Scutisotoma kolymica, Potapov & Babenko & Fjellberg, 2006

Potapov, Mikhail, Babenko, Anatoly & Fjellberg, Arne, 2006, Taxonomy of the Proisotoma complex. Redefinition of genera and description of new species of Scutisotoma and Weberacantha (Collembola, Isotomidae), Zootaxa 1382 (1), pp. 1-74 : 28-30

Scutisotoma kolymica sp.n.

Figs. 15 , 22 , 67–71

Type material. Holotype: ♀, Russia, Magadan Province, upper current of Kolyma river, 60 km west of Sinegor’e (62 o 27’N, 149 o 47’E), 1000 m alt., dry upper edge of slope with Carex argunensis , 25.viii.1987, leg. D. Berman. Paratypes: 30 exx., same sample ( MSPU) .

Other material. 10 exx., Russia, Chukotka, Bol’shoi Annachag Mt. Range, Aborigen Peak (61 o 58’N, 149 o 31’E), pitfall among slates, Pinus pumila , dry, 24.vii.1979, leg. A. Fjellberg. 15 exx., Russia, Far East, Khabarovsk Territory, Badzhalsky Range , Badzhal River , under Pinus pumila (1450 m alt.) and in mountain tundra (1500 m alt.), leg. N. Babushkin ( MSPU) .

Description. Size up to 1.0 mm. Colour dark, blue-violet with numerous paler spots, ventral side and extremities paler. Cuticle with fine primary granulation. Ocelli 8+8, G and H slightly smaller. PAO narrow elliptical, not constricted, 0.9–1.2 as long as U 3. Maxillary outer lobe with 4 sublobal hairs and bifurcate palp. Maxillary head with short unmodified lamellae ( Fig. 22 ). Labral formula 4/554. Labium with a complete set of papillae and guards ( Fig. 15 ). Proximal chaetae 3, basomedian chaetae 4. Ventral side of a head with 4–5+4–5 postlabial chaetae. Ant.1 with 2 basal microsensilla (bms) in dorsal and ventral position, and 2 ventral sensilla (s). Ant.2 with 3 bms and one laterodistal s, Ant.3 with one bms and 6 distal s (4 in AO and two lateral of similar length) ( Fig. 70 ). Lateral guards of AO slightly longer than the inner pair of sensilla. Additional sensilla on Ant.2–3 present in males. Sensilla on Ant.4 hardly differentiated, subapical organite small.

Dorsal axial chaetom of Th.II–Abd.III as 8–9,7–8/5,5,5–6. Thorax without ventral axial chaetae. Macrochaetae differentiated laterally on Th.II–III and on tip of abdomen, medial ones on Abd.V are 0.3–0.4 as long as tergite. Sensilla on tergites short and slightly thickened. Sensillary formula 33/22224 (s) and 11/111 (ms). Sensilla on Abd.I–III in almost mid-tergite position (medial sensillum on Abd.III set in posterior 1/3 of the tergite). On Abd.V the two medial and two lateral sensilla set far apart ( Fig. 71 ). The most lateral sensillum (accp4) displaced anteriorly, usually set in front of sensillum accp3. In the type population the microsensillum of Abd.III set rather far from the lateral sensillum, more medially (unlike Figs. 76–78 , see also remarks below).

Unguis rather slender, without inner tooth. The number of chaetae on Ti.1–3 is 21-21- 26(27), like the basic set. B-row on Ti.1-2 with 7 chaetae. Chaetae x and B 5 on Ti. 3 in subadult males slightly differentiated (full–sized males not seen). Tibiotarsal tenent chaetae (1-2-2) on Ti.1–3 clearly clavate, shorter than unguis (0.6–0.8 as long as U 3). Ventral tube with 4+4 laterodistal and 5–6 posterior chaetae. Tenaculum with 4+4 teeth and one chaeta. Anterior furcal subcoxa with 13–16, posterior with 9–10 chaetae. Anterior surface of manubrium with a pair of distal chaetae. Posterior surface with 17–20+17–20 chaetae on the main part and 4–5 on each laterobasal lobe ( Fig. 68 ). Dens with 8–11(12) anterior chaetae, usually arranged as 3,2,1,1...1 (basal quarter to one third of dens (usually about 1/4) without chaetae, Figs. 67, 69 ). Posterior side of dens crenulated, usually with 8 chaetae (4 basal, 1 outer, 2 inner and 1 subapical near mucro, Fig. 68 ). Mucro with 3 subequal teeth which set close together. Ratio of manubrium: dens: mucro = 4.9–6.5: 4.0–5.1: 1. Each anal lobe with 3 tiny chaetae of similar length.

Intraspecific variability. Specimens from Badzhalsky Mt. Range differ from the type population in more lateral position of microsensillum on Abd.III, set very close to the lateral sensillum (like in Fig. 77 ). At the moment we regard them as conspecific with kolymica .

Affinity. S. kolymica sp.n. is most similar to two new species described below. The first, S. longisensilla sp.n., has almost the same furcal characters (moderate size, similar chaetotaxy and mucro with 3 teeth), 2 lateral sensilla on Ant.3, and 4+4 tenacular teeth. Differentiating characters are the length of dorsal sensilla (long in S. longisensilla , short in S. kolymica ), their positions on Abd.V, and the length of the unsetaceous part of anterior side of dens (about 1/2 of dens in S. longisensilla , about 1/ 4 in S. kolymica ). The second, S. schisti sp.n., can easily be distinguished from S. kolymica by the presence of only one lateral sensillum on Ant.3 and higher number of chaetae on dens.

Distribution. Known only from two localities in the Far East of Russia.

Name derivation. The new species is named after the type-locality.

Figures

FIGURES 12–17. Morphological characters of the Proisotoma-complex. 12–14, inner side of Ti. 2 in Proisotoma minuta (12) and Ballistura schoetti (13–14) (tibiotarsal chaetae B4, B5, and B4/5); 15–17, labial palp in Scutisotoma kolymica sp.n. (15), P. clavipila (16), and S. tianshanica (17) (papilla E, and guard e7 encircled).

FIGURES 18–23. Maxillary head in Proisotoma minuta (18), Ballistura schoetti (19), Strenzketoma buddenbrocki (20), Scutisotoma karadagi sp.n. (21), Scutisotoma kolymica sp.n. (22), and “Proisotoma” ripicola (23) (1–6 maxillary lamellae).

FIGURES 67–71. Scutisotoma kolymica sp.n. 67–68, anterior and posterior views of furca; 69, dens laterally; 70, Ant.3, lateral view (ls: lateral sensilla); 71, chaetotaxy of Abd.V (s1–4: accp1–4 sensilla).

FIGURES 72–79. Scutisotoma longisensilla sp.n. 72, posterior side of manubrium; 73, 74, posterior and anterior sides of dens; 75, Ant.3, lateral view (ls – lateral sensilla); 76–78, variants in position of sensillum and microsensillum on Abd.III (p-chaetae connected by a line, s: sensillum, ms: microsensillum); 79, chaetotaxy of Abd.V (s1–4: accp1–4 sensilla).