Edwards-aquifer
Guides
Haideoporus texanus
Edwards Aquifer Diving Beetle
Haideoporus texanus is a stygobiontic diving beetle endemic to the Edwards Aquifer of Texas. It is a subterranean aquatic species adapted to life in groundwater systems, with larvae possessing characteristic morphological features including a nasale and absence of primary pores MXd and LAc. The species was described in 1976 and represents an independently evolved lineage within the subfamily Hydroporinae.
Heterelmis
riffle beetles
Heterelmis is a genus of aquatic beetles in the family Elmidae, commonly known as riffle beetles. The genus includes several described species, with Heterelmis comalensis being particularly notable as an endangered species endemic to spring systems in Texas. Members of this genus are fully aquatic, inhabiting oxygen-rich flowing water environments where they feed on microbial biofilms. Some species have reduced or non-functional wings, limiting their dispersal ability and making them vulnerable to habitat degradation.
Heterelmis comalensis
Comal Springs riffle beetle
Heterelmis comalensis is a federally endangered aquatic beetle endemic to two spring systems in Texas. Described in 1988, this flightless species measures approximately 2 mm and inhabits shallow gravel substrates in spring riffles fed by the Edwards Aquifer. The species has been the focus of intensive conservation research, including captive breeding programs and studies on sexual dimorphism identification.
Heterelmis glabra
riffle beetle
Heterelmis glabra is a species of riffle beetle in the family Elmidae, found in Central America and North America. The largest known populations occur in springs associated with the upper Devils River in south-central Texas. As a spring-adapted organism, it has life-history patterns requiring surface habitat components, making it vulnerable to changes in spring flow. The species has been studied using N-mixture models to assess abundance and distribution across spring sources.
Stygobromus pecki
Peck's cave amphipod
Stygobromus pecki is a small, eyeless, unpigmented cave-dwelling amphipod endemic to four spring systems in Comal County, Texas. It is a federally listed endangered species in the United States and classified as Endangered on the IUCN Red List due to its extremely limited geographic distribution. The species inhabits subterranean limestone aquifers and exhibits adaptations typical of stygobitic organisms, including light sensitivity and starvation resistance. Very few individuals have been documented since its listing, and no formal recovery plan or comprehensive population assessment exists as of 2022.
Stygoparnus
Comal Springs dryopid beetle (for sole species S. comalensis)
Stygoparnus is a monotypic genus of dryopid beetles containing the single species Stygoparnus comalensis, known as the Comal Springs dryopid beetle. The genus is endemic to central Texas spring systems fed by the Edwards Aquifer. Its sole member is a federally endangered, subterranean-obligate aquatic beetle with vestigial eyes and reduced pigmentation. The genus represents the only known aquatic lineage within the family Dryopidae.
Stygoparnus comalensis
Comal Springs dryopid beetle
Stygoparnus comalensis is a federally endangered, subterranean-obligate dryopid beetle endemic to three spring systems in the Edwards Aquifer region of central Texas. Adults are approximately 2 mm long with vestigial eyes and undeveloped wings, reflecting their troglobitic ancestry. The species exhibits extreme population genetic structure with no gene flow among localities, indicating evolutionary isolation. Captive studies reveal strong habitat preferences for wood substrates and specific phototactic responses to light wavelength. The beetle serves as a surrogate species for monitoring aquifer health and faces threats from groundwater extraction, pollution, and drought-induced springflow reduction.