The Isopoda are small crustaceans with seven pairs of legs that range in size from 300 micrometres (Microcerberidae) to nearly 50 centimetres (Bathynomus). Their name, which means "like-foot" or similar (iso) and foot (pod), probably comes from the early zoologists' familiarity with the common terrestrial "slaters" or "woodlice" (other names: cloportes, pissebedden, pillbugs, roly-polies, sowbugs). The isopods are diverse, with around 10,309 species found in all ecosystems from the deepest oceans to the montane terrestrial habitats and deep underground in caves or aquifers. Isopods are thought of as dorsoventrally flattened, as in the typical terrestrial slater, and indeed many species fit this morphological stereotype. Isopods from the deep sea and groundwater habitats and parasitic taxa may depart considerably from this typical body plan.

The isopods belong to the well-known crustacean group, the Malacostraca, which includes familiar crustaceans like shrimp, crabs, lobsters and krill. Unlike these malacostracans with an obvious carapace, the isopods lack one. The isopods belong to the Superorder Peracarida, which includes a diverse array of shrimp-like taxa that all brood their young in a pouch between their legs. Isopods are unique among these crustaceans for many reasons. Because they lack a carapace, the gills, which are covered by the carapace in other groups, are absent, so they breathe using specialised lamellar gill-like pleopods ("swimming limbs") on the posterior section of the body. In many terrestrial isopods, the pleopods bear respiratory structures similar to lungs. Internally, the heart is positioned in the posterior section of the thorax to provide increased circulation for the gills. Unlike all other crustaceans, the isopods shed their cuticle (a process called ecdysis) in two steps: "biphasic molting".

This site has the following aims:

To provide sufficient expert knowledge for maintaining the list, we have formed an editorial committee to whom the queries on particular taxa should be addressed.

History of the list

This list began as an initiative of the US National Museum of Natural History, Smithsonian Institution, maintained by the late Brian Kensley and Marilyn Schotte. It grew into a valuable resource for providing nomenclature on the Isopoda: Schotte, M., B.F. Kensley, and S. Shilling. (1995 onwards). World list of Marine, Freshwater and Terrestrial Crustacea Isopoda. National Museum of Natural History Smithsonian Institution: Washington D.C., USA. This list is now reconstructed at, with more detailed information on synonymies and distributions, and a capability to host more information, such as images, original literature, and specimen data. This list will be transferred on a monthly basis back to the Smithsonian site.

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If any data constitutes a substantial proportion of the records used in secondary analyses (i.e. more than 25% of the data are derived from this source, or the data are essential to arrive at the conclusion of the analysis), the editors of the database should be contacted. Contacting us directly may be useful in case additional data may strengthen the analysis or features of the data are important to consider but may not have been apparent from the metadata.


World List of Marine Freshwater and Terrestrial Isopod Crustaceans Editorial Board:

Links to other isopod sites