Oligaphorura ambigua, Babenko, Anatoly B. & Fjellberg, Arne, 2015

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 : 48

Taxon classification Animalia Collembola Onychiuridae

Oligaphorura ambigua sp. n. Figs 1-2, 3-9, 29-30

Material.

Holotype ♂, Russia, Magadan District, upper reaches of Kolyma River, Bolshoi Annachag Mt. Range, field station “Aborigen” [61°56'N, 149°40'E], mountains above station, rather dry moss/lichen in rock crevices, 1600 m alt., 23 vii 1979, A. Fjellberg leg. (MSPU).

Paratypes 6♂, 5 ♀, and 4 juveniles, same data as holotype (MSPU); 1♂, 2 ♀, and 1 juveniles, same data but moss, lichens on rock, 1650 m alt., 23 vii 1979, A. Fjellberg leg. (MSPU).

Description.

Colour white. Size of adults 0.73-0.92 mm. Body slender and elongated, Abd.3-4 clearly widened, Abd.6 short and hardly visible in dorsal view (Fig. 1), anal spines not developed (Fig. 3). Antennae about as long as head, Ant.4 not wider than Ant.3 (Fig. 5). Ant.4 with spherical subapical organite surrounded by cuticular papillae (Fig. 6), basal microsensillum present on level with proximal whorl of setae (Fig. 5). AO consisting of 4 finger-like papillae, 2 sensory rods, 2 smooth sensory clubs clearly differing in shape (Fig. 7), 5 guard setae and a lateral microsensillum (Fig. 5). Ant.1 and 2 with (8)9 and 14-15 setae respectively. PAO smaller than nearest pso, usually with 3 subequal lobes (Fig. 8). Labrum with 7 setae and 4 prelabral ones. Apical part of labium with thick terminal setae on papillae A, B and C (ABC-type), 7 long and 4 spiniform guard setae, and 6 proximal setae (Fig. 4). Basal fields of labium (mentum and submentum) with 4 and 5 setae, hypostomal complex of usual shape. Maxillary palp simple, with 2 sublobal setae.

Pseudocellar formulas (pso) as follows, dorsal: 42/133/33354, ventral: 11/000/1111, parapseudocelli (psx) invisible. Each upper subcoxa with two pso, dorsal and ventral. Localization of pso as in Figs 1-2. Granulation fine and uniform, without areas of enlarged granules. Dorsal chaetotaxy more or less symmetrical, with frequent variations even in axial parts of terga. Setae smooth and clearly differentiated, especially on abdominal tip: meso- and macrosetae straight, thick and blunt, microsetae curved and pointed, sensory setae indistinct (Fig. 1). Th.1 with 6+6 setae. Lateral ms present only on Th.2. All terga from Th.2 to Abd.3 with 3+3 axial microsetae as a rule. Unpaired dorsal seta d0 on head absent, Abd.4-5 usually with mesosetae p0, Abd.6 dorsally with 1-2 axial macrosetae. Thoracic sterna of Th.2-3 with 1+1 setae along ventral line, rarely absent on one or both sterna, ventral chaetotaxy of abdomen as in Fig. 2. Furca reduced to a small area of fine granulation situated at contact with borders of Abd.3-4 sterna, with 2+2 small posterior setae arranged in 2 rows and surrounded by several (age dependent) longer setae including two flank macrosetae in row mp (cf. Fig. 29 and Fig. 30). Ventral tube with (8)9+9 distal setae and 1(2) proximal ones at base. Upper subcoxae usually with 4-5-5, tibiotarsi with 20-21-20 setae as a rule. Distal whorl with 11 setae (7 A and 4 T-setae), whorl B with 7-7-6 setae, setae M and 1-2 setae of C-whorl present. Unguis simple, with neither inner nor lateral teeth, unguiculus without distinct basal lamella, clearly shorter than unguis (Fig. 9).

Affinities.

This new species resembles two congeners recently described from the European part of Russia, namely Oligaphorura humicola Shvejonkova & Potapov, 2011 and Oligaphorura kremenitsai Shvejonkova & Potapov, 2011. All three species lack anal spines and have no cuticular fold on the sternum of Abd.4. Apart from this, the former is characterized by a set of pso on both dorsal and ventral sides on a body, as well as on upper subcoxae identical to that in Oligaphorura ambigua sp. n., and also has no ms on Th.3 and ventral psx. Oligaphorura kremenitsai differs from both Oligaphorura ambigua and Oligaphorura humicola having more pso on Th.2-3 (42/144/33354 as a whole). Some differences like the uncommon position of anterior pso on head and submedial ones on Abd.4-5 in Oligaphorura humicola and Oligaphorura kremenitsai or their reduced tibiotarsal chaetotaxy may be a result of small body size (<0.6 mm). Nevertheless, the palp structure (ABD-type) in humicola / kremenitsai and the loss of labial papilla C probably reflects a certain genetic distance.

The presence of only four papillae in AO is also an unusual condition in the tribe, shared only with Micraphorura absoloni ( Börner, 1901), Oligaphorura palissai (Yosii, 1971) and Dimorphaphorura sophyae Weiner & Kaprus’, 2014. The clear cuticular papillae on antennal tip are also quite characteristic.

Etymology.

The name reflects the uncertain generic position of the new species.

Distribution.

Known only from the type locality, the alpine belt in the upper reaches of Kolyma river.