Subisotoma posteriomollis, Potapov, Mikhail, Babenko, Anatoly, Fjellberg, Arne & Greenslade, Penelope, 2009

Potapov, Mikhail, Babenko, Anatoly, Fjellberg, Arne & Greenslade, Penelope, 2009, Taxonomy of the Proisotoma complex. II. A revision of the genus Subisotoma and a description of Isotopenola gen. nov. (Collembola: Isotomidae), Zootaxa 2314, pp. 1-40 : 19-20

Subisotoma posteriomollis sp. nov.

Figs 7 , 46–50 , Tab. 2

Type material. Holotype, female, Vietnam, Province Ha Tien, Nui Da Dung, secondary forest, litter, 29.xi.2006, leg. L. Deharveng & A. Bedos ( MNHN, sample code Vn06–104). Paratypes, 4 females (on slides) and 5 specimens (alcohol), the same data as the holotype (3 in MSPU, others in MNHN).

Description. Size 0.9 mm. Colour greyish-black with numerous lighter spots. Cuticle granulation fine and almost uniform (pits very small and hardly visible). Ocelli 8+8, H and G clearly smaller. PAO wide elliptic, without constriction, about 1.5 as long as ocellus diameter and shorter than inner unguis (0.9:1). Maxillary palp simple with 4 sublobal chaetae. Labrum with 2/554 chaetae. Labium with all papillae A–E present, papilla E with 6 guard chaetae (e7 absent), proximal chaetae 3. Basomedial and basolateral fields of labium with 4 and 5 chaetae. Ventral side of head with 4+4 (5) postlabial chaetae. Ant.1 with 2 bms (dorsal and ventral) and 2 ventral sensilla (s) of different size, Ant.2 with 3 bms and 1 distal s, Ant.3 with one rather long bms and 5 distal s, including one lateral in АО. Inner sensilla of АО clearly broadened, dorsal side of the segment with 9–10 additional sensilla ( Fig. 50 ). Ant.4 with numerous poorly differentiated sensilla, subapical organite small, microsensillum present.

All terga with dense cover of short, uniform chaetae, macrochaetae poorly developed. Longest chaetae on Abd.V 0.16–0.23 as long as tergal length. Dorsal axial chaetom of Th.II–Abd.III as 8–9,6–8/5,5–6,6. Tergal sensilla fine and long, only slightly shorter than ordinary chaetae. Sensillar formulas as 3,3/2,2–3,3,5–7,5–7 (s) and 10/101 (ms) ( Figs 7 , 46–48 ). On Abd.I–III medial sensilla set slightly in front of p-row of chaetae. Ventral side of Th.III with (1)2+2 chaetae.

Unguis usually with a small inner tooth, sometimes hardly visible. Ti.1–3 with 21, 21–24, 22–25 chaetae. Tibiotarsal tenent chaetae 1–2–2, clearly clavate, longer than inner edge of unguis (U3: t.ch. = 0.5–0.7). Ventral tube with 4+4 lateral and 4 posterior chaetae. Tenaculum with 3+3 teeth and one chaeta. Anterior furcal subcoxae with 8–9 chaetae, posterior ones with 5–7. Manubrium without anterior chaetae, posterior side with about 9+9 chaetae, laterobasal lobes with 3–4 chaetae. Dens with one anterior and 4 posterior chaetae, the anterior one shorter than others, rarely absent. Mucro narrow with 2 teeth, not clearly set off from dens ( Fig. 49 ). Ratio of manubrium: dens: mucro = 5.5–6.0: 3.1–4.2: 1. Each anal lobe with 3 tiny setulae.

Affinity. A unique character of the new species is the increased number of macrosensilla only on Abd.IV– V. In other ‘polysensillar’ species, S. multisensillata sp. nov. and in most species of Isotopenola the number of sensilla is increased also on thoracic segments.

Distribution. Known only from the type locality.

Name derivation. The name relates to the high number of sensilla on the tip of the abdomen (from Latin ‘ mollis ’––soft, tender).

Figures

FIGURES 7 – 8. Sensillar chaetotaxy of Subisotoma: 7, Subisotoma posteriomollis sp. nov. (3,3 / 2,2 – 3,3,6 – 7,5 – 7); 8, Subisotoma multisensillata sp. nov. (4 – 7,6 – 12 / 4 – 5,3 – 6,3 – 5,4,5 – 11).

FIGURES 46 – 50. Subisotoma posteriomollis sp. nov.: 46 – 48, sensillar chaetotaxy of Abd. IV – VI (variants); 49, mucrodens; 50, Ant. 3, dorsal view.