Psyllaphorura pseudopodis, Shveenkova & Babenko, 2021

Shveenkova, Yulia B. & Babenko, Anatoly B., 2021, Two new species of the genus Psyllaphorura (Collembola: Onychiuridae) from the east of European Russia, Zootaxa 4965 (1), pp. 114-128 : 117-120

Psyllaphorura pseudopodis sp. nov.

Figs 11–19

Type material. Russia: holotype, female, European part, Middle Volga River Basin, Penza Region, “Privolzhskaya Lesostep” State Nature Reserve , middle reaches of Kadada River , near Shatkino settlement, Alnus glutinosa floodplain forest [N 52.9322°, E 46.3022°], soil, 15.09.2017, Yu. Shveenkova leg. Paratypes: 4 males and 5 females, same data as holotype; 1 male, ibid., but 10.10.19; 1 female, ibid., but 18.09.20, Yu. Shveenkova leg. The types are kept in the collection of MSPU .

Diagnosis. A species of the genus Psyllaphorura , which can be distinguished from the congeners due to the presence of 30/000/00003 dorsal pso (3+3 cephalic pso are located as a common axial group on the median part of the head), only 2+2 dental setae and a pair of ventral swellings on Abd. IV. It is also characterized by coarse dorsal granulation, rather distinct dorsal sensilla, AO with 5 papillae and 4 guard setae, PAO with 12–15 simple vesicles, labium of AC - type, the presence of lateral ms on both Th. II–III, rather short unguiculus and the absence of retinaculum.

Description. Size: 1.0– 1.2 mm in females, 0.87–0.97 mm in males, holotype: 1.06 mm. Colour white. Habitus typical of the genus ( Fig. 11 ), body ovoid with a short Abd. VI armed by small anal spines. Cuticular granulation very coarse, especially in middle parts of terga, with 8–9 cuticular granules around each abdominal pso and only 5–6 granules between p1 setae on Abd. V.

Dorsal pseudocelli as 30/000/00003, 3+3 cephalic pseudocelli located on head front in the form of a single “Vshaped” complex ( Fig. 11 ). Psx invisible.

Antennae club-like, distinctly shorter than head diagonal. Small area of antennal bases clearly marked with finer granulation. Ant. IV with small, peg-like subapical organite, 3 curved blunt sensilla laterally and up to 8 sensilla on its inner side, basolateral microsensillum present in line with proximal whorl of setae ( Fig. 13 ). AIIIO typical, with 5 cuticular papillae, 4 guard setae, two sensory rods, two smooth sensory clubs and lateral microsensillum ( Fig. 13 ). Ant. I–II with 10 and 13–14 setae, respectively. PAO with 12–15 simple vesicles. Labrum with 4/9 setae ( Fig. 17 ), maxillary outer lobe simple with two sublobal setae. Labium of AC type (sensillum on papilla A clearly thicker) with 7 long and 4 spiniform guards and 6 proximal setae ( Fig. 16 ). Basomedian and basolateral fields of labium with 4 and 6 setae, respectively. Usually 4+4 postlabial setae present along ventral midline ( Fig. 12 ).

Chaetotaxy plurichaetotic and usually not symmetrical, dorsal setae weakly differentiated ( Fig. 11 ). Most dorsal sensilla relatively distinct, but masked by coarse granulations, 2/021/221121(0) in number, sensilla on Abd. VI, if present, located ventro-laterally on pleura. The presence/absence of dorsal seta d0 on head often obscure due to chaetotic asymmetry. Th. I with up to 17 setae on each side set in two irregular rows. Both Th. II and Th. III with lateral microsensillum. Upper subcoxae prominent on all legs with up to 10 setae. Chaetotaxy of Abd. IV very plurichaetotic, axial m-setae present or absent. Abd. V with seta p0. Axial seta a0 on Abd. VI about as long as p1 and a2 setae, seta a1 shorter than a2 (~0.7: 1). Sterna of Th. I–III without setae along ventral line. Ventral chaetom on abdomen composed of pointed meso- and macrosetae ( Fig. 14 ).

Furcal remnant without mucro, dens knob-like with 2+2 long setae, retinaculum absent. Chaetotaxy of furcal field in adults highly variable and usually not symmetric: in largest specimens 2–3 irregular rows of manubrial setae present posterior to dental remnant. VT with 7(8) distal setae on each side and without proximal setae at base. Sternum of Abd. IV on each side of furcal remnant with two specific protuberances covered with modified (long and thin) cuticular granules ( Figs. 14 , 18, 19 ). Tibiotarsi with a complete distal whorl (7A+4T), 7–7–6 setae in B - whorl, M seta present, C-whorl variable. Unguis toothless, unguiculus about as long as half of inner edge of unguis ( Fig. 15 ). Upper anal valve with setae a0, 2a1, 2a2, 2b1, c0, 2c1, 2c2, each of lateral valve with setae a0 and 2a1 ( Fig. 14 ). AS short and conical, about as long as papillae.

Etymology. The species name is derived from the unique ventral swellings located on the fourth abdominal segment, which is somewhat reminiscent of pseudopodia.

Affinities. In having 3+3 cephalic pso arranged in a single group on the median part of the head, Psyllaphorura pseudopodis sp. nov. is the most similar to P. altaica , which has recently been described from southern Siberia. P. pseudopodis sp. nov. can be easily distinguished from the latter species by the absence of pso on Abd. IV ( P. altaica has 00013 abdominal pso), only 2+2 dental setae (vs 3+3 setae in P. altaica ) and a shorter unguiculus (~ 0.5–0.6 UIII vs 0.8 UIII in P. altaica ).

The only other congener with not 3+3, but 2+2 setae on the furcal knobs as in P. pseudopodis sp. nov., is P. bashkirica ( Khanislamova, 1986) , described from a more easterly region (at a distance of ~ 700 km). Although the description of the latter species does not fully correspond to modern standards and clearly requires verification, its conspecificity with the new species is unlikely. These species clearly differ by the number of dorsal pso (5/000/00023 in P. bashkirica vs 3/000/00003 pso in the new species), structure of PAO (15–17 divided vesicles in P. bashkirica vs 12–15 simple vesicles in P. pseudopodis sp. nov.), the number of dorsal sensilla (?/?11/11112?, sensilla on Th. III in medial position in P. bashkirica vs 2/021/221120(1), sensilla on Th. III in lateral position in the new species) and guard setae in AIIIO (5 setae in P. bashkirica vs 4 setae in P. pseudopodis sp. nov.).

P. pseudopodis sp. nov. is also characterized by one unique feature, namely the development of a pair of ventral swellings on the fourth abdominal segment, which seem to have never been observed in any other species of Collembola. These swellings are covered with modified cuticular granules, representing a structure of unknown origin with a duct system or a hole inside visible under them.

Distribution and ecology. The species has only been registered at the type locality.

Figures

FIGURES 11–14. Psyllaphorura pseudopodis sp. nov.: 11, dorsal chaetotaxy; 12, ventral chaetotaxy of head; 13, antenna, different views; 14, ventral chaetotaxy of abdomen. Scales: Figs 11, 12, 14—0.1 mm; 13—0.5 mm.

FIGURES 15–22. Psyllaphorura pseudopodis sp. nov.: (15–19), P. altaica (20–22): 15, tip of leg III; 16, labial palp (small guards not shown); 17, labrum; 18, ventral swelling (lateral view); 19, sterna of Abd. III-IV (lateral parts) with ventral swelling and furca; 20, subcoxae of legs II, III; 21, subcoxa of leg III (dorsal view); 22, subcoxa of leg III (lateral view). Scales: Figs 15, 18, 19—0.05 mm; 16, 17—0.025 mm; 20–22—0.5 mm.