Spring-endemic

Guides

• 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.

  riffle-beetlespring-endemicaquatic-insectgroundwater-dependentEdwards-AquiferDevils-RiverElmidaeColeopteraendangered-speciesconservation-monitoringN-mixture-modelsplastron-respirationspring-habitat-vulnerability

• 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.

  endangeredsubterraneanaquaticspring-endemicEdwards-Aquifertroglobiticconservation