Pseudachorutes variabilis Babenko & Kuznetsova & Nakamori & Shveenkova 2021, sp. nov.

Pseudachorutes variabilis Babenko & Shveenkova sp. nov.

Figs 31–35, 37–39, Table 1

Type material. Russia: holotype, female, Far East, Southern Primor’e, Sikhote-Alin State Nature Reserve, coniferous forest with Rhododendron brachycarpum, 45°8.30’N 135°53.22’E, ~ 930 m alt., 08August 2017. N. Kuznetsova, A. Kuprin & A. Geraskina leg. [MSPU collection]. Paratypes, 1 female, same region, Ussuri State Nature Reserve, forest with Pinus sibiricus, 43°38.88’N 132°21.1’E, ~ 200 m. alt., 22 July 2016. N. Kuznetsova & M. Potapov leg.; 1 female, same Nature Reserve, mixed forest, 43°38.2’N 132°20.98’E, ~ 380 m alt., litter, 24 July 2016. N. Kuznetsova & M. Potapov leg.; 1 juvenile, same region, but ~ 30 km SE of Chuguevka, mixed forest, 44°1.32’N 134°9.02’E, 500 m alt., 11 August 2017. N. Kuznetsova, A. Kuprin & A. Geraskina leg.; 1 male and 1 juvenile, same region, but «Kedrovaya Pad» State Nature Reserve, mixed coniferous-broadleaf forest, 43°6.88’N 131°29.23’E, ~ 100 m alt., litter, 27 July 2016. N. Kuznetsova & M. Potapov leg.; 1 female, same region, Chuguev District, National Park «Zov Tigra», Mount Oblachnaya, Ussuri River valley, 43°36.04’N 134°11.58’E, ~ 550 m alt., mixed forest, litter, 19–20 September 2018. A. Kuprin leg.; 3 females, northern part of Khabarovsk Territory, Ezop Mt. Range, Bureinskaya Rassoshina River, alpine belt, 1900–2000 m alt., 29 June 2006. A. Brinev & A. Polyakov leg.; 2 females and 1 male, Kamchatka, environs of Petropavlovsk, Khalatyrsky beach [~ 52°58’N, 158°49’E], seaside meadow, under Leymus sp., sand, July 2018. L. Lobkova leg. [MSPU collection]

Other material. 1 female, Japan, Honshu Island, Nagano Prefecture, E Chino city, Kitayama, surroundings of Mugikusa Hutte, 36°2.72’N 138°21.92’E, 2150 m alt., mixed forest (Betula, Tsuga, Abies), litter, 10 August 2016. M. Potapov & N. Kuznetsova leg. [MSPU collection]

Diagnosis. Medium sized species. PAO rounded, slightly larger than nearest ocellus. Buccal cone elongate, complete set of labral setae (4/2334 totally), labium with seta L and labial organites additionally to 12 ordinary setae, 5 setae in perilabial area. Dorsal chaetotaxy of the parvulus type, Th. I with 3+3 setae, most of dorsal setae on abdominal tip more or less clearly modified, sensilla short (about as long as ordinary setae). Mucro with lateral lamella almost reaching tip. Each anal valve with two hr-setae.

Description. Length (without antennae) up to 1.52 mm, but usually smaller, holotype— 1.4 mm. Colour greyblue, not especially dark. Tegument granulation rather coarse, especially in larger specimens.

Antennae slightly shorter than head, Ant. III–IV fused dorsally, ventral separation well marked. Ant. IV with simple or slightly divided apical vesicle, external ms, subapical or and seta i present; dorsal side of Ant. IV with six clearly differentiated, curved sensilla (S1–S4, S7–S8), ventral side with utmost few pointed, truncate or slightly clavate sensilliform setae (Fig. 39). Antennal organ of Ant. III typical, inner sensilla small, sgv slightly curved and clearly longer than sgd, ventral ms present. Ant. I–II with usual 7 and 12 setae, respectively.

Head with 8+8 subequal ocelli. PAO rounded or slightly elliptic, consisting of 8–12 vesicles, slightly larger than nearest ocellus B, ratio 1.2–1.3: 1. Buccal cone elongate. Maxilla styliform with tiny apical teeth, lamellae not clearly seen. Mandibles thin and membranous, usually with four apical teeth (Fig. 38). Distal edge of labrum pointed, number of labral setae as follows: 4/2334. Main part of labium with four proximal ordinary setae, distal seta L on tiny papilla and two labial organites; submentum and mentum with usual set of four setae each, i.e. 4+4 (Fig. 35). Perilabial area usually with 5+5 setae.

Most of dorsal setae, especially on abdominal tip modified. Degree of these modifications in different specimens highly variable: from truncated or slightly capitate setae (Figs 31–32) to distally widened and flattened ones (Figs 33–34, 34a), sensilla short (about as long as ordinary setae or even shorter), their number as usual, i.e. 22/11111. Main characteristics: head with unpaired d0, but without a0, setae sd2 at level or slightly posterior to d2 (Figs 31, 33), Th. I usually with 3+3 setae (but one female with abnormal 3+4 also seen), Th. II with a2-setae, dorso-external group with two setae (a3–a4) in front of p3–p4, only lateral m6 (S) in m-row, lateral ms present. Th. III identical, but without a2 and ms. Abd. I–III with only one seta (a3) in front of p3–p4, setae of m-row absent.Abd. IV with 9+9 setae in a–p rows, setae of m-row absent. Abd. V without p2 as usual (Figs 32, 34).

Thoracic sterna without setae. Ventral tube with 4+4 setae, no seta on sternum of Abd. I, Abd. II with (3)4+4 ventral setae, Abd. III with 5–7 setae. Tenaculum with 3+3 teeth as usual. Furca not especially long. Manubrium with 8–9+8–9 setae on main part, 4 setae on each basolateral lobe and 2 basal setae in line. Dorsal side of dens with six setae and uniform coarse granulation, hyaline field on its ventral side rather large. Mucro with upturned tip and lateral lamella almost reaching tip. Each anal valve with two tiny hr-setae.

Legs I–III with 1, 2, 2 setae on upper subcoxae, 0, 2, 2 setae on lower subcoxae, 3, 7, 7 setae on coxae, 6, 6, 6 on trochanters, 13, 12, 11 setae on femora and 19, 19, 18 setae on tibiotarsi. Unguis with clear inner tooth in mid part of inner edge and pair of tiny lateral ones in basal half (Fig. 37).

Etymology. The name of the new species reflects a high variability of the shape of its dorsal setae.

Affinities. The main diagnostic features of P. variabilis sp. nov. are identical to those of P. subcrassus Tullberg, 1871, which probably has a predominantly European range. Both these species are characterized by similar sensory equipment of Ant. IV, labrum with 4/2334 setae, labium with seta L and two organites additionally to 12 ordinary setae, practically identical mandibular shape, unguis with a clear inner tooth and mucro of similar shape. Both species also have the same type of dorsal chaetotaxy with 3+3 setae on Th. I, Th. II with a2 setae, two setae in front of p3–p4 on Th. II–III and one a 3 in front of p3–p4 on Abd. I–III. In addition to the differences in the shape of the dorsal setae, which is a highly variable feature in P. variabilis sp. nov., these species differ in a number of small but constant characters. For instance, labrum in P. variabilis sp. nov. is pointed distally but rounded in P. subcrassus (cf. Fig. 35 and Fig. 36), lateral teeth on unguis is located in basal part in P. variabilis sp. nov., but subapically in P. subcrassus. Kaprus’ & Weiner (2009) suggested using the relative position of the setae d2 and sd2–sd3 on the head as an additional criterion for distinguishing between P. parvula and P. subcrassus, i.e. d2 at the level of sd2 (parvulus) or sd3 (subcrassus). The position of these setae in P. variabilis sp. nov. (Fig. 31) is more similar to that of P. parvulus, than P. subcrassus.

Distribution. The species appears to be widespread in the studied region; it was found in three State Nature Reserves (Sikhote-Alin, Ussuri and Kedrovaya Pad), in the northern part of the Khabarovsk Territory, Kamchatka and in Japan.