Philotella caeca, 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 : 543

Philotella caeca sp. nov.

Figs 44–48

Type material. Holotype: female, Khabarovsk Territory, Lazo District, mountain range «Arseniev’s granites», valley of Malyi Katen River ( Fig. 1 , point 11), ~ 900 m alt., coniferous forest belt, rotten wood, 08 July 2019. A. Brinev leg. Paratypes: 1 female, same habitat, litter; 2 females and 1 juvenile, same area but ~ 1500 m alt., Mount Arseniev , Pinus pumila belt, litter, 08 July 2019. A. Brinev leg.

Diagnosis. A colourless species of the genus Philotella characterized by coarse cuticular granulation; the absence of ocelli; an elliptic PAO with 12–15 lobes; a labrum with subequal setae; a labium of the second type; a complete dorsal chaetotaxy with p2 setae present on all terga from Th. II to Abd. IV; tibiotarsi with 19–19–18 setae, and a toothless unguis.

Description. Length (without antennae) of available specimens 0.54–0.79 mm. Habitus typical of the genus. White, without traces of dark pigment. Tegument granulation rather coarse.

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; 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 12 setae, respectively.

Ocelli absent, PAO as a wide ellipse, consisting of 12–15 vesicles ( Fig. 45 ). Buccal cone not especially short. Maxilla styliform, with two small denticles on apex, lamella not clearly seen. Mandible with usual five teeth. Labrum usually with a common set of 4/2352 setae of similar length, but abnormalities frequent. Main part of labium of the second type with three ordinary setae in triangular position and 1+1 axial setae between sensorial elements ( Fig. 46 ); submentum and mentum with usual set of four setae each. Head ventrally with 2+2 postlabial setae as usual.

Dorsal chaetotaxy complete ( Fig. 44 ). Ordinary setae short, needle-like, sensilla longer, their number as usual: 22/11111, lateral ms present on Th. II. Main characteristics: Th. II–Abd. IV with 3+3 axial setae (p2 present); dorsolateral group on Th. II–III usually consisting of four setae (a3, a4, m4 and p4) additionally to sensilla p3 set in forward position, sometimes one of them absent; Abd. I–III with p3 present, i.e. three p-setae present between axial line and sensilla; Abd. V with 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 ( Fig. 47 ). Furcal remnant in a form of two swellings, each with a seta and 2–3 tiny setules, on anterior border of Abd. IV ( Fig. 48 ). Number of setae hr on anal valves in available mature specimens unstable.

Legs 1–3 with 1, 2, 2 setae on upper subcoxae, 0, 2, 2 setae on lower subcoxae, 3, 6, 6 setae on coxae, 6, 6, 6 on trochanters, and 12, 11, 10 setae on femora. Tibiotarsi with most complete set of setae: 19, 19, 18, seta M present. Unguis toothless.

Etymology. This is the first described species of the genus without ocelli, the name reflecting this: from the Latin caecus —blind.

Remarks. In our material, there are two more undescribed forms which are characterized by the absence of a dark pigment on the body. One of them, from the Amur Region (Zeya State Nature Reserve, Fig. 1 , point 1), like P. caeca sp. nov., lacks ocelli, but distinguished by rounded PAO with a smaller number of lobes, a posterior position of sensilla in dorsolateral groups on Th. II–III (i.e., p4 setae absent), and shortened and slightly widened sensilla on Abd. IV. The second one from Southern Primorye ( Fig. 1 , point 5) has 3+3 small and uncoloured ocelli, and its dorsal and ventral chaetotaxy is almost identical to that of P. caeca sp. nov. Most likely, these specimens represent distinct species, but the shortage of material does not allow us to describe them.

Affinities. The species possesses all diagnostic features of the genus Philotella , but lacks ocelli. This combination of characters is not known among the described species of the genus, although Najt & Weiner (1997) mentioned the existence of a similar form in New Caledonia.

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 44–48. Philotella caeca sp. nov.: 44, dorsal chaetotaxy; 45, ocular field and PAO; 46, labium; 47, ventral chaetotaxy of abdomen; 48, furcal remnant. Scales. Figs 44, 47: 0.1 mm; 45–48: 0.01 mm.