Killer whales have symbiotic relationships with barnacle and small fish, called cleanser fish. These relationships may be symbiotic or commensal, which means one species benefits from the relationship, while the other is neither harmed nor benefited. These relationships offer unique advantages to whales, including preventing disease.
Barnacles grow on whales' outer skins, which gives them a habitat in which to live, and protects them from potential predators. Many types of barnacles exist, and different species of whales are identified based on the type of barnacle growing on their skin. Although whales do not always benefit from barnacle attachments, they derive distinct benefits from partnering with small fish. These critters feed on the small particles that attach to whales, namely fungi and bacteria, which may cause harm. Both species benefit, as the fish obtain food and nutrition, and whales stay healthy. Fish may also relieve whales of damaged and dying tissue.
Like other organisms, however, whales can be involved in parasitic relationships too, which cause them harm. Lice may infect whales, causing a host of health problems, according to pbs.org. Lice, which live outside whales, may pose problems primarily in quantity. As with barnacles, different species of whales may be identified based on the type of lice covering their outer skins.