Jacekaphorura furcata Babenko, 2013, sp. nov.

Jacekaphorura furcata sp. nov.

Figs 6–15

Type material. Holotype, female, Russia, Magadan District, Bolshoi Annachag Mts. Range, upper reaches of Kolyma River, field station “Aborigen” 61°56′ N 149°40′ E, moss and Larix /Pinus litter on slope down to stream, 25.vii.1979, A. Fjellberg leg. Paratypes, 22 specimens, same sample as holotype; male and juvenile, same area, slope with Dahurian larch (Larix gmelinii) down from ridge to boggy area close to aufeis, litter, 25.vii.1979, V. Behan leg.; 3 juvenile females, same area, Olen’ River, north-facing slope, moss/lichen cover, 23.viii.2006, A. Alfimov leg.

Description. Length up to 1.3 mm. Colour white. Body shape cylindrical, abdominal tip clearly broadened, Abd. VI small, poorly separated from and almost completely hidden under Abd. V (Fig. 6).

Antennae thin, clearly longer than head. Ant. IV with spherical subapical organite and microsensillum set slightly above proximal whorl of chaetae (Figs 12). AO consisting of 5 long and narrow papillae, two smooth sensory rods, two granulated sensory clubs slightly differing in size and granulation, 5 guard chaetae, and lateral microsensillum (Figs 12–13). Ant. IV and II with 11–12 and 22–25 chaetae, respectively. PAO long with 32–39 simple vesicles (Fig. 14), abnormal variation rather frequent and specimens completely lack PAO or with only few lobes on one or both sides are seen. Labrum with 9 chaetae and 4 prelabral ones. Labium of A-type, with all 5 usual papillae (A–E), 7 long and 4 spiniform guards, and 6 proximal chaetae. Basal fields with 4+6 chaetae. Maxillary palp simple with two sublobal hairs.

Dorsal pso formula as 32/133/33333, anterior pso on head set close together in a form of triangle, medial hind pseudocellus on head moved slightly forward (Fig. 6). Number of ventral pso 2/000/0111, ventral pso on head in usual position: medial and postero-lateral; ventral pso on abdomen as Fig. 10. Parapseudocelli (psx) are seen only on inner side of femora and sometimes on antennae laterally to AO. Upper subcoxae with 1–1–1 pso, psx invisible.

Granulation fine and more or less uniform with slightly enlarge granules around pso. Dorsal chaetotaxy more or less symmetrical, chaetae clearly differentiated into macro-, meso- and microchaetae, especially laterally and on abdominal tip (Fig. 6, 10), most macro- and mesochaetae truncate. Th. I with usually with 9+9 chaetae, whole range in adults 6–9 on each side. Both Th. II and Th. III with lateral microsensilla. Unpaired dorsal chaeta d0 on head absent, Abd. V with one or two unpaired axial mesochaetae, Abd. VI with a0 (usually absent in juveniles) clearly shorter than a2. Thorax without chaetae along linea ventralis.

Sternum of Abd.4 with prominent cuticular fold near anterior border with 2+2 chaetae set on it by pairs in a line. In mature males these chaetae clearly modified (Figs 7–8). Chaetotaxy of manubrial field in juveniles as on Fig. 9 with 1+1 intermediate chaetae between dental row and 3+3 q-chaetae. Adults with few secondary chaetae (Fig. 8). VT with 8–10 distal chaetae on each flap, frontal and proximal chaetae at corpus base absent, in mature males some distal chaetae slightly thickened and longer than in females. Upper subcoxae usually with 5, 6, 5(6) chaetae, Ti. I–III with 24, 25, 23 chaetae as a rule: distal row complete with 11 chaetae (7A + 4T), 7, 7, 6 chaetae in B-whorl, M chaeta present on all tibiotarsi, and 5, 6, 5 chaetae in proximal C-whorl. Unguis usually with small tooth in proximal part of inner edge, lateral ones invisible, unguiculus with distinct but not wide lamella, slightly shorter than inner edge of unguis (Fig. 15). Anal spines absent.

Affinities. As it was pointed above J. furcata sp. nov. occupies an isolated position within the genus, although there are only three characters which differ it from the type species of the genus, viz. less number of chaetae due to smaller size, the presence of cuticular fold on Abd. IV sternum, and only one pso on each subcoxa. On the other hand, a high similarity in pso distribution (see below) may testify its close relation to other species of the genus.

Etymology. Named after the presence of cuticular fold, the most characteristic feature of the new species.