Paranura tsushimaensis Kasai sp. nov.

[Japanese name: Rurihoso-ibonashi-tobimushi]

Figs 1–11, Tables 1–2

Type material. Holotype: male, Japan, Kyushu, Nagasaki Prefecture, Tsushima-shi, Tsushima Island, Kamitsushimacho (alt. 33 m, 34°35'52"N 129°25'10"E), evergreen forest, rotten fallen branch, 27-XI-2022, Kahito Nakamura & Hiro Kasai leg. (NMNS, NSMT-Ap 671) . Paratypes: 2 females (NMNS, NSMT-Ap 672–673), 2 males (NMNS, NSMT-Ap 674–675), and juvenile (NMNS, NSMT-Ap 676); same data as the holotype .

Etymology. The new species is named after the type locality, Tsushima Island.

Diagnosis. 3+3 black eyes on head. Dark blue body color. Body elongated and flattened. Some tubercles present on dorsal side of body, underlined by reticulations. Abd. V four times as long as Abd. VI. Ant. II with 12 chaetae. Chaetae O, A, E, and three ocular chaetae present on head. Lateral area on head with 6 chaetae Dl and 10 chaetae (L+So). Th. II–III with 3 and 4 ordinary chaetae De respectively. Tubercles Di on Abd. V not developed, with 2+2 chaetae Di. Abd. V with 9 ordinary chaetae De+Dl+L. Furcal remnant with 5–7 mesochaetae and no microchaetae. Tibiotarsi with chaeta M.

Description. Body length (without antennae) 1.58–1.83 mm in adults. Color of the body dark blue (Fig. 1). 3+3 black eyes, two anterior and one posterior. Body elongated and flattened (Fig. 4).

Chaetal morphology. Five types of dorsal ordinary chaetae. Long macrochaetae (Ml) relatively long, thickened, sheathed, apically acuminated; some lateral chaetae longer and strongly acuminate at the apex (Fig. 10). Short macrochaetae (Mc) morphologically similar to Ml, but much shorter. Very short macrochaetae (Mcc) relatively thick and weakly acuminated (Fig. 9). Mesochaetae (me) and microchaetae (mi) similar to ventral chaetae: thin, smooth, and pointed. S–chaetae of tergites thin and smooth.

Antennal morphology and chaetotaxy. Antenna 4-segmented. Ratio of antennal segments I: II: III + IV = 1:1:1.5. Dorso-central area on Ant. III–IV weakly granulated. S-chaetae of Ant. IV relatively long and thick, S1 and S2 slightly thinner than others (Fig. 2). Apical bulb distinct and trilobed. Chaetotaxy of antennae shown in Table 1b and Figs 2–3.

Mouthparts. Buccal cone relatively long and rounded at apex. Labrum chaetotaxy 0/2,2 (Fig. 5). Labium with 4 basal, 3 distal, and 4 lateral chaetae, papillae x absent (Fig. 6). Mandible with 3 teeth. Maxilla styliform.

Cephalic tubercles and chaetotaxy. Tubercle Cl weakly developed (Fig. 4). Chaetotaxy of the central area complete (Fig. 4). Lateral area with 6 chaetae Dl and 10 chaetae (L+So). Dorsal chaetotaxy of the head shown in Table 1a and Fig. 4. Group Vi with 6+6 chaetae. Groups Vea, Vem, and Vep with 4, 3, and 4 chaetae respectively.

Body tubercles and chaetotaxy. Tubercle Dl on Abd. IV, tubercle De+Dl+L on Abd. V, and a unique tubercle on Abd. Vl developed and reticulated (Figs 4, 11). Tubercles Di on Abd. V not developed, with 2+2 chaetae Di. Abd. V very long, four times as long as the last segment of the body (Figs 4, 11). Dorsal chaetotaxy shown in Table 2 and Figs 4, 11. Furcal remnant with 5–7 mesochaetae and no microchaetae. Genital plate with 28–30 and 12–30 chaetae in females and males respectively. An with 2 mi, rarely one side absent. Ventral chaetotaxy shown in Table 2 and Fig. 7.

Legs. Tibiotarsi I, II, and III with 19, 19, and 18 chaetae respectively, chaeta M present. Unguis without inner tooth (Fig. 8). Chaetae B4 and B5 long. Chaetotaxy of the legs shown in Table 2 and Fig. 8.

Remarks. Paranura tsushimaensis sp. nov. is the third species with a bluish body color, a very long abdominal segment V, and reticulations in the dorsal area. P. tsushimaensis sp. nov. is the most similar to P. reticulata Smolis & Deharveng, 2015, having a head with 3 ocular chaetae, the lateral area of the head with 16 chaetae, and 4 ordinary chaetae De on Th. III. However, this new species is clearly distinguishable from P. reticulata by the absence of prelabral chaetae (in P. reticulata 4), 2+2 ordinary chaetae Di on Abd. V (in P. reticulata 3+3), 9 ordinary chaetae De+Dl+L on Abd. V (in P. reticulata 6–7), and microchaetae absent on the furcal remnant (in P. reticulata present). This new species is also similar to P. s-uenoi Yosii, 1955 . However, the new species differs with 3 ocular chaetae on the head (in P. s-uenoi 2), 2 ordinary chaetae De on Th. I (in P. s-uenoi 3), and 4 ordinary chaetae De on Th. III (in P. s-uenoi 3).