Sensillonychiurus taimyrensis, 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 : 10-11

Sensillonychiurus taimyrensis sp. n. Figs 810-14, 18, 21

Material.

Holotype ♀, Russia, Taimyr Peninsula, northern coast of Taimyr Lake, Postoyannaya River [74°38'N, 101°55'E], low river terrace, mosses, Dryas sp., Astragalus spp., 02.viii.1993, leg. A. Babenko (MSPU).

Paratypes 5 ♀ and 4 ♂, same data as holotype; 2 ♀ and 1 ♂, Taimyr Peninsula, northwestern coast of Lake Pyasino [70°04'N, 87°39'E], herbaceous meadow on south-facing slope, sand, 03.viii.2001; 16 ♀, 10 ♂ and 6 juv., Taimyr Peninsula, middle reaches of Pyasina River, Ust-Tareya [73°15'N, 90°35'E], herbaceous meadow on south-facing slope, 22.vii.2010, leg. A. Babenko (MSPU).

Other material. 1 ♀, Russia, Siberia, northwestern Buryatia, Ust’ -Barguzin [53°25'N, 109°01'E], Lake Baikal shore, sandy beach (ca 5 m from water edge, flotation), 21.viii.2008, leg. M. Potapov; 1 ♀, Russia, Siberia, Buryatia, Vitim Plateau, vicinity of Eravna (Sosnovo-Ozerskoe) [52°27'N, 111°09'E], dry birch forest, 21.viii.2009, leg. A. Chimitova.

Description.

Colour white. Size 0.56-0.62 mm. Body slender and elongated. Antennae about as long as head, antennal area not clearly demarcated. Ant.4 with a subapical organite, two distinct thickened sensilla, and a subbasal microsensillum set well above proximal row of setae (Figs 10-14). Ant.3 organ consisting of 4 papillae, 2 sensory rods, 2 smooth sensory clubs, 3 guard setae, and a lateral microsensillum (Fig. 10). Ant.1 and 2 usually with 8 and 13 setae, respectively. PAO with 7(8) composed vesicles. Labrum with 7 setae and 2 prelabral ones (2/3-4). Apical part of labium of AC-type, with (5)6 proximal setae and usually with a complete set of guard setae (11), although asymmetrical absence of one of e-guard setae also visible, a1-guard long. Basal fields of labium (mentum and submentum) with 4 and 5 setae. Hypostomal complex with one long and one shorter projection. Maxillary palp simple, with 2 sublobal setae.

Pseudocellar formula (pso) as follows, dorsal: 32/133/33343, ventral: 1/000/0000, parapseudocelli (psx) invisible. Each upper subcoxa with one pso. Localization of pso as in Fig. 8. Granulation rather fine and uniform, without areas of clearly enlarged granules. Dorsal chaetotaxy almost symmetrical, setae smooth and clearly differentiated, especially on last abdominal terga, in anterior parts of body meso and microsetae similar in size but differing in shape: mesosetae straight and blunt, microsetae curved and pointed, sensilla more or less distinct on terga and less evident on sterna: 1/011/221-2111 (dorsal) (Fig. 8) and 2/000/0000-1 (ventral), sensillum on coxae of Lg.3 present but not distinct. Th.1 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 8, 18). Axial microsetae p1 set anteriorly to mesosetae p2 on Abd.1-3 (Fig. 21). Thoracic sterna without setae along linea ventralis. Abd.3 sternum unclearly divided, anterior subsegment 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 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. Unguis simple, with neither inner nor lateral tooth, unguiculus with an indistinct basal lamella, clearly shorter than unguis (about 0.6-0.65 U3).Anal spines short (0.7-0.75 U3) but rather thick (thickness/length 0.23-0.28), set on low papillae.

Affinities.

Apart from Sensillonychiurus taimyrensis sp. n., only two known species of the genus, i.e. Sensillonychiurus minusculus and Sensillonychiurus vegae sp. n., completely lack all T-setae on tibiotarsi (distal whorl with 7 setae). Sensillonychiurus minusculus clearly differs in having lateral ms on Th.3 and Abd.6 without AS. Two other species, Sensillonychiurus vegae sp. n. and Sensillonychiurus taimyrensis sp. n. are very similar, sharing many common characteristics (see Table 1). Nonetheless Sensillonychiurus taimyrensis sp. n. can be easily distinguished due to stronger AS set on low papillae (cf. Figs 18 and 19), more distal position of ms on Ant.4 (cf. Figs 10-14 and 15-17) and clear differences in the mutual position of microsetae p1 and mesosetae p2 on Abd.3 (cf. Figs 21 and 22).

Etymology.

The new species was named after its terra typica.

Distribution.

Despite a few records the new species is probably widespread in eastern Siberia being found in such remote regions as Taimyr’s tundras and mountainous Buryatia. Previously the species was erroneously listed for Taimyr as Tantulonychiurus volinensis (Szeptycki, 1964) by Babenko (2003) and Babenko and Fjellberg (2006).