Stygobromus hubbsi Shoemaker 1942

Stygobromus hubbsi Shoemaker

Stygrobromus hubbsi Shoemaker, 1942b:1–6, figs. 1–2.—Hubricht, 1959:878.—Nicholas, 1960:128—Bousfield, 1961:2–3.—Holsinger, 1972:68–69, 72, fig. 26f.

MATERIAL EXAMINED.—OREGON. Harney Co.: Malheur Cave, holotype male (USNM 98404) and 104 paratypes (USNM 98405 and 80528), Carl L. Hubbs, 27 July 1928; additional specimens collected include 1 female by Virginia M. Tipton, 9 Aug. 1969 (JRH) and 2 juveniles by W. R. Elliott et al., 9 Aug. 1972 (JRH).

DIAGNOSIS.—A medium-sized cavernicolous species bearing a close morphological affinity with the cave species of east-central California (especially S. grahami, S. harai, and S. wengerorum) but distinguished by having fewer plumose setae on the inner plates of maxillae 1 and 2; fewer apical spines on the inner plate of the maxilliped; only 8 or 9 apical spines on the telson; and other characters noted in the descriptions below. Largest females, 6.5 mm; largest males, 5.5 mm.

This description corresponds to Shoemaker’s (1942b) with the following additions and modifications: Antenna 1 about 45 percent as long as body, 50 percent longer than antenna 2; primary flagellum with up to 15 segments. Antenna 2, flagellum with 5 or 6 segments. Maxilla 1, inner plate with 8 or 9 apical, plumose setae. Maxilla 2, inner plate with 9 or 10 obliquely placed, plumose setae on inner margin. Maxilliped: inner plate armed apically with 4 or 5 bladelike spines, several stiff setae and 2 or 3 plumose spines; outer plate with 1 bladelike spine and a number of stiff setae apically and subapically.

Gnathopod 1: Propod palm slightly convex, armed with double row of 9 or 10 spine teeth; posterior angle with 1 long and 3 shorter spine teeth on outside, 5 spine teeth (some forked) on inside; posterior margin comparatively short, about one-third the length of palm, without setae or spines. Coxal plate of gnathopod 1 longer than broad, with 4 or 5 marginal setae. Gnathopodal propod 2 up to one-third larger than 1st, about 50 percent longer than broad; palm long, oblique, slightly concave proximally, with double row of 11 or 12 spine teeth, plus 3 additional spine teeth on outside; posterior angle with 1 long, curved spine and several long setae on outside, 3 shorter spine teeth on inside; posterior margin with 2 or 3 sets of long setae; superior medial setae singly and doubly inserted, inferior medial setae singly inserted; dactyl long and curved, nail rather long. Coxal plates of gnathopod 2 and pereopod 3 longer than broad, with 8 to 10 marginal setae; coxal plate of pereopod 4 about as broad as long, with 12 marginal setae. Pereopod 6 about 50 percent longer than body, slightly longer than pereopod 7, 20 to 25 percent longer than pereopod 5. Bases of pereopods 5–7 rather narrow, a little broader proximally than distally; distoposterior lobes small, rounded; dactyls comparatively long, about one-third the length of corresponding propods. Coxal gills present on pereopods 2–6. Brood plates of mature females small and narrow.

Pleonal Plates: Posterior margins slightly convex and bearing 1 seta each; posterior corners broadly rounded; ventral margin of plate 1 without spines, ventral margins of plates 2 and 3 with 4 and 5 spines, respectively. Uropod 1 of female: inner ramus shorter than peduncle, slightly longer than outer ramus, armed with 12 spines; outer ramus with 8 spines; peduncle with 17 or 18 spines. Uropod 2 of female: inner ramus about as long as peduncle, about one-third longer than outer ramus, armed with 10 spines; outer ramus with 5 spines; peduncle with 5 spines. Uropods 1 and 2 of male with a few less spines; distal peduncular process of uropod 1 rather short and triangular. Uropod 3: ramus about one-third the length of peduncle, armed apically with 3 slender spines. Telson longer than broad; apical margin with shallow notch; apical lobes usually with 4 (or rarely 5) spines each.

TYPE-LOCALITY.—Malheur Cave, Harney County, Oregon. The type-locality is a lava tube formed in basalt of Late Cenozoic age. The original type-series and subsequent topotypes were collected from a lake over a thousand feet within the cave. Malheur Cave is also the type-locality (and only known locality) for the unique troglobitic planarian Kenkia rhynchida, described by Hyman (1937) and discussed more recently by Kenk (1972). In addition, the cave contains a tiny, white, eyeless isopod of the genus Asellus. The isopod, presumably undescribed, is known only from three females (1 ovigerous) collected along with two specimens of S. hubbsi by W. R. Elliott et al. in August 1972. The material is deposited in the National Museum of Natural History.

DISTRIBUTION AND ECOLOGY.—Stygobromus hubbsi is known only from its type-locality, where it is associated with the troglobitic planarians and isopods noted above. The majority of specimens collected have been females, but none were ovigerous and nothing is known about the life history of this species.

COMMENTS.—Although Shoemaker’s 1942 description of this species was adequate, I found it necessary to give more detailed figures of some of the appendages as shown. In my recent identification manual of freshwater amphipods (Holsinger, 1972), I inadvertently misplaced the location of Malheur Cave on the distribution map for S. hubbsi. The location shown on the map in Figure 36 (herein) is correct.

Stygobromus hubbsi, commonly called Malheur Cave amphipod, is a troglomorphic species of amphipod in family Crangonyctidae. It is endemic to Oregon in the United States. It is only found in Malheur Cave, which is a 3,000 ft (910 m) long lava tube.

Stygobromus hubbsi é uma espécie de crustáceo da família Crangonyctidae.

É endémica dos Estados Unidos da América.

Stygobromus hubbsi là một loài giáp xác trong họ Crangonyctidae. Chúng là loài đặc hữu của Hoa Kỳ.