A new species of Stygobromus Cope, 1872 (Amphipoda, Crangonyctidae) from a hypotelminorheic seepage spring in Washington, D.C., USA

We describe a new species of subterranean amphipod (Amphipoda: Crangonyctidae) in the genus Stygobromus from a hypotelminorheic seepage spring at Shepherd Parkway, part of National Capital East Parks, Washington, D.C., USA, part of the National Park System, using both morphological and genetic approaches. The Anacostia Groundwater Amphipod, S. anacostensissp. nov. is a member of the S. tenuis species group but differs from related congeners based on body size, serrate blade-like edge of both palms of gnathopods 1 and 2, presence of rastellate setae on the posterodistal margin of the carpus of gnathopod 2, and aspects of the second antennae, mandibular palp, pereopods 5–7, uropods 1 and 2, and telson. Moreover, S. anacostensissp. nov. is genetically distinct from S. tenuis in the Washington D.C. metropolitan area. The description of S. anacostensissp. nov. increases the number of described Stygobromus species to eight in the Washington D.C. area and highlights the need for continued biodiversity studies, even in regions that have received considerable attention.