Ligidium nantahala sp. nov.

urn:lsid:zoobank.org:act: A2CAA049-6BCB-4229-A06D-49F61B36B030

Figs 4–5

Ligidium sp. 2 – Recuero & Caterino 2024: table 1.

Diagnosis

Ligidium nantahala sp. nov. presents a male pleopod 2 endopodite with a robust excrescence occupying the inner part of the tip and projected outwards. The projection of male pleopod 1 endopodite presents a triangular profile. It also can be distinguished from all other Appalachian species based on molecular data, representing a distinct evolutionary lineage with no close relationships among the studied taxa.

Etymology

From the Cherokee Nantahala, the name of the forests where the species lives. A noun in apposition.

Material examined

Holotype

USA – North Carolina • ♂; Clay Co., Nantahala N.F., Chunky Gal Trail; 35.1471° N, 83.7144° W; 1274 m a.s.l.; 7 Jun. 2021; M. Caterino and E. Recuero leg.; GenBank no: OR169931 (Cox1); USNM, CUAC000180794.

Paratype

USA – North Carolina • 1 ♂; same data as for holotype; CUAC000180793.

Other material examined

USA – North Carolina • 1 imm. ♀; same data as for holotype; CUAC000171282 .

Description

Body length of adult males 4.9–5.5 mm, width (at pereonite 4) 2.4–2.6 mm. Color in ethanol of adult males (Fig. 4) dorsally marbled brown and white, with a conspicuous dark brown longitudinal medial stripe running from pereonite 1 to pereonite 7 and a transverse dark brown band in the caudal margin of pereonites; epimera dark brown with a large white patch at the base; pleonites dark brown caudally, lighter in the central parts (showing in pleonites 4–5 in dorsal view); telson dark brown with a white anchor-shaped spot; head marbled brown and white; antennae with basal segments white and brown, distally brown with some white marking; uropod brown with a large white spot in the basipodite; pereopods and pleopods white with brown marbling. Immature specimen with the same color pattern but lighter brown. Antennule (Fig. 5G) three-segmented; first segment about 1.6 times as long as wide, 3 spiniform setae on its distal border; second segment about 3 times as long as wide, also bearing 3 strong spiniform setae in the distal border; third segment small, with blunt apex and a single seta. Antennae (Fig. 5F) with 5 segmented peduncle, relative size of antennomeres 5>4>3>2>1; antennal flagellum with 10–11 articles. Dactylus of pereopods with outer claw longer than inner one; no sexual dimorphism observed in pereopods 1 (Fig. 5H) or 7 (Fig. 5I). Male pleopod 1 endopodite (Fig. 5A) with obtuse triangular projection, bearing 2 strong, blunt setae, 0.4–0.8 times as long as endopodite. Pleopod 1 exopodite (Fig. 5B) with rounded caudal margin bearing 2 strong, blunt setae, 0.4–0.6 times as long as exopodite. Male pleopod 2 exopodite (Fig. 5C) 1.6–1.7 times as wide as long; inner and frontal margins with limited pilose setation dense, present also along outer caudal corner; caudal margin markedly convex. Male pleopod 2 endopodite (Fig. 5D–E) with rounded tip and a soft, blunt, robust excrescence occupying most of inner part of tip and projecting outwards; inner margin with minute spiniform setae, no spines at the base. Telson (Fig. 4) with caudal margin obtusely produced, convex in immature female. Uropod (Fig. 5J) with exopodite and endopodite subequal in length when not broken, 1.5–1.7 times as long as basipodite.

Distribution

The species is so far only known from its type locality (Fig. 4). All specimens were collected in broadleaf forest leaf litter samples.

Remarks

Ligidium nantahala sp. nov. corresponds with Ligidium sp. 2 in Recuero & Caterino (2024a). It is not closely related to any of the other species studied here (Fig. 1A). Morphologically, the presence of a projecting excrescenceat the tip of male pleopod 2 endopodite resembles that observed in L. blueridgensis, L. pacolet sp. nov. and L. whiteoak sp. nov. However, the disposition of the excrescence is different in all four species. In L. nantahala it covers the whole inner part of the tip ventrally, and projects outwards. In L. blueridgensis the excrescence is more slender, and projects from the inner tip corner rising near the margin dorsally, and projecting caudally and inwards. Ligidium pacolet has also a more slender excrescence rising medially or near the inner corner from the end of the tip, projecting caudally or inwards. In L. whiteoak, the excrescence is broad, almost as much as the endopodite stem, rising dorsally and medially from the caudal margin of the tip and projecting caudally and slightly outwards. Ligidium nantahala differs also in the triangular shape of male pleopod 1 endopodite projection, squarish in the other mentioned species. All three gene fragments analyzed are informative to identify this species, with high genetic p-distances for Cox1 and even for the conserved NaK and 28S fragments (Supp. file 1), forming a monophyletic clade in all cases.