Folsomia vitimica Potapov & Gulgenova, 2013, sp. nov.

Folsomia vitimica sp. nov.

Figs 39–43

Type material. Holotype: female. Russia (East Siberia), Buryat Republic, Vitim Highland, Konda Basin, near Birkhasan river (ca 14 km N Telemba), larch wood (Larix gmelini) with grass, ca. 1000 m alt., 4.x.2009, leg. A. Gulgenova. 3 paratypes from the same locality (dated as 30.v.2009 and 23.viii.2009) and 10 paratypes from Eravna Basin of the same highland, ca. 3 km SW Sosnovo-Ozyorskoye, ca. 1050 m alt., larch wood on elevation with Rhododendron, 20.viii.2009, leg. A. Gulgenova. Holotype and 7 paratypes in MSPU; 6 paratypes in BSU.

Other material. Several specimens from from Konda Basin of Vitim Highland, near Birkhasan river (ca 14 km N Telemba), ca. 1050 m alt., larch wood on elevation with Rhododendron, 23.viii.2009, and larch wood with Betula nana, ca. 14 km N Telemba, ca. 960 m alt., 9.vii.2009, leg. A. Gulgenova.

Description. Body size about 0,4 mm. Body without pigmentation, slender (Fig. 39). Cuticle with weak hexagonal primary granulation ("smooth"). Ocelli lacking. PAO narrowly elliptical, not constricted, 1.1–1.2 as long as width of Ant I and 1.6–1.9 as long as inner unguis length (Fig. 42). Maxillary outer lobe with 4 sublobal hairs, maxillary palp simple. Labral formula as 3/5,5,4. Labium with 5 usual papillae (А–Е), guard chaetae e7 absent, 3 proximal and 4 basomedian chaetae. Ventral side of a head with 4+4 chaetae. Ant.I with 2 ventral sensilla (s) and 2 small basal microsensilla (bms), dorsal and ventral, the former set together with long chaeta-form microsensillum (Fig. 42), Ant.II with 3 bms and 1 latero-distal s, Ant.III without bms and with 5 distal s (including 1 lateral), without additional sensilla. Sensilla on Ant.4 weakly differentiated. Organite small.

Sensillary formula as 4,3/2,2,2,3,5 (s), 1,0/1,0,0 (ms). Tergal sensilla as long as common chaetae and hardly distinguishable. Medial sensilla on Th.II–Abd.III situated in mid-tergal position, on Abd.I–III between Mac1 and Mac2. Abd.V with 5 sensilla arranged with 3 dorsal ones (al, accp1, accp2) being long and slender and 2 lateral middle-sized sensilla clearly thicker than other sensilla (Fig. 40). Macrochaetae smooth and short, 1,1/3,3,3 in number, medial ones on Abd.V 1,1–1,6 times shorter than dens and 2.1–2.9 times longer than mucro (Fig. 40). 7 foil chaetae at the tip of abdomen arranged in two transversal rows as 2+2 anterior (fa1 and fa2) and 1+2 posterior (fp0 and fp2), respectively. Axial chaetotaxy as 7–8,5/3,3–4,4. Thorax without ventral chaetae.

Unguis of normal shape, without lateral and inner teeth. Empodial appendage about half as long as unguis. Tibiotarsi without additional chaetae on Leg I and II (21 chaetae), and with few ones on Leg III (25 as the most common set). Tibiotarsal tenent chaetae pointed. VT with 4+4 laterodistal and 5 posterior chaetae, anteriorly without chaetae. Tenaculum with 4+4 teeth and 1 chaeta. Anterior furcal subcoxae with 5, posterior one with 3 chaetae. Anterior side of manubrium with 2+2 chaetae (Figs 40, 41). Posterior side of manubrium with 4+4 laterobasal, 2 apical chaetae (ap), 2+2 chaetae in distal transversal row (M1, L1), one pair of lateral chaetae, and 2+ 2 in central part (Fig. 43). Dens with 9 (8) anterior chaetae arranged as 1,2,1,2,3 (Fig. 41). In middle position one chaeta sometimes absent (chaetae arranged as 1,2,0,2,3 or 1,1,1,2,3). Posterior side of dens crenulated at the middle and with 4 normal chaetae (2 basal and 2 at the middle) and often one rudimentary minute chaeta at the base of mucro. Mucro bidentate. Ratio of manubrium:dens:mucro = 3.7–4.7:3.1–3.7:1.

Discussion. The species formally belongs to ‘ heterocellata’ group (Potapov 2001) because of the simple maxillary palp. The most remarkable character of F. vitimica sp. nov. is the sensilla of the lateral duplet of Abd.V which are subequal and thick. These sensilla form the "3+2" pattern, that is 3 long and slender dorsal and 2 middlesized and thick lateral sensilla (for more details of the terminology see Potapov & Greenslade, 2010). All other Holarctic species with "3+2" pattern (species of ' sensibilis ' group and part of species of ' heterocellata ' group) have many more chaetae on the anterior side of the dens. F. k u r u s h i c a described from East Caucasus is most similar to F. vitimica sp. nov.: they share simple maxillary palp, "3+2" pattern, mid-tergal position of sensilla on body, 3 prelabral chaetae and some other characters. F. kurushica shows more developed furca with 3–4+ 4–4 and 20–25 anterior chaetae on manubrium and dens, respectively. Chaetotaxy of the proximal part of the anterior side of the dens is another distinct character of the new species: two chaetae set together in transversal row ("1, 2,...") (Fig. 41) (shared only with F. biparis sp. nov.) that is unknown in species having such a short furca: they have formula "1, 1,...".

Distribution and ecology. Known from forest sites in two basins of E Buryatia (Fig. 1: loc.: 1, 2).

Etymology. The name of the new species refers to the type locality that belongs to the studied region Vitim Highland.