Groundwater
Guides
Aselloidea
Waterslaters and allies
Aselloidea is a superfamily of freshwater and subterranean isopods within the suborder Asellota. Members are primarily aquatic, with many lineages adapted to life in groundwater, caves, and karst systems. The superfamily includes families such as Asellidae (common freshwater isopods), Stenasellidae, and Atlantasellidae. Some representatives exhibit remarkable morphological specializations for subterranean existence, including reduced eyes and elongated appendages.
Asellota
Asellotes
Asellota is a suborder of isopod crustaceans comprising approximately one-quarter of all marine isopods. The group exhibits remarkable ecological diversity, occurring in marine, freshwater, and subterranean habitats from shallow coastal waters to abyssal depths, including hydrothermal vents. Members possess distinctive morphological specializations including a complex copulatory apparatus that distinguishes them from other isopods. The suborder has undergone multiple independent colonizations of deep-sea environments, with some lineages showing extensive radiation in these habitats.
Bidessini
Bidessini is a tribe of predaceous diving beetles within the family Dytiscidae, comprising at least 40 genera and over 630 described species. Members are small to minute aquatic beetles found across diverse freshwater habitats worldwide, with notable radiations in Australia, South America, and Madagascar. The tribe includes both surface-dwelling (epigean) and subterranean (stygobitic) species, with several genera exhibiting convergent adaptations to groundwater environments.
Caecidotea kenki
Caecidotea kenki is a spring-dwelling asellid isopod found in the eastern United States. Originally described as Asellus kenki by Bowman in 1967, it is one of only three asellid species in Maryland habitually associated with springs rather than subterranean caves. It is distinguished from the six obligate cave-dwelling Caecidotea species in the region by its surface water habitat preference.
Caecidotea racovitzai
Caecidotea racovitzai is a small freshwater isopod in the family Asellidae, originally described as Asellus racovitzai by Williams in 1970. This species belongs to a genus primarily composed of subterranean and groundwater-dwelling crustaceans. Records indicate it has been documented in the United States, specifically in Vermont. Like other members of Caecidotea, it is likely associated with groundwater habitats such as caves, springs, or interstitial environments, though specific ecological details remain poorly documented.
Caecidotea racovitzai australis
Caecidotea racovitzai australis is a subspecies of freshwater isopod in the family Asellidae. It was originally described as Asellus racovitzai australis by Williams in 1970. The subspecies belongs to a genus of aquatic isopods commonly found in groundwater and cave habitats.
Cirolanides texensis
Cirolanides texensis is a subterranean isopod species endemic to Texas. It belongs to the family Cirolanidae, a group of predominantly aquatic isopods that includes many cave-dwelling species. The species was described in 1896 by Benedict and is known from limited observations in karst groundwater systems.
Comaldessus stygius
Comal Springs Diving Beetle
Comaldessus stygius is a small diving beetle in the family Dytiscidae, described from Comal Springs in Texas. It belongs to a genus of minute beetles adapted to spring and groundwater habitats. The species is known from very few records and is considered rare.
Copepoda
copepods
Copepods are small aquatic crustaceans and one of the most abundant and diverse multicellular organisms on Earth. They occupy nearly every aquatic habitat, from marine plankton to deep ocean floors, freshwater lakes, groundwater systems, and even moist terrestrial environments such as leaf litter and bromeliad phytotelmata. The group includes free-living forms as well as highly modified parasites. Copepods are fundamental components of aquatic food webs, serving as critical prey for fish, whales, and other marine life, while also contributing to nutrient cycling and carbon sequestration through the biological pump.
Crangonyctidae
Crangonyctidae is a family of freshwater amphipod crustaceans containing both surface-dwelling and subterranean species. The family includes notable genera such as Crangonyx, Stygobromus, Bactrurus, and Synurella. Many species are obligate groundwater inhabitants adapted to cave and aquifer environments, while others occupy springs, streams, and lakes. The family has a broad geographic distribution across the Northern Hemisphere, with significant diversity in North America, Europe, and Asia.
Diacyclops
Diacyclops is a genus of cyclopoid copepods in the family Cyclopidae containing over 120 described species. Species occupy diverse aquatic habitats including freshwater lakes, wetlands, rivers, and groundwater systems. Some species are planktonic while others are benthic or stygobiontic. The genus shows broad salinity tolerance, with at least one species thriving in brackish conditions up to 5 ppt. Diacyclops species serve as prey for fish and are sensitive indicators of environmental contaminants.
Gammaridae
gammarids, scuds
Gammaridae is a family of amphipod crustaceans with a distribution centered on Eurasia. The family exhibits euryhaline tolerance as a lineage, inhabiting environments from freshwater to marine waters. Historically, Gammaridae served as a wastebin taxon for numerous gammaridean amphipods, many of which have since been reassigned to separate families including Anisogammaridae, Melitidae, and Niphargidae. In North America, members are commonly referred to as scuds.
Gnathostenetroidoidea
Gnathostenetroidoidea is a superfamily of asellotan isopods established by Kussakin in 1967. Members are predominantly small crustaceans adapted to cryptic habitats, including both freshwater groundwater systems and marine interstitial environments. The superfamily includes families such as Protojaniridae and Caecostenetroididae. Documented species exhibit reduced or absent eyes and morphological specializations for subterranean or interstitial life.
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.
Hydroporinae
Hydroporinae is a large subfamily of predaceous diving beetles (family Dytiscidae) containing at least 2,200 described species. Members are primarily aquatic, inhabiting diverse freshwater habitats from lentic pools to lotic streams across all continents except Antarctica. The subfamily exhibits remarkable diversity in body size, with some species among the smallest diving beetles known. Many species are habitat specialists, including stygobiont forms adapted to subterranean waters.
Lirceolus
Texas Caveslaters
Lirceolus is a genus of freshwater isopods in the family Asellidae, endemic to subterranean habitats in Texas, USA. These troglobitic crustaceans are adapted to life in caves and aquifers, showing reduced pigmentation and eye structures compared to surface-dwelling relatives. The genus was established by Bowman and Longley in 1976 to accommodate species previously assigned to other asellid genera. Known as "Texas Caveslaters," they represent an important component of the unique groundwater fauna of the Edwards Aquifer and related systems.
Mexiweckelia hardeni
Mexiweckelia hardeni is a species of amphipod crustacean in the family Hadziidae, first described by Holsinger in 1992. The genus Mexiweckelia is part of a group of amphipods adapted to subterranean or aquatic habitats. As a member of Hadziidae, it likely inhabits groundwater or cave systems, though specific ecological details remain poorly documented. The species is known from limited collection records in the Nearctic region.
Oreoleptidae
Oreoleptid Flies
Oreoleptidae is a monotypic family of flies established in 2005 based on the single species Oreoleptis torrenticola. The family was discovered in the Rocky Mountains where larvae inhabit torrential streams and groundwater wells. Adults were reared from larvae after decades of larval collections that could not be matched to any known adult stage. The family shows morphological affinities to both Pelecorhynchidae and Athericidae/Tabanidae, with distinctive male genitalia linking it to the latter group.
Oreoleptis torrenticola
Oreoleptis torrenticola is the sole species in the monotypic genus Oreoleptis and family Oreoleptidae, a family of flies established in 2005 based on this single species. The species was described from specimens collected in the Rocky Mountains, where its larvae inhabit torrential streams and have also been found in groundwater wells. This enigmatic dipteran represents a distinct lineage whose larval morphology shows similarities to Athericidae and Tabanidae but possesses distinctive abdominal prolegs.
Parachaetocladius
non-biting midges
Parachaetocladius is a genus of non-biting midges in the subfamily Orthocladiinae of the family Chironomidae, established by Wolfgang Wülker in 1959 and revised in 2020. The genus contains approximately 10 described species distributed across the Holarctic region, including both Palaearctic and Nearctic representatives. Species are typically associated with lotic freshwater habitats, particularly sandy substrates in springs and groundwater-fed streams. The genus is distinguished from related orthocladiine genera primarily through adult male genitalic characters, particularly features of the hypopygium.
Paraperla
green stoneflies
Paraperla is a genus of green stoneflies in the family Chloroperlidae, established by Banks in 1906. It contains at least two described species: P. frontalis (the hyporheic sallfly) and P. wilsoni. The genus belongs to the subfamily Paraperlinae and is characterized by its association with subterranean or hyporheic aquatic habitats. These stoneflies are part of the Arctoperlaria, a suborder of Plecoptera found primarily in the Northern Hemisphere.
Siettitiina
Siettitiina is a subtribe of diving beetles (family Dytiscidae) established by Smrz in 1982. It belongs to the subfamily Hydroporinae and tribe Hydroporini. The group includes the genus Iberoporus, which contains the first known stygobiont beetle species from Portugal, Iberoporus pluto, discovered in 2019. Members of this subtribe are associated with subterranean and groundwater habitats.
Stenasellidae
Stenasellidae is a family of stygobiotic (obligate subterranean aquatic) isopods in the suborder Asellota. The family comprises approximately 10 genera including Stenasellus, Metastenasellus, and Parastenasellus, with species distributed across groundwater habitats in Africa, the Middle East, southern Europe, and Southeast Asia. These crustaceans are exclusively adapted to life in continental underground waters including caves, wells, and interstitial aquifers. Their evolutionary history has been shaped by Quaternary climatic events including aridification in tropical zones and glaciations in temperate regions.
Stygobromus
Stygobromus is a genus of subterranean freshwater amphipods in the family Crangonyctidae, comprising 134 described species. The genus is primarily distributed in North America, with a smaller number of species in the Palearctic region including Siberia. Many species are narrow endemics restricted to specific groundwater systems, and several are listed as endangered or vulnerable by the IUCN; one species, S. lucifugus, is extinct.
Stygobromus russelli
Russell's Cave Amphipod, Russell stygobromid
Stygobromus russelli is a subterranean amphipod species in the family Crangonyctidae, endemic to Texas in the United States. As a stygobiont, it inhabits groundwater systems in cave environments. The species was originally described by Holsinger in 1967 under the basionym Stygonectes russelli. Like other members of the genus Stygobromus, it exhibits troglomorphic adaptations including reduced pigmentation and eye development associated with life in permanent darkness.
Stygothrombidiidae
Stygothrombidiidae is a family of mites in the order Trombidiformes. Members are associated with subterranean freshwater habitats, particularly hyporheic zones and groundwater systems. The family is relatively small and poorly documented, with most known species placed in the genus Stygothrombium. These mites represent an example of adaptation to permanent darkness and interstitial aquatic environments.
Stygothrombium
Stygothrombium is a genus of mites in the family Stygothrombiidae, order Trombidiformes. It belongs to the diverse group of prostigmatid mites, which includes many parasitic and predatory forms. The genus was established by K.H. Viets in 1932. Members of this genus are associated with subterranean or groundwater habitats, reflecting the 'stygo-' prefix in its name.