The role of crustaceans in nature and their practical significance. Biology at the Lyceum Diversity and importance of crustaceans

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Our tasks

• Get to know the variety of crustaceans
• To study the role of crustaceans in nature and in human life

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fresh water

Daphnia, or "water flea"

1 - 3 mm, plankton, filter feeders (ensure self-purification of water bodies), food for many animals (an important link in the food chain)3

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• Cyclops
• 1 – 8 mm, planktonic organism, favorite food for fish fry, insect larvae and tadpoles4

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• shield
• 1.2 - 7.5 cm, predatory crustaceans, can feed on fish fry. Shield eggs, protected by a powerful shell, are able to survive during shallowing and even when the reservoir dries up. Eggs can be dispersed by the wind, allowing crustaceans to disperse.5

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• water donkey
• Lives at the bottom. 1.2 - 2 cm, favorite places - overgrown areas of lakes, rivers, reservoirs. They move slowly along the bottom, feeding on the remains of decaying plants and animals.6

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• lake amphipod
• Bottom animal. 1 - 2 cm long. Yellowish crustacean quickly swimming on its side. Fishermen often call him "mormysh".
• In winter, due to a lack of oxygen, it floats up under the ice, where it can be easily caught and used as bait for fish.

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Narrow-toed crayfish

• Widespread in stagnant waters.
• Leads a predominantly nocturnal lifestyle. Scavenger. Does not shun small fish, invertebrates, amphibians. It can feed on dead and fresh parts of plants.
• In a situation of danger, they will fiercely defend themselves with claws.
• Adults reach 20 - 25 cm in length, weigh about 200 g.8

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Broad-toed crayfish

• An extremely rare species. Listed in the Red Book of Belarus.
• Lover of very clean lakes, rivers, streams. Leads a predominantly nocturnal lifestyle. Scavenger. During the day it hides under rocks or in burrows. In search of food, it can go up to 250 m from its shelter.
• Life expectancy up to 25 years.

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American signal cancer

• Rare view. On the territory of Belarus, it is sometimes found in the Neman and its tributaries.
• A distinctive feature is a white spot on the claw (hence the name)
• Resistant to crayfish plague.
• It was brought to Europe in the late 1990s. It is believed that it came to the territory of Belarus from the reservoirs of Poland.
• Usually 6 - 9 cm in length, there are individuals up to 18 cm. Life expectancy is up to 20 years. They feed mainly on carrion.

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Significance for a person

• American wide-toed narrow-toed
• signal crayfish crayfish crayfish
• favorite food of many people in our country

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Seas

lobsters

• Body length up to 60 cm.
• Weight 3 - 4 kg, specimens up to 11 kg are known.
• They live in warm waters everywhere.
• Claws are missing.
• Excellent food for marine predators.
• They contact each other with their antennae and stay in small groups.

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Lobsters or lobsters

• Males are much larger than Females.
• Life expectancy for males is about 30 years, for females - about 55 years.
• The largest individual had a mass of 20 kg 150 g.
• The number is declining.
• Excellent food for large marine predators.

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• Crustaceans from a few cm to 3.5 m or more between the tips of the claws.
• Mostly marine animals, but there are also inhabitants of the land, and representatives of fresh water.
• Powerful armor. Head
• Crabs have a small and very short abdomen.
• They are sometimes called short-tailed crayfish.
• Pictured is a Tasmanian king crab: 38 cm wide, weight 6.8 kg.

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Shrimps

• Crustaceans from a few cm to 10 cm or more in length.
• Mostly marine animals, but there are also freshwater inhabitants.
• We are well aware of the Black Sea shrimp.
• Predominantly nocturnal. They feed on plant and animal remains.
• They themselves serve as food for many marine life.
• They have no means of protection. When attacked, they simply run away with jerks from a predator.

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• Accumulations of crustaceans from 0.5 cm to 10 cm in the seas.
• Favorite food of herring, cod, sea bass, baleen whales, blue whale, penguins, crabeater seals.

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Ground and soil environment

• Wet forest floor, cellars and basements, sometimes bathrooms, soil - woodlice can be found everywhere.
• They feed on the remains of plants, sometimes animals. An important role in soil formation, for example, in the desert.
• Soil-forming wood lice can harm cultivated plants. Sizes from a few millimeters to several centimeters.

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Ground environment

coconut crab

• One of the largest arthropods on the planet.
• They live up to 40 years, reach a width of up to 40 cm and a weight of up to 4 kg.
• They like to feast on newborn turtles, other crustaceans, coconut pulp and fruits.

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Significance for a person

• Marine crustaceans - food animals
• In the photo: king crab catch

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Lesson topic: "Crustaceans, their diversity, common features and significance"

The objectives of the lesson: to study the diversity of crustaceans, to get acquainted with the features of their structure, to highlight common features, to consolidate knowledge about the features of the external and internal structure of crustaceans, to determine the meaning of crustaceans in nature and human life, to form the ability to analyze, concretize, draw conclusions, generalize and systematize the material, develop the processes of memory, attention, imagination.

In the last lesson, we got acquainted with the structure of crayfish, which belongs to the class Crustaceans. This class includes more than 30 thousand species from 1 mm to 1 m. Among them, lower and higher crustaceans are distinguished. Today we will get acquainted with some units of this class. Crayfish

Classification of Crustacea Orders LEAF PEDAL CONEPODS ISALOPEDS DIFFERENT DECAPS lower higher Class Crustaceans TYPE ARthropod daphnia shield cyclops Sea Duck Sea acorn Woodlice Water donkey amphipods Crayfish Lobster Spiny lobster Crab Shrimp

Lower crustaceans Lower crustaceans are several orders of crustaceans whose representatives lack ventral legs. A) Detachment Leaf-legged - representatives of this detachment have legs flattened like a leaf. daphnia shield

B) Order Copepods - these are small crustaceans that row with their pectoral legs like oars. Cyclops are ordinary copepods of our reservoirs. They got their name for an unpaired simple eye located on the forehead. Cyclops serve as intermediate hosts for broad tapeworm and guinea worm. They use their antennae for locomotion. Cyclops can perform complex movements - "dead loops" like a fighter plane.

C) Order Barnacles - representatives of this order lead an attached lifestyle and live in multi-valve calcareous shells. Their head and abdomen are greatly reduced, and the thoracic region is better preserved from the whole body. Two-branched long legs turn into a filtering apparatus, with the help of which barnacles get their own food ... Sea ducks

sea ​​acorns

Higher crustaceans Representatives of higher crayfish have a constant number of head, thoracic and abdominal segments, the latter have abdominal legs. A) Detachment Equinopods Outwardly, their legs seem to be the same. In fresh waters there is a water donkey, which crawls along the bottom on thin legs. On the head of a donkey there are 8 simple eyes. water donkey

Woodlice are terrestrial isopods. Woodlice live in damp places - in cellars, basements, under stones and lagging bark. They lead a nocturnal lifestyle. All segments of the thorax and abdomen remain free and clearly visible. Woodlice breathe moist air with the help of modified gills. woodlouse

B) Order Diverse - these are crayfish that have different limbs for movement. They are often called amphipods, because. moving around lying on their side. amphipod

C) Detachment Decapods - in representatives of this detachment, the pectoral limbs turn into powerful walking legs, of which there are 5 pairs. With their help, they move along the bottom of reservoirs, and small abdominal ones are used for swimming and bearing offspring. They mainly live in the seas. There are about 9 thousand of them. This is the same detachment where the crayfish belongs.

Such different decapod crayfish Crayfish Crayfish (boiled) Mantis crab

Omar Langust

Hairy crab King crab Blue crab

Sections: Biology

Purpose: To acquaint students with the diversity of lower and higher crustaceans, habitat, consider their importance in aquatic biocenoses; continue to develop skills to justify your answer.

Equipment: Collections of crustaceans, tables depicting crayfish and a variety of crustaceans, drawings in the textbook.

I Checking knowledge and skills.

1. Characteristic signs of the type of arthropods, structural features, vital activity of crustaceans on the example of crayfish. (foyer of the zoological museum)
2. Historical development of arthropods. (foyer of the zoological museum)

II. Learning new material.

1. Diversity of crustaceans colonization of water bodies: seas and oceans.

A) lower crustaceans: cyclops, daphnia, brine shrimp, sea acorn, sea ducks.

Hall 1 Crumbs living in water (brine shrimp, daphnia, cyclops)

Hall 2 Sitting crustaceans (sea ducks),

sea ​​acorns)

Hall 3 Life and customs of woodlice

B) Higher crustaceans: river and sea crayfish, crabs, shrimps, lobsters, lobsters.

Hall 5 Hermit crab

The role of crustaceans in biogeocenoses

Hall 6 The chain of life in the sea.

III. Fixing:

1. Crossword
2. Test

IV. Homework pp. 148-149

During the classes

Foyer of the Zoological Museum of Crustaceans

Arthropods are crayfish, crabs, spiders, scorpions, centipedes, insects. There are a great many of them on earth. There are about 3 million species of arthropods alone.

The very name of the type of these animals shows that their legs are jointed. Each segment is connected to other segments, and to the body by a special movable joint. They walk and run, one might say, on numerous levers. The muscles that move the legs and other parts of the body are not attached outside the skeleton, but inside it, that is, inside the chitinous shell that covers the entire body of arthropods. Since the shell is located on top of the rest of the body of the animal, it is strong and, having formed, does not increase in size, therefore, arthropods can grow only during molting, when they shed the old shell, and the new one is still soft and stretchable. Therefore, their growth can be said to be spasmodic. Crayfish changes only once a year.

And here's another difference between arthropods - all their muscles are striated. And as you know, it has more powerful and faster contractions. The striated muscles of arthropods provide those high-speed movements that, for example, insect wings are capable of.

Arthropods have a fairly well-developed heart, but the circulatory system is open. Therefore, their blood is often called hemolymph, which gives a more accurate definition of the generated marine fluid that is distilled through their blood vessels and body cavities. In crustaceans, for example, in lobsters, a special pigment is dissolved in the blood - hemocyanin, something like hemoglobin, which carries oxygen to the cells. But hemoglobin is red in color, and hemocyanin is bluish in color, because it contains not iron, but copper. By the way. Some crustaceans also have hemoglobin.

Arthropods are an ancient group of organisms. Many classes of them already lived in the Cambrian. They originated in the Decembirian from some animals close to annelids. Trilobites were the first to form their typical appearance. In our time, arthropods have populated everything from the Arctic to Antarctica.

The fact that arthropods have passed from annelids is proved by the presence of many structural features common to these types of animal:

1. body segmentation
2. structures of the nervous system in the form of a ventral nerve cord
3. the similarity of the circulatory system with the main vessel lying on the dorsal side of the body.
4. The presence of modified mtanefridia in some arthropods.

Hall 1 “Crumbs living in water”.

There is a crustacean in the world - the entire length of its body is 1.5 cm, which can only live in salt water, where any other animal inevitably dies. The name of this amazing crustacean is Artemia salima.

Artemia salima lives in lakes, estuaries and bays in Europe, Asia, America, Africa, where the salt saturation of water is 23%. It withstands high salinity, and dies at lower salinity. It belongs to the branchial crustaceans.

And gastropods are the most primitive in the class of crustaceans. Their legs are partially turned into gills. But they have blades with which they row and drive food into their mouths.

The gastropods always swim with their backs down. But if you conduct an experiment and illuminate, for example, an aquarium in which Artemia salina is located, with a strong lamp from below, the crustaceans turn over and swim with their backs up.

Studying the Sivash Bay, the Soviet scientist V.P. Vorobyov calculated that in one cubic meter of water there are 13.6 g of brine shrimp, which means that there are 14.8 thousand tons of them in the entire bay. The bay of Kara-Bogaz-Gol was not yet separated from the sea (30%), had a reddish tint to the water, due to the mass of crustaceans that swarmed in the water. Now this bay has become more salty and the crustaceans in it have died.

Artemia feed on diatoms and green algae, which have adapted to live in “oversalted” water. With a lack of algae, they disturb the silt, and, swarming in it, fish out bacteria from it. Here are the Indians living on the shores of the Great Salt Lake in Utah, they ate both in winter and summer mainly brine shrimp.

Daphnia or water fleas are well known to all aquarium lovers. These tiny crustaceans are the predominant component of freshwater plankton and fill the ponds, dig in such a multitude that the water acquires a brownish tint.

The body of Daphnia is enclosed in a bivalve shell, from which only the head and second antennae, or, simply speaking, antennae, stick out. They are not simple, but branched, therefore they are referred to the suborder of branchy mustachioed crustaceans.

Daphnia legs are partially turned into gills. They also drive food into the mouth, but do not take part in the movement. Daphnia jumps in the water like a flea, sharply waving its branched antennae.

Daphnia feed, filtering out detritus, small animals and algae, which are not larger than 0.02 mm, by smoothly working pectoral legs. the most solid is daphnia magna half a centimeter long, all others are smaller. They eat daphnia and flagellates, but the main food is bacteria. One water flea eats from 5 to 40 million of all kinds of bacteria per day. Daphnia are hermaphrodites, although they can reproduce sexually if necessary. But this happens only when there is a big death. In this case, males hatch from eggs. They are dwarfs compared to females, but nevertheless they fertilize females very actively. After that, the eggs are covered with a thick cuticle, for example, it is easier for such eggs to overwinter. Or the wind carries them with dust, settling them in the nearest water bodies.

They got their name in honor of the mythical one-eyed giant with whom the cunning Odysseus dealt, for the reason that these crustaceans also have only one eye on their foreheads. Unlike brine shrimp and daphnia, they have no gills on their legs or anywhere else. They breathe through the entire surface of the body. There is no heart, no circulatory system: "The abdominal fluid is set in motion by the contractions of the intestines."

When swimming, the cyclops “rows” with four pairs of pectoral legs. It will make, by waving them, a jerk forward or upward, and then soars in the water on its spread mustaches, like an eagle on outstretched wings. He can swim on his back, and do “Dead Loops”, and dive with his head.

In general, the inexhaustible cascade of maneuvers performed by the cyclops is very similar to aerobatics.

Cyclops are predators and, moreover, very dangerous for small animals: they cope with worms and mosquito larvae, moreover, larger than themselves. They do not shy away from cannibalism.

Cyclops also show a kind of concern for offspring. The female carries fertilized eggs on the sides of the tail, and the eggs are glued together in two lumps until the larvae hatch from them.

Hall 2 - Crustaceans, seated.

There are crayfish that, like a sponge, cannot budge. Only their larvae swim. And as soon as the larva sits on the bottom, clings to it with its antennae, turns into an adult cancer, and sits all its life on a stone, rock, on a mollusk shell, on a crab shell, it happens on the skin of whales, and sharks, and even on the teeth of a sperm whale, in general, at the place to which the larva is attached. He sits and moves his mustache.

And the mustache of cancer is a magnificent fan. He then scatters it, then folds it in a bunch, driving water into his mouth, and with it any plankton (but not larger than 1 mm)

These animals, therefore, are called barnacles. They live in shells with lids made of calcareous plates. Those of them, in which the shells are attached to some object directly with their wide bases, are called sea acorns. And if a lime house sits on a stalk with its other end stuck to the substrate, then these will be sea ducks.

Sea acorns usually settle close to each other, so that they form dense fouling of stones and rocks in the tidal zone and even above the water level, in this case being content with the meager food that the surf brings to them.

Sea acorns cause great damage to the surfaces of ship hulls. Up to 45 thousand larvae sometimes settle on 1m 2 of the bottom of the ship. If we take into account that during the day they increase their height by 1 mm, then it is easy to understand that due to sea acorns, good streamlining is lost, which reduces its normal speed by a third. We have to bring the ships to the docks and clean them from fouling.

Whales, in particular the gray whale, usually carry thousands of passengers. Marine crustaceans - sea ducks no larger than a coin - need a solid base to which they can attach. The huge surface of the whale's body is just as good for them as the rock or the bottom of the ship. Sea ducks feed on tiny organisms, sucking and straining them out of the water. The patterns of these shells on the whale's back help whalers recognize individual individuals.

Hall 3 - the life and customs of wood lice.

Woodlice are the only isopods that have mastered the living space of land of all latitudes and climates.

True, there are some primitive woodlice that have not yet completely parted with the habits of their ancestors, have not gone far from the sea - they live on its shores. They even know how to swim, they even conducted experiments where they were kept under water for 80 days and they did not die. All other wood lice would have “choked” long ago if they were subjected to such an experiment.

Land woodlice try to keep all the same in wet places. During the day, they hide from the sun under stones, buried in the ground, or in burrows dug by themselves or strangers, looking for shelter even in anthills. At night, they crawl out of their shelters and gnaw on plants, replenishing their thirsty body with moisture.

Desert woodlice among arthropods. Perhaps one of the most numerous inhabitants of the loess deserts and, apparently, are of no small importance in the life of the desert. These wood lice are constantly looking for new places suitable for existence. They crawl slowly, covering about two meters in a minute. This is when it is relatively warm +10 +15 0 s in the shade.

Desert woodlice do not live alone, but always in colonies, in which sometimes there are several million families. Caring for alien offspring belonging to one's own species is one of the most interesting features of the biology of woodlice. It has no analogy among other crustaceans.

River and sea crayfish, crabs and shrimps are representatives of the order of decapod crayfish, or decanods. The order is extensive: it contains 8500 species. It got its name for the reason that the animals representing it walk on ten pectoral legs, and the first pair of them in many is transformed by nature into powerful claws. Decapods also have gills on the bases of the thoracic legs, and their females attach eggs to the abdominal legs, and only a few shrimp do not carry eggs on themselves, but sweep it directly into the water. The head and chest are covered with a monolithic cephalothoracic shield - a carapace. In crayfish, it looks like a warrior's cuirass and immediately catches the eye. Behind him stretches the abdomen, already dressed with separate plates, which ends with a “tail” (telson).

Huge crayfish live off the coast of Africa, America and Europe, these are lobsters and spiny lobsters.

The European lobster is up to 50 cm long and weighs 11 kg. American lobster - up to 60 cm long, weighing up to 15 kg. On the front pair of walking legs of the lobster are powerful claws. One of them is stronger - crushing, the other - cutting. Lobsters don't have claws. Within Russia, the European lobster is found in the Black Sea on rocky and pebbly soils at a depth of 30-80 m. During the day, the lobster hides among the stones, and at night it hunts for mollusks, worms, and shrimps. It grows slowly, reaching sexual maturity only in the sixth year. The female lays about 32 thousand eggs on the abdominal legs, from which floating larvae emerge after a year.

Lobsters are smaller in size than lobsters (but there were cases when they met lobsters up to 75 cm long.) These crayfish live at shallow depths along the coasts of Europe and Africa in the Mediterranean Sea, AS WELL AS IN the Pacific, Indian and Atlantic oceans. Spiny lobsters have long antennae, and their chest is covered with numerous shields. Unlike lobsters, lobsters do not have claws on their front legs. Interestingly, with the help of waving antennae - antennas that rub their base against the front edge of the shell, lobsters make a loud sound.

Lobsters and lobsters are considered a food delicacy and are caught in large numbers. Only off the coast of Europe and America, about 1000 tons of these crayfish are mined annually, and off the coast of Cuba - about 8000 tons.

Shrimps belong to the swimming suborder (natancia), while lobsters and lobsters are crawling suborder (rentancia). Slope shrimp will settle in sponges, because. they hide in them.

Some shrimp often find safe shelter under jellyfish colonies, between the tentacles of sea anemones, in the cups of sea lilies, and also in sponges.

For the most part, shrimp are free-floating inhabitants of marine, brackish and fresh waters.

Some of them are hermaphrodites (an exception among decapods). In youth, when it turns from larvae into adults, they are males. After living for two years, they are reborn as females. Shrimps are even able to change their color to match the color of the bottom.

Kamchatka crab, its life is peculiar. It inhabits the Japanese, Okhotsk, Bering seas. The carapace of the male of this species is on average 16 cm wide, and in the Gulf of Alaska - 28 cm.

The distance between the ends of the average walking legs of such large individuals is 1.5 m, and the total body weight is up to 7 kg. The Kamchatka crab, although decapodous, has only four pairs of legs “in use”. He hides one pair of legs under the shell and cleans the gills with them. First pair of legs with claws. The right claw is large and strong. With it, the crab opens the shells of mussels, breaks the shells of sea urchins. With his left claw, he crushes food and sends it to his mouth.

King crabs are real travelers, and every year they repeat the same route. Crabs hibernate at depths up to 250 meters. In spring they return to the coast to molt and breed. In the fall they go deeper again. The female lays 20,000 to 300,000 eggs and carries them, like a cancer female, on her abdominal legs for 11.5 months.

In the crabs fishery, males are harvested (it is forbidden to harvest females) up to 13 cm long or more. The right claw with its segments is the most valuable product of the crab industry. Crabs are processed on floating plants. Shells and entrails are processed into excellent fertilizer.

Hall 5 Cancer is a hermit.

More than two thousand years ago, the father of zoology, the great Aristotle, drew attention to strange crayfish.

The partners of hermit crabs are anemones, or sea anemones, which live in the sea everywhere, for example in coral reefs where animals live together or on other animals. So it is easier for them to get food or find protection.

The hermit crab does not have its own shell, so it lives inside old sea shells. On coral reefs, sea anemones share a home with hermit crabs. Anemones with their burning tentacles protect themselves and hermit crabs. And those, in turn, supply a lot of food residues that eat up anemones.

A higher stage in the development of symbiosis is represented by the “friendship” of Prideaux crayfish and adamsia sea anemones.

Adamsia, if separated from cancer, dies in 2-3 months, and Prido's cancer dies even faster: for the first time, he becomes a victim of the greed of predatory fish and octopus. Cancer, after all, is not protected now by the stinging batteries of sea anemones.

Few people have ever seen Prideaux's crab without sea anemones. The anemone itself also lives without cancer only at a young age. Sitting on a stone is a kind of pink bud the size of a thimble. No one has ever met large adamsias in the sea, except on the shells of Prideaux. Therefore, it is unknown to zoologists whether these anemones reach full maturity without the help of cancer, leading a free lifestyle.

Cancer feels the anemone with its antennae, and if it is wrapped in a rag, it will not be mistaken either: it will distinguish its action from someone else's. He probably smells it. He carefully takes her claws at the very bottom, at the sole, so as not to damage her, and puts her on the sink. Actinia does not sting cancer. Although experiments have shown that hermit crabs are not susceptible to sea anemone poison. A substance is formed in their blood that neutralizes this poison.

Hall 6 The chain of life in the sea.

Life in the sea begins with phytoplankton - the smallest algae. It is they who create the primary products - biomass, on the basis of which almost all other inhabitants of the sea exist.

Not visible to simple gas, a small green cell, hovering near the surface of the sea, is the first to capture the energy of the sun, and during photosynthesis converts it into nutritious organic substances. During one year, about 500 million tons of organic matter are formed in the World Ocean. The food chain starts with phytoplankton.

Its next link is zooplankton - these are microscopic animals that live in the sea water and feed on algae. Mostly they are crustaceans. Zooplankton are eaten by small fish forming another link. In turn, they can become prey for larger fish. Birds or animals can become the next link. Interestingly, the total mass of living beings in each subsequent link is about 10 times less than in the previous one.

At the end of our tour, we can conclude:

That the world of crustaceans is diverse and beautiful, which in turn are the second link in the food chain in rivers, lakes, seas and oceans.

V. Consolidation.

1. Test.
2. Make a food chain including representatives of crustaceans.
3. Compose a crossword.

VI. Homework pp. 148-149.

About 30,000 species of crustaceans are known. Among them there are small crustaceans 2-5 mm long. These are daphnia and cyclops. They float in the water.

Figure: variety of crustaceans

Organisms floating in water, such as daphnia and cyclops, are called plankton. Daphnia and cyclops live both in fresh waters and in the seas. They make up a significant part of the plankton and serve as food for various fish. In pond fish farms, they are specially bred for feeding fry.

Decapod crayfish, which also includes river crayfish, got their name from the number of walking pectoral legs. This also includes shrimp, crabs, lobsters and lobsters that live in the seas. These are valuable commercial crustaceans, which are mined for meat. There are about 10,000 known species. Many crustaceans serve as a favorite food for fish and toothless whales.

General characteristics of crustaceans

Crustaceans are gill-breathing aquatic arthropods that differ from other arthropods in having two pairs of antennae and biramous limbs. Most crustaceans have a cephalothorax and an abdomen. Respiratory organs - gills, which are outgrowths of the limbs.

2014-05-29

Most crustaceans are aquatic organisms. They live in the seas, oceans, lakes, rivers, puddles and damp places. Some representatives of this group of animals lead a sedentary lifestyle. For example, sea acorns and sea ducks attach themselves to the bottom of ships or objects floating on the surface and move along with them. From the polar regions to tropical forests, you can find terrestrial crustaceans - wood lice, palm thief crab.

Daphnia are able to soar in the water column and perform sharp jumps, hence their second name - water fleas. The body of these crustaceans is enclosed in a bivalve shell, from which the head and branched antennae protrude. In daphnia, droplets of fat accumulate in the body, which are visible through transparent covers. Daphnia feed by filtering various algae, protozoa and bacteria from the water. So, one daphnia magna per day is able to eat up to 40 million unicellular organisms.

The representative of higher crayfish is crayfish. Found in rivers and streams. At the bottom of the river and in the cliffs, the cancer pulls out a mink more than 25 cm deep. In the mink, it sits out in the heat, and in winter it escapes from the cold, closing the entrance with silt. Crayfish are nocturnal. In the spring, the female lays eggs, which are attached to the abdominal legs and carry with her everywhere. At the beginning of summer, young ones appear from them. For several days they remain sitting under the mother's belly. The first summer they grow rapidly and molt 10 times, the second summer - 5 times. Crayfish live for almost 20 years.
Barnacles on all fours, sea acorns and sea ducks lead an immobile lifestyle in adulthood. The front end of their body turns into an attachment organ - a flat wide sole or a fleshy stalk. Externally, the body is protected by a shell, consisting of plates of calcium carbonate. Attaching to the bottoms of ships, barnacles significantly slow down the progress of ships and increase fuel consumption. Ships have to be docked to clean the bottoms.
Rais are hermits. The abdomen of the hermit crab does not have a hard cover. For protection, they usually settle in empty gastropod shells or bamboo stalks. Hermit crab can live in symbiosis with sea anemones and other coral polyps.
The palm thief crab easily climbs palm trees 20 m high, cuts coconuts with claws and opens them on the ground.