The nature of the symbiosis between Indo-Pacific anemone fishes and sea anemones

Under the general heading of symbiosis, defined originally to mean a living together of two dissimilar species, exist the sub-categories of mutualism (where both partners benefit), commensalism (where one partner benefits and the other is neutral) and parasitism (where one partner benefits and the other is harmed). The sea anemone-fish (mainly of the genus Amphiprion) symbiosis has generally been considered to benefit only the fish, and thus has been called commensal in nature. Recent field and laboratory observations, however, suggest that this symbiosis more closely approaches mutualism in which both partners benefit to some degree. The fishes benefit by receiving protection from predators among the nematocyst-laden tentacles of the sea anemone host, perhaps by receiving some form of tactile stimulation, by being less susceptible to various diseases and by feeding on anemone tissue, prey, waste material and perhaps crustacean symbionts. The sea anemones benefit by receiving protection from various predators, removal of necrotic tissue, perhaps some form of tactile stimulation, removal of inorganic and organic material from on and around the anemone, possible removal of anemone parasites, and by being provided food by some species of Amphiprion.