Symbiosis in fiction

Symbiosis (mutualism) appears in fiction, especially science fiction, as a plot device. It is distinguished from parasitism in fiction, a similar theme, by the mutual benefit to the organisms involved, whereas the parasite inflicts harm on its host. Early science fiction mostly depicted parasitic relationships, with symbiotic ones gaining prominence following World War II alongside the emergence of more positive depictions of aliens in general. The distinction between parasitism and symbiosis is not always clear-cut, and several works depict associations that start out parasitic and become symbiotic or vice versa, relationships with traits of both types, or one kind being mistaken for the other.

The most common type of symbiosis in science fiction is between humans and alien species, though there are also examples between humans and microbes, humans and plants, humans and artificial life forms, and between two or more non-human species. A common theme involves symbionts accessing the mind of their host; an analogous psychic counterpart without physical attachment also appears, especially in fantasy. In a more extensive variation, the psychic kind of symbiosis forms what is known as a gestalt or hive mind. On an even larger scale, some works depict entire planetary ecospheres in symbiosis—a concept related to the Gaia hypothesis, which posits that all life on Earth functions as a single organism.