Mesaphorura critica Ellis 1976

Mesaphorura critica Ellis, 1976, new record to China

Figures 32–41, Table 4

Material examined. 10 females (slide Nos. XJ-2016001–XJ-2016004), Northwest China, Xinjiang Province, Aletai City, Buerjin County, Jiadengyu, 48°29’ N 87°08’E, elev. 1450 m, soil samples from mixed forest, 18-VIII-2016; 25 females (slide Nos. XJ-2016005–XJ-2016021), Northwest China, Xinjiang Province, Aletai City, Buerjin County, Hemu village, 48°33’ N 87°25’E, elev. 1150 m, soil samples from broad-leaf forest, 20-VIII-2016; 7 females (slide Nos. XJ-2016005–XJ-2016021), Northwest China, Xinjiang Province, Aletai City, Buerjin County, Kanasi Lake, 48°40’ N 87°01’E, elev. 1300 m, soil samples from broad-leaf forest, 24-VIII-2016; 7 females (slide Nos. XJ- 2016027–XJ-2016033), Northwest China, Xinjiang Province, Aletai City, Habahe County, 48°04’ N 86°20’E, elev. 470 m, soil samples from broad-leaf forest, 27-VIII-2016; 15 females (slide Nos. XJ-2016034–XJ-2016037), Northwest China, Xinjiang Province, Bole City, Hariturege Park, 45°08’N 81°46’E, elev. 1125 m, soil samples from the forest of Populus euphratica, 31-VIII-2016; 45 females (slide Nos. XJ-2016046–XJ-2016054), Northwest China, Xinjiang Province, Bole City, Sailimu lake, 44°29’N 81°09’E, elev. 2100 m, soil samples from coniferous forest, 1-IX-2016, all specimens are collected by Cheng-Wang Huang.

Diagnosis. Postantennal organ with 26–32 simple compressed vesicles in two parallel rows; pseudocelli of type I, with formula of 11/011/10011, and situated between setae m5 and p5 on Th. II and III; sensillum b on Ant. IV distinctly thinker than others; Abd. IV with setae m4 and m5, p1 as microseta and p2 as macroseta; Abd. V with only two microsetae a1 and a3 between macroseta a4 (a2 absent), sensillum p3 spindle-like; anal lobes with l3’ present, l2’ absent.

Description of Chinese materials. Adult body 0.47 mm long on average (0.45–0.50 mm, n = 30). Dorsal setae well differentiated into micro- and macrosetae (Figs 36–39). Granulations on body fine. Pso formula as 11/011/10011 from head to abdomen, 8–9 μm in diameter, type I (Figs 33, 36–37). On Th. II and III each with one pair of lateral pso between setae m5/p5, close to m5 (Fig. 36); pso on Abd. I and IV posterior to seta p3 (Figs 37, 39), on Abd. V between the borders of Abd. V and VI (Fig. 39).

Cephalic seta a0 and sd5 as mesosetae, 5–7 μm, c1 absent, oc2 as macroseta, 10–13 μm (Fig. 33). Postantennal organ 14–16 μm long and 5–6 μm wide, composed of 26–32 elliptical vesicles arranged in two rows (Figs 34–35). Labrum with 4/5/4 setae. Labium with 5 papillae, 6 apical guard setae, 6 proximal setae, 4 basomedian setae, and 5 basolateral setae.

Antenna (60–65 μm) shorter than head (70–80 μm). Antennal segment IV with five thickened sensilla a–e, sensillum b dinstinctly thicker than others. Small microsensillum, subapical organite and one apical vesicle present. Antennal organ III consists of two small sensory rods concealed behind one large papilla and two thick sensory clubs bent toward each other, with four guard setae; one large ventral sensory club present.

Legs short, without clavate tibiotarsal hairs. Coxa, trochanter, femur and tibiotarsus with 3/7/7; 5/5/4; 9/9/9; 11/11/11 setae on Leg I, II and III respectively. Claw 9–10 μm long, with tiny empodial appendage (3 μm). Anal lobes with seta l3' only, 12' absent (Fig. 41). Anal spines short, 6–8 μm long.

Adult chaetotaxy given in Figs 36–39 and Table 4. Microsensilla present on Th. II–III, lateral sensilla 15–18 μm long (Fig. 36). Th. II and III with a2 seta present. Thorax with 0, 2, 2 ventral setae. Abd. I–III with 2+2 axial setae each and seta m4 present (Figs 37–38). Abd. IV with setae m4 and m5 present, p1 as microsetae (6–7 μm) and in proximal position above macroseta p2 (12–17 μm) (Fig. 39). Abdominal segment V (Fig. 39) with seta a2 absent, sensillum p3 spindle-like, 8–10 μm in length; a4 (15–20 μm) and p2 (14–19 μm) as macroseta. Crescentic ridges on abdominal segment VI present (Fig. 39).

Ventral tube with 4+4 apical setae and 2+2 basal setae (Fig. 40). Abd. II, III and IV with 17–18, 20–22, and 24–26 ventral setae respectively. Female genital plate with 6+6 pregenital setae, 3 circumgenital setae, one pair of eugenital setae and 2 pairs of post-genital setae.

1 seta m4 present; 2 seta m4 and m5 present; 3 seta px present, p1<p2; 4 setae a2 absent, a4 as macroseta; 5 sensillum p3 spindle-like, seta p2 as macroseta; 6 female genital plate with 3 circumgenital and one pair of eugenital setae.

Distribution. China (Xinjiang); known from Palearctic and South Australia.

Remarks. Mesaphorura critica was first found in sands in Greece. It is widely distributed in the world, from North Europe (Greenland and Norwary) to North Africa (Morocco, Senegal), from Spain to Russia, and also recorded from South Australia (Greenslade 1992). It was usually found in dry open habitats such as meadows or the shore, rarely in forest (Dunger & Schlitt 2011). We found it occurred in different kinds of forests of Xinjiang frequently and with high density.