The number of roundworms. §17. Type Roundworms. Questions for consolidation

Task 1. Fill in the table.

Characteristics of the type Roundworms
Representatives of the type	General features of the structure	Specific features of the structure	Habitat and lifestyle
roundworm Task 2. Fill in the gaps in the text. Human roundworms have separate sexes. The reproductive organs of the female are paired ovaries, the male is the filiform testis. Every day the female lays about 100-200 thousand eggs. Large roundworm ensures the preservation of eggs in nature, since most of them do not enter the body and die. Eggs are covered with a strong and dense shell. From the human intestine, they enter the bloodstream, the lungs. After two or three weeks, the larva develops. A prerequisite development from roundworm eggs is the presence of a damp environment. If eggs with larvae enter the human body, then infection with ascariasis will occur. Task 3. Fill in the table. Comparative characteristics bull tapeworm and human roundworm Comparable feature View human roundworm Bull tapeworm Type of roundworms flatworms body integuments tight and elastic cuticle dense cuticle and epithelium body cavity primary body cavity primary body cavity Nutrition and digestion has a mouth, esophagus, stomach and anus there are no organs of nutrition, food is absorbed through all the integuments of the body Breath through all the integuments of the body do not use oxygen for breathing Selection through the excretory opening leftover food is expelled through the mouth Nervous system longitudinal nerve trunks underdeveloped, sensory organs absent Reproduction and development dioecious reproduction hermaphrodites Task 4. Write down the numbers of signs characteristic of the human roundworm. Signs of animals. 1. Free-living worm. 2. Body with bilateral symmetry. 3. Hermaphrodite. 4. The larva develops in the intermediate host. 5. The intestine ends with an anus. 6. The larva develops in the lungs, but with the blood enters the heart and liver. 7. Has a circulatory system. 8. Dioecious animal. 9. Reproduces in the human intestine. 10. intermediate host- cattle. 11. The body is covered with a dense cuticle that protects the worm from the digestive juices of the host. 12. The body is ribbon-like, jointed. 13. The female is larger than the male. 14. There is no mouth opening, food is absorbed by the whole body. 15. There is a digestive and nervous system. Signs of roundworm: 4, 3, 8, 9, 13, 15. Task 5. Fill in the table.

Free-living nematodes:

• live in soil and water;
• participate in the ecology of all ecosystems;
• second in number only to arthropods.

The concentration of free-living nematodes is about 1 million individuals per 1 m3.

Harm to humans and animals:

Type roundworms are distributed throughout the globe.

General characteristics of the type

Circulatory and respiratory systems

At roundworms no respiratory and circulatory system. Almost all members of the nematode family live in anaerobic conditions, and receives oxygen and nutrients already in finished form.

In the hypodermal layer, glycogen accumulates, which is also split there into oil, valeric and other important organic acids. Suction finished nutrients occurs through the epithelial layer of the primary cavity (intestine), and accumulates in the hypodermis.

Such a primitive life support system makes the respiratory and circulatory system redundant in the existence of the worm.

Morphology

Body structure (from outer layer to inner):

• Pseudochain - the primary cavity, lined with epithelium (intestine).
• Coeloma - secondary cavity without epithelium.

Digestive system of roundworms

At the anterior end of the body there is a mouth opening with lips made of cuticular sweets. Further, the oral capsule begins (in some species armed with teeth), and then a small segment of the esophagus begins.

Whole digestive tract forms one rectum, which is divided into:

• front;
• average;
• back departments.

Some species do not have an anus.

Nervous system

Nervous system of nematodes:

• peripharyngeal ring- located in the middle of the pharynx with an inclination to the dorsal edge (in some species to the ventral)
• Ventral (abdominal) nerve trunk- goes along the lower plane of the body in the ventral ridge of the hypodermis. Other small nerve fibers originate from it.
• Dorsal (dorsal) nerve trunk- passes in the dorsal roller of the hypodermis. Does not "let" nerve fibers.

Also, roundworms can be guided by smell and light.

reproductive system

They belong to dioecious worms with pronounced sexual dimorphism. Females lay eggs, larvae can hatch either in the external environment or in the body of the female (live birth). The females are larger than the males.

The reproductive system of females is steam, tubular and consists of:

• ovaries;
• oviducts;
• uterus;
• vagina.

The ovaries are narrow, blindly curved, gradually turning into wider sections. The uterus is a steam room that extends into the vagina, which opens on the ventral side in front of the body. Females can be several times larger than males, the body is straight.

In males, the end of the body is spirally wrapped towards the abdominal plane.

The structure of the male reproductive system:

• Tubular seed.
• Semen tube.
• The vas deferens that opens into the posterior intestine.

On the cloaca there are copulatory spicules, with which the male holds the female.

In some species, the spicules have capulative burses, which are expanded and flattened in the form of wings, the lateral parts of the posterior end of the body.

excretory system

It consists of two tubules that begin in the back of the body, connecting to form a common duct that opens with an opening on the ventral side of the anterior end of the body. The movement of the body is carried out only in the dorsoventral (forward) direction.

Representatives of the nematode type in the human body

Ascaris human

The causative agent ascaris lumbricoides is a nematode, the length of the male is up to 25 centimeters, and the female is up to 40 centimeters. Body color from white to pale pink, narrow, cylindrical, pointed at the ends. The mouth is a pair of cuticular lips.

In skinny and ileum live for about a year, capable of living only in the human body. At one time, the female is able to lay up to 240 thousand eggs, which are released into the external environment along with feces. Eggs in the external environment can live up to 5 years, thanks to a five-layer outer shell that protects against most environmental factors.

Developmental Biology:

• Enter the rectum through food or dirty water, are then localized in small intestine.
• After 21 days, the larvae hatch, penetrate the intestinal mucosa. With the blood flow they migrate through the internal organs: the liver, the right part of the heart, the lungs.
• Once through the pulmonary circulation into the lungs, the larvae break through the alveolar capillaries and, together with cough or exhaled air, enter oral cavity.
• They are swallowed through the mouth and back into the digestive tract.

The entire migration period takes up to two weeks. The female becomes sexually mature after 20 days and is able to lay eggs.

Pinworm

A nematode that causes a common disease is enterobiasis. This disease is also called "disease of unwashed hands", since the eggs of the pathogen often enter the human body through dirty food and hands. Children are mostly affected. The causative agent is localized in all parts of the intestine, and the main symptom of the disease is the tooth of the anus.

Enterobius is a nematode with an elongated body and narrowed ends. Females reach a length of up to 12 millimeters, and males up to 5 millimeters.

The color of the pathogen is grayish-white. At the mouth opening from the side abdominal cavity a special vesicle is located, with the help of which the helminth is attached to the intestinal mucosa.

Developmental Biology:

• fall into human body together with food, are localized in lower sections small intestine, attached to the intestinal mucosa.
• The female becomes sexually mature at the age of 4 weeks.
• The fertilized female moves to the rectum to lay eggs.
• At night, it comes out of the anus and lays eggs in the anal folds, after which it dies.
• One female is able to lay up to two thousand eggs.

Vlasoglav

Nematode, disease-causing trichuriasis. The causative agent is considered only human, small children are especially susceptible. The habitat is initial department large intestine. With a small invasion, the symptoms of the disease almost do not appear, but with a strong infection, diarrhea, vomiting, prolapse of the rectum are possible, and are also one of the causes of inflammation of the appendix.

The causative agent trichocephalus trichiurus is a helminth 3.5 to 5 centimeters long.

Basic hallmark is the presence on the front of the body of a threadlike part, on which the mouth opening and esophagus are located. In the rear compacted part are the remaining organs of the helminth. One individual is able to live in the human body for up to 5 years.

Developmental Biology:

• Helminth eggs enter the human digestive tract through contaminated food or water.
• Once in thin department intestines, hatching of larvae occurs within a few days.
• Immediately migrate to the large intestine.
• In the thick section, they are attached to the mucous membrane with a filiform process, cutting through the mucous membrane with it. They feed on blood and tissue fluid. After 3 months they become sexually mature.
• For a day, the female whipworm is able to lay 20 thousand eggs.

A prerequisite for the maturation of an invasive egg is to stay in moist soil at a temperature of 24-30 degrees for 10-40 days. After maturation, they remain capable of infection for several months.

Flat and roundworms: differences

Differences between flatworms and roundworms:

1. Intestines- flatworms have only a mouth opening, there is no anal opening. Excrement is excreted through small tubules that penetrate the entire body of the worm and exit through the outer integument. Nematodes have mouth and anus intestinal tract through.
2. reproductive system- , with the exception of the family of trematodes Schistosomatidae - hermaphrodites. There is an opinion that reproduction in flatworms occurs cross, but self-fertilization is not excluded. Nematodes have a strict distribution of sexes with pronounced sexual dimorphism.
3. Presence of cavities- at roundworm there is a primary and a secondary cavity, when both flatworms belong to barren animals. In the skin-muscular sac of trematodes, digestive and excretory processes and the absorption of nutrients occur.
4. Nematodes have only longitudinal muscles, which allow the worm to move exclusively in the dorsoventral direction, and flatworms also have transverse and longitudinal muscles.

Read the information .

roundworms(primary cavity or nematodes) - three-layer multicellular animals with bilateral symmetry of the body, which has a cylindrical shape with a circular cross section.

The group was first identified by the German zoologist K.A. under the name Nematoidea (Nematodes).

To date, most scientists distinguish 2 classes in the Nematode type (Adenophores and Secernents).

Structural features

1. have a cylindrical or spindle-shaped body. In cross section - round (hence the name of the type).

2. there is no segmentation of the body.

3. have an external cuticle, which performs the function of the external skeleton (protects against mechanical and chemical influences).

4. have a body cavity - a separate space between the body wall (muscular skin sac) and internal organs (in flatworms, this space is filled with loose fiber - parenchyma).

It is believed that roundworms are descended from a group of flatworms.

Aromorphoses that contributed to the appearance of roundworms:

• the emergence of a primary body cavity (the second name of the type is primary cavity)
• progressive development nervous system(formation of ganglia, parapharyngeal nerve ring, dorsal and ventral nerve trunks)
• appearance back section intestines and anus
• the appearance of an excretory opening
• the appearance of four muscle strands, which made it possible to bend when crawling
• the emergence of dioecious reproductive system and internal fertilization

Footnotes

Ascariasis – parasitic disease human and pigs, caused by roundworms. Symptoms: mainly indigestion, exhaustion.

Trichinosis- an invasive disease of humans and animals (pigs, dogs, cats, ruminants, rodents, etc.) caused by trichina.

Dracunculiasis- an invasive disease of humans and animals caused by guinea worm (affects the subcutaneous tissue).

Trichinella(trichina) - a worm of the nematode class.

Hookworm- a worm of the nematode class.

Rudolphi Asmund Karl (1771 - 1832) - German naturalist, zoologist and botanist.

Used Books:

1. Biology: a complete guide to preparing for the exam. / G.I. Lerner. – M.: AST: Astrel; Vladimir; VKT, 2009

2. Biology: Animals: textbook. for 7-8 cells. general education institutions. – 7th ed. – M.: Enlightenment, 2000.

3. Biology for applicants to universities. Intensive course / G.L. Bilich, V.A. Kryzhanovsky. - M .: Onyx Publishing House, 2006.

4. Biology: study guide / A.G. Lebedev. M.: AST: Astrel. 2009.

5. Biology. Full course general educational high school: tutorial for schoolchildren and entrants / M.A.Valovaya, N.A.Sokolova, A.A. Kamensky. - M .: Exam, 2002.

Used Internet resources:

Nematode plant diseases

The systematization of roundworms is still open. Initially, all worms (round, flat, annelids) were combined into one type - worms. In this taxonomy, the class of roundworms was subdivided into two subclasses :

• Adenophorea (Adenophorea) ;
• Secernents (Secernentea) .

The difference between subclasses consisted in the presence or absence of phasmid - tactile organs. After combining roundworms into a separate type group, a classification was proposed that distinguishes six grades :

• Nematodes (Nematoda) ;
• Gastrociliary (Gastrotricha) ;
• Kinorinchi (Kinorinchi) ;
• Hairy (Gorciiacea) ;
• Rotifers (Rotatoria) ;
• Acanthocephala (Acanthocephala) .

Subsequently, gastro-ciliated, rotifers, hairy, acanthocephalans were separated into separate types, and kinorhynchus became a class of the clade Cycloneiralia. The class Nematodes or, in fact, Roundworms has also been revised. Modern taxonomy (2011) highlights three classes of roundworms :

• Chromadoria (Chromadorea) ;
• Oenoplia (Enoplea) ;
• Dorylaimea (Dorylaimea) .

Rice. 1. The human roundworm is a representative of chromadoria.

Some experts consider the class Dorylaimea to be a subclass of Enoplea.

The classes include 31 orders, more than 200 families, and about 3000 genera. Currently, about 30 thousand species have been described, but the diversity of nematodes suggests about a million species.

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Main Representatives

Rice. 2. Potato nematode.

The main signs of roundworms:

1. They have a non-segmented, rounded body in cross section. Its surface is three-layered and consists of meso-, endo- and ectoderm. The worm has a skin-muscular sac.
2. All types annelids have a pseudo-target - this is the primary cavity of the body filled with liquid. It gives the body additional elasticity and performs the functions of a hydroskeleton. This fluid is also responsible for metabolic processes. This is where everything is internal organs, forming the digestive, nervous, excretory, muscular and reproductive systems.
3. The structure of roundworms is such that they lack a respiratory and circulatory system.
4. Features of roundworms are that they digestive system represented by a through tube beginning with a mouth opening. The mouth is surrounded by cuticular lips. At the end of the digestive tube is the anus. The whole tube is divided into three sections. Pinworms have a special extension of the esophagus called the bulbus.
5. As for the nervous system, it consists of the peripharyngeal ring, head ganglia and nerve trunks (abdominal, spinal and two lateral trunks). The most developed abdominal and dorsal rods. They are connected by special jumpers.
6. No matter how many species of roundworms, all of them have poorly developed sense organs. As a rule, they consist of tactile tubercles and special organs of chemical sensation.
7. The excretory system of the roundworm consists of a small amount excretory phagocytic cells. They accumulate metabolic products and foreign substances that enter the cavity of the body.
8. Nematodes are roundworms that have tubular structure genitals. The number of genital organs of the female, as a rule, is paired. The male, on the contrary, has unpaired genitals. His genital apparatus incorporates the testis and the vas deferens, which passes into the ejaculatory canal and opens into the back of the intestine. The body structure of the female is somewhat different. Her reproductive apparatus consists of paired ovaries, from which come two tubular oviducts and a paired uterus. It unites into a common vagina.

We have listed common signs, characteristic of representatives of the type roundworms. However external structure individual individuals may differ slightly. So, if you describe a group of roundworms, the representatives of this class are as follows:

• roundworm;
• whipworm;
• pinworms;
• hookworm;
• trichinella;
• guinea worm.

Roundworm

It's pretty large helminth, the female of which can grow up to 40 cm, males - about 20 centimeters. Ascaris has a cylindrical body narrowed towards the ends. The body of the male from the rear end is twisted in a spiral towards the abdomen.

Important! Infection of people occurs when eating unwashed fruits and herbs.

The life cycle of roundworm in the human body is as follows:

1. After the egg is in the intestine, its shell dissolves digestive juices, and a larva emerges from it.
2. It enters the bloodstream through the intestinal walls. It then migrates through the liver to right atrium, stomach and lungs.
3. From there, through the pulmonary capillaries, the larva enters the bronchi and trachea, provoking a cough.
4. During coughing, it is swallowed again and again ends up in the intestines. Here she reaches the state of a sexually mature individual, lives and breeds for up to a year.

Pinworms

Important! Eggs become infectious a couple of hours after they are laid. If, while combing this area, the eggs fall under the nails of the patient, he re-infects himself if hygiene is not observed.

Since the life expectancy of a sexually mature pinworm reaches 58 days, the patient may self-heal if it has not happened. reinfection. As for males, they die immediately after mating with females and leave the body. naturally(with feces).

Vlasoglav

The anterior filiformly elongated part of the body of the worm is thinner than the posterior one. It contains the esophagus. The posterior end of the male is thickened and spirally twisted. This is where the intestines are reproductive system. The eggs of this worm outwardly very much resemble a barrel with caps in the form of corks at the ends. They are light transparent and reach 50 microns in length.

Trichinella

This worm is a biohelminth. His life cycle next:

The worm lives in the small intestine, where it can live up to five years. It is referred to as geohelminths. Hookworm migrates in the human body like roundworms. Eggs with feces enter the external environment, where a day later they hatch into larvae that feed on feces. After they reach the filarial stage, the larvae become infective.

Sometimes infection occurs by the oral route, but more often filariae enter through skin. From the intestine, the larvae migrate to blood vessels and lungs. Then they rise through the bronchi to the trachea, from where during cough reflex thrown into the mouth and swallowed. After that, they settle in the duodenum.