Philotella alba, 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 : 539

Philotella alba sp. nov.

Figs 31–37

Type material: Holotype: immature male, Khabarovsk Territory, Komsomolsk State Nature Reserve, Anyuinski National Park , Anyui River ( Fig. 1 , point 14), mixed coniferous-broadleaf forest, 49°21.81’N, 137°42.14’E, ~ 200 m alt., litter, 08. July 2018. N. Kuznetsova, A. Kuprin & A. Geraskina leg. Paratypes: 2 females, 3 immature males and 6 juveniles, same data as holotype ; 1 female, 1 male and 3 juvenile, same region and National Park , Tormasu River ( Fig. 1 , point 13), mixed coniferous-broadleaf forest, 49°18.2’N 137°34.2’E, ~ 200 m alt., litter, 07 August 2018. N. Kuznetsova, A. Kuprin & A. Geraskina leg.

Additional material. 3 females and 1 male, Khabarovsk Territory, Lazo District, mountain range «Arseniev’s granites»( Fig. 1 , point 11), valley of Malyi Katen River , 500-600 m alt., mixed forest, litter, 08 July 2019. A. Brinev leg. ; 1 immature male, same region, upper reaches of Katen River, Ko Mountains ( Fig. 1 , point 10), ~ 500 m alt., mixed forest, litter, 01 July 2018. All A. Brinev leg.

Diagnosis. A colourless species of the genus Philotella characterized by: the presence of 2–3 ocelli on each side of the head; the labral setae in the second row similar in length; a labium of the second type; dorsal chaetotaxy with p2 present on Th. II–III but absent on Abd. I–V; three ordinary setae (a3, a4 and m4) in dorsolateral group on Th. II–III and usually two setae (a3 and p3) between axial group and sensilla p4 on Abd. I–III; a strongly thickened sensilla p6 on Th. II and p4 on Abd.4; a complete tibiotarsal chaetotaxy, and toothless unguis.

Description. Length (without antennae) of mature specimens 0.34–0.49 mm. Uncoloured, ocular fields sometimes with few granules of dark pigment. Tegument granulation moderate, not especially coarse.

Antennae clearly shorter than head, Ant. III–IV fused dorsally, ventral separation more or less clear. Ant.4 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. Antennal organ of Ant.3 typical, inner sensilla small, sgv longer than sgd and curved, ventral ms present. Ant. I–II with 7 and 11 setae, respectively.

Head with 2+2 or 3+3 small ocelli, clearly larger than secondary granules on ocular field ( Figs 32–33 ). PAO usually rounded, more rarely slightly elliptic, consisting of 8–10 vesicles, its axis to ocellus B ratio as 2.0–2.2: 1 ( Figs 32–33 ). Buccal cone short and blunt. Maxilla styliform with two small apical denticles, lamellae not clearly seen. Mandible typical, with five teeth along cutting edge. Labrum with a common set of 4/2352 setae of more or less similar length ( Fig. 35 ). Main part of labium of the second type with three ordinary setae in triangular position and 1+1 axial setae between sensorial elements ( Fig. 36 ); submentum and mentum with usual set of four setae each, i.e. 4+4. Head with 2+2 postlabial setae along ventral line as usual.

Dorsal chaetotaxy usually symmetrical and rather reduced ( Fig. 31 ). Ordinary setae short, needle-like, sensilla longer, their number as usual: 22/11111, lateral ms present on Th. II. Main characteristics: sensilla on Abd. IV and lateral sensilla on Th. II short and thick ( Figs 31, 34 ); Th. II–III with 3+3 axial setae (p2 present) and three setae (a3, a4 and m4) additionally to sensilla p 3 in dorsolateral position; Abd. I–III with 2+2 axial setae (p2 absent) and two setae (a3 and p3) between axial group and sensilla; Abd. IV and Abd. V with only 2+2 axial 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. Furcal remnant in a form of two swellings, each with a seta, on anterior border of Abd. IV ( Fig. 37 ). Number of hr-setae on anal valves variable, probably depended on age.

Legs 1–3 with 1, 2, 2 setae on upper subcoxae, 0, 2, 2 setae on lower subcoxae, 3, 6, 7 setae on coxae, 6, 6, 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. In specimens from the type series 3+3 uncolored eyes can be seen, as a rule; traces of dark pigment on the ocular fields are less often observed. All specimens from more southern region ( Fig. 1 , points 10 and 11) have only 2+2 ocelli, which are clearly distinguished by the dark pigment. Otherwise, these individuals are identical to those from the type series.

Etymology. The name of the new species reflects one of its characteristic features—the almost complete absence of dark pigment.

Affinities. Philotella alba sp. nov. is difficult to compare to the known species of the genus as the main diagnostic features (sensorial equipment of the antennae, labrum and labium, maxillae and mandibles, ventral chaetotaxy) are not unique compared to other species of the genus. Its dorsal chaetotaxy with the presence of setae p2 only on the thoracic terga is also rather usual, being almost identical to that in P. miracli , P. aliniensis sp. nov., and P. amurica sp. nov. Nevertheless, there is one characteristic feature of the new species, i.e. a significant modification of the sensilla on Th. II and Abd. IV, which makes P. alba sp. nov. undoubtedly distinguished from all known species of the genus. A similar modification of the same sensilla is known for a number of species of Micranurida and Anurida Laboulbène, 1865 , which can probably be considered as another piece of evidence of the existing generic classification of this part of Pseudachorutinae being artificial.

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 31–37. Philotella alba sp. nov.: 31, dorsal chaetotaxy; 32–33, ocular field and PAO (two different specimens; 34, lateral sensillum of Th. II; 35, labrum; 36, labium; 37, ventral chaetotaxy of abdomen. Scales. Figs 31, 37: 0.1 mm; 32–36: 0.01 mm.