House of echinoderms coral. Echinoderm crinoids of coral reefs. Structure of the ambulacral system

Invertebrates include animals lacking an axial skeleton. A bunch of the most beautiful inhabitants seas - corals, sea anemones, crustaceans - these are invertebrates, and a considerable part of fans of this species buy an aquarium because of them. Invertebrates are much more sensitive to water quality than fish, which means they will require more sophisticated equipment to maintain. It is important to remember that copper-based fish treatments are harmful to most invertebrates.

Corals

The most famous among invertebrates are the inhabitants of tropical seas and oceans, striking with their bright colors and bizarre shapes. The body of most corals contains symbiotic organisms - zooxanthellae, which often determine the color of the coral. Zooxanthellae – unicellular algae, which are synthesized for coral organic compounds and oxygen, so the correct type of lighting is of great importance for keeping corals in aquariums. The skeleton of corals may consist of either calcium or other horn-like structures. To build it, different types of corals need many trace elements, such as strontium, magnesium, iodine, etc. The key to successful maintenance is knowledge and constant monitoring of the presence of microelements. Corals – colonial organisms, each individual element of which is called a polyp and is connected to others.

Madrepore corals

They have a calcium skeleton and are reef-building corals. Over millions of years of existence, madrepore corals have worked hard on the appearance of the old Earth. The most sensitive aquarium organisms that require perfect quality And chemical composition water. Therefore, by the time madrepore corals are placed in an aquarium, the environment in the latter must be absolutely stable. In addition, this type of coral does not accept proximity to a large number of fish. Individual polyps different types can vary in size from 1-2 mm to 20 cm in diameter. Madrepore corals have chemical means of defense (“burn”) and can wage real “wars” with each other, so when moving into an aquarium, it is worth calculating in advance the availability of free space between the corals, taking into account their future growth.

Tube corals

There are different colors, polyps are small - up to 1.5 cm, and in the colony they are interconnected, forming large swaying surfaces. Some - such as tubipora - have a tubular skeleton like a honeycomb, into which they can retract when danger arises. Other species have no skeleton at all.

Soft corals

The skeleton is represented by separate internal needles, due to which these corals can significantly change their volume depending on conditions. As a rule, they are highly branched and look like small underwater trees. Different species have different dependence on light, but it is easier to keep light-loving species in aquariums, since they do not need additional live food.

The most suitable for “beginner lovers” of corals. They have a dense structure and consist of small polyps that can “retract” or “extend”. At good conditions content and sufficient quantities of essential microelements can very quickly increase in size.

Horn corals

Just like soft corals, they are popular because of their relative unpretentiousness, fast growth and spectacular appearance.

Anemones (anemones)

Unlike corals, they consist of only one polyp, do not have a rigid skeleton and are filled with water. They are interesting due to the large “selection” of colors and sizes, as well as various types of “stinging” tentacles, with which you need to be especially careful. Sea anemones are excellent eaters of captured food, and many of them live in symbiosis with clown fish. The latter feed, clean and protect “their” sea anemone, in return receiving an underwater “home” protected from predators. It should also be noted that the sea anemone can actively move around the aquarium, causing inconvenience to other invertebrates. You need to especially carefully monitor the location of the pumps in the aquarium - there are often cases when sea anemone is “sucked” into the pumps and “grinded” into fine dust.

Disc anemones and zooanthids

As a rule, they live in large groups, reproduce well in captivity and are not too whimsical.

Crustaceans

There are about 40 thousand species of crustaceans in nature, but only relatively few are suitable for keeping in an aquarium. Crustaceans are chosen not only for unusual shape and coloring, but also for their “sanitary” features - they usually dispose of leftover food. All crustaceans molt regularly, shedding their exoskeleton (shell), and the empty shell looks so impressively like a living crustacean that some mistake this moment for the death of the animal. Large crustaceans can lead a predatory lifestyle and be dangerous to small fish. On the other hand, many small shrimp and hermit crabs will be useful even in a reef aquarium.

Echinoderms

Echinoderms include such well-known inhabitants of the sea as starfish, sea urchins, as well as lesser-known brittle stars, sea ​​cucumbers and sea lilies. Many of starfish are predators and can harm or eat corals. Many starfish regenerate well, that is, they restore own body even with significant damage. So, for some of them, a new starfish grows over time from each “torn off” ray. In turn, many of another popular class of echinoderms - sea ​​urchins– feed on fouling and algae, although some do not disdain coral polyps. Depending on the species, their needles can have different lengths and shapes. It should be remembered that the injections of some hedgehogs - for example, diatoms - are extremely painful, while other representatives are completely poisonous. But sea cucumbers are so named because they really resemble large cucumbers in shape, with tentacles at one end of the body that filter food. When keeping sea ​​cucumbers you need to pay attention to the fact that in the event of danger, some species release toxic substances into the water, which in the confined space of an aquarium is destructive for all its inhabitants.

Shellfish

It is very numerous (about 120 thousand species) and diverse group animals. Many bivalves are suitable for keeping in an aquarium, the most popular being Tridacna species. Bivalve mollusks feed by filtering water; in addition, the bodies of many of them, like corals, contain zooxanthellae. Gastropods, as a rule, are not very popular, since in addition to plant fouling they can cause harm to corals by eating them. But with live rocks, as a rule, small species enter the aquarium, eating fouling and - which is very useful for the aquarium environment - decay products. Mollusks also include cephalopods, such as cuttlefish and octopuses. Keeping the latter is also possible in marine aquariums, but it is quite complicated by the peculiarities of their diet - cuttlefish and octopuses can destroy all living organisms in the aquarium, so they need a separate microcosm.

Worms

Among all the earthly diversity of worms, the aquarium is mainly of sessile polychaete worms. They typically live in tubes of mucus or a horn-like substance from which protrudes a corolla of brightly colored tentacles. With them the worm filters water and receives food. Representatives of other groups of worms can also be observed in aquariums - on live rocks and in the ground. They are often additional and natural food for fish.

Echinodermata (Echinodermata), a type of marine invertebrate animal. They appeared in the Early Cambrian and reached great diversity by the end of the Paleozoic. Dimensions from a few millimeters to 1 m (rarely more - in modern species) and up to 20 m in some fossil crinoids. The body shape is varied: star-shaped, disc-shaped, spherical, heart-shaped, cup-shaped, worm-shaped or flower-shaped. About 10,000 fossil species and about 6,300 modern ones are known. Of the 20 known classes, 5 have survived to this day, belonging to subphyla: crinozoans (sessile forms, oriented with the mouth upward, with the only class crinoids), echinozoans (combines sea urchins and holothurians) and asterozoans (includes starfish and brittle stars). According to another classification, representatives of the last 2 subtypes are combined into the subtype Eleutherose.

All modern echinoderms are characterized by the presence of an ambulacral system and pentaradial symmetry; the latter extends in many cases to the outline of the body, the location of individual organs (nervous and circulatory system) and skeletal details. Deviations from pentaradial symmetry in modern echinoderms (for example, in holothurians) are a secondary phenomenon; at the same time, the homalazoans of the early Paleozoic were initially devoid of radial symmetry.

In most modern species, the mouth is located in the center of the body (on the oral side), and the anus is at the opposite pole (on the aboral side). The intestine is poorly differentiated, has the shape of a long narrow tube, spirally twisting clockwise, or sac-like; in some groups it is secondarily blindly closed. There are no digestive glands. Circulatory system consists of a perioral annular vessel and radial canals extending from it without their own walls - a system of lacunae. There is no gas exchange in this system; it serves to transport nutrients from the intestines to all parts of the body. Weak blood movement occurs due to the pulsation of the heart - a plexus of blood vessels surrounded by epithelial-muscular tissue. The function of the respiratory organs is performed by the ambulacral legs, the posterior part of the intestine and other formations. Excretion products are removed by coelomocytes, ambulacral legs and through thin-walled areas of the body.

Nervous system primitive, without a pronounced brain center. It consists of 3 rings, from each of which there are 5 radial nerves that do not have direct contact with each other. Thus, we can talk about the presence of three nervous systems in echinoderms. In accordance with this, they distinguish ectoneural (dominant, predominantly sensory, located on the oral side in the integumentary epithelium), hyponeural (controls the motility of skeletal muscles, connective tissue cells and is located in the middle layer) and aboral (controls motor function, predominates in crinoids, weakly developed in other echinoderms) systems. Echinoderms are dioecious (rarely hermaphrodites). The ducts of the reproductive glands open outward. Fertilization is mainly external. During metamorphosis, the swimming larva is transformed from a bilaterally symmetrical one into a radially symmetrical adult animal.

Lit.: Beklemishev V.N. Fundamentals comparative anatomy invertebrates. M., 1964. T. 1-2; Invertebrates: a new generalized approach. M., 1992.

S. V. Rozhnov, A. V. Chesunov.

Echinoderms are represented on reefs by stemless sea lilies - comatulids, holothurians, sea urchins, brittle stars and starfish. These main groups achieve significant species diversity when endemism occurs in the composition of their communities in areas of individual and especially isolated reef systems, such as the reefs of the Red Sea or the Caribbean (Clark, 1976). More than 1000 species of echinoderms live on the Indo-Pacific reefs, about 150 species live on the reefs of the Western Atlantic, and there are only 8 species common to these two large zoogeographic regions. Such isolation of the echinoderm faunas of these regions is similar to the isolation of the faunas of the corals living in them. The endemism of the echinoderm fauna in certain areas is expressed, in particular, in the fact that out of 1027 species inhabiting the Indo-Pacific reefs, there are only 57 species that inhabit this region from end to end. On average, within individual reef systems there are usually from 20 to 150 species of echinoderms. Thus, the number of their species in the Red Sea is 48, in Caribbean- about 100, on the reefs of the Philippines - about 190, in the area of ​​​​the Great Barrier Reef - about 160 (Marsh, Marashall, 1983).

The groups of echinoderms listed above, excluding starfish, form fairly dense communities and monospecific populations on reefs and especially in shallow water zones of the lagoon, flat and outer slope, the most important element free-living macrobetos. Their functional role as a component of the reef ecosystem is also great. They occupy all the main trophic niches. Among them there are filter feeders (brittle stars, sea lilies), detritivores and ground feeders (brittle stars, sea cucumbers), phytophages (sea urchins) and predators (starfish, as well as partially urchins and brittle stars).

Echinoderms play a significant role in the regeneration of nutrients (Webb et al., 1977) and have a significant impact on the processes of reefogenesis. They have a massive calcareous skeleton, constituting up to 90% of their body weight. Their skeletal elements serve important source supplies of carbonate material. The consumption of periphyton and spat macrophytes of corals by hedgehogs and stars has a significant impact on the formation of coral communities, as well as the consumption of corals themselves by stars and hedgehogs, especially the star Acanthaster. Ground-feeding holothurns, passing huge masses of coral sand through their intestines, significantly influence the formation of bottom sediments and the production processes occurring in them. Finally, echinoderms serve as a source of food for many mollusks and fish, and sea cucumbers are one of the main objects of fishing on the reefs.

Currently we have enough complete information in the composition and structure of communities of reef echinoderms, about the nutrition and reproduction of some of their groups (Endean, 1957; Clark, Taylor, 1971; Clark, 1974; 1976; Marsh, 1974; Lisddell, 1982; Yamaguci, Lucas, 1984). Information about their quantitative distribution is very fragmentary. Estimating the population density of most of the dominant species of urchins, brittle stars, crinoids and stars is complicated by the fact that these predominantly nocturnal animals hide in the shelters of rocky flats during the day and are difficult to count. Therefore, reliable quantitative data are available only for holothurians (Bakus, 1968).

A couple of days ago, we were sitting on the beach, swimming, frying meat, and then one girl said:
“And I saw a fish with a human face in Italy!”
- Screw you, I don’t believe her...
She takes out her phone and shows this fish. As it turned out, this is a Napoleon fish.

Yes, life in the ocean is mysterious and beautiful. They are also found in salty waters by their nature, which sometimes makes it hard to believe that they appeared on Earth thanks to evolution alone. For example, few people know that sharks lack bladder, and the horn of narwhals, northern whales, is nothing more than an erupted tooth.
So, let's admire the most bizarre and: from huge to tiny and harmless.

1

The biggest bivalve, whose prototype can be found in various animated films. Its shell has a characteristic relief, and its length reaches 1.5 meters. This giant can easily live for several centuries and gain weight up to 300 kilograms.
Oddly enough, the mollusk is capable of bearing pearls that match its size. In 1934, the largest tridacna pearl was found, weighing 6.3 kilograms. The cost of this splendor is estimated at 40 million dollars.

2

The largest jellyfish in the world. The dome of this giant grows to 2 meters in diameter, and the length of the tentacles reaches 20 meters.

3

The most ancient representative of stingrays, which appeared in the era of dinosaurs and has successfully survived to this day. The largest individual reaches 7.4 meters in length, with a quarter of the body occupied by the saw itself.

4

A long and distinctive fish, which is nicknamed the herring king because of the impressive growth on its head. The usual length of this creature reaches 3.5 meters. The largest specimen was 11 meters long and weighed 272 kilograms.
The belt fish is included in the Guinness Book of Records as the longest lobe-finned fish.

Without a doubt, a very strange fish, resembling in its appearance both the moon and the month at the same time. The body size reaches 3 meters in length, and weight – up to 2 tons.

6

Some mistakenly attribute this creature to jellyfish, but in fact it belongs to siphonophores - a large colony of organisms that unite into a single mechanism. When spread, it reaches 50 meters and is extremely poisonous.

7

The crown echinoderm is the most dangerous eater of coral reefs. In a year, a starfish can gnaw up to one and a half kilometers of the coral zone. The needles of this killer reach 3 centimeters and can cause severe poisoning even in humans. The star also has an impressive size among all other representatives of its class: more than 50 centimeters in diameter. The number of rays by average standards is also the most significant - 17-19.

8

This subclass of echinoderms has a second name - snaketails. Unlike starfish, the legs of these animals stand out in contrast against the background of the body.
The head of the Gorgon is the most unusual and most big representative among brittle stars. The span of the rays of some specimens can reach two meters.

9

Extraordinarily beautiful and graceful animals. With their roots they cling to a hard surface and spread bristly branches. And the bright colors in the color give them a resemblance to flowers.
Crinoids are another class of echinoderms. They drive night look life and feed on small plankton. The number of arms can vary from 10 to 200 rays. And the length of the stem ranges from 10 to 50 centimeters.

10

This little creature touches with its appearance and has many names. The most sonorous of them are: anumara crab and lobster fairy. In fact, the lobster fairy is not a lobster at all, but a well-disguised crab. The pink-purple miracle could well pass for a sophisticated monster, if not for the size of the body (1.5 centimeters in length).

Kingdom: Animalia, Zoobiota = Animals

• Class: Asteroidea de Blainville, 1830 = Starfish
• Class: Crinoidea = Sea lilies
• Class: Echinoidea = Sea urchins
• Class: Holothurioidea = Sea cucumbers
• Class: Ophiuroidea Gray, 1840 = Brittle stars, darters

Phylum: Echinodermata = Echinodermata

• Read: Type Echinoderms * Poisonous Echinoderms
• Crown of thorns starfish * Slow moving starfish

Echinodermata (Echinodermata) are a phylum of marine benthic animals, which currently includes five modern classes, including starfish, sea urchins, holothurians, etc. Listed below are the five modern classes of the phylum Echinodermata, which are classified into three subphyla . It should be borne in mind that there are apparently much more extinct classes.

Subphylum Crinozoa or Pelmatozoa
Class: Sea lilies = Crinoidea
Subphylum Asterozoa
Class: Starfish = Asteroidea
Class: Brittle stars or darters = Ophiuroidea
Subphylum Echinozoa
Class: Sea urchins = Echinoidea
Class: Holothurians or sea cucumbers = Holothuroidea

Representatives of the phylum Echinodermata appearance They are not similar to any other animals and are characterized by the fact that adults have radial (beam) symmetry, but their larvae have bilateral symmetry. That is why radial symmetry for representatives of the echinoderm type is secondary acquired, in contrast to some other primitive animals that also have radial symmetry, in which such symmetry is primary. In the process of individual development, when the larva begins to transform into an adult animal, left-hand side her body begins to grow rapidly at the expense of the right, which as a result of such disproportionate growth is completely absorbed. And the new body that develops from the left side of the larva is divided into five parts. They are symmetrically located around the body axis giving radial symmetry. Along with this, many species of echinoderms have a spherical or disc-shaped shape, while their symmetry is not immediately apparent, while in some other groups of species the body rays continue to branch, resulting in a complex tree-like body structure.

Echinoderms, in addition to the unusual symmetry of the body, are characterized by the presence of a dermal calcareous skeleton, the intensive development of which develops, especially in sea urchins, into external appendages of various structures, such as spines, spines or pedicellariae. Echinoderms are the owners of a completely unique system for the entire animal kingdom - the ambulacral system. It consists of many small legs that are controlled by the hydraulic pressure of the internal fluids of the body and therefore can move in different directions. The ambulacral system performs numerous functions for the body of echinoderms, and primarily motor functions: on the one hand, moving the animal itself in space, and on the other, transporting food particles to their mouth opening in sessile species.

The sensory organs of echinoderms are quite diverse, but primitive in structure. They are represented by various sensory cells that are diffusely distributed throughout the body and perform the functions of touch, vision and chemical sense. In most echinoderms, light-sensitive cells are distributed throughout the body, but in some species these cells can be concentrated in special organs of vision - the ocelli. The nervous system of echinoderms is very primitive, and it consists of a perioral nerve ring and radial nerve cords located in the skin epithelium.

Paleontological evidence suggests that echinoderms arose back in the Precambrian era. And in the early Paleozoic there were, according to some estimates, about 20 different classes, most of which have now become extinct. At the same time, the echinoderms that exist in our time are quite prosperous animals, and there are about 6-7 thousand species of them in the modern fauna.

If the sizes of some extinct species of echinoderms were up to 20 m, then the sizes of modern species range from a few millimeters in length (diameter) to a meter. The body shape can be stellate, spherical, disc-shaped, barrel-shaped, heart-shaped and even worm-shaped, and in echinoderms such as sea lilies it more closely resembles a flower. Despite all the diversity of forms, all echinoderms have pentaradial symmetry at one or another stage of life, and this despite the fact that some species, as a result of individual development, already acquire bilateral symmetry for the second time.

The development of echinoderms necessarily involves the stage of a free-swimming larva followed by its metamorphosis. Some species are capable of bearing embryos until the formation of juveniles. Although most species of echinoderms are dioecious organisms, few of them are hermaphrodites. Fertilization in echinoderms is usually external, since they sweep the reproductive products into the water.

Echinoderms are exclusively marine animals that live on the bottom from the littoral zone to almost extreme depths. They practically cannot tolerate noticeable changes in water salinity, since echinoderms are not capable of regulating the salt composition of body fluids. Moreover, at great depths, echinoderms, mainly holothurians, are the dominant group of benthic animals. By type of feeding, many species of echinoderms are detritivores, but among them there are also polyphags, such as many brittle stars, and predators, such as most starfish, and herbivores, such as many sea urchins.