Pseudachorutella stebaevae, Babenko & Kuznetsova, 2024

Babenko, Anatoly & Kuznetsova, Natalia, 2024, Three new species of the genus Pseudachorutella Stach, 1949 (Collembola, Neanuridae) from Russia, Zootaxa 5447 (2), pp. 188-198 : 195-197

Pseudachorutella stebaevae sp. nov.

Figs 20–27

Type material. Holotype: female, Russia, Siberia, northeastern Altai Mountains, Lake Teletskoe , vicinity of Artybash [51°47’28’’N 87°15’21’’E], field station [of the Institute of Animal Systematics and Ecology, Siberian Branch, Russian Academy of Sciences], under bird-cherry tree, pit traps, 11– 12.09.1988. S.K. Stebaeva leg. Paratypes: one juvenile, Siberia, Kemerovo Oblast, Novokuznetsk, vicinity of Badaevka , birch forest, 28.05.1981 ; 2 juveniles, same region, vicinity of Mezhdurechensk [53°45’N 88°00’E], zonal taiga, litter, 15.06.1981 ; one juvenile, same region and habitat type, but 01.07.1982; 3 females and one male, Western Sayan Mountains, Olenya Rechka River [52°48’N 93°15’E], mosses in upper limit of forest belt, 06.27.1990. All S.K. Stebaeva leg. ; one juvenile, Kemerovo Oblast, road between Tashtagol and Kuzedeevo , 53.2245 oN 87.1414 oE, old aspen forest, 09.10.2020. M. Potapov & N. Kuznetsova leg.

Diagnosis. A large-sized species of the genus. Sensorial equipment of Ant. IV usual for the genus with eight blunt dorsal sensilla and many small sensorial elements ventrally. Buccal cone long, labrum with a pointed edge and 4/2334 setae, i.e. a medial pair of prelabral setae present. Labium with 12 ordinary setae and a subapical spine L, organites small, poorly visible. Maxillae with two small apical hooks. Mandibles with 6 teeth. Dorsal chaetotaxy rich, with many supplementary setae including three ordinary setae additionally to sensillum on dorsolateral parts of Th. II–III.

Description. Length (without antennae) up to 3.6 mm, holotype –– 1.79 mm. Colour of dorsal side dark, grayish-blue, with numerous light spots; ventral side paler. Tegument granulation coarse and almost uniform becoming slightly enlarged on abdominal tip.

Antennae about as long as head, Ant. III–IV fused dorsally, ventral separation well marked. Ant. IV with a trilobed apical vesicle, external ms, subapical or and seta i present; eight sensilla (S1–S8) on dorsal side of Ant. IV clearly differentiated ( Fig. 23 ), ventral «file» with numerous sensilliform setae covering more than half of ventral side ( Fig. 22 ). Antennal organ of Ant. III typical, inner sensilla small, sgv about as long as sgd (cf. Fig. 22 and Fig. 23 ), ventral ms and about 20 common setae present. Ant. I–II with 7 and 13–14 setae, respectively.

Head with 8+8 subequal ocelli. PAO absent. Buccal cone long and pointed. Maxilla styliform with two apical hooks and a pointed lamella with some denticles on tip ( Fig. 24 ). Mandible with three tiny apical and three stronger basal teeth ( Fig. 25 ). Distal edge of labrum pointed (ogival), number of prelabral and labral setae as follows 4/2334. Labium with usual 12 setae and a subapical spine ( Fig. 18 ), small, poorly visible organites present. Total length of labium is 5.0–5.5 of distance between postlabial setae a1 and m1. Perilabial area with 4+4 setae.

Ordinary setae on dorsal side of body short, smooth and acuminate, sensilla 1.6–2.2 times longer than ordinary setae ( Figs 20 ), their number as usual: 22/11111. Main characteristics of dorsal chaetotaxy ( Fig. 20–21 ): head without a0, d0 present or absent; Th. I with 4+4(5) setae; all terga from Th. II to Abd. VI with some additional setae in dorso-external group; dorso-lateral group of setae on Th. II–III with 3 ordinary setae. Abd. V with setae p2 present ( Figs 20–21 ).

Thoracic sterna without setae. Ventral tube with 4(5) distal setae on each side, no seta on sternum of Abd. I, Abd. II with 7–9 ventral setae on each side. Tenaculum with 3+3 teeth as usual. Furca strong, dorsal side of dens with six setae and coarse granulation, hyaline field on its ventral side slightly shorter than mucro length. Mucro with relatively low lateral lamella not reaching tip. Each anal valve with two small hr-setae.

Legs I–III with an almost stable set setae: 1, 2, 2 setae on upper subcoxae, 0, 2(3), 2(3) setae on lower subcoxae, 3, 8, 8 setae on coxae, 6, 6, 6 on trochanters, 13, 12, 11 setae on femora and 19, 19, 18 setae on tibiotarsi. Unguis with a clear tooth in mid part of inner edge and two lateral teeth basally ( Fig. 26–27 ), outer tooth also usually present, as well as few tiny ones basally.

Etymology. The new species is named in honor of our senior colleague, Sophia K. Stebaeva, thanks to whose works the springtail fauna of southern Siberia ceased to be a continuous blank spot.

Affinities. Due to its rich dorsal chaetotaxy P. stebaevae sp. nov. is most similar to P. bescidica , described from the Polish Carpathians. Both species compared are characterized by the presence of supernumerary setae on all terga, combined with such an unusual trait as an increased number of setae in the dorsolateral parts of Th. II–III. These two species can easily be distinguished by the relative length of the buccal cone (the ratio of the labium length to the distance between postlabial setae a1 and m1 is 5.0– 5.5 in P. stebaevae sp. nov. vs, according to Smolis et al. 2023, only 3.5 in P. bescidica ), the shape of the labral edge (rounded in P. bescidica and pointed (ogival) in P. stebaevae sp. nov.), as well as the number of teeth on the mandibles (3–4 in P. bescidica , vs 6 in P. stebaevae sp. nov.) and the shape of the maxillary tip (styliform in P. bescidica vs styliform with two clear apical hooks in P. stebaevae sp. nov.). In addition, according to Smolis & Skarżyński (2007, p. 77), the distance between chaetae A and B on the labium of P. bescidica is greater than length of chaeta B, whereas this distance is much smaller than the length of seta B in P. stebaevae sp. nov. (as in Figs 9, 16 ).

Chaetotaxy of P. stebaevae sp. nov. is also comparable to that of P. plurichaetosa sp. nov. from the Caucasus. Both these species are characterized by the presence of supplementary setae on dorsal side of the body, although the latter species lacks additional setae in the dorso-lateral parts of Th. II–III and setae p2 on Abd. V. Besides this, the mandibles of P. stebaevae sp. nov. have more teeth than in P. plurichaetosa sp. nov. (6 vs 5).

Remarks.Apparently, it was P. stebaevae sp. nov. that could have been recorded from different areas of southern Siberia (Kuznetsk Ala-Tau, northeastern Altai Mountains, Tuva) as Pseudachorutes asigillatus or Pseudachorutella sp. aff. asigillata ( Stebaeva 1963, 2012). However, it appears impossible to state unequivocally that all available Siberian records of the genus belong exactly to this very new species. In fact, several congeners clearly exist in Siberia. Thus, recently, another species of the genus (two immature males) was discovered several kilometers from the type locality of P. stebaevae sp. nov. (Lake Teletskoe, vicinity of Artybash, 51.8137°N, 87.2042°E, fir forest, litter, 08.10.2020, М. Potapov & N. Kuznetsova leg.). It differs from P. stebaevae sp. nov. by the small size (0.95 mm vs up to 3.6 mm), a shorter (but also pointed) buccal cone and the complete absence of plurichaetosis (chaetotaxy of the basic type as in P. asigillata ). Apart from this, it is characterized by the presence of fairly clearly clavate tibiotarsal setae, this brings it closer to P. clavata , an European species, the real morphology of which is unfortunately practically unknown.

Figures

FIGURES 20–27. Pseudachorutella stebaevae sp. nov.: 20, dorsal chaetotaxy (holotype); 21, chaetotaxy of abdominal tip (paratype, juvenile); 22, Ant. III–IV (ventral side); 23, antenna (dorsal side); 24, maxillary apex; 25, mandible; 26, unguis and tibiotarsus, leg. 2; 27, ibid., juvenile. Scales: 20–23, 26–27, 0.1 mm, 24–25, 0.01 mm.

FIGURES 5–19. Pseudachorutella circassiana sp. nov. (5–10) and P. plurichaetosa sp. nov. (11–19): 5, antenna (ventral side); 6,Ant. III–IV (dorsal side); 7, mandible; 8, maxillary apex; 9, labium; 10, unguis and tibiotarsus of leg.2; 11, Ant. III–IV (ventral side); 12, antenna (dorsal side); 13, mandible; 14, maxillary apex; 15, labrum; 16, labium; 17, unguis and tibiotarsus of leg 2; 18, dens and mucro (dorso-lateral view); 19, ibid. (inner side); Scales: 5–6, 11–12, 17–19, 0.1 mm, 7–10, 13–16, 0.01 mm.