Stygobromus bakeri, a new species of groundwater amphipod (Amphipoda, Crangonyctidae) associated with the Trinity and Edwards aquifers of central Texas, USA

A new stygobitic groundwater amphipod species, Stygobromus bakeri sp. nov., is described from 4 central Texas limestone karst springs; John Knox Spring (Comal County), Jacob’s Well (Hays County), Mormon Spring (Travis County) and Salado Springs (Bell County). This species belongs to the predominately western Nearctic hubbsi species group of Stygobromus and differs from other species in the group by gnathopod 1 with row of 4 to 5 setae posterior to the defining angle, pereopods 6 and 7 with broadly expanded bases and distinct distoposterior lobes, gnathopods 1 and 2 with 2 rows of 3 singly inserted setae on the inner palm, and uropod 3 with single, slightly distal peduncular seta. Habitat, sympatric groundwater species, and conservation issues are discussed.


Introduction
The Nearctic amphipod genus Stygobromus Cope, 1872 (Amphipoda, Crangonyctidae) currently includes 137 described species and 4 subspecies in the United States and Canada (Hay 1882;Hubricht 1943;Derzhavin 1945;Holsinger 1967;Holsinger 1969;Holsinger 1974;Holsinger 1978;Wang and Holsinger 2001;Holsinger 2009;Sidorov et al. 2010;Holsinger et al. 2011;Taylor and Holsinger 2011;Holsinger and Ansell 2014;Holsinger and Sawicki 2016;Cannizzaro et al. 2019;Palatov and Marin 2020). The genus is entirely stygomorphic, and, as with most groundwater-obligate taxa, low detection probability (a function of inaccessible habitat and low population densities), coupled with pervasive convergent evolution (Eberhard et al. 2009;Culver and Pipan 2015;Devitt 2019) results in an incomplete understanding of diversity and systematics within the genus. Many species, cryptic and otherwise, await description. Holsinger (1974) and Wang and Holsinger (2001) provisionally assigned 45 of 54 currently recognized taxa in the western United States and southwestern Canada to the hubbsi group. Although molecular data supporting systematic relationships are lacking for most taxa (but see Ethridge et al. 2013;Aunins et al. 2016;Cannizzaro et al. 2019), the hubbsi group is supported morphologically by lack of sternal gills on the pereonites and a combination of additional characters summarized by Wang and Holsinger (2001). The distribution of Stygobromus in Texas is mapped in Figure 1. In the Edwards Plateau and Balcones Escarpment of central Texas, USA, 9 Stygobromus species are documented alongside diverse assemblages of stygobiontic crustaceans (Holsinger 1967;Gibson et al. 2008;Hutchins 2018;Nissen et al. 2018). Four central Texas Stygobromus species belong to the tenuis group: S. balconis (Hulbricht, 1943), S. reddelli (Holsinger, 1966), S. russelli (Holsinger, 1967), and S. bifurcatus (Holsinger, 1967). Four comprise the central Texas endemic flagellatus group: S. flagellatus (Benedict, 1896), S. longipes (Holsinger, 1966), S. dejectus (Holsinger, 1967), and S. pecki (Holsinger, 1967). Stygobromus hadenoecus (Holsinger, 1966) is the sole described member of the hadenoecus group found in the western Edwards Plateau. The nearest hubbsi group species, S. limbus Wang & Holsinger, 2001, occurs more than 300 km away from the Edwards Plateau taxa in a southeastern extension of the Basin and Range Province of the western United States in far west Texas. Huston and Gibson (2018) reported an undescribed species in the hubbsi group from a single spring site in the Chisos Basin of Big Bend National Park, Texas, also within the Basin and Range Province. Only a single hubbsi group species, S. putealis (Holmes, 1909) from wells in Wisconsin, is currently known from east of North America's western Cordillera (Wang and Holsinger 2001).
Stygobromus species of the hubbsi group are recorded in a variety of groundwater habitats including caves, wells, the hyporheic zone of surface streams, karstic and nonkarstic springs, and hypotelminorheic seeps. Two species live in the depths (5-495 m) of Lake Tahoe (California and Nevada) although Wang and Holsinger (2001) hypothesized that their preferred habitat may actually be adjacent groundwater.
Many groundwater habitats and groundwater-obligate organisms are at risk from a myriad of threats, including groundwater contamination, physical habitat destruction (e.g. gravel mining), and groundwater extraction (Burri et al. 2019;de Graaf et al. 2019), lending urgency to continued documentation of groundwater biodiversity. Here, we describe the 12 th species of Stygobromus from Texas, USA and the first species belonging to the hubbsi group in the Edwards Plateau/Balcones Escarpment region, an area where groundwater extraction to meet the demand of a rapidly growing human population along the Interstate 35 highway corridor increasingly threatens groundwater resources.

Materials and methods
Specimens were collected from karst springs using 150-250 µm mesh drift nets and using multiple techniques at an underwater cave, Jacob's Well ( Fig. 2A) accessed via the resurgence entrance using SCUBA (Fig. 2B, C). Divers performed surveys at Jacob's Well, Hays County on 20 occasions from May 2009 to June 2011, using visual searches, a drift net placed at a vertical constriction at -25 m depth and 42 m penetration, cloth lures secured to the side of the cave shaft near the entrance, and baited bot-   tle traps placed in a broad, low room at -30 m depth and 70 m penetration. The visual search area within the underwater passage began at the shaft below the spring opening and up to a maximum penetration of 330 m. Hand sampling was performed using basters, fine aquarium dipnets, and centrifuge vials. Külköylüoğlu and Gibson (2018) and Külköylüoğlu et al. (2017) described collection details at John Knox Springs, Comal County. Surveys using 250 µm drift nets at springs in the city of Salado, Bell County (Fig. 3) began in 2015 and have continued seasonally as part of a monitoring project for the endangered Salado salamander, Eurycea chisholmensis Chippindale, Price, Wiens & Hillis, 2000 at 10 spring orifices at Robertson Springs and 2 spring orifices at the Downtown Spring Complex (Diaz and Warren 2019). Mormon Spring #3, in Travis County was sampled using 150 µm drift nets from 20 January to 23 February 2017. All samples were stored in 95% ethanol.
Specimens were dissected, and mouthparts and appendages were mounted in glycerin. Images and measurements were acquired at multiple magnifications and focal points using an Olympus BX-45 compound stereomicroscope and Nikon DS-5M digital camera. Images were imported into Abode Illustrator Creative Suite 5 software and line drawing illustrations were produced using a Wacom Cintiq 22HD Interactive Pen Display. Nomenclature for setal arrangement on the mandibular palps follows Cole (1980) for segment 2 and Stock (1974) for segment 3. The "defining angle" of the gnathopod propodus is the area where the tip of the dactylus rests on the posterior margin of the palm. "Robust setae" and "setae" were used in place of the traditional "spine teeth" and "spines" following Watling (1989) and Cannizzaro et al. (2019).  Fig. 4 Type locality. USA, Texas, Comal County, John Knox Ranch, John Knox Spring (29.9642, -98.1956).  Diagnosis. Small stygobitic species similar to most members of the hubbsi group with mature females larger than males, gnathopod 2 larger than gnathopod 1, posterior margin of gnathopod 1 typically shorter than palm, and telson as long as broad with shallow notch in apical margin. Distinguished from other hubbsi group species by gnathopods 1 and 2 with 2 rows of 3 singly inserted setae on the inner palm, and combination of following characters: gnathopod 1 with row of 4 to 5 setae posterior to the defining angle (compare to S. quatsinensis Holsinger & Shaw, 1986 with 2 or 3 postmarginal setae, 3 hubbsi group species have 1 or 2 postmarginal setae and all others are lacking); pereopods 6 and 7 with broadly expanded bases and distinct distoposterior lobes (similar to S. salturus Wang & Holsinger, 2001); and uropod 3 with single, slightly distal peduncular seta (similar to S. lanensis Wang & Holsinger, 2001).
Gnathopod 1 (Fig. 6, G1): propodus shorter than that of gnathopod 2; coxal plate longer than broad, with 1 ventral and 2 anterior marginal setae; basis with 5 long setae inserted along posterior margin; ischium with 2 setae and scale patch along posterior margin; merus with 9 posterodistal setae and patch of pubescence; carpus 36% length of propodus, with 9 setae; propodus 1.5× longer than widest point with 3 superior and 3 inferior medial setae, palm slightly convex with 10 inner and 11 outer bifurcate robust setae, 2 of these posterior to defining angle, defining angle rounded and sub angular, margin posterior to defining angle ca. half the length of the palm with 4-5 setae and scaly patch becoming finer at defining angle and granular along inner margin of dactylus depression; dactylus with 1 seta on outer margin and 3 on distal half of inner margin; dactylus nail ca. 21% length of dactylus.
Gnathopod 2 (Fig. 6, G2): propodus 1.3× longer than that of gnathopod 1; coxal plate quadrate, with 1 ventral and 2 anterior marginal setae; basis with 1 long seta on anterior margin, shorter seta on posterodistal margin; ischium with 1 seta and scale patch on posterior surface; merus with 2 posterodistal setae, scale patch on posterior surface; carpus 25% length of propodus, with 3 distal setae, 7 setae and scale patch on posterior surface; propodus ca. 2× longer than widest point with 3 superior and 3 inferior medial setae, palm straight to slightly convex with 11 inner and 13 outer bifurcate robust setae, 2 of these posterior to defining angle and 3 sets of paired setae, 2 of these posterior to defining angle, defining angle rounded, margin posterior to defining angle ca. half the length of the palm with scaly patch on poster margin becoming finer at defining angle and granular along inner margin of dactylus depression; dactylus with 1 seta on outer margin; dactylus nail ca. 15% length of dactylus.
Male (3.1 mm). Closely resembles female but typically smaller, with fewer setae on appendages, and differing in the following characters: Antenna 1 proportionally longer, up to 46% length of body; primary flagellum with 9 segments. Uropod 2 inner and outer rami subequal in length.
Etymology. Epithet bakeri honors David Baker, a citizen scientist, conservationist and visionary who has worked for decades to bring together scientists, politicians, funders, regulators and stakeholders from near and far to conserve the watershed of Jacob's Well. David lived immediately over the underwater cave for some time, working hard to make his own property environmentally friendly and to educate those who visited. He formed the Wimberley Valley Watershed Association, a non-profit with the mission to protect Jacob's Well and Cypress Creek.
Distribution and ecology. To date, this small species has been collected in 2 karst springs in southwestern Hays and northwestern Comal counties, Texas, a single karst spring 50 km northeast, on the shoreline of the Colorado River (usually emerging beneath a boat dock in Lake Austin) in Austin, Travis County, Texas and 2 karst spring complexes 74 km further northeast in Salado, Bell County, Texas (Fig. 1). All 4 sites are hydrogeologically distinct.
Jacob's Well ( Fig. 2A-C) is a natural spring and cave located in the bed of Cypress Creek with enterable passage typically 1-2 m in diameter, and mapped using cave SCUBA to about 42 m deep and 1.6 km in length. Water issues out of the cave from Glen Rose Limestone (Middle Trinity Aquifer) and flows down Cypress Creek: a tributary of the Blanco River (Gary et al. 2019). Stygobromus bakeri sp. nov. was only sampled successfully by hand, with divers using basters, dipnets, and centrifuge vials. Typically, the species was seen in the water column or on the floor, which consisted of silt, breakdown and cobble. Drift nets, bottle traps and cotton lures were not effective at capturing this species at Jacob's Well. It was seen only in a deeper portion of the cave between 70 m and 215 m penetration. At 70 m penetration, the cave passage descends from -30 m to -42 m through a vertical slot called "The Knife Edge", beyond which, S. bakeri sp. nov. was collected. But beyond 215 m, the passage ascends back to 30 m and the species was not observed in that section. The habitat was not obviously different in the areas where the species was observed, with the exception of the entrance area (within 70 m of the surface) that has both surface influence and passage constrictions with greater flow, leading to smooth, scoured rocks and less silt.
John Knox Spring (Fig. 2D, E) emerges from Lower Glenn Rose Limestone (Middle Trinity Aquifer) through a 0.3 m vertical crevice-like orifice 1 meter below the water surface and along the bank of a limestone grotto pool forming the headwaters of Carper's Creek which discharges into the Blanco River. Interstitial surface insect fauna collected from this spring along with Stygobromus russelli (the most widespread Stygobromus species in central Texas) suggests that some portion of the flow might arise from hyporheic or vadose origin. Details of this habitat are described in Külköylüoğlu and Gibson (2018).
Robertson Springs (Fig. 3A-D) and Downtown Spring Complex (Fig. 3E, F) are 0.4 km apart, located on opposite sides of Interstate Highway 35 in the city of Salado. Both spring complexes comprise several spring orifices issuing from Edwards and Comanche Peak limestones forming spring runs that empty into Salado Creek. A diverse interstitial groundwater fauna (Table 1) including relatively widespread species has been recorded from these springs. Stygobromus bakeri sp. nov. was initially sampled by drift netting at Middle Robertson Springs (Norris et al. 2012). Robertson Springs has numerous spring openings (over 30 sites mapped during high flows) with variable discharge and substrate issuing from both banks and from under the 300 m long spring run. Stygobromus bakeri sp. nov. was collected at 4 spring sites throughout the run at different spring zones within the Robertson Springs complex (Diaz et al. 2016;Diaz and Warren 2019). The upper springs cease flowing seasonally and often produce troglofauna (terrestrial cave fauna) when flows resume after adequate rain events, while the lower springs are perennial and occasionally produce troglofauna. The Downtown Spring Complex is more discrete than Robertson Springs, with each of the 7 spring sites issuing from a single origin. Most of the springflow issues from Big Boiling Spring and flows down a short 5 meter spring run that empties into Salado Creek. Anderson Spring is 350 m downstream of Big Boiling Spring, has much less flow, issues from a fissure underneath a spring run (250 m downstream of the headwater Critchfield Spring), and flows 21 m before joining Salado Creek (Norris et al. 2012). Hydrological studies of this area in the Northern Segment of the Edwards Aquifer showed the Downtown Spring Complex to be part of an integrated fracture system with groundwater flow velocities recorded at 1.8 m/sec and confirmed mixing of groundwater and Salado Creek surface water at Big Boiling Spring (Wong and Yelderman 2017).
Mormon Spring # 3 (Fig. 2F, G), which normally lies beneath Lake Austin on the Colorado River, issues from Fredericksburg Group consolidation (limestone, dolomite, chert, and marl). Lake Austin was constructed in 1940, replacing the damaged Austin Dam, which may have also inundated the spring. From time to time, the Lower Colorado River Authority lowers the level of Lake Austin to allow for dock maintenance. During the last such lowering of 3 m in January 2017, multiple spring  (Hershler & Longley, 1986) S X Phreatodrobia conica Hershler & Longley, 1986 S X Phreatodrobia micra (Pilsbry & Ferriss, 1906) S X Phreatodrobia nugax (Pilsbry & Ferriss, 1906) S X X Stygopyrgus bartonensis Hershler & Longley, 1986 S X Family Hydrobiidae Marstonia comalensis (Pilsbry & Ferriss, 1906 (Holsinger, 1967) S X X X Stygobromus russelli (Holsinger, 1967) S  (Steeves, 1968) S X X Lirceolus bisetus (Steeves, 1968) X Lirceolus hardeni (Lewis & Bowman, 1996) S X X X Lirceolus pilus (Steeves, 1968 (Brady, 1864) C X Pseudocandona cf semicognita (Schäfer, 1934) C X Physocypria cf globula Furtos, 1933 C X Darwinula stevensoni (Brady & Robertson, 1870) C X Cypridopsis sp. (Brady, 1867) C X Physocypria denticulata (Daday, 1905) C X Chlamydotheca texasiensis (Baird, 1862) C X Cypridopsis cf helvetica Kaufmann, 1900 C X complexes were visible over a stretch of about 100 m along the east shore of the lake. North to south, Mormon Springs numbers 1 and 2 emerged from sediment, without visible bedrock apertures. Mormon Spring # 3 consists of multiple bedrock outlets in a cutbank excavated in bedrock below a boat dock. The spring appears associated with the Trinity Aquifer but is located near the Edwards Aquifer boundary and could potentially be a gravity spring from local recharge intersected by the Colorado River. Alternatively, this spring could represent flow from the north, from the Balcones Escarpment. No dye tracing has been conducted at this spring to characterize its springshed. Stygobromus bakeri sp. nov. co-occurs with S. russelli (all sites), S. bifurcatus (Jacob's Well, Salado Springs, and Mormon Springs), and a large undescribed species of Stygobromus in the flagellatus group (Jacob's Well). The presence of 4 Stygobromus species at Jacob's Well is notable, and presumably all 4 species occupy different ecological niches. Due to its unusually small size and robust body, S. bakeri sp. nov. is able to inhabit both deep cave and shallow spring habitats. It may also occupy interstitial habitats such as the hyporheic zone of surface streams, although it was not collected in hyporheic samples from Carper's Creek, near John Knox Spring. The small adult size and general stout teardrop body shape is reminiscent of Seborgia relicta Holsinger, 1980 andS. hershleri Holsinger, 1992 found in groundwater habitats (deep aquifer caves and wells, springs, and hyporheos) throughout the Edwards Plateau and Balcones Escarpment. Seborgia has not been found associated with the Glen Rose formation of the Trinity Aquifer nor with the northernmost section of the Edwards Aquifer extending north of the Colorado River in Austin to Salado where Stygobromus bakeri sp. nov. occurs (Fig. 1). The furthest northern record for Seborgia relicta is from Cold Spring issuing from the Edwards Aquifer on the southern bank of the Colorado River (Ladybird Johnson Lake) only 4 km downstream of Mormon Spring #3. Groundwater fauna records for Stygobromus bakeri sp. nov. sites (Table 1) include interstitial and relatively widespread, ecological generalist stygobionts and crenobionts, yet widespread cavernicolous stygobionts such as Cirolanides spp. isopods are absent at these sites (Holsinger 1967;Lewis 2000;Krejca 2009;Hutchins 2018;Devitt et al. 2019;Schwartz et al. 2019;Alvear et al. 2020). Many of the springs have been thoroughly sampled and regularly monitored for multiple years, so the stygofauna is better characterized relative to many other Texas groundwater sites.

Discussion
The description of S. bakeri sp. nov. represents a southeast extension of the known range of the hubbsi group into the eastern Edwards Plateau and Balcones Escarpment of central Texas. Stygobromus putealis, described from eastern Wisconsin is the only other representative of the hubbsi group that occurs east of the western Cordillera of North America (Wang and Holsinger 2001). The presence of this species at Robertson Springs, over 70 km away from the other nearest known site for the species is somewhat unusual not only because of the distance, but because the sites are discharge points for 2 distinct karst aquifers, the Trinity and Edwards. However, at least 3 other Stygobromus species (S. bifurcatus, S. longipes, S. russelli) also occur in both the Trinity and Edwards aquifers, and limited, localized hydrologic connections between these aquifers have been documented (Tian et al. 2020), opening the possibility of interaquifer dispersal. Additionally, numerous members of the hubbsi group have been recorded from the hyporheic zone of surface streams (Wang and Holsinger 2001) which could provide another potential avenue for dispersal by S. bakeri sp. nov. While the current range of S. bakeri sp. nov. is within the range reported for other Stygobromus species (Hutchins 2018) and certainly within the 200 km range reported for macrostygobionts by Trontelj et al. (2009), genetic analysis would still be prudent to evaluate whether southern and northern populations represent cryptic lineages. At all sites where S. bakeri sp. nov. was detected, it occurs in apparently low abundance, particularly compared to co-occurring Stygobromus (e.g. at John Knox Spring, S. bakeri sp. nov. composed 10% of all Stygobromus (27 versus 236 S. russelli) collected from 6 January to 21 May 2010. In comparison, at Robertson Springs, the highest yearly abundance of S. bakeri sp. nov. was 5% of all Stygobromus (26 versus 532 S. russelli and S. bifurcatus combined) collected from 12 April to 7 November 2018. However, it is uncertain whether perceived rarity reflects actual rarity or a lack of effective sampling (Niemiller et al. 2018). Indeed, we lack much basic ecological information about the species including niche breadth and microhabitat preference. A better understanding of the species' rarity and distribution is a high priority given growing threats to water quantity and water quality in the region.
Both Jacob's Well and John Knox Springs are fed by the Trinity Aquifer, although the recharge area for John Knox Spring has not been delineated. Recharge for Jacob's Well primarily occurs in an 80 km 2 area within the Dry Cypress Creek watershed northwest of the spring (Gary et al. 2019). Increased pumping in the region has resulted in reduced spring flow at Jacob's Well, which now flows intermittently (Hunt et al. 2013), and projected rapid human population growth in the region will put additional pressures on groundwater resources. Hays County is the 3 rd fastest growing county, by percent, in Texas (Texas Demographic Center 2019). Desired future conditions set by Groundwater Management Area 9 allow for an increase in average drawdown of the Trinity Aquifer in the region up to approximately 9 m by 2060, which if realized, would result in reduced spring flow or spring failure for many Trinity-fed springs. A Recharge Study Zone created in January 2020 and a proposed Jacob's Well Groundwater Management Zone afford some pumping curtailments and restrictions on new well construction in the region. Neither of these zones, however, provides conservation benefits for the John Knox Spring springshed, which probably occurs farther west in adjacent Comal County, Texas. Texas Parks and Wildlife Department recorded discharge measurements of 28-57 L/s at Carper's Creek in 2005, 2007 and the springshed proportional to this discharge is assumed to be approximately 13-18 km 2 (Marcus Gary, Edwards Aquifer Authority, pers. comm.).
The listing of several aquifer-obligate species in the adjacent Edwards Aquifer in the 1960s, 1970s, and 1980s spurred formation of the Edwards Aquifer Authority (EAA) in 1993. Charged with protecting minimum spring flows at Comal and San Marcos springs, the EAA implemented programs that helped protect groundwater recharge and reduce groundwater use (including enforcement of pumping limitations). The regulatory actions of the EAA and conservation measures established in the Edwards Aquifer Habitat Conservation Plan (HCP) have been successful in maintaining spring flow despite a rapidly growing population. Indeed, existing models predict that HCP conservation measures are sufficient to maintain springflows during drought-ofrecord conditions that would otherwise result in spring failure (Votteler and Gulley 2014). However, EAA jurisdiction does not cover sites at which S. bakeri sp. nov. occurs. Although similar regulatory frameworks do not exist for the Jacob's Well and John Knox Springs area, the proposed management practices outlined by the Jacob's Well Groundwater Management Zone were designed explicitly to maintain springflow during periods of drought (Gary et al. 2019).
Recharge of the northern section of the Edwards Aquifer and groundwater conservation in Salado is not regulated by the EAA. In this section of the aquifer, Clearwater Underground Water Conservation District is responsible for management of groundwater in Bell County. Recharge for the springs where S. bakeri sp. nov. and the federally threatened salamander, Eurycea chisholmensis occur are thought to be in the west and southwest portion of Bell County with flow moving generally southeast (Wong and Yelderman 2017). In addition, Brune hypothesized that the recharge to Salado Creek began from fissures along the Williamson and Bell county line (Brune 1981). Bell County is the most northern extension of the Edwards Aquifer in Texas (Wong and Yelderman 2017) and the most northern location known for many Edwards Aquifer associated taxa (Alvear et al. 2020). Edwards limestones thin in Bell County relative to areas to the south, and the southeastern extent of the county was described as being devoid of substantial caves (McKenzie and Reddell 1964).
Mormon Springs is located upstream, but near habitat for the federally endangered Barton Springs and Austin blind salamanders (Eurcyea sosorum Hillis, 1993 andE. waterlooensis Hillis, Chamberlain, Wilcox &Chippindale, 2001), and is in the same aquifer formation as the federally endangered Jollyville Plateau salamander, E. tonkawae Chippindale, Price, Wiens & Hillis, 2000. Little is known about groundwater flow on the northeast side of the Colorado River on the Balcones Escarpment. Mormon Springs is not within a groundwater conservation district, and well pumping, mainly for domestic landscaping use, is unregulated.

Conclusion
The discovery of an undescribed Stygobromus amphipod from the Trinity and Edwards aquifers associated karst springs in Hays, Comal, Travis, and Bell counties in central Texas is unsurprising giving the high species richness and small-range endemism previously reported for the genus and previous documentation of numerous undescribed taxa . However, the assignment of S. bakeri sp. nov. to the predominantly western hubbsi group suggests that the hubbsi group may be more widespread than currently recognized and that additional investigation for smallbodied taxa west of the continental divide will yield additional undescribed species. Stygobromus bakeri sp. nov. is the 12 th Stygobromus species described from Texas and can be distinguished from other Texas congeners by gnathopod 2 larger than gnathopod 1 and pereopods 6 and 7 with broadly expanded bases and distinct distoposterior lobes.
Stygobrumus bakeri sp. nov. is distinguished from all other hubbsi group species by gnathopod 1 and 2 with 2 rows of 3 singly inserted setae on the inner palm, gnathopod 1 with row of 4-5 setae posterior to the defining angle, and uropod 3 with single, slightly distal peduncular seta. Molecular analysis is recommended to assess the relatedness of southern Trinity Aquifer populations versus northern Edwards Aquifer populations. Finally, the description of small-range endemic species in the region underscores the immediate need for a comprehensive groundwater management framework that ensures adequate groundwater habitat in the face of drought exacerbated by a changing climate and growing human populations.