Commensalism is a relationship between two species in which one species gets benefit from the relationship but the other remains unaffected. It is one of the five types of symbiosis viz., Mutualism, Parasitism, Commensalism, Synnecrosis, and Amensalism. Symbiosis can be any type of a long-term relationship between two different species.
The species which gets the benefit is called the commensal and it gets may get support, shelter, nutrients or locomotion from the host species. The commensal species is usually smaller than the host species. This relationship is in contrast to mutualism or parasitism in which both species are affected.
However, some biologists are of the view that true commensalism does not exist or the effects on the host is imperceptible. Others argue that once the commensalism between two species is thoroughly studied it will be found to be parasitism or mutualism.
Types of Commensalism
Scientists classify commensalism into four main types:
Chemical commensalism mostly occurs between bacterial species when chemicals produced by host species (which are not useful for itself) are used as food by the other species (commensal).
Metabiosis occurs when a species unintentionally makes a shelter for some other species. Metabiosis also involves one species using something created by another species after its death.
Inquilinism is an association between two individuals of different species in which one lives in or on other’s body and gets shelter and sometimes food without harming it.
Phoresy occurs when one species attaches to the other’s body for transportation.
There are many examples of commensalism, however, a few of them are given below.
Anemonefishes live between the tentacles of anemones to protect themselves from predators which get poisoned by the nematocysts on sea anemones.
Barnacles attach to whales or the shells of mollusks for transportation and safety.
Cattle egrets live where there are cattle so they get insects for food which are stirred up by the movement of cattle.
Golden jackals which are not in packs follow the tigers and feed on what is left by them after predation.