Micraphorura alnus (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 : 52-53

Taxon classification Animalia Collembola Onychiuridae

Micraphorura alnus (Fjellberg, 1987) comb. n.

Onychiurus (Archaphorura) alnus Fjellberg, 1987: 282.

Dimorphaphorura alna (Fjellberg): www.collembola.org

Dimorphaphorura alnus (Fjellberg): Weiner and Kaprus’ 2014: 6.

Material.

holotype, ♀, " USSR, Magadan Reg., Aborigen [field station, 61°56'N, 149°40'E], deep, moist Pinus pumila litter, 27 vii 1979" (CNC 165044, type No 20108); Paratypes, 5 ♀, same sample (CNC 165130, type No 20111); 1 ♀, same region, " Alnus litter in dense thickets, 25 vii 1979" (CNC 165129, type No 20110), all A. Fjellberg leg.; 9 specimens (in bad condition), "USSR, Chukotka, Chaun Bay [68°44'N, 170°36'E], Sept. 1975" (CNC 165128, type No 20109), S.F. MacLean leg.

Additional material.

1 ♂, Magadan District, Bolshoi Annachag Mts. Range, upper reaches of Kolyma River, field station “Aborigen”, valley bottom near station, moss and litter of Larix / Pinus on slope, 25 vii 1979, A. Fjellberg leg.; 5♀ and 3♂, same region, deep moist litter in thickets of Pinus pumila , 1200 m alt., 27 vii 1979, A. Fjellberg leg.; 2 ♂, same region, stand of Pinus pumila , Betula , Larix dahurica , and Alnus fruticosa , 24 vii 1979, V. Behan 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 almost straight, external much larger and bent), 5 guard setae and a lateral microsensillum which is set below the organ. Ant.1 with 8 setae, Ant. 2 with (12)13 setae. PAO with 3-4 lobes, slightly longer than nearest pseudocellus. Labrum with 4/3-2-2 setae. Apical part of labium with thick terminal setae on papillae A and C, 6 long guard setae and 6 proximal setae present, basal fields with 4+5 setae. Maxillary palp simple with two sublobal hairs.

Pseudocellar formula (pso) as follows, dorsal: 32/133/33343, ventral: 2/000/0001, parapseudocelli (psx) invisible. Each subcoxa with one pso, psx absent. Granulation rather coarse, especially around pseudocelli and on Abd.6. Dorsal chaetotaxy almost symmetrical, setae smooth and fine, macrosetae poorly differentiated, sensory setae (2/011/222211) more or less distinct, Th.1 usually with 6+6 setae, Th.2-3 with lateral ms, p1 on head and Th.2-3 almost on level with other medial p-setae. Abd.5 with m1 longer than a1, subequal to p1. Unpaired setae: d0 and axial seta on Abd.5 absent, Abd.6 with two axial setae, a0 subequal to a2. Thoracic sterna with 0-1(2)-1(2-3) setae on each side of ventral line. Upper subcoxae usually with 3-3-4 setae. Furca as a small area with fine granulation in middle section of sternum of Abd.4, some setae present on sternum anteriorly to furcal remnant. In juveniles manubrial field with usual 3+3 proximal q- setae and 2+2 distal ones set in a row, in adults some additional setae sometimes present, especially in large specimens (Fig. 33). Ventral tube with (5)6+6 distal and (1)2 proximal setae at base. Subcoxae with 3-(3)4-(3)4 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 clear basal lamella, about 3/4 as long as unguis. Anal spine bent, rather thick and constricted at base, set without papillae. Males present.

Remarks.

The redescription completely matches the original one, although Fjellberg (1987) did not mentioned ventral pso on Abd.4. The species was recently redescribed by Weiner and Kaprus’ (2014). The only clear difference with this description is the number of labral setae which states as being full (4/3-4-2). The authors treat the species as Dimorphaphorura because their specimens had no secondary setae in the manubrial field (only 5+5 setae in all). In the largest specimens from Magadan the manubrial field has several additional mm-setae (the holotype has 14 setae on the manubrial field in total) which illustrates the weak distinction between Dimorphaphorura and Micraphorura .

The set of dorsal pseudocelli displayed by Micraphorura alnus is shared with several other species in the genus. Among these only four species have ventral pso present on Abd.4, i.e. Micraphorura alnus , Micraphorura pieninensis Weiner, 1988, Dimorphaphorura irinae (Thibaud & Taraschuk, 1997), and Dimorphaphorura olenae . Micraphorura pieninensis differs from both other species in having no ms on Th.3. Dimorphaphorura irinae can be distinguished by the reduced tibiotarsal chaetotaxy (only 2 T-setae present), a full number of labral setae (4/9) and different labial type (ABC) ( Weiner and Kaprus’ 2014). Dimorphaphorura olenae possesses ventral pso on all sterna from Abd.1 to Abd.4, and two pso on subcoxae of leg.2-3.