Hyalella keepuikantun Cannizzaro, Lange & Berg, 2025

Cannizzaro, Andrew G., Lange, Corey J. & Berg, David J., 2025, Gateways to the underworld: molecular phylogenetic analyses identify patterns of groundwater fauna and two new species of hypogean Hyalella Smith, 1874 (Amphipoda, Hyalellidae) from the northern Mojave Desert, Subterranean Biology 54, pp. 35-68 : 35-68

Hyalella keepuikantun Cannizzaro, Lange & Berg sp. nov.

Figs 11 , 12 , 13 , 14 , 15 , 16 , 17

Material examined.

• Holotype, male 3.48 mm: Devils Hole II , Nye County, Nevada, USA ( 36.42714, -116.29117); collectors: Jeffrey Goldstein / Olin Feuerbacher, 08 February 2017; USNM 1694154 . • Allotype, female 3.62 mm: Devils Hole II , Nye County, Nevada, USA ( 36.42714, -116.29117); collectors: Jeffrey Goldstein / Olin Feuerbacher, 08 January 2020; USNM 1694155 . • Paratype, male, same locality and collection information as holotype; USNM 1694157 . • Paratype male, same locality and collection information as allotype; USNM 1694156 .

Type locality.

Devils Hole II, Death Valley National Park, Nye County, Nevada, USA ( 36.42714, -116.29117).

Etymology.

The specific epithet keepuikantun means “ blind ” in Timbisha Shoshone (literally “ no eye having ”, kee (no / negative) pui (eye) katün (possession or having )) is given in reference to the lack of eyes and the location of Devils Hole II within Death Valley, the homeland of the Timbisha Shoshone Tribe. This name was selected in consultation with the Timbisha Shoshone Tribal Historic Preservation Office.

Diagnosis.

Small sized, stygomorphic species distinguished from congeners — except members of the H. muerta and H. cretae complex — by the combination of the following characters: eyes absent; antenna 1 longer than antenna 2; pleonites lacking dorsoposterior carinae; maxilla 1 inner plate with 2 apical pappose setae; male uropod 1 inner ramus lacking long curved setae. Differentiated from H. muerta and other members of the H. cretae complex by the combination of the following characters: maxilliped inner plate with 4 apical robust setae; male gnathopod 2 palmar margin with weak anterior notch; pereopod 7 basis projecting <1.2 × the length of the ischium, with <5 posterior setae, all simple, length 25 % remainder of the pereopod segments; uropod 3 ramus with robust setae; telson with 4 apical setae.

Description.

Holotype male (Figs 3 C , 11 – 15 ): 3.48 mm in length. Eyes and integumentary pigment absent (Fig. 3 C ).

Antennae. Antenna 1 (Fig. 11 A ): approximately 1.4 × length of antenna 2; peduncle segment 1 with posterodistal robust seta; primary flagellum with 9 segments, aesthetascs on distal segments, aesthetascs shorter than respective segments, antepenultimate 3 segments with paired aesthetascs.

Antenna 2 (Fig. 11 B ): approximately 25 % body length, gland cone distinct; peduncular segment 5 subequal in length to segment 4; flagellum with 8 segments.

Mouthparts. Mandibles: left mandible (Fig. 11 C ): incisor 8 - dentate, lacinia mobilis 5 - dentate, accessory setal row with 3 plumose setae; molar process well-developed, cylindrical triturative, with plumose seta.

Right mandible (Fig. 11 D ): incisor 7 - dentate, lacinia mobilis trifid, lobes with numerous fine dentations; accessory setae row with 2 plumose setae; molar similar in form to left mandible.

Upper lip (Fig. 12 A ): rounded, apical margin of labrum with numerous setules.

Lower lip (Fig. 12 B ): inner lobes indistinct, outer margin of inner and outer lobes covered in setules; face of lip covered in pubescent setules.

Maxilla 1 (Fig. 12 C ): inner plate shorter than outer plate, with 2 apical pappose setae, and fine pubescent setules covering the entire plate; outer plate with 9 apical serrate setae, pubescent setules sparse decreasing laterally and proximally; palp one-segmented, vestigial, 20 % length of outer plate, tapering strongly distally, with sparse pubescent setules, palp emerges at approximately 70 % the length of the outer plate.

Maxilla 2 (Fig. 12 D ): both inner and outer plates covered in pubescent setules; outer plate subequal in length to inner plate, with numerous apical setae; inner plate narrowing slightly distally with numerous apical setae and 2 pappose facial setae.

Maxilliped (Fig. 12 E ): inner plate shorter than outer plate with 4 unarmed cuspidate setae along apical margin, surface of plate covered in pubescent setules; outer plate with numerous setae, lacking pubescent setules; palp 4 - segmented, second and third segments with numerous marginal, submarginal setae; dactylus surface lacking comb-scales, nail not elongate.

Gnathopods. Gnathopod 1 (Fig. 13 A ): coxal plate with 4 short apical setae; basis narrowing proximally, distoposterior surface of segment lacking comb-scales; ischium with a posterior seta; merus with 3 posterior setae, distoposterior surface of segment lacking comb-scales; carpus subequal in length to propodus, with cluster of posterior serrulate setae; propodus 1.3 × longer than broad with 5 inner medial serrulate setae, anterodistal corner with tuft of setae, sparse comb-scales present along posterior margin; palm straight, with 5–9 setae on inner / outer margins; defining angle straight with 2 robust setae; dactylus with plumose seta on outer margin and 3 inner setae, surface lacking comb-scales.

Gnathopod 2 (Fig. 13 B ): coxal plate with 3 short apical setae; basis narrowing weakly proximally; ischium with a posterior seta; merus with 3 posterior setae, distoposterior surface of segment lacking comb-scales; carpus 40 % length of propodus, posterior margin lobate, 33 % breadth of segment, lacking comb-scales; propodus enlarged, powerful, 1.1 × longer than broad, with tuft of anterodistal setae, posterior setae absent; palm straight, irregular with weak anterior notch, palm with 9 inner and 11 outer robust setae; defining angle weak, projecting slightly past carpus posterior lobe, with 2 robust setae arranged around notch where tip of dactylus rests, comb-scales present apically; dactylus with plumose seta on outer margin placed proximally and 3 inner setae.

Pereopods. Pereopod 3 (Fig. 14 A ): coxal plate with 5 short apical setae, plate not excavated posteroproximally; basis much longer than coxal plate lacking posterior marginal setae; merus subequal in length to carpus; carpus 80 % length of propodus; dactylus 50 % length of propodus, with plumose seta placed proximally on outer margin and 2 setae inserted adjacent to base of nail.

Pereopod 4 (Fig. 14 B ): coxal plate with 4 short apical setae, plate excavated posteroproximally; basis much longer than coxal plate lacking posterior marginal setae; merus subequal to carpus in length; carpus subequal in length to propodus; dactylus 50 % length of propodus, setation as in pereopod 3.

Pereopod 5 (Fig. 14 C ): coxal plate large, bilobate, anterior / posterior lobes both with a seta; basis posterior margin weakly convex, with 4 short setae, posterodistal corner convex, anterior margin with 4 robust setae; merus subequal in length to carpus; carpus 70 % length of propodus, dactylus 40 % length of propodus, with plumose seta placed proximally on posterior margin and 2 setae inserted adjacent to base of nail.

Pereopod 6 (Fig. 14 D ): coxal plate large, bilobate, with produced posterior lobe; basis posterior margin straight to convex, with 3 short setae, posterodistal corner straight, anterior margin with 2 robust setae; merus subequal in length to carpus; carpus 85 % length of propodus; dactylus 40 % length of propodus, setation as in pereopod 5.

Pereopod 7 (Fig. 14 E ): coxal plate diminutive, lobes indistinct; basis posterior margin weakly convex, projecting 1.1 × past the ischium, with 4 short setae extending to start of posterodistal corner, robust setae absent, posterodistal corner rounded, anterior margin with 2 robust setae, basis length 25 % remainder of pereopod segments; merus 70 % length of carpus; carpus 90 % length of propodus; dactylus 50 % length of propodus, setation like pereopods 5 and 6.

Gills. Coxal gills present on somites 2–7, sternal gills present on somites 3–6 (Figs 13 B , 14 A-E ).

Pleon. Pleosome somites lacking dorsoposterior carinae. Epimera (Fig. 15 A ): first epimeron ventral margin unarmed, distoposterior corner not produced, posterior margin with a single seta; second and third epimera like first in form, each with a posterior seta placed more medially.

Pleopods (Fig. 15 B ): peduncle of pleopod 1 90 % length of rami, with 2 coupling hooks lacking setae; outer, inner rami with 3 and 6 segments respectively. Pleopod 2 peduncle similar to first, with 2 coupling hooks; outer, inner rami with 3, 6 segments respectively. Pleopod 3 peduncle similar to first and second, with 2 coupling hooks; outer, inner rami with 3, 5 segments respectively.

Urosome. Somites free, bare dorsally. Uropod 1 (Fig. 15 C ): peduncle 1.3 × length of inner ramus with 4 outer robust setae and an inner robust seta; rami narrowing slightly distally, outer ramus with 1 marginal robust seta, and 4 apical robust setae; inner ramus 90 % length of outer ramus with 5 apical robust setae, marginal robust setae lacking.

Uropod 2 (Fig. 15 D ): peduncle subequal in length to inner ramus with 1 inner robust seta and 2 outer robust setae; rami not narrowing distally, outer ramus with 1 marginal robust seta, and 5 apical robust setae; inner ramus subequal in length to outer ramus, with 5 apical robust setae, marginal robust setae lacking.

Uropod 3 (Fig. 15 E ): diminutive, uniramous; peduncle 2 × length of ramus, with a robust seta and a simple seta; ramus with 2 robust setae.

Telson (Fig. 15 F ): fleshy, rounded, not narrowing distally, as long as broad, with 4 distal setae and 2 triplets of submarginal plumose setae flanking outer margins, apical margin not produced.

Female (Figs 3 D , 16 , 17 ): Allotype, USNM 1694155 , 3.62 mm in length. Differing from male in presence of weaker gnathopods with weaker carpals / propodi, and minor differences in uropod and telson setation. Structures not described below as in male.

Gnathopods. Gnathopod 1 (Fig. 16 A ): coxal plate with 5 short apical setae, basis narrowing proximally, lacking marginal posterior setae; ischium with 1 posterior seta; merus with 2 posterior setae, distoposterior surface of segment lacking comb-scales; carpus 90 % length of propodus, with a medial seta and a cluster of posterior serrulate setae, posterior surface of segment with comb-scales; propodus 1.2 × longer than broad with 3 inner medial serrulate setae, anterodistal corner with tuft of setae, comb-scales present along posterior margin; palm straight with 5–10 setae on inner / outer margins; defining angle straight with 3 robust setae; dactylus with plumose seta on outer margin, and 3 inner marginal setae, surface lacking comb-scales.

Gnathopod 2 (Fig. 16 B ): coxal plate with 4 short apical setae, basis narrowing proximally, lacking marginal posterior setae; ischium with 1 posterior seta; merus with 2 posterior setae, distoposterior surface of segment lacking comb-scales; carpus 70 % length of propodus, posterior margin lobate, with sparse comb-scales; propodus 1.4 × longer than broad, with 3 inner medial setae, anterodistal corner with tuft of setae, comb-scales present along posterior margin; palm straight with 5–12 setae on inner / outer margins; defining angle with 2 robust setae and 4 additional submarginal robust setae; dactylus with plumose seta on outer margin, and 3 inner marginal setae, surface lacking comb-scales.

Brood plates. (Fig. 16 B ): large setaceous brood plates present on somites 2–5, decreasing in size posteriorly.

Urosome. Somites free, bare dorsally. Uropod 1 (Fig. 17 A ): peduncle 1.4 × length of outer ramus with 5 outer robust setae and an inner seta; rami narrowing slightly distally, outer ramus with 3 marginal robust setae, and 4 apical robust setae; inner ramus 90 % of outer ramus with 5 apical robust setae, lacking marginal robust setae.

Uropod 2 (Fig. 17 B ): peduncle subequal to rami, with 1 inner seta and 2 outer robust setae; rami not narrowing distally, outer ramus with 1 marginal robust seta, and 4 apical robust setae; inner ramus subequal in length to outer ramus with 5 apical robust setae, marginal robust setae absent.

Uropod 3 (Fig. 17 C ): diminutive, uniramous; peduncle 1.5 × length of ramus, with a robust seta and a seta; ramus with 3 robust setae.

Telson (Fig. 17 D ): fleshy, rounded, not narrowing distally, as long as broad, with 4 distal setae and 3 pairs of submarginal plumose setae flanking outer margins, apical margin not produced.

Variation.

Individuals examined were shown to vary significantly in several morphological characteristics (Table 3 ).

Distribution and ecology.

Hyalella keepuikantun sp. nov. is known only from its type locality, Devils Hole II (also known as Devils Hole Cave), in Nye County, Nevada, USA. Devils Hole II is located ~ 200 m north of Devils Hole, and is a separate cave system, manifesting as a small pit opening one meter by half a meter, then opening up to a nearly vertical pit ~ 40 m deep where it meets the water table ( Hoffman 1988). As a result, Devils Hole II is less exposed when compared to its sister site, and epigean species such as the Devils Hole pupfish ( Cyprinodon diabolis ) are absent ( Hoffman 1988). An unidentified species of Ostracoda has been found co-occurring with H. keepuikantun , but no other known species of aquatic invertebrates have been found in Devils Hole II (Kevin Wilson personal communication). Surveys of the cave have noted water depths of at least 21 meters, but the total depth is likely significantly deeper; its connections to Devils Hole and the rest of the basin remain unknown ( Hoffman 1988). Hyalella keepuikantun sp. nov. has only been found near the surface of the water in Devils Hole II, where it was collected near bat guano and small, floating, calcite rafts. Devils Hole II is located on a disjunct 16 - hectacre (40 acre) portion of Death Valley National Park, owned and managed by the National Park Service. Additionally, it is surrounded by Ash Meadows National Wildlife Refuge, managed by the US Fish and Wildlife Service, and the Ash Meadows Area of Critical Environmental Concern ( ACEC), managed by the Bureau of Land Management.

Figures

Figure 3. Habitus photographs A Hyalella plutonia sp. nov. holotype male, unnamed spring, ~ 0.7 km north of Hwy 95 and Oleo Rd, Nye County, Nevada, USA (USNM 1694150), 4.20 mm B Hyalella plutonia sp. nov., allotype female, unnamed spring, ~ 0.7 km north of Hwy 95 and Oleo Rd, Nye County, Nevada, USA (USNM 1694151), 3.25 mm C Hyalella keepuikantun sp. nov., holotype male, Devils Hole II, Nye County, Nevada, USA (USNM 1694154), 3.48 mm D Hyalella keepuikantun sp. nov., allotype female, Devils Hole II, Nye County, Nevada, USA (USNM 1694155), 3.62 mm.

Figure 11. Hyalella keepuikantun sp. nov., holotype male, Devils Hole II, Nye County, Nevada, USA (USNM 1694154), 3.48 mm A antenna 1 (single aesthetasc enlarged) B antenna 2 C left mandible D right mandible (lacinia mobilis enlarged). Scale bars: 0.25 mm (A, B); 0.1 mm (C, D).

Figure 12. Hyalella keepuikantun sp. nov., holotype male, Devils Hole II, Nye County, Nevada, USA (USNM 1694154), 3.48 mm A upper lip B lower lip C maxilla 1 (outer plate serrate setae enlarged) D maxilla 2 E maxilliped (apical margin of inner plate enlarged). Scale bars: 0.1 mm.

Figure 13. Hyalella keepuikantun sp. nov., holotype male, Devils Hole II, Nye County, Nevada, USA (USNM 1694154), 3.48 mm A gnathopod 1 (palmar margin and dactylus enlarged) B gnathopod 2 (palmar margin and dactylus enlarged). Scale bar: 0.25 mm.

Figure 14. Hyalella keepuikantun sp. nov., holotype male, Devils Hole II, Nye County, Nevada, USA (USNM 1694154), 3.48 mm A pereopod 3 B pereopod 4 C pereopod 5 D pereopod 6 E pereopod 7. Scale bar: 0.25 mm.

Figure 15. Hyalella keepuikantun sp. nov., holotype male, Devils Hole II, Nye County, Nevada, USA (USNM 1694154), 3.48 mm A epimera B pleopod 1 (coupling spine enlarged) C uropod 1 D uropod 2 E uropod 3 F telson. Scale bars: 0.25 mm (A, B); 0.1 mm (C – E).

Figure 16. Hyalella keepuikantun sp. nov., allotype female, Devils Hole II, Nye County, Nevada, USA (USNM 1694155), 3.62 mm A gnathopod 1 (palmar margin and dactylus enlarged) B gnathopod 2 (palmar margin and dactylus enlarged). Scale bar: 0.25 mm.

Figure 17. Hyalella keepuikantun sp. nov., allotype female, Devils Hole II, Nye County, Nevada, USA (USNM 1694155), 3.62 mm A uropod 1 B uropod 2 C uropod 3 D telson. Scale bars: 0.1 mm.