Desoria albicornis, Fjellberg, Arne, 2010

Fjellberg, Arne, 2010, Cryophilic Isotomidae (Collembola) of the Northwestern Rocky Mountains, U. S. A., Zootaxa 2513, pp. 27-49 : 32-33

Desoria albicornis sp. n.

( Figs. 19–29 , 111 , 115C )

Type material (all in alcohol, sex not checked). Holotype and 55 paratypes from: "Alaska, mountains between Mendenhall Glacier and Montana Creek Trail, 58 o 29 'N, 134 o 40 'W, on melt-water ponds, 975 m. alt., 13.VII. 1980, A. Fjellberg leg." ( INHS).

Description. Body size up to 1.3 mm. Body shape cylindrical, slender, with relatively short legs ( Fig. 115 C ). Head shape normal. Abd. 5–6 weakly separated, with a clear break in setal cover. Colour uniformly violet black, antennae pure white apart from dark proximal half on ant. 1. Head with a transverse row of four small white spots ( Fig. 111 ). Tibiotarsi paler than rest of the legs. Each side of head with 6 large ocelli and two very small ones. PAO oval, as long as diameter of nearest ocellus, with three associated setae ( Fig. 24 ). Ant. 1 on ventral side with up to 10 long slender sensilla and 2–3 short ones in apical position. Ant. 2 with an enlarged sensillum in lateral position ( Fig. 22 ). Ant. 3 organ normal, with 4 dorsoapical sensilla and 3 ventrolateral ( Fig. 23 ). Ant. 4 with bifurcate subapical pin seta and a short rod-shaped subapical organite in a pit. Labrum with 4 / 554 slender setae, apical edge with 4 low ridges and a composite ventroapical ciliation ( Fig. 29 ). Central part of frontoclypeal field with 4 (rarely 5) setae ( Fig. 28 ). Maxillary outer lobe with bifurcate palp and 4 sublobal setae. Labial palp with apical papillae A–E present, 4 proximal setae; guard e 7 present at base of papilla E; terminal seta of the papillae shorter than the guards. Lateral process (l.p.) on papilla E strong, finger-like. Hypostomal papilla with H shorter than h 1 /h 2. Basal fields of labium with 4 median and 5 lateral setae. Head with 4 + 4 postlabial setae along ventral line. Mandibles normal, with moderately strong teeth. Maxillae with 3 -toothed capitulum and 6 lamellae covered with fine denticles only. Lamellae short, not projecting beyond tip of capitulum. Integument smooth, without visible granulation. The cover of body setae short, dense and uniform. Macrochaetae smooth, acuminate, weakly differentiated from ordinary setae. Median macrochaeta on abd. 5 about half as long as tergite in midline. Tergites with 44 / 3345 ordinary sensilla n the p-row on abdomen (one anterior s on abd. 5) and slightly in front of the p-row on th. 2–3. Spine-like microsensilla as 11 /001 ( Fig. 19 ). Ventral tube with 1 + 1 frontal setae, usually 5 + 5 (4–6) lateral and 3–5 caudal setae. Retinaculum with 4 + 4 teeth and 2–4 setae. No ventral setae on thorax. Manubrium with a variable number of ventral setae, fewer than 15 ( Fig. 27 ); ventroapical thickening with blunt teeth; 1 + 1 short ventroapical setae. Dens with 7 dorsal setae in the proximal 1 / 3 and a subapical microseta; ventroapical seta not prolonged. Mucro short and curved, with 5 sharp teeth; a tooth on the inner side derived from the inner lateral lamella ( Figs. 25–26 ); no lateral seta. Tibiotarsi with 11 acuminate apical setae (A 1–7, T 1–4, Fig. 20 ). Legs shortened, in particular tib. 1–2 with only 3 + 3 setae along median line (as Fig. 72 ). Claws narrow, slightly constricted at base, without visible inner and lateral teeth; unguiculus with wide lamellae ( Figs. 21– 22 ). Reproductive males without differentiated setal cover.

Etymology. The name reflects the strikingly white antennae of the species.

Discussion. The only described North American Desoria having a 5 -toothed mucro is cancellarei Christiansen et Bellinger, 1980 , described from California and Iowa (on snow). This species is said to have 6 + 6 ocelli, otherwise it comes very close to albicornis , having few setae on ventral tube and retinaculum as well as untoothed claws of similar shape. However, cancellarei has much longer abdominal macrochaetae, 2– 3 times as long as inner edge of the claw (1.5 as long in albicornis ). D. albicornis resembles Myopia alaskana in colour, except only basal part of ant. 1 is dark, the rest is white.

Distribution and ecology. So far only recorded from snow and melt water ponds in Alaska (types) and British Columbia (Vancouver Island: Comox Glacier, 49 o 33 'N, 125 o 21 'W, 26.VIII. 1983, A. Fjellberg leg.).

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.

FIGURES 110 – 114. black / white patterns on head and antennae in (110) Desoria triangularis sp. n., (111) Desoria albicornis sp. n., (112) Myopia alaskana from Juneau, Alaska, with antenna of a specimen from Haigh Glacier, Alberta (above), (113) Desoria ater sp. n., (114) Gnathisotoma spinolabris sp. n.

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.

FIGURES 57 – 77. (57 – 63) Desoria cryophila sp. n., (64 – 70) Desoria rosea sp. nov., (71 – 76) Desoria olympica sp. n., (77) Desoria capra sp. n., (57) sensillary chaetotaxy, positions of macrochaetae indicated, (58) eye-field and PAO, (59) left mucro, (60) sensilla on ventral side of right ant. 1, (61) ditto, right ant. 3, dorsal, (62) ditto, right ant. 2, lateral, (63) setae along midline on inner side of tib. 1, (64) eye-field and PAO, (65) sensilla on right ant. 2, lateral. es: erect sensilla, (66) ditto, ant. 3, (67) setae in right basomedian field of labium, the additional 5 th. seta encircled, (68) right mucro, lateral, (69) ditto, dorsal, with the secondary inner tooth formed by the truncated inner lamella marked, (70) dorsal setae in basal half of dens, (71) sensillary chaetotaxy, positions of macrochaetae indicated, (72) setae along midline on inner side of tib. 1, (73) left mucro and apical part of dens, (74) ventral side of manubrium, (75) eye-field and PAO, (76) labrum and frontoclypeal field, (77) right maxilla with details of capitular teeth (mt: membranous tooth).