Subisotoma homonomica Potapov, Babenko, Fjellberg & Greenslade, 2009, sp. nov.

Subisotoma homonomica sp. nov.

Figs 4, 24–27, Tab. 2

Type material. Holotype, female, Russia, Kuril Islands, Kunashir, vicinity of Yuzhno–Kuril’sk [44° 01’N, 145° 51’E], under logs on a sea shore, 18.vi.1990, leg. S. Bugrov (MSPU). Paratypes: 3 females, the same data as the holotype (MSPU).

Description. Size 1.2–1.4 mm (subadults). Colour dark. Cuticle granulation with large pits all over the body with largest on head. Ocelli 8+8, H and G clearly smaller (Fig. 27). PAO wide elliptic, without constriction, about 1.5–2.0 as long as ocellus diameter and clearly shorter than inner unguis (0.5–0.7: 1). Maxillary palp simple, 4 sublobal chaetae. Labrum with 2/554 chaetae. Labium with papillae A–E present, proximal chaetae 3. Papilla E with 6 guard chaetae (e7 absent). Basomedial field of labium with 4 chaetae. Ventral side of head with 4+4 or 5+5 postlabial chaetae. Ant.1 with 2 bms, dorsal and ventral, and 2 ventral sensilla (s), Ant.2 with 3 bms and 1 distal s, Ant.3 with 1 bms and 5 distal s, including one lateral. AO with cylindrical inner sensilla and with 5–6 additional sensilla on dorsal side (Fig. 25). Ant.4 with numerous poorly differentiated sensilla, subapical organite small, microsensillum present.

All terga with dense cover of short, uniform chaetae, macrochaetae poorly developed, on Abd.V 0.2 times as long as tergite length. Dorsal axial chaetom of Th.II–Abd.III as 11–12,8/6–7,6,7. Tergal sensilla fine and rather long, but distinctly shorter than ordinary chaetae. Sensillar formulas as 33/33334 (s) and 10/101 (ms) (Figs 4, 24). On Abd.I–III medial sensilla set slightly in front of the p-row of chaetae. Sterna of Th.3 with 2+2 chaetae.

Unguis with clear inner tooth in distal 2/3. Ti.1–3 with 21, 23, 25 chaetae respectively. Tenent chaetae 1– 2–2, clearly clavate, longer than inner edge of unguis (U3: t.ch. = 0.6). Ventral tube with 4+4 lateral and 4–5 posterior chaetae. Tenaculum with (2)3+3 teeth and one chaeta. Anterior furcal subcoxae with 10–12 chaetae, posterior ones with 8–9 chaetae. Manubrium without anterior chaetae, posterior side with about 10+10 chaetae, laterobasal lobes usually with 4 chaetae. Dens with one anterior and (3)4 posterior strong chaetae (Fig. 26). Mucro narrow and rather long, with 2 teeth, clearly set off from dens. Ratio of manubrium: dens: mucro = 5.1–7.1: 3.6–4.2: 1. Each anal lobes with 3 tiny equal setulae.

Affinity. The most notable feature of S. homonomica sp. nov. is peculiar sensillar chaetotaxy of Abd.I–III with 3–3–3 accp-sensilla. Only S. pusilla has the same condition, but differs in having more macrosensilla on Th.II–III.

Distribution. Known only from the type locality.

Name derivation. The name of the new species refers to the constant number of sensilla almost on all terga (from Greek ‘ homos ’––the same, ‘ nomos ’––law, principle)