Scutisotoma bengei, Huang, Cheng-Wang & Potapov, Mikhail, 2012

Huang, Cheng-Wang & Potapov, Mikhail, 2012, Taxonomy of the Proisotoma complex. IV. Notes on chaetotaxy of femur and description of new species of Scutisotoma and Weberacantha from Asia, Zootaxa 3333, pp. 38-49 : 41-43

Scutisotoma bengei sp. nov.

Figs 7–14 , 18 , Tab. 1

Material. Holotype, female, China (south-west), Sichuan Province, Litang County, Benge Village, 29°53’N, 100°20’E, 4026 m alt., border area between grassland and forest, litter, 27.vii.2009, leg. W.J. Chen. Paratypes, 1 subadult male, 4 subadult females, same locality. Type specimens deposited in SIPPE.

Material of S. christianseni (Stach) . Two type specimens labelled as " Liban środk. Jebel Sannine 2000 m 12.IV.1958 leg. Dr. K. Kowalski na śniegu i pod kamieniami", deposited in ISEA ( Poland).

Description. Size 1.3–1.7 mm. Colour dark-violet, extremities paler. Cuticle with fine primary granulation and numerous pits. Body stout, with long furca. All abdominal tergites clearly separated. Ocelli 8+8, G and H smaller ( Fig. 9 ). PAO elliptical, about 1.8–2.5 as long as ocellus diameter and 0.5–0.8 as long as U3. Maxillary outer lobe with 4 sublobal hairs and simple maxillary palp. Maxillary head with short, unmodified lamellae. Labral formula 4/ 5,5,4. Labium with a full set of papillae and guards. Proximal field with 3 chaetae, basomedian field with 4. Ventral side of a head usually with 4+4, more rarely 5+5, postlabial chaetae. Ant.1 with 2 basal microsensilla (dorsal and ventral), 2 ventral sensilla and 12–14 common chaetae. Ant.2 with 3 bms and 1 laterodistal s. Ant.3 with 1 bms and 6 distal s (2 inner, 2 guards and 2 lateral) ( Fig. 10 ). Sensilla on Ant.4 weakly differentiated, microsensillum and subapical organite small.

With numerous common chaetae of unequal size on body tergites. Abd.V, VI and posterior half of Abd IV with many thicker and stronger needle-like chaetae, both erect and strongly curved ( Fig. 7 ). Strong and thin chaetae alternate in p-row on Abd. IV. Macrochaetae weakly differentiated and fully masked among dense covering of strong common chaetae. The largest chaetae of Abd.V about half as long as tergite. Thorax without ventral axial chaetae. Sensilla on tergites short, much shorter than the most common chaetae, but hardly visible among the scattered shorter and thinner common chaetae. Sensillary formula 3,3/2,2,2,2,4 (s) and 1,1/1,1,1 (ms). Sensilla on Abd.I–III situated in front of p-row. Microsensilla on Abd.III set apart from sensilla, in more lateral position. On Abd.V sensilla of lateral pair (accp 3 and accp 4) slightly shorter and thinner than median sensilla ( Fig. 8 ).

Unguis simple, without inner tooth ( Fig. 11 ). Tibiotarsi with many additional chaetae (more than 25 on Ti.1–2). B-row of chaetae on Ti.1–2 complete. Tibiotarsal tenent chaetae (1,2,2) slightly clavate, about as long as inner edge of unguis (0.9–1.0: 1). Femur 1 with 6–8 a -chaetae, 1 ae -chaeta, 4 e -chaetae, and 9–12 chaetae of pe-ppi-i -group ( Fig. 4 ). Upper and lower subcoxa with 5–7 and 8−10 chaetae on Leg 2 and 11−13 and 9−12 on Leg 3. Ventral tube with 7+7(6) laterodistal and 4–6 posterior chaetae. Tenaculum with 4+4 teeth and one chaeta. Anterior furcal subcoxa with 32–36 chaetae, posterior with 10–12 chaetae. Anterior side of manubrium with a pair of distal chaetae, rarely 2+2 with the second pair positioned more laterally and at the middle of manubrium. Posterior side of manubrium with 33–38+33–38 (including 5+5 on laterobasal lobes) ( Fig. 13 ). Dens with 7 anterior chaetae in distal half, arranged as 1–1–2–3. Posterior side slightly crenulated, with 11–14 chaetae (5–7, usually 6 in basal group, 2–3 outer, 3 inner and 1 subapical). Mucro with three teeth, lamellae absent ( Figs 12, 14 ). Ratio of manubrium: dens: mucro = 8.9–10.0: 7.0–7.7: 1.0.

Affinity. The new species is closely related to S. christianseni ( Stach, 1959) sharing characters of the group (see above), missing ventromedial chaetae on thorax and tridentate mucro. It differs from S. christianseni by 7 (vs. 9) anterior chaetae on dens (see Fig. 16 for the latter species). Polychaetosis is characteristic for both species ( Figs 7 , 15 ). In two topotypes of S. christianseni microsensillum set very close to lateral sensillum on Abd. III ( Fig. 17 ), unlike in S. bengei sp. nov.

Distribution. Known only from the type-locality.

Name derivation. Named after the locality where the species was collected.

Figures

FIGURES 7 – 14. Scutisotoma bengei sp. nov.: 7, posterior part of abdomen (chaetae of Abd. VI not shown); 8, position of sensilla on Abd. V, other individual; 9, PAO and ocelli; 10, chaetotaxy of Ant. 3; 11, apical part of Leg 3; 12, dens and mucro, lateral view; 13, furca, posterior view; 14, dens and mucro, anterior view.

FIGURES 15 – 18. Scutisotoma christianseni (15 – 17) and S. bengei sp. nov. (18): 15, posterior part of abdomen (chaetae of Abd. VI not shown); 16, dens and mucro, lateral view; 17 – 18, position of s and ms on Abd. III.

FIGURES 1 – 6. Chaetotaxy of femur (1, 3 − 6, posterior view; 2, external view): 1 − 2, Scutisotoma robustodens sp. nov.; 3, Scutisotoma trichaetosa sp. nov.; 4, Scutisotoma bengei sp. nov.; 5, Weberacantha cylindrica sp. nov.; 6, Weberacantha beckeri. For abbreviations of groups of chaetae see text.