Commensalism is a biological relationship in which one species benefits from the interaction while the other species is neither helped nor harmed. The species that benefits, known as the commensal, may gain nutrients, shelter, support, or locomotion from the host species, which remains unaffected by the relationship. This interaction is distinct from mutualism, where both species benefit, and parasitism, where one benefits at the expense of the other.
Key Characteristics of Commensalism
- One species gains a benefit such as food, shelter, or transportation.
- The other species (the host) experiences no significant positive or negative effect.
- Often involves a larger host and a smaller commensal species.
- The commensal species may develop adaptations for the relationship, whereas the host remains largely unchanged.
Examples of Commensalism
- Remoras attaching to sharks to feed on leftover food without affecting the shark.
- Birds like egrets feeding on insects stirred up by grazing mammals.
- Orchids growing on tree branches to access sunlight without harming the tree.
- Emperor shrimp riding sea cucumbers for protection and transportation while the sea cucumber is unaffected.
- Arctic foxes following caribou to catch small prey unearthed by the caribou’s movements.
The term "commensalism" originates from the Medieval Latin word meaning "sharing a table," reflecting the idea of sharing resources without harm. It is a form of symbiosis, though unlike mutualism, commensalism involves benefit to only one party without impact to the other.
