hostcommensal

A hostcommensal is an organism that lives in or on another organism, known as the host, and benefits from this relationship without causing harm to the host. This type of symbiotic interaction is known as commensalism. In a commensal relationship, the commensal organism typically derives nutrients, shelter, or transportation from the host. The host, in turn, is neither significantly helped nor harmed by the presence of the commensal.

Examples of hostcommensal relationships can be found throughout nature. For instance, certain species of barnacles attach themselves to whales. The barnacles benefit from a stable surface and access to food particles in the water stirred up by the whale's movement. The whale, however, is generally unaffected by the presence of these crustaceans. Another common example involves bacteria that live on human skin. These bacteria, often referred to as the skin microbiome, can derive nutrients from skin secretions. While they do not typically cause disease, they also do not provide a direct benefit to the human host. Remoras, small fish that attach to sharks, are also considered hostcommensals. They benefit from protection and transportation, and their feeding habits on leftover scraps from the shark's meals do not detract from the shark's sustenance. The defining characteristic of hostcommensalism is the one-sided benefit to the commensal organism while the host remains neutral.