Desoria triangularis Fjellberg, 2010, sp. n.
Creators: name: Fjellberg, Arne
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Entognatha
Collembola
Isotomidae
Desoria
Desoria triangularis

description: Desoria triangularis sp. n.
(Figs. 30–34, 110, 115E)
Type material. Holotype (alc.) from "Alaska. Richardson Hwy., N of Paxson. Triangle Peak, 63o24'N, 145o31'W, 09.VIII.1980. Wet moss near snow, 1,600 m alt. A. Fjellberg 144/80." Paratypes, two specimens (slide), male and female, from the same sample (INHS).
Description. Body size up to 1.2 mm. Body shape cylindrical, rather stout (Fig. 115E). Head shape normal. Abd. 5–6 fused without clear break in setal cover. Colour bluish or greenish black, legs and furca bluish grey. Antennae white, except the first segment which is bluish grey. Occipital area of head with two large triangular white spots (Fig. 110); in addition head and body with diffuse blue-grey marks in the spots that usually mark muscular incisions. Ocelli 6+6 (A–F), a small G-ocellus may also be present. PAO elongated, as long as diameter of nearest ocellus. Two setae associated with PAO (Fig. 31). Ant. 1 with two short ventroapical sensilla and about 8 longer setaceous sensilla. Ant. 2 with one curved enlarged sensillum in ventroapical position. Ant. 3 organ with 4 dorsal sensilla and 3 (one small) lateral ones. No additional sensilla (Fig. 34). Ant. 4 with simple subapical pin seta, subapical organite as an apically expanded rod set in a pit. Labral chaetotaxy 4/554, setae normal, not spine-like. Apical edge of labrum with 4 sharp folds and a composite ventroapical ciliation. Central frontoclypeal field with 6–8 setae, two setae above posterior corner of labrum. Maxillary palp bifurcate, 4 sublobal setae. Labial palps unmodified, with terminal setae of the papillae as long as the inner guard setae; guard e7 present. Hypostomal setae normal. H long and straight, sub equal to h1 and h2. Basal fields of labrum with 4 median and 5 lateral setae. Head with 4+4 postlabial setae along ventral line. Mandibles normal, strong. Maxillae unmodified, with strong 3-toothed capitulum and 6 finely denticulate lamellae of which Lam.1 reaches tip of capitulum. Body integument smooth, without visible granulation. Setal cover of body very dense, "double", with short and long setae (Fig. 30). Macrochaetae clearly differentiated on abdomen, but not long. Median macrochaetae on abd. 5 about 1.7 as long as inner length of last claw. Sensilla on the tergites hard to distinguish from ordinary short setae and formula unclear, but numbers appear to be low, probably 4–5 on anterior abdominal segments. Formula of spine-like microsensilla appears like 10/001 but must be verified. Ventral tube with 1+1 frontal, 4+4 lateral and 4 caudal setae (only two specimens examined). Retinaculum with 4+4 teeth and 4–5 setae. Manubrium with blunt apical teeth, 1+1(2) short ventroapical setae. Central field of ventral side densely piles (more than 50 setae). Dens with 8–9 dorsal setae in proximal half; ventroapical seta not prolonged. Mucro short and compact, with 5 sharp teeth; inner lateral lamella transformed to a secondary tooth; lateral seta absent (Fig. 32). Tibiotarsi with 11 apical setae (A1–7, T1–4), all acuminate. Legs shortened, inner side of tib.1–2 with 3+3 setae along median line (as Fig. 72). Claws small, inner and lateral teeth absent on unguis (Fig. 33). Males present.
Etymology. The name refers to both the type locality (Triangle Peak) and the triangular white spots on the head.
Discussion. The outstanding character of this species is the strikingly "double" cover of seta on the body which separates it from all other cryophilic Desoria / Gnathisotoma which are dark with white antennae. From albicornis it differs by having two triangular pale spots on head, rather than four small spots. Also abd. 5-6 are completely fused while they are weakly separated in albicornis. The absence of the spine-like microsensillum on th. 3 in triangularis may also be a distinctive character, but a verification is necessary.
Distribution and ecology. So far only known from the type locality in the alpine region of the mountains of southern Alaska.
description: Published as part of Fjellberg, Arne, 2010, Cryophilic Isotomidae (Collembola) of the Northwestern Rocky Mountains, U. S. A., pp. 27-49 in Zootaxa 2513 on pages 33-34, DOI: 10.5281/zenodo.196078