Stygobromus carolinensis Holsinger 1978

Stygobromus carolinensis

MATERIAL EXAMINED.—NORTH CAROLINA. Yancey Co.: seeps on W side of state route 128, 2.4 km N of Blue Ridge Parkway, holotype (USNM 168803), 17 and 3 paratypes (USNM), 34 and 5 paratypes (JRH), L. Hubricht, 15 Sep 1971.

DIAGNOSIS.—A relatively small to medium-sized groundwater species distinguished from other members of the sparsus subgroup by the absence of sternal gills. Further distinguished from S. sparsus by the presence of a tiny ramus on uropod 3. Largest male, 4.3 mm; largest female, 5.5 mm.

FEMALE.—Antenna 1, 40–45 percent length of body, 40–45 percent longer than antenna 2; primary flagellum with 12 segments. Antenna 2, flagellum with 4–6 segments. Mandibles subequal; spine row with 4 or 5 spines; segment 2 of palp with about 5 setae of unequal length on inner margin, segment 3 with 1 long seta on outer margin, 1 long seta and row of short setae on inner margin, and 3 long setae apically. Maxilla 1: inner plate with 7 apical, plumose setae; palp with 2 slender spines and 3 stiff setae apically. Maxilla 2, inner plate with oblique row of 7 plumose setae on inner margin. Maxilliped: inner plate with 2 baldelike spines, 1 plumose spine and 2 naked setae apically; outer plate with naked setae on inner margin and apex and 1 lightly plumose seta on apex. Inner lobes of lower lip small to vestigial.

Propod of gnathopod 1 slightly smaller than 2nd propod; palm armed with double row of 6 or 7 spine teeth; defining angle with 2 long spine teeth on outside, 2 shorter ones on inside; posterior margin with 3 setae; medial setae singly inserted. Dactyl nail of gnathopod 1 moderately long. Coxal plate of gnathopod 1 about as broad as long, margin with 2 setae. Gnathopod propod 2: palm armed with double row of 6 or 7 spine teeth; defining angle with 1 long spine tooth on outside, 3 shorter ones on inside; posterior margin with 3 sets setae; medial setae singly inserted. Dactyl nail of gnathopod 2 moderately long. Segment 5 of gnathopod 2 without rastellate setae. Coxal plate of gnathopod 2 about as broad as long, margin with 3 setae. Coxal plate of pereopod 3 a little longer than broad, margin with 5 setae. Coxal plate of pereopod 4 a little longer than broad, reaching about 45 percent length of basis, margin with 7 setae. Pereopod 6 a little longer than pereopod 7, 45 percent length of body, about 20 percent longer than pereopod 5. Bases of pereopod 6 and 7 narrowing somewhat distally, distoposterior lobes distinct, bluntly rounded. Dactyls of pereopods 5–7, 32–37 percent length of corresponding propods. Coxal gill absent from pereopod 7. Sternal gills absent. Brood plates relatively narrow but somewhat expanded distally.

Pleonal plates: posterior margins of plates 1 and 3 convex, that of plate 2 nearly straight, margins with 1 seta each; posterior corners rounded and indistinct; ventral margin of plate 2 with 2 spines, that of plate 3 with 3 spines. Uronites free. Uropod 1: inner ramus subequal in length to outer ramus, about 55 percent length of peduncle, armed with 11 spines; outer ramus with 7 spines; peduncle with 11–13 spines. Uropod 2: inner ramus longer than outer ramus, a little shorter than peduncle, armed with 12 spines; outer ramus with 6 or 7 spines; peduncle with 4 or 5 spines. Uropod 3: ramus tiny, only about 1/10 length of peduncle, with 1 apical spine. Telson about as broad as long; apical margin incised about 25 percent the distance to base, armed with 12 spines.

MALE.—Differing only slightly from female as follows: Gnathopods with few less setae and spines. Uropod 1: inner ramus with 10 spines; peduncle with 8 spines; peduncular process similar that described for S. barryi. Uropod 2: inner ramus with 10 spines; peduncle with 3 spines. Telson with 12 to 16 apical spines.

TYPE-LOCALITY.—The type-series was obtained from groundwater seeps on the west side of North Carolina Route 128, 2.4 km north of the Blue Ridge Parkway in Mt. Mitchell State Park (Yancey Co., North Carolina). This locality, approximately 2.4 km southwest of the summit of Mt. Mitchell, is underlain by metamorphic rocks of Precambrian age and is drained to the north and west by tributaries of the Nolichucky River (upper Tennessee River drainage basin).

DISTRIBUTION AND ECOLOGY.—This species is known only from its type-locality. Its range is situated approximately 26 airline miles (42 km) south of the range of S. barryi and in the same drainage basin. Of the 52 females in the type-series, 11 had setose brood plates and ranged in length from 4.0 to 5.0 mm.

ETYMOLOGY.—The specific name refers to the occurrence of this species in the state of North Carolina.

The grandis Subgroup

DIAGNOSIS.—Adults large (ca. 12.0–19.0 mm). Gnathopod propods proportionately larger than in other species of the mackini group. First gnathopod propod subtriangular, slightly larger than 2nd propod; segment 5 without rastellate setae. Dactyl nails of gnathopods reduced. Posterior margins of pleonal plates with 1 seta each. Telson incised 65 percent the distance to base.