Ligidium gadalutsi Recuero & Caterino, 2025, sp. nov.

Ligidium gadalutsi sp. nov. urn:lsid:zoobank.org:act: 3EAEAB27-5C45-4183-9B5D-70FB794D8094 Figs 8–9 Ligidium sp. 4 – Recuero & Caterino 2024: table 1. Diagnosis This new species differs from all other Appalachian species in its male pleopod 2 endopodite having an acuminate tip, strongly projected posteriorly and outwards. It has a distinctive male pleopod 1 endopodite, showing a poorly defined, broadly triangular projection, and a male pleopod 1 exopodite with its caudal margin flattened. It also differs from all other Appalachian species based on molecular data, representing a distinct evolutionary lineage with no close relationships among the studied taxa. Etymology A noun in apposition, ‘ gadalutsi ’ is the Cherokee word that originated the name Cataloochee, and consequently the origin of the name of the type locality, Big Cataloochee Mountain. Material examined Holotype USA – North Carolina • ♂; Haywood Co., Great Smoky Mountains N.P., Big Cataloochee Mt; 35.6675° N, 83.1805° W; 1703 m a.s.l.; 14 Jul. 2020; M. Caterino and F. Etzler leg.; GenBank no: PP737148 (Cox1); USNM, CUAC000138053. Other material examined USA – North Carolina • 1 ♀; Clay Co., Nantahala N.F., Chunky Gal Trail; 35.1471° N, 83.7144° W; 1274 m a.s.l.; 6 Jul. 2021; M. Caterino and E. Recuero leg.; CUAC000171281. – Tennessee • 1 ♀; Sevier Co., Smoky Mountains N.P., Mount LeConte (Alum Cave Trail); 35.6382° N, 83.4387° W; 1317 m a.s.l.; 28 Sep. 2021; M. Caterino and E. Recuero leg.; CUAC000171324. Description Body length of holotype 4.9 mm, width (at 4 pereonite) 2.4 mm; body length of females 5.5–7 mm, width 2.5–3.6 mm. Color in ethanol (Fig. 8) of holotype dorsally marbled brown and white, with a conspicuous dark brown longitudinal medial stripe running from pereonite 1 to pereonite 7 and a transversal dark brown band in the caudal margin of pereonites; epimera dark brown with a large white patch at the base; pleonites dark brown with lateral white spots; telson dark brown with a white anchor-shaped spot; head and antennae marbled brown and white, distal segments of antennae darker brown with white setae bundle in flagellum; uropod brown with a white spot in the inner part of basipodite; pereopods and pleopods white with brown marbling. Among females one resembles the holotype in coloration, the other is dorsally almost black with large white spots from head to telson. Antennule (Fig. 9G) three-segmented; first segment about 1.5–1.7 times as long as wide, 2–3 spiniform setae in its distal border; second segment about 2.3–2.5 times as long as wide, bearing 3 strong spiniform setae in the distal border; third segment with blunt apex and 2 setae. Antennae (Fig. 9F) with 5 segmented peduncle, relative size of antennomeres 5>4>3>2>1; antennal flagellum with 11 articles. Dactylus of pereopods with outer claw longer than inner one, inner one reduced in pereopod 1; no sexual dimorphism observed in pereopods 1 (Fig. 9H) and 7 (Fig. 9I). Male pleopod 1 endopodite (Fig. 9A) with short, blunt projection, bearing a single strong, blunt seta, 0.8 times as long as endopodite; caudal and inner margins with pilose setae. Pleopod 1 exopodite (Fig. 9B) with flat caudal margin bearing 4 strong, blunt setae, up to 0.8 times as long as exopodite. Male pleopod 2 exopodite (Fig. 9C) 1.9 times as wide as long; inner and half of the frontal margin with dense, hairy setation, as in outer caudal corner; caudal margin evenly convex, with 2 short, strong setae in the outer corner. Male pleopod 2 endopodite (Fig. 9D–E) with a broad and acuminate tip, projected posteriorly-laterally, with small setae in the interior margin; inner margin of the peduncle with minute spiniform setae, no spines at base. Telson (Fig. 8) with caudal margin slightly concave in the sides and obtusely produced in the middle. Uropod (Fig. 9J) with endopodite 1.3–1.4 times as long as exopodite when not broken, and about 2 times as long as basipodite. Distribution The species has been found in two localities in the Great Smoky Mountains and one at the Nantahala National Forest further south, at mid- to high elevations (Fig. 8). Studied specimens have been collected in leaf litter from conifer and mixed forests. Remarks Ligidium gadalutsi sp. nov. corresponds with Ligidium sp. 4 in Recuero & Caterino (2024a). It is not closely related to any of the studied Appalachian species (Fig. 1A). The shape of the male pleopod 2 endopodite somewhat resembles that of L. mucronatum, which could indicate a shared ancestry. However, in L. mucronatum the tip is shorter and blunt, while much longer and acuminate in L. gadalutsi. This new species shows the highest genetic p-distances compared to all other studied species (Supp. file 1).