Peck’s Cave Amphipod - Edwards Aquifer Authority

Peck’s Cave Amphipod

Covered Species Information

Authored by Connor Helsel
Peck’s Cave Amphipods (S. pecki) subsist in and around groundwater springs, seeps and upwellings in the Edwards Aquifer. These areas are largely hidden, yet sensitive to changes in springflow, drought and pollution that afflict the aquifer. The Edwards Aquifer Habitat Conservation Plan implements water quality monitoring and Conservation Measures such as the Voluntary Irrigation Suspension Program Option and the Aquifer Storage and Recovery programs to help maintain springflow for these aquifer dwelling species.

Explore how the EAHCP helps protect the Peck’s Cave Amphipod

Common name

Peck’s Cave Amphipod

Scientific name

Stygobromus pecki

Endangered Species Act status

Endangered species

Maximum size

Reaches a size of 10.5 mm (0.41 inches; USFWS, 2013).

Physical description and Life History

The Peck’s Cave Amphipod is a subterranean aquatic species in the Crangonyctidae family. Amphipods are generally described as having five pairs of legs, two pair of antennae and a “laterally flattened body” (Holsinger, 1967). The Peck’s Cave Amphipods are eyeless and unpigmented, traits specific to the Stygobromus genus. Populations of the species in the Comal Springs have been observed to have an orange hue, which is attributed to its food supply (Blake & Everett, 2017).

A microscope examination is usually necessary to distinguish the Peck’s Cave Amphipod from other species (USFWS, 2013; National Academies of Sciences, Engineering, and Medicine., 2018).

Little is known of the lifespan and reproduction of the species in the wild, however, captive refuge populations are under further study.


The Peck’s Cave Amphipods are found in Comal and Hueco Springs and have been collected around Panther Canyon in New Braunfels, Texas (USFWS, 2013).

Habitat and Diet

Peck’s Cave Amphipods are highly adapted for a subterranean life. They only occasionally rise to surface areas around spring openings within a range from 15 meters around spring openings to 110 meters down into the aquifer (78 Fed. Reg. 205, 2013).

They are opportunistic feeders, with a diet comprised of both bacterial biofilm atop woody debris and other small invertebrates (Blake & Everett, 2017).


Blake, M., & Everett, A. (2017). Captive Propagation Manual for Peck’s Cave Amphipod. 25.
Endangered and Threatened Wildlife and Plants; Revised Critical Habitat for the Comal Springs Dryopid Beetle, Comal Springs Riffle Beetle, and Peck’s Cave Amphipod, 78 Fed. Reg. 205 (October 23, 2013) (to be codified at 50 C.F.R. pt. 17).

Holsinger, J. R. (1967). Systematics, Speciation, and Distribution of the Subterranean Amphipod Genus Styognectes (Gammaridae). Bulletin of the United States National Museum. 259:176 pp.

National Academies of Sciences, Engineering, and Medicine. 2018. Review of the Edwards Aquifer Habitat Conservation Plan: Report 3. Washington, DC: The National Academies Press.

U.S. Fish and Wildlife Service (USFWS). (2013). Biological Opinion for the Edwards Aquifer Recovery Implementation Program HCP (No. 21450-2010-F-0110; pp. 52–57). Ecological Services Field Office. Austin, TX.