoel + mesocoel = axohydrocoel) opens on the dorsal surface as a hydropore, which is a larval nephridiopore. By the time of the formation of the coelomic cavities and intestines, the larvae of the cilia in the integument are concentrated within the ciliary cord. It is a curved strip that runs along the surface of the larva, and later rises to outgrowths - the larval arms. Eventually, the anterior ventral part of the ciliary cord separates from the rest and forms a separate preoral loop. At this stage, the bilaterally symmetrical larva feeding on food suspended in the water column is called a bipinnaria.

The ciliated cords serve both for locomotion and feeding, while the larval arms increase their area. Phytoplankton and other tiny food particles are collected and thrown away in the opposite direction of the beating of cilia and then transported to the mouth.
Bipinnaria becomes brachiolaria with the appearance of three additional arms at the anterior end. These short arms (brachioles), ventral in location, bear adhesive cells at their ends. Between the bases of the hands is a glandular adhesive disc, or sucker. Three hands and an adhesive disc are used to attach when sinking to the bottom. As a rule, it is the brachiolaria that is the larval stage that sinks to the bottom and undergoes metamorphosis, however, in some starfish, such as Luidia and Astropecten, settling occurs at the bipinnaria stage.
Metamorphosis

When starfish larvae are ready to settle to the bottom, their positive phototaxis changes to negative. When settling, the brachiolaria is attached with its front end to the bottom with the help of brachioles and suckers, which form an attachment stalk.
During metamorphosis, a bilaterally symmetrical larva turns into a pentameric juvenile. In this case, the loss and reconstruction of larval tissues and the morphogenesis of new structures occur, and the rudiment of a juvenile star is formed behind on the left side of the body. In this case, the left side of the body of the larva becomes the oral surface, and the right side becomes the aboral. Part of the larval intestine is retained in the juvenile, but the larval mouth and anus are lost and subsequently re-formed in their new positions. The right larval mesocoel degenerates, but the left protomesocoel (axohydrocoel), including the pore canal and hydropore, is preserved and modified into the SCC. The arms of the juvenile star are new processes of the body wall, not connected with the larval arms. Eventually, a young starfish, less than 1 mm in diameter, separates from the larval stalk and crawls away on short arms:
Growth rates and lifespans of starfish vary widely, as observed in two species of the intertidal zone of the Pacific coast of the United States. Leptasterias hexactis bears a small number of yolk-rich eggs during the winter, and juveniles become sexually mature at the age of two years, when their weight reaches about 2 g. The average lifespan of this species is 10 years. Pisaster ochraceus produces large numbers of eggs each spring and development is planktonic. Sexual maturity is reached by the age of five with an animal weight of 70 to 90 g. Individuals can live for 34 years, breeding annually.

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 the structure of their digestive system can be found below. These amazing beauties give the impression of perfect security. In fact, they are 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 germ 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 shores of 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- amazing creatures that look so beautiful on the seabed! Today, friends, we want to tell you a little about them, starting with a general description.

Description of the starfish

echinoderms there are about 1600 species, but today we will list the main ones. The size of the stars ranges from 1 mm to 25 cm, it all depends on the species. Of course, each view is beautiful and colored in its own way, some stars are bright, while others are barely visible in the sea. The rays of the star serve as digestion, because it is in them that the processes and genital organs and the stomach itself are located. The starfish also has legs and a mouth!

The stars feed plankton, detritus, sea ducks, clams, oysters, mussels and even corals! BUT life expectancy it averages 20 years.

Interesting facts about starfish

The legs of a starfish are usually equipped with suction cups in order to make it convenient to move along the seabed.

Most starfish are predators

Stars are dioecious

Stars multiply right in the water, sweeping both sperm and eggs

Usually the fertilized "larva" is attached next to the parent, but some carry the baby in a special bag

HABITAT AND SPECIES OF STARS

Types of starfish

1. Luidia two-needle

2. Patiria scallop

3. Pacific Solaster

4. Henricia Hayashi

5. Lysastrosoma antosticta

6. Dystolasteria prickly

7. Letasteria black

8. Afelasteria japonica

9. Prickly eusteria

10. Reticulated eusteria

11. Ordinary Amur star

Where do starfish live

Sea stars are the oldest group of animals that have survived to this day! And oddly enough, a marine representative can be found in almost every salty sea and in every ocean. By the way, it is in those seas where there is normal salinity that starfish can be found on the shore! It is for this reason that mankind has known about them since ancient times.

VIDEO: ABOUT STARS IN THIS VIDEO, WE SUGGEST YOU WATCH THE DOCUMENTARY ABOUT STARS