Desoria uniens Christiansen and Bellinger, 1980

Fjellberg, Arne, 2010, Cryophilic Isotomidae (Collembola) of the Northwestern Rocky Mountains, U. S. A., Zootaxa 2513, pp. 27-49 : 31-32

Desoria uniens Christiansen and Bellinger, 1980

( Figs. 13–18 , 115B )

Type locality. Allegheny Mountains, Terra Alta, West Virginia ( Christiansen & Bellinger 1980: 761)

Material examined. Alaska: Clearwater Mountains, 63.20o N, 147.04o W, 30.VII.1980, alpine meadow 1,670 m., A. Fjellberg leg.; British Columbia: Vancouver Island, Comox Glacier, 26.VIII.1983, moss at melt water 1,850 m.; Sparwood, Bald Mountain, 7.VI.1983, moss at melt water 2,700m., A. Fjellberg leg.; Garibaldi Park, Panorama Ridge, 1.IXC.1983, wet moss at snow 1,920 m., A. Fjellberg leg.; Washington: Mount Rainier, Sugarloaf Mountain, 21.VIII.1980, moss at melt water, 2,400 m., A. Fjellberg leg.; Olympic National Park, Hurricane Ridge, 10.IX.1983, wet moss at snow 1,940 m., A. Fjellberg leg.; Nisqually Glacier, summer 2003, P. Hartzell leg.; Oregon: Zigzag South, summer 2003, P. Hartzell leg.; Colorado: Boulder County, Upper Diamond Lake, 26.VIII.1980, wet moss at snow 3,550 m., A. Fjellberg leg.

Redescription. Body size up to 1.6 mm. Body shape slender, normal for the genus ( Fig. 115B ). Head not prognathous. Abd. 5–6 clearly demarcated. Colour of large individuals uniformly blackish green. Smaller specimens violet green with paler extremities, last abdominal segments (abd. 4–6) and lateral and posterior part of head often paler than rest of body. Ocelli 8+8, G and H very small ( Fig. 18 ). PAO oval, about the size of nearest ocellus, with three associated setae. Ant. 1 on ventral side with up to 6 short blunt apical sensilla and several (up to 10) thin long setaceous sensilla, near base with two setaceous microsensilla. In addition males with 3–4 short erect sensilla on the inner ventrolateral side ( Fig. 15 ). Ant. 2–3 also with groups of short blunt ventroapical sensilla in addition to short setaceous sensilla which are dispersed over the surface ( Fig. 16 ). Ant. 4 with numerous setaceous sensilla, simple pin-seta and a small rod-shaped subapical organite. Labrum with 4/554 normal setae, four sharp apical folds and composite ventroapical ciliation. Frontoclypeal area with 12–15 setae. Maxillary palps bifurcate with 4 sublobal setae. Labial palps complete, guard e7 present. Proximal setae 5. Hypostomal group normal, H stiff and straight. Basal fields of labium with 5 lateral and 5 median setae. Head with 3–4 postlabial setae on each side of the ventral line. Mandibles normal, strong. Maxillae with short densely denticulate lamellae, none of them extending beyond tip of capitulum. Integument smooth, cover of body setae uniform and moderately long, macrochaetae in anterior part of abdomen not longer than ordinary setae, only recognised by their erect posture. Median macrochaeta on abd. 5 about 1.5 as long as inner length of last claw. Macrochaetae on abd. 5–6 smooth or indistinctly serrated. Setaceous sensilla on the tergites distributed as 88/58785, with some variation ( Fig. 13 ). Spine-like microsensilla as 11/111, those on thorax are set outside the setaceous sensilla. Sensilla along the posterior edge of tergites set in front of the p-row. Abd. 4–5 with some anterior sensilla. Ventral tube with 1–5 frontal setae on each side (very variable), lateral setae always 3+3, posterior setae up to 12. Retinaculum with 4+4 teeth and up to 12 setae in large specimens. Manubrium with 3–4 short ventroapical setae on each side, midventral field rather narrow, with 20–25 setae, manubrial teeth blunt. Dens with more than 30 dorsal setae in large specimens, only apical 1/3 free of dorsal setae. Mucro short and compact, apparently with 3 teeth; a fourth apical tooth reduced to a small hook on the ventral edge; subapical tooth with inner lamella ending before tip; inner basal tooth in line with subapical; lateral seta absent ( Fig. 17 ). Tibiotarsi with 9 apical setae (A1–7, T1, T4, Fig. 14 ), seta A1 slightly prolonged, pointed; in small juveniles T 4 may be absent. Inner side of tib.1–2 with more than 3+3 setae along median line. Upper subcoxa on first leg with two setae. Claws normal, unguis with small lateral teeth, no inner tooth; unguiculus sometimes with a small corner tooth. Males present, reproductive specimens not observed.

Discussion. The tridentate mucro and the reduced number of apical setae on tibiotarsi (9, not 11) links this species with the pjasini -group ( Potapov 2001), unlike all other Desoria of the Rocky Mountains. The mucronal shape and the presence of only 3+3 lateral setae on the ventral tube is similar to species of Isotomurus of the palustris group, but trichobothria are not present.

The recent samples were compared with a slide with 3 paratypes and the holotype (MCZ) from Terra Alta, West Virginia, and judged to belong to the same species. The type specimens have the same shape of mucro, 8–9 tibiotarsal apical setae, bifurcate maxillary palp and 3+3 laterodistal setae on the ventral tube. Type specimens have slightly longer body setae (M1 on Abd. 5 is 2.0 times as long as inner length of last claw) and their colour may differ as dark pigment is mainly present in dorsomedian part of the anterior body segments. However, at present there seem to be no sharp characters distinguishing the Rocky Mountain samples from the type specimens. Fjellberg (1984) reported D. uniens from the Colorado Front Range Mountains. These specimens were re-examined and found to be conspecific with the more recent samples.

Distribution and ecology. Common and often abundant on and near snow and ice fields in the Rocky Mountains of British Columbia, Washington, Oregon and Colorado (details above). In the original description of the species Christiansen & Bellinger (1980) also included records from California, Montana and New Mexico.

Figures

FIGURES 1 – 29. (1 – 12) Myopia alaskana, (13 – 18) Desoria uniens, (19 – 29) Desoria albicornis. (1) sensillary chaetotaxy, ms: spine-like microsensillum, (2) anterior part of head, lateral (ocelli marked A – F), (3) eye-field, right side, (4) sensilla on right ant. 1, ventrolateral, (5) sensilla on right ant. 2, lateral, (6) sensilla on right ant. 3, lateral, (7) left dens, lateral (only dorsal setae shown), (8) left mucro, dorsal, (9) ditto, lateral, (10) claw, dorsal, (11) claw, lateral, (12) manubrium, ventral, (13) sensillary chaetotaxy, (14) apical setae of left tib. 2, (15) sensilla on left ant. 1, ventral, (16) sensilla on right ant. 3, dorsal, (17) left mucro, (18) left eye-field with PAO, (19) sensillary chaetotaxy, (20) apex of tibiotarsus with unguiculus enlarged, (21) claw on last leg, lateral, (22) sensilla on right ant. 1 – 2, ventral, (23) Sensilla on left ant. 3, dorsal, (24) eye-field and PAO, right side, (25) right mucro seen from inner side, inner tooth marked, (26) right mucro and apical part of dens, (27) ventral side of manubrium, (28) labrum and frontoclypeal field, (29) apical edge of labrum.

FIGURE 115. A – H, habitus of (A) Myopia alaskana from Juneau, Alaska (a) and Bow Glacier, Washington (b). Note the difference in colour of the antennae; (B) Desoria uniens from Comox Glacier, Vancouver Island; (C) Desoria albicornis sp. n. from Juneau, Alaska; (D) Desoria ater sp. n. from Juneau, Alaska; (E) Desoria triangularis sp. n. from Triangle Peak, Alaska. Note the triangular white spots between the eyes; (F) Desoria garibaldii sp. n. from Easton Glacier, Washington; (G) Gnathisotoma spinolabris sp. n. paratype from Juneau, Alaska, in dorsal (a) and lateral (b) views. Note the crown-shaped white figure between the eyes; (H) Desoria cryophila sp. n. holotype from Kananaskis, Alberta.