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The crustacean (Malacostraca) order Decapoda is is composed of two suborders, only one of which occurs in fresh waters: Pleocyemata. The suborder is divided into 7 infraorders, with four representatives in non-marine habitats: Anomura, Brachyura, Caridea, and Astacidea. Of these, only the latter two inhabit in-land waterways in North America.

The crayfishes and lobsters comprise the Astacidea. There are c. 780 species of astacideans worldwide in marine and freshwater habitats, of which the non-marine crayfish comprise 640 species (33 genera, 3 families). The majority of these species occur in North America, with different assemblages east and west of the continental divide. In total, there are 382 Nearctic species in 12 genera in 2 families (Crandall & Buhay, 2008). The rest of the North American freshwater decapods are represented 17 species (5 genera, 3 families) of caridean shrimps (De Grave et al., 2008).

The brachyuran crabs are well represented in global fresh waters (including Central and South America), but only tangentially relevant to North American freshwater invertebrates. Of the truly freshwater brachyuran families, only one, Pseudothelphusidae, makes it as far north as the High Plateau of Mexico (Yeo et al., 2008). Other genera are found in brackish waters, but they are absent from in-land waters. Freshwater anomurans are represented by only a single genus in southern South America (Bond-Backup et al., 2008).

Decapods are large (cm-dm length) and among the best recognized freshwater crustaceans. Because they are common exemplars in introductory zoology labs, their morphology is often regarded as “typical.” The Decapoda has earned its name by its 5 pairs (= 10) of pereopods (walking legs). The five appendages of the head augmented by three maxillipeds from the thorax. The five (of 8) remaining thoracic appendages are the pereopods. In crayfish, the first pereopods are well-developed with chelae. The head and pereon (thorax) are covered dorsally by a large carapace. The pleon (abdomen) bears 5 pairs of pleopods (swimmerets) and a pair of uropods. The latter, with the telson, forms the tail fan. The head bears stalked compound eyes. These crustaceans are generally omnivores. Decapods are gonochoristic (often with strong dimorphism), and reproduction is almost exclusively sexual. Fertilize eggs are cared for by the female, and development is direct.

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Bibliography

• Hobbs, H.H. & D.M. Lodge. 2010. Decapoda. [in] J.H. Thorp & A.P. Covich (eds.). Ecology and Classification of North American Freshwater Invertebrates, 3rd edition: 901-967.
• 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.
• Yeo, D.C.J., P.K.L. Ng, N. Cumberlidge, C. Magalhães, S.R. Daniels & M.R. Campos. 2008. Global diversity of crabs (Crustacea: Decapoda: Brachyura) in freshwater. Hydrobiologia 595: 275-286. [Available online]
• De Grave, S., Y. Cai & A. Anker. 2008. Global diversity of shrimps (Crustacea: Decapoda: Caridea) in freshwater. Hydrobiologia 595: 287-293. [Available online]
• Crandall, K.A. & J.E. Buhay. 2008. Global diversity of crayfish (Astacidae, Cambaridae, and Parastacidae — Decapoda) . Hydrobiologia 595: 295-301. [Available online]
• Smith, D.G. 2001. Decapoda (Crayfishes, shrimps). Pennak's Freshwater Invertebrates of the United States, 4th edition: 585-608.
• 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.
• Strenth, N.E. 1976. A review of the systematics and zoogeography of the freshwater species of Palaemonetes Heller of North America (Crustacea: Decapoda). Smithsonian Contributions to Zoology (228): 1-27. [Available online]
• Hobbs, H.H., jr. 1972. Crayfishes (Astacidae) of North and Middle America. U.S. Environmental Protection Agency, Biota of Freshwater Ecosystems Identification Manual 9. 173 pp. [Available online]
• Chace, F.A., jr., J.G. Mackin, L. Hubricht, A.H. Banner & H.H. Hobbs, jr. 1959. Malacostraca. [in] W.T. Edmondson (ed.). Ward & Whipple Fresh-Water Biology, 2nd edition: 869-901.

Student Essays

• "Cambaridae and Applied Interest of Invasive Introductions" by Amber Honadel (BIOL/WATR 361, Fall 2013 )
• "The Rusty Crayfish" by Thomas Farley (BIOL/WATR 361, Fall 2013 )
• "Orconectes rusticus (Rusty Crayfish), an invasive species in the native waters of Wisconsin" by Austin Cumber (BIOL 490, Fall 2014 )
• "Importance and Life History of Palaemonetes spp." by Ryan Gibson (BIOL/WATR 361, Fall 2013 )

Web Pages

• Animal Diversity Web
• Decapoda AToL
• Integrated Taxonomic Information System
• Tree of Life
• WikiSpecies
• Wikipedia
• World Register of Marine Species