Commensal

The fish (AMPHIPRION PERCULA) "intel-intel" of the blacks, is said to be commensal (literally, dining at the same table with its host), as distinguished from the parasite, which lives on its host.

Source: wiktionary

With this there is also associated the grazing or herding over wider or more restricted areas, belonging either collectively or discretely to the community, of sheep, cattle, goats, or swine, and almost always the domestic fowl is commensal with man in this life.

Source: wiktionary

The tree did indeed grow right out of the algae, as I had seen from the lifeboat. There was not the least trace of soil. Either there was soil deeper down, or this species of tree was a remarkable instance of a commensal or a parasite.

Source: wiktionary

Colville ordered it, and was sorry when the last of his commensals, slightly bowing him a good-night, left him alone to it.

Source: wiktionary