Stygobromus inexpectatus Holsinger 1978

Stygobromus inexpectatus

Stygobromus species.—Holsinger and Peck, 1971:30 [in part].

MATERIAL EXAMINED.—ALABAMA. Calhoun Co.: Meadows Cave, holotype (USNM 168827), 6 , 1 and 3 juv. paratypes (JRH), S. B. Peck, L. Guy, and G. McCluskey, 3 Sep 1968.

DIAGNOSIS.—A medium-sized cavernicolous species closely related to S. ackerlyi but distinguished from that species by fewer setae on outer margin of gnathopod dactyls, larger coxal plate of pereopod 4 which is about 2/3 length of basis, proportionately broader bases of pereopods 5–7, proportionately larger pleonal plates with more ventral marginal spines, fewer spines on inner ramus but more spines on peduncle of uropod 1, and proportionately longer telson with shallower apical notch. Largest male (immature ?), 4.5 mm; largest female, 7.7 mm.

FEMALE.—Antenna 1, 40–45 percent length of body, 40 percent longer than antenna 2; primary flagellum with 15 segments. Antenna 2, flagellum with 6 segments. Mandible, maxilliped, and lower lip like those of S. ackerlyi. Maxilla 1: inner plate with 6 apical, plumose setae; palp with 2 slender spines and 5 setae apically. Maxilla 2, inner plate with oblique row of 7 or 8 plumose setae on inner margin. Gnathopod 1 about like that of S. ackerlyi except outer margin of dactyl with 1 seta instead of 4. Gnathopod propod 2: palm with double row of 14 or 15 spine teeth; defining angle with 3 long spine teeth on outside, 5 shorter ones on inside; posterior margin with 3 or 4 sets setae; medial setae mostly singly inserted. Coxal plates of gnathopod 2 and pereopod 3 like those of S. ackerlyi. Coxal plate of pereopod 4 rather broad and deep, reaching about 2/3 length of basis, margin with 9 setae. Pereopod 6 subequal in length to pereopod 7, 40–45 percent length of body, 15–20 percent longer than pereopod 5. Pereopods 5–7: bases broader proximally than distally, posterior margins broadly convex, distoposterior lobes broadly rounded; dactyls 34–39 percent length of corresponding propods. Gills and brood plates like those of S. ackerlyi.

Pleonal plates: posterior margins of 1 and 3 convex, that of 2 nearly straight, margins with 1 seta each; posterior corners small, 1 and 2 bluntly rounded, 3 more narrowly rounded; ventral margins of plates 2 and 3 with 4 or 5 spines. Uronites free. Uropod 1: inner ramus slightly longer than outer ramus, 70–75 percent length of peduncle, armed with 8 or 9 spines; outer ramus with 12 or 13 spines; peduncle with 18 or 19 spines. Uropods 2 and 3 about like those of S. ackerlyi. Telson 25–30 percent longer than broad, gently tapering distally; apical margin with shallow notch, armed with 16–18 spines.

MALE.—Single specimen in collection apparently immature; differing from female by having few less spines and setae on most appendages. Peduncular process of uropod 1 short, apex trilobed.

TYPE-LOCALITY.—Meadows Cave which, according to S. B. Peck who collected the type series, is located 1.6 km northwest of Weaver in Calhoun Co., Alabama. This is a small cave with several pools but apparently no flowing stream (see map 94 in Tarkington, Varnedoe, and Veitch, 1965; Varnedoe, 1973). Varnedoe (1973:33) indicated that Meadows Cave was developed in the Fort Payne chert (Mississippian age), but on the basis of the Geological Map of Alabama, by Adams, et al. (1926) it would be in Cambrian limestone or dolomite.

DISTRIBUTION AND ECOLOGY.—This species is known only from its type-locality, which is located approximately 61 km southwest of Cave Springs Cave (see S. ackerlyi, above) in the Coosa River drainage. Only a single female (7.7 mm) in the type series had setose brood plates.