Scutisotoma matalini, 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 : 36-38

Scutisotoma matalini sp.n.

Figs. 99–102

Type material. Holotype: ♀, Russia, northern Altai Mts., right bank of Katun river, vicinity of Ust-Sema village (51 o 39’N, 85 o 44’E), plant debris on sandy bank, 27.vii.2000, leg. A. Matalin. Paratypes: 6 exx., same sample. 6 exx., same mountain region, Altaisky Reserve , Teletskoye Lake, bay of Kokshi River, plant debris on shore, 08.vii.2002, leg. A. Matalin ( MSPU) .

Other material. 21 exx., Russia, central Altai, Inya (50 o 27’N, 86 o 36’E), river sediments above Katun river, cliffs with Sedum , cliffs with Parmelia , and steppe with Artemisia frigida , 14.ix.1988, leg. S. Stebaeva. 10 exx., same region, from river Sarlyk (on the way to Seminski passage), plant cover on cliffs, 16.ix.1988, leg. S. Stebaeva ( MSPU).

Description. Size 0.7–1.0 mm. Colour dark, blue-violet with numerous paler spots, ventral side and extremities paler. Cuticle with fine granulation. 8+8 ocelli, G and H clearly smaller. PAO narrow elliptical, not constricted, about 1.5–2.0 as long as ocellus diameter and 0.7–1.0 as long as U 3. Maxillary outer lobe with bifurcate palp and 4 sublobal hairs. Maxillary head with short, unmodified lamellae. Labral formula 4/554. Labium with a full set of papillae and guards. Proximal field with 3 chaetae, basomedian with 4. Ventral side of a head usually with (4)5+5 postlabial chaetae. Ant.1 with 2 basal microsensilla (bms, dorsal and ventral) and 2 ventral sensilla (s). Ant.2 with 3 bms and one laterodistal s, Ant.3 with one bms and 5 distal s (AO and one lateral s) ( Fig. 101 ). Additional sensilla on Ant. 2–3 in males usually long, chaeta-like. Sensilla on Ant.4 hardly differentiated, subapical organite small.

Dorsal axial chaetom of Th.II–Abd.III as 9–10,7–8/5–6,6–7,6–7. Thorax without ventral axial chaetae. Macrochaetae differentiated laterally on Th.II–III and on tip of abdomen, medial ones on Abd.V are about 0.3 as long as tergite. Sensilla on tergites short and slightly widened. Sensillary formula 33/22224 (s) and 11/111 (ms). Sensilla on Abd.I–III in mid-tergal position (medial sensillum on Abd.III in posterior 1/3 of the tergite). The two lateral sensilla on Abd.V longer than median ones. Position of sensilla on Abd.V variable: accp4 may be in line with or in front of medial pair, accp3 always in anterior position, just in front of accp2 or more medially ( Fig. 102 ).

Unguis slender, without inner tooth. Number of chaetae on Ti.1–3 (21/21/25–27) is similar to the basic set. B-row on Ti.1–2 with 7 chaetae. Chaetae x and B 5 on Ti. 3 in males slender and slightly longer than ordinary chaetae. Tibiotarsal tenent chaetae (1-2-2) clearly clavate, slightly longer than unguis (U 3: t.ch. = 0.8–1.0: 1). Ventral tube with 4+4 laterodistal and 5–6 posterior chaetae. Tenaculum with 3+3(4) teeth and one chaeta. Anterior furcal subcoxa with 17–20, posterior one with 8–12 chaetae. Anterior side of manubrium with a pair of distal chaetae, posterior side with 16–23+16–23 on the main part and 4 on each laterobasal lobe. Dens with 9–13 anterior chaetae (basal 1/3–1/5 without chaetae) ( Fig. 100 ). Posterior side of dens crenulated, with 8–9 chaetae (4–5 basal, 1 outer, 2 inner and 1 subapical near mucro) ( Fig. 99 ). Mucro with 3 subequal teeth set close together. Ratio of manubrium: dens: mucro = 5.6–7.1:4.0–5.4:1. Medial chaeta on each of the anal lobes clearly longer than lateral ones.

Affinity. S. matalini is most similar to S. schisti . The most significant difference seems to be the number of posterior chaetae on dens ( schisti usually has 2 outer and 3 inner chaetae in lateral rows, matalini only with 1 and 2 chaetae correspondingly). They differ also in position of sensilla on Abd.V (cf. Fig. 92 and Fig. 102 ).

Chaetotaxy of posterior side of dens in S. matalini sp.n. is identical to that of S. kolymica sp.n. (see above). The species can easily be distinguished by the number of lateral sensilla on Ant.3 and position of sensilla on Abd.V. The bare part of anterior side of dens is usually larger in S. matalini (0.31–0.45) than in kolymica (0.17–0.34).

Distribution. Known from several localities of central and northern Altai.

Name derivation. Named after our Moscow colleague Andrei Matalin, who collected some of the material.

Figures

FIGURES 99–102. Scutisotoma matalini sp.n. 99, 100, dens, posterior and lateral; 101, Ant.3, lateral (ls: lateral sensillum); 102, chaetotaxy of Abd.V, below — variation in sensillary patterns (s1–4: accp1–4 sensilla).

FIGURES 87–92. Scutisotoma schisti sp.n. 87, 88, anterior and posterior sides of furca; 89, dens, lateral; 90, PAO and ocelli; 91, tenaculum; 92, chaetotaxy of Abd.V.