Some of the animals are born and die, spend their lives in the organisms of other representatives of the fauna. The former use the latter as power sources. Animal parasites can also be on the body of another animal, feed on its blood. For example, fleas and lice live on the skin of the host (the so-called organism, due to which the existence of parasites occurs). Some parasitic animals can provide themselves with food in the intestines, blood vessels, and other organs, causing enormous harm to their owners. This may not cause death, but it leads to a general and global weakening of the body. They can also cause diseases that spread from some fauna to humans.
Parasitism
The word "parasite" itself has Greek roots and literally translates as "parasite". Large and small, “parasites" feed on lymph and blood, tissues and overcooked food, constantly or temporarily use other organisms as a habitat. Parasitism is one way of coexistence of various species of animals. It is internal, external and nesting.
Domestic
Parasite animals of this kind (their names are in the hundreds) penetrate the internal organs of various animals, live there, reproduce, giving innumerable offspring, causing various poisonings by the products of their vital functions, as well as certain types of diseases. A person, as a rule, can become infected by eating animal meat that has not undergone sufficient heat treatment.
Protozoa
These parasitic animals are so small that they can be confused with bacteria. By structure, these are unicellular organisms. They may or may not have a shell, reproduce sexually or asexually, be static or move. As a rule, they live on the mucous membranes, in the blood, glands. From Toxoplasma gondii, the causative agent of Toxoplasmosis and Leishmaniasis, Leishmania donovani, can be identified as especially dangerous for humans. These animal and human parasites are usually transmitted through food.
Helminths
The sizes of parasitic worms are various and range in length from a few millimeters to several meters. May cause helminthiases. They are divided into three groups: trematodes, nematodes and cestodes.
Trematodes
Attach with suction cups and have an oblong body without segments that resembles a leaf. For example, hepatic fluke, which lives in the bile ducts of a sheep, but can also be transmitted to humans. It reaches a centimeter wide, and in length - up to three.
Cestodes
These parasitic animals are called “shadows,” or tapeworms. They can parasitize in the adult stage in the intestines of both humans and animals. And in the larva, they are found in some organs of fish, insects, and mammals. They have a flat segmented body of various shapes. They feed diffusely with the help of osmosis, since they are devoid of digestive organs. For example, ekinococcus can parasitize in the intestines of dogs, and tapeworm (sometimes its length reaches five meters) can occur in the adult stage in the intestines of humans. The larval stage of the tapeworm takes place in the pig’s muscles, and by consuming such meat without sufficient heat treatment, people can also become infected.
Nematodes
These roundworms (e.g. Trichinella spiralis) are up to three millimeters in length. Adult forms parasitize in the intestines of animals and humans, larvae can be in the muscles. When consuming pork infected with larvae, a person, as a rule, also becomes infected with nematodes.
Arthropod Parasitic Animals
Examples: ticks, lice, fleas and mosquitoes. Of ticks that are intermediate hosts and carriers of various pathogens of diseases - a whole family of ixodidae (Ixodidae). And the Sarcoptidae family also includes various ticks that cause scabies in humans. Parasites penetrate the intradermal passages in order to lay eggs, or live on the surface of the skin. They relate to external parasites.
Mosquitoes
It is also an external animal parasite. Examples of their "parasite" activities - blood supply. They do not inhabit the human or animal body, but parasitize using blood (ectoparasitism) as food. Interestingly, mosquitoes of both sexes feed, as a rule, on nectar and plant sap. However, many species (in Russia there are more than a hundred) have adaptations of the mouth to pierce the skin of the victim. The female receives nutrients from the blood and acquires the ability to lay more eggs. Moreover, both nutritional options are present: both blood and nectar. But from the blood, the female receives proteins as building materials for her eggs. Males use only nectar as food, refraining from parasitism. It has been proven by science that some types of mosquitoes can use the blood of birds, reptiles, and even fish as food!
Leeches
These relatives of the earthworm also prefer blood as a food. Sucking it, they parasitize at the expense of other organisms. Leeches detect a victim by body temperature or by smell. Then they suck, biting the skin with the three available jaws. Their saliva is so adapted by nature that it gives an analgesic effect and prevents blood clotting.
Lampreys
They are the parasites of fish. With its mouth, lamprey is attached to the body of the fish, stripping the skin. So she has the ability to suck blood and other fluids from the wound. When the saturation process occurs, the lamprey falls off from the wound and sinks to the bottom until it is hungry again.
What parasite animals still exist in nature? These include isopod crustaceans. They bite, as a rule, the skin or shell of marine inhabitants and eat in this way, "riding on horseback" on their master.
Nest parasitism
Oddly enough, birds are also parasitic animals. The names of these flying "parasites" include about eighty species and five families. The most famous representative is the cuckoo. She lays her eggs in a strange nest, in this way forcing birds of other species (for example, woodpeckers) to grow cuckoos. And the cuckoo, hatching, throws the woodpecker's eggs out of the nest, eliminating competitors.
Some fish and insects also engage in similar nesting parasitism, using other animals to raise their offspring.