Folsomia uniramia, 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 : 323-325

Folsomia uniramia sp. nov.

Figs 32 , 34–38

Type material. Holotype: Adult female. Russia (East Siberia), Buryat Republic, Ust'-Barguzin, shore of Baikal Lake, pine wood on dunes, flotation of sand on beach (5 m from water edge), 21.viii.2008, 5 paratypes from the same locality, leg. A. Gulgenova & M. Potapov. Holotype and 3 paratypes in MSPU; 2 paratypes in BSU.

Other material. Shore of Baikal Lake, ca. 30 km S estuary of Selenga River, Posol'sky Sor Bay, near Baikal'sky Priboy station, lake debris near the water, 23.viii.2011. leg. A. Gulgenova and L. Vanyavina.

Description. Body size 0.4–0.5 mm. Without pigmentation, ocelli absent. Cuticle with thin hexagonal primary granulation ("smooth"). PAO broadly elliptical, not constricted, about as long as width of Ant I (0,8–1,1) and 1,4– 1,6 as long as inner unguis length ( Fig. 37 ). Maxillary outer lobe with 4 sublobal hairs, maxillary palp simple. Labral formula as 3/5,5,4. Labral edge reduced and distal row of labral chaetae placed in apical position ( Fig. 37 ). Labium with 5 papillae (А–Е), guard chaetae e7 present, 3 proximal and 4 basomedian chaetae. Ventral side of a head with 4(3)+4(3) 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, Ant.II with 3 bms and 1 latero-distal s, Ant.III without bms and with 5 distal s (including one lateral), without additional sensilla. Sensilla on Ant.4 weakly differentiated. Organite small.

Sensillary formula as 3,3/2,2,2,3,5 (s), 1,0/0,0,0 (ms) ( Fig. 32 ). Corner sensilla on Th.II absent. Tergal sensilla as long as or longer than common chaetae and hardly distinguishable ( Fig. 34 ). 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 thickened and pointed sensilla ( Figs 34, 35 ). Shape of lateral sensilla varies ( Fig. 36 ). Macrochaetae smooth and short, 1,1/3,3,3 in number, medial ones on Abd.V 1.6–2.0 times shorter than dens and 3.7–4.6 times longer than mucro ( Fig. 36 ). 7 foil chaetae at the tip of abdomen (fa1, fa2, fp0, and fp2). Axial chaetotaxy as 7–8,4/3,3,3 (only one specimen was studied). Thorax without ventral chaetae.

Unguis of normal shape, without lateral and inner teeth. Empodial appendage about half as long as unguis (0.5–0.6). Tibiotarsi without additional chaetae on Leg I and II (21 chaetae), and with some ones on Leg III (up to 27 in all). Tibiotarsal tenent chaetae pointed. VT with 4+4 laterodistal and 5 posterior chaetae, anteriorly without chaetae. Tenaculum with 4+4 teeth and a chaeta. Anterior furcal subcoxae with 6, posterior one with 4–5 chaetae. Anterior side of manubrium with 2+2 chaetae ( Fig. 34 ). Posterior side of manubrium with 8+8 chaetae on main part: 2 apical chaetae (ap), 2+2 chaetae in distal transversal row (M1 and L1), and 5+ 5 in central part ( Fig. 38 ). 4+4 laterobasal chaetae, a pair of laterocentral chaetae present or absent (see the discussion part). Dens with 16–18 anterior chaetae ( Fig. 34 ). Posterior side of dens crenulated and with 4 chaetae (2 basal and 2 at the middle), without minute chaeta at the base of mucro. Mucro short, bidentate. Ratio of manubrium:dens:mucro = 5.6–6.8: 7.5–7.9: 1.

Discussion. The species belongs to ' heterocellata ' group. It is a rather peculiar member of the genus due to reduced edge of labrum, absence of corner sensilla on Th.II and microsensilla on Abd.I. In the characters of the furca, F. uniramia sp. nov. takes an intermedate position between F. kurushica Potapov, Abdurakhmanov & Aitekova, 2001 and F. vitimica sp. nov. One specimen from Eastern Buryatia (Eravna Basin, pine wood) differ from the type population by the presence of microsensilla on Abd.I and a lateral pair of chaeta on manubrium and probably belongs to another undescribed species. Two specimens from an estuary of the Selenga River also have lateral chaetae on the manubrium, which are treated as a variation within F. uniramia sp. nov. by us.

Distribution and ecology. Two distant records from the sandy shore of Baikal Lake ( Fig. 1 : loc.: 6, 12).

Etymology. The species has a simple maxillary palp with only one branch.

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 31 – 32. Habitus and chaetotaxy of F. uniparis sp. nov. (31) and F. uniramia sp. nov., adult male (32).

FIGURES 33 – 38. F. uniparis sp. nov. (33) and F. uniramia sp. nov. (34 – 38): 33, Furca of adult male; 34, posterior part of abdomen; 35, Abd. IV – VI, dorsal view; 36, variation of lateral sensilla on Abd. V; 37, anterior part of the head; 38, posterior side of manubrium.