Copepods

Copepods are pale or translucent crustaceans, measuring between 0.04 mm to several millimeters long. They have adapted to many different habitats; while they usually live in salt water, copepods can live in lakes and ponds as well. Furthermore, they have different modes of locomotion: some can swim purposefully but others are planktonic, floating with the current. Scientists generally A copepod (Diaptomus sp.). © M.I. Walker/Science Photo Library, National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission. distinguish between two basic forms of copepods, free-living and parasitic.

The phylum Arthropoda is the largest phylum in the animal kingdom, containing more than one million species. Within this phylum, the subphylum Crustacea contains some 35,000 species and can be broken down into eight classes. Copepods belong to the class Maxillopoda and the subclass Copepoda, containing seven orders and more than 7,500 species. Three of these orders—Calanoida, Cyclopoida, and Harpacticoida—are primarily free-living and are present in huge numbers. The other orders are: Misophrioida, Monstrilloida, Siphonostomatoida, and Poecilostomatoida.