Five New Freshwater Mussel Species Discovered in Southern U.S. Rivers

Scientists have identified five previously unknown freshwater mussel species living in rivers across the southern United States, revealing that some populations long thought to belong to known species are actually genetically distinct.

The discovery was made through a combination of DNA analysis, detailed shell comparisons and geographic studies. Researchers from Shedd Aquarium, Arkansas State University and the U.S. Geological Survey examined mussels collected from rivers in Missouri, Arkansas, Mississippi, Alabama, Louisiana and Texas.

Five Species Hidden in Plain Sight

The newly described species all belong to the genus Obovaria, a group of freshwater mussels whose members can look extremely similar.

The five species are the Mobile hickorynut, White River hickorynut, Big Thicket hickorynut, Tallahatta hickorynut and Acolapissa hickorynut.

Several of them occupy very limited geographic ranges, with some known only from particular river systems.

DNA Revealed the Differences

Identifying the mussels was difficult because their shells can vary in appearance depending on environmental conditions. Historical misidentifications had also caused different species to be grouped together.

Researchers combined genetic evidence with shell morphology and geographic distribution to determine that the mussels represented distinct evolutionary lineages.

Years of Searching in Rivers

The discovery was built on more than two decades of fieldwork. Researchers and conservation teams spent years wading through rivers, often wearing masks and snorkels while searching muddy and rocky riverbeds for mussels.

Small tissue samples were collected and later analyzed in laboratories, allowing scientists to compare the genetic characteristics of populations from different watersheds.

Why Freshwater Mussels Matter

Freshwater mussels may be easy to overlook, but they play an important role in river ecosystems. They filter water as they feed, removing particles, algae and bacteria from waterways.

Healthy mussel populations can therefore contribute to the ecological health of rivers that support fish, wildlife and communities.

Some of the New Species Are Rare

Several of the newly described mussels are geographically restricted and uncommon. Their official recognition gives scientists a clearer way to monitor their populations and evaluate the condition of the rivers where they live.

Without accurate identification, a species can decline without researchers fully realizing that a separate population is at risk.

A Reminder of How Much Remains Unknown

The discovery shows that even in a region that has been studied for generations, scientists can still uncover previously unrecognized biodiversity.

The researchers say identifying these five species is an important first step toward understanding their populations and developing conservation strategies tailored to the individual river systems where they occur.

Sources

• Zootaxa — “Description of multiple cryptic species of Obovaria Rafinesque, 1819 from the Mississippi Embayment and Gulf coastal rivers of North America” — September 23, 2026.
• Shedd Aquarium — “Five new species of freshwater mussels in southern US uncovered by researchers” — October 1, 2026.
• U.S. Geological Survey — Research on freshwater mussel biodiversity and conservation in the southern United States.