Millotellina bambusinus, Jin & Bu, 2019

Jin, Ya-Li & Bu, Yun, 2019, Occurrence of Millotellina (Myriapoda, Symphyla) in China with the description of two new species, Zootaxa 4691 (3), pp. 215-224 : 220-222

Millotellina bambusinus new species

Figs. 23–43

Material Examined. Holotype, female (slide no. GX-JX-SY2018050) ( SNHM), China, Guangxi, Chongzuo City, Daxin County, Mingshi Village , soil samples of bamboo forest, Alt. 230 m, 22°42'N, 106°54'E, 7-IX-2015, coll. Y. Bu.

Diagnosis. Millotellina bambusinus sp. n. is characterized by the coniform unpaired median ventral processes between the coxal sacs of legs 5–10, the palp of second maxilla with three pointed branches, the frontal seta of leg 1 slender and distinctly shorter than the posterior claw, and the cerci narrowed abruptly in the distal part.

Description. Adult body 3.84 mm long (holotype).

Head: length 280 μm, width 430 μm ( Fig. 23 ). Dorsally covered with straight setae. Longest seta (43 μm) in front of lateral angle, half the length as first antennal segment diameter (88 μm). Three prominent setae of oblique post-antennal row longer than posterior setae, subequal to longest lateral angle setae ( Fig. 23 ). Dorsal cuticle glabrous, covered with mesh-work of cuticular thickenings present on anterior part of head, around antennae bases, lateral and posterior of head. Central rod (45 μm) 0.16-fold shorter than length of head ( Fig. 23 ), terminating poste- riorly in prominent ovoid swollen end, distance between swollen end and posterior margin of head (63 μm) 0.2-fold shorter than length of head. Tömösváry organ: ovoid, length 28 μm, width 23 μm, about 0.3-fold less than greatest diameter of first antennal segment ( Fig. 25 ). Mouthparts: Mandible with 8 pointed, separated teeth and 4 blunt, fused teeth ( Fig. 37 ). Inner lobe of first maxilla with 3 exterior thick teeth and 4 slender hook-shaped interior teeth; palp conical, with broad base, about 1.2 times longer than width of base, terminated with three pointed branches ( Fig. 38 ). Anterior part of second maxilla with many small protuberances and each carrying one seta, 3 pairs of distal setae thickened, posterior part with numerous setae. Cuticle of maxilla and labium covered with scaly cuticular thickenings ( Fig. 24 ). Antennae: with 25 segments. Antennal base short, densely granulated. First antennal segment 1.5 times wider than long (68 μm width: 45 μm length), primary whorl with 7 setae, dorsal seta longest, 0.4-fold shorter than width of segment. Second antennal segment 1.6 times wider than long (50 μm width: 30 μm length), with primary whorl of 9 setae, longest seta inserted outer-dorsally, its length 0.6-fold shorter than width of segment, two inner setae 0.9-fold shorter than length of longest outer setae. Third antennal segment 1.3 times wider than long (48 μm width: 38 μm length), with primary whorl of 11 setae, longest seta 0.6-fold shorter than width of segment. Proximal antennal segments each have only primary whorl of setae. Secondary whorl begins on antennal segment 6, tertiary whorl begins on antennal segment 14. Spatulate organs on dorsal side of antennal segments 3–5 ( Fig. 39 ). Small spined organs present on dorsal surface from antennal segment 4 onwards. Specialized sensory setae present on dorsal side of antennal segment 5 onwards. Apical antennal segment 1.6 times longer than wide (63 μm length: 40 μm width), distal half with 19 straight setae, the longest one about 0.75-fold shorter in length than greatest width of segment, with one large apical spined organ on elevated base, 0.3-fold shorter in length of segment, and two shorter small spined organ inserted nearby large one ( Fig. 26 ). Scale-like cuticular thickenings present on segments 1–2, mainly transverse, pubescent. Tergites: First tergite rudimentary, with 4 thick setae ( Fig. 27 ). Second tergite complete, 2.3 times wider than long (265 μm width: 118 μm length), posterior margin straight or somewhat con- vex ( Fig. 27 ). Anterolateral macrochaetae (63 μm) 0.9-fold shorter than diameter of antennal segment 1. Posterior margin with 23 setae, with longest one (40 μm) and shortest one (15 μm) 0.6 and 0.2-fold shorter than anterolateral macrochaetae respectively. Posterior half with numerous unequal length setae (15–57 μm), 0.2–0.8-fold shorter than longest posteromarginal setae. Anterior half with short pubescence on scale-like cuticular thickenings. Third tergite 1.9 times wider than long (330 μm width: 175 μm length), posterior margin straight, with 29 marginal setae, chaetotaxy similar to tergite 2 ( Figs. 28, 29 ). Tergite 4 broader than tergite 3. Anterolateral macrochaetae present on tergites 2, 3, 4, 6, 7 and 9. All tergites with sparse short pubescence on scale-like cuticular thickenings on anterior part. Leg 1: with four segments. Tarsus 4.6 times longer than wide (105 μm length: 23 μm width), tapering distally, with 6 dorsal setae and 7 ventral setae, length of setae increasing distally; distal-most dorsal seta longest, its length equal to greatest width of segment.Anterior claw slightly curved, more robust than posterior claw, its length 0.2-fold shorter than length of tarsus, and 1.2 times longer than posterior claw. Frontal seta slender, distinctly shorter than posterior claw ( Fig. 41 ). Tibia 1.7 times longer than wide (50 μm length: 30 μm width), with 4 lateral setae, longest one 0.6-fold shorter than greatest width of segment ( Fig. 41 ). Following segment 1.9 times longer than wide (75 μm length: 40 μm width), dorsally with scaly cuticular thickenings, with 7 ventral setae including two long setae, longest one reaching 0.6-fold of greatest width of segment ( Fig. 40 ). Leg 12: with five segments ( Fig. 42 ). Tarsus 4.1 times longer than wide (115 μm length: 28 μm width), subcylindrical, tapering distally, dorsally with several longitudinal rows of seate, two distal of them rather erect, longest one 0.9-fold shorter than greatest width of segment, ventrally with three longitudinal rows of setae. Anterior claw 0.2-fold shorter in length than of tarsus, 1.2 times longer than posterior claw. Posterior claw more slender than anterior one. Frontal seta short. Tibia 1.9 times longer than wide (88 μm length: 45 μm width), with 15 setae, length of longest dorsal seta 0.6-fold of greatest width of segment. Femur 1.4 times longer than wide (68 μm length: 50 μm width), two longitudinal rows of setae on lateral side, each of 3 or 4 setae, longest one 0.6-fold length of greatest width of segment. Trochanter 1.3 times longer than wide (100 μm length: 75 μm width), with numerous fine setae on ventral surface. Tarsus and tibia rather uniformly pubescent. Ventral side of femur and trochanter with pubescence on cuticular thickenings, dorsal side glabrous and with scaly cuticular thickenings. Styli: present at bases of legs 3–12, 2.7 times longer than the width of base (40 μm length: 15 μm width). Styli pubescent, with two distal setae, longer seta 0.4-fold length of stylus, shorter seta 0.3-fold shorter than length of longer seta, both tapering to pointed apex ( Figs. 30–36 ). Coxal sacs: present at base of legs 3–9, fully developed, each with 5–8 setae ( Figs. 30–36 ). Areas corresponding to coxal sacs at bases of legs 1, 2, 10, 11, 12 replaced by 0, 4, 3, 2, 2 setae, respectively. Coxal plates of legs 1 and 12 without setae, those of leg 2, 3–9, 10, 11 with 5, 7–10, 8, 6 setae, respectively ( Figs. 30–36 ). Median ventral processes: unpaired, located between coxal sacs of legs 5–10, subconical, 1.4–1.7 times longer than width of base (43–50 μm length: 25–35 μm width), subequal to stylus. Cuticle with short, dense, curved pubescence ( Figs. 30–36 ). Cerci: 3.0 times longer than wide (243 μm length: 80 μm width), 0.1-fold length of body, covered by dense setae, and narrowed abruptly in distal part ( Fig. 43 ). Cerci dorsally with 30–32 setae, ventrally with 28–30 setae, distal setae slightly longer than proximal setae, longest seta (33 μm) 1.5 times longer than shortest seta (20 μm), 0.4-fold of greatest width of cercus and 0.1-fold length of cercus. Distal-most portion of cercus almost cylindrical, terminal area 0.2-fold shorter than length of cercus. Apical setae pointed, longer seta 0.3-fold of greatest width and 0.1-fold length of cercus, shorter seta lost. Cuticle with pubescence.

Distribution. China (Guangxi). Only known from the type locality.

Remarks. The new species Millotellina bambusinus sp. n. is similar to M. reducta Jupeau, 1957 and M. monteithi Naumann & Scheller, 1977 in having unpaired median ventral processes inserted between the coxal sacs of legs 5–10. It differs from M. reducta in the shape of the cerci (narrowed abruptly in the distal part and 3 times as long as wide in M. bambusinus sp. n. vs. very sharp and 4 times as long as wide in M. reducta ), the shape of the median ventral processes (with coniform end in bambusinus sp. n. vs. with round end in M. reducta ) and the chaetotaxy of the first tergite (four setae in bambusinus sp. n. vs. two setae in reducta ). It can be easily distinguished from M. monteithi by the shape of the median ventral processes (broad, 1.4–1.7 times as long as basal wide in bambusinus sp. n. vs. elongate, 2 times as long as basal wide in M. monteithi ), the shape of the setae on tergites (with only normal setae in bambusinus sp. n. vs. with some lanceolate setae in M. monteithi ), and the distribution of the pubescence on the tergites (on both anterior and posterior parts in bambusinus sp. n. vs. only on the anterior parts in M. monteithi ).

Etymology. The species name bambusinus indicating its habitat bamboo forest.

The 11 species of the genus Millotellina can be distinguished by the following key.

Figures

FIGURES 23–36. Millotellina bambusinus sp. n. 23. Head, dorsal view, white arrow shows central rod, black arrows show longest setae; 24. Ventral view of head, shows maxilla; 25. Tömösváry organ left side; 26. Apical segment of antenna; 27. Tergites 1 and 2; 28. Tergite 3; 29. Part of tergite 3, shows shape of setae; 30. Median ventral process between coxal sacs leg 5; 31–36. Median ventral processes between coxal sacs of leg 5–10, amplified. Scale bars: 50 µm.

FIGURES 37–43. Millotellina bambusinus sp. n. 37. Mandible, left side; 38. First maxilla, left side; 39. Antennal segments 3–5, dorsal view, arrows show spatulate organs; 40. Basal two segments of leg 1, lateral view; 41. Tibia and tarsus of leg 1, ventral view; 42. Leg 12, dorsal view; 43. Cercus, dorsal view. Scale bars: 50 µm.