[Photo: Texas Parks and Wildlife]

Peck's Cave Amphipod
Stygobromus pecki

Description: The Peck's cave amphipod is a subterranean, aquatic crustacean of the family Crangonyctidae. The Stygobromus genus is differentiated from the other members of the family due to its lack of eyes. It also has no skin pigmentation, giving it a translucent appearance that is consistent with other cave-dwelling species. The Peck's cave amphipod can grow up to 0.4 inches (10.5 mm) long.

Life History: Not much is known of this amphipod's life history, but information about related species suggest that the Peck's cave amphipod avoids bright light and feeds on detritus. The range of this species is limited because it cannot swim upstream against a strong current. Amphipods generally have a one year long life cycle, however cave species may take longer to mature (up to 6 years).

Habitat: The Peck's cave amphipod is a mostly subterranean species, found at the bottom of underground streams in the caves of the Edwards Aquifer, where it lives among rocks, crevices, and detritus. Outside of the aquifer, at the spring openings, the Peck's cave amphipod is easy prey and can not survive. There is little known about this species; however the Stygobromus genus, in general, prefers cool, thermally constant waters.

Distribution: Stygobromus pecki has been found at Comal Springs and Hueco Springs (Comal county), in the Edwards Aquifer, central Texas.

The map below depicts the critical habitat for this species, as designated by the US Fish and Wildlife Service pursuant to the Endangered Species Act.

NOTE: No warranty is given, expressed or implied, as to the accuracy, reliability, or completeness of these data. Data do not represent a legal description of the critical habitat boundary; refer to the textual description in the appropriate final rule for this species as published in the Federal Register.

Federally Designated Critical Habitat for the Peck's Cave Amphipod (Stygobromus pecki) [Figure: Houston Advanced Research Center using USFWS data]

Status: The Peck's cave amphipod is a state and federally listed (1997) endangered species. Groundwater quality is important to the survival of the Peck's cave amphipod because it requires high dissolved oxygen content for respiration. This species is not as sensitive to changes in groundwater or surface water quantity as other spring-dwelling species because it can retreat into the aquifer under low flow conditions. The spring flow defined as "take" for this species is 40 cubic feet per second (cfs) or less. At 20 cfs or less there is a possible legitimate risk to the population.

Resources:

Edwards Aquifer Authority, Draft Edwards Aquifer Habitat Conservation Plan

US Fish and Wildlife Service, Endangered Species Listing

Texas A&M, Peck's Cave Amphipod Status

Texas Parks and Wildlife, Endangered Species of the Edwards Aquifer