Oocysts

Part of speech: noun

Definitions

1. A dormant form of certain protozoa, often resistant to harsh environments
2. Structures that serve as a protective means for parasites during their life cycle
3. Encysted stages that enable survival and transmission in various hosts

Etymology: "Oocysts" is the plural of "oocyst", a noun for the protective capsule that certain parasites form around their eggs, which lets the eggs survive outside a host. The word is built from two parts: "oo-", from the Greek "ōion", meaning egg, and "cyst", from the Greek "kystis", meaning bladder or sac. Put together, the sense is an egg enclosed in a sac, and the pairing is a plain descriptive coinage rather than a word with a long folk history. The "cyst" element is the older and more widely known half. In medicine it has long named any sac-like membrane enclosing fluid or a developing body, which is why the compound follows the same pattern as other biological terms built with "oo-", such as "oosphere" for the egg cell in plants and algae. The formation is an ordinary modern scientific coinage that draws on classical Greek roots, so the word describes a structure its coiners could observe under the microscope rather than one the ancient Greeks themselves named.

Synonyms: cysts, spore cysts