Commensals

Commensals are organisms that live in a close, often prolonged, relationship with another organism of a different species, where one organism benefits (the commensal) and the other is neither significantly harmed nor helped. This relationship, known as commensalism, contrasts with parasitism (where one organism benefits at the expense of the other) and mutualism (where both organisms benefit). The commensal derives sustenance, shelter, or transport from the host without inflicting any apparent damage. The association is typically more casual than that of symbiosis, though in some cases it could lead to dependence. The type of relationship can vary. The interaction can be obligatory (the commensal cannot survive independently), or facultative (the commensal can survive independently).

Commensals meaning with examples

• Barnacles on whales are a classic example of commensalism. The barnacles gain a mobile home and access to food sources in the water column without affecting the whale. The whale is unbothered by the barnacles. This relationship benefits the barnacles in several ways, providing them with movement to new feeding grounds and protection from predators. The whale's size allows it to easily move through these areas. It's an example of a situation where one benefits, and the other isn't affected.
• Many bird species exhibit commensal behavior by following herds of grazing animals, such as cattle or elephants. As these large animals move through grasslands, they stir up insects. The birds then swoop in to consume these insects, taking advantage of a readily available food source. The grazing animals are generally unaffected by the presence of the birds. The birds have an advantage. The grazers are not affected by the presence of the birds.
• Certain microorganisms residing in the human gut can be considered commensals. They utilize undigested food or byproducts from the digestive processes for their own nourishment. While providing no direct benefit to the host, nor harming the host, these microbes can contribute to the overall health and stability of the gut environment by contributing to a complex balance. The host neither gains nor loses.
• Remora fish attaching themselves to sharks represent another common instance of commensalism in the marine environment. The remora fish are able to hitch a ride and benefit from the shark’s feeding behavior, consuming scraps left over from its prey. The shark is generally indifferent to the presence of the remora. In this scenario, the remora receives transport and access to food.