Larvae and eggs of nematodes( photo), development and life cycle

Nematodes are round, two-sexed worms. There are about a million subspecies of similar parasites. All of them are united by one: the general scheme of parasitism. The main stages of development of nematodes: eggs - larva - adult. The structure of the reproductive system in males is extremely simple. The reproductive system is a thin tube that expands where a seminal duct is formed, consisting of a seminal vesicle and a canal spewing out the seed.

Female genitalia also have a tubular shape. Symmetrically located in the ovaries and oviducts. They, according to the principle of folding dominoes, flow into the thick tubes of the uterus. The vagina leads to the uterus, which is not connected with the esophagus. It is located separately. The females of these worms lay eggs, from which larvae emerge( they are shown in the photo).In order for them to become invasive, certain conditions must be created. For each species they are different. According to the totality of the generality of these parameters, it is customary to distinguish three types of nematodes.

Cycle of development of nematodes of different species

The group of contact nematodes includes helminths having the simplest life cycle. Sexually mature individuals make a laying of eggs that become invasive without leaving the host organism. Re-infection occurs by contact, through dirty hands. The most striking example of such an invasion is enterobiosis.

The group of geological worms includes round worms, the larvae of which become invasive only when they enter the soil. At a certain temperature( from +18), relatively high humidity, having lain in the earth for a certain time, the larvae of nematodes spend several lines, and only then they become dangerous to humans. Such nematodes have a direct development cycle. Adult individuals parasitize in the lumen of the intestine, they lay eggs, they, together with feces, are naturally released to the outside( into the external environment).Under favorable conditions, the larva ripens inside the egg. In the host's body, it enters passively, also by contact( through the mouth or skin).Geohelminths that affect a person can not live in the animal's body. That is why nematodes, which a person is sick with, are called anthroponous. To this group of parasitic diseases include ascariasis, trichocephalus, ankylostomidosis. An important tool for diagnosing these helminthiases is the analysis of stool. It can detect eggs or worm larvae, and also identify parasites.

Worms belong to the group of biohelminths, for the maturation of larvae, the body of the intermediate host is needed. These can be animals, fish, mites or mollusks. The life cycle of nematodes-biogelminthes is the most complex in terms of development. A person can get infected with worms only if the larvae of nematodes visit the body of one or even two intermediate organisms, where they will spend several lines. For the occurrence of parasitic disease, a person must either eat contaminated meat, or drink dirty water. Very widespread and transmissive pathway of infection( larvae in the body of the final host fall into the bite of small bloodsucking insects).The transmission of invasion from person to person is impossible in this case. The life cycle of individual biohelminths requires the presence of four hosts( the larva can become invasive by making a few lines in the bodies of different incubators).

Life cycle of nematodes

Eggs of almost all nematodes( on photo) have a two-loop shell. Under it is formed an embryo, which at first in shape resembles a bean seed, then on a small worm wound in a ring. He needs further development, which can occur in the environment or in the body of the intermediate host.

There are viviparous nematodes, they reproduce larvae instead of eggs. In some subspecies, the larvae develop in the body of a sexually mature female and are born already in a mobile form. After the birth of larvae, the development of viviparous nematodes also proceeds in different ways. Much depends on whether it is necessary to change the habitat for larvae or not, whether an additional living incubator is needed to develop the larva or nematode has a direct life cycle of reproduction.

Knowing how the development of individual species of nematodes occurs, you can try to prevent any helminth disease. Simple preventive measures prevent infection and preserve precious health. Virtually every invasion is dangerous in that it causes system failures in all internal systems. Some round worms can provoke a fatal outcome.

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