Most of the species of organisms that exist on our planet, for many centuries and millennia, followed the path of evolution and biological progress. However, there are such representatives of wildlife who have achieved more success in a completely different way - by regression or simplification of the organization. How did this happen and how can it be useful? It turns out that this is a necessary condition for maintaining a parasitic lifestyle. Particularly successful in adapting to life at someone else's expense were different types of worms - helminths, which we will talk about later.
The structure of parasitic worms
Helminths, or parasitic worms, include organisms that have adapted to live inside mammals and other creatures, including humans, causing serious harm to the he alth and even life of the host with their vital activity. Each parasitic worm is capable of changing several hosts during its life cycle. This is necessary to maintain the number and survival of eggs, that is, future offspring.
Of course, each class has its representatives, who, in turn, are endowed with features that distinguish them from each other and allow them to be uniqueparasites. However, there are a few common characteristics that each parasitic worm has.
- In the structure of the body there are organs that serve to fix in the body of the owner. Examples: suction cups, hooks.
- The presence of special body coverings that do not allow the host's body to digest them.
- Laying offspring of several million eggs at a time and the complex structure of the reproductive system (most often hermaphroditic type).
- Regression in the structure of all sense organs. The digestive and excretory systems are as simple as possible in structure and functionality. Breathing is carried out by the entire surface of the body.
- Ability to reproduce at the larval stage.
All these features make different types of parasitic worms simply universal and very dangerous creatures with simply colossal survival.
Classification of parasitic worms
In total, two main groups of such organisms can be distinguished.
- Type Flatworms. It is parasitic forms that are the classes Tape, Flukes. Types of parasitic flatworms of this type: bovine tapeworm, pork tapeworm, tapeworm, echinococcus, feline fluke, schistosome, paradoxical leukochloridium, flukes and others.
- Type Roundworms. Class Proper roundworms. Examples of organisms: anisakids, pinworms, roundworms, hookworms, guinea worms, whipworms, trichinella, filaria and others.
Types of parasitic worms are very diverse. In total, scientists identify about 300 representatives that can live in the body.of humans, not to mention other animals. The harm done by these creatures is truly sometimes irreparable.
Class Proper roundworms: parasitic forms
Compared to flatworms, this group is more highly developed in terms of body structure. So, this class of parasitic worms has the following features.
- Separate cavity. Males have testes and a vas deferens that opens into the hindgut. Females - ovaries, combined into a common vagina. Reproduction is sexual only.
- Low ability to regenerate lost body parts as cells are limited.
- The anus appears. Thus, the digestive system looks like a simple tube, which consists of the mouth, middle and anus.
- The nervous system is represented by ganglia. So far quite simple, but nevertheless already existing.
- Excretory system like protonephridia.
- Integuments of the body are three-layered, the outer one is the hypodermis. It performs not only a protective role, but also the function of a skeleton. Metabolic processes take place in it.
- The center of the body is occupied by a pseudo-target - this is the cavity in which the liquid is located. She acts as blood.
A parasitic worm of this class can lead a different lifestyle. So, bio- and geoparasites are isolated. Biohelminths should include those species that change several hosts during their life and thus spread. To geohelminths - those whose distribution occursin the external environment.
Vlasoglav
This parasitic roundworm belongs to geohelminths, because it needs two conditions for reproduction, growth and development:
- presence of the human body;
- ordinary wet earth.
With such modest needs, it is not surprising that the prevalence of this helminth is very high. By itself, an adult worm rarely reaches a length of 5 cm. Males and females differ in the posterior end of the body: in the former it is thickened and spirally twisted, while in the latter it is elongated, filiform.
The parasite does not feed on the contents of the human intestine, but on its blood, so treatment from its effects requires special treatment. It deeply affects the intestinal wall, so it can cause inflammation. It affects the body with the products of its vital activity.
The disease caused by this creature is called trichuriasis. Infection occurs through tactile contact with dirty vegetables and fruits, water. It is on these objects that the barrel-shaped eggs of parasites are located, which reach sexual maturity inside the body in a few weeks.
Eggs are hatched with faeces and develop in the external environment - in warm, moist soil. Back again swallowed by a man.
Pinworm
The parasitic roundworm, which occurs in almost every second child, can also be present in an adult. Small white parasites rarely exceeding 5 mm in length. Themthe main feature that allows it to spread so widely is the absence of a change of owner. They parasitize in one organism, feeding on the contents of its intestines.
They come out of the anus at night and lay a lot of eggs on the circumference of the anus. This causes itching and irritation in the child, he begins to scratch this place unconsciously in a dream. So the eggs get under the nails, from where again into the oral cavity and on the surrounding objects.
After laying eggs, the female dies. Therefore, in the case when re-infection is not observed, it is possible to cure the body without medical intervention. The disease caused by pinworms is called enterobiasis.
Trichinella
A parasitic worm of very small size. Rarely reaches a length of 3.5 mm. Males are even smaller. Refers to biohelminths. They parasitize humans and mammals. They affect the muscles, as they settle and settle in them. Each female is able to lay enough eggs (up to 2 thousand) and die after that.
About two months later, larvae emerge from the eggs, which are carried throughout the body with a current of lymph and blood, strengthening in the muscles and disrupting their normal functioning. The disease is called trichinosis, and if heavily contaminated with parasites, it can be fatal.
Type Flat, class Tapeworms
Representatives of this type can be both free-living and parasitic forms. All of them are characterized by some features in the structure of the body.
- Bilateralsymmetry.
- No body cavity.
- Colossal ability to regenerate.
- The most simplified digestive system.
- The vast majority of species are hermaphrodites.
The main parasites are two classes - Banders and Flukes.
Broad tapeworm and echinococcus
The broad tapeworm is a parasitic tapeworm that goes through three hosts in a lifetime. The first of these are crustaceans, the second is fish, the third and final is man. The length of these helminths can be up to several meters. They feed on the contents of the intestine, which causes severe starvation and a lack of substances for the life of the host.
Infection occurs through fish that a person eats. The disease is called diphyllobothriasis.
Echinococcus is also a parasitic tapeworm. Its peculiarity is that a person for him is an intermediate host. The main ones are dogs and wolves. However, once in the human body, the larvae are carried by the bloodstream. Then larvae emerge - oncospheres. They form a bubble, which begins to grow gradually. This disease is called echinococcosis.
Both considered species of the parasite have several rows of tenacious hooks for rooting in the host organism, which cause additional harm and cause pain. Also common and terrible tapeworm parasites are tapeworms - bovine and porcine.
Schistosome and leukochloridium paradoxical
Which of the parasitic worms is characterized by a changehost with the participation of gastropods? The answer is: for many flukes. These are worms that have numerous suckers. It is by them that they are fixed in the body of the final owner, which is a person.
Schistosoma is a type of infection that occurs when swimming in water where the larvae swim. They feed on the blood of mammals. Their main danger is the spikes on the body, with which they pierce the walls of internal organs, causing their inflammation, the occurrence of cysts, tumors. It is difficult to cure these parasites.
Leukochloridium is paradoxical - it is he who uses gastropods as one of the hosts. This worm chose birds as the final point for life. It is interesting that in the body of the snail the larva grows and becomes so convex that it is visible from the outside. It resembles a bright green caterpillar, which attracts birds. They peck at it, resulting in infection.
Measures against parasitic worms
The fight against parasitic worms is not easy. The most important thing is the careful observance of all necessary preventive measures. Personal and public hygiene is of great importance. Without this, it is impossible to fight helminth eggs. Secondly, it is certainly a good heat treatment of food.
Treatment for each specific type of parasite is strictly individual and is prescribed by a doctor. Most often these are tablets ("Vermox", "Decaris", "Pirantel", etc.). However, in more severe cases, injections are also necessary,droppers, radiation and other types of exposure.
