Symbiote (Needle)

Symbiotes are a sapient amorphous species resembling a green gelatinous mass. They are made up of biological units much smaller than cells, more closely resembling viruses; and like a virus they live within the bodies of larger lifeforms, although they are able to survive outside a host, at least for some period of time.

Biology
Unlike most symbionts and parasites; these Symbiotes are highly generalist; able to survive inside many species of lifeforms native to different planets of the galaxy. Once entering a host, they can easily dodge around their natural defense system until they are capable of producing substances that cause the host's body to "accept" them. They can feed on practically anything organic, and would horribly kill the host if they acted on instinct alone. It is rather their intelligence and moral code that allows them to act symbiotically, and not parasitically.

Culture and society
For a number of spacefaring species, hosting Symbiotes is socially normal. They associate with a lifelong host with which they share a friendly relationship. They will feed on germs and other hazardous agents, take their share of nutrients and oxygen without causing damage to the host, and act like an efficient medical system capable of healing or alleviating many sorts of physical damages and diseases.

Like practically all species, however, criminals exist in their society, being particularly dangerous for their ability to live within a host for decades undetected. Symbiotes can communicate with their host through a number of ways. Usually they will decide upon joining which way is more comfortable to their host. When in direct contact with each other, Symbiotes can communicate using a complex chemical language, described as capable of higher levels of significance and nuance than most verbal idioms.

Appearances

 * Needle, by Hal Clement (1950)
 * Through the Eye of a Needle, by Hal Clement (1978)