Image from An Image-Based Key To The Zooplankton Of North America.

Crustaceans of the subclass Copepoda are found in both marine and freshwater habitats. Globally, there are c. 13,000 species in 10 orders. Almost 350 species (87 genera, 17 families, 6 orders) are known from North American fresh waters (Boxshall & Defaye, 2008).

Copepods are minute crustaceans in the μm-mm size range. The three tagmata of the typical crustacean body plan are recognizable, although the "head" is actually a cephalothorax (cephalosome) because 1-2 thoracic segments are fused to it. The thorax bears biramous appendages, and the abdomen has only a pair of caudal rami. Although trunk segmentation is generally visible, the cylindrical body has a main point of articulation dividing the anterior metasome from the posterior urosome. The shape of the body tagmata in combination with the length of the antennules can be used to distinguish the free-living copepod orders.

Copepods in general are sexually dimorphic, with modifications of the appendages in males for grasping the females and female appendages modified to carry eggs. Development is indirect through a nauplius larval phase.

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Bibliography

• Smith, I.M., D.R. Cook & B.P. Smith. 2010. Water mites (Hydrachnidiae) and other arachnids. [in] J.H. Thorp & A.P. Covich (eds.). Ecology and Classification of North American Freshwater Invertebrates, 3rd edition: 485-586.
• Reid, J.W. & C.E. Williamson. 2010. Copepoda. [in] J.H. Thorp & A.P. Covich (eds.). Ecology and Classification of North American Freshwater Invertebrates, 3rd edition: 829-899.
• Covich, A.P., J.H. Thorp & D.C. Rogers. 2010. Introduction to the Subphylum Crustacea. [in] J.H. Thorp & A.P. Covich (eds.). Ecology and Classification of North American Freshwater Invertebrates, 3rd edition: 695-723.
• Forró, L. N.M. Korovchinsky, A.A. Kotov & A. Petrusek. 2008. Global diversity of cladocerans (Cladocera; Crustacea) in freshwater. Hydrobiologia 595: 177-184. [Available online]
• Boxshall, G.A. & D. Defaye. 2008. Global diversity of copepods (Crustacea: Copepoda) in freshwater. Hydrobiologia 595: 195-207. [Available online]
• Smith, D.G. 2001. Copepoda. Pennak's Freshwater Invertebrates of the United States, 4th edition: 489-517.
• Underhill, J.C., W.D. Schmid & D.E. Gilbertson. 1982. Taxonomic Keys to the Common Animals of the North Central States, exclusive of the parasitic worms, terrestrial insects, and birds, 4th edition. 205 pp.
• Wilson, M.S. & H.C. Yeatman. 1959. Free-Living Copepoda. [in] W.T. Edmondson (ed.). Ward & Whipple Fresh-Water Biology, 2nd edition: 735-861.
• Pennak, R.W. 1940. Ecology of the microscopic Metazoa inhabiting the sandy beaches of some Wisconsin lakes. Ecological Monographs 10(4): 537-615. [Available online]

Web Pages

• Copepoda Web Portal
• Free-Living and Parasitic Copepods (including Branchiruans) of the Laurentian Great Lakes: Keys and Details on Individual Species
• Integrated Taxonomic Information System
• Tree of Life
• WikiSpecies
• Wikipedia
• World Register of Marine Species
• World of Copepods
• Zooplankton of the Great Lakes