Stygobromus emarginatus (Hubricht 1943)

Stygobromus emarginatus (Hubricht)

Synpleonia emarginata Hubricht, 1943:707–708, pl. 9 [in part] [type-locality: Organ Cave, Greenbrier Co., West Virginia].

Stygonectes emarginatus (Hubricht).—Holsinger, 1967:23–26, fig. 2; 1969a:32–33.—Culver and Holsinger, 1969–632.—Poulson and White, 1969:975.—Culver, 1970a:949; 1970b:464; 1971a:173; 1971b:98.—Culver and Poulson, 1971:74.—Holsinger, 1972:59.—Culver, 1973:103.—Culver, Holsinger, and Baroody, 1973:691.—Holsinger, Baroody, and Culver, 1976:23.—Rutherford and Handley, 1976:45.

Stygobromus emarginatus (Hubricht).—Karaman, 1974:110.—Holsinger, 1977:261.

MATERIAL EXAMINED.—MARYLAND. Garrett Co.: John Friends Cave, 2 , 1 (Holsinger, 1967:23). WEST VIRGINIA. Greenbrier Co.: Benedicts Cave, 1 , WVACS, 18 Jan 1966; Bransfords Cave, 1 , J. R. Holsinger and P. Hightower, 2 Jul 1966; Court Street Cave, 15 , 4 (Holsinger, 1967:23); dug-out spring near Coffmans Cave, 1 , 1 , S. W. Hetrick, 13 May 1972; Fox Cave, 1 (Holsinger, 1967:23); Fuells Fruit Cave, 1 , D. C. Culver, 18 Jun 1967; Grapevine Cave, 1 , J. R. Holsinger and J. O. Davis, 28 Aug 1967; The Hole (cave), 1 specimen (D. C. Culver coll.), D. C. Culver and W. W. Biggers, 31 Mar 1967, and 1 , J. M. Rutherford, Jr., 22 Jul 1967; Levisay Cave, 1 specimen (D. C. Culver coll.), D. C. Culver and W. W. Biggers, 29 Mar 1967; Organ Cave (system), 9 collections (26 , 9 , 1 juv.) from 1939–1970 (Holsinger, 1967:23); Wades Caves, 2 , WVACS, 23 Apr 1966; Monroe Co.: Coburn Cave, 1 , J. R. Holsinger and G. W. Frederick, 30 May 1969, and 2 , J. R. Holsinger, 28 Jun 1974; McClung-Zenith Cave, 1 , J. R. Holsinger, R. A. Baroody, and D. J. Newson, 31 Aug 1967; Rock Camp Cave, 1 , 1 , T. C. Barr, Jr. and J. H. Carpenter, 1 Jul 1968; Pendleton Co.: Kenny Simmons Cave, 2 , J. R. Holsinger, 25 Aug 1966; Pocahontas Co.: Linwood Cave, 2 , J. R. Holsinger, 22 Aug 1966; Marthas Cave, 1 , 1 , T. C. Barr, Jr., 28 Jul 1966, and 1 , J. R. Holsinger and D. C. Culver, 14 Jan 1967; Upper Marthas Cave, 1 , D. C. Culver, 21 Nov 1967; Piddling Pit (cave), 1 , J. R. Holsinger, R. A. Baroody, and R. L. Swensson, 30 Sep 1967, and 1 , J. R. Holsinger and D. C. Culver, 12 Aug 1972; Poor Farm Cave, 1 , J. R. Holsinger, 4 May 1968; Randolph Co.: Bazzle Cave, 1 , J. R. Holsinger and D. C. Culver, 21 May 1973; Bowden Cave, 2 , 1 , J. R. Holsinger and D. C. Culver, 22 May 1973; Tucker Co.: Big Springs Cave, 5 , J. R. Holsinger, 24 Aug 1966; Harpers Cave, 1 , A. and B. Norden, Jan 1974.

DIAGNOSIS AND DESCRIPTION.—Corresponding to earlier diagnoses and descriptions by Hubricht (1943) and Holsinger (1967) with the following additions and variation: Largest males, 11.2 mm; largest females, 14.0 mm. Antenna 1 with up to 23 primary flagellar segments; antenna 2 with up to 8 flagellar segments. Maxilliped: inner plate with 4 or 5 bladelike spines, 3 plumose spines and 2 naked setae apically and 1 or 2 plumose setae or spines on inner margin distally; outer plate with naked setae on inner margin and apex, 2 plumose setae apically. Defining angle of 2nd gnathopod propod with 1, or rarely 2, long spines on outside; posterior margin with 4–8 sets setae (but usually 5 or 6). Lateral sternal gills bifurcate. Brood plates of sexually mature females rather narrow but somewhat expanded distally. Uronites completely or incompletely fused. Ramus of uropod 3 with typically 3 apical spines but occasionally 2 or 4. Telson somewhat variable in shape (Figure 2), occasionally slightly broader distally than proximally; apical margin usually with slight notch but occasionally without, armed with 10–20 spines but more commonly with 12–16.

DISTRIBUTION AND ECOLOGY.—During the preparation of my 1967 monograph on Stygonectes, this species was known only from three caves in Greenbrier Co., West Virginia, and one cave in Garrett Co., Maryland. Since that time the species has been found in numerous caves in eastern West Virginia as indicated. The range of S. emarginatus, the third longest of the cave species treated in this paper, extends for a linear distance of 274 km from Monroe County in southeastern West Virginia north-northeast to Garrett County in western Maryland. Except for the localities in Monroe and Pendleton counties, this species is known only from caves developed in the Greenbrier limestone of Mississippian age.

Stygobromus emarginatus is predominately an inhabitant of small, gravel-bottom cave streams, although a few samples have been taken from pools fed by drips and seeps. A single collection was also made from the gravels of a recently excavated spring in Greenbrier County, this being the only noncave locality recorded for this species to date. Samples have been made during all seasons of the year, but females with setose brood plates (size range = 8.5–13.5 mm) have so far been found only during spring and summer. Ovigerous females are known only from an August collection in Court Street Cave in Greenbrier County (Holsinger, 1967:26). Detailed studies on the microhabitat of this species and its interaction with other amphipod species (i.e., Stygobromus spinatus Holsinger and Gammarus minus Say) and an isopod (Asellus sensu lato holsingeri Steeves) in caves of the Greenbrier Valley of West Virginia have been published by Culver (1970a).

Stygobromus emarginatus, commonly called Greenbrier cave amphipod, is a troglomorphic species of amphipod in family Crangonyctidae. It is native to Maryland and West Virginia in the United States.