Parasitism is one of the most widespread life strategies in the Animal Kingdom, with at least 20% of animal species parasitic on other organisms. There are taxa composed solely of parasitic beings, such as viruses and acanthocephalans (parasitic worms). These types of organisms live at the expense of other living things, either for their entire lives or for a short time.
In this article on our site we will learn the definition of parasitism, the types and examples that there are, as well as understand what advantages and disadvantages has this lifestyle.
What is parasitism?
Parasitism is a type of symbiosis in which there are two organisms involved. A relationship is created between an organism that is integrated into another organism or external environment. Therefore, we have two protagonists:
- Guest: is harmed, that is, does not obtain any benefit and also suffers damages derived from the relationship.
- Parasite: finds in this relationship his way of survival.
This type of relationship is maintained until one of the two individuals (parasite or host) dies. Each member belongs to a different species, so the parasite needs to live in the host in order to get food, often genetic material to create its own proteins and, moreover, finds its habitat in the host, without which it could not live.
For all this, parasites are organisms that need a close and continuous relationship with a host (of another species), which provides food, digestive enzymes or materialsand encourage it to develop or reproduce.
That is why on many occasions we hear the expression "you are a parasite" applied to human beings, since it refers to behaviors similar to those of this phenomenon where people are interested in others just to get something. This behavior is known as social parasitism
Types of parasitism
There are several ways to classify parasites, below we show you the best known or used according to taxonomy, the location of the parasite or its dependence on its host, for example.
Classification according to taxonomy
Taxonomically, parasites are classified as phytoparasites when they parasitize plants and zooparasites when they infect animals. In parasitology, the science that studies parasites, only zooparasites are treated.
Classification according to dependency level
According to the level of dependency that the parasite may have with its host, we can establish the following classification:
- Facultative parasite: are those species of parasites that are capable of living through another form of life besides the parasitic one.
- Obligated parasite: are those that cannot live outside the host, since they depend totally on it for any stage of development.
- Accidental parasite: are parasites that, by mistake, end up inside an animal which is not their usual host and, despite this, he manages to survive.
- Wandering Parasite: Parasites that live inside animals usually live in a specific organ or tissue. A parasite found in an organ that is not normal is known as a parasite erratic.
Location Sorting
Another form of parasitism is due to the place that the parasite occupies within the host it is occupying. In this case we can talk about:
- Endoparasite: are the parasites that need to live inside the host, such as the heart, lungs, liver or the digestive tube. Many times this happens because the host has antibodies that are related to the parasite because it has numerous other microparasites on it.
- Ectoparasite: they live on the host, never inside. The most basic example is when we see that an animal has laid its eggs in a nest that is not its own, such as skin or hair.
Classification according to time period
Depending on the time the parasite spends parasitizing the host in question, we can refer to:
- Temporary parasites: the parasitism phase is temporary and only occurs on the surface of the animal (host), never inside it. The parasite feeds on the host, on its skin or blood, for example.
- Periodic parasite: the parasite needs to spend one of its life stages (egg, larva, juvenile or adult) inside the host, then live freely.
- Permanent parasite: The parasite must spend its entire life inside or outside the host if it is to survive.
As a result of this relationship, parasites and hosts often carry out coevolution, that is,they alter their behavior to achieve their goal, which will depend on whether they are the occupants of another organism or the occupied. Species evolve and lose or change their physiological functions in order to continue living. On the other hand, we should also mention hyperparasitism , a relationship that occurs when a parasite lives at the expense of another parasite.
Examples of parasitism
Although there is a great variety of examples of parasitism, below we will show which are the most common, among which we also find zoonoses.
- Fleas, ticks, lice and nits: in this case, the parasites live on the animal, in its fur, and not inside of the. If you want to know more about the Types of fleas and how to identify them or the Life Cycle of lice and nits, do not hesitate to take a look at these two articles on our site.
- Fungi: Many species of fungi are parasites found on the nails, feet, or skin of animals and people.
- Termites: Commonly known because they are found in wood and trees, these insects are feared because they destroy everything they come across.
- Bacteria: they are found in the digestive system of organisms and enter them through food and water, although they are also found on earth.
- The mistletoe: although it may not seem like it, there are also parasitic plants and the mistletoe is one of the best examples of this, since it is found in other species from Europe, Africa or America.
- Amoebas: when we talk about this example of parasitism we also refer to endoparasites, since they are found in the intestine. Their diet is based on the host, so they can cause malnutrition.
- Mites: with this example of parasitism we refer to an ectoparasite, which usually feed on dead cells or secretions found in the skin. You may be interested in this article about Mites in cats: symptoms, treatment and contagion.
- Protozoa: These are commonly known parasites in plants and animals that can cause Chagas disease.
- Guinea worm: they inhabit the waters of rivers, so consuming them can be harmful to our he alth.
- Viruses: These are parasites that inhabit and prey on plants, animals and people. They are not considered living beings and enter them through the respiratory or digestive system.
- Other examples of parasitism: we can find the relationship between leeches and the blood of their hosts, who need it to live, or the worms that invade animal and human organs to remove nutrients.
Parasitic diseases
Some of the diseases caused by parasitism are the following:
- Coccidiosis: is a disease caused by a group of protist parasites belonging to the Coccidiasin subclass. Coccidia are obligate intracellular parasites, so they need a host to live, they must also be found not only inside the animal, but inside its cells. You may be interested in this article about Coccidiosis in dogs: symptoms, treatment and contagion.
- Echinocosis or hydatidosis: is another serious disease caused by the relationship between a parasite of the Cestoda class and a mammal, usually livestock, pets or the human being itself. Cestodes are endoparasites of the digestive tract like tapeworms. Its larvae can travel through the blood to other organs such as the liver, producing hydatid cysts.
Advantages and disadvantages of parasitism
Since we already know what parasitism is and the types that exist, now we are going to see what the possible advantages and disadvantages of this biological process are.
Advantages of parasitism
Initially, the animals we know today as parasites had a free lifestyle in the past The fact that in a given moment of evolution these animals acquired a parasitic lifestyle, suggests that they should obtain some kind of benefit.
- The habitat: Animals have mechanisms to maintain homeostasis within their bodies, which gives them the possibility of living in a medium with hardly any fluctuations.
- The Offspring: On the other hand, they have an easy way to distribute their offspring over wide areas quickly. For example, if the parasite releases eggs through the faeces of its host, it is certain that its offspring will develop elsewhere.
- Food: for a parasite, food is always close and available, since it feeds on the host itself or on part of the food it contains. eat.
Disadvantages of parasitism
Not all are advantages for parasitic animals, therefore, here we are going to mention some of the disadvantages of parasitism.
- The remoteness of congeners: the fact of living inside a body means that parasitic congeners are far away, both in space as in time, since they will live in other hosts, so strategies for sexual reproduction must be found and thus be able to combine the genetic material.
- The habitat: although this is also an advantage, as we mentioned before, the host can die, so the habitat It's not forever.
- Host Hostility: As a rule, hosts don't want to be parasitized, so they will be hostile to parasites and try to get rid of them at all costs, for example, through grooming.
