Ectozoan

Part of speech: noun, adjective

Definitions

1. A parasitic organism that lives on the outside of an animal's body rather than inside it
2. An animal that feeds externally as a parasite, inhabiting the skin or surface of a host
3. A creature that exists as an external parasite on the body of another animal

Etymology: Ectozoan is a term for an organism that lives on the outside of another, such as a flea or tick on a mammal's skin. It is a technical coinage built from two Greek parts: "ektos", meaning "outside", and "zoion", meaning "animal" or "living being". The same pattern gives "endozoan" for an organism living inside another, and the pair belongs to the parasitology and zoology vocabulary of the 19th and 20th centuries rather than to ancient Greek usage, since the Greeks had no such combined term. The "ecto-" prefix is itself a scientific borrowing that turns up in many modern words, such as "ectoderm", the outer layer of cells in an embryo, and "ectoplasm". Its partner "endo-", from Greek "endon" meaning "within", works the same way. Scientists assembled these prefixes from classical roots whenever they needed precise labels for location, so "ectozoan" describes a position in relation to a host and nothing more.

Synonyms: ectozoon, external parasite