In the phylum Flatworms there are three classes:

Ciliated worms, or Turbellaria,

Tapeworms

Flukes.

Class Turbellaria. A representative of this class, white panpanaria, lives in ponds, ditches, and leads an active nocturnal lifestyle. At the anterior end of the flattened body there are two eyes. The body of the animal is covered with a skin-muscle sac. Its outer layer is represented by ciliated epithelium with mucous glands. Under the single-layer epithelium are three layers of muscle fibers.

The planaria feeds on small crustaceans, worms and the remains of large organisms. The mouth leads into the pharynx, which turns into a branched intestine. Single-celled glands located in the intestinal walls secrete enzymes for extracellular digestion, small digestive particles are ingested by phagocytic cells, and the digestion process is completed intracellularly. Undigested food remains are expelled through the mouth.

The excretory system is formed by two longitudinal excretory canals, which branch repeatedly, ending in “flame cells” that ensure the release of harmful breakdown products and osmoregulation.

Reproduction is asexual and sexual. Asexual reproduction is carried out by transversely dividing the llanaria in half. Each half then regenerates the missing body parts. Planarians are hermaphrodites. Numerous testes produce sperm, which travel through the vas deferens into the seminal sacs and are stored there as sperm. The ovaries are located on the sides of the body in the parenchyma. From these, the eggs pass through the oviducts into the spermatic receptacle, where fertilization occurs. Fertilization is preceded by copulation.

Prevention of infection for humans: do not drink raw water from reservoirs, thoroughly wash vegetables and herbs.

Flatworms belong to the group of three-layered animals. In addition to the ecto- and endoderm, the embryos of flatworms develop a third germ layer - mesoderm. During development, these three leaves form the tissues and organs of the worms' body.

Flatworms have bilateral (two-sided) symmetry; only one plane can be drawn through their body, dividing the body into symmetrical halves. With bilateral symmetry, the body is divided into right and left halves: ventral and dorsal sides, anterior (head) and posterior (tail) ends. These signs are a consequence of aromorphoses that occurred in the ancestors of flatworms. Flatworms are protostomes.

The body of flatworms has a leaf- or ribbon-like shape and is always flattened in the dorsoventral direction, which gave rise to the name of the type. The body wall is formed by a skin-muscle sac. It consists of a layer of epithelium covering the outside of the body, and continuous layers of muscle underlying it. The outer layer is represented by circular muscles, the inner layer is longitudinal. Between them there are usually diagonal muscles. Contraction of the muscular elements of the skin-muscular sac provides the characteristic “worm-like” movements of flatworms.

The internal organs are immersed in loose connective tissue of mesodermal origin - parenchyma containing numerous cells. The functions of the parenchyma are diverse: it has a supporting role, serves to accumulate reserve nutrients, and plays a role in metabolic processes. Since parenchyma fills the space between organs, flatworms are called cavityless, parenchymatous animals. They do not have a body cavity.

The excretory system in flatworms is represented by excretory organs - protonephridia. Their function is to remove intracellular breakdown products (dissimilation products) from the body. The latter are excreted from all cells of the body and enter the intercellular spaces of the parenchyma. From here they are extracted by special cells with a “flickering flame”, i.e. with a bunch of eyelashes. Inside these cells, the tubules of the excretory (excretory) system begin. The beating of the cilia drives waste products through the tubules. Coming together, these tubules form increasingly larger tubes that flow into paired (right and left) canals of the excretory system, which merge together and open outward into the excretory pore.

Flatworms are hermaphrodites. The reproductive system consists of the gonads (testes and ovaries) and a complex system of canals that excrete reproductive products.

Animals belonging to the type of flatworms are characterized by:

1. three-layer, i.e. development of ecto-, ento- and mesoderm in embryos;
2. the presence of a skin-muscle sac;
3. absence of a body cavity (the space between organs is filled with parenchyma);
4. two-sided symmetry;
5. body shape, flattened in the dorsoventral (dorsoventral) direction;
6. the presence of developed organ systems: muscular, digestive, excretory, nervous and reproductive.

The phylum flatworms (Plathelminthes) includes 6 classes. Will be discussed here

• Class ciliated (Turbellaria)
• Class flukes (Trematodes)
• Class tape (Cestoidea)

Class ciliated (Turbellaria)

About 1,500 species of ciliated worms or turbellarians are known. Turbellaria are distributed in all parts of the globe. Most species live in the seas, where flatworms apparently first arose. Freshwater and soil species are known. Almost all turbellarians are predators. They eat protozoa, worms, small crustaceans and insects. There are intestinal forms, as well as species with straight and branched intestines. Typical representatives of ciliated worms are planarians.

A small (10-15 mm long) leaf-shaped worm that lives in ponds and low-flowing water bodies. Planaria can be found on pieces of wood rotting underwater, fallen tree leaves and plant stems.

Body coverings and movement apparatus. The body is covered with cilia. The body wall of planaria, like all flatworms, is formed by skin and muscles, which, tightly fused, make up a skin-muscular sac. Single-celled mucous glands are developed in the skin. Muscles are represented by fibers arranged in three layers (circular, oblique and longitudinal). This allows planarians to move and change their body shape somewhat.

No body cavity. Inside the skin-muscle sac between the organs there is spongy parenchyma tissue, consisting of a mass of cells, the small spaces between which contain tissue fluid. It is associated with the movement of nutrients from the intestines to all parts of the body and the final waste products to the excretory organs.

Digestive system. The mouth is located on the ventral side, in the middle or in the posterior third of the body. The digestive system consists of an anterior section - the ectodermal pharynx, and a middle section, which has the appearance of highly branched trunks ending blindly. Undigested food remains are expelled through the mouth. In ciliated worms, along with extracellular digestion, intracellular digestion plays an even greater role. Some planarians have no intestine and digestion is carried out only by phagocytic cells. Aintestinal tubellaria are of considerable phylogenetic interest (see below).

Excretory system. Protonephridia begin deep in the parenchyma as stellate-shaped terminal or terminal cells. The terminal cells contain tubules with a bunch of cilia that oscillate like a candle flame. Hence their name - flickering, or ciliary, flame. Terminal cells flow into tubules, the walls of which already consist of many cells. These tubules are numerous and permeate the entire body. They open into lateral canals, which have a large lumen, and, finally, communicate with the external environment through excretory pores. Protonephridia perform the functions of osmoregulation and removal of dissimilation products from the body. Terminal cells absorb tissue fluid from the parenchyma. The flickering flame promotes its movement through the channels to the excretory pore.

Nervous system. In ciliated worms, at the head end there is a paired cerebral ganglion and nerve trunks coming from it, of which two lateral trunks, consisting of nerve cells and their processes, reach the greatest development. The transverse trunks are connected by ring bridges, due to which the nervous system takes on the appearance of a lattice.

Sense organs still primitive. They are represented by tactile cells, which the skin is rich in, one or more pairs of pigmented ocelli, and in some, balance organs - statocysts.

Reproduction. Planarians are hermaphrodites with a complex reproductive system. They have widely developed asexual reproduction and well-defined somatic embryogenesis. Thanks to this, they serve as classical objects for studying regeneration processes.

Origin. The question of the origin of eyelash worms has not been completely resolved. The most widely accepted hypothesis is V.N. Beklemisheva (1937). He believes that the oldest turbellarians are the intestinal ones. According to his hypothesis, they originated from the planula-shaped (i.e., similar to the planula - the larva of coelenterates) ancestor of flatworms, which switched to crawling. This way of life contributed to the separation of the dorsal and ventral sides of the body, i.e., the formation of bilateral symmetry.

According to the hypothesis of A.V. Ivanov (1973), the lower intestinal turbellariae evolved directly from the phagocytella, bypassing the coelenterates. According to his concept, coelenterates are a side branch of the animal world.

Type Annelids are bilaterally symmetrical, three-layered animals with a secondary body cavity.

Structural features

The body is segmented, the segments are located sequentially one after another; all are the same, so the rings are characterized by homonomic segmentation. On the sides of the segments there are setae - organs of movement. The body consists of a prostomium (head segment), a homonomically segmented trunk and pygidium (anal lobe)

Integument - skin-muscle bag:

cuticle - a thin layer of dense substance;

hypodermis is a single-layer epithelium in which metabolism occurs intensively,

forms the cuticle

two layers of muscles: circular and longitudinal

The body cavity is secondary (as a whole) segmented, has its own epidermal lining - mesothelium, its outer layer is adjacent to the walls of the sac, the second - to the walls of the digestive tube. The leaves grow together above and below the tube, forming the dorsal and ventral mesentery. Transverse partitions are generally divided into chambers, the number of which corresponds to the number of segments. The coelomic fluid is in constant motion and performs the following functions: supplies organs with nutrients and O2, promotes the removal of CO2 and metabolic products, transports biologically active substances and phagocytes.

Features of life

Support is provided by a hydroskeleton

Movement is carried out using circular and longitudinal muscles. In polychaetes, parapodia first appear, from which dorsal and ventral branches arise. A thin tendril extends from each branch, which performs tactile and olfactory functions. In oligochaetes, in place of parapodia there are tufts of setae.

Nutrition is carried out by the digestive system: the foregut (mouth, pharynx, esophagus with goiter, stomach with muscular walls), the middle and hind intestine (ending with the anus). Digestion and absorption of food occurs in the midgut

Transport of substances occurs through the circulatory system, which appears for the first time. The circulatory system is closed, consists of dorsal and abdominal vessels connected to each other by ring vessels, small vessels depart from these vessels, forming a network of capillaries, blood movement is carried out due to the pulsation of ring vessels, there is no heart. Blood can be colorless or colored by respiratory pigments: chlorocruorin (green), hemoglobin and hemoerythrin (red).

Breathing is carried out with the participation of the respiratory system, which appears for the first time.

Ringfishes develop gills - thin-walled formations with an extensive network of vessels, which are located on the parapodia and head. In many ringlets, gas exchange occurs through the integument.

Excretion occurs using the excretory system, which is represented by metanephridia (a pair in each segment). Metanephridia begins with a funnel - a nephrostomy, facing the coelomic cavity; the funnel continues into a convoluted tube, which opens on the lateral surface of the adjacent segment with a nephridial pore. In primitive polychaetes, the excretory function is performed by protonephridia, which contain cells with flagella at the inner ends - solenocytes. Nephridia excrete liquid waste products of the worm, solid ones are phagocytosed by mesothelial cells and cells of some organs (vascular walls).

Regulation of functions is carried out by the nervous system of the nodal (ganglionic) type. The central nervous system consists of supra- and subpharyngeal ganglia, connected by jumpers and the ventral nerve cord. The PNS is represented by nerve processes and nerve endings.

The sense organs of wandering polychaetes are well developed, while in sessile forms they are reduced

organs of vision are represented by the supracerebral eyes (2-4), in addition to them or instead of them

organs of vision may be on the palps or near the anus

chemical sense organs (amphids) on the palps

organs of touch - sensory cells located in the skin, on the palps,

tentacles, antennae;

balance organs (statocysts)

Reproduction is sexual, which is carried out by a dioecious reproductive system in polychaetes, and a hermaphroditic reproductive system in oligochaetes. Fertilization can be external or internal.

Earthworms are hermaphrodites, but they undergo cross-fertilization:

during the process of copulation, hermaphroditic sexual partners are closely attached to each other with their abdominal parts, with the head ends of each of them facing in different directions, and the girdle is located opposite the opening of the spermatic receptacle; each sexual partner secretes a mucous sheath, which merges with the same sheath of the other worm and a common mucous sheath is formed, covering both of them; each partner secretes a drop of seminal fluid from its ♂orifices (15th segment), which flows to the openings of two pairs of seminal receptacles (on the 9th and 10th segment) and is sucked into them; as a result, each partner receives the sperm of another individual (hermaphroditism of oligochaetes does not prevent the exchange of genetic material!); after copulation, the partners separate and after a while begin laying eggs; glands of the girdle secrete a secret that forms a mufa, into which 1-3 eggs are laid, and then the sperm obtained during copulation is squeezed out; a lot is released into the cocoon, which will later be needed to feed the embryos; the coupling slides through the head end, hardens and turns into a cocoon that protects the eggs

In aquatic ringworms, asexual reproduction occurs: the body of the worm can break up into several unequal parts (disordered division) or into separate segments (multiple fragmentation)

Development in polychaetes and leeches is direct, in polychaetes it is indirect, during which a larva, a trochophore, is formed. It floats for a while, then settles to the bottom and turns into an adult worm.

Regeneration is well developed in oligochaetes and polychaetes; in leeches this ability is lost.

Variety of annelids

	Features of the organization	Representatives
Subtype Beltless The skin-muscular outgrowths - parapodia - are well developed; branches extend from the basal part: dorsal (notopodia) and ventral (neuropodia). A tendril extends from each of the branches, which perform tactile and olfactory functions, and in some, the dorsal tendril grows and serves as a gill. Notopodium and neuropodium contain tufts of supporting setae that provide movement. Girdleless animals are dioecious, their genital organs develop in all segments of the body. Development occurs with metamorphosis.
	Most live in the seas, only a few have adapted to life in fresh water. Free-living and benthic, they can secrete protective tubes around themselves. Predators, but there are herbivores and omnivores; There are commensals living inside sponges, in the shells of hermit crabs or on starfish. On the prostomium there are tentacles (touch), palps (touch, directing food to the mouth), simple ocelli, statocysts. Breathing is cutaneous or through gills. Circulatory system: dorsal (contracts) and abdominal vessels, which are connected by annular vessels (in each segment). Development is indirect: eggs → floating trochophore larvae → worm.	Crawling: Nereis, lepidonotus; burrowing: sandworm; sessile: telepus (in an organic tube reinforced with pebbles), serpula, spirorbis (in a calcareous tube)
Subtype Belt The girdle zone is characteristic; they are all hermaphrodites and undergo direct development
	Inhabitants of fresh water bodies and soil, rarely live in the seas. The body is segmented (up to 600 segments), parapodia are absent, in their place are tufts of setae (promote movement, enhancing adhesion to the substrate); some larger ones - genital setae - promote mating. In the epithelium of the musculocutaneous sac there are mucous cells that secrete a lot of mucus, which is necessary for gas exchange. On the front of the body of sexually mature individuals there is a glandular girdle. Gas exchange occurs through a network of capillaries in the body wall. Circulatory system: dorsal (contracts) and abdominal vessels, annular vessels (contracts) only in the anterior part of the body. The sense organs are poorly developed: usually there are no eyes, sensilla and light-sensitive cells are scattered in the skin. Gonads are found only in some segments (in the earthworm, ♂ organs are in segments 9–15, ♀ - in segments 13–14). Direct development, from egg to worm	Common earthworm, common tubifex, Australian earthworm
	They live in fresh water bodies, seas, and sometimes on land. Among them there are predators that feed on small animals and bloodsuckers that feed on the blood of the host, but do not use it as a habitat. The body consists of 34 segments. There are two suckers: the front one is used for attachment; through the front one, at the bottom of which there is a mouth with teeth and jaws, feeding occurs. The jaws cut through the skin of the animal to which the leech has attached itself, and saliva containing hirudin is released into the wound. Hirudin prevents blood clotting. Blood treated with leech saliva can be stored for a long time in the pockets of its intestines, so the animal can starve for a long time. They have a belt in which eggs are formed.	European medicinal leech, large and small false leeches, fish leech

The meaning of the rings

Comparative characteristics of different types of worms

Signs	Flatworms	Roundworms	Annelids
Total species
	from 0.1 mm (monogenea) - 30 m (Polygonoporus giganticus)	from 0.04 mm (rotifers) to 8.4 m (placentonema gigantisima)	from 0.5 mm to 2.5-3.6 m (megaloscolides australis)
	unsegmented	unsegmented	homonomic segmentation, cephalization
flattened, leaf-shaped or ribbon-shaped	cylindrical in shape with a circular cross-section in cross section	worm-shaped, posterior part flattened
Body cavity	absent	primary (protocoel)	secondary (overall)
Skin-muscle bag	epithelium, 4 layers of muscles: circular, longitudinal, oblique and dorso-abdominal.	cuticle, hypodermis, 4 ribbons of longitudinal muscles	cuticle, single-layer epithelium and two layers of muscles: circular and longitudinal
Digestive system	closed: anterior and posterior branched intestine, no anus	through, consists of the foregut, midgut and hindgut	differentiated, tubular: foregut, middle and hindgut
Respiratory system	absent	absent	gills appear
Circulatory system	absent	absent	closed, no heart, respiratory pigments in the blood
Excretory system	protonephridia	protonephridia or skin glands	metanephridia
	Paired cerebral ganglion and three pairs of nerve trunks	peripharyngeal ring and 2-6 nerve trunks extending from it	peripharyngeal nerve ring and ventral nerve cord
	most are hermaphrodites	most are dioecious	dioecious and hermaphrodite
Development	straight, in some with metamorphosis: egg → Müllerian larva	complex life cycle; egg → larvae: miracidia → redia → sporocysts → cercariae → adolescaria	complex life cycle; egg → oncosphere → finna (cysticercus, acenur, cysticercoid, plerocercoid)
Basic	Eyelash worms, Flukes, Tapeworms	Actually roundworms, rotifers	Oligochaete worms, Polychaete worms, Leeches

11. Cell movement. Organelles of movement. The structure of the flagellum, cilia, centrioles.

12. Adaptations of animals to parasitism.

13. Characteristics of features that distinguish living organisms from inanimate matter.

14. Classification of the animal world.

15. Forms of relationships between organisms (mutualism, predation, parasitism, competition, antagonism).

17. Flagellates (mastigophora): classification, general characteristics of life-support organelles. Plant flagellates (phytomastigina).

18. Animal flagellates (zoomastigina). Parasitic forms and the diseases they cause. Extracellular and intracellular parasites. Adaptations to parasitism.

19. Apicomplexa. General characteristics. Sporozoea: characteristics using the example of coccidia.

20. Coccidia coccidia: development cycle of eimeria.

21. Coccidia coccidia: development cycle of toxoplasma.

22. Haemosporina: development cycle of malarial plasmodium (genus Plasmodium).

23. Ciliates (ciliophora, seu infusoria).

24. Coelenterata: classification, general characteristics of the first two-layer organisms, Cellular specialization.

25. Flatworms (plathelminthes): classification and general structural and functional characteristics of the first three-layered animals.

26. Flatworms (plathelminthes): Flukes (trematoda). General characteristics.

27. Flatworms (plathelminthes): development cycle of the liver fluke.

28. Flatworms (plathelminthes): development cycle of the lanceolate fluke.

29. Flatworms (plathelminthes): development cycle of the cat fluke.

30. Flatworms (plathelminthes). Tapeworms (cestoda): classification and general characteristics.

31. Morphological differences between armed and unarmed tapeworms and tapeworms.

32. Flatworms (plathelminthes). Tapeworms (cestoda): development cycle of armed and unarmed tapeworms. Finnish types.

33. Flatworms (plathelminthes). Tapeworms (cestoda): development cycle of Echinococcus. Finnish types.

34. Flatworms (plathelminthes). Tapeworms (cestoda): development cycle of the broad tapeworm. Finnish types.

35. Roundworms (nemathelminthes): classification. General characteristics of nematodes (nematoda).

36. Roundworms (nemathelminthes): structural features of the reproductive system and the development cycle of the horse roundworm.

37. Roundworms (nemathelminthes): development cycles of pinworms and Trichinella spiralis.

38. Annelida: systematic classification, general morphofunctional characteristics. Development of the coelom.

39. Annelida: characteristics of polychaeta.

40. Annelida: characteristics of oligochaeta. Biocenotic role of earthworms.

41. Annelida: morphofunctional characteristics of leeches (hirudinea).

42. Mollusks (mollusca): classification, general characteristics of gastropoda. 43. Mollusks (mollusca): general characteristics of bivalves (bivalvia) and cephalopods (cephalopoda) mollusks.

I. Subtype Bokonerova – (Amphineura)

44. Arthropods (arthropoda): classification and general characteristics.

45. Arthropods (arthropoda): characteristics of crustaceans (crustacea).

46. ​​Arthropods (arthropoda): general characteristics of arachnids (arachnida).

47. Arthropods (arthropoda): general characteristics and parasitological significance of mites.

48. Arthropods (arthropoda): classification and morphofunctional characteristics of insects (insecta).

49. Arthropods (arthropoda): reproduction and development of insects. Direct development, development with incomplete transformation, development with complete transformation.

50. Arthropoda (arthropoda): parasitic insects. The development cycle of gastric and cutaneous gadflies.

51. Type Hemichordata: general characteristics using the example of Balanoglossus. The importance of hemichordates for elucidating the phylogeny of chordates.

52. Chordata: subclasses and classes of chordates, general characteristics and main characteristics of chordates.

53. Subtype Skullless (acrania). The structure of the lancelet.

54. Subtype Acrania: embryogenesis of the lancelet. Laying of the germ layers. Formation of the coelom. Layering of organ systems.

55. Subtype Tunicates, or Larval Chordates (tunicata, seu urochordata): structure of ascidians.

56. Superclass Pisces: classification and general characteristics. Differences between cartilaginous and bony fish.

57. Bony fishes (osteichthyes): morphofunctional and ecological characteristics. Main units.

58. Amphibians (amphibia): classification and morphofunctional characteristics. Phylogenesis.

59. Reptiles (reptilia): classification and general characteristics of organ systems.

60. Phylogeny of reptiles.

61. Birds (aves): classification and characteristics of organ systems.

62. Birds (aves): adaptations of birds to flight.

63. Birds (aves): structural features of the skeleton and muscles in connection with adaptation to flight.

64. Birds (aves): features of the respiratory system and breathing.

65. Birds (aves): embryonic and postembryonic development. The structure of the egg.

66. Birds (aves): phylogenetic development.

67. Mammals (mammalia): systematic classification. Main units.

68. Mammals (mammalia): integument, skeleton, muscles.

69. Mammals (mammalia): digestive system. Features of the digestive system of ruminant mammals.

70. Mammals (mammalia): circulatory system.

71. Mammals (mammalia): respiratory system. Respiration mechanism.

72. Mammals (mammalia): structure of the reproductive system and reproduction. Types of placentas and uteruses.

88. Veterinary and sanitary significance of roundworms.

89. Veterinary and sanitary significance of ticks.

90. Veterinary and sanitary significance of insects.

25. Flatworms (plathelminthes): classification and general structural and functional characteristics of the first three-layered animals.

Type flatworms - Plathelmintes

1 class Eyelash worms Turbelaria

1Squad Three-branched- Tricladida

Representative Milk planaria- Dendrocoeliumlaceatum

2Grade Monogenetic flukes - Monogenea

Before Frog polymouth- Polystomaintegerrimum

Carp fluke- Gyrodacilus

3Grade Digenetic flukes - Trematodes

1Squad Liver fluke- Fasciolahepatica

2Squad Lanceolate fluke- Dicrocoeliumlanceatum

3Squad Cat fluke- Opisthorchisfelineus

4th grade Tapeworms- Cestodes

1Squad tapeworms- Pseudophylidea

Representative Wide tape- Diphylobothriumlatum

2Squad Chain- Cyclophylidea

Before Armed (pork)tape- Taeniasuum

Unarmed (bull) tapeworm- Taeniarhynchus saginatus

Granular echinococcus- Echinococcusgranulosus

Sheep Brain- multicepsmulticeps

Characteristic;

1. External species: Type PLC are bilaterally symmetrical (bilateral) invertebrate animals. Flatworms have three layers. During the process of ontogenesis, 3 embryos are formed. leaf. Between the ectoderm, which forms the integument, and the endoderm, from which the intestines are built, there is also an intermediate layer - the mesoderm. Their body is elongated and flattened in the dorso-ventral direction.

2. An important feature of the structure of the PLC is the presence of a skin-muscular sac. The contraction of the muscle fibers of the musculocutaneous sac causes the characteristic “worm-like” movements of the PLC.

3. PLCs are cavityless, or parenchymatous, animals: pr-in between internal. organs are filled with connections. tissue (parenchyma). The edge serves as a place for the accumulation of reserve pits. thing-in, participates in the exchange of thing-in.

5. The nervous system (NS) consists of a paired cerebral ganglion and nerve trunks connected by ring bridges. Longitudinal lateral or abdominal trunks are developed. The PLC forms a central regulatory apparatus of the NS.

6. The circulatory and respiratory systems are absent.

7. Special excretory organs (for the first time) - a system of branched tubules, ending in the parenchyma with a special stellate cell with a bunch of cilia. With external The protonephridia communicate with the environment using special excretory openings.

8. Reproductive system: HPL - hermaphrodites; complex system of ducts for excretion of reproductive products + ! organs that enable internal fertilization.

26. Flatworms (plathelminthes): Flukes (trematoda). General characteristics.

Type Flatworms Plathelmintes

3Grade Digenetic flukes - Trematodes

1Squad Liver fluke- Fasciolahepatica

2Squad Lanceolate fluke- Dicrocoeliumlanceatum

3Squad Cat fluke- Opisthorchisfelineus

1)External structure: The body is leaf-shaped, flattened in the dorso-ventral direction. There are 2 suckers: 1) oral - at the front end of the body, mouth. hole at the bottom. 2) abdominal - located on the ventral side of the body.

2) Covers: are represented by a typical tegument: a continuous outer syncytial plate is connected by cytoplasmic bridges with submerged nuclear-containing parts - cytons. In the cytoplasm there is syncytosis. the plates contain actin spines. Superficial structures (microvilli and microtrichia) are absent. There is no parenchyma in trematodes.

3) Nervous system: There are 3 pairs of longitudinal trunks (dorsal, lateral and ventral), which are connected by transverse ligaments. The abdominal ones are the most developed. At the anterior end there is a trapezoidal ganglion. Nerves move forward from him. endings innervating the muscles of the oral sucker and sensory organs. A system of nerve trunks, forming a plexus, also extends from the ventral trunks to the ventral sucker. 4) Excretory system: Unlike other PLCs, there is a bladder. There are 2 main collecting channels from the bladder to the anterior end of the body. Main function: osmoregulation. The excretory function of trematodes is carried out by the integument of the body.

6) Digestive system: Closed. Mouth. the hole is located at the anterior end of the body at the bottom of the mouth. suckers leading into the pharynx. Next is the esophagus, which in front of the abdominal sucker is divided into two blindly closed branches of the intestine.

7) Reproductive system: Most trematodes appear. hermaphrodites. However, among trematodes there are also dioecious ones: in the families Schistosomatidae and Didymozoidae.

1. Women part of the reproductive system: one ovary (rarely secondarily segmented). An oviduct with many valves extends from it. In the wall of the oviduct there is a growth - the spermatheca (serves for storing sperm). The vitelline duct flows into the oviduct. The Laurer canal also extends from the oviduct, which opens with an opening on the ventral or dorsal side of the body. Its function: removal of excess yolk cells and sperm from the oviduct. After the confluence of the Laur. The oviduct canal forms an oval chamber - ootype.

2.Men part of the reproductive system: 2 testes, which can subsequently fragment. (except for the family Monorchidae). The vas deferens extend from the testes, extending forward to the ventral sucker and uniting into the vas deferens. There are 2 swellings on the vas deferens - seminal vesicles. Then the vas deferens flows into the bursa of the cirrus, the copulatory organ.

8) Social organization in trematodes: Individual worms in the host's body differ from each other in appearance. appearance and behavior. Some are sedentary and clone hundreds of their own kind every day, while others protect the colony from enemy invaders.

Table of contents of the topic "Animal Kingdom. Worms.":

Systematics and characteristic signs of the Platyhelminthes type are given in the table.

Three-layer structure flatworms is due to the appearance of the third germ layer in the embryo - the mesoderm, which is located between the ecto- and endoderm (Fig. 2.55, A). The presence of mesoderm is important in several respects.

1. With a three-layer structure body size may increase, as a result of which the digestive tract becomes distant from the walls of the animal’s body.

2. From mesoderm Various organs are formed, the coordinated work of which leads to a higher level of organization - to the development of organ systems. Examples of such systems include the central nervous system, digestive, excretory and reproductive systems.

3. In three-layered animals muscle work becomes much more perfect. The need for this is associated with an increase in the size of the animal, since cilia and flagella can no longer provide locomotor functions.

However, with an increase animal size The problem of transport of substances between the endodermal and ectodermal layers arises. In some animals, the mesoderm completely fills the space between the endoderm and ectoderm (acelomic animals). In this case, transport problems are solved by flattening the body, ensuring the preservation of a large surface area compared to its volume. As a result, simple diffusion is sufficient to maintain the required level of metabolism between the environment and the tissues of the animal. In other animals, in the mesoderm of which a cavity develops - the coelom (coelomic animals), transport systems have arisen that ensure the transfer of substances from one part of the body to another.

Flatworms have a three-layer body. This is the earliest group of animals in which organ systems formed from mesoderm first appeared. Flatworms are acoelomic animals and, as a result, their body is flat, which is why they got their name. The bulk of the mesoderm in the body remains undifferentiated and forms the lining tissue - mesenchyme, which performs supporting and protective functions for the internal organs.

In flatworms there is no special transport system, since in accordance with the general structural plan, all parts of their body are located close to sources of food and oxygen. The body of all representatives of this type is flat and thin, so the ratio of the surface area of ​​the body through which gas exchange occurs to the volume is quite high. Many forms have a highly branched gut, which facilitates the absorption of nutrients. In addition, they have a system of branching excretory tubes that collect metabolic end products to be excreted.