Stygobromus estesi Holsinger 1978

Stygobromus estesi

MATERIAL EXAMINED.—VIRGINIA. Craig Co.: Rufe Caldwells Cave, holotype (USNM 168813), 3 paratypes (JRH). J. R. Holsinger, L. M. and B. L. Ferguson, 19 Apr 1975; New Castle Murder Hole (cave), 1 paratype (JRH), J. A. Estes, 1 Mar 1975.

DIAGNOSIS.—A moderately small cavernicolous species, closely related to S. ephemerus, but distinguished from that species by having more spine teeth on gnathopod propods, more setae on margins of coxal plates of gnathopod 2 and pereopods 3 and 4 and on posterior margins of pleonal plates 2 and 3, more spines on uropods 1 and 2, and by the apical margin of the telson, which has a shallow notch and 12 spines. Largest female, 5.8 mm; male unknown.

FEMALE.—Antenna 1 about 50 percent length of body, 45–50 percent longer than antenna 2; primary flagellum with 17 or 18 segments. Antenna 2, flagellum with 6 or 7 segments. Mandibles subequal; spine row with 5 or 6 spines; segments 2 of palp with 4 long setae on inner margin, segment 3 with 1 long seta on outer margin, row of short setae on inner margin, 6 setae of unequal length on apex. Maxilla 1: inner plate with 5 apical, plumose setae; palp with 3 slender spines and 4 or 5 setae on apex. Maxilla 2, inner plate with oblique row of 6 plumose setae on inner margin. Maxilliped: inner plate apically with 2 bladelike spines, 1 plumose spine, and 1 naked seta, subapically with 1 plumose spine (or seta); outer plate with naked setae on inner margin and apex and 2 plumose setae apically. Inner lobes of lower lip small to vestigial.

Propod of gnathopod 1 a little larger than 2nd propod; palm slightly concave, armed with double row of 6 or 7 spine teeth; defining angle with 2 long spine teeth on outside, 4 shorter ones on inside; medial setae few, singly inserted. Coxal plate of gnathopod 1 longer than broad, with 2 marginal setae. Gnathopod propod 2: palm with double row of about 8 spine teeth; defining angle with 1 long spine tooth on outside, 3 shorter ones on inside; posterior margin 3 or 4 sets setae; medial setae mostly singly inserted. Coxal plates of gnathopod 2 and pereopod 3 about as broad as long, margins with 6 or 7 setae each. Coxal plate of pereopod 4 about as broad as long, reaching 35–40 percent length of basis, margin with 8 setae. Pereopods 6 and 7 equal in length, 50 percent length of body, 20 percent longer than pereopod 5. Bases of pereopods 6 and 7 rather narrow, distoposterior lobes small and poorly developed. Dactyls of pereopods 6 and 7, 35–40 percent length of corresponding propods; dactyl of pereopod 5, 30–35 percent length of corresponding propod. Three rather long median sternal gills on pereonites 2–4; 2 pairs simple lateral sternal gills on pereonites 6 and 7; sternal gills absent from pleonite 1. Brood plates sublinear, not expanded distally.

Pleonal plates: posterior margins of plates 1 and 2 weakly convex, with 1–3 setae each, posterior margin of plate 3 strongly convex, with 3 or 4 setae; posterior corners of plates 2 and 3 small and narrowly rounded, that of plate 1 indistinct; ventral margin of plate 2 with 1–3 spines, that of plate 3 with 3 or 4 spines. Uronites fused. Uropod 1: inner ramus slightly shorter than outer ramus, 60 percent length of peduncle, armed with 11 spines; outer ramus with 11 spines; peduncle with 11 spines. Uropod 2: inner ramus longer than outer ramus, a little shorter than peduncle, armed with 10 spines; outer ramus with 7 spines; peduncle with 5 spines. Uropod 3 lacking ramus, peduncle with 1 apical spine. Telson a little longer than broad; apical margin with shallow notch, armed with 12 spines.

(cave), Virginia: a, left mandible; b, dentate part of right mandible; c, lower lip; d, apical part of inner plate of maxilliped (greatly enlarged); e, f, gnathopods 1, 2; g, pleonal plates; h, telson; i, uropod 3; j, lateral sternal gill.

TYPE-LOCALITY.—Rufe Caldwells Cave, located 6.4 km southwest of New Castle in Craig Co., Virginia, is a medium-sized cave (with a small stream) developed in Middle Ordovician limestone.

DISTRIBUTION AND ECOLOGY.—This species is known only from two caves which are located 2.3 km apart near the head of a karsted limestone cove formed between Sinking Creek and Johns Creek mountains. Both caves are situated in the James River drainage basin just east of the limestone interfluve between Sinking Creek (New River drainage) and Meadow Creek (James River drainage). The range of this species is approximately 29 km northeast of the range of S. ephemerus. In both caves, S. estesi has been collected from mud-bottom pools fed by drips and seeps. Two females (4.5 and 5.5 mm) from the April collection in Rufe Caldwells Cave had setose brood plates. In New Castle Murder Hole, this species occurs sympatrically with S. interitus, new species (p. 95), and an undecided form closely related to S. mackini (see “Stygobromus species”).

ETYMOLOGY.—It is a pleasure to name this species in honor of James A. Estes, who first discovered it in New Castle Murder Hole.