Types of eyelash worms. Class ciliated worms

All worms can be divided into three types (flat, annelid, round), each of which has its own characteristic features. This type refers to invertebrate animals that lack a body cavity and have bilateral symmetry.

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The main signs of the type of flatworms

  • digestive;
  • nervous;
  • sexual;
  • excretory

This type has several systems and even the rudiments of organs

Circulatory system

Not present, but the function of blood is performed by the parenchyma, consisting of connective cells. It is she who transports nutrients in the body.

Digestive system

Quite simplified, consists of the pharynx and intestines.

The pharynx is powerful and can:

  • suck in;
  • twist and envelop its victim.

The intestine consists of two sections - anterior and middle, most often branched. It has a closed structure, so that all undigested waste exits through the mouth. The mouth opening is located closer to the middle of the worm's body.

Free worms are mostly predators and they even have a peculiar device for capturing prey. This system is not observed in all classes; more primitive worms do not have it. For example, tapeworms feed on the entire surface.

Excretory system

The excretory system is quite large and consists of many tubules that unite and lead to excretory pores.

The parenchyma contains special cells that drive harmful substances into the tubules. For humans, these excretory products are very dangerous and toxic, along with poison.

This class includes free-living marine and freshwater, rarely terrestrial worms, the entire body of which is covered with ciliated epithelium. The movement of worms is ensured by the work of cilia and muscle contraction. Many species are characterized by regeneration.

A typical representative of eyelash worms -milky white palan aria- lives in fresh standing water bodies on underwater objects and plants (Fig. 11.4). Its flat body is elongated; at its anterior end two small tactile tentacle-like outgrowths and two eyes are visible.

Planaria is a predatory animal. Her mouth is located on the ventral side, almost in the middle of the body. With the help of a muscular pharynx protruding outwards, the planaria penetrates the prey and sucks out its contents.

In the branching middle section of the intestine, food is digested and absorbed. Excretory organs

- protonephridia. They are represented by two branching canals, at one end with excretory openings opening outwards, and at the other - stellate cells scattered in the parenchyma.

The stellate part of the cell passes into a canal, inside of which there is a bunch of cilia. Liquid metabolic products leak into the pear-shaped expansion of the initial section of the canal. Protonephridia are located on the sides of the body.

    General characteristics of the type The characteristic features of the type are as follows: Body

    flat, its shape is leaf-shaped (in ciliated and flukes) or ribbon-shaped (in tapeworms). For the first time in the animal world, representatives of this type developed

    bilateral (bilateral) symmetry of the body, that is, only one longitudinal plane of symmetry can be drawn through the body, dividing it into two mirror-like parts. In addition to the ectoderm and endoderm, they also have a middle germ layer - mesoderm. That's why they are considered the first

    three-layer animals. The presence of three germ layers provides the basis for the development of various organ systems. The body wall is formed

    knee-muscle bag - a combination of outer single-layer epithelium and several layers of muscles located underneath it - annular, longitudinal, oblique and dorso-abdominal. Therefore, the body of flatworms is capable of performing complex and varied movements. Body cavity absent,

    since the space between the body wall and the internal organs is filled with a loose mass of cells - parenchyma. It performs a supporting function and serves as a depot of reserve nutrients. The digestive system consists of two sections: ectodermal foregut,

    represented by a mouth and a muscular pharynx, capable of turning outwards in predatory ciliated worms, penetrating inside the victim and sucking out its contents, and a blindly closed endodermal midgut. Excess water and metabolic end products (mainly urea) are removed through the excretory pores.

    The nervous system is more concentrated and represented in pairs cephalic ganglion and extending from it longitudinally nerve trunks, connected by ring jumpers. Nerve trunks are formed by the bodies of nerve cells and their processes located along its entire length. This type of organization of the nervous system is called stem

All flatworms have developed organs of touch, chemical sense, balance, and in free-living ones - vision. Appearance and covers.


The body of ciliated worms is elongated and leaf-shaped. Dimensions vary from a few millimeters to several centimeters. The body is colorless or white. Most often, eyelash worms are colored in different colors by grains of pigment located in the skin. The body is covered with single-layer ciliated epithelium. The integument contains skin glands scattered throughout the body or collected in complexes. Of interest are the types of skin glands - rhabditis cells

, in which there are light-refracting rabdita rods. They lie perpendicular to the surface of the body. When an animal is irritated, the rhabdites are thrown out and swell greatly. As a result, mucus forms on the surface of the worm, possibly playing a protective role. Skin-muscle bag.
Beneath the epithelium is a basement membrane that serves to give the body a certain shape and to attach muscles. The combination of muscles and epithelium forms a single complex - a skin-muscle bag. The muscular system consists of several layers of smooth muscle fibers. The most superficial are the circular muscles, somewhat deeper are the longitudinal and the deepest are the diagonal muscle fibers. In addition to the listed types of muscle fibers, ciliated worms are characterized by dorsal-abdominal, or dorsoventral

, muscles. These are bundles of fibers running from the dorsal side of the body to the ventral side. The movement is carried out due to the beating of the cilia (in small forms) or the contraction of the skin-muscular sac (in large representatives). Ciliated worms do not have a clearly defined body cavity. All spaces between organs are filled parenchyma


- loose connective tissue. The small spaces between the parenchyma cells are filled with aqueous fluid, which allows the transfer of products from the intestines to the internal organs and the transfer of metabolic products to the excretory system. In addition, parenchyma can be considered as supporting tissue. ciliated worms are blind-closed. The mouth serves both for swallowing food and for throwing away undigested food debris. The mouth is usually located on the ventral side of the body and leads into the pharynx. In some large ciliated worms, such as the freshwater planaria, the mouth opening opens into a pharyngeal pouch, which contains a muscular pharynx that can stretch and protrude through the mouth. The midgut in small forms of ciliated worms consists of canals branching in all directions, and in large forms the intestine is represented by three branches: one anterior, going to the anterior end of the body, and two posterior, going on the sides to the posterior end of the body.Some ciliated worms lack an intestine, and food entering through the mouth enters a loose mass of parenchyma cells, which absorb and digest it. In forms that have an intestine, food is digested both in its lumen and by the cells of the walls, which capture pieces of food. Consequently, ciliated worms are characterized by both extracellular and intracellular digestion. there are special cells - phagocytes, capable of capturing and digesting various microorganisms that have entered their body


Main feature nervous system ciliated worms in comparison with coelenterates is the concentration of nerve elements at the anterior end of the body with the formation of a double node - the cerebral ganglion, which becomes the coordinating center of the whole body. Longitudinal nerve trunks, connected by transverse annular bridges, extend from the ganglion.The sense organs of ciliated worms are relatively well developed. The entire skin serves as an organ of touch. In some species, the function of touch is performed by small paired tentacles at the anterior end of the body. The balance sense organs are represented by closed sacs - statocysts, with auditory pebbles inside. The organs of vision are almost always present. There may be one pair of eyes or more.

Excretory system appears for the first time as a separate system. It is represented by two or several channels, each of which opens outward at one end, and the other strongly branches, forming a network of channels of various diameters. The thinnest tubules or capillaries at their ends are closed by special cells - stellate. From these cells, bundles of cilia extend into the lumen of the tubules. Thanks to their constant work, there is no stagnation of fluid in the body of the worm; it enters the tubules and is subsequently excreted. The excretory system in the form of branched canals closed at the ends by stellate cells is called protonephridia.

Reproductive system quite diverse in structure. It can be noted that, compared to coelenterates, ciliated worms have special excretory ducts for removing germ cells out. Ciliated worms are hermaphrodites. but self-fertilization is eliminated by the maturation of eggs and sperm at different times. Fertilization is internal.Reproduction is in most cases sexual. In most worms, development is direct, but in some marine species development occurs with metamorphosis. However, some eyelash worms can also reproduce asexually through transverse fission. At the same time, regeneration of missing organs occurs in each half of the body.

A typical representative of eyelash worms is milky white planaria- lives in fresh standing reservoirs on underwater objects and plants. Its flat body is elongated, at the front end two small tactile tentacle-like outgrowths and two eyes are visible.
The class Ciliated worms is divided into the following orders:

  1. Order Intestinal Turbellaria (Acoela)
  2. Order Catenulida
  3. Order Macrostomida
  4. Order Polycladida
  5. Order Proseriata
  6. Order Trigladida
  7. Order Rectal turbellaria (Rhabdocoel

The structure of the skin-muscle sac of ciliated worms.

Prevention.

Diagnostics

1.Personal. Compliance with personal hygiene rules.

2. Public. Sanitary arrangement of public places, monitoring of public water supply sources, sanitary educational work with the population, rodent control, hygienic keeping of pigs.

Skin-muscle bag . Under the epithelium is basement membrane, which serves to give the body a certain shape and to attach muscles. The combination of muscles and epithelium forms a single complex - skin-muscle sac. The muscular system consists of several layers smooth muscle fibers. Most superficially located circular muscles, somewhat deeper - longitudinal and the deepest - diagonal muscle fibers. In addition to the listed types of muscle fibers, ciliary worms are characterized by dorso-abdominal, or The combination of muscles and epithelium forms a single complex - a skin-muscle bag. The muscular system consists of several layers of smooth muscle fibers. The most superficial are the circular muscles, somewhat deeper are the longitudinal and the deepest are the diagonal muscle fibers. In addition to the listed types of muscle fibers, ciliated worms are characterized by dorsal-abdominal, or, muscles. These are bundles of fibers running from the dorsal side of the body to the ventral side.

The movement is carried out due to the beating of the cilia (in small forms) or the contraction of the skin-muscular sac (in large representatives).

Clearly expressed body cavities ciliated worms do not. All spaces between organs are filled Ciliated worms do not have a clearly defined body cavity. All spaces between organs are filled- loose connective tissue. The small spaces between the parenchyma cells are filled with aqueous fluid, which allows the transfer of products from the intestines to the internal organs and the transfer of metabolic products to the excretory system. In addition, parenchyma can be considered as supporting tissue.

The muscular part of the skin-muscle bag is formed by several layers of muscle fibers. On the outside there is a ring layer, underneath it is a longitudinal layer and the lowest layer is diagonal, the fibers of which run at an angle to each other. It is the combination of the integument and underlying layers of muscle fibers that forms the skin-muscle sac.

- loose connective tissue. The small spaces between the parenchyma cells are filled with aqueous fluid, which allows the transfer of products from the intestines to the internal organs and the transfer of metabolic products to the excretory system. In addition, parenchyma can be considered as supporting tissue. eyelash worms blind. Mouth also serves for swallowing food, and for throwing out undigested food debris. The mouth is usually located on the ventral side of the body and leads into throat. In some large ciliated worms, such as the freshwater planaria, the mouth opening opens into pharyngeal pocket, in which it is located muscular throat, capable of stretching and protruding out through the mouth. Midgut in small forms of ciliated worms it is canals branching in all directions, and in large forms the intestine is represented three branches: one front, going to the anterior end of the body, and two rear, running along the sides to the rear end of the body.



Most turbellaria are predators, feeding on a variety of small animals. The digestive system consists of the foregut and midgut, which closes blindly. The mouth not only serves to swallow food, but also to expel undigested solids. The mouth is usually placed on the ventral side of the body: at a short distance from the anterior end of the body, in the middle of the ventral side, or closer to the posterior pole. The mouth leads into the ectodermal pharynx, which in turn passes into the midgut. In some large turbellarians (in freshwater planarians of the order Tricladida and in marine turbellarians of the order Polycladida), the mouth opening does not open into the pharynx, but into a special deep invagination of the outer integument, called the pharyngeal pouch (Fig. 124, Fig. 135). From the bottom of the pocket a muscular pharynx protrudes into its cavity. It looks like a tube that can be strongly stretched and protruded out through the mouth, serving to capture prey.

The endodermal midgut is structured differently in many forms of Turbellaria. In small turbellarians (orders Rhabdocoela, Macrostomida, etc.) it has the form of a simple bag or a blindly closed tube (Fig. 134). In large forms, the intestine is usually branched. Thus, in polycladida, the pharynx leads to the stomach, from which branching canals, blindly closed at the ends, extend in all directions to the edges of the body (Fig. 135). In three-branched animals (Tricladida), three main branches of the intestine depart from the pharynx, located near the middle of the body (Fig. 123, Fig. 124): one goes straight forward, the other two bend and go backward along the sides of the pharynx; each of the branches produces side blind branches.

This intestinal structure is not accidental. In small turbellaria, the size of which does not exceed a few millimeters, digestive products are easily distributed throughout the body through loose parenchymal tissue. In large tricladids and polycladids, sometimes reaching 1-3 and even 30 cm, this process is extremely difficult. In such turbellaria, the function of distributing digestive products throughout the animal’s body is performed by intestinal branches that penetrate the parenchyma in all directions and are in direct contact with all tissues and organs.

In the process of digesting food in turbellarians, as well as in coelenterates, intracellular digestion occupies a large place. Food particles, previously processed by the secretion of the pharyngeal glands, enter the intestine and are captured by intestinal epithelial cells, in which numerous digestive vacuoles are formed. In the order of intestinal turbellarians, a pronounced midgut is completely absent (Fig. 126). Their pharynx protrudes into a somewhat separate area of ​​parenchyma (digestive parenchyma), in which intracellular digestion of food occurs

The digestive system of ciliated worms is quite diverse within the class and varies from primitive - without a formed intestine to relatively complex - with a branched intestine. The main orders of ciliated worms differ primarily in the shape of their intestines.

Multi-branched turbellarians - polyclades (order Polycladida) have a rather complex intestine. Their mouth opening, as a rule, is closer to the posterior end of the body and leads into a folded pharynx, from which many blind branches of the endodermal intestine diverge radially.

In the suborder three-branched, or planarians, there is a triclad ( Tricladida) three branches of the intestine extend from the pharynx, located in the middle of the body. One branch is directed towards the anterior end of the body, and two - backward. In this case, food first enters the front growth, and from there flows to the rear. Thus, nutrients are initially provided to the organs located in the front of the body.

In the order Rhabdocoela, the pharynx is located at the anterior end of the body and the intestine is straight and unbranched.

In ciliated worms with formed intestines, the pharyngeal glands play a large role in the digestion of food. Many species exhibit extraintestinal digestion. Planarians often attack fairly large prey (mollusks, crustaceans). They secrete digestive enzymes into the victim's body and then absorb semi-digested food.

Despite the certain complexity of the digestive system, food absorption in turbellarians is largely carried out due to intracellular digestion, that is, phagocytosis of epithelial cells of the midgut.

Most turbellarians are predators and feed on a variety of small invertebrates. Having discovered the victim, the worm covers it with its body and then swallows it. In planarians, this is accomplished by a retractable pharynx, which is ejected from a deep invagination of the outer integument - the pharyngeal pouch. If the size of the prey is too large and it cannot be swallowed whole, the worm tears off pieces with strong sucking movements of the pharynx, after which it swallows them. However, small arthropods (for example, crustaceans) are covered with a hard shell and planaria cannot tear them apart. In this case, it secretes digestive enzymes from the pharynx, which break down the tissues of the victim outside the worm’s body, after which the softened food is absorbed through the pharynx. Thus, external digestion is also possible in turbellarians. Some turbellarians (planarians) have a peculiar ability to use “captured weapons”. Scientists have found that when hydra are eaten by planaria, the stinging cells are not destroyed, but migrate into the integument of the worm and protect it.

Ciliated worms (from the Latin turbellaria or turbellaria) are a class of worms that zoologists classify as flatworms. The total number of all representatives of this class varies within 3.5 thousand individuals, of which the vast majority are free living creatures A.

Peculiarities

The body of turbellarians is covered ciliated epithelium. Thanks to the work of the cilia and the contraction of the muscular part of the body, the turbellaria moves in space by crawling or swimming.

Many turbellarian species have shown amazing regenerative abilities.

She especially stood out in this skill. planaria- an inhabitant of reservoirs and one of the large typical representatives of the class of ciliated worms. This turbellaria from the order of three-branched animals can fully recover and form into a full-fledged worm, even if only 0.01 parts of its body remain.

Under unfavorable conditions for life, the planaria spontaneously disintegrates into tiny pieces in order to subsequently come to life in a more pleasant environment for existence.

The sizes of individuals range from tiny and invisible to quite impressive sizes - 30-40 cm.

Classification of eyelash worms

The new, thoroughly revised and complicated classification of turbellarians currently includes 12 squads. If earlier turbellarians were divided into 4 orders, based only on the difference in the structure of the intestinal system, now the distinctive features are: types of eggs and methods of crushing, the structure of the reproductive and excretory systems, etc.

Experts identify several main groups, which are considered the main ones:

  1. Order Intestinal (Acoela)- tiny and predominantly marine inhabitants with a primitive form of body structure: no intestine (it is replaced by digestive parenchyma), no excretory organs typical of other representatives of lower invertebrates, a primitive structure of the genital organs, etc. There is a statocyst - an organ for the sense of balance.
  2. Order Macrostomida- primitive small worms. They live in sea and fresh water. The intestines are saccular. The reproductive system is primitive - there are no separate vitelline sacs. Individual representatives reproduce by transverse division.
  3. Gnathostomulida- small turbellarians that live in the sands of sea coasts. The intestines are saccular. The throat contains a pair of chitinous jaws. A characteristic feature is that instead of cilia they have flagella that originate from each epithelial cell.
  4. Multibranched (Polyclaida)– large (up to 15 cm) marine inhabitants with a leaf-shaped body. The intestine is branched, there are multiple gonads. Primitive features - there are no separate zheltochniks, and in some representatives there are no sexual tributaries, etc.
  5. Three-branched or planarians (Tricladida)– freshwater individuals with a leaf-like and ribbon-like body structure. The reproductive system is developed, there are numerous testes, a pair of ovaries and vitelline sacs. Three-branched structure of the midgut.
  6. Rectum (Rhabdocoela, or Neorhabdocoela)– small animals: from 0.5 to 5 mm. The body is almost not flattened, almost cylindrical. They swim in water with the help of cilia. A characteristic feature is a straight and blindly closed intestine. The mouth is on the front of the body. There are sensory organs - a pair of eyes. The excretory system consists of a pair of canals with two openings.
  7. Temnocephalida- worms several millimeters in length with an elongated body. They have tentacles and suckers with glands. The epithelium is devoid of cilia.

Structure and physiology

Representatives of turbellarians are characterized by common structural features, such as an elongated leaf- or ribbon-shaped body, often without additional appendages. Only rare individuals can have tentacle-like outgrowths. Eyelash worms are distinguished by a variety of spotted colors and rarely are individuals colorless or of one solid color.

A characteristic feature of ciliated worms, which gave the name to this class, is special structure of the ciliated epithelium in the form of highly located cylindrical cells, on the edges of which cilia are located. The beating of the cilia ensures the movement of the turbellaria in space, as does the contraction of the skin-muscle sac.

All internal organs that exist in one or another representative of ciliated worms are connected by loose tissue - Ciliated worms do not have a clearly defined body cavity. All spaces between organs are filled. It plays the role of an intermediary in the digestive system and transfers from one organ to another the products of digestion in the intestines and metabolic products to the excretory system. Experts also consider parenchyma as connective tissue

The skin often contains many glands that secrete fluids of different composition and properties. Often these are toxic substances that play a protective role.

Digestive system and nutrition

Between individual representatives of the orders of ciliated worms, there are fundamental differences in the structure of their digestive system. There are types of worms with a very primitive mechanism for digesting food - intestinal.

  1. Temnocephals.
  2. Udonellid.

Primitive turbellarians digest food in special digestive cells or parenchyma.

Individuals with a more evolutionarily developed digestive system are divided into species:

  • Branches.
  • Rectal.

Nervous system, sensory organs and breathing

The typical structure of the nervous system for representatives of the turbullar class is the cerebral ganglion and the nerve trunks branching from it. Nerve endings are concentrated mainly at the front of the body, forming a kind of double knot - ganglion. This primitive brain of invertebrate ciliated worms functions as a nerve center.

Some primitive representatives of turbullarians have a simply structured nervous system, which consists only of a plexus of a small number of nerve endings located close to the surface of the body. And others may have more neurons, more thickened and sensitive to external stimuli.

Sense organs are well developed. Turbellaria use the entire surface of their skin to sense touch. Touch with the help of eyelashes. Some worms have a statocyst organ, an organ for the sense of balance. Almost all worms have eyes.

Turbellarians do not have separately formed respiratory organs. The entire surface of their skin has the ability to absorb oxygen contained in water. It is the ability to respire by absorbing oxygen over the entire surface of the body that distinguishes free-living ciliated worms from other flatworms, most of which are anaerobes. Which means they can exist in an environment without oxygen. Breathing is an important part of existence for eyelash worms.

Reproduction and sexual characteristics

Turbellaria are mostly hermaphrodites, i.e. have both male and female genital organs. Mating occurs crosswise and both worms fertilize each other as males, and then become fertilized as females.

After successful mating, an egg is formed, from which a larva emerges, resembling an adult in appearance. Some species are capable of reproducing by dividing in half, after which a separate full-fledged individual is formed from each part.

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