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A titan triggerfish (Balistoides viridescens)

In ecology, commensalism is a class of relationships between two organisms where one organism benefits from the other without affecting it. This is in contrast with mutualism, in which both organisms benefit from each other, amensalism, where one is harmed while the other is unaffected, and parasitism, where one benefits while the other is harmed.

The word "commensalism" is derived from the word "commensal", meaning "eating at the same table" in human social interaction, which in turn comes through French from the Medieval Latin commensalis, meaning "sharing a table", from the prefix com-, meaning "together", and mensa, meaning "table" or "meal".[1] Originally, the term was used to describe the use of waste food by second animals, like the carcass eaters that follow hunting animals, but wait until they have finished their meal.[citation needed]

Commensalism, in biology, is a relation between individuals of two species in which one species obtains food or other benefits from the other without either harming or benefiting the latter. The commensal (the species that benefits from the association) may obtain nutrients, shelter, support, or locomotion from the host species, which is substantially unaffected. The commensal relation is often between a larger host and a smaller commensal; the host organism is unmodified, whereas the commensal species may show great structural adaptation consonant with its habits, as in the remoras that ride attached to sharks and other fishes. Both remoras and pilot fishes feed on the leftovers of their hosts’ meals. A commensal relation based on shelter is seen in clown fishes (Amphiprion percula), which live unharmed among the stinging tentacles of sea anemones, where they are protected from predators.[citation needed] Numerous birds feed on the insects turned up by grazing mammals, while other birds obtain soil organisms stirred up by the plow.[citation needed] Various biting lice, fleas, and louse flies are commensals in that they feed harmlessly on the feathers of birds and on sloughed-off flakes of skin from mammals[citation needed]

Pierre-Joseph van Beneden introduced the term "Commensalism" in 1876.[2]

Examples of commensal relationships[edit]

Commensalism is harder to demonstrate or explain than parasitism and mutualism, as it is easier to show a single instance in which the host is affected than it is to disprove that possibility. One example is a whale and barnacles.[citation needed] Another is the titan triggerfish (Balistoides viridescens) which creates feeding opportunities for smaller fish by moving large rocks too big for them to shift themselves.[citation needed] Yet another example is the remora, which eats leftover food from a whale and "hitches a ride".[citation needed] Another example of a commensal relationship is the relationship between Cacique birds and the wasp Polybia rejecta.[citation needed]However, the best example for this is of a vulture and a lion. Once the lion has finished its meal, the vulture swoops down and finishes off the carcass. The lion is not affected by this while the vulture gets to eat.


Whether the relationship between humans and some types of our gut flora is commensal or mutualistic is still unanswered.

Some biologists argue that any close interaction between two organisms is unlikely to be completely neutral for either party, and that relationships identified as commensal are likely mutualistic or parasitic in a subtle way that has not been detected. For example, epiphytes are "nutritional pirates" that may intercept substantial amounts of nutrients that would otherwise go to the host plant.[3] Large numbers of epiphytes can also cause tree limbs to break or shade the host plant and reduce its rate of photosynthesis. Similarly, phoretic mites may hinder their host by making flight more difficult, which may affect its aerial hunting ability or cause it to expend extra energy while carrying these passengers.


Phoretic mites on a fly (Pseudolynchia canariensis)
Phoresy, a pseudoscorpion on the leg of a crane fly

Like all ecological interactions, commensalisms vary in strength and duration from intimate, long-lived symbioses to brief, weak interactions through intermediaries.


Phoresy is one animal attached to another exclusively for transport, mainly arthropods, examples of which are mites on insects (such as beetles, flies or bees), pseudoscorpions on mammals[4] or beetles, and millipedes on birds.[5] Phoresy can be either obligate or facultative (induced by environmental conditions).


Inquilinism is the use of a second organism for permanent housing. Examples are epiphytic plants (such as many orchids) that grow on trees,[6] or birds that live in holes in trees.


Metabiosis is a more indirect dependency, in which one organism creates or prepares a suitable environment for a second. Examples include maggots, which feast and develop on corpses, and hermit crabs, which use gastropod shells to protect their bodies.

See also[edit]

  • Symbiosis – long-term interactions between different biological species, which can be mutualistic, commensal or parasitic
  • Mutualism – where both organisms experience mutual benefit in the relationship
  • Parasitism – where one organism benefits at the expense of another organism.


  1. ^ Harper, Douglas. "commensalism". Online Etymology Dictionary. 
  2. ^ van Beneden, Pierre-Joseph (1876). Animal parasites and messmates. London, Henry S. King.[page needed]
  3. ^ Benzing, D.H. (1980) Biology of the Bromeliads. Eureka, California: Mad River Press.[page needed]
  4. ^ Durden, Lance A. (June 1991). "Pseudoscorpions Associated With Mammals in Papua New Guinea". Biotropica 23 (2): 204–6. doi:10.2307/2388309. JSTOR 2388309. 
  5. ^ Tajovský, Karel; Mock, Andrej; Krumpál, Miroslav (2001). "Millipedes (Diplopoda) in birdsˈ nests". European Journal of Soil Biology 37 (4): 321–3. doi:10.1016/S1164-5563(01)01108-6. 
  6. ^ C. Michael Hogan. 2011. Commensalism. Topic Ed. M.Mcginley. Ed-in-chief C.J.Cleveland. Encyclopedia of Earth. National Council for Science and the Environment. Washington DC

External links[edit]

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Commensalism — Please support Wikipedia.
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196 news items

Wed, 06 May 2015 02:11:15 -0700

First, we investigated whether there is habitat partitioning between the two species in the context of commensalism. Further, using mitochondrial and nuclear microsatellite markers, we tested (a) if genetic differentiation is higher and migration rates ...

Above the Law

Above the Law
Sat, 05 Sep 2015 06:25:31 -0700

The impetus behind the exodus might be insignificant, but the partnership arrangement between firm and lawyer is predicated on mutualism and a weakening of a firm's platform — whether it be real or perceived — shifts this dynamic towards commensalism ...
The Navhind Times
Sat, 26 Sep 2015 13:15:00 -0700

In the same year he published a report on the characteristics and identification of the yeasts living in commensalism in the intestine of some laboratory animals and followed it by a report on experimental studies on diets deficient in vitamin B and ...


Fri, 21 Aug 2015 06:03:24 -0700

Additionally, remoras can rub their hosts raw, potentially opening them up to infection—not exactly the civilized behavior required of commensalism or mutualism. Kenaley has also run models that show remoras significantly slow down their hosts.
Wed, 01 Jul 2015 06:06:11 -0700

Unbeknownst to most landlubbers, polychaetes rule the seas. There are at least 10,000 species of these swimming bristly worms, some of which pop with brilliant colors or light up with a bioluminescent glow. They've adapted to every imaginable marine ...

The Guardian

The Guardian
Sat, 15 Aug 2015 16:05:37 -0700

Richard Madden as Mellors and Holliday Grainger as Lady Chatterley in the new production. Photograph: Robert Viglasky/BBC Pictures/Hartswood Films. Jamie Doward. Saturday 15 August 2015 19.05 EDT. Share on Facebook · Share on Twitter · Share via ...

The Guardian (blog)

The Guardian (blog)
Thu, 30 Jul 2015 06:05:26 -0700

The menu was put together according to the different types of symbiotic relationship: mutualism (a relationship which is mutually beneficial to both organisms); commensalism (in which one organism benefits and the other isn't significantly harmed or ...
Christian Science Monitor
Wed, 04 Mar 2015 06:15:00 -0800

When one benefits and the other is neither helped nor harmed it is commensalism. And when one organism is helped while the other suffers it is parasitism. What most fish and sea mammals see as a predator, the remora fish sees as a home. The remora ...

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