Epizoan

Part of speech: noun, adjective

Definitions

1. An organism that lives as a parasite on the outer body or skin of another animal
2. A creature that inhabits and feeds on the external surface of a host organism
3. A parasite that attaches to or dwells upon the outside of an animal's body

Etymology: Epizoan is a technical term in zoology for an animal that lives on the outside of another animal, such as a barnacle on a whale or a louse on a bird. It was coined in the 19th century from Greek roots rather than being inherited from classical times, so the Greeks themselves never used it. The first element is "epi", meaning "upon" or "on", and the second is "zoion", meaning "animal" or "living being", which also gives English "zoo" and "zoology" through the shortened form. The pattern follows a set of scientific coinages built the same way, where "epi-" marks a position on or above something, as in "epidermis" (the outer layer of skin) and "epiphyte" (a plant growing on another plant without taking nourishment from it). The contrast word is "endozoan", for animals living inside another. Because the term belongs to the specialised vocabulary of biology, it appears mainly in scientific writing rather than everyday speech.

Synonyms: parasite, ectoparasite