Millotellina centralis, 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 : 216-220

Millotellina centralis new species

Figs. 1–22

Material examined: Type specimens. Holotype, male (slide no. GX-JX-SY2018020) ( SNHM), China, Guangxi Province, Baise City, Jingxi County, Tongling Large Barranca , soil of broad-leaved forest, alt. 730 m, 23°1'N, 106°39'E, 5-IX-2015, coll. Y. Bu. Paratypes : 4 females (slides nos. GX-JX-SY2018014, GX-JX-SY2018015, GX- JX-SY2018022, GX-JX-SY2018024) ( SNHM), 5 males (slides nos. GX-JX-SY2018018, GX-JX-SY2018019, GX-JX-SY2018021, GX-JX-SY2018025, GX-JX-SY2018026) ( SNHM), same locality data as holotype . Non-type materials ( SNHM) : 2 juveniles with 11 pairs of legs (slides nos. GX-JX-SY2018016, GX-JX-SY2018017), 2 juveniles with 9 pairs of legs (slides nos. GX-JX-SY2018017, GX-JX-SY2018031), 1 juvenile with 8 pairs of legs (slide no. GX-JX-SY2018027), 1 juvenile with 7 pairs of legs (slide no. GX-JX-SY2018023), same locality data as holotype .

Diagnosis. Millotellina centralis sp. n. is distinct from other Millotellina species based on the following combination of characters: single median ventral processes posterior to each pair of the coxal sacs of legs 4–10, located half-way between successive pairs of legs and situated in the center; and the frontal seta on leg 1 which is thick and nearly same length as the posterior claw.

Description. Adult body averaging 4.66 mm long (3.50–4.64 mm, n=10), holotype 4.2 mm.

Head: length 410–560 μm, width 460–590 μm, broadest part just posterior to middle ( Fig. 1 ). Dorsally covered with straight setae of unequal length. Longest seta (63–73 μm) inserted in front of lateral angle, 0.6–0.7-fold shorter in length than first antennal segment diameter (88–113 μm). Three prominent setae of oblique post-antennal row longer than posterior setae, and about same length as longest lateral angle setae. Dorsal cuticle glabrous. Mesh-work of cuticular thickenings observed at anterior part of head, around base of antennae and lateral and posterior part of head. Central rod (100–113 μm) 0.18–0.24-fold shorter than length of head, terminating posteriorly in prominent ovoid swollen end ( Fig. 1 ); distance between swollen end and posterior margin of head (68–113 μm) 0.14–0.23- fold shorter than length of head. Tömösváry organ: subspherical, length 28–38 μm, width 20–33 μm, at least 0.2–0.3-fold less than greatest diameter of first antennal segment ( Fig. 3 ). Mouthparts: Mandible with 8 pointed, separated teeth and 4 blunt, fused teeth ( Fig. 16 ). Inner lobe of first maxilla with 3 exterior thick teeth and 4 slender hook-shaped interior teeth; palp conical, with broad base, sharply pointed, about 2 times as long as its basal width ( Fig. 17 ). Anterior part of second maxilla with many small protuberances each carrying one seta, including 3 pairs of thickened setae distally, posterior part with numerous setae. Cuticle of maxilla covered with scaly thickenings ( Fig. 2 ). Antennae: with 21–33 segments (holotype with left and right antenna 24 and 25 segments respectively). Antennal base short, densely granulated. First antennal segment 1.3–2.2 times wider than long (88–113 μm width: 43–88 μm length), primary whorl with 6–8 setae, longest dorsal seta 0.4–0.5-fold shorter than segment width. Second antennal segment 1.5–2.0 times wider than long (63–93 μm width: 40–48 μm length), with primary whorl of 9–11 setae, longest seta inserted outer-dorsally, its length about 0.5–0.7-fold less than segment width, two inner setae 0.9-fold length of longest outer setae. Third antennal segment 1.4–1.8 times wider than long (65–83 μm width: 43–50 μm length), with primary whorl of 10–12 setae, longest seta 0.6–0.7-fold shorter than segment width. Proxi- mal antennal segments each with only primary whorl of setae. Secondary whorl begins on antennal segments 6–9, tertiary whorl begins on antennal segments 12–16. Spatulate organs present on dorsal side of antennal segments 3–5 ( Fig. 18 ). Small spined organs present on dorsal side from antennal segment 3 onwards distally. Specialized sensory setae present from middle antennal segment distally: one on middle segments, two or three on subapical ones ( Fig. 19 ). Apical antennal segment wider than long (60–83 μm width: 43–55 μm length), distal half with 20–25 straight setae, the longest one about half as long as greatest width of segment. Apical antennal segment with one large apical spined organ on elevated base, about half as long as segment, and two small spined organs inserted lateraly ( Fig. 4 ). Scale-like cuticular thickenings present on segments 1, 2; mainly transverse. Pubescence present on all antennal segments. Tergites: First tergite rudimentary, with 2–4 thick setae. Second tergite complete, 1.9–2.4 times wider than long (320–400 μm width: 160–210 μm length), posterior margin straight or somewhat convex ( Fig. 5 ). An- terolateral macrochaetae (113–145 μm) length 1.2–1.4 times longer than diameter of antennal segment 1. Posterior margin with 19–24 setae, longest one (50–78 μm) and shortest one (18–28 μm) 0.4–0.6-fold and 0.2-fold shorter in length of anterolateral macrochaetae respectively. Posterior half with numerous unequal length setae (10–25 μm), 0.3–0.7-fold shorter than longest posteromarginal setae. Anterior half with short pubescence on mesh-work covered cuticular thickenings, posterior half with short pubescence. Third tergite 1.8–2.1 times broader than long (410–510 μm width: 200–260 μm length), posterior margin straight or slightly convex, with 25–34 posteromarginal setae, chaetotaxy similar to second tergite, some setae lanceolate ( Figs. 5, 7 ). Tergite 4 broader than tergite 3 ( Fig. 6 ). Anterolateral macrochaetae present on tergites 2, 3, 4, 6, 7 and 9. All tergites with short pubescence on scale-like cuticular thickenings on anterior part. Some setae on tergites distinctly lanceolate ( Fig. 7 ). Leg 1: with four segments. Tarsus 4.0– 4.8 times longer than wide (140–175 μm length: 30–38 μm width), tapering distally, with 20–25 setae in total, length of setae increasing distally; distal-most dorsal seta longest, its length 0.9–1.2-fold of greatest width of segment. Anterior claw slightly curved, more robust than posterior claw, its length 0.2-fold less than length of tarsus, about 2.0 times longer than posterior claw. Frontal seta thick and nearly same length of posterior claw ( Fig. 20 ). Tibia 1.1–1.7 times longer than wide (55–63 μm length: 38–58 μm width), with 5–7 dorsal setae and short pubescence on scale-like cuticular thickenings on dorsal side of segment. Proximal segment 1.3–2.0 times longer than wide (80–125 μm length: 58–75 μm width), dorsal side glabrous with scale-like cuticular thickenings; ventral side with many short setae and four long setae, longest seta 0.7-fold longer than greatest width of segment ( Figs. 9 , 20 ). Leg 12: with five segments ( Figs. 10 , 21 ). Tarsus 4.2–5.1 times longer than wide (170–225 μm length: 35–50 μm width), proximally subcylindrical, tapering distally, dorsally with three longitudinal rows of setae, each includes 5–7 setae, two distal rather erect, longest one 0.8–0.9-fold shorter than greatest width of segment. Tarsus ventrally with three longitudinal rows of setae, each consisting of 3–6 setae. Anterior claw about 0.2-fold shorter than length of tarsus, 1.2–1.3 times longer than posterior claw; posterior claw more curved than anterior claw. Frontal seta short. Tibia 1.9–2.4 times longer than wide (133–200 μm length: 63–93 μm width), dorsally with three longitudinal rows of setae, each row with 4–6 robust appressed setae, length of longest dorsal seta 0.4–0.6-fold shorter than greatest width of segment. Tibia with several fine setae on ventral surfaces. Femur 1.0–1.3 times longer than wide (85–120 μm length: 75–108 μm width). Femur with longest setae on lateral side, 0.3–0.6 shorter than greatest width of seg- ment. Trochanter 1.4–1.6 times longer than wide (150–200 μm length: 85–133 μm width), with numerous fine setae on ventral surface. Tarsus and tibia with rather uniform pubescence on mesh-work covering of cuticular thickenings. Ventral side of femur and trochanter with pubescence on cuticular thickenings, dorsal side glabrous, with scaly cuticular thickenings. Male genitalia: with 50–65 setae in total, including 4 pairs of specialized sensory setae close to genital opening ( Fig. 15 ). Styli: present at bases of legs 3–12, 2.9–3.8 times longer than basal width (50–63 μm length: 15–20 μm width). Styli pubescent, with two distal setae, longer seta 0.4–0.6-fold shorter than length of stylus, apex blunt; shorter seta 0.2–0.3-fold less than length of longer seta, apex pointed ( Fig. 8 ). Coxal sacs: present at bases of legs 3–9, fully developed, each with 5–7 setae ( Figs. 11–13 ). Areas corresponding to coxal sacs at bases of legs 1, 2, 10, 11, 12 replaced by 0, 4–6, 2–3, 2–3, 1–2 setae, respectively. Coxal plates of leg 1 without setae, those of legs 2, 3–9, 10, 11, 12 with 2–8, 6–17, 8–10, 5–11, and 3–5 setae, respectively ( Figs. 11–13 ). Median ventral processes: unpaired, subconical, apex blunt, located posterior to coxal sacs of legs 4–10, half-way between successive pairs of legs and located in center. Median ventral processes 1.1–2.0 times longer than width of the base (38–65 μm length: 23–45 μm width), as long as or somewhat shorter than stylus. Cuticle covered with fine dense curved pubescence ( Figs. 11–14 ). Cerci: 3.4–4.8 times longer than wide (340–445 μm length: 73–125 μm width), 0.1-fold shorter than length of body, covered with dense setae except ventral proximal part ( Figs. 10 , 22 ). Cerci dorsally with 36–48 setae, ventrally with 25–48 setae; longest seta (33–38 μm) 1.7–1.9 times longer than shortest seta (18–23 μm), 0.3–0.4-fold less than greatest width of cercus and 0.1-fold shorter than length of cercus. Distal-most portion of cercus almost cylindrical, terminal area 0.1–0.2-fold less than length of cercus. Two apical setae pointed, longer seta 0.8–1.3 times as long as wide and 0.2–0.3-fold less than length of cercus. Shorter seta about one third length of longer one. Cuticle with pubescence.

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

Remarks. The new species Millotellina centralis sp. n. has unpaired median ventral processes indicating a close affiliation to the nominate subgenus Millotellina , but can be easily distinguished from the other eight known members of the subgenus by the location of the processes which are located posterior to the coxal sacs of legs 4–10 (between the coxal sacs of legs 5–10/ 11 in others). The location of the median ventral processes in Millotellina centralis sp. n. is similar to M. bidens of the subgenus Diplomillotellina , but the latter has a pair of processes posterior to each pair of coxal sacs of legs 5–9.

Etymology. The species name centralis refers to the location of the median ventral processes, which are in a central position between successive pairs of legs.

Figures

FIGURES 1–15. Millotellina centralis sp. n. 1. Head, dorsal view, arrow shows central rod; 2. Ventral view of head, shows maxilla; 3. Tömösváry organ, left side; 4. Apical segment of antenna; 5. Tergite 2 and 3; 6. Tergite 4 and 5; 7. Part of tergite 3, shows lanceolate setae; 8. Stylus associated with leg 5; 9. Leg 1 on right; 10. Leg 12 and cercus, left side; 11. Median ventral process posterior to leg 4; 12. Male genitalia, styli, coxal sacs and median ventral process posterior to leg 4; 13. Styli, coxal sacs and median ventral process posterior to leg 5; 14. Median ventral process posterior to leg 4, amplified; 15. Male genitalia, arrows show specialized sensory setae. Scale bars: 50 µm.

FIGURES 16–22. Millotellina centralis sp. n. 16. Mandible, left side; 17. First maxilla, left side; 18. Antennal segment 4, dorsal view, arrow shows spatulate organs; 19. Antennal segment 14, dorsal view, arrows show one spined sensory organ and two specialized sensory organs; 20. Leg 1, lateral-ventral view; 21. Leg 12, ventral view; 22. Cercus, ventral view. Scale bars: 50 µm.