Stygobromus amicus Holsinger

Holsinger, John R. & Ansell, Lynnette, 2014, A new species of the subterranean amphipod genus Stygobromus (Amphipoda: Crangonyctidae) from two caves and a spring in western Maryland, USA with additional records of undescribed species from groundwater habitats in central Maryland, Zootaxa 3768 (3), pp. 386-394 : 387-392

publication ID	https://doi.org/ 10.11646/zootaxa.3768.3.6
publication LSID	lsid:zoobank.org:pub:3C538DA9-82AE-4E92-AE7B-1826A6442842
DOI	https://doi.org/10.5281/zenodo.6134162
persistent identifier	https://treatment.plazi.org/id/03EBAF45-FFC4-F967-FBA4-FA3BFDB9F9E8
treatment provided by	Plazi
scientific name	Stygobromus amicus Holsinger
status	sp. nov.

Treatment

Stygobromus amicus Holsinger View in CoL , sp. n.

Figures 2 View FIGURE 2 , 3 View FIGURE 3 , 4 View FIGURE 4 , 5 View FIGURE 5

Material examined. Holotype female 3.0 mm and 3 paratypes (2.5 – 3.0 mm), John Friend Cave, Garrett County, Maryland, 1.3 km WNW of Sang Run, Maryland, collected by Daniel Feller 28 Feb. 2009; additional 4 paratypes from same locality by Daniel Feller (29 Aug. 1992 and 11 Feb. 2006); 3 paratypes collected by Ben Hutchins, 12 July and 9 August 2007; and 6 paratypes collected by David C. Culver et al., January and May 2008. The holotype is deposited in the National Museum, Smithsonian Institution ( USNM 2060768); paratypes are in the research collection of J.R. Holsinger at Old Dominion University. Additional material from Garrett County tentatively assigned to this species includes: 1 female collected from Crabtree Cave by Richard Franz, 22 Oct. 1966 and 1 juvenile collected from High Rock Wildland Spring by Daniel Feller, 19 December 1988.

Diagnosis. Tiny, presumably rare species of troglomorphic facies distinguished by long, needle-like terminal spines on uropods 1 and 2; ramus of uropod 3 reduced in size and bearing single short spine; and convex apical margin of telson bearing few short spines.

Description. Antenna 1 ( Fig. 2 View FIGURE 2 a): 0.45–0.50% length of body, approximately 2X longer than antenna 2; primary flagellum with 9 or 10 articles, lacking aesthetacs, accessory flagellum approximately equal in length to first flagellar article. Antenna 2 ( Fig. 2 View FIGURE 2 b): flagellum with 2 articles. Mandibles ( Fig. 2 View FIGURE 2 c, d) subequal, differing in few minor ways: spine row of right with 2 lightly plumose spines, that of left with 3 such spines; left and right lacinia mobili are forked spines of unequal lengths; incisors 4–5 dentate, more strongly developed on right mandible; articles 1 and 2 of palps naked; article 3 with 4 apical E setae, 4 much shorter D setae on inner margin and 1 B seta on outer margin. Lower lip ( Fig. 2 View FIGURE 2 e): inner lobes vestigial. Maxilla 1 ( Fig. 2 View FIGURE 2 f): inner plate with 2 apical plumose setae; outer plate with 5 apical spines (some notched); palp with 4 apical spines. Maxilla 2 ( Fig. 2 View FIGURE 2 g): inner plate with 6 naked spines apically; outer plate with 7 rather long spines apically. Maxilliped ( Fig. 2 View FIGURE 2 h): inner plate with 4 short apical spines; outer plate with long row of inner marginal spines; palp article 2 broader and longer than article 1, inner margin with row of relatively long setae/spines; palp articles 3 and 4 much shorter, with spines/ setae; article 4 (dactyl) with prominent nail and 3 or 4 short spines/setae.

Gnathopod 1 ( Fig. 3 View FIGURE 3 a): propodus approximately 30% larger than propodus of gnathopod 2, palm nearly straight and relatively smooth, approximately equal in length to posterior margin, bearing uneven row of 7 or 8 small spines; dactyl nail ca. 60% length of dactyl; posterior margin with 4 spines; carpus about 75% length of propodus, bearing 5 long setae on ventral margin; coxa oblong, longer than broad, with 2 long, marginal setae. Gnathopod 2 ( Fig. 3 View FIGURE 3 b): propodus smaller than that of gnathopod 1, palm slightly curved, smooth, approximately 50% length of posterior margin, bearing 6 small spines; nail of dactyl approximately 75% length of dactyl; posterior margin nearly 2X length of palm, bearing 5 sets of 2 long setae each. Posterior margin of carpus of gnathopod 2 slightly convex, with 7 setae of unequal length. Coxa of gnathopod 2 rounded, bearing 1 marginal seta.

Pereopods 3 and 4 ( Figs. 4 View FIGURE 4 a, b): subequal, approximately equal in length to pereopod 5; coxae subquadrate, approximately equal in size, anterior margins convex, posterior margins nearly straight or slightly concave and without marginal setae, ventral margins convex, with 4 or 5 setae of unequal length. Pereopods 5, 6 and 7 ( Figs. 4 View FIGURE 4 c, d, e): pereopod 5 slightly shorter, coxa 2-lobate; pereopods 6 and 7 subequal in length, coxae smaller and rounded ventrally); dactyls relatively long, approximately 50% length of corresponding propodi. Coxal gills present on pereopods 5 and 7 (and possibly 6) small and subovate. Paired median sternal gills or processes on pereonites 6 and 7 ( Figs. 4 View FIGURE 4 d, e).

Pleonal plates generally similar ( Fig. 5 View FIGURE 5 a): ventral margins weakly convex, lacking spines or setae; posterior margins slightly expanded, subrounded, each with single seta; ventral margins lacking setae or spines. Pleopods ( Fig. 5 View FIGURE 5 b) biramous, articles bearing long, plumose setae; tiny coupling spines on inner margin of peduncles not shown. Urosomites not fused. Uropod 1( Fig. 5 View FIGURE 5 c): peduncle robust, longer than rami, with 3 short spines on upper margin; rami subequal in length, outer with 5 apical spines, one of which is much longer. Uropod 2 ( Fig. 5 View FIGURE 5 d): inner ramus longer and more robust than outer, approximately 75% length of peduncle, bearing 9 marginal spines; outer ramus bearing 5 apical spines of unequal length; peduncle with 3 short spines. Uropod 3 ( Fig. 5 View FIGURE 5 e): greatly reduced, only approximately 1/3 length of telson, outer ramus cap-like, bearing single short apical spine; telson ( Fig. 5 View FIGURE 5 f) relatively large, little longer than broad, apical margin convex and bearing 11 rather robust apical spines.

Type locality. John Friend Cave, 1.3 km WNW of Sang Run, Garrett County, Maryland ( Fig. 1 View FIGURE 1 ). See also Franz and Slifer (1971) for a detailed description and map of this cave.

Etymology. The epithet amicus is from the Latin meaning “friend” in recognition of “John Friend,” the longstanding name of the type-locality cave.

Distribution and ecology. This species is known to date primarily from drip pools in the type-locality John Friend Cave, and tentatively from a small stream in Crabtree Cave and High Rock Wildland Spring No 2, all three localities in Garrett Co., Maryland ( Fig. 1 View FIGURE 1 ).