Scutisotoma montana, Potapov & Babenko & Fjellberg, 2006

Potapov, Mikhail, Babenko, Anatoly & Fjellberg, Arne, 2006, Taxonomy of the Proisotoma complex. Redefinition of genera and description of new species of Scutisotoma and Weberacantha (Collembola, Isotomidae), Zootaxa 1382 (1), pp. 1-74 : 45-47

Scutisotoma montana sp.n.

Fig. 119–126

Type material. Holotype: ♀, Canada, Sparwood, B.C., Bald Mt. , moss/ Dryas meadow, 07.vi.1983, leg. A. Fjellberg. Paratypes: 26 exx., same sample. Deposited in ONC (holotype and 16 paratypes) and MSPU (10 paratypes) .

Other material. Many specimens from several localities in Alberta, Canada (Kananaskis Valley, Plateau Mt.), mostly in the alpine zone above 2000 m alt., leg. A. Fjellberg.

Description. Size 0.8–1.1 mm. Colour rather dark yellow-brown with numerous paler spots, ventral side and extremities paler. Cuticle with fine but visible primary granulation. Ocelli 8+8, subequal. PAO elliptical, long with indistinct constriction ( Fig. 124 ), 1.2–1.6 as long as U 3. Maxillary outer lobe with 4 sublobal hairs and bifurcate maxillary palp. Labral formula 4/554. Labium with a full set of papillae and guards. Proximal field with 3 chaetae, basomedian field with 4. Ventral side of a head with 3+3 postlabial chaetae. Ant.1 with 2 basal microsensilla (bms, dorsal and ventral) and 2 ventral sensilla (s). Ant.2 with 3 bms and 1 latero-distal s, Ant.3 with 1 bms and 5 distal s (AO + one lateral s). Guards of AO thinner and slightly longer than inner pair of sensilla. Additional sensilla on Ant.2–3 present in males. Sensilla on Ant.4 hardly differentiated, subapical organite small.

All abdominal tergites clearly separated. Dorsal axial chaetom of Th.II–Abd.III as 7–8,5–6/555. Thorax without ventral axial chaetae. Macrochaetae clearly differentiated laterally on Th.II–III, on Abd.I–III and on tip of abdomen. Medial macrochaetae on Abd.V are 0.4–0.5 times as long as tergite. Sensilla on tergites clearly shorter and more slender than ordinary chaetae. Sensillary formula 33/22224 (s) and 11/111 (ms). On Th.II–III one sensillum of the lateral group set long behind the lateral macrochaeta ( Fig. 126 ). Sensilla on Abd.I–III in mid-tergal position, including medial sensillum on Abd.III. The position of sensilla on Abd.V somewhat variable. The specimen shown in Fig. 125 has the second medial sensilla (accp2) in anterior position, in other specimens all sensilla are set almost in a line.

Unguis usually with a small inner tooth, rarely without tooth. Ti.1–3 with the basic set of chaetae (21-21-25). B-row on Ti.1–2 with 7 chaetae. Chaetae x and B 5 on Ti.3 sticklike, rather long and truncate at tip. Tibiotarsal tenent chaetae (1-2-2) clavate and about as long as unguis (U 3: t.ch. = 0.8–1.1: 1). Ventral tube with 4+4 laterodistal and 4–6 posterior chaetae. Tenaculum with 4+4 teeth and one chaeta ( Fig. 120 ). Anterior furcal subcoxa with 7–11, posterior usually with 6 chaetae. Furca long and slender, almost reaching anterior margin of Abd.III. Anterior side of manubrium without chaetae, posterior side usually with 10+10 chaetae on main part and 3+3 chaetae on lateral lobes ( Fig. 119 ). Dens with 3(4) posterior chaetae and one subapical on anterior side ( Figs. 121–123 ). Mucro elongated with two subequal teeth. Ratio of manubrium: dens: mucro = 5.7–6.8: 3.3–3.6:1.

Affinity. Among the Asiatic species of the genus our new species is most similar to stepposa (Martynova) and baica sp.n. However, the two latter species both have all lateral sensilla on Th.II set in front of the lateral macrochaeta, forming a single group. Also they have a different mucro/dens ratio and more posterior setae on manubrium and dens. S. montana sp.n. also relates to the American species Folsomides teres Christiansen & Bellinger which has an unclear generic position. Although the original description of F. teres indicate several differences to S. montana , the general similarity of the two species calls for additional studies. F.teres might well be a Scutisotoma .

Many species of the genus Subisotoma Stach share essential furcal characters with our montana , but other principal characteristics are different and led us to assign montana to Scutisotoma and not to Subisotoma (see also remarks to S. baica sp.n.).

Distribution. Known from several mountainous localities of western Canada.

Name derivation. The name reflects the distribution of the new species.

Figures

FIGURES 119–126. Scutisotoma montana sp.n. 119, furca and genital field, posterior; 120, tenaculum; 121, dens, anterior; 122–123, dens, lateral (different specimens); 124, PAO and ocelli; 125, chaetotaxy of Abd.V (s1–4: accp1–4 sensilla); 126, chaetotaxy of lateral part of Th.II (sensilla encircled, s: sensillum, ms: microsensillum).