Hay's Spring Amphipod

Stygobromus hayi

Description

The Hay's Spring amphipod, Stygobromus hayi, is a white, eyeless, shrimp-like crustacean only about 0.5 in (1.2 cm) in length.

Behavior

The Hay's Spring amphipod feeds on organic matter, such as leaf litter, decaying organic detritus, and dead insects. Individuals may live five to 10 years. Females carry eggs attached to their belly until they hatch.

Habitat

This species occurs in a small spring, possibly permanent but seeplike in appearance, within the National Zoological Park (in Washington, D. C.) in the heart of a densely populated urban area. The spring appears to issue forth from crevices in Precambrian rocks. The amphipods occur in decaying deciduous leaf litter and mud at the spring's exit.The spring water is cool, fresh, and not obviously polluted.

Distribution

This crustacean is endemic to Hay's Spring, a small outflow located within Rock Creek National Park in the District of Columbia. Only a small percentage of the population has been seen in the spring habitat itself. It likely inhabits cracks, crevices, and the bedrock area that form the recharge zone for the spring. The full range may extend to the limits of the groundwater aquifer.

The Hay's Spring amphipod is only known from Hay's Spring, on the grounds of the National Zoological Park in Washington, D. C. Although there are other springs within Rock Creek National Park, this species has not been found elsewhere since its discovery in 1940. No more than 10 individuals have ever been seen at the site at any one time. From what is known about similar species, such as Stygobromus tenuis, this amphipod probably evolved as a cave-adapted inhabitant of underground cracks and crevices. A second amphipod found in Rock Creek National Park is the undescribed Stygobromus sp., also a candidate for federal endangered status.

Threats

Flood waters from Rock Creek occasionally reach the level of the spring habitat, degrading water quality and disturbing the leaves and bottom sediments that form the amphipod's microhabitat. The site of the spring has been fenced, although protection is minimal, and no signs have been posted. Because the zoo attracts so many visitors, administrators fear that calling further attention to the small spring would cause greater harm than good.

Because of its location within major urban and commercial areas, there is always a possibility that Rock Creek, and the Hay's Spring, are vulnerable to sewage effluent and overflow during a flood. Urban runoff could threaten the aquifer. With such a small and limited population, even short-term changes to the water quality could result in stochastic extirpation.

Conservation and Recovery

The Smithsonian Institution's National Zoological Park has developed a memorandum of understanding with the U. S. Fish and Wildlife Service to protect the amphipod and the area adjacent to the spring. Some measures that have been undertaken in accordance with the agreement include limiting human access to the area, ensuring that park maintenance does not disturb the habitat, and monitoring water quality in the spring.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
300 Westgate Center Dr.
Hadley, Massachusetts 01035-9589
Telephone: (413) 253-8200
Fax: (413) 253-8308
http://northeast.fws.gov/

References

Holsinger, J. R. 1977. "A Review of the Systematics of the Holarctic Amphipod Family Crangonyctidae." Proceedings of the 3rd International Colloquium on Gammarus and Niphargus, Schlitz, West Germany: Crustaceans 4: 244-281.

Holsinger, J. R. 1978. "Systematics of the Subterranean Amphipod Genus Stygobromus (Crangonyctidae), Part II: Species of the Eastern United States." Smithsonian Contributions to Zoology, no. 266.

U. S. Fish and Wildlife Service. 1982. "Determination of Hay's Spring Amphipod as an Endangered Species." Federal Register 47 (25): 5425-5426.