Pseudachorutes cf. hitakamiensis Tamura, 2001

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 : 373-376

Pseudachorutes cf. hitakamiensis Tamura, 2001

Figs 66–71

Examined material. Russia: 6 females and 1 male, Far East, Southern Primor’e, 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 male, same data, but 4 August 2017 ; 1 male, same Nature Reserve , mixed forest, 43°38.2’N 132°20.98’E, ~ 380 m alt., litter, 23 July 2016. N. Kuznetsova & M. Potapov leg. ; 1 male, 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 female, same region, but Sikhote-Alin State Nature Reserve , oak forest on gentle slope, 44°58.9’N, 136°32.05’E, ~ 200 m alt., 6.08.2017. N. Kuznetsova, A. Kuprin & A. Geraskina leg. ; 3 females and 1 male, same Nature Reserve , coniferous forest with Rhododendron brachycarpum , 45°8.30’N 135°53.22’E, ~ 930 m alt., 08 August 2017. N. Kuznetsova, A. Kuprin & A. Geraskina leg. ; 1 juvenile, same region, «Kedrovaya Pad» State Nature Reserve , mixed coniferous-broadleaf forest, 43°6.95’N 131°30.42’ E, ~ 100 m alt., 29 July 2016. N. Kuznetsova and M. Potapov leg. ; 1 male, 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. ; 3 females and 2 males, same region, upper reaches of Sukpai River , 1650 m alt., mountain tundra, mosses, 19 June 2018. A. Brinev leg.

Japan: 1 female, Honshu Island, Nagano Prefecture, E Chino city, Kitayama, surroundings of Mugikusa Hutte, 36°3.27’N 138°19.95’E, ~ 2050 m alt., humid forest with old Abies trees, litter and turf ( Lycopodium , Carex , Polytrichum ), 12 August 2016. M. Potapov & N. Kuznetsova leg.

South Korea: 2 females, Gangwon-do , vicinities of Yeongwol , bank of Han-gang (East river), Ulmus forest in valley, 10 September 2017. A. Kuprin leg.

Main diagnostic characters: Small-sized species. PAO rounded with up to 8 vesicles. Labrum with only 2/334 setae, labium with 4 proximal setae, L absent, basomedial part of labium usually with only 3 setae (E—absent), rarely all four setae present. Th. II usually without a2, Th. II–III with 3 ordinary setae additionally to S in dorsoexternal group, Abd. I–III with only one seta (a3) in front of p3 and p4 (= S), Abd. V with or without a2. Each anal valve with two hr-setae.

Description. Small species with slender body, length (without antennae) of adults usually from 0.38 to 0.58 mm, but one larger female (0.83 mm) also seen. Colour grey-blue, not especially dark. Tegument granulation rather coarse and uniform.

Antennae slightly shorter than head, Ant. III–IV fused dorsally, ventral separation well marked. Apical vesicle on Ant. IV usually simple, rarely slightly divided, external ms, subapical or and seta i present; dorsal side of Ant. IV with 6 differentiated, curved sensilla (S1–S4, S7–S8), ventral side with few pointed setae ( Fig. 67 ). Antennal organ of Ant. III typical, inner sensilla small, sgv slightly curved and clearly longer than sgd, ventral ms present. Ant. I–II with 7 and 12 setae, respectively.

Head with 8+8 subequal ocelli. PAO rounded, consisting of 6–8 vesicles, larger than nearest ocellus B, ratio 1.4–1.6: 1 ( Fig. 68 ). Buccal cone short. Maxilla styliform, lamellae not clearly seen. Mandible with two teeth. Distal edge of labrum rounded, number of labral setae as follows: 2/334. Main part of labium with four proximal ordinary setae, seta L and labial organites invisible ( Fig. 69 ); number of setae on basal parts of labium variable (see Variation part), but usually without seta E on submentum ( Fig. 69 ). Perilabial area with 5+5 setae.

Typical pattern of dorsal chaetotaxy presented on Fig. 66 , 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 3+3 setae, Th. II with or without setae a2, 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. V without p2 as usual, a2 present or absent.

Thoracic sterna without setae. Ventral tube with 4+4 setae, no seta on sternum of Abd. I, Abd. II with 3(4)+3(4) ventral setae, Abd. III with 5–6 setae on each side. Tenaculum with 3+3 teeth as usual. Furca not long, slightly passing over Abd. II–III border. Manubrium with (7)8+(7)8 setae on main part, 3–4 setae on each basolateral lobe and 2 basal setae in line ( Fig. 70 ). Dorsal side of dens with six setae and uniform coarse granulation, hyaline field on its ventral side rather large. Mucro with upturned tip and broad and lateral lamella almost reaching tip ( Fig. 71 ). Each anal valve with two hr-setae.

Legs I–III with 1, 2,2 setae on upper subcoxae, 0, 2, 2 setae on lower subcoxae, 3, 6–7, 7 setae on coxae, 6, 6, 6 on trochanters, 13, 12, 11 setae on femora and 19, 19, 18 setae on tibiotarsi. Unguis with inner tooth in lower half of inner edge, lateral teeth invisible.

Variation. It should be noted that in our material from the Russian Far East, two important characteristics of chaetotaxy, which are considered fairly constant within the genus, are variable. In particular, all specimens from three state reserves (Ussuri, Sikhote-Alin, and Kedrovaya Pad) lack setae a2 on Th. II and seta E on the submentum ( Fig. 69 ), while both these setae may be present or absent together or separately in specimens from Khabarovsk Territory. Two females from South Korea are characterized by the presence of a2 on Th. II, but have no seta E on the submentum as the main form from Primor’e. Besides, a single male with the same set of characters (a2 is present on Th. II and submentum without seta E) was also seen in materials from Sakhalin. The latter has only three setae on the mentum and an unstable number of setae (4+5) in the perilabial area.

Remarks. The assignment of our materials from the Russian Far East to P. hitakamiensis , described from Japan, is rather arbitrary. Initially, we believed that individuals with the absence of seta E on labium and without setae a2 on Th. II represent a new species that differs from typical P. hitakamiensis in these very features. The discovery of populations, in which these characters vary independently of each other, has forced us to reconsider this point of view. Nevertheless, it is highly probable that P. cf. hitakamiensis in this broader sense is a complex of several cryptic species, which separation at present can only be very subjective.

The main diagnostic features of P. hitakamiensis ( Table 1) are almost identical to those of true P. parvulus , and most likely this particular species has been registered in the region ( Solntseva & Kutyreva 1979; Weiner & Najt 1985) under this name. Nevertheless, our material from the Russian Far East, as well as the original description, clearly differ from the modern understanding of P. parvulus according to Jordana et al. (1997), Fjellberg (1998) and Kaprus’ & Weiner (2009) by the labral chaetotaxy (2/334 vs 2/2334 setae in P. parvulus ), labium (seta L absent vs present in P. parvulus ) and the number of mandibular teeth (2 vs 4 teeth in P. parvulus ).

In fact, P. hitakamiensis itself may well be the junior synonym of P. infuscata Yosii, 1954 , described as a form of P. parvulus and currently regarded as a synonym of the latter (see www. collembola.org). The differences between P. infuscata and P. parvulus are quite comparable with those between P. infuscata and P. hitakamiensis and are most likely due to inaccuracies in the original descriptions. However, the formal synonymisation of P. hitakamiensis and P. infuscata obviously requires additional studies.

Distribution. The species was described from Japan, probably recorded from North and South Korea and is widespread in the Russian Far East being found in three remote State Nature Reserves (Sikhote-Alin, Ussuri and Kedrovaya Pad), as well as in the northern part of the Khabarovsk Territory.

Figures

FIGURES 66–71. Pseudachorutes cf. hitakamiensis Tamura: 66, dorsal chaetotaxy; 67, Ant. III–IV (lateral view); 68, PAO and nearest ocelli; 69, labium; 70, ventral chaetotaxy of abdomen; 71, dens and mucro. Scales: Figs 66, 70 = 0.1 mm, 67–69, 71 = 0.01 mm.