Philotella oligotricha, Babenko & Shveenkova & Potapov, 2022

Babenko, Anatoly, Shveenkova, Yulia & Potapov, Mikhail, 2022, New species of the genus Philotella Najt & Weiner, 1985 (Collembola, Neanuridae, Pseudachorutinae) from the Russian Far East, Zootaxa 5174 (5), pp. 525-550 : 531-532

Philotella oligotricha sp. nov.

Figs 10–16

Type material. Holotype: female, Southern Primorye , «Kedrovaya Pad» State Nature Reserve ( Fig. 1 , point 3), mixed coniferous-broadleaf forest, 43°6.88’N 131°29.23’E, ~ 120 m alt., litter, 27 July 2016. N. Kuznetsova & M. Potapov leg. Paratypes: 1 immature male, same habitat; 2 immature males and 1 juvenile, same region and Nature Reserve , oak-wood, 43°6.06’N 131°33.68’E, ~ 150 m alt., litter, 28 July 2016 ; 1 female, same region, near Anisimovka , Mount Khualaza ( Fig. 1 , point 5), greenwood forest, 43°7.56’N 132°47.82’E, ~ 400 m alt., litter and rotten wood, 21 July 2016 ; 1 immature female, same region, Ussuri State Nature Reserve ( Fig. 1 , point 4), forest with P. koraiensis , 43°38.88’N 132°21.09’E, ~ 200 m . alt., 22 July 2016. N. Kuznetsova & M. Potapov leg.

Additional material. 5 females, Khabarovsk Territory, Lazo District, upper reaches of Katen River , Ko Mountains ( Fig. 1 , point 10), ~ 500 m alt., mixed forest, litter, 01 July 2018. A. Brinev leg. ; 2 females, 1 immature male and 11 juveniles, Southern Primorye, Partisan District, Mount Olkhovaya ( Fig. 1 , point 6), mixed forest in valley, 43°18.35’N 133°40.07’E, ~ 500 m alt., litter, 20 August 2018. M. Potapov, Yu. Shveenkova & A. Kuprin leg. ; 1 immature female and 1 immature male, Southern Primorye, Chuguev District, National Park «Zov Tigra», Mount Oblachnaya , Ussuri River valley , mixed forest, 43°36.04’N 134°11.58’E, ~ 550 m alt., litter, 19–20 September 2018. A. Kuprin leg. ; 7 juveniles, Khabarovsk Territory, Komsomolsk State Nature Reserve, Anyuinski National Park , Tormasu River (( Fig. 1 , point 13), mixed coniferous-broadleaf forest, litter, 49°18.2’N 137°34.2’E, ~ 200 m alt., 07 August 2018. N. Kuznetsova, A. Kuprin & A. Geraskina leg.

Diagnosis. A dark species characterized by the presence of 3+3 subequal ocelli; the second row of labral setae with three longer and two shorter setae; a labium of the second type; reduced dorsal chaetotaxy without p2 on all terga from Th. II to Abd. V; a dorsolateral group of setae on Th. II–III with sensillum p3 set below two ordinary setae (a3 and m4); a complete tibiotarsal chaetotaxy and toothless unguis.

Description. Length (without antennae) of available specimens 0.38–0.59 mm, holotype — 0.48 mm. Habitus typical of the genus. Colour dark blue, uniform. Tegument granulation very strong, especially on abdominal tip.

Antennae clearly shorter than head, Ant. III–IV fused dorsally. Ant. IV with simple or slightly divided apical vesicle; external ms, subapical or and seta i present; six sensilla (S1–S4, S7–S8) on dorsal side of Ant. IV blunt and elongate ( Fig. 12 ); few sensilliform setae of various shape also present on its ventral side. Antennal organ of Ant. III typical, inner sensilla small, sgv longer than sgd and curved, ventral ms present. Ant. I–II with 7 and 11 setae, respectively.

Head with 3+3 ocelli, clearly larger than surrounding secondary granules on ocular field. PAO rounded, consisting of 7–10 vesicles, its axis to ocellus B ratio as 1.6–2.0: 1. Buccal cone short and blunt. Maxilla styliform, with at least two lamellae, one of which bearing two hooks, another one with few apical denticles ( Fig. 14 ). Mandible delicate, with five usual teeth, among them two tiny ones between apical and two basal teeth ( Fig. 15 ). Labrum usually with a common set of 4/2352 setae of different length, distal pair and three setae of the next row being the longest ( Fig. 13 ). Main part of labium of the second type with three ordinary setae in triangular position and 1+1 axial setae between sensorial elements ( Fig. 16 ); submentum and mentum with usual set of four setae each. Head ventrally with 2+2 postlabial setae.

Dorsal chaetotaxy symmetrical and rather reduced ( Fig. 10 ). Ordinary setae short, needle-like, sensilla longer, clearly differentiated, their number as usual: 22/11111, lateral ms present on Th. II. Main characteristics: head usually with unpaired seta d0 and only 2 setae on each ocular field; Th. I with 3+3 setae; all terga from Th. II to Abd. IV with 2+2 axial setae (p2 absent); dorso-lateral group on Th. II–III consisting of 2 ordinary setae (a3 and m4) additionally to sensillum p 3 in backward position; Abd. V with only 1+1 setae between sensilla.

Thoracic sterna without setae. Ventral tube with 4+4 setae, no seta on sternum of Abd. I, ventral side of Abd. II–III without unpaired axial setae ( Fig. 11 ). Furcal remnant in a form of two small warts, each with a seta, on anterior border of Abd. IV. Each anal valve usually with three setae hr, but variations frequent.

Legs I–III with 1, 2, 2 setae on upper subcoxae, 0, 2, 2 setae on lower subcoxae, 3, 6, 6 setae on coxae, 6, 6, (5)6 on trochanters, and 13, 12, 11 setae on femora. Tibiotarsi with most complete set of setae: 19, 19, 18, seta M present. Unguis toothless.

Remarks. The material from the Zeya State Nature Reserve (Amur Region, Fig. 1 , point 1) contains three juvenile specimens of a very similar form, which differs from P. oligotricha sp. nov. by the presence of 5+5, not 3+3 ocelli. Other detected differences are minimal: the presence of three setae on the ocular field (vs only two setae in P. oligotricha sp. nov.) and 2+2 setae between sensilla on Abd. V (vs 1+1 setae in this position in P. oligotricha sp. nov.). Most likely, this is a different species, which cannot yet be described due to the lack of sufficient material.

Etymology. The name of the new species reflects one of its most characteristic features, i.e. the relatively small number of dorsal setae; from ancient Greek όλίγος (few, little) & τρίχα (seta).

Affinities. Apart from the reduced number of ocelli, a character not always easy to correctly identify, P. oligotricha sp. nov. resembles P. deharvengi and P. tertia , the latter two species known from the neighbouring region. All these three species have an almost identical dorsal chaetotaxy with 2+2 axial setae on all terga from Th. II to Abd. III, and a backward position of sensilla in the dorsolateral groups of Th. II–III. Philotella oligotricha sp. nov. differs from P. deharvengi in having a different type of the labium (the first type in P. deharvengi , vs the second one in P. oligotricha sp. nov.) and 1+1 axial setae between sensilla only on Abd. V (vs 1+1 such setae on both Abd. IV and Abd. V in P. deharvengi ). The chaetotaxy of the abdominal tip in P. tertia is characterized by the presence of 2+2 axial setae on both Abd. IV and Abd. V. Apart from this, both Korean species lack M-setae on all tibiotarsi and have an inner tooth on the unguis.

The dorsal chaetotaxy of P. oligotricha sp. nov. is also quite similar to that of P. porcella comb. nov. (central Alaska), the only known Nearctic representative of the genus, although the latter species is characterized by the anterior position of the sensillum in the dorsolateral group on Th. II–III, and the presence of 2+2 axial setae between sensilla on both Abd. IV and Abd. V.

Figures

FIGURE 1. Map of main sampling plots. 1, Amur Region, Zeya State Nature Reserve; 2, Amur Region, Arkhara; 3, Southern Primorye, «Kedrovaya Pad» State Nature Reserve; 4, Southern Primorye, Ussuri State Nature Reserve; 5, Southern Primorye, Anisimovka, Mount Khualaza; 6, Southern Primorye, Mount Olkhovaya; 7, Southern Primorye, Chuguevka; 8, Southern Pri- morye, Mount Oblachnaya; 9, Southern Primorye, Sikhote-Alin State Nature Reserve; 10, Khabarovsk Territory, Ko Mountains; 11, Khabarovsk Territory, “Arseniev’s granites” Mts. Range; 12, Khabarovsk Territory, Komsomolsk State Nature Reserve; 13, Khabarovsk Territory, Tormasu River; 14, Khabarovsk Territory, Anyuinski National Park.

FIGURES 10–16. Philotella oligotricha sp. nov.: 10, dorsal chaetotaxy; 11, ventral chaetotaxy of abdomen; 12, Ant. III–IV (lateral view); 13; labrum; 14, maxillary head; 15, mandible; 16, labium. Scales. Figs 10–11: 0.1 mm; 12–16: 0.01 mm.