Pseudachorutes minimus Babenko & Shveenkova, 2021

Babenko, Anatoly, Kuznetsova, Natalia, Nakamori, Taizo & Shveenkova, Yulia, 2021, A review of Pseudachorutes Tullberg, 1871 (Collembola, Neanuridae) from the East Asia, with description of six new species, Zootaxa 4938 (4), pp. 351-391 : 359-361

Pseudachorutes minimus Babenko & Shveenkova sp. nov.

Figs 25–30 , Table 1

Type material. Russia: holotype, female, Far East, Khabarovsk Territory, Lazo District , Sikhote-Alin , upper reaches of Katen River , Mount Ko , mixed forest, wood, ~ 500 m alt., 01 July 2018. A. Brinev leg. Paratypes, 2 females, Southern Primor’e, Partisan District, Mount Olkhovaya , 43°20.83’N 133°39.38’E, ~ 1600 m alt., Pinus pumila belt, soil, 20 August 2018 ; 1 male pread., same area, 43°18.35’N 133°40.07’E, ~ 500 m alt., mixed forest in valley, wood, 20 August 2018; 1 female, same biotope, litter; 1 female, slope of same mount, 43°20.25’N 133°39.7’E, ~ 1300 m alt., fir forest, litter, 20 August 2018. All M. Potapov, Yu. Shveenkova & A. Kuprin leg.; 1 male pread., Chuguev District, National Park «Zov Tigra», Mount Oblachnaya , 43°41.70’N 134°11.98’E, ~ 1800 m alt., litter under Pinus pumila , 19–20 September 2018. A. Kuprin leg.

Diagnosis. Small sized species. Ant. IV with usual 6 sensilla on dorsal side. PAO small and rounded with only 4–5 vesicles. Labrum with 4/2334 prelabral and labral setae, labium with full number of ordinary setae, seta L and two labial organites present. Dorsal chaetotaxy of the parvulus type with only 2+2 setae on Th. I and without seta a2 on Th. II. Each anal valve with 2 hr-setae. Mature males lack spine-like setae between furcal base and genital orifice.

Description. Length (without antennae) 0.43–0.60 mm (median— 0.53 mm). Colour blue, not especially dark. Tegument granulation rather coarse and uniform.

Antennae slightly shorter than head, Ant. III–IV fused dorsally, ventral separation well marked. Ant. IV with simple apical vesicle, external ms, subapical or and seta i present; dorsal side of Ant. IV with usual six curved sensilla ( Fig. 26 ). Antennal organ of Ant. III typical ( Fig. 26 ), inner sensilla small, sgv curved and clearly longer than sgd, ventral ms and 18–19 common setae present on Ant. III. Ant. I–II with 7 and (11)12 setae, respectively.

Head with 8+8 subequal ocelli. PAO small, rounded, consisting of (3)4–5 vesicles, about as large as nearest ocellus B, ratio 0.9–1.1 ( Fig. 27 ). Buccal cone moderately elongate. Maxilla styliform with two tiny apical teeth, lamellae not clearly seen. Mandible thin, only two teeth visible. Labrum usually with full number of labral and prelabral setae, 4/2334 totally, but sometimes proximal pair of setae absent. 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. 28 ). Perilabial area in all studied specimens with 4+4 setae.

Typical pattern of dorsal chaetotaxy presented on Fig. 25 , asymmetrical abnormalities not frequent, number of sensilla as usual: 22/11111, their length 1.5–1.8 times longer than ordinary microsetae. Main characteristics: head with unpaired d0, but without a0, Th. I with 2+2 setae, Th. II without a2 setae and only two setae (a3–a4) in front of p3–p4, lateral ms present. Th. III identical, but without ms. Abd. I–III with only one seta (a3) in front of p3–p4, setae of m-row absent. Chaetotaxy of Abd. IV–V slightly reduced: Abd. IV often with only 2+2 p-setae between sensilla p4 and Abd. V usually without both a2 and p2.

Thoracic sterna without setae. Ventral tube with 4+4 setae, no seta on sternum of Abd. I, Abd. II with 2+2 ventral setae, Abd. III usually with 5+5 such setae ( Fig. 29 ). Tenaculum with 3+3 teeth as usual. Furca not especially long. Manubrium with (7)8+8 setae on main part, 3 setae on each basolateral lobe and 2 basal setae in line. Dorsal side of dens with six setae and uniform granulation. Mucro with upturned tip and broad lateral lamella ( Fig. 30 ). 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, 6–7, 8 setae on coxae, 6, 6, 6 on trochanters, 13, 12, (10)11 setae on femora and 19, 19, 18 setae on tibiotarsi. Inner tooth on unguis usually invisible, lateral teeth absent.

Etymology. The name of the new species reflects its small size.

Affinities. Pseudachorutes minimus sp. nov. is the next Far Eastern species, which can be mistakenly identified as P. parvulus due to its small size, few lobes in PAO, simple apical vesicle on Ant. IV, similar dorsal chaetotaxy and labium with the presence of seta L and two labial organites. Nevertheless the presence of four prelabral setae (vs two setae in P. parvulus ), 4+4 setae on the perilabial area (vs 5+ 5 in P. parvulus ), 2+2 setae on Th. I (vs usual 3+3 setae in P. parvulus ) and the absence of setae a2 on Th. II (present in P. parvulus ) make them easy to separate.

Two similar congeners characterized by their small size and few lobes in PAO are known to exist in the eastern part of Asia, namely P. cf. hitakamiensis (see below) and P. armatus sp. nov. described above. Moreover, the former appears to have a sympatric distribution and can be found together with P. minimus sp. nov. in the same soil sample. Nevertheless P. minimus sp. nov. can easily be distinguished from P. cf. hitakamiensis by the presence of four prelabral setae (vs two such setae in P. cf. hitakamiensis ), seta L on labium (absent in P. cf. hitakamiensis ), four setae on basomedian part of labium (usually only three setae present in the same position in P. cf. hitakamiensis ), and 2+2 setae on Th. I (3+3 setae in P. cf. hitakamiensis , at least in adults). Pseudachorutes armatus sp. nov. also has only two prelabral setae (vs four setae in P. minimus sp. nov.), 5 sensilla on Ant. IV (always 6 sensilla in adults of P. minimus sp. nov.), a2 setae on Th. II (absent in P. minimus sp. nov.) and spine-like setae on the ventral side of Abd. IV–V in adult males.

Distribution. The species appears to be widespread, but not particularly abundant in the region under consideration.

Figures

FIGURES 25–30. Pseudachorutes minimus sp. nov.: 25, dorsal chaetotaxy; 26, Ant. III–IV (lateral view); 27, PAO and nearest ocelli; 28, labium; 29, ventral chaetotaxy of abdomen; 30, dens and mucro. Scales: Figs 25, 29 = 0.1 mm, 26–28, 30 = 0.01 mm.