Five new mussel species reveal how much biodiversity US rivers still conceal.
Researchers from Shedd Aquarium, Arkansas State University and the U.S. Geological Survey used DNA to describe five new freshwater mussel species from rivers in six Southern states, several of them rare.
Scientists from Shedd Aquarium, Arkansas State University and the U.S. Geological Survey (USGS) have described five new species of freshwater mussels from rivers in Missouri, Arkansas, Mississippi, Alabama, Louisiana and Texas. The study appeared in the journal Zootaxa. Over 20 years, researchers snorkeled southern rivers and felt along the bottoms for mussels. Many shells resembled known species, but their DNA showed otherwise. The authors write that several of the new species are rare and confined to single river basins.
Mussels are hard to identify by shell alone. Shells of the same species can be flatter in headwater streams and rounder downstream, and males and females differ. The team clipped small bits of tissue or took swabs, then returned the mussels alive to the water. They sequenced three genes and compared more than 440 shell outlines. Each major river basin held its own genetic lineage. Shell shape reliably identified only one new species, the Tallahatta hickorynut, sorting 88% of specimens correctly.
All five belong to the hickorynut group. The Mobile hickorynut survives only in upper tributaries of the Tombigbee River. The White River hickorynut ranges from the Ozark highlands to the Mississippi floodplain. The Big Thicket hickorynut lives in a few scattered spots in the Calcasieu, Sabine and Neches rivers. The Tallahatta hickorynut is known only from about 16 kilometers (10 miles) of Mississippi's Big Black River. The Acolapissa hickorynut, the largest at about 6.4 centimeters (2.5 inches), lives in the Pearl, Pascagoula and Lake Pontchartrain drainages in Louisiana.
The page cites the USGS in saying freshwater mussels are the most imperiled animal group in North America, with 66% of species at risk. Mussel larvae must attach to host fish, and scientists do not yet know which fish the new species need. Relatives use small bottom-dwellers such as darters and sculpins. Captive rearing programs have helped other mussels, but that work cannot begin for these five until the hosts are identified.
Only the Acolapissa hickorynut has been proposed for federal protection. In 2024, the U.S. Fish and Wildlife Service proposed listing it as threatened under an earlier label, according to the study. The other four have no federal assessments. The authors call for state and federal reviews of all five and suggest the Mobile hickorynut may warrant the same protection as the Alabama hickorynut, which was proposed as endangered. Lead author Kentaro Inoue of Shedd Aquarium said, "Conservation efforts can only protect what we recognize."
At a Glance
- The five new species are hickorynuts from rivers in Missouri, Arkansas, Mississippi, Alabama, Louisiana and Texas, described in Zootaxa.
- The team sequenced three genes and compared more than 440 shell outlines over about 20 years of fieldwork.
- The Tallahatta hickorynut is known only from about 16 kilometers (10 miles) of Mississippi's Big Black River.
- In 2024, the U.S. Fish and Wildlife Service proposed threatened status for the Acolapissa hickorynut, the only one of the five proposed.
- The USGS says 66% of North America's freshwater mussel species are at risk.
Sources
This brief was written by Brightside Report from the reporting linked above. Spot an error? Request a correction.