What do echinoderms eat. Echinoderm inhabitants of the sea - Sea urchins

Holothurians, or sea cucumbers, can be called one of the strangest, most interesting and unusual inhabitants water. From the point of view they are animals, but their character traits and lifestyle make some think they are closer to plants. However, this is not at all the case, but this does not prevent one from wondering how evolution even created this bizarre creature.

Facts about sea cucumbers

In total, there are as many as 1150 species of holothurians in the world, many of which are edible. Of these, about a hundred are also found in Russian waters.
Judging by archaeological finds, the first sea cucumbers appeared on Earth about 440 million years ago. They are older than many types of dinosaurs.
body sea cucumbers symmetrical, but very peculiar. For example, our bodies are symmetrical on two sides, and they have five.
It is impossible to overestimate the importance of holothurians for the world ecology. They process 80-90% of all plant and animal remains that settle on the bottom of the oceans ().
No matter how funny it may sound, but sea cucumbers breathe with the help of a cloaca, or anus. Through it, they draw water into their body, from which they already absorb oxygen.
The karapus fish hides inside sea cucumbers at a time when it is not looking for food. Moreover, it penetrates into it through the same aforementioned opening of the body.
Sea cucumbers feed by sucking sand and soil into the body, absorbing useful material and throwing waste back.
These amazing creatures can make their body both rigid and almost liquid. Thanks to this, they can seep into the narrowest gaps.
sea urchins and starfish are the closest relatives of holothurians ().
Sea cucumbers large species when mature, they can reach a length of up to 5 meters, and the smallest - only 3 centimeters.
The mouth of the holothurian is surrounded by small tentacles, which can be up to 30 pieces.
Some types of sea cucumbers, in case of danger, throw out their insides along with a liquid that is poisonous to most other marine organisms.
In some Asian countries, dried sea cucumbers are used as a folk pain reliever.
If a sea cucumber suddenly loses its intestines, it can grow a new one in a month or two.
No bacteria have ever been found in the cells of holothurians ().
Due to the popularity of edible sea cucumbers in some countries, they are purposefully bred on special marine farms.
During the year, sea cucumbers of medium-sized species (about the size of a human hand) sift through their bodies about 150 tons of sand and soil.
The life span of holothurians can reach 10 years.
Most of their species spend their entire lives at the bottom, but some live right in the water column without sinking down.
In the traditional Chinese medicine sea cucumbers are still actively used, as in local cooking.

Type Echinoderms - Echinoddermata - are exclusively marine forms with an internal skeleton formed by calcium carbonate crystals, and often with five-ray radial symmetry. This well-known group includes starfish, serpenttails (brittle stars), sea lilies, sea cucumbers (holothurians) and sea urchins. Their diversity was maximum in the Paleozoic: 6 modern classes are known, 15 are extinct.

Class Sea urchins - Echinoides - in the fossil state are known from the Ordovician, characteristic of post-Paleozoic marine deposits. There are up to 940 species of modern sea urchins.

Sea urchins. Photo: Revital Salomon

The body of sea urchins is usually almost spherical, ranging in size from 2-3 to 30 cm; covered with rows of calcareous plates. The plates, as a rule, are fixedly connected and form a dense shell (shell), which does not allow the hedgehog to change shape. According to the shape of the body (and some other features), sea urchins are divided into regular and irregular. At correct hedgehogs the shape of the body is almost round, and they are built according to strictly radial five-beam symmetry. At wrong hedgehogs the shape of the body is flattened, and they have distinguishable anterior and posterior ends of the body.

With the shell of sea urchins, needles of various lengths are movably connected (using an articular bag with muscle fibers). The length ranges from 1-2 mm ( flat hedgehogs, Echinarachniidae) up to 25-30 cm (diadem hedgehogs, Diadematidae). There is a species completely devoid of needles - Toxopneustes, whose body is dotted with pedicellaria. Quills are often used by sea urchins for locomotion, feeding and protection. In some species, they are poisonous, as they are connected to special poisonous glands. Poisonous species (Asthenosoma, Diadema) are distributed mainly in tropical and subtropical regions of the Indian, Pacific and Atlantic oceans.

In addition to needles, pedicellaria sit on the surface of the shell of sea urchins, and also, at the mouth opening, special organs of balance - spheridia. In some species, pedicellaria are also equipped with poisonous glands (Toxopneustes, Sphaerechinus).

The ambulacral system is common in echinoderms. Each ambulacral leg, equipped with a suction cup, passes through the skeletal plates of the shell with two branches (through 2 pores). The ambulacral legs of the underside are used by sea urchins for locomotion and burrowing. The legs of the dorsal side were transformed into organs of touch and breathing. In some species, ambulacral legs, along with needles and pedicellaria, take an active part in the process of cleaning the shell and feeding.

The mouth of sea urchins is located in the center of the lower (oral) side of the body; anal and genital openings - usually in the center of the upper (aboral) side. In regular sea urchins, the mouth is equipped with a chewing apparatus (Aristotelian lantern), which serves to scrape algae from stones. The Aristotelian lantern consists of 5 complex jaws, each of which ends in a sharp tooth. The teeth of the Aristotelian lantern are involved not only in the processing of food, but also in movement (sticking into the ground), and also presumably in burrowing. Irregular sea urchins that feed on detritus do not have a chewing apparatus.

The intestine does not have a radial structure, but is a tube that runs from the mouth opening in a spiral inside the body cavity. Sometimes an adnexal intestine runs along it, opening into the intestine at both ends. The respiratory organs are the external skin gills located near the mouth, the ambulacral system and the adnexa.

The sense organs and the nervous system are rather poorly developed. In addition to tactile ambulacral legs and spheridia, hedgehogs have primitive ocelli located on the upper side of the body.

Widespread in oceans and seas with normal salinity at depths up to 5 km; are absent in the low-salinity Caspian, Black and partially Baltic Seas. Widespread on coral reefs and in coastal waters, often settling there in the crevices and depressions of the rocks. Correct sea urchins prefer rocky surfaces; incorrect - soft and sandy soil.

Sea urchins are bottom crawling or burrowing animals. They move with the help of ambulacral legs and needles. According to some assumptions, with the help of the “Aristotelian lantern”, sea urchins drill holes for themselves in the rocks, even granite and basalt, where they hide at low tide and from predators. Other species burrow into the sand or simply cover themselves with pieces of shells, algae, etc.

Almost omnivorous. The diet includes algae, sponges, bryozoans, ascidians and a variety of carrion, as well as mollusks, small starfish and even other sea urchins. The purple hedgehog Sphaerechinus granularis easily copes with the mantis shrimp Squilla mantis. Species living on soft ground swallow sand and silt, digesting small organisms that come with them.

Sea urchins serve as food for lobsters, starfish, fish, birds, fur seals. The main natural enemy of the sea urchin is the sea otter. Having caught a hedgehog, the sea otter either twists it in its paws for a long time (sometimes after wrapping it in algae) to crush the needles and then eats it; or breaks a hedgehog with a stone on his own chest. The number of urchins eaten by sea otters is so great that the intestines, peritoneum and even bones of these marine mammals are sometimes stained with purple pigments of sea urchins.

The reproductive organs consist of vine-like gonads (usually five) that open outwards on the upper side of the body. Sea urchins have separate sexes; sometimes males are somewhat different in appearance from females. Development with planktonic larvae (echinopluteus); some Antarctic species are viviparous - eggs develop under the protection of needles on the upper side of the body or in the brood chamber, so that the young hedgehog leaves the mother fully formed.

Hedgehogs reach sexual maturity and commercial size in the 3rd year of life. According to the estimates of growth rings on the plates of the shells, the age of sea urchins is on average 10-15 years, with a maximum of up to 35 years.

Many sea urchins serve as an object of fishing. They are a traditional dish of the inhabitants of the coasts of the Mediterranean Sea, North and South America, New Zealand and Japan. Their milk is highly valued, and especially caviar, which contains up to 34.9% fat and 19.2-20.3% protein. The shell is a good fertilizer for marginal lands, as it contains a lot of calcium and phosphorus. In addition, modern research has established that the pigment isolated from the sea urchin (Subclass Real [correct] sea urchins - Euechinoidea

In Primorye, there are two types of regular sea urchins, which are found in abundance in any bay on coastal stones and rocks. This is a gray hedgehog Strongylocentrotus intermediate and a black hedgehog Strongylocentrotus unarmed.

Of these two species, the dark purple, almost black, unarmed sea urchin bears just longer and thicker quills than those of the gray urchin. Their tips are easily stuck into the body of a careless swimmer and, breaking off, remain in the body. gray hedgehog you won't see it right away. He covers himself with pieces of shells, pebbles, scraps of algae, which he sticks to the body and holds with ambulacral legs. However, this disguise, as a rule, does not save from swimmers. The gray sea urchin is one of the objects of industrial production, and several thousand tons are caught per year. Inochrome), has strong antioxidant activity.

Trepang is a marine invertebrate animal belonging to the type of echinoderms. Sea cucumbers, holothurians or sea capsules are called mollusks, whose body tends to shrink strongly at the slightest touch, becoming like a cucumber or an old egg capsule.

To date, there are 1150 species that differ in their structure, shape of tentacles, color and appearance. The closest relatives are starfish and hedgehogs. In Russia you can meet about a hundred species of these animals, the most popular of which are cukumaria (Japanese sea cucumber) and Far Eastern trepang: they are used to prepare healthy and delicious food. Sea cucumber reaches a size of up to half a meter, and its most big weight, known today is 1500 gr!

Trepang: description

Most often, these worm-like animals are found in the waters of the Japan and Yellow Seas, where they live at a fairly large depth (about 100 m or more). By appearance the mollusk resembles a cucumber (hence the name): it has elongated oval body, thick skin, on which long growths are visible, similar to thorns. Trepang has a number of healing properties and has been eaten for a long time.

The appearance of the holothurian

Holothuria - a unique inhabitant underwater world, similar at the same time to a huge worm and big caterpillar. The soft body of a mollusk can be either absolutely smooth or rough (depending on the variety) and covered with short or long outgrowths. Color - red, gray, green, brown or black.

Sea cucumbers also differ in size. Animals can be either very tiny (from 0.5 cm) or incredibly huge (up to five meters!), which is what attracts the interest of sea hunters.

The mouth of the holothurian is practically devoid of any devices for crushing and chewing food. It is located either at the front end of the body, or slightly shifted to the belly. The few forms of this marine inhabitant that have the ability to attach to rocks or burrow into silt are vaulted, flask-shaped or spherical in shape. This is explained by the fact that the anus and mouth of the trepang are slightly shifted to the back.

All sea cucumbers have characteristic tentacles located around the mouth. These processes are modified ambulacral pedicles. In various representatives of the trepang orders, the structure of the tentacles is not the same, and their number ranges from 8 to 30 pieces. The tentacles are short, thyroid-shaped, intended mainly for collecting nutrient material from the ground surface, tree-branched, covering a fairly large body of water when catching prey.

But, despite the fact that the holothurian has such unusual shape it is almost always possible to distinguish between the ventral and dorsal sides, but in its structure the belly of the sea cucumber does not morphologically correspond to that of other animals. Since these worm-like animals always crawl on their side, the names "dorsal" and "ventral" do not quite correspond to generally accepted concepts.

Most forms of sea pods does not have a clear separation of boundaries between head and body, however, in some species, some separation of the body from the head end can still be seen. Trepangs are very slow and move from place to place slowly stretching and contracting. However, their usual state is a quiet pastime lying on their side, which greatly facilitates their capture.

Composition and properties

Sea cucumbers can be safely called a dietary product, since they have a very low calorie content (only 33 kcal per 100 g). Beneficial features shellfish are determined by their composition. in sea cucumbers contains the following substances:

Holothuria is a unique natural substance, the use of which makes it possible to achieve a quick recovery after surgery or illness. Oriental medicine uses sterile sea cucumber meat to normalize metabolic processes, lowering blood pressure, stimulating cardiac activity, accelerating tissue regeneration, and even getting rid of bradycardia and tachycardia.

Thus, sea cucumbers have a beneficial effect on human health, and if you include them in your daily diet, you can avoid many diseases. Holothuria also has a healing effect on the joints, which is why it is widely used to treat arthritis. The elements that make up trepang meat will help reduce joint stiffness, as well as relieve pain.

Not only fresh sea cucumber meat has useful properties, but also extract from trepang. According to Chinese doctors, the extract of this mollusk, obtained according to a unique recipe, prolongs life, improves the functioning of the nervous and cardiovascular systems, and also helps to saturate the body with a complex of necessary elements and strengthen immunity. The use of extracts is especially recommended for people suffering from chronic diseases and pensioners.

Thus, trepang meat is a unique raw material for the production of medicines and medicinal extracts.

In addition, the sea cucumber found wide application in cooking. It is consumed canned, stewed or fried, as well as delicious salads.

However, there are also contraindications to the use of drugs based on trepang, as well as its meat:

Hyperthyroidism. The use of sea cucumber can cause an exacerbation of the disease;
hypertension. The product contributes to a significant decrease in blood pressure;
pregnancy and lactation;
age up to 15 years;
individual intolerance.

How to cook?

Preparing a sea cucumber for eating is not difficult at all. However, you must first prepare the product. To start dried shellfish should be thoroughly washed before complete disappearance black powder. Then put it in a container of water for a while to soak. Water should be changed periodically. After the actions taken, boil the sea cucumber in clean water until ready (at least three hours).

There are a huge number of dishes based on trepang. It can be a hodgepodge, soup, pilaf, salad, as well as all kinds of snacks. Sea cucumber can also be used as a filler for cutlets. Dishes containing this mollusk can be served with various sauces (especially spicy ones).

Trepang with honey gained particular popularity among gourmets not only for its unique taste, but also for its very useful properties.

Too dry mollusks should be soaked for several days, until the product ceases to exude the smell of iodine, and the water after washing it becomes completely transparent.

Sea cucumber storage

Store the dried product in a cool and dry place, away from sunlight. Already cooked or fresh sea cucumber, if necessary, can be frozen. However, you should not store trepang in the freezer for too long (more than two months), otherwise it will lose its beneficial properties.

The Japanese use sea cucumbers in their raw form. For this remove the entrails of the animal, cut it into small pieces seasoned with vinegar or soy sauce. Also the inhabitants of the islands Pacific Ocean and Japan, the gonads and intestines of the sea cucumber are used for cooking. These products are valued more expensively, the musculoskeletal bag of trepang.

In the world, canned sea cucumbers are in great demand, due to which some modern factories and firms European countries put the production of canned products from holothurian meat on stream. Now not only hunting for trepang is widely practiced, but also artificial breeding, including here, in Russia (Far East).

So, this seemingly unsightly and to some extent even nasty marine animal can not only save you from many ailments, but also provide you with a healthy and satisfying dinner.

Sea cucumber trepang

Echinoderms (Echinodermata)- a type of marine animal that includes: starfish, sea lilies, sea urchins, brittle stars and sea cucumbers. We know about 6000 living species of echinoderms. Most echinoderms are benthic animals that have a variety of feeding habits, including water filtering, carrion eating, and predation. Modern echinoderms, despite the fact that they evolved from sedentary ancestors, are able to move around.

Echinoderms have an endoskeleton composed of calcareous plates. In starfish and brittle stars, the plates have a flexible structure. In sea urchins, the plates are fused together, which gives the animals a rigid frame structure.

Echinoderms have predominantly five-ray radial symmetry, due to which their body is divided into five equal parts around the central axis. Echinoderms developed this symmetry through evolution based on the bilateral symmetry that their ancestors possessed. For this reason, the radial symmetry of echinoderms does not mean that they are closely related to other organisms with this type of symmetry, such as cnidarians.

Main characteristics

Key characteristics of echinoderms include:

calcareous endoskeleton, consisting of plates or bones;
radial (five-beam) symmetry;
water vascular system;
pedicellariae (small skeletal claws used by sea urchins and stars to clean and capture prey);
skin gills (skin tubercles used to absorb oxygen from the water).

Classification

Echinoderms are divided into the following taxonomic groups:

sea lilies (Crinoidea);
Sea stars (Asteroidea);
Ofiury (Ophiuroidea);
sea urchins (Echinoidea);
Holothurians (Holothurioidea).

Echinoderms are peculiar animals. They cannot be compared in structure with other types. these animals are reminiscent of a flower, a star, a cucumber, a ball, etc.

History of study

Even the ancient Greeks gave them the name "echinoderms". Representatives of this species have long been of interest to man. The history of their study is connected, in particular, with the names of Pliny and Aristotle; and in the 18th and early 19th centuries they were studied by many famous scientists (Lamarck, Linnaeus, Klein, Cuvier). most zoologists at that time correlated them with either coelenterates or worms. I. I. Mechnikov, a Russian scientist, found out that they are related to the enterobranchs. Mechnikov showed that these organisms are closely related to representatives of chordates.

Variety of echinoderms

In our time, it has been established that echinoderms are animals that belong to the group of the most highly organized invertebrates - deuterostomes. They appeared on our planet more than 520 million years ago. The remains of echinoderms are found in sediments dating back to the early Cambrian. This type includes about 5 thousand species.

Echinoderms are benthic, most of which are free-living organisms. Less common are those attached to the bottom with a special stalk. The organs of most organisms are located along 5 rays, but their number in some animals is different. It is known that the ancestors of echinoderms had bilateral symmetry, which from modern species have free-swimming larvae.

Internal structure

In representatives of echinoderms, a skeleton develops in the subcutaneous connective layer, consisting of calcareous plates and needles, spines, etc. on the surface of the body. As in chordates, in these organisms the secondary body cavity is formed by the separation of mesodermal sacs from the intestine. The gastropore during their development overgrows or transforms into the anus. In this case, the mouth of the larva is formed anew.

Echinoderms have circulatory system. Nevertheless, their respiratory organs are rather poorly developed or completely absent. It is necessary to briefly describe other features of echinoderms. These animals lack special nervous system organisms of interest to us. It is located partially in the skin epithelium or in the epithelium of invaginating parts of the body.

External structure

Characteristics of echinoderms should be supplemented by features external structure these organisms. The outer epithelium of the main part of echinoderms (with the exception of holothurians) has cilia that create a flow of water. They are responsible for the supply of food, gas exchange and cleansing the body of dirt. In the integument of echinoderms there are various glands (luminous and poisonous) and pigments that give these animals an amazing color.

The skeletal elements of starfish are calcareous plates, which are placed in longitudinal rows, usually with spines protruding outwards. The body of sea urchins is protected by a calcareous shell. It consists of a series of plates tightly connected to each other, with long needles sitting on them. Holothurians have calcareous bodies that are scattered over their skin. The skeleton of all these organisms is internal in origin.

Musculature and ambulacral system

The musculature of these animals is represented by muscular bands and individual muscles. It is developed quite well, as much as this or that animal is mobile. In most species of echinoderms, the ambulacral system is used for touch, movement, and in some sea urchins and sea lilies it is for breathing. These organisms are dioecious; they develop with larval metamorphosis.

Classification of echinoderms

There are 5 classes of echinoderms: brittle stars, sea stars, sea urchins, sea lilies and sea cucumbers. The type is divided into 2 subtypes: freely moving echinoderms are represented by brittle stars, holothurians, sea urchins and starfish, and attached by crinoids, as well as some extinct classes. About six thousand modern species are known, as well as twice as many extinct ones. All echinoderms are marine animals that live only in salt water.

Sea stars

The most famous representative of the type of interest to us is the starfish (a photo of one of them is presented above). These animals belong to the class Asteroidea. Sea stars are not accidentally given this name. In their form, many of them are a five-pointed star or a pentagon. However, there are also such species, the number of rays of which reaches fifty.

See what interesting body has a starfish, the photo of which is presented above! If you turn it over, you can see that on the underside of the rays there are rows of small tubular legs with a suction cup at the end. The animal, sorting through them, crawls along the seabed, and also climbs vertical surfaces.

All echinoderms have the ability to quickly regenerate. In a starfish, every ray that has separated from the body is viable. It immediately regenerates and a new organism emerges from it. Most starfish feed on leftovers organic matter. They find them in the ground. Their diet also includes fish carcasses and algae. However, some representatives of starfish are predators that attack their prey (non-motile invertebrates). After the prey is found, these animals dump their stomach out. Thus, digestion in some predatory starfish is carried out externally. The rays of these animals have very powerful muscles. It allows them to easily open the clam shells. Starfish, if necessary, can crush its shell.

The most famous among them is Acanthasterplanci - the crown of thorns. it worst enemy marine coral reefs. There are about 1500 species in this class (type echinoderms).

Sea stars are able to reproduce both sexually and asexually (regeneration). The bulk of these animals are dioecious organisms. They fertilize in water. The organism develops with metamorphosis. Some starfish live up to 30 years.

Serpenttails (brittle stars)

These animals are very reminiscent of stars: they have thin and long rays. The ophiuroids (type echinoderms) do not have liver appendages, anus and hindgut. In their way of life, they are also similar to starfish. These animals are dioecious, but are capable of both regeneration and asexual reproduction. Some species are luminous forms.

The body of the serpentine (ofiur) is represented by a flat disk, the diameter of which is up to 10 cm. 5 or 10 thin long segmented rays depart from it. Animals use these curving beams to move around, with which they crawl along the seabed. These organisms move in jerks. They stretch forward two pairs of their "arms", after which they sharply bend them back. Serpenttails feed on detritus or small animals. Ophiurs live on the bottom of the sea, sponges, corals, sea urchins. There are about 2 thousand of them. These animals have been known since the Ordovician.

sea lilies

Echinoderms are very diverse. Examples of crinoids that are also of this type are presented above. These organisms are exclusively benthic. They drive sedentary image life. It should be emphasized that crinoids are not plants, but animals, despite their name. The body of these organisms consists of a calyx, stem, and arms (brachioles). They use their hands to filter food particles from the water. Most modern species are free-floating and stemless.

Stemless lilies can crawl slowly. They can even swim in water. Their diet consists of small animals, plankton, algae residues. Total number species is estimated at 6 thousand, of which less than 700 are currently represented. These animals have been known since the Cambrian.

Beautifully colored species of crinoids live mainly in the seas and oceans of the subtropics. They are attached to various underwater objects. It is believed that this, however, in the Mesozoic and Paleozoic era their role in the waters of the seas and oceans was very great.

Sea cucumbers (holothurians)

These organisms are called differently: sea-pods or holothurians. They represent a class of invertebrates such as echinoderms. There are species that humans eat. Common name edible holothurians - "trepang". Trepang is mined on a large scale in Far East. There are also poisonous holothurians. Various drugs are obtained from them (for example, holothurin).

Currently, about 1150 species of sea cucumbers are represented. Their representatives are divided into 6 groups. The Silurian period is the time to which the oldest fossils of holothurians belong.

These organisms differ from other echinoderms in their oblong, spherical or worm-like shape, as well as the reduction of the skin skeleton and the fact that they do not have protruding spines. The mouth of these animals is surrounded by a corolla, consisting of tentacles. With the help of them, holothurians capture food. These animals are benthic, although very rare and living in the silt (pelagic). They drive sedentary image life. Holothurians feed on small plankton or silt.

sea urchins

These animals live at the bottom or in the bottom. The body of most of them is almost spherical, sometimes ovoid. Its diameter is from 2-3 to 30 cm. Outside, the body is covered with rows of spines, calcareous plates or needles. As a rule, the plates are interconnected motionlessly, forming a shell (dense shell). This shell does not allow the animal to change shape. Today, there are about 940 species of sea urchins. The largest number species were introduced in the Paleozoic. Currently, there are 6 classes, while 15 are extinct.

As for nutrition, some sea urchins use dead tissue (detritus) for food, while others scrape algae from stones. In the latter case, the animal's mouth is equipped with a special chewing apparatus called the Aristotelian lantern. In appearance, it resembles a drill. Some species of echinoderms (sea urchins) with its help not only get food, but also modify rocks by drilling holes in them.

The value of sea urchins

These animals - valuable species biological resources of the sea. Commercially interesting mainly In Japan and other countries of the Asia-Pacific region, it is a delicacy product. The caviar of these animals contains many biologically active substances. Scientists believe that the elements that are present in it can be used for cancer as a therapeutic and prophylactic agent. In addition, they normalize blood pressure, increase potency, remove radionuclides from the human body. It has been proven that eating caviar increases resistance to various infections, helps with gastrointestinal diseases, reduces the effects of radiation therapy, improves the functions of the genital and thyroid glands, and the cardiovascular system.

Considering the above, it is not surprising that the sea urchin is a marine echinoderm that is becoming a coveted dish. For example, the inhabitants of Japan every year eat about 500 tons of caviar of this animal, both in its natural form and as additives to dishes. Incidentally, using this food product associated with such a long life expectancy in this country, where people live an average of 89 years.

In this article, only the main echinoderms were presented. We hope you remember their names. Agree that these representatives marine fauna very beautiful and interesting.