Subisotoma tenuis ( Dunger, 1982 )

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 : 11

Subisotoma tenuis ( Dunger, 1982)

Figs 1 , 29, 32 , Tab. 2

Proisotoma (s.str.) tenuis Dunger, 1982: 51

Material. 2 paratypes, Mongolia, Central Aimak, sample 760 in Dunger (1982) ( SMNG), 11 specimens, Russia, Buryatia, Vitim Plateau, Telemba, birch forest mixed with larch, 06.i.2008, leg. А. Chimitova; 7 specimens, Russia, Irkutsk Province, W Khamar–Daban Range, Cherskogo Peak, rocks, steep northern slope, cold mossy shelves in permanent shadow, 2000 m alt., 26.viii.2008, leg. M. Potapov, 1 specimen, Russia, Yakutia, middle reaches of Indigirka river, Ust'–Nera, 800 m alt., mosses and litter on stones, 21.vii.1992, leg. M. Potapov ( MSPU); 1 specimen, Russia, Yakutia, Suntar–Khayata Mt. Range, Kyubyume River, 1250 m alt., bog, 30.vii.2002, leg. O. Makarova ( MSPU).

Redescription. Size 1.2–1.3 mm. Colour almost-black, with numerous light spots. Ventral side and appendices also coloured. Cuticular big pits regularly scattered all over body, larger on head (as in Fig. 53 ). Ocelli 8+8, H and G clearly smaller. PAO small, narrow elliptical, without constriction, 1.5–2.0 as long as ocellus diameter and 0.6–0.8 as long as inner unguis. Maxillary palp simple, 4 sublobal chaetae present. Labral formula as 2/554. Labium with papillae A–E present, papilla Е with 6 guard chaetae (е 7 absent), proximal part of labium with 3 chaetae, basomedian and basolateral fields with 4 and 5 chaetae as usual. Ventral side of head with (4)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 1 lateral (= АО), “inner” sensilla of АО clearly broadened. One additional sensillum present on dorsal side of Ant.3 ( Fig. 29 ). Ant.4 with numerous poorly differentiated sensilla, subapical organite small, microsensillum present.

All terga with dense cover of short, uniform chaetae, macrochaetae not developed. Dorsal axial chaetom as 11–13,9–11/7–8,7–8,7–9. Tergal sensilla shorter and finer than ordinary chaetae. Sensillar formulas 33/ 22224 (s) and 10/101 (ms). Arrangement of sensilla and microsensilla as on Fig. 1 . On Abd.I–III medial sensilla set well in front of the p-row. Ventral side of Th.III with 1+1 strong chaetae ( Fig. 32 ).

Unguis normally with a weak tooth in the distal 2/3 of the inner edge. Ti.1–3 with additional proximal chaetae: 22–25, 24–27, 25–30 respectively. Tenent chaetae on Ti.1–3 1–2–2, long and clearly clavate, longer than inner unguis (U3: t.ch. = 0.55–0.70). The long ‘ ventrale Spürhaare’ on Ti.1–2 (chaeta B4) and on femora which was mentioned by Dunger (1982), are present as in the majority of other species of the genus. Chaetae x and B5 on Ti.3 undifferentiated in the studied males. Ventral tube with 4+4 laterodistal and 4 caudal chaetae. Tenaculum with 3+3 teeth and one chaeta. Anterior furcal subcoxae with 12–15 chaetae, posterior ones with 7–9. Anterior side of manubrium without chaetae, posterior side with 11–12+11–12 chaetae, laterobasal lobes usually with 4 chaetae. Dens rather long with one anterior and 4 posterior chaetae. Mucro clearly set off from dens, narrow and long, with two teeth and more or less clear lateral lamella. Ratio of manubrium: dens: mucro = 4.5–7.5: 2.5–4.0: 1. Each anal lobe with 3 tiny equal setulae.

Affinity. A study of the two paratypes of S. tenuis from Mongolia revealed that sensillar formula given in the original description (3,2/2,1(2),1,2,3) is not complete and the species is characterized by the common (for Anurophorinae ) number and arrangement of s and ms. The presence of only 1+1 ventral chaetae on Th.III and the only additional sensillum on Ant.3 separate S. tenuis from other species of the group which have a similar number of macro- and microsensilla ( S. bisensillata sp. nov. and S. guzeriplica sp. nov.).

Distribution. Probably widespread in Inner Asia being recorded from central and southern parts of Mongolia, Buryatia, and Yakutia.

Figures

FIGURES 1 – 6. Sensillar chaetotaxy of Subisotoma: 1, Subisotoma tenuis, Subisotoma bisensillata sp. nov. (3,3 / 2,2,2,2,4); 2, Subisotoma guzeriplica sp. nov. (3,3 / 2,2,2,3,4); 3, Subisotoma pomorskii sp. nov. (3,3 / 2,2 – 3,3,3,4); 4, Subisotoma homonomica sp. nov. (3,3 / 3,3,3,3,4); 5, Subisotoma quadrisensillata (3,3 / 3,3,3,4,4); 6, Subisotoma pusilla (4,4 / 3,3,3,3,4).

FIGURES 28 – 33. Subisotoma bisensillata sp. nov. (28, 30 – 31, 33) and Subisotoma tenuis (29, 32): 28 – 29, Ant. 3, dorsal view; 30, ocelli; 31, chaetotaxy of leg 3 and sterna of Th. III; 32, chaetotaxy of sterna of Th. III and ventral tube; 33, dens and mucro.

FIGURES 51 – 57. Subisotoma multisensillata sp. nov.: 51, chaetotaxy of abdomen (clusters of sensilla, furcal subcoxae and median setaceous fields of Abd. II encircled, chaetotaxy of posterior part of manubrium not shown); 52, ocelli and PAO; 53, fine structure of cuticle near posterior edge of head; 54, posterior side of manubrium and genital plate of male; 55, Ant. 3, dorsal view (variation of sensilla is shown); 56, dens and mucro, lateral view (variation is shown); 57, fine structure of cuticle on Abd. V.