The Elusive Delta Hydrobe (Probythinella emarginata) in Kansas

The delta hydrobe (Caenogastropoda-Rissooidea: Hydrobiidae: Probythinella emarginata) was first collected in Kansas in 2001. Previously it was only known from the Pleistocene fossil record. Three live individuals were collected in Cedar Creek, Chase County during Kansas Department of Health and Environment macroinvertebrate surveys in June 2001. Subsequent surveys throughout Cedar Creek in 2010 yielded poor results and only two live individuals were collected. Surveys throughout selected streams in southeastern Kansas in 2011 yielded only one additional population in the Elk River, Montgomery County, Kansas. We resampled and re-evaluated the Cedar Creek and Elk River delta hydrobe populations in May through August 2020 using the same approach as previous surveys. No live individuals were collected. We searched additional perennial streams throughout the Verdigris River basin for the delta hydrobe. We collected few weathered shells but no live individuals were observed. We provide a comprehensive summary of all delta hydrobe shell collections in Kansas. This Pleistocene relic is elusive and likely imperiled in the state. Future surveys should use environmental DNA sampling approaches to more efficiently survey for presence of the delta hydrobe.