Roundworms are a type of biohazard organisms that cause threats to human beings. The parasitic species like filaria, rishta, whipworm, ascaris, pinworms cause serious human health infections such as diarrhea and fever. Roundworms are contagious and pandemic biohazards.
Features of the structure and reproduction of roundworms
Roundworms (Nematodes) – have a non-segmented cylindrical or spindle-shaped body, consisting of three layers. In the cross section, the body is round (this determines the name of the type). Between the intestine and the body wall of roundworms is the primary body cavity, in the form of a tube. This feature refers to roundworms in the primary cavity.
The body cavity is filled with an aqueous liquid that participates in the process of gas exchange. Like the circulatory system, it distributes nutrients and also removes waste products of decay.
The aqueous liquid is the hydroskeleton, supporting the shape of the roundworm’s body.
Roundworms are covered on the outside with an elastic dense shell – the cuticle.
The cuticle is a dense protective shell that protects the parasite from digestion. Under it are longitudinal muscle fibers. Due to the lack of transverse fibers, the ascaris cannot stretch, but only bends.
Roundworms have a bilaterally symmetrical body.
Digestive system of roundworms
The digestive system of roundworms is located in the body cavity.
Food in the roundworm passes through the oral cavity into the tubular intestine. This perfectly straight tube runs through the entire body.
The intestine consists of three sections: anterior, middle, posterior. Food digested in the intestine is absorbed by its walls and enters the body cavity, namely the body fluid. Undigested food debris is expelled through the anus.
Roundworms do not have a circulatory or respiratory system. They breathe, like tapeworms, with the entire surface of the body.
Nervous system and sense organs of roundworms
The nervous system of roundworms is similar to flatworms. The upper dorsal and lower abdominal trunks are connected to each other by annular bridges and form a near-pharyngeal nerve ring, from which the nerve filaments extend to the sensory organs. The sense organs are very poorly developed, in the skin dimple in the front of the body there are organs of touch. Ascaris has no eyes.
Reproduction of roundworms
Ascaris are dioecious. Males are shorter than females, the tail of the male is bent slightly inward. The female has two gonads, the male has one. A fertilized egg passes into the intestine and, together with undigested food residues, is excreted
A large number of fertilized eggs (up to 200 thousand) turn into larvae in a few days. The larvae through unwashed vegetables and dirty hands enter the human mouth, then pass into the intestines. The larvae dig into the walls of the intestine and cause the disease ascariasis, in which the functions of the intestine are disturbed.
With blood, the larvae can also penetrate the lungs. In this case, a person has an expectorated sputum, coughs. Roundworm larvae, along with sputum, enter the oral cavity, then into the intestines, where they feed on prepared food and develop. After three months, the adult roundworm lays eggs.
Some representatives of roundworms are hermaphrodites.
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Meaning of roundworms
Such free-living species of roundworms as rotifers, bellies and kinorhynchus play a large role in nature.
They are food for various crustaceans, fish and fry. For example, roundworms, called hairworms, look like ponytail hair and reach a length of 1 m. They are harmless to humans, but parasitize in the bodies of insects.
By way of life, roundworms are internal parasites of humans, animals, plants and fungi. Very small representatives in the form of free-living forms, live at the bottom of water bodies or in damp soil. About 20 thousand species of roundworms are known.
Through unwashed vegetables and dirty hands, roundworm larvae enter the digestive system. Sanitary control of water, testing of meat in slaughterhouses, timely detection and treatment of worm-infected people and domestic animals limit the spread of diseases.
Parasitism of roundworms
Such representatives of roundworms as – filamentous worm and beet nematode live in the soil, parasitizing in plant organs, causing damage to roots and tubers. Filamentous worms are parasites of plants, having a body length of only 1-1.5 mm.
Parasitic roundworms of animals (pigs, horses) and humans settle in various parts of the body:
- under the skin (gut)
- in muscles (trichinella)
- in the intestines (ascaris, pinworm).
Pinworm
Pinworms live in the human small and large intestines, most often in children. This is a parasitic worm. The rear end of the male is twisted in a spiral, the body size is about 20 mm.
Ascaris
One of the dangerous parasites of the human intestine is roundworm. Its males reach 15-25 cm, and females 20-40 cm in length. The difference in the anatomical and external structure determines the sexual dimorphism of animals.
The mouth of the roundworm is surrounded by three lips, located at the front end of the body. The posterior end of the body of the worm ends with an anus. Ascaris is able to drill through the walls of the intestine and penetrate into the blood.
The body of roundworms is three-layered. Round in cross section. The body cavity is filled with an aqueous fluid that provides gas exchange, transport of nutrients, and also acts as a hydroskeleton. The body is covered on the outside with a dense shell – cuticle. There is no circulatory and respiratory system. There is an anus. Roundworms are dioecious organisms, but there are also hermaphrodites. Most are parasitic forms.
