ABSTRACT
The Copepoda-small aquatic crustaceans between 0.5 and 5 mm in length-are a large class of Crustacea, with over 12000 species currently known worldwide. Most species are marine. The subclass is divided into ten Orders, four of which live in symbiosis with other organisms or are external parasites; only the larval stages are free-living. Six Orders (Platycopioida, Misophrioida, Calanoida, Harpacticoida, Gelyelloida and Cyclopoida) have free-living adults. The Calanoida and the Cyclopoida are by far the most dominant groups in freshwater and marine zooplankton.
