Oligaphorura nataliae (Fjellberg, 1987) Fjellberg, 1987

Babenko, Anatoly B. & Fjellberg, Arne, 2015, Subdivision of the tribe Oligaphorurini in the light of new and lesser known species from North-East Russia (Collembola, Onychiuridae, Onychiurinae), ZooKeys 488, pp. 47-75 : 51-52

Taxon classification Animalia Collembola Onychiuridae

Oligaphorura nataliae (Fjellberg, 1987) comb. n.

Onychiurus (Archaphorura) nataliae Fjellberg, 1987: 281.

Micraphorura nataliae (Fjellberg): www.collembola.org

Material.

holotype, ♂, "USSR, Chukotka, Chaun Bay [68°44'N, 170°36'E], upland heath, soil, 13.viii 1977" (CNC 165046, type No 20114); paratypes: 1 juv. same data (CNC 165136, type No 20113); 3♀, same place, Loc. S-1, Sept. 1975 (CNC 165135, type No 20112), all S.F. MacLean leg.

Additional material.

15 specimens, Russia, Novosibirsk Islands, Kotel’nyi, Balyktakh river [75°03'N, 140°10'E], various habitats, vii 1994, A. Babenko leg.

Redescription.

Colour white. Size 0.8-0.9 mm. Body shape cylindrical. Antennae about as long as head, Ant.3-4 broad, club-like. Ant.4 with subapical organite and microsensillum located in proximal row of setae. AO consists of 5 long and thin papillae, two sensory rods, two granulated sensory clubs (internal straight, external much bigger and bent), 5 guard setae, and a lateral microsensillum which is set below the organ. Ant.1 and 2 with 8 and 14-15 setae, respectively. PAO with 3-4 lobes, slightly longer than nearest pseudocellus. Labrum with 4/5-2-2 setae but variations also seen. Apical part of labium with thick terminal setae on papillae A and C, usually complete number of long guard setae (7) and 4 spiniform ones, 6 proximal setae present. Basal fields of labium with 4+5(6) setae. Maxillary palp simple with two sublobal hairs. Maxillae not modified.

Pseudocellar formula (pso) as follows, dorsal: 32/033/33343, ventral: 2/000/0000, parapseudocelli (psx) invisible. Each subcoxa with one pso, psx invisible (absent?). Granulation fine, clearly coarser around pseudocelli on all segments. Dorsal chaetotaxy almost symmetrical, setae smooth, macrosetae clearly differentiated only on abdominal tip, sensory setae indistinct. Th.1 with (5)6+6 setae. Lateral ms present only on Th.2. On head p1 clearly above p2, its position on Th.2-Abd.3 rather variable but usually more or less at a level with p2. Abd.1-3 with setae p4 present as a rule. Abd.5 with m1 curved, thinner and shorter than the straight a1 and p1, the latter usually shorter than anterior macrosetae a1. Unpaired setae: d0 absent, Abd.5 often with seta p0 present, Abd.6 with two axial macrosetae, a0 clearly shorter than a2. Thoracic sterna with 0, 1+1, 1+1 setae. Furca as small cuticular furrow in some distance from anterior border of sternum. Chaetotaxy of furcal field in juveniles as in Fig. 32: usual 3+3 proximal q-setae and 3+3 setae set in triangle below furrow; adults with few (1-2) additional setae in front of q-row (Fig. 31). Ventral tube usually with 6+6 distal and 2(1) proximal setae at base. Subcoxae with 3-5-(4)5 setae, tibiotarsi with 20-20-19 setae: each distal whorl (A+T) with 11 setae, whorl B with 7-7-6 setae, setae M and Y present on all tibiotarsi. Unguis simple, without inner or lateral teeth, unguiculus with small basal lamella, about 3/4 as long as unguis. Anal spines rather long and thin, almost straight and hardly constricted at base, set without papillae. Males present.

Remarks.

Originally described as Onychiurus (Archaphorura) nataliae , the species is now listed under Micraphorura on www.collembola.org. Nevertheless the chaetotaxy of the manubrial field in juveniles of this species is identical with that found in northern parthenogenetic populations of Oligaphorura groenlandica (Tullberg, 1876) (cf. Fig. 32 and Fig. 18). Adults usually have a pattern with four setal rows behind the cuticular furrow (Fig. 31), which considered being typical for Oligaphorura .

In the interactive key on www.collembola.org the species keys out with Oligaphorura interrupta ( Micraphorura on www.collembola.org) which can easily be distinguished by higher number of abdominal pso, presence of ms on Th.3 and absence of ventral setae on Th.2.

Five known species of the tribe possess the same number of dorsal and ventral pseudocelli as nataliae, i.e. Oligaphorura pingicola (Fjellberg, 1987), Oligaphorura koreana (Weiner, 1994), Dimorphaphorura raxensis (Gisin, 1961), Dimorphaphorura chatyrdagi ( Kaprus’, Weiner & Pomorski, 2002), and Dimorphaphorura sanjiangensis Sun & Wu, 2012. Oligaphorura nataliae differs from the above Oligaphorura species ( Oligaphorura pingicola and Oligaphorura koreana ) in having no ms on Th.3. Dimorphaphorura raxensis according to Weiner and Kaprus’ (2014) has 9 distal setae on tibiotarsi and ABC type of labium. Dimorphaphorura chatyrdagi can easily be distinguished due to strongly reduced tibiotarsal chaetotaxy (with 5 distal setae) and the presence of ms on Th.3. Dimorphaphorura sanjiangensis , recently described from northern China, can be separated from Oligaphorura nataliae due to different type of labium (A versus AC in Oligaphorura nataliae ), the presence of psx on abdominal sterna (0/000/122201+1m), and identical number of tibiotarsal setae on all legs (20-20-20) which is very characteristic if it is correct. Apart of this, all three species of Dimorphaphorura should have no more than 5+5 setae in the manubrial field whereas even first instars of Oligaphorura nataliae possess 6+6 setae.

The presence of 7 long guard setae of labium in such small species as Oligaphorura nataliae is an uncommon character in the tribe and needs additional confirmation being seen in few specimens. Only five other Asiatic species, Dimorphaphorura sanjiangensis , Micraphorura changbaiensis Sun & Wu, 2012, Oligaphorura aborigensis (Fjellberg, 1987) and the two new Oligaphorura species described above, share this character with Oligaphorura nataliae whereas 18 species of the tribe are known as having only 6 long guards.