Acarids

An acarid is that alive being that live and you are nurtured to another alive being's expenses without contributing any benefit to this I finish. This alive other being, receives the hospedador (sometimes, in confused way, guest) name to expenses from which the acarid is nurtured, being able to take place in some cases damage or injuries.

Definition
In a precise definition, we can summarize that you are metabolically a relationship simbiótica anisoespecífica (among different species) in which the acarid is dependent of your hospedador and you are not beneficial for this. Nevertheless, from an ecologic point of view, the definition of the term can be expanded considerably.

Although parasitism usually involves a relationship trófica, the acarid he/she can also obtain other benefits of your hospedador like protection in front of predators or competitors. Also, they can benefit of parental cares. The reproductive acarids, as some African fish winch of the family synodontidae, make that other fish ciclidos that habitually incubate your eggs in the mouth, also protect the petty fish winch next to your own breedings. These fish, although they don't feed the breedings of the sinodontidos, they protect them and they defend in front of other fish.

Also, it can be said that a hospedador doesn't always nurture to the copy that the parásita, it can also nurture your eggs or breedings. This way, the most important relationship cannot be trófica, although these cases are enough isolated.

Lastly, you are important to say that the acarids usually cause always some nuisance value to your hospedador in general ledger or pettier grade, although you are sometimes impossible to discern the parasitism of the comensalismo and they don't lack examples of parásitismos that can produce to have some positive effect on the hospedador in spite of being pathogen clear agents. You are believed that in this relationship it can evolve, throughout many generations of acarids and hospedadores, toward a mutually beneficial (mutualismo) symbiosis.

Classification
Microparasitos and Macroparasitos Exist. The first are petty and extremely numerous. They multiply inside the guest and in general they make it inside the guest's cells, therefore they are related with the metabolism and they cause reactions on the part of the antibodies. Macroparasitos grows, but they don't multiply inside the guest. They produce infectious phases that leave outside of the guest, to affect others. They live inside the body or in the cavities of the affected one for the acarids and in general, it can be considered the I number of existing macroparasitos in the affected organism. The parasitism involves a relationship trofica with your guest (obtaining of nutritious) but it can also involve other relationships as you are it that of protection on the part of this I finish.

Types of acarids
Many types of acarids exist. Among them they are:

* The viruses
* The bacteria
* The mushrooms
* The plants
* The protozoa
* The helminths
* The arthropods
* The algae

Attending the place occupied in the body of the hospedador, the acarids can be classified in:

* ectoacarids: They live in contact with the exterior of your hospedador (for example the flea)
* endoacarids: They live inside the body of your hospedador (for example a taenia or a trichina)
* mesoacarids: They possess a part of your body looking toward the exterior and another anchored deeply in the tissues of your hospedador. In some extreme cases of mesoacarids of fish (copepods pennellidae), they can have the head inserted in the heart of your hospedador and to extend for the arteries until the gills, or to perforate the visceral cavity.

Parasitology
The science that he study the acarids is the parasitología, as well as the biologic interaction between two species, acarid and hospedador, you are named parasitism. Since most of the microorganisms that produce infections are studied by the microbiology, the parasitología takes charge of studying exclusively to the acarids eukaryotes except the mushrooms. That is to say, so much the one-celled eukaryotes of the polifilético group Protozoa, as the pluricelulares (metazoos) that include to platelmintos, nematodes, arthropods, etc.

In occasions, you are díficil to differentiate the phenomenon of the parasitism of the comensalismo, the symbiosis, the foresis, or the pillaging, since the distinctions among these they vary from an author to another.

One of the features common of the parasitism is that you bear an exchange of substances that they cause in the hospedador an immunologic answer.

An inmunoevasión petition for the acarid is the one of forming antigens that resemble those of the guest (mimicry). Other, you are the one of sticking antigens from the hospedador to the extraneous surface of the body of the acarid (camouflage antigénico); Other, you are the petition of going constantly varying and quickly your surface (antigens) proteins so that the antibodies taken place by the guest cannot recognize it; the result is that the invaded hospedador doesn't recognize to the acarid like invasive or the answer that this takes place you are not completely actual.

Another feature of the parasitism is that although the acarid should adapt to the answer inmunitaria and, in general, to the parasitic life, the hospedador also debit side to make it. This is because the population parásita exercises a selective pressure in this, so guest and hospedador coevolucionan parallelly as a consequence of the parasitism. This explains, for example that the gene of the falciform anaemia is very frequent in endemic fields of malaria.

Almost all the important groups of animals possess some species parásitas. Some quite unexpected ones. For example besides the good known groups of acarids (monogéneos, digéneos, cestodes, nematodes, hirudíneos, copepods) among the acarids some species of barnacles can be included, clams, turbelarios, hidrozoos, birds like the cuckoo... and even some sharks.