The biodiversity of species in the National Capital Region continues to grow! The latest additions are two tiny crustacean amphipods that live in leafy, woodland seeps. They are relatives of the region’s most famous amphipod—the federally endangered Hay’s Spring amphipod—and join a list of 10 known subterranean amphipod species from in and around the Washington, DC area (Cannizzaro et al. 2026).

New Additions to the Genus Stygobromus

Amphipods are invertebrate animals (with no backbone). The two new species, Stygobromus paveki and Stygobromus scottsruni, are the size of a grain of rice and belong to the most common subterranean amphipod genus in the DC area. 

The Stygobromus genus was described for cave dwelling animals. It is named after the underground River Styx of Greek mythology since the animals of the genus live in moving underground water habitats (caves and forest seeps). They have no need for pigment or eyes since they live in a completely dark environment. Like other genera of amphipods, they eat dead and decaying organic material (leaves, small insects, micro-invertebrates, bacteria, etc.), which cleans the water.

The Project

Scientists from American University, Old Dominion University, the Smithsonian Institution, and other universities have long  worked with NPS to study fauna of seepage springs across the DC region (see Literature Cited below). Their work has been  supported by a mix of NPS park, regional, and program funds, and is facilitated by the Chesapeake Watershed Cooperative Ecosystems Study Unit. The discovery of the two new species comes from work in parks administered by National Capital Parks – East. The same group of scientists also discovered and described the new amphipod species Stygobromus anacostensis in 2024.

Forest Seeps

The setting seems unlikely. Shallow wet woodland habitats separated from the deeper groundwater by a clay layer, with no light, and lots of organic matter from decaying leaves. It’s known as “hypotelminorheic” habitat. These small, pocket-like habitats support highly specialized fauna that have a narrow native range. Because of their small size, forest seeps are especially vulnerable to local disturbances like changes in water supply or land use. Their  biodiversity is also poorly documented, especially in urban landscapes (Cannizzaro et al. 2026). 

If we can protect these unassuming spots, future discoveries of new species or even genera may yet lay ahead. Both new species are found only in these forest seeps and occur nowhere else on earth!

Naming the New Species

Stygobromus paveki was identified through DNA analysis (and later physical analysis) as a unique species located in a forest seep near the Baltimore-Washington Parkway. The scientists who found and formally described this new species, named it. Despite her  suggestion of a place-based name, they named it in tribute to NCR’s Research Coordinator Diane Pavek. 

Stygobromus scottsruni was found in a cluster of seeps near Scott’s Run, a creek in Scott’s Run Regional Park in Virginia (an area just south of the Potomac River on the outside of the Capital Beltway).

This project is facilitated by the Chesapeake Watershed Cooperative Ecosystem Studies Unit (CW CESU). The CW CESU promotes stewardship and integrated ecosystem management of natural and cultural resources in the Chesapeake Watershed through collaborative research, technical assistance, and education. To do research with CW CESU, please contact Danny Filer at 301-689-7108.

Further Reading

New Species of Eyeless Crustaceans Discovered Near Busy City Streets (U.S. National Park Service)

The Seep Shrimp – Urban Ecology Research Learning Alliance (U.S. National Park Service)

Literature Cited:

Niemiller ML, Cannizzaro AG, Sawicki TR, Culver DC. 2024. A new species of Stygobromus Cope, 1872 (Amphipoda, Crangonyctidae) from a hypotelminorheic seepage spring in Washington, D.C., USA. Subterranean Biology 48:117–146.
https://irma.nps.gov/DataStore/Reference/Profile/2318739

Cannizzaro AG, Sawicki TR, Schaefer J, Castrillo D, Maxwell EC, Burch E, Culver DC, Niemiller ML. 2026. Two new species of Stygobromus Cope, 1872 (Amphipoda, Crangonyctidae) amphipods from hypotelminorheic seepage springs in the Washington, D.C., USA area. Subterranean Biology. 57: 23-63. https://irma.nps.gov/DataStore/Reference/Profile/2318718

This article first appeared in the Fall 2026 Edition of the Natural Resource Quarterly published by the Division of Resource Stewardship & Science in the National Capital Region of the National Park Service.