Otostigmus (Otostigmus) xizangensis, Niu & Li & Di, 2021

Niu, Meilian, Li, Yixuan & Di, Zhiyong, 2021, Otostigmus (Otostigmus) xizangensis n. sp., from China and a case of sexual dimorphism in the subgenus Otostigmus (Otostigmus) Porat, 1876 (Chilopoda, Scolopendromorpha, Scolopendridae), Zootaxa 5081 (2), pp. 295-300 : 296-299

Otostigmus (Otostigmus) xizangensis n. sp.

Figs 1–18

Material examined. Holotype, ♂ ( Ar. -MHU-SoBM1705250501, figs 1, 2, 5, 6, 8, 10–13): Bomi County, Xizang, China, lat. 30°06′, long. 95°06′, 25/5/2017, leg. Zhiyong Di. Paratypes, (4 males, 5 females and 4 immatures: Ar. -MHU-SoBM1705250502–14, figs 3, 4, 7, 9, 14–15): Bomi County, Xizang, China, lat. 30°06′, long. 95°06′, 25/5/2017, leg. Zhiyong Di; (1 male, 2 females and 1 immature: Ar. -MHU-SoBM1705250101–04) , Taohua ditch, Bomi County, Xizang, China, lat. 29°57′, long. 95°38′, 25/5/2017, leg. Zhiyong Di ; dissected specimens (2 males and 2 females: Ar. -MHU-SoBM1705250515–18, figs 16–18): Bomi County, Xizang, China, lat. 30°06′, long. 95°06′, 25/5/2017, leg. Zhiyong Di.

Etymology. The specific epithet refers to the locality where the specimen was collected. The prefecture name “xizang” is compounded with the suffix “ensis”.

Diagnosis. Tergites grayish-blue to dark green (in 75% ethanol). Body length up to 53 mm. Antennae 17–19 articles (mainly 19), ca 2.4 basal ones glabrous dorsally and ca 2.2 ones ventrally, basal articles cylindrical, definitely longer than wide. Forcipular tooth-plate with 4 teeth; trochanteroprefemur with long process, with two median tubercles. Tergites (5) 6–20 with complete paramedian sutures; well-developed lateral margination on tergites (6) 9–21. Sternite 21 narrowed towards the slightly concave posterior margin, with posterior longitudinal median depression. Legs 1–16 with two tarsal spurs. Coxopleural process of female long and curved, male coxopleural process short and straight.

Description of Holotype (♂)

Length of holotype about 51 mm (anterior margin of cephalic plate to posterior margin of tergite 21) ( Figs 1, 2 ).

Color (in 75% ethanol for 4 years): antennomeres l–10 dark blue, 11–19 pale green ( Fig. 5 ); head sapphire blue dorsally, red-brown ventrally; tergites (TT) 1–2, sternites (SS) 1–2 dark blue to grayish-blue; TT3–21, SS3–21, and all legs dark green; margin of coxosternal tooth plates, coxopleuron, tibial and tarsal spurs, and distal parts of pretarsus red-brown.

Antenna: 19 articles, extending to nearly the posterior margin of T4 when reflexed. Basal 2.3 to 2.4 articles glabrous dorsally ( Figs 6, 8 ) and ca 2.2 ones ventrally, subsequent articles densely pilose. Basal articles cylindrical, definitely longer than wide.

Cephalic plate: approximately rounded and without sutures, its posterior margin overlapped by T1 ( Fig. 6 ).

Forcipular segment: tooth-plates 4 + 4 ( Fig. 8 ), lateral tooth much smaller than the others. The basal sutures of tooth-plates form an obtuse angle, their lateral ends bifurcate. Trochanteroprefemur with a large process, with two median tubercles; this process extends much beyond the tooth-plates. Tarsungula long, their inner surface rounded.

Tergites (T): T2 very short (only as long as 1/2 of T1) ( Figs 1 ). TT1–3 without sutures; T4 with incomplete paramedian sutures in the posterior half, TT5–20 with complete paramedian sutures and well-developed ( Fig. 10 ). TT5–20 with a median keel ( Fig. 10 ), which is incomplete on ultimate tergite. Ultimate tergite much narrower than T20, somewhat wider than long, without median suture, with a posterior median depression ( Fig. 12 ). Lateral margination virtually absent on TT6–7, incomplete on T8, complete and well-developed on TT9–20 and ultimate tergite.

Sternites (S): SS5–21 narrowed posteriorly ( Fig. 11 ), SS4–19 with very short, poorly-developed paramedian sutures anteriorly. S1 with shallow median depression, SS2–3 with two hardly visible longitudinal (paramedian) depressions in the middle. SS4–20 with three longitudinal depressions in the middle. Ultimate sternite (S21) somewhat wider than long, distinctly narrowed towards the slightly concave posterior margin, with longitudinal median depression in the posterior half ( Fig. 13 ).

Coxopleural process: relatively long, surface without setae, with sharp tip. Coxopleuron considerably longer than ultimate sternite, almost completely covered with coxal pores of various sizes ( Fig. 13 ), with two/three apical, one lateral and two dorsal spines. Pore field extending near to posterior margin of coxopleuron ( Figs 12–13 ).

Legs (L): L1–5 each with one tibial spur near distal end of tibia; L6–20 without tibial spur. Two tarsal spurs on L1–16, L17–20 with one tarsal spur.

Ultimate legs glabrous, all articles (prefemur, femur, tibia, tarsus 1, tarsus 2) cylindrical. Pretarsus welldeveloped. Prefemur with four rows of spines, each on a prominent base. Prefemoral spines: VL 4, VM 2, M 3, DM 2, CS 1 ( Fig. 13 ).

Variation in paratypes.

Body length 48–53 mm (the largest of specimens, figs 3, 4) in adults. Antennae mainly of 19 articles (one adult ♀ with 18 left and 17 right articles). Both topography and structure of the setae at the antennal articles identical to that of the holotype ( Fig. 7 ). Forcipular tooth-plate with 4 teeth, the outer two teeth coalesced in one adult female ( Fig. 9 ).

In the paratypes, tergite 5 has very short (1/4 of tergite length) paramedian sutures posteriorly, TT6–20 with complete paramedian sutures. Median keel essentially as in the holotype; lateral margination on TT(6) 7–21 in the paratypes.

Sternites (4)5–(17)19 with much shortened anterior paramedian sutures; configuration and topography of sternal depressions virtually the same as in the holotype.

Coxopleural process bearing 2/3 apical spines, 1/2 lateral and 1/2 dorsal spines; ultimate leg prefemoral spines arranged as VL 3/4, VM 2, M3, DM 1/2, CS 1 ( Figs 14–17 ).

Sexual dimorphism.

In O. (O.) xizangensis n. sp., there are two notably different shapes of the coxopleural process among 22 specimens, one long and curved, the other short and straight. We inferred the existence of sexual dimorphism in this new species. We dissected two males and two females, finding that the individuals with a short and straight coxopleural process are relatively small, and they have some pairs of testes ( Fig. 18 ) and vas deferens and are therefore males; while the individuals with a long and curved coxopleural process contain ovaries and are thus females. In immatures, coxopleural process slender and straight, unable to distinguish sexual dimorphism.

Distribution. Known only from the type locality ( Fig. 19 ).

Figures

FIGURE 19. Distribution of Otostigmus Porat 1876 in Xizang. a: star, O. (O.) xizangensis n. sp. Bomi County. b: circle, O. (O.) beroni, Jilong Town, Jilong County. c: square, O. (O.) martensi, Nielamu County.

FIGURES 1–4. O. (O.) xizangensis n. sp., habitus. 1–2: Holotype, adult male, dorsal and ventral views. 3–4: Paratype, Ar.- MHU-SoBM1705250502, adult female, dorsal and ventral views. Scale bars of figs 1–4: 10.0 mm.

FIGURES 5–18. O. (O.) xizangensis n. sp., Holotype (figs 5, 6, 8, 10–13); Paratype (Ar.-MHU-SoBM1705250502, figs 7, 9, 14, 15; the dissected female, Ar.-MHU-SoBM1705250515, fig. 16; the dissected male, Ar.-MHU-SoBM1705250516, figs 17–18) 5: Head and tergite 1, dorsal view; 6–7: Cephalic plate, dorsal view; 8–9: Forcipular segment, ventral view; 10–11: Legbearing segments 13–17, dorsal and ventral views; 12–15: Ultimate leg-bearing segment and ultimate legs, dorsal and ventral views; 16–17: Ultimate leg-bearing segment and ultimate legs, ventral view; 18: Three pairs of testes. Scale bar (6, 8, 9, 12): 1 mm, scale bars (5, 7, 10, 11, 13–18): 2 mm. Abbreviations: (bs)—basal suture of tooth-plate, (gp)—glabrous basal portion of antennal article 3, (pt)—process of trochanteroprefemur (tp)—tooth-plate, (md)—median depression, (mk)—tergal median keel, (S17)—sternite 17, (us)— ultimate sternite, (cp)—coxopleural process.