Page last updated
Wed 1 October 2025

The Freshwater Mussels (Unionoida) of the World (and other less consequential bivalves)

FM(U)otW(aolcb) is the web version of the MUSSEL Project Database. Follow the links to browse the data or use the custom Google search field. Either way, you win!

Geographical Summary

We currently list 997 species (216 genera) of freshwater mussels worldwide. This diversity, however, is not randomly distributed. Based on the geographical distributions of the taxa, we have divided the mussel-inhabited continents of the Earth into seven regions, most with multiple subregions. Each region is depicted in the map below. Areas in gray are without mussels.

• North America — North America includes all of Canada and the USA, south to the Mexican Plateau. It is divided into five subregions. Total richness: 307 species, 68 genera.
• Central America — Central America is composed of only a single subregion that includes Mexico south the the Rio Grande Basin, Central America to the Isthmus of Panama, and Cuba in the Caribbean. Total richness: 66 species, 20 genera.
• South America — South America includes all of basins on the continent, from the Caribbean and Pacific basins in the northwest through the Amazon to Tierra del Fuego in the south. The region is divided into six subregions. Total richness: 115 species, 19 genera.
• Afrotropics — Sub-Saharan Africa, the Nile Basin and Madagascar are grouped as the Afrotropics. The region is partitioned into six subregions. Total richness: 81 species, 16 genera.
• North Eurasua — North Eurasia consists of basins from the Europe and Arctic Russia to rivers draining to the Bering Sea and the Sea of Okhotsk, as well as northern Africa and the Middle East. It is subdivided into four subregions. Total richness: 47 species, 10 genera.
• East Asia — Eastern and southern Asia (including the Philippines and much of Indonesia) are treated as East Asia. It is divided among six subregions. Total richness: 365 species, 91 genera.
• Australasia — The Australasian Region is composed of Australia, New Zealand and New Guinea (as well as some smaller islands). The area is subdivided into four subregions. Total richness: 31 species, 10 genera.

For the longest time, it has been established fact that North America has the richest mussel assemblage in the world. However, with the flurry to ecent updates, the title of richest region has passed to East Asia. The other regions are relatively less diverse (especially when their land area is considered). This is presumably due to both the relative habitat instability of those realms and the fact that those areas (outside of Europe) are less well studied.