11. Type of clams

12. Clam classes

1. Having studied the text of the paragraph, formulate general characteristics such as Mollusks.

The body is soft, muscular, consists of 3 sections: trunk, leg, head (except for bivalves). No segmentation. The body is covered with a shell. On the head there are tentacles, eyes, a mouth opening and balance organs.

2. Show on concrete examples that the structure of the respiratory organs of mollusks is determined by their habitat.

Terrestrial mollusks (snail) breathe lightly, aquatic mollusks (oysters) - gills.

3. What do you think, for what purpose are mollusk shells crushed and added to poultry feed?

as an additional source of calcium

4. Select from the terms listed those that indicate body partscertain clams.

1. Tentacles
B 2. Leg
B 3. Gills
4. Sink
5. Respiratory opening
6. Head
7. The mantle
8. The torso
9. Eyes
10 Shell flaps
11. Introductory siphon
12. Oral lobes
13. Outlet siphon
14. Tentacle Stalkers
15. Tail fins

A - squid
B - pond
B - Toothless

Answer:

A - 1, 3, 6, 7, 8, 9, 14, 15
B - 1, 2, 4, 5, 6, 7, 8, 9, 12
B - 2, 3, 7, 8, 10, 11, 12, 13

5. Having studied the text of the paragraph, fill out the table.

6. Using figure 31 of the textbook, describe how the blood circulation in mollusks is carried out.

The circulatory system is open and consists of the heart and blood vessels. The heart has a ventricle and 1 -2 (less often 4) atria. In addition to the vessels, part of the way the blood passes in the slit-like cavities between organs.

7. Having studied the text of the paragraph, fill out the table Meaning of mollusks.

8. Complete the sentences.

Shellless body slugs thick mantle . It protects the body from excessive evaporation and drying out. This mollusks are predominantly ground lifestyle and hide under sticks, boards, etc.

9. Having studied the text of the paragraph and the drawings, perform laboratory work No. 4, “Features of the structure and life of mollusks,” sketch the shells of gastropods and bivalves, and sign their names.

10. Consider pictures 32, 33.34 of the textbook (p. 49, 51). Which of the painted mollusks have you seen? Write down their names.

fig. 32: Bradyben Weirich, blue slug
fig. 33: Lima rough, trident giant
Figure 34: octopus, cuttlefish

11. Having studied all the material of the textbook on the type of Shellfish, fill out the table.

12. Give definitions of concepts.

Jet propulsion- pulsating discharge of water from the mantle cavity through the funnel
Ink bag- the mollusk organ (e.g. cuttlefish) in which ink is produced
Digestive gland- body included in digestive the system mollusks
Salivary gland- iron of the first section of the digestive tract in mollusks
Mantle cavity- the cavity that is located between the mantle and the body of the mollusk
Grater - muscular tongue with chitinous teeth in the oral cavity of mollusks

13. Based on the text of the paragraph, prove that mollusks are at a higher stage of evolutionary development than worms.

Shellfish are more highly organized in structure (there are blood, digestive and nervous system organs) and behavior

14. Fill in the Scheme Systematic groups of the type Mollusks.

Type Shellfish
- class gastropods
- class bivalve
- cephalopods class

15. Carefully examine the drawing and designate the internal organs of the mollusks.

1. Nerve nodes
2. Nerves
2, easy
3. Heart
4. Blood vessels
5. Intestine
6. Stomach
7. Grater
5. Intestine

What new organs appeared in mollusks compared to worms?gut, stomach, heart, lung

16. Crossword number 2 "Mollusks"

1. Excretory organs in mollusks ( the kidneys )
2. The body that provides the movement of blood through the vessels and body cavity ( a heart )
3. A clam capable of flying over water in the event of a pursuit ( squid )
4. The outer fold of skin in mollusks ( mantle )
5. gastropod mollusk. shellless ( slug )
6. Part of the body of the gastropod (leg )
7. A mammal using gastropods as a food ( mole )
8. Sack-like respiratory organ in terrestrial mollusks ( lung )

CLASS Molluscs Dentist (Gastropoda)

In gastropods, the body consists of a head, trunk, and leg. The leg is the muscular abdominal part of the body, resting on which the mollusk slowly glides.

Most gastropods have a spiral twisted shell (therefore they are also called snails), in which the animal can completely hide. In the lower part of the shell there is a wide opening - the mouth, through which the mollusk protrudes its head and leg during movement. Some terrestrial gastropod mollusks - slugs - have no shells.

In the throat of gastropods there is a muscular tongue covered with spines - the so-called grater. Using it, the mollusk scrapes the tissue of plants or scrapes the plaque formed on underwater objects from various microorganisms.

Family Definition Table

1(4) The mouth of the conch, when the mollusk draws its head and leg in, is closed by a thin lid attached to the leg.
2(3) On the curls of the shell there are dark longitudinal stripes (they may be poorly visible due to plaque covering the shell), up to 45 mm;
3(2) Sink without dark stripes, one-color; value not more than 12 mm;
4(1) There is no lid at the mouth of the conch, so that the mollusk hidden in it shows a compressed sole of the foot.
5(6) The turns of the shell are twisted in one plane;
6(5) The shell is twisted conically.
7(8) The shell is twisted to the right (if you take the shell so that the top is directed away from you and the mouth towards you, then the mouth will be located to the right of the center line);
8(7) The shell is twisted to the left (the mouth is to the left of the center line); FAMILY (Lymnaeidae)

In the pond, the shell is twisted spirally, in several revolutions, in the form of a turret. In the USSR there are about 20 species.

Common pond (Lymnaea stagnalis) The largest of our ponds, the height of the shell is 45-55 mm, and in some individuals even up to 65 mm. It lives in stagnant water bodies - ponds, lakes, backwaters of rivers with abundant vegetation. Here you can see how the pond, sticking out his leg and head with tentacles from the sink, slowly glides over the plants. Having reached the surface of the water, the pond spreads its leg wider and slides, hanging from below to the surface film of water. At the same time, at the mouth of the shell, on the side of the leg, a round breathing hole can be seen. In mid-summer, the pond grows to the surface of the water 6-9 times per hour. Distributed in Europe and North Asia to Kamchatka.

Ear pond (Lymnaea auricularia) This mollusk has a shell with a very wide mouth, the height of the shell is 25–40 mm, and the width is 20–30 mm. It lives in the surf zone of stagnant water bodies. Distributed in Europe and Asia (except for the southeast).

COIL FAMILY (Plarmrbidae)

The coils of the shell coils are located in the same plane. Coils are not as mobile as ponds, and cannot be suspended from a surface film of water. In the USSR there are 35 types of coils.

Horn coil (Planorbarius corneus) This mollusk has a shell diameter of up to 35 mm. It lives on plants in stagnant bodies of water, in the same place where ordinary pondbut rarely rises to the surface of the water. Distributed in Europe and Western Siberia to the Ob.

Edged coil (Ptanorbis planorbis) At the fringed coil, the shell is dark brown, with a diameter of 20 mm, with 5-6 revolutions. On the last turn below there is a sharp ledge - keel. It lives in shallow reservoirs and in the coastal part of large reservoirs. Distributed in Europe and Western Siberia to the Yenisei.

Spool (Anisus vortex) The shell is yellow, with a diameter of up to 10 mm, with 6-7 revolutions. At the last turn, a sharp, shifted downward keel. It lives in coastal thickets of standing reservoirs, often floats on the surface of the water. Distributed in Europe and Western Siberia to the Yenisei.

FISIDA FAMILY (Physidae)

The fizid has a turret-shaped shell, like that of a pond, but is twisted to the left.

Phiza bubbly (Physa fontinalis) The shell is dull, pale yellow, 10-12 mm high, 5-6 mm wide, the height of the mouth is more than half the height of the shell. It lives on vegetation in various ponds. Distributed in Europe and North Asia.

Aplexa sleepy (Aptexa hypnorum) The shell is shiny, golden brown, 10-15 mm high, 5-6 mm wide (mouth height less than half the height of the shell). It lives only in temporary, drying up reservoirs in the summer. Distributed in Europe, Western Siberia and the south of the Far East.

FAMILY PILLS (Viviparidae)

The mouth of the conch alone is closed by a lid. Sinks with dark longitudinal stripes. Luzhanka is also called viviparous, as they do not lay eggs, like other mollusks, but give birth to small, already having a shell meadows.

Marsh meadow (Viviparus contectus) Sink up to 43 mm high. It lives in lakes, ponds, sometimes even in puddles with clean water. Holds on the bottom. Distributed in Europe and Western Siberia to the Ob.

FAMILY BITINI (Bithyniidae)

As in the puddles, the shell mouth is closed by a lid at rest, but the shells are monochromatic, without stripes.

Bitinia tentacle (Bithynia tentaculata) Sink up to 12 mm high. It lives in standing and weakly flowing reservoirs, on stones, in silt and among plants. Distributed in Europe and Western Siberia.

Terrestrial gastropods

Terrestrial gastropods can be divided into two groups: snails with a shell, and slugs that have no shell (in some species, a small remainder of the shell is hidden under the skin and is not visible from the outside). Since the skin of the mollusks is bare, many species adhere to humid habitats. In addition, animals are usually motionless during the day. In this case, the snails completely hide in the sink, sucking the sole of the foot to the substrate, and the slugs crawl under shelters - stones, leaves, between lumps of soil. But at night, and in rainy times and during the day, mollusks crawl from place to place.

Snails

In land snails, the shell is spirally twisted. In some species, the shell is elongated, so that its height significantly exceeds the width, in other species, on the contrary, the shell is low and its width is greater than the height. During the movement, the mollusk protrudes its head and leg from the shell. On the head are visible 4 forward tentacles. At the ends of two longer tentacles there are dark balls - these are eyes. If you carefully touch the tentacles, the mollusk immediately draws them in, and if you disturb it strongly, it will completely hide in the sink. In the USSR, several hundred species of snails are found. Basically, these are very small, difficult to distinguish from each other species (often only by internal structure) We will consider only some of the largest and most widespread forms.

Amber (Succinea putris) It got its name for the amber-yellow color of an elongated, thin, fragile, almost transparent shell. The height of the sink is 16-22 mm, the width is 8-11 mm. Sink with 3-4 revolutions, the last revolution is strongly swollen and enlarged, the mouth is ovoid. Amber lives in moist places - in moist meadows, near water bodies, it can often be seen on floating leaves of aquatic plants, and sometimes it even plunges into water. Widely distributed in the USSR.

Kohlikopa slippery (Cochticopa lubrica) This is a small snail, with a smooth shiny, elongated, conical shell, 6-7 mm high, 3 mm wide. It is very common in moist places - in meadows, in grass, in moss, in fallen leaves of moist forests. Distributed throughout the USSR.

Ifigen's bloated (Iphigena ventricosa) At this snail the shell is elongated, fusiform, ribbed, reddish-horny, 17-18 mm high, 4-4.5 mm wide, with 11-12 revolutions. A flat toothlike protrusion extends from the mouth above. It lives in forests, on litter, on mossy tree trunks. Distributed in the Baltic states and the middle zone of the European part of the USSR.

Rocky cohlodine (Cochlodina laminata) In this species, the shell is elongated, fusiform, slightly swollen, smooth, shiny, light-horny, 15-17 mm high, 4 mm wide, with 10-12 revolutions. At the mouth, two lamellar curved protrusions are visible. It lives in forests, on rocks, stumps, tree trunks. Distributed in the middle lane of the European part of the USSR, north to the Leningrad region, east to Kazan.

Shrub snail (Bradybaena fruticum) This snail has a spherical shell, almost smooth, 16-17 mm high, 18-20 mm wide, with 5-6 revolutions. Coloring can be various, from grayish-white to reddish-horn, often on the last turn of the shell a narrow brown stripe is visible. It lives in shrubs, deciduous forests, gardens, often a shrubby snail can be found on nettles and coltsfoot. Sometimes it climbs quite high on bushes, tree trunks and fences. Distributed in the European part of the USSR, in the Crimea and in the North Caucasus.

Garden snail (Cepaea hortensis) At the garden snail, the shell is cubar-shaped, similar to the shell of a shrubby snail, 15-16 mm high, 19-21 mm wide, with 4-5 turns, dark spiral stripes are visible at all turns. It lives in sparse shrubs and forests, on stones, rocks. Distributed in the Baltics

Shaggy snail (Trichia hispida) In this small snail, the conch is covered with thin hairs (in older individuals, they may be worn away). Sink 5 mm high, 8–9 mm wide, grayish or reddish-brown in color, usually with a light stripe at the last revolution. It lives in shrubs, on the ground in forest litter, under stones, and fallen trees. Distributed in the forest zone of the European part of the USSR, up to the Leningrad and Perm regions. Often causes harm to native, fruit and berry crops and ornamental plants, scraping leaf tissue so that only longitudinal thick veins remain from them.

SLIMA

In slugs, the body is naked, devoid of a shell. In a calm state, the slugs look like small mucous lumps, but when they move, their body is greatly stretched. Like snails, 4 tentacles directed forward are visible on the head. At the ends of two longer tentacles there are eyes. Behind the head, a short neck is visible, passing into the back. Immediately behind the neck, an oval thickening is visible on the back, as if another layer of skin were superimposed on top. This is the so-called mantle covering the respiratory organ - the lung. A rounded breathing hole is visible on the right side of the mantle. As the name shows, slugs produce a lot of mucus. It primarily protects the mollusks from drying out. In addition, mucus helps them slip. Creeping slug always leaves a noticeable shiny mucous mark. In the middle zone of the European part of the USSR 16 species of slugs live. Of these, we will consider the most common, widespread forms.

Definitive birth chart

1(2) The breathing hole is located in front of the right edge of the mantle. When moving, the end of the leg protrudes slightly from under the back;
2(1) The breathing hole is located at the back of the right edge of the mantle. The leg from under the back does not protrude when moving.
3(4) Large slugs, over 100 mm long.
4(3) The size of the slugs does not exceed 50 mm.
5(6) Yellow mucus;
6(5) The mucus is colorless, with irritation of the mollusk - milky white; GENUS OF ARION (Arion)

The body is thick, massive. The mantle is oval, rounded in front and behind. A breathing hole in front of the right edge of the mantle. When moving, the end of the leg protrudes slightly from under the back.

Arion Brown (Arion subfuscus) Body length up to 80 mm. The mantle is about 1/3 of the body length. Coloring can be different, from brown to orange, often rusty. The middle of the back is usually darker. It lives in deciduous, mixed and coniferous forests, occasionally found in old parks and cemeteries. Favorite food - hat mushrooms, in which the slug eats large cavities. It can also feed on dead parts of plants and animal corpses. Distributed in the forest and forest-steppe zone of the European part of the USSR. In the Altai Territory, Eastern Siberia, the Amur basin and Primorsky Territory, the subspecies Arion brown Siberian (Arion subfuscus sib ire us) lives, which is distinguished by a one-color-black body color. In warm, damp summers, this slug causes damage to gardens and fields located next to the forest.

Arion striped (Arion fasciatus) Body length up to 50 mm. The mantle occupies about 1/3 of the body length. The color is light - cream or yellowish-ash, the middle of the back and mantle is slightly darker. On the sides are clearly delimited dark stripes. It occurs more often in cultural biotopes - gardens, fields, gardens, parks. Often causes significant damage to crops. Distributed in the northwestern and central regions of the European part of the USSR.

GENUS OF DEROCERASES (Deroceras)

Small slugs, rather slender and mobile. The skin is almost smooth, with weak grooves, without rough wrinkles. A breathing hole in the back of the right edge of the mantle. The mucus is colorless, with milky irritation milky white.

Mesh slug (Deroceras reticulatum) Body length 25-35 mm. The mantle occupies about half the length of the body. The color is mostly cream or light coffee, with dark spots forming a grid pattern, especially visible on the mantle and back. Head and neck are also covered with small spots; tentacles are blackish. It lives in open places, avoiding forests and shrubs, often on clay soils - meadows, fields, gardens, landfills, and in cities - in parks and gardens. Of all slugs, the most dangerous crop pest. In the gardens, he eagerly attacks cabbage, eating large holes not only in the outer leaves, but also inside the head of cabbage. In rainy years, it damages the seedlings of winter crops. Widely distributed in the European part of the USSR.

Field Slime (Deroceras agreste) Body length 35-40 mm. The mantle occupies about 1/3 of the body length. Coloring from almost white to cream, without a dark pattern. It lives in open places - meadows, swamps, near roadside ditches, on forest edges, but, unlike mesh slug, avoids places with cultivated soil. Widely distributed throughout the USSR.

Smooth slug (Deroceras laeve) Body length up to 25 mm. The mantle occupies about half the length of the body. Coloring from reddish-brown to almost black, one-color. Very hygrophilous and cold-resistant. It lives in swamps, wet meadows, in damp forests, on the banks of small overgrown ponds - here it can be not only on soil and plants, but also on their underwater parts. Widely distributed throughout the USSR.

GENUS OF LIMACS (Limax)

Large slugs, more than 100 mm long. The color is spotty, sometimes the spots merge into dark stripes. The keel protrudes on the tail of the back. The body is wrinkled, wrinkles are long, convex, with deep grooves between them.

Black slug (Limax cinereoniger) Body length 150-200 mm. The mantle occupies about 1/4 of the body length. Coloring is black or dark gray, keel is light. Tentacles with black dots. It lives in deciduous and mixed forests, and can live in coniferous forests with good grass cover. It feeds mainly on mushrooms and lichens. Distributed in the Karelian Autonomous Soviet Socialist Republic, the Baltic States, Belarus, in the western and central regions of the RSFSR, east to Nizhny Novgorod.

Big slug (Limax maximus) Body length up to 130 mm. The mantle occupies about 1/3 of the body length. Coloring mottled: on a yellowish, ash-gray or off-white background, 2-3 pairs of dark stripes or rows of dark spots. The tentacles are one-color, without dark dots. It lives in cities - in parks, gardens, greenhouses, vegetable stores, where it can be harmful. Distributed in the northwestern and central regions of the European part of the USSR.

GENUS OF MALACOLIMAX (Malacotimax)

Malacolimax tender (Matacolimax tenellus) Body length up to 50 mm. The mantle occupies about 1/3 of the body length. The color is one-color, often yellow, greenish or grayish-yellow, sometimes orange-yellow. The head and tentacles are black or dark brown. The mucus is yellow. It lives in deciduous forests, occasionally in conifers. It feeds on cap mushrooms and lichens. Distributed in the northwestern, western and central regions of the European part of the USSR.

CLASS Mollusk bivalves (Bivalvia)

In bivalve mollusks, the shell consists of two halves connected on the dorsal side by an elastic ligament. On the ventral side, the shell halves can be slightly moved apart, and the clam leg protrudes through the gap formed. When moving, the mollusk spreads with its foot, like a plow, silt or sand at the bottom, hooks its foot on the ground and pulls the body with the sink forward, again extends the leg forward, again pulls itself up and thus crawls along the bottom with small steps. Some bivalve mollusks do not move, but sit in one place, attaching to the substrate with special adhesive threads. Bivalves have no heads, so there is no grater. They feed on small planktonic organisms, which are sucked together with water through a siphon hole located at the rear end of the body. All bivalves live in the water.

Dreissen River (Dreissena polymorpha) The shell of the river dreissen is greenish-yellow, with brown stripes, 30-50 mm long. The lower edge adjacent to the attachment site is flat, two lateral convex. It lives in rivers, lakes and reservoirs.

BARBAR FAMILY (Unionidae)

At the perovlitsa, the shell is elongated-oval. On each leaf the most convex, outstanding part is visible - the top. Concentrating around the apex, arcuate lines pass on each leaf. Some of these arcs are sharper, darker are annual arcs, they can approximately determine the age of the mollusk. There are 4 genera in the family. The most famous are barley and toothless.

CROWN BIRTH (Unio) The shell has a thick-walled shell, the tops of the flaps protrude upward. If you look at the sink from the end, then the place of fastening of the wings - the ligament - will be in the recess.

Barley ordinary (Unio pktorum) In ordinary pearl barley, the shell is long, narrow, up to 145 mm, with almost parallel dorsal and abdominal edges. Coloring in young individuals is yellow-green, in old ones it is greenish-brown. It lives in lakes and rivers, in places with a slowed flow, on sandy, not very silted ground. Distributed in the European part of the USSR, except for the north and northeast.

Swollen Barrier (Unio tumidus) In this species, the shell is shorter, up to 110 mm, with non-parallel edges. The habitats and distribution are the same as that of common barley.

KIND OF TOOTHLESS (Anadonta) The toothless have a thin-walled shell, the tops of the valves do not protrude much. If you look at the sink from the end, then the place for fastening the wings is not deepened. Some species have a large keel on the upper edge of the leaf. The shape of the shell is very variable in individuals of the same species living in different bodies of water.

GENUS OF A PEA (Pisidium) At peas, the apex of the shell folds is shifted to the side, the shell is short-oval. The size of the peas does not exceed 11 mm.

Pea (Pisidium amnicum) The diameter of the shell of a river pea is 10-11 mm. It lives in the backwaters of rivers and lakes, on silty-sandy soil. Distributed in the European part of the USSR and in Siberia to the Lena.

Prudoviki

The pond (Limnaea) belongs to the mollusks (Mollusca), to the class of gastropods (Gastropoda), to the detachment of pulmonary mollusks (Pulmonata), to the family of the pond (Limnaeidae).

The largest of our ponds is the ordinary pond, Limnaea staghalis L. (shell height up to 55 mm, width up to 27 mm) with a very elongated conical shell.

The auricle of the pond L. auricularia L. (shell height 26 mm, width 21 mm), with a short curl and an even more swollen last turn, and the shell looks like a human ear.

Swamp pond L. palustris Mull, (shell height 32 mm, width 10 mm) is similar to an ordinary one, but the shell has the shape of a very sharp cone with a small hole and is distinguished by a dark brown color.

Ovoid pond L. ovata. (shell height 18 mm, width 12 mm) has a short curl and the last revolution with a wide ovoid opening.

Prudoviki. Everyone's eating. led.

1 - an ordinary pond; 2 - an ear pond; 3 - swamp pond; 4 - pointed physa (Physa acuta); 5 - ovoid pond (L. ovata); 6 - Key Physa (Physa fontinalis).

Prudoviks are very common in freshwater bodies of water. The common pond is especially prevalent everywhere. To collect the pond, there is not even the need to use the net, as they are kept near the surface, and sometimes on the surface of the water, and can easily be removed from underwater objects by hand. Very often you have to catch empty pond shells.

Movement. If you put the caught pond in a jar of water, it slowly begins to crawl along the walls of the vessel. At the same time, a wide leg with a flat sole, which serves to crawl, and a head with two long triangular tentacles, at the base of which a pair of eyes sit, extends from the opening of the shell. By sticking the sole to the underwater objects, the snail glides forward smoothly. Gliding is achieved by wave-like contractions of the muscles of the sole, which is easy to observe through the glass of the vessel. It is very remarkable that the snails can wander along the surface of the water, hanging from it with their sole. At the same time, the animal leaves a tape of mucus that stretches along the surface of the water and can be detected if you hold a stick behind a crawling snail or powder the surface of the water with lycopodium (clown seed). It is believed that snails moving in this way take advantage of the surface tension of the liquid, hanging from the bottom to the elastic film that is present on the surface of the water due to tension.

The described crawl is easy to observe on excursions with a calm surface of the reservoir.

If the snail crawling in this way is slightly pushed so that it plunges into the water, then it is clear that the animal again, like a cork, floats to the surface. This phenomenon is explained by the fact that there is air inside the respiratory cavity of the animal that supports the cochlea like a swimming bladder. The snail can arbitrarily compress its respiratory cavity: then the mollusk becomes heavier and falls to the bottom. On the contrary, when the cavity expands, the snail floats to the surface without any push in a vertical line.

Try to immerse a pond floating on the surface of the water in water and disturb its soft body by touching it with a tip (tweezers, a wand, etc.). The leg immediately retracts into the sink and air bubbles burst through the breathing hole. After this, the mollusk sinks to the bottom and is no longer able to rise to the surface except by crawling onto aquatic plants, due to the loss of its air float.

Breath. Prudovik belongs to the pulmonary mollusks and breathes atmospheric air. The way in which he takes air is not difficult to observe on excursions. Rising to the surface of the water, the pond opens its breathing hole, which is located on the side of the body, near the edge of the shell. In a calm state, this hole is closed by the muscular edge of the mantle. Air is drawn into a vast pulmonary integrity, the walls of which are formed by a mantle pierced by a rich network of blood vessels. The exchange of gases occurs through the thin wall of the mantle, while the mantle cavity plays the role of the lung.

The pond can stay under water without refreshing the air of its pulmonary cavity for a very long time. This is due to the fact that the air enclosed in the pulmonary cavity is used during breathing very perfectly, and the oxygen in the air is gradually replaced by carbon dioxide. In addition, snails probably breathe through the skin, extracting oxygen dissolved in water.

Prudniks feed on plant foods: leaves and stems of aquatic plants on which they live. The tissue of the plant is scraped off with the help of a special organ covering the tongue, which bears the well-known name of “grater”; the mouth of the mollusk can be clearly seen through the glass of the vessel when it creeps along the wall of the jar.

Large ponds (Limnaea stagnalis) are extremely voracious and cause considerable damage to plants in the aquarium, why only small species should be planted in the aquariums. Sometimes pond-eaters devour, in addition to parts of plants, and small animals (hydras, protozoa), eat fish eggs, meat, and even the corpses of sleepy fish and dead snails.

Pond ponds reproduce by eggs, which they lay on aquatic plants or other objects (Fig. 189). The eggs are connected by a common mucous membrane, and the entire clutch looks like a transparent gelatinous sausage. Each animal lays several such clutches during the summer (up to 20).

Clutches of mollusks. Is eating. led. (Orig.)

1 - a pond; 2 - coils; 3 - bitinia.

In about 20 days, tiny cloves come out of the eggs, which grow quite quickly, eating plant foods. The development of eggs is very convenient to observe in the aquarium.

Interestingly, the pond fish can multiply, far from reaching their maximum growth. For example, an ordinary pond swimmer becomes sexually mature at the end of the first year of his life, when he grows only half his normal size. All the ponds are hermaphrodites. In some species, even self-fertilization (ear pond) was observed.

When the ponds settled by ponds dry out, not all mollusks die. The large pond (L. stagnalis) when the pond dries out, releases a dense film that closes the hole in the shell. Some of the most adapted forms of mollusks tolerate being out of the water for quite some time. So, the common pond lives without water for up to two weeks. L. peregra mull. - more than a month. In this regard, L. truncatula mull is particularly endurance. (Fig. 190), which sticks with mucus to the substrate, and L. palustris Mull. In one experiment, 4 specimens of the latter species remained alive after a month in the desiccator over calcium chloride.

Pond (Limnaea truncatula). Is eating. led.

When freezing ponds, mollusks do not die, freezing in ice, and come to life when thawing. According to S. A. Zernov, for the vicinity of Moscow, more than a hundred organisms are known that possess this ability, including 5 species of mollusks.

Most pond animals are either indifferent to humans, or even useful to them, such as the large pond and the oval pond, which sometimes serve as food for fish. But there is one extremely harmful small species among prudniks - L. truncatula (Fig. 190), which contributes to the development of helminthic disease in sheep and cattle, known as fascioliasis, or dropsy of the liver (popular name).

The species of interest to us is distributed throughout the country. The mollusk lays eggs (9-25 pcs.) Several times a year, reaches maturity in 6-7 months and lives about two years. He lives along the banks of rivers and lakes, in swamps, in small puddles and grooves, even in ruts of roads filled with water (dwarf forms).

Sometimes this pond is propagated in large quantities: for example, in one case, 323 specimens were found on 4 m. In another case, an average of 125 was found per 1 liter, which yields 1.25 million per hectare. Thus, on 1 ha thousands of sheep can become infected with fluke.

The question naturally arises of combating this harmful mollusk.

One of the means is not to graze animals in humid meadows and to drain the pastured lands. Of the chemical methods of control, it is recommended that the transmitter be destroyed with milk of lime (1000-1400 kg of lime per 1 ha), sodium chloride, potassium hydroxide, and vitriol. However, the fight against Limnaea truncatula is very difficult: chemical methods roads, and pasture drying does not always give positive results due to the marked ability of the mollusk to withstand drying.

Luzhanka and bitinia

Luzhanki (Viviparus viviparus L., Paludina vivipara) belong to the class of gastropods (Gastropoda), to the order of the anterior gill (Prosobranchia), to the family of meadow (Viviparidae).

Luzhanka is a large snail with a spirally curled shell, which has the appearance of a blunt cone of yellowish-brown color (shell height 40 mm, width 30 mm). Three dark brown stripes pass along the turns of the shell. The hole in the sink can be tightly closed by the horn cap.

Luzhanka and bitinia. Eats led. 1 - real lawn (Viviparus viviparus), 2 - striped lawn (V. fasciata), 3 - tentacle bitinia (Ltithynia tentaculata).

There are two close, very similar to each other species: a real lawn, characteristic of standing water bodies (V. viviparus), and a striped lawn (V. contectus Millet), found in running waters. The latter species is somewhat smaller than the first and has a more blunted apex of the shell and the opening of the shell is pointed upward. In addition, there are still various local varieties on which we will not dwell.

A representative of the close Hydrobndae family is somewhat similar to a lawn - tentacle bitinia (Bithynia tentaculata L.), a small snail (shell height 10 mm, width b mm) with a conical shell equipped with a calcareous lid.

And lawns and bitinia are ordinary inhabitants of our reservoirs and are often found in many. Luzhanka usually live in reservoirs with a muddy bottom, sometimes completely dotting it. When fishing for lawns, a net should be carried out along the very bottom of the reservoir where the animals are kept. Due to the presence of the lid, it is difficult to mix the lawn and bituminia with other mollusks similar to them, and even the most inexperienced excursionist will distinguish them at first sight.

Movement. The lawns caught from the water lie motionless with closed covers. But, being lowered into the water, the snails after a while open the lids and push their dark-colored body out of the shell, dotted with small yellow specks. The head of the lawn is extended in front into a short proboscis, on which the mouth is located. On the head there is a pair of thin tentacles, at the outer base of which is placed over the eye. A wide, flat leg gives the snail the ability to slowly crawl through underwater objects.

And the lawn and bitinia always stay at the bottom of the reservoir and do not float to the surface, like ponds and coils. In case of danger, they close the sink with a lid, which serves these snails as an excellent protective shield.

Breath. Unlike the pond and coil, the lawn and bitinia belong to the gill snails, which extract oxygen from the water using the gill apparatus, hidden under the sink. The meadow has a well-developed comb-shaped gill with numerous branchial outgrowths, which somewhat resemble the gills of fish. Thanks to water respiration, the meadows and bitinia are very sensitive to water quality and, under adverse conditions, die much faster than ponds and coils.

Snails feed on various plant debris that are found at the bottom of ponds. Bitinia eagerly eats green algae on underwater objects.

Of considerable interest is the reproduction of the lawn. Its Latin name Viviparus - the live-bearer - indicates that it gives birth to live cubs, bearing eggs and juveniles in its body, which is how it differs from other freshwater gastropods. Young lawns are not like adults, not only in size, but also in the shape of a shell. The latter appears to be faceted and covered with hard bristles, which subsequently fall away. Unlike ponds and coils, lawns are dioecious. Having found a mature female, you can immediately open her shell on an excursion and, breaking open the spiral, show young, unborn lawns at different stages of development.

Unlike lawns, bitinia reproduces by laying eggs on aquatic plants. Its masonry has a very peculiar shape and is easily distinguishable from the clutches of other mollusks: it consists of hexagonal eggs, which are arranged in a double row and are invested with gelatinous substance, forming an elongated mucous cord (Fig. 189).

Finally, we note the often observed fouling of lawns with algae, which cover their shells in the form of a green bloom, completely hiding their characteristic pattern. Sometimes algae grows so abundantly that they completely cover the shell with a green fluff.

A similar fouling with algae is characteristic, although to a lesser extent, of pulmonary mollusks, for example, coils.

Remarkable is the resistance that the lawns find when the reservoir inhabited by them dries, which is greatly facilitated by the presence of a lid. So, it was observed that the striped meadow (Viviparus contecfts) survived outside the water for up to 10 months, while burying itself in soil to a depth of 15 cm.

Coils

Coils (Planorbis) belong to the class of gastropods (Gastropoda), to the order of pulmonary (Pulmonata), to the family of coils (Planorbidae).

The coil can be distinguished at first glance due to its extremely characteristic shell, curled in one plane in the form of a spiral cord.

The horn reel (P. corneus L.) attracts the most attention, the largest among the others (shell diameter 30 mm, height 12 mm), reddish-brown. This coil is found everywhere in both pond and lake waters.

Coils Is eating. led. (Orig.)

1 - horn coil (Planorbis corneus); 2 - edge coil (P. marginatus); 3 - keel coil (P. carinatus), 4 - circular coil (P. vortex); 5 - curled coil (P. contortus); 6 - smooth coil (P. glaber)

Among the coils of medium size, we note an edge coil (P. marginatus L.) (shell diameter 15 mm, thickness 3.5 mm), the revolutions of which are provided with a filamentary keel, passing in the middle of the revolution; a keel coil (P. carinatus L.) is found much more often than the previous one, almost the same size as the filamentary keel shifted to the lower side. A slightly smaller circular coil (P. vortex L.) (shell diameter 10 mm, thickness 1 mm) has a very flat shape, with tightly wound turns, with a keel without a filiform appendage.

Next, we note an almost black curled coil (P. contortus L.) (shell diameter 4-5 mm, thickness 1.8 mm), the revolutions of which are very closely wound, so that their number reaches 7-8. Almost the same size, but with a small number of rapidly growing revolutions, P. complanatus L. shells

The movements of the coils resemble the movements of the pond. Crawling, snails expose their dark soft body far from the shell and move around underwater objects with their wide flat legs. On the head there is a pair of thin tentacles, at the base of which eyes are placed. Coils are exactly the same as ponds, they can wander along the surface of water bodies, hanging from a film of surface tension of a liquid.

Coils breathe atmospheric air, absorbing it into the pulmonary cavity formed by the walls of the mantle. The respiratory opening leading to the specified cavity opens on the side of the body, near the edge of the shell. It opens when the coil rises to the surface of the water for a supply of air. With a lack of air, the coil uses a special leathery outgrowth, which is placed on the body near the pulmonary opening and plays the role of a primitive gill. In addition, the coil, in all likelihood, breathes directly through the skin.

Nutrition. Coils feed on plant foods, eating parts of plants that are scraped off with a grater. Especially willingly, these snails eat a green coating of small algae that forms on the walls of the aquarium. Outside, it is easy to observe through the glass how the animal acts with its grater, raking the plaque like a spatula. It is very possible that coils can feed on animal food. At least in captivity, they willingly pounce on raw meat.

Reproduction. Coils reproduce with eggs, which are laid on the leaves of aquatic plants and other underwater objects. The laying of the horn coil is constantly found on excursions and is so characteristic that it can be distinguished without difficulty: it has the appearance of a flat gelatinous plate of an oval shape yellowish or light brown in color and contains several tens of round pinkish transparent eggs. After two weeks or more (depending on the temperature of the water), tiny eggs are removed from the eggs, which grow quite quickly. The caviar of coils, like other snails, is readily eaten by fish and killed by them in a large number. Like a pond, coils are hermaphrodites.

Interesting is the behavior of the coils during drying of the reservoirs in which they are found. They dig into wet sludge, like a large horn coil (P. corneus). Sometimes this coil remains on the surface of the soil, sucking the mouth to the sludge if moisture remains in it, or releases a dense water-insoluble film, which closes the hole in the sink. In the latter case, the body of the mollusk gradually shrinks, eventually occupying the third part of the shell, and the weight of the soft parts drops by 40-50%. In this state, the mollusk can survive out of water for up to three months (edge \u200b\u200bcoil P. marginatus P. planorbis).

List of references

B.E. Raikov, M.N.Rimsky-Korsakov. Zoological excursions. 1

Those of you who have an aquarium at home are familiar with the clam by the great pond. Having studied this animal, you will understand why the class to which it is referred is called the gastropods, you will learn how the gastropods move, the structure of their organ systems and how they function.

A large pond (Fig. 27.1) lives in rivers, lakes and ponds. Its conical shell 4-5 cm high is twisted by a spiral in 4-5 turns and ends with a sharp tip. The entire body of the mollusk is placed in the shell. But the pond can only push the head, leg and front of the body through the hole in it (the mouth); the rest of it is covered with a mantle firmly connected to the sink.

On the head of the pond, two tentacles are visible organs of touch and embrace, and near them - a pair of eyes. The mouth is located at the bottom of the head. It can be seen when the mollusk crawls on the glass of the aquarium, scraping off a thin coating of algae.

The large muscular leg (Fig. 27.2) of the pond is reminiscent of an iron. Controlling its muscles in waves, the pond moves slowly along the surface of stones and aquatic plants. The large pond can move along the bottom side of the surface film of stagnant water in the “upside down” position. Facilitates the movement of the mollusk mucus secreted by the epithelium of the leg. You can see how the pond creeps, using a magnifier at the moment when the mollusk moves along the glass wall of the aquarium.

A variety of gastropods, their role in nature.This is the most numerous class of mollusks; they have mastered both the aquatic environment and land.

Most of them have spiral shells. A grape snail is widespread in Ukraine (Fig. 27.6); a river live-bearer lives in water bodies (Fig. 27.6), breathing with gills. The Rapana mollusk living in the Black Sea is a migrant. He came here in the 40s from the Sea of \u200b\u200bJapan on the bottoms of co-rable. Not meeting the natural enemies in the Black Sea, the rapana “took root” and replaced the Black Sea oyster and many other mollusks. Material from the site

Among the gastropods, there are species that do not have shellfish (Fig. 27.7). Slugs willingly settle on cabbage and strawberry beds, damaging these plants. In the Carpathians live slugs up to 8 cm long with dark purple, dark green and reddish color. Many gastropods inhabit the tropics on land and at sea (Fig. 27.8).

On this page, material on the topics:

• Role in nature and importance for humans of gastropods

• Clams gastropods big pond

• Report on the Pond

• The role of the pond in human life

• Gastropods and their significance in nature

Questions about this material:

Mollusks

The body of most mollusks is enclosed in a calcareous shell that protects them. Under the shell are the mantle characteristic of mollusks.

Freshwater mollusks are found in almost all of our still and weakly flowing waters. They easily adapt in aquariums, and some successfully breed in them and live for years. Many species of freshwater mollusks are reduced in number, they can not be collected and kept in aquariums. Of the mollusks, the most common are gastropods. In gastropods, when moving from a shell, a part of the body, called the leg, protrudes. Its abdominal side is flattened and serves for movement, in front there is a head with movable tentacles (they are easily retracted with fright), eyes are visible on the head. Freshwater gastropods are divided into breathing lungs and gills. The former are forced to rise to the surface of the water in order to breathe atmospheric air. They can crawl over water, so aquariums with such snails should be covered with coverslip. Shellfish with gill respiration require clean, oxygenated water.

The leg of the gastropod is a perfect organ of movement both on a flat surface and along acute-angled gravel, both along the plane and along the thin stems of plants. Mollusk can move in an aquarium and along invisible thread mucus released by him or another snail earlier. It seems that he slowly swims in the water column. The remarkable ability of a number of water snails to glide over the surface of the water is attached to it from below. The surface film in this case bends downward (this is clearly seen from above), but does not tear. However, young ampullaria can use the film for movement, but it does not withstand large, old ones.

The body of the snail in danger is completely hidden in the shell. At the pond and coil, the leg goes into the mantle, and the mantle can shrink, going deep into the shell. When drying, the mantle shrinks and pushes the body into the depths, preserving the remaining moisture. In gill mollusks and ampullaria, a calcareous cap is fixed on the back of the back of the leg (it, like the shell, grows its size in rings). When the leg hides in the sink, the lid covers the mouth and holds with great force (it is almost impossible to open a living mollusk without breaking the edge of the shell). In a closed sink, moisture lasts longer.

Pulmonary mollusks rise to the surface for air. The pond is lighter than water, it breaks away from the substrate and floats, the leg wriggles until it touches the surface of the water. Ampullaria creep to the surface, but go down by parachuting, break away from the substrate and, putting up a leg, straightening the tentacles, slowly sink to the bottom. The breathing opening opens with a slight pop or smacking sound. In the ampullaria, a breathing tube extends (up to 10 cm long) and you can see how air is pumped by the movement of the body into a special mantle cavity. The pond and coil in the mantle have a breathing hole; it opens when the edge of the mantle comes in contact with air. The more saturated the water with oxygen, the less often snails rise behind the air, since, in addition to air, mollusks have very developed skin respiration over the entire surface of the body. The body of the pond and a number of other gastropods are covered with cilia, which move all the time, updating the water around. At the coil, a mantle wing with a large number of blood vessels extends from the shell. It serves as an additional respiratory organ.

In prudoviks, the mantle cavity serves both for air and water respiration. In winter, snails eject air from the mantle under ice and fill it with water. In the experiment, the pond dwellers lived without air for three months, there was water in the robes, occasionally the mollusk opened a hole, throwing out part of the water and absorbing a new portion. This is a rare case in nature when one organ works both as a lung and then as a gill.

Fig. 16. Luzhanka

In Geneva and others deep water lakes at depths of more than 100 m, small forms of ordinary freshwater ponds live, which never rise to the surface; there is always water in their robes. The same can be observed in lakes with a strong surf, which can destroy shells of mollusks, here, the ponds are always at depth, breathe oxygen dissolved in water. Freshwater gastropods are predominantly herbivorous animals. They have a toothed grater in their mouth, whose work is clearly visible through the wall of the aquarium. Algal fouling is usually scrubbed, but a number of ponds and ampullar species are eaten by the soft tissues of higher plants, the bodies of aquatic animals. Ampullaria eagerly eat live bloodworms and tubule. All mollusks with pleasure eat dry daphnia, dry gammarus, ampullaria - planed meat, white bread. Bottom forms (lawns, bitinia) feed mainly on detritus, excrement of aquatic animals (Fig. 16). Tropical and Amur snails of the melania type, which are widespread among aquarium lovers, search for detritus freely penetrate the soil and thereby drain it, help wash the roots of plants with fresh water (compare with the role of earthworms in the soil).

In school aquariums, the following species are of interest for maintenance and observation.

An ordinary pond - a shell is thin-walled, elongated, large (6 - 7 cm high), with a sharp curl and a thin tip. Widely distributed in standing and slowly flowing reservoirs of the USSR. It is found in lakes. Not found in Crimea. Propagated by eggs; masonry - a transparent curved roller 4 - 5 cm long with a width of 6 - 8 mm; more than 100 eggs. The aquarium reproduces successfully. Large snails can devour young ones. Hermaphrodite. Development in eggs 20 to 25 days.

Fiza - the shell is thin-walled, transparent, with a sharp curl, height up to 1 cm. The shell is curled to the left. The edge of the mantle protrudes beyond the sink. The leg is dark brown. Egg laying is sausage-shaped. Distributed in most reservoirs of the USSR. In an aquarium, for unknown reasons, it sometimes crawls out of the water onto the walls, dries and dies.

Fizastra, the “red fiza,” is a thin-walled shell, more obtuse than that of a fiza, up to 2 cm high. The shell is curled to the left. The body and mantle are pink, brown or red. The most common in aquariums was a decorative red shape. Lifestyle is similar to physa. Sometimes it eats holes in the soft tissues of the leaves of higher plants. Acclimatized in aquariums from water bodies of South Australia.

Fig. 17. Horn coil

The horny coil - the shell is twisted in one plane (Fig. 17) is dark brown, the walls are thicker than ponds, the diameter of the shell is 3-4 cm. Along with the lungs, there is a part of the mantle exposed from the mouth, acting as gills. The body is brown, dark cherry, chocolate, tentacles filiform. It feeds on algae, does not touch higher plants. Mating is mandatory, one snail does not breed, masonry is flat. Everywhere in the reservoirs of the USSR.

Gelizoma, the “red coil”, looks like a horn coil, but smaller (up to 2 cm) in diameter of the shell. The body and mantle shining through the shell are brown, but more often carmine-red. Lifestyle like a reel. Popular among aquarists, clam from reservoirs of Brazil.

Ampullaria is a large mollusk from the genus of South American snails popular among aquarists. The height of the spiral wide-conical shell is 65 mm (Fig. 18). The mouth is closed by a cap. Diclinous. Laying above the water in the form of an oblong cluster of large (with a diameter of 1.2 - 1.5 mm) eggs, covered with a calcareous shell. The color of the masonry varies from pink to silver-orange. Snails leave their eggs after 4-6 weeks, eggs develop only in moist air (Fig. 19).

Fig. 18. Ampullaria with a respiratory tube

This type of ampullaria rarely affects higher plants, lives well in an aquarium with other animals. The other 4 species feed mainly on higher aquatic vegetation; the shell of one of them reaches a height of 12 cm.

Viviparous lawn - a mollusk with gill breathing, widespread, held at the bottom of water bodies, has a spiral curled cone about 50 mm high. Such large shells are more common in river puddles. The mouth is closed by a cap; dioecious; the embryos develop inside the body of the female. Young snails leave after maturing several pieces a day, their shells are covered with bristles and have a beautiful pattern of dark stripes, the height of the shell is up to 5 mm (up to 12 mm in the Ussuri meadow). There are a number of other domestic and tropical gastropods that can be successfully kept in aquariums. It should be remembered that many fish eat small newborn snails, tear off tentacles in larger ones. Macropods and a number of cichlids feed on snails. They may be attacked by a hungry swimming beetle and its larvae. Hydrophobic larvae are more specialized in mollusk feeding. Some of our natural snails (small pond and a number of others) are carriers of dangerous diseases; their presence in school aquariums is undesirable.

Fig. 19. Newborn ampullaria

Live collection of these animals, in which different kinds placed in separate small aquariums, can not only be an adornment of a corner of wildlife, but will contribute to the development of the concept of classification.

Observing the movement, respiration, nutrition, and reproduction of mollusks will help students better understand the training material on the topic “Type of mollusks”.

The gastropods are best kept in rectangular wide jars. Fine sand suitable for the soil, planted with the most unpretentious plants, is suitable. Large ponds are very voracious and sometimes completely destroy plants. Therefore, in aquariums with these animals, frequent replacement of plants is required.

Luzhanka better live in shallow vessels with silty soil, in which they could dig in and look for food in it, consisting of rotting plant debris.

With proper care, mollusks live from 2 to 5 years.

In lessons, the common pond is more convenient for consideration. Students examine the shape of the body, the head and sensory organs on it, the muscular leg, the protective color. If you do not disturb the pond, then in the lesson you can observe his movement with the help of his leg, as well as movements associated with breathing. Every 5 to 8 minutes, the pond grows to the surface of the water and opens a breathing hole. Students through a magnifying glass examine the breathing hole of the pond and establish its location.

Demonstration material can be represented by other types of mollusks (horn coil, viviparous lawn, ball, etc.). Their demonstration contributes to the development of the concept of animal diversity and adaptability to the environment.

In the lessons, reports on various observations of mollusks contained in a corner of wildlife can also be presented.

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