Ectosymbiosis

Ectosymbiosis is a form of symbiotic behavior in which an organism lives on the body surface of another organism (the host), including internal surfaces such as the lining of the digestive tube and the ducts of glands. The ectosymbiotic species, or ectosymbiont, is generally an immobile (or sessile) organism existing off of biotic substrate through mutualism, commensalism, or parasitism. Ectosymbiosis is found throughout a diverse array of environments and in many different species.

In some species the symbiotic environment provided by both the parasite and host are mutually beneficial. In recent research it has been found that these micro-flora will evolve and diversify rapidly in response to a change in the external environment, in order to stabilize and maintain a beneficial ectosymbiotic environment.