Sensillonychiurus vegae, Babenko, Anatoly B., Chimitova, Ayuna B. & Stebaeva, Sophya K., 2011

Babenko, Anatoly B., Chimitova, Ayuna B. & Stebaeva, Sophya K., 2011, New Palaearctic species of the tribe Thalassaphorurini Pomorski, 1998 (Collembola, Onychiuridae), ZooKeys 126, pp. 1-38 : 11-13

Sensillonychiurus vegae sp. n. Figs 915-17, 19-20, 22-23

Material.

Holotype ♂, Russia, eastern Siberia, Yakutia (Sakha Republic), mouth of Yana River, Shirokostan Peninsula, vicinity of Lake Ledyanoe [72°25'N, 141°00'E], Dryas association on steep slope, 04.viii.1994, leg. A. Babenko (MSPU).

Paratypes 6 ♀, 1 ♂, and 1 juv., Russia, eastern Siberia, Yakutia (Sakha Republic), left bank of Kolyma River [69°32'N, 160°44'E], grass ( Elymus sibiricus ) association on a polar fox hill, 19.viii.1994, leg. A. Babenko (MSPU).

Other material: 1♀ and 2♂, Russia, Siberia, northwestern Buryatia, Ust’ -Barguzin [53°25'N, 109°01'E], shore of Lake Baikal, pine forest on sandy dunes (flotation), 21.viii 2008, leg. M. Potapov; 2♀, 6♂ and 6 juv., Russia, Siberia, Buryatia, Vitim Plateau, vicinity of Eravna (Sosnovo-Ozerskoe) [52°27'N, 111°09'E], pine forest with Rhododendron dauricum , 08.ix.2008, leg. A. Chimitova; 2 ♂, same region, but birch forest, 25.viii.2009, leg. A. Chimitova (MSPU).

Description.

Colour white. Size 0.40-0.52 mm, holotype 0.47 mm long. Body slender and elongated. Antennae about as long as head, antennal area not clearly demarcated. Sensillar armature of Ant.4 as usual: two distinct thickened sensilla, a sub apical organite and a basal microsensillum set almost in line with proximal row of setae (Figs 15-17). Ant.3 organ consisting of 4 papillae, 2 sensory rods, 2 smooth sensory clubs, 3 guard setae, and a lateral microsensillum (Fig. 15). Ant.1 and 2 usually with 8 and 13(14) setae, respectively. PAO with 6-7(8) composed vesicles. Labrum with 7 setae and 2 prelabral ones (2/3-4), four setae of apical row thicker. Apical part of labium with thick terminal setae on papillae A and C (AC - type), (5)6 proximal setae and a complete set (11) of guard setae: 7 long [b3-4, d3-4, e1-3] and 4 spiniform [a1, b1-2 and d2] ones set on papillae, a1 clearly longer than others. Basal fields (mentum and submentum) with 4 and 5 setae. Maxillary palp simple, with two sublobal setae.

Pseudocellar formula (pso) as follows, dorsal: 32/133/33343, ventral: 1/000/0000, Abd.4 sterna with or without 1+1 parapseudocelli laterally (see Variability). Each upper subcoxa with one pso. Granulation fine and uniform, slightly enlarged granules rarely present around medial pso on abdominal tip and on head. Dorsal chaetotaxy almost symmetrical (Fig. 9), setae smooth and clearly differentiated, especially on last abdominal terga, in anterior parts of body meso and microsetae only slightly differing in size but different in shape: mesosetae straight and blunt, microsetae curved and pointed. Tergal sensilla (1/011/221111 in number) distinct, sternal ones (2/000/0000-1) hardly distinguished, sensillum on coxae of Lg.3 evident. Th.1 usually with 6+6 setae. Lateral microsensilla present only on Th.2. Unpaired dorsal seta d0 on head absent, Abd.4 with m0 and p0, Abd.5 with p0, Abd.6 with one axial macroseta (Figs 9, 18). Axial microsetae p1 lying almost in line with mesosetae p2 on Abd.3 (Fig. 22) and sometimes also on Abd.2. Thoracic sterna without setae along linea ventralis. Abd.3 sternum unclearly divided, anterior subsegment narrow and without setae. Furca reduced to a small area of fine granulation situated at contact with border between Abd.3-4 sterna, with 2+2 small posterior setae arranged in two rows, manubrial area usually with 4+4 setae set in two rows. Ventral tube with 6+6 distal setae, proximal ones at corpus base absent. Upper subcoxae usually with 3-4-4, tibiotarsi with 15-15-14, setae: distal rows with 7 setae (all T-setae absent), row B with 7-7-6 setae, setae M absent but Y present (Fig. 20). Unguis simple, with neither inner nor lateral tooth, unguiculus with an indistinct basal lamella, about 0.6 times as long as inner edge of U3.Anal spine rather long (0.6-0.7 U3) but thin (thickness/length 0.13-0.23) (Fig. 19), set without papillae.

Variability.

The types of Sensillonychiurus vegae sp.n. completely lack psx as well as all so far studied species of the genus. Nonetheless, at least some of the specimens collected on Vitim Plateau possess 1+1 ventral parapseudocelli on Abd.4 (Fig. 23) being otherwise identical to the types. This population may represent a separate species, but its reliable distinction is hardly possible. Anyway, more material from different points of the distributional range is needed to evaluate the constancy and significance of this character.

Affinities.

Virtually all of the main morphological characteristics of Sensillonychiurus vegae sp. n. (structure of AO and PAO, labrum and labium, dorsal and ventral chaetotaxy, number and distribution of pso, presence of ms only on Th.2, number of setae on subcoxae, tibiotarsi and VT) are identical to those of sympatric Sensillonychiurus taimyrensis sp. n. Concerning the differences of Sensillonychiurus vegae sp. n. from Sensillonychiurus taimyrensis sp. n. see description of the latter.

Etymology.

The new species was initially collected during the joint Swedish-Russian expedition arranged in 1994 in order to commemorate A.E. Nordenskiöld’s first trip on “Vega” board along the Northern Sea Route (1878-1879). That is why it is named after Nordenskiöld’s famous steamship “Vega”.

Distribution.

Known from several remote areas of eastern Siberia. Previously, it was erroneously listed for Yakutia as Tantulonychiurus volinensis (Szeptycki, 1964) by Babenko and Fjellberg (2006).