Symbion pandora is a jug-shaped microscopic aquatic animal that dwells on the mouth-parts of Norway lobsters. The animals are less than ½ mm wide, with sac-like bodies, and three distinctly different forms in different parts of their three-stage life cycle.
They are so unlike any known animal that its discovery by Danish scientists in 1995 led to the creation of a new phylum. The phylum Cycliophora, from the Greek for 'carrying a small wheel', was named after the creature's circular mouth. Two other members of that phylum have since been discovered.
Symbion refers to the animal's symbiotic relationship with its lobster host while the specific epithet pandora refers to the part of the organism's life cycle that reminded Funch and Christensen of the mythical Pandora's box.
Symbion pandora has a bilateral, sac-like body with no coelom. There are three basic life stages:
Symbion pandora can reproduce both asexually by budding and sexually. The sexual reproductive cycle is triggered when the host crustacean molts its skin in order to grow: a feeding stage buds a male, which attaches to another feeding stage and triggers it to bud a female, which it impregnates. The female is able to swim, and finds another host crustacean, where the larva in her develops. The female dies, and the larva escapes, spawning another feeding stage on the new host.