Scrapes: Class, Species, Types, Class And Representatives

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Scrapes: Class, Species, Types, Class And Representatives
Scrapes: Class, Species, Types, Class And Representatives

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Video: Scrapes: Class, Species, Types, Class And Representatives
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  • Morphology
  • Features of life

    Reproduction

  • Classification
  • The circulation of worms in nature
  • Life cycle of scrapers
  • Spread
  • Economic value in the defeat of domestic animals and livestock
  • Danger to people
  • Diagnostic methods
  • Prevention measures
  • You can defeat parasites!

Scrapes (thorn-headed worms or Latin Acanthocephala) are a type of parasitic worm that includes about 1150 known species and is characterized by the presence of an everted proboscis with hooks. They have a complex life cycle involving terrestrial or aquatic vertebrates (final hosts) and insects or crustaceans (intermediate hosts).

Scrapes represent one of the groups of helminths. In animals and rarely in humans, a group of diseases called acanthocephalosis is caused, which is divided into smaller types of helminthiasis, depending on the pathogens.

What to do in such a situation? To get started, we recommend reading this article. This article details the methods of dealing with parasites. We also recommend contacting a specialist. Read the article >>>

Morphology

The size of the scrapers varies greatly depending on the species. Adults have a body length from one millimeter to 65-70 cm, which can be reached by the largest species, the giant comb.

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Scrapes are spindle-shaped worms, the body of which has a proboscis covered with cuticular hooks in several rows. The hooks are bent back and are needed for the parasite to attach to the intestinal wall of the host. The proboscis is hollow from the inside and can be turned in the opposite direction. It is also able to be drawn into a saccular formation that hangs down into the body cavity, called the proboscis sheath and contains a muscle cord. From this cavity to the final part of the body, a cellular cord passes - the so-called intestinal rudiment.

Adults live in the intestines of their host and absorb nutrients from the surface of the body (like tapeworms). Breathing is carried out in the same way.

The circulatory, digestive and respiratory systems are absent. The skin of the ridge has thin membranes that cover the epidermis, consisting of syncytium without cell walls. Only representatives of the Archiacanthocephala class have a protonephridial excretory system.

The nervous system is an oval or spherical ganglion, which is located in the proboscis sheath, and also includes the nerve trunks.

In males, the reproductive system consists of two testes, the vas deferens, cement glands, the vas deferens and the copulatory apparatus. In females, egg lumps are found in the body cavity. A genital opening is located in the posterior caudal region. The reproductive system consists of the uterus, two oviducts, the uterine bell, the vagina.

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Features of life

All scrapers feed exclusively through the epidermis, absorbing the host's undigested food by the surface of the body. To do this, they have an appropriate structure - circular channels ("lacunae"), which are additionally connected by transverse channels inside the epidermal syncytium (a special type of tissue). This system is connected to the outer depressions of the epidermis and the cavities of the musculature.

At the same time, there are no holes in the cavities, and nutrients, especially proteins and monosaccharides, enter the canals and are distributed thanks to a special coating of the epithelium called glinocalyx. The contractions of the worm help the nutrients spread evenly throughout the body.

Reproduction

All scrapers are dioecious - there are males and females. During mating, the male surrounds the rear end of the female with his copulatory bursa (bursa), and then, when this bursa is turned inside out, the back of the female approaches the copulatory organ. The resulting seminal fluid flows through the female's seminal duct and fertilizes the egg clumps in the body cavity. After that, the male from the cement gland secretes a substance that clogs the genital opening of the female, so that the other cannot fertilize her.

The scrapers produce a huge amount of eggs. For example, a female giant scrubber produces about 800 thousand pieces per day. Then they leave the host's body and enter the soil or water. In this case, the shell can be coated with sugars to increase the chances of being eaten by an intermediate host.

Classification

A complete classification of animals has not been drawn up, there are four main classes:

  • Archiacanthocephala - a distinctive feature is the presence of special excretory organs, the arrangement of thorns in a circle;
  • Eoacanthocephala - spines are located radially;
  • Palaeacanthocephala - differs from Eoacanthocephala in the organization of the cement gland;
  • Polyacanthocephala - Genetically distinct with three main classes.

The description of the species is incomplete; there are a number of worms that have not been classified by scientists.

The circulation of worms in nature

The comb during the life cycle must visit the body of several hosts:

  • at the stage of development, from birth to a young larva, in the body of arthropods - crustaceans, millipedes, insects, molluscs;
  • at the stage of puberty, mating assimilate the main host - fish, bird, mammal, human.

Life cycle of scrapers

The final owners of worms can be terrestrial vertebrates, marine and freshwater inhabitants (amphibians, reptiles, mammals, fish), birds, and in rare cases, humans.

Intermediate hosts are arthropods - crustaceans, millipedes, insects. In one known species of worms, a mollusk may be an intermediate host.

The worms have a complex life cycle, for the passage of which the worms use several hosts and go through several stages of development. The life cycle of only 25 species of worms has been fully studied. The main stages are described below, but each specific comb has its own developmental characteristics. For example, there are scrapers that can change the behavior, habitat, or color of intermediate hosts to increase the chances of the final ones entering the body.

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From the infected final host, the eggs of the worm come out with feces. In the human body, scrapers do not usually multiply. The scraper begins its life path in the body of the invertebrate intermediate host, which has swallowed the eggs of the worm. Inside it, freeing itself from the capsule, the first larval stage (acantor) develops, then the acantor is localized in the intestinal wall, reaching the next form of acanthella, this takes from several hours to two weeks, depending on the type of worm.

The larva then invades the body cavity to encapsulate. Further, the internal organs are formed, and after a few weeks the larva turns into a small copy of an adult individual of the worm, but the reproductive system at this stage is not fully developed, since the reproductive organs are far from each other. In this form, the worm is called cysticant, it is in the infectious stage.

Infection of the final host occurs by eating invasive insects or crustaceans. The worm has a special proboscis for anchoring to the intestinal walls. In the organs of the final host, the larva develops over several weeks and reaches the stage of a sexually mature individual, ready for fertilization and the production of eggs, which are thrown into the external environment with feces. This completes the life cycle of the scraper.

Scrapes can have a reservoir host; vertebrate aquatic or unearthly animals play its role. This complicated life cycle of the comb is possible when infected fish or animals enter the body of the final host, in whose organisms the larva did not have time to reach the stage of a sexually mature individual.

Spread

Some worms live in certain localities and only parasitize in specific final hosts. For example, there are species of worms that infect Antarctic seals or Australian marsupials. Acanthocephalus reunionensis is found in freshwater eels in the Indian Ocean on Reunion Island, and Pomphorhynchus moyanoi infects freshwater fish in central Chile.

Isolated cases of human infection were recorded in Australia, Asia (Pakistan, Bangladesh, Indonesia, Japan and Iran), Europe (Italy, Russia), America (Florida, Alaska, Texas and Honduras), Africa (Madagascar, Sudan, Nigeria and Egypt).

Economic value in the defeat of domestic animals and livestock

Young animals are hard to tolerate the course of the disease, possibly a lag in their development and growth. Acanthocephalosis in fish often causes exhaustion and death. Adult animals may not feel the disease, and it is possible to detect infection only during autopsy, revealing pathological changes in the intestine in the form of tubercles.

Domestic pigs become infected with the giant scraper most often in regions and countries where animals are raised on free grazing. In modern times, European countries use intensive methods of raising pigs, that is, animals are kept in closed rooms, where only special food is used, with this method, infection with a scraper is practically impossible.

In the aquaculture sector, infestation with scrapers not only causes impaired growth of fish, but parasites are also the causative agents of other diseases in important species of the inhabitants of water bodies. Worms mainly affect the intestines. Cases of protruding eyes have been reported in trout when infected with Echinorhynchus truttae.

European zoos in the 1960s-1980s identified primates infected with the giant scraper and Prosthenorchis elegans. Cockroaches, which lived freely in animal enclosures, were considered carriers of parasites. Over time (since 1990), strict hygiene practices have led to a rapid decline in the spread of scrapers.

Danger to people

Scrapes play an insignificant role as parasites for humans. Humans rarely act as the definitive host for the giant ridge (Macracanthorhynchus hirudinaceous), as well as for smaller species.

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In humans, the giant comb reaches up to 70 cm in length. It is the largest representative of this class.

Moniliformis moniliformis is one of the small species that has been identified in a human body infected with helminths, but such cases are extremely rare. An adult worm reaches a length of 10 to 30 cm, males are much smaller - from 4 to 5 cm.

The genus Bolbosoma infects fish. Several cases of human infection with these representatives when eating raw fish are described.

Diagnostic methods

It is possible to establish the correct diagnosis in fish only after opening the carcasses. With intensive infection, jaw-toothed animals are fed with organotin compounds. To reduce the scale of infection, sick fish are caught, and they are actively fighting carriers of the intermediate type.

The period from the moment of infection to the onset of symptoms of the disease is 21 days. After another two weeks, eggs can be found in the stool and the correct diagnosis can be established. Acanthocephalosis is characterized by severe symptoms, partly due to mechanical damage to the intestinal walls.

In humans, scraping parasites cause the following signs of infection:

  • sharp pain;
  • bloating;
  • feverish conditions;
  • weight loss against a background of decreased appetite;
  • nausea and vomiting;
  • severe weakness;
  • stool disorders.

It is extremely important to seek timely help from specialists. Since the disease can become chronic.

In medicine, there are no special drugs for the destruction of worms. These worms are still poorly understood due to rare infections. You can get rid of parasites with the help of conventional anthelmintic drugs. You just need to seek help from doctors, strictly observe the prescribed dosage and other recommendations.

Prevention measures

To avoid infection, you need to carefully monitor personal hygiene, do not eat raw fish, neglect preservation of suspicious quality. It is important from time to time to carry out the prevention and treatment of pets (especially cats) from helminthic invasions, to poison cockroaches. Following simple guidelines will help reduce the risk of a scraper infection.

Scrapes are more common in river fish, less often in sea fish. Some of the species cause intestinal pathologies that provoke the death of jawbones. To avoid infection, fish meat should be properly heat treated, frozen, or salted for a long time. Non-living scrapers and nematode larvae are safe for human health.

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