Symbion is a genus of commensal aquatic animals, less than 0.5 mm wide, found living attached to the mouthparts of cold-water lobsters.

Symbion pandora was discovered in 1995 by Reinhardt Kristensen and Peter Funch[2] on the mouthparts of the Norway lobster (Nephrops norvegicus).

There are three basic life stages: Symbion reproduces both asexually and sexually, and has a complex reproduction cycle, a strategy evolved to produce as many offspring as possible that can survive and find a new host when the lobster they live on sheds its shell.

During the autumn they make copies of themselves, where a new individual grows inside the parent body, one offspring at the time.

The new offspring attach themselves to an available spot on the lobster, begin to feed and eventually start making new copies of themselves.

By late winter, when the large feeding individuals in the colony have males attached to their bodies, they start making females.