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

Paranura microchaetosa sp. nov.

Figs 48–55, Tables 9–10

Etymology. The name of the species refers to the presence of distinct microchaetae on furcal remnant.

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 12 18 th. II 3 3+s 3+s+ms 3 2 7 6 11 18 th. III 3 4+s 3+ s 3 2 7 –8 6 10 17

Sterna

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

abd. II 2 3+ s 2 3 Ve: 4; Vel present

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

abd. IV 2 1+ s 3 7 –8 Vel: 4; Vec: 2 Vei: 1–2; Vl: 4

abd. V (2+2) 6+s Ag: 3; chaetae L‘ and Vl present

abd. VI 5–6 Ve: 10–11; An: 1 mi

Diagnosis. Body white. 2+2 eyes on head. Tubercles developed on dorsal side of abdomen, reticulations absent, reticulations absent. 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 absent. Tibiotarsi without chaetae M.

Description. Habitus typical for Paranura Axelson, 1902 genus. Buccal cone elongate. Body length (without antennae) 0.35–0.9 mm (holotype: 0.48 mm). Colour of body when alive and in alcohol white. Tubercles developed on last abdominal segments (Figs 50, 52). Ordinary dorsal chaetae (Figs 50, 52, 55) differentiated into short, thin, acuminate microchaetae, medium size, smooth, acuminate mesochaetae and long, nearly smooth (with small denticles visible under magnification 1000x, Fig. 55), relatively thick, acuminate macrochaetae Ml and Mc. No plurichaetosis on body.

Head. Antennae slightly shorter than head (Fig. 50). S-chaetae of ant. IV relatively short and thick, S1 and S2 distinctly thinner than others (Fig. 49). Apical bulb unilobed. Chaetotaxy of antennae as in Fig. 49 and Tab. 9. Buccal cone relatively short and rounded at apex. Maxilla needle-like, mandible tridentate. Chaetotaxy of labium as in Fig. 48, with 2 lateral chaetae and without labial papillae x. Labrum chaetotaxy 4/2,4,4 (Fig. 51). Group Vi with 6+6 chaetae (Fig. 48). Groups Vea, Vem and Vep with 3, 4 and 4 chaetae respectively. Dorsal chaetotaxy of head as in Tab. 9 and Fig. 50. 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). 2+2 relatively small black eyes with diameter two times as large as the diameter of chaeta Ocm socket (Fig. 50).

Thorax, abdomen, legs. Dorsal chaetotaxy as in Figs 50, 52 and in Tab. 10. Ventral chaetotaxy as in Tab. 10 and Figs 53, 54. S-chaetae long, slightly longer than nearby macrochaetae (Figs 50, 56). S-chaetae formula of body: 022/11111, s-microchaeta on Dl of th. II present. Tubrcles Di on abd. IV sometimes fused (Fig. 52). Furcal remnant with 3–5 mesochaetae and 6 microchaetae (Figs 53, 54). Male without ventral modified chaetae (“male ventral organ”). Microchaetae on abd. VI located along midline (Fig. 53). Claw without internal tooth. Chaeta M absent on tibiotarsus, chaetae B4 and B5 short. Chaetotaxy of legs as in Tab. 10.

Types. Holotype: female on slide, United States of America, 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, litter, 27.IX.2006, leg. A. Smolis. Holotype housed in DIBEC. Paratypes: 7 females, 11 males and 12 juveniles on slides, same data as holotype. Four paratypes (female, 2 males and juv.) preserved in MNHN, the others in DIBEC.

Other material. Female and male on slides (DIBEC), USA: Oregon, Coast Range, 18 km North of Florence Town, old-growth forest of Picea sitchensis zone around the Giant Spruce tree, litter, 10.VI.2009, leg. A. Smolis.

Remarks. The species is superficially most similar to Paranura kedrovayensis sp. nov. They differ in a number of details, including the chaetotaxy of abd. IV (in P. microchaetosa sp. nov. only 1 ordinary chaeta De, in P. kedrovayensis sp. nov. 2 chaetae De), of trochanters (in P. microchaetosa sp. nov. with 6 chaetae, in P. kedrovayensis sp. nov. with 5 chaetae) and of labium (in P. microchaetosa sp. nov. 8+8 chaetae, in P. kedrovayensis sp. nov. 10+10 chaetae). Another discriminant character is the presence of microchaetae on furcal remnant in P. microchaetosa sp. nov. (absent in P. kedrovayensis sp. nov.).

Among formerly described species of the genus known from North America, P. microchaetosa sp. nov. is most similar to P. quadrilobata Hammer, 1953, resembling that species in having the same number of eyes, ocular chaetae and chaetae Di in V abdomen. The mentioned species was described from Canada (Hammer 1953) and lately partially revised and discussed by Fjellberg (1985) in his monograph of Arctic Collembola. Based on the original description and Fjellberg’s revision it can be stated that the main differences between these species include the shape of antennal apical bulb (in P. microchaetosa sp. nov. unilobed, in quadrilobata trilobed), the number of chaetae De on thorax III (in P. microchaetosa sp. nov. 4+s, in quadrilobata 3+s) and the number of chaetae De on abdomen IV (in P. microchaetosa sp. nov. 1+s, in quadrilobata 2+s).

Biology. The new species is resident in conifer old-growth forest of both Tsuga heterophylla (Fig. 57) and Picea sitchensis Zones (Franklin & Dyreness 1988). It inhabits thick litter, and despite intensive research not found in soil/dead wood samples. Bisexual form.