Paranura reducta Smolis & Deharveng, 2015, sp. nov.

Paranura reducta sp. nov.

Figs 28–37, Tables 5–6

Etymology. The name of the species refers to the strong reduction of its labral chaetotaxy.

Diagnosis. Body white. 3+3 eyes on head. Tubercles and reticulations not developed. Head with chaetae O, A and E. Head with three ocular chaetae. Thorax I with 2 chaetae De. Thorax II–III with 3 chaetae Di. Thorax II–III with 3 and 4 ordinary chaetae De respectively. Abdomen V with 2+2 chaetae Di. Abdomen V slightly longer than VI. Abdomen without clavate chaetae. Furca rudimentary with microchaetae. Male ventral organ present. Tibiotarsi with chaetae M.

Description. Habitus typical for Paranura Axelson, 1902 genus. Buccal cone slightly elongated. Body length (without antennae) 0.8–1.7 mm (holotype: 1.05 mm). Colour of body when alive and in alcohol white. Tubercles not detected. Ordinary dorsal chaetae (Figs 28, 37) differentiated into short, thin, acuminate microchaetae, medium size, smooth, acuminate mesochaetae and long, nearly smooth (with denticles visible under large magnification, Fig. 37), relatively thick, acuminate macrochaetae Ml and Mc. No plurichaetosis on body.

Head. Antennae distinctly shorter than head (Fig. 28). S-chaetae of ant. IV relatively short and thick, S1 and S2 slightly thinner and smaller than others (Fig. 28). Apical bulb distinct and trilobed (Fig. 30). Chaetotaxy of antennae as in Fig. 31 and Tab. 5. Buccal cone relatively long and rounded at apex (Figs 29, 33). Maxilla needlelike, mandible tridentate. Chaetotaxy of labium as in Fig. 32, labial papillae x absent. Labrum chaetotaxy 0/2,2 (Fig. 29). Group Vi with 6+6 chaetae (Fig. 32). Groups Vea, Vem and Vep with 3–4, 4 and 4 chaetae respectively. Dorsal chaetotaxy of head as in Tab. 5. and Fig. 28. Dorsal chaetotaxy of central area on head complete, with 3 chaetae Oc and chaetae A, B, C, D, E, F, G, O. Line of chaetae Di2–De2 crosses line Di1–De1 on head (cross-type, Deharveng 1983). 3+3 relatively large eyes, their diameter about three times as large as the diameter of chaeta Ocm socket (Fig. 28), pigmented in black.

Thorax, abdomen, legs. Dorsal chaetotaxy as in Fig. 28 and in Tab. 6. Ventral chaetotaxy as in Tab. 6 and Figs 34, 35. S-chaetae long, nearly equal to nearby macrochaetae (Figs 28, 36). S-chaetae formula of body: 022/11111, s-microchaeta on Dl of th. II present. Furcal remnant with 4–6 mesochaetae and 6 minute microchaetae (without chaetopores and visible only under magnification 1000x, Fig. 34). Male with thick and forked chaetae in groups Ag (abd. V) and Ve (abd. VI) (“ventral male organ”). Claw without internal tooth. Chaeta M present on tibiotarsus, chaetae B4 and B5 short. Chaetotaxy of legs as in Tab. 6.

Types. Holotype: male on slide, United States of America: Oregon, Blue River Ranger District of Willamette National Forest, neighborhood of H. J. Andrews Experimental Forest, 7 km North–East of Blue River town, c. 500–650 m above sea level, “Mona Creek” site, valley of Mona Creek, coniferous forest of Tsuga heterophylla Zone, ex decayed log, 26.IX.2006, leg. A. Smolis. Holotype deposited in DIBEC. Paratypes: 5 females, 2 males and juvenile on slides, same data as holotype. Three paratypes (2 females and male) are housed in MNHN, the others in DIBEC.

Other material. Female on slide (DIBEC), USA: Oregon, Blue River Ranger District of Willamette National Forest, neighborhood of H. J. Andrews Experimental Forest, 6.5 km East of Blue River town, c. 520–550 m above sea level, “Cougar 1” site, old-growth forest of Tsuga heterophylla Zone, ex decayed log, 27.IX.2006, leg. A. Smolis; numerous specimens on slides and in alcohol, 18 km North of McKenzie Bridge town, c. 1450 m above sea level, “Wild cat” site, old-growth forest of Abies amabilis Zone, ex decayed logs, 4.X.2006, 9.VI. 2009, leg. A. Smolis.

Remarks. The new species is most similar to Paranura mjohjangensis Deharveng & Weiner, 1984 (from North Korea) and P. oregonensis sp. nov., resembling them in having the complete chaetotaxy of central area of head and the same number of eyes, ocular chaetae and chaetae Di on abdomen V. Among these species, Paranura reducta sp. nov. is most diagnostically recognized by labral chaetotaxy, with only 4 chaetae (0/2,2; in mjohjangensis, 4/5,4; in P. oregonensis sp. nov. 4/2, 4). Other characters, in combination, that allow to distinguish P. re d uc t a sp. nov. from these species are: the number of labial lateral chaetae (in P. reducta sp. nov. and P. oregonensis sp. nov. 3 chaetae, in mjohjangensis 4 Fig. 59), number of ordinary chaetae De on abdomen IV (in P. reducta sp. nov. and mjohjangensis 2 chaetae, in P. oregonensis sp. nov. 1 chaeta), microchaetae on furcal remnant (in P. reducta sp. nov. and P. oregonensis sp. nov. present, in mjohjangensis absent). Considering the last character should be mentioned that microchaetae in P. reduct a sp. nov. are very minute and can be overlooked (Figs 34, 35).

a) Cephalic chaetotaxy––dorsal side.

b) Chaetotaxy of antennae.

Terga Legs

Di De Dl L Scx2 Cx Tr Fe TT th. I 1 2 1 – 0 3 6 13 19 th. II 3 3+s 3+s+ms 3 2 7 6 12 19 th. III 3 4+s 3+ s 3 2 8 6 11 18

Sterna

abd. I 2 3+ s 2 3 VT: 4

abd. II 2 3+ s 2 3 Ve: 5; Vel present

abd. III 2 3+ s 2 4 Ve: 4–5; Fu: 4–6 me, 6 mi

abd. IV 2 2+ s 3 7 –10 Vel: 4; Vec: 2; Vei: 2; Vl: 4

abd. V 2 5–6+s Ag: 3; chaetae L‘ and Vl present abd. VI 7 Ve: 12–14; An: 2 mi

Several characters: the presence of 3+3 eyes, the complete chaetotaxy of central head area, labral chaetotaxy 0/ 2,2, tubercle De of th. III with 5 chaetae and tubercle Di of abdomen with 2+2 chaetae, and rather unusual habitat of the new species (dead coniferous logs) are suggestive of close relationships with P. sitchensis Fjellberg, 1985 (described from Alaska and known also from Vancouver Island, Fjellberg 1985). However, both species are readily distinguished by the following features: the clavate chaetae on two last abdominal segments (absent in P. re du c t a sp. nov., present in sitchensis), colour of the body (white in P. reducta sp. nov., bluish-gray in sitchensis), the length of tibiotarsal chaetae B4 and B5 (short in P. reducta sp. nov., long in sitchensis) and number of lateral labial chaetae (three in P. reducta sp. nov., four in sitchensis). Considering the differences between both species it should be mentioned that there are only two described species of Paranura with clavate chaetae on abdominal segments V and VI, the mentioned P. sitchensis and P. clavisetis (Axelson, 1902) described from Finland (Europe) and later considered by different authors as a junior synonym of P. sexpunctata.

Biology. The species is resident in lower and upper montane (from 500 to 1400 m) conifer forests of both Tsuga heterophylla (Fig. 38) and Abies amabilis Zones (Franklin & Dyreness, 1988). It can be treated as a truly saproxylic species (according to Speight’s definition, Speight 1989) as it was found only in coarse woody debris of coniferous tree species: Douglas fir Pseudotsuga menziessi, western hemlock Tsuga heterophylla and noble fir Abies amabilis. Despite intensive field investigations it was not collected from dead wood of deciduous trees and litter/soil samples.