Folsomia sensivillosa, Potapov, Mikhail & Gulgenova, Ayuna, 2013

Potapov, Mikhail & Gulgenova, Ayuna, 2013, Isotomidae (Collembola) of Buryat Republic. II. A revision of the genus Folsomia, Zootaxa 3682 (2), pp. 305-330 : 317-318

Folsomia sensivillosa sp. nov.

Figs 18–23

Type material. Holotype: Subadult female. Russia (East Siberia), Irkutskaya Oblast', Khamar-Daban Range, vicinities of Slyudyanka, ca. 500 m alt., litter of herbaceous birch forest ( Rosa , Vaccinium vitis-idea, Rhododendron ), 29.viii.2008, leg. M. Potapov and V. Kadnikov. 8 paratypes, subadult females and males, from the same locality. Holotype and 4 paratypes in MSPU; 4 paratypes in BSU.

Other material. Several specimens from W Buryatia, Tunkinsky District, Tunkinskiye Gol'tsy Range, Khulugaisha Mt., 1563 m alt., herbaceous birch forest, 27.vii.2009. leg. A. Gulgenova. Mongolia, Arkhangai Aymag, ca. 40 km E Tsetserleg, Tavshrulekh Farm, leg. A.Druk.

Description. Body size about 1 mm. Lacking pigment on body. Body of typical habitus for the genus ( Fig. 20 ). Body cuticle smooth, with weak hexagonal/orthogonal primary granulation. Ocelli lacking. PAO narrow and long, constricted, 1.3–1.6 as long as width of Ant I and 1.6–1.8 as long as inner unguis length. Maxillary outer lobe with 4 sublobal hairs, maxillary palp bifurcate. Labral formula as 4/5,5,4. Chaetae of subapical and middle rows thicker, labral edge well developed. Labium with 5 papillae, full set of guard chaetae, 3 proximal, 4 basomedian, and 5 basolateral chaetae. Ventral side of a head with 4+4 chaetae. Ant.I with 2 small basal microsensilla (bms), dorsal and ventral, and 2 ventral sensilla (s), Ant.II with 3 bms and 1 latero-distal s, Ant.III with 1 bms and 6 distal s (including 2 lateral), without additional sensilla. Sensilla on Ant.4 weakly differentiated. Organite stick-like, slightly swollen at tip.

Sensillary formula as 4,3/2,2,2,3,5 (s), 1,1/1,1,1 (ms). Tergal sensilla thin, shorter than common chaetae ( Fig. 20 ). Medial sensilla on all tergites situated in mid-tergal position, on Abd.I–III between Mac1 and Mac2, on Th.II in front position. Abd.V with 5 sensilla arranged with 4 dorsal ones (al, accp1, accp2, accp3) longer than sensilla on Abd.IV and lateral sensilla on Abd.V ( Fig. 22 ). Microsensilla (ms) of Abd.III large, subequal to ms on Th.II ( Fig. 21 ), ms of Th.III, Abd.I, and Abd.II small. Macrochaetae smooth and long, 1,1/3,3,3 in number, medial ones on Abd.V longer than dens (as 1:0.8–0.9) and 4.3–5.2 times longer than mucro. Without foil chaetae. Axial chaetotaxy as 8–9,7–8/4–5,4,3. Thorax without ventral chaetae.

Unguis of normal shape, without lateral and inner teeth. Empodial appendage 0.45–0.50 as long as unguis. Tibiotarsi with many additional chaetae, up to 36 on Leg III. Tibiotarsal tenent chaetae pointed. VT with 3+3 laterodistal and 7–8 posterior chaetae, anteriorly without chaetae. Tenaculum with 4+4 teeth and 1 chaeta. Anterior furcal subcoxae with 6(5–7), posterior one with 4 chaetae. Anterior side of manubrium with 10–14 chaetae usually arranged as 2+2,2+2,2+2,1 ( Figs 18–19 ). Posterior side of manubrium with 4+4 laterobasal, 1 apical chaeta (ap), 2+2 chaetae in distal transversal row (M1, L1), one pair of lateral chaetae, and 3–4+ 3–4 in central part. Dens with 10–11 anterior chaetae. Posterior side of dens crenulated and with 3 normal chaetae (2 basal and 1 at the middle). Mucro bidentate. Ratio of manubrium:dens:mucro = 4.4–4.8:3.9–4,1:1.

Discussion. The species belongs to the ‘ quadrioculata’ group. It resembles F. b ai c al ic a Stebaeva & Potapov, 1997 and F. villosa Potapov & Marusik, 2000 described from vicinities of Baikal and Kuril Islands respectively. The three species share the absence of ocelli, mid-tergal position of sensilla, more than 8 anterior chaetae on dens, many chaetae on anterior side of manubrium, and long macrochaetae. F. sensivillosa sp. nov. differs by a complete set of ms (1,1/1,1,1 vs. 1,0/1,0,0 in other two species). Besides, it has more chaetae on the anterior side of dens (10–11 vs. 9) and longer accp3 sensilla on Abd.V which is subequal to accp2 (sensilla accp3 much shorter than accp 2 in F. b a i c a l i c a and F. villosa ). The chaetotaxy of the anterior side of manubrium and dens of F. sensivillosa sp. nov. also resembles F. setosa Gisin distributed in European mountains. The latter has 5 ocelli and more chaetae on posterior side of dens.

Distribution and ecology. Known from adjacent mountains in S Siberia and Mongolia. The distribution of F.

sensivillosa sp. nov., F. villosa , and F. baicalica is probably allopatric ( Fig. 23 ). Four other undescribed species belonging to this group have been also found in our material from China and the Asiatic part of Russia which are partly sympatric with F. villosa ( Fig. 1 : loc. 9, 10).

Etymology. Due to a complete set of microsensilla the species is presumably more "sensitive" than F. villosa .

Figures

FIGURE 1. The sampling sites in Buryatia: 1 – 2 — Vitim Plateau (1 — Konda Basin, 2 — Eravna Basin), 3 – 5 — Selenga Low Plateau (3 — Zagansky Range, 4 — vicinities of Schuch'ye Lake, 5 — vicinities of Karasinoye Lake), 6 – 8 — Barguzinsky Range (6 — Ust' - Barguzin, 7 — vicinities of Barguzin, 8 — upper flow of Barguzin River), 9 — Khamar-Daban Range, 10 — Tunkinskiye Gol'tsy Range, 11 — vicinities of Ulan-Ude, 12 — estuary of Selenga River, 13 — vicinities of Khorinsk, 14 — vicinities of Unnokent'evka, 15 –– Turka.

FIGURES 16 – 19. F. maximovi sp. nov. (16, 17) and F. sensivillosa sp. nov. (18, 19): 16, sensilla and macrochaetae of Abd. IV – VI; 17, 18, furca, lateral view (on manubrium chaetae of only one side shown); 19, furca, anterior view.

FIGURES 20 – 23. F. sensivillosa sp. nov.: 20, habitus and chaetotaxy; 21, lateral part of Abd. III; 22, chaetotaxy of Abd. IV – VI; 23, records, two closely related species also shown.