What Is Commensalism?

Commensal shrimp get their names from their tendency to have commensal relationships with other organisms.


This is a term in ecology that refers to a relationship between organisms in which one of the organisms gains from the other without harming the latter. It is opposite of mutualism where both organisms benefit from each other and amensalism in which the benefiting organism harms the other.

The term “commensalism” coming from “commensalis” is a Medieval Latin word meaning table sharing. “Com” is a prefix that means together while “mensa” means table/meal” hence the term.

In biology, commensalism is a relationship between two species whereby one of the species is obtaining benefits without causing any harm or benefit to the other species. The benefiting species can be called the commensal. In this case, the commensal way smaller than the species from which it is benefitting, with the latter being unmodified. The benefits can range from shelter, nutrients, support, support to locomotion. An example is the Remora which rides on the back of sharks. As if that is not enough, the remora feeds on remains of their hosts’ meals, a trait they share with pilot fish. Many birds feed on worms that have been exposed by a plough.

Types Of Commensalism

Animals And Man

There are very many examples of commensalism in the modern day. Using man as an example, the relationship between man and dogs and cats is a commensal relationship. The two animals, dogs and cats, do not harm humans in any way, but they benefit from him. They get food, they get shelter, locomotion and of course treatment. Man on the other hand does not benefit whatsoever from these animals. These animals lived by preying on waste around man habitats hence established the commensal relationship. They later became closer to human beings.

Relationship Between Bacteria/fungi And Man

There are also many bacteria and fungi that have a similar relationship with man. They live in or on the human body, turning to be part of the body’s natural flora. Aspergillus is a fungal genus that is known to colonize the human body's upper gastrointestinal tract without harming the individual. There are different types of commensalisms. These vary in strength and duration of the relationships. They include;

  • Phoresy. In this sort of commensalism, one organism is attached to the other mainly for transport. This trait is chiefly witnessed with anthropods. Examples include mites on insects like beetles, flies or bees, millipedes on birds and pseudoscorpions on mammals.
  • Inquilinism. This is the use of a second organism for permanent housing. A good example is a bird that lives in a hole on a tree or an epiphytic plant (like an orchid) which grows on a tree.
  • Metabiosis- This is a rather more indirect dependency. In this relationship, one organism prepares or creates a suitable environment for the other organism. These are instances like where maggots feast and develop on corpses or hermit crabs that use gastropod shells as protection of their bodies.

More in Environment