Breathing of flatworms. Type Flatworms. Class ciliated worms. Fluke class. Class tapeworms

According to the shape of the body, worms are divided into three types: Flat, Round and Ringed. All worms are three-layered animals. Their tissues and organs develop from three germ layers - ectoderm, endoderm and mesoderm.

Type Flatworms their characteristics

Type Flatworms unites about 12,500 species. In their organization, they are higher than coelenterates, but among the three-layer animals they are the most primitive. These animals can crawl slowly. Most characteristic feature flatworms - a flattened (flattened) body, in the form of a long ribbon.

The figure below shows the structure of the Flatworm using the Planaria as an example.

Structure	The body is flattened in the dorsal-abdominal direction, the space between the organs is filled with a special tissue - parenchyma (there is no body cavity)
Body covers	Musculocutaneous sac (skin fused with muscular fibers)
Nervous system	Two nerve trunks connected by nerves ("ladders")
Sense organs	Eyes in front of the body, tactile cells scattered throughout the body
	The digestive system is blindly closed; eat mouth -> pharynx -> branched intestines
	The entire surface of the body
Highlighting	System of tubules opening outward on the sides of the body
Reproduction	Hermaphrodites; sperm mature in the testes, eggs in the ovaries; the female lays eggs, from which young worms emerge

Variety of Flatworms, their main classes

Type Roundworms and their characteristics

Type Roundworms- a large group of animals with a long, round body in cross section, which is pointed at the front and rear ends. Roundworms are characterized by the presence of free space inside the body - the primary cavity. It contains internal organs surrounded by cavity fluid. Washing the cells of the body, it participates in gas exchange and transport of substances. The body of the roundworms is covered with a strong shell - the cuticle. This group includes about 20 thousand species.

The figure below shows the structure of the Round Worm using the Ascaris as an example.

Structure	Elongated cylindrical body, pointed at both ends, round in cross section, there is a body cavity
	Musculocutaneous sac
Nervous system	Abdominal nerve cord
	Mouth (3 hard lips) -> pharynx -> intestinal tube -> anus
	The entire surface of the body
Highlighting	Through the surface of the body
Reproduction	Most are dioecious; the female lays eggs, from which young worms emerge
Representatives

Type annelid worms their characteristics

Type Ringworms- a group of animals whose representatives have a body divided into segments, resembling rings folded one after another. There are about 9 thousand species of annelids. Between the skin-muscle bag and the internal organs, they have the whole- a secondary body cavity filled with fluid.

Structure	The body consists of segments, there is a body cavity
	Leather; muscles - longitudinal and circular
Nervous system	The supraopharyngeal and subopharyngeal ganglia and the abdominal nerve cord, from which nerves branch off in each segment
	Mouth -> pharynx -> esophagus -> goiter -> stomach -> intestine -> anus
	The entire surface of the body; the sea has special outgrowths of the body - gills
Highlighting	Each segment has a pair of tubules opening outward by excretory pores
Reproduction	Hermaphrodite; the female lays eggs in a cocoon, from which young worms appear
Manifold	1. Class Small setae - live mainly in soil and fresh water bodies, have small bristles on each segment (representative - earthworm) 2. Class Polycheetinovye - live in the seas; have paired outgrowths with bristles on the sides of the body (a representative is a nereid, sandworm)

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Sourse of information: Biology in tables and diagrams. / Edition 2e, - SPb .: 2004.

Flatworms are simple, segmented, soft-bodied, invertebrates, bilaterally symmetric, which have no space between organs (body cavities). In this group of worms, there are up to 25,000 thousand species. More than 3000 flatworms are found in Russia. They mainly infect the organisms of humans and mammals, but there are also free-living species.

A distinctive feature of representatives of the flatworm type is a three-layer structure (internal (endoderm), external (ectoderm) and middle (mesoderm) layers), acquired in the process of evolution, as well as bilateral symmetry, differentiated tissues and organs.

Seven classes fall under the type of flatworms:

Aspidogastry;
Cestode-like;
Monogeneans;
Ciliary;
Tape;
Gyrocotilides.

In appearance, worms of this class have a long, flat body with suction cups on the front of the torso for attachment.

Ciliary individuals have well-developed sense organs, muscles, and have cilia for movement.

The body is represented by a leaf-like shape.

A feature of the structure is an organ - a rosette, which serves for attachment.

The main reasons for the increase in cases of invasion

In developed countries

In less developed countries

Many poor countries are vigorously taking all possible measures to combat unintentional invasions, while in developed countries cases of targeted self-infection with flatworms are recorded by people who follow a diet to quickly lose body weight

Pests

Northwest Europe, not excluding the British Isles, is concerned about the existing threat of the spread of planaria from New Zealand and the Australian worm Australoplana SANGUINEA. The triangulatus worms are believed to have entered Europe with plants brought in containers from botanical gardens.

Human use of planaria

The Philippines, Indonesia, Hawaii, New Guinea and Guam have successfully introduced two species of planaria, thereby controlling the growth of the African snail from the Achatina gigantea species. Spreading planaria has been effective or not, but the number of unwanted snails has been significantly reduced. In this regard, it is believed that this method is more effective than other biological methods. But it is possible that planarians can subsequently bring a serious threat to their native snails.

Free-living species

The digestive system consists of the mouth, pharynx, and cecum.

Both food intake and waste disposal are carried out through the mouth, which is located on the ventral side of the front of the body.

Tapeworms have no digestive system.

Nervous system

Consists of cerebral ganglia, nerve trunks and nerves.
Nerves radiate from the trunks and the ganglion, which cover all tissues and organs of the worm.

Excretory system

Branching tubules serve for construction, at their ends are cells in the form of stars, which are immersed in the parenchyma. They are called fiery or flickering. These tubules serve the worms to transfer the trapped liquid waste from the parenchyma to the tubules along the cilia. The tubules come out to the surface of the worm, where they end in pores, through them waste from the body is thrown out.

Reproductive system

Most flatworms are hermaphrodites. The organs of the reproductive system consist of the ovaries and testes (at the same time in one organism).

Sperm are contained in the semen produced by the testes - the male sex glands.

The fertilization process is cross-cutting, which means that different individuals can exchange seminal fluid.

The musculocutaneous sac includes organs: muscles and epithelium.

The epithelium has only one layer of cells. The surface can be covered with cilia, microvilli, or chitinous hooks. Representatives of the ciliate worms class have cilia. Tapeworms, cestodes, and other worms have microvilli and hooks.

Muscles are immediately located under the integumentary tissue, which are subdivided into diagonal, longitudinal and circular. The body of the worms is equipped with bundles of dorsal-abdominal muscles. Such worms can stretch, shrink, contract, bend, twist, contract, thanks to the variety of muscles.

The senses are made up of tentacles that react to chemicals, light-sensitive pigment eyes, tactile cells located on the surface of the skin, and the organ of balance.

Organs respiratory system absent.

The circulatory system is absent.

Classification of flatworms for recent times has undergone significant changes caused by the study of these individuals. Now the group of flatworms has 4 different classes.

Ciliary worms. The most primitive species of tapeworms and the only free-living species. In its size, it can reach a length of up to half a meter.

Flukes or - helminths living in various human organs, mainly in the liver, lungs and intestines.

Food and movement

Structure

The complex structure of the worm's muscles allows it to stretch and contract in size, as well as move and twist. The entire body of flatworms is filled with cells that form a loose mass. This connection of cells is called parenchyma. It is here that the excretory system, digestive organs and genitals are located. The excretory system has protonephridia, which remove all unprocessed food from the body. Excretion can pass through cells or through excretory tubules.

Although digestion occurs in all classes, the organ system is present in only a few members. Other species receive food through the integument of the body, so the system itself may be absent. The digestive system has a blind ending.

Not all types of these worms have sense organs. In free-living representatives, the sense organs are represented by vision. Like other primary cavity organisms, the circulatory system in tapeworm flatworms is absent. Also, flatworms lack sexual separation, all representatives are hermaphrodites. The development of helminths proceeds in a direct way.

Initial level of knowledge:

Response plan:

General characteristics of flatworms
External and internal structure Flatworms
Breeding Flatworms
Classification of Flatworms, variety of species
Features of the structure and development of worms of the Ciliary class on the example of Milk planaria
Features of the structure and development of worms of the Fluke class on the example of the Liver fluke
Features of the structure and development of worms of the tape class on the example of the Bull tapeworm, etc.

General characteristics of flatworms

Number of species: about 25 thousand.

Habitat: They live everywhere in humid environments, including tissues and organs of other animals.

Structure: Flatworms are the first multicellular animals in which, in the course of evolution, bilateral symmetry, three-layer structure, real organs and tissues appeared.

Bilateral(bilateral) symmetry - this means that an imaginary axis of symmetry can be drawn through the animal's body, while the right side of the body will be mirror-like to the left.

During embryonic development in three-layer animals are laid three layers of cells: outer - ectoderm, average - mesoderm, internal - endoderm... Certain organs and tissues develop from each layer:

the skin (epithelium) and the nervous system are formed from the ectoderm;

from the mesoderm - muscle and connective tissue, reproductive, excretory system;

from the endoderm - the digestive system.

In flatworms, the body is flattened in the dorsal-abdominal direction, the body cavity is absent, the space between the internal organs is filled with mesoderm cells (parenchyma).

Digestive system includes the mouth, pharynx and blind intestine. The absorption of food and the excretion of undigested residues occurs through the mouth. In tapeworms, the digestive system is completely absent, nutrients they are absorbed by the entire surface of the body, being in the intestine of the host.

Excretory organs - protonephridia... They consist of thin branching tubules, at one end of which there are fiery (ciliated) cells stellate, immersed in the parenchyma. A bundle of cilia (flickering flame) leaves inside these cells, the movement of which resembles a flickering flame (hence the name of the cells). Flame cells capture liquid decay products from the parenchyma, and the cilia drive them into the tubule. The tubules open on the surface of the body by an excretory pore through which waste products are removed from the body.

Nervous system ladder type ( orthogon)... It is formed by a large head paired nerve node (ganglion) and six nerve trunks extending from it: two on the ventral side, two on the dorsal and two on the sides. The nerve trunks are interconnected by jumpers. Nerves extend from the ganglion and trunks to organs and skin.

Reproduction and development:

Flatworms are hermaphrodites. Sex cells mature in the sex glands (gonads). Hermaphrodite has both male glands - testes, and female - ovaries. Fertilization is internal, usually cross-fertilization, i.e. worms exchange seminal fluid.

CLASS CILIA WORM

Milk planaria, a small aquatic animal, an adult is ~ 25 mm long and ~ 6 mm wide, the body is flat, milky white. At the front end of the body are two eyes that distinguish light from darkness, as well as a pair of tentacles (chemical sense organs) needed to search for food. Planarians move, on the one hand, thanks to the work of the cilia covering their skin, on the other hand, thanks to the contraction of the muscles of the skin-muscular sac. The space between the muscles and internal organs is filled with parenchyma, in which they meet intermediate cells responsible for regeneration and asexual reproduction.

Planarians are predators that feed on small animals. The mouth is located on the ventral side, closer to the middle of the body, from it there is a muscular pharynx, from which three branches of the closed intestine depart. Capturing the victim, the planaria sucks out its contents by throat. In the intestine, digestion occurs under the action of enzymes (intestinal), intestinal cells are able to capture and digest pieces of food (intracellular digestion). Undigested food debris is removed by mouth.

Reproduction and development... Ciliates are hermaphrodites. Fertilization is cross. Fertilized eggs fall into a cocoon, which the worm lays on underwater objects. Direct development.

PUCKER CLASS

TAPE CLASS

Bovine tapeworm- tapeworm, reaches a length of 4 to 12 meters. The body includes a head with suction cups, a neck and a strobila - a tape of segments. The youngest segments are at the neck, the oldest are sacs filled with eggs, located at the posterior end, where they come off one by one.

Reproduction and development... The bovine tapeworm is hermaphrodite: in each of its segments there is one ovary and many testes. Both cross fertilization and self-fertilization are observed. The posterior segments, filled with mature eggs, open and, with feces, are removed. Large cattle(intermediate host) can swallow eggs along with the grass; in the stomach, microscopic larvae with six hooks emerge from the eggs, which enter the bloodstream through the intestinal wall and are carried throughout the animal's body and are carried into the muscles. Here the six-haired larva grows and turns into finnu- a bubble, inside which there is a chain head with a neck. A person can become infected with Finns by eating insufficiently cooked or cooked meat from an infected animal. In the human stomach, a head comes out of the fin, which attaches to the intestinal wall. New segments bud off from the neck - the worm grows. Bovine tapeworm releases toxic substances that cause intestinal disorders and anemia in humans.

Development pork tapeworm has a similar character, its intermediate owner, in addition to a pig and a wild boar, can also be a person, then finns develop in his muscles.

Development wide tape is accompanied by a change of two intermediate hosts: the first is a crustacean (cyclops), the second is a fish that ate the crustacean. The ultimate host can be a human or a predator who ate the infected fish.

New concepts and terms: mesoderm, musculocutaneous sac, tegument, hypodermis, reduction, protonephridia (flame cells), orthogon, strobila, ganglion, gonads, hermaphrodite, direct and indirect development, final and intermediate host, miracidium, cercaria, finna, unarmed and armed tapeworm.

Literature:

Bilich G.L., Kryzhanovsky V.A. Biology. Complete course. In 3 volumes - M .: OOO Publishing House"Onyx 21st century", 2002
Pimenov A.V., Pimenova I.N. Zoology of invertebrates. Theory. Tasks. Answers .: Saratov, Lyceum Publishing House, 2005.
Chebyshev N.V., Kuznetsov S.V., Zaichikova S.G. Biology: a guide for university applicants. T.2. - M .: Publishing House LLC New wave", 1998.