Sensillonychiurus mirus, 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 : 9-10

Sensillonychiurus mirus sp. n. Figs 1-7

Material.

Holotype ♀, Russia, NW of European part, Kola Peninsula, Dalnie Zelentsy [69°07'N, 36°03'E], coastal sandy steep with sparse vegetation (flotation), 19.vii.2009, leg. A. Babenko (MSPU).

Paratypes 5 ♀, same data as holotype (MSPU).

Description.

Colour white. Size 0.56-0.60 mm. Body slender and elongated. Antennae about as long as head, antennal area not clearly demarcated. Ant.4 with two distinct thickened sensilla, subapical organite and basal microsensillum present (Fig. 1). Ant.3 organ consisting of 5 papillae, 2 sensory rods, 2 smooth and usually slightly bilobed sensory clubs (Fig. 2), 4 guard setae, and a lateral microsensillum (Fig. 1). Ant.1 and 2 with 7-8 and 12-13 setae, respectively. PAO with 7-8 composed vesicles (Fig. 3). Labrum with 7 setae and 4 prelabral ones. Apical part of labium with thick terminal setae on papillae A, B and C (ABC-type), 11 guard setae, a1 clearly longer and thicker than other spiniformguard setae, i.e. b1-2 and d2 (Fig. 4), and 5 proximal setae. Basal fields of labium (mentum and submentum) with 4 and 5 setae, hypostomal complex reduced to one long seta and a minute projection. Maxillary palp simple, with 2 sublobal setae.

Pseudocellar formula (pso) as follows, dorsal: 2(3)2/133/33343 (rarely some pso duplicated), ventral: 1/000/0000, parapseudocelli (psx) invisible. Each upper subcoxa with one pso. Localization of pso as in Fig. 5. Granulation fine and uniform, without areas of enlarged granules. Dorsal chaetotaxy almost symmetrical, setae smooth and clearly differentiated only on abdominal tip, in more anterior parts of body setae differing in shape but not in size: some of them straight, thick and blunt, others curved and pointed, sensilla distinct: 2/022/222221 (dorsal) and 2/000/00011 (ventral) (Figs 5-6), occasionally some additional mesosetae can be thickened and look like other sensilla, thickened sensillum present on coxae Lg.3 (Fig. 7). Th.1 with 6+6 setae as a rule. 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 dorsally with one axial macroseta and 1+1 prespinal microsetae (Fig. 5). Thoracic sterna without setae along linea ventralis, ventral chaetotaxy of abdomen as in Fig. 6. 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 2 rows, manubrial area with 4+4 setae set in two rows (Fig. 6). Ventral tube with 6+6 distal setae, proximal ones at corpus base absent. Upper subcoxae usually with 3-3-4, tibiotarsi with 17-17-16, setae: distal whorl with 9 setae (7 A and two T-setae), 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, shorter than unguis (Fig. 7). Anal spine short but rather strong, set on unclear papillae.

Affinities.

Sensillonychiurus mirus sp. n. clearly differs from the all previously described species of the genus first of all in having not three but four guard setae in AO. Nevertheless it is not a unique character for the group. The same structure of AO (5 papillae and 4 guards) as in Sensillonychiurus mirus sp. n. is known in two other species of the genus, Sensillonychiurus vitimicus sp. n. and Sensillonychiurus amuricus sp. n. (see descriptions below). All these species which are characterized by only a weak reduction of AO with a highest possible number of papillae and 4 guard setae have many other characteristics in common (see Table 1.). Nonetheless, Sensillonychiurus mirus sp. n. can easily be distinguished from Sensillonychiurus vitimicus sp. n. by the complete absence of setae on thoracic sterna, from Sensillonychiurus amuricus sp. n. in the different type of labium (ABC in Sensillonychiurus mirus sp. n. versus AC in Sensillonychiurus amuricus sp. n.), and in four prelabral setae ( Sensillonychiurus amuricus sp. n. possesses only two prelabral setae which are more common in the genus).

Etymology.

Initially, the name mirus (odd, strange, unusual in Latin) reflects both an isolated position of the new species within the genus and the gap between its type-locality and the distributions of the other known species of the genus which are pure Asiatic or American. The level of morphological uncommonness has lowered after the performed survey of all available material, but the geographical isolation still exists.

Distribution.

Known only from the type locality.