Parasitism – Concept, types and examples

We explain what parasitism is, the types that exist and some examples. Also, what is social parasitism.

Parasitism - Parasite
Parasitism can occur throughout all phases of an organism’s life.

What is parasitism?

Parasitism is a close biological relationship between two organisms of different species, one called a host (that receives or welcomes) and another called a parasite (that depends on the host for some benefit). The parasite lives at the expense of its host, that is, it uses the organism that hosts it to meet its basic needs, allowing it to expand its own survival capacity. In most cases of parasitism, the host is harmed or damaged by the parasite at some point in the cycle.

Parasitism can occur throughout all phases of the life of an organism or only in specific periods. It may also happen that, as the parasite is still an organism, it hosts another specimen. These cases, in which the parasite hosts another parasite, are called hyperparasitism.

Types of parasitism

Mosquito - parasitism - parasite
Ectoparasites are found outside the host’s body.

There are several ways to classify parasites, based on different criteria.

  • Depending on the location of the parasite in the host’s body:
    • Ectoparasites. They are parasites that are outside the host’s body and take advantage of what they find in the outermost layer of the dermis and even consume a little of their blood. For example, fleas and ticks.
    • Endoparasites. They are the parasites that are inside the host. Depending on the species of the parasite, some can cause slight damage and others, very serious. For example, the worms that live in the intestines.
  • According to the level of dependence that the parasite has on the host:
    • Facultative parasite. They are those species of parasites that do not need the host to complete their life cycle since they are capable of another form of life in addition to the parasitic one.
    • Obligate parasite. They are those species of parasites that are totally dependent on their host at all stages of their life cycle and, therefore, cannot live without it.
    • Accidental parasite. They are free-living organisms that, by mistake, reach the interior of an organism that is not their usual host, but despite this they manage to survive.
  • According to the time the parasite stays in its host:
    • Temporary parasites. They are those that only require the host temporarily and to feed.
    • Periodic parasites. They are those that need to pass one of the stages of their life cycle (egg, larva, juvenile or adult) within the host, but then live freely.
    • Permanent parasites. They are those that require the host throughout their life cycle in order to survive.

Examples of parasitism

Parasitisms - Parasites - Termites
Termites usually live in trees and woods.

On our planet there are many examples of parasitism, among them, some of the most common are the following:

  • Fungi. There are species of fungi that are parasites. They usually stay on the feet, nails or skin of animals and feed on keratin, an abundant protein in the epidermis.
  • Mites. They are a large group of ectoparasites, which usually live on the skin and feed on debris such as keratinocytes (dead cells) or secretions.
  • Mistletoes. They are parasitic plants that tend to be found in various species of trees in parts of Europe, America and Africa.
  • Termites. They are insects that usually lodge in trees and in wood used for the construction of houses. They have a great capacity for destruction.
  • The bacteria. They form a diverse and extensive group. They are usually found in water and on land, so they enter the body through food and stay in the digestive system of animals.
  • The virus. They are obligate parasites, since they cannot be considered living beings, and to carry out their functions they need to take advantage of the organism they invade. They frequently enter the body through the digestive or respiratory systems.
  • Amoebas. They are endoparasites, which usually live in the intestines of animals. They feed on the host, so they can cause malnutrition and serious illness.
  • The worms. They tend to lodge in various parts of the host’s body and can take away its nutrients.

Social parasitism

Social parasitism refers to the type of association made by some animal species to obtain some benefit, but that does not directly impact your organism or biology but rather benefits you in your social development. For example, some birds lay their eggs in the nests of other species of birds, so that the latter raise them.

Social parasitism within a community of people exceeds the strictly biological point of view mentioned above and refers to an association of a derogatory type, in which the parasite violates the ethics and morals that predominate in society of the host (that is, it does not obtain directly biological benefits). For example, in some regions, individuals who live with and with their parents until advanced adulthood are considered “parasites”, obtaining the benefit of a life of comfort and fewer worries.