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Research Article
Six new species of dragon millipedes, genus Desmoxytes Chamberlin, 1923, mostly from caves in China (Diplopoda, Polydesmida, Paradoxosomatidae)
expand article infoWeixin Liu, Sergei Golovatch§, Mingyi Tian|
‡ Agricultural University, Guangzhou, Guangdong Province, China
§ Russian Academy of Sciences, Moscow, Russia
| South China Agricultural University, Guangzhou, China
Open Access

Abstract

Six new species of Desmoxytes are described from southern China: D. laticollis sp. n., D. simplipoda sp. n., and D. similis sp. n., all three from caves in Guangdong Province; D. phasmoides sp. n. also from a cave, and both epigean D. spiniterga sp. n. and D. variabilis sp. n., the latter trio from Guangxi Zhuang Autonomous Region. A modified key to all 20 Desmoxytes species currently known to occur in China is given.

Keywords

Desmoxytes, new species, troglobite, key, southern China

Introduction

Millipedes in the genus Desmoxytes Chamberlin, 1923, belong to the tribe Orthomorphini, subfamily Paradoxosomatinae, family Paradoxosomatidae (Golovatch et al. 2012) and are often referred to as “dragon millipedes”. This genus is conspicuous in its species generally showing a dragon-like appearance, with strongly wing-, spine- or antler-shaped paraterga. Desmoxytes was first revised by Golovatch and Enghoff (1994), very recently reviewed by Likhitrakarn et al. (2015) to comprise 35 described species ranging from southeastern China south through Laos, Vietnam and Myanmar to southern Thailand and Western Malaysia. Only one species, D. planata (Pocock, 1895), has attained a nearly pantropical distribution through commerce.

The dragon millipede fauna of China has also been summarized, keyed and shown to contain 14 species, including all 11 congeners hitherto known from caves (Golovatch et al. 2010, 2012, Liu et al. 2014, Golovatch 2015). Most of the cavernicolous Desmoxytes look highly troglomorphic and show spiniform paraterga.

The following 14 species are currently known to occur in mainland China, arranged in alphabetic order:

D. cornutus Zhang & Li, 1982, from Guangxi, Guilin, Yangshuo.

D. draco Cook & Loomis, 1924, from Jiangxi, Jiujiang, Lushan Mountain.

D. eupterygota Golovatch, Li, Liu & Geoffroy, 2012, from two caves in Hunan, Chenzhou, Linwu.

D. getuhensis Liu, Golovatch & Tian, 2014, from two caves in Guizhou, Ziyun, Getuhe National Geopark.

D. lingulata Liu, Golovatch & Tian, 2014, from Guangxi, Guilin, Pingle, Chaotianyan.

D. longispina Loksa, 1960, from a cave in Guangxi (an exact locality unknown).

D. lui Golovatch, Li, Liu & Geoffroy, 2012, from a cave in Guangxi, Yongfu.

D. minutubercula Zhang, 1986, from Guangxi, Tianlin.

D. nodulosa Liu, Golovatch & Tian, 2014, from several caves in Guangxi, Hechi, Du’an.

D. parvula Liu, Golovatch & Tian, 2014, from Guangxi, Du’an, Xia’ao.

D. planata (Pocock, 1895), from a cave in Yunnan, Luxi, but actually nearly pantropical.

D. scolopendroides Golovatch, Geoffroy & Mauriès, 2010, from a cave in Guangxi, Huanjiang and several caves in Du’an.

D. scutigeroides Golovatch, Geoffroy & Mauriès, 2010, from several caves in Guangxi, Huanjiang and Du’an.

D. spinissima Golovatch, Li, Liu & Geoffroy, 2012, from a cave in Guangxi, Fuchuan.

The present paper describes another six new species of Desmoxytes from southern China, including four presumed troglobites. Three of the new species are the first to be recorded in Guangdong Province, whereas a further three are from Guangxi Zhuang Autonomous Region which alone has already been known to support seven troglobitic species. Altogether, 20 species of Desmoxytes have now been recorded from China.

Material and methods

The holotypes and a number of paratypes are deposited in the zoological collection of the South China Agricultural University, Guangzhou, China (SCAU), with some duplicates (paratypes) housed also in the Zoological Museum Alexander Koenig, Bonn, Germany (ZFMK), and the Zoological Museum, State University of Moscow, Russia (ZMUM).

Observations and dissections were performed using an Olympus SZ51 stereo microscope. The line drawings were prepared with the help of an Olympus SZX12 stereo microscope and a camera lucida attached to the scope. The photographs were taken with Canon EOS 40D and 7D cameras, further processed using Adobe Photoshop CS5 software.

The methods and terminology used here are after Golovatch et al. (2012).

Taxonomic part

Desmoxytes laticollis sp. n.

Figs 1A–B, 2, 3

Holotype

♂ (SCAU), China, Guangdong, Qingyuan, Yingde Shi, Huanghua Xiang, Yanbei Cun, Cave Yangyan Dong, 24°18'32"N, 112°47'20"E, ca 450 m a.s.l., 2014-XII-30, leg. Mingyi Tian, Weixin Liu, Sunbin Huang & Xinhui Wang.

Paratypes

13 ♂, 7 ♀ (SCAU), 1 ♂, 1 ♀ (ZMUM), 1 ♂, 1 ♀ (ZFMK), same locality and collecting data as the holotype.

Name

To emphasize the collum being the broadest segment; adjective.

Diagnosis

Keys out to the superficially most similar D. eupterygota Golovatch, Li, Liu & Geoffroy, 2012 (Liu et al. 2014), especially so concerning metatergal ornamentation and a condensed solenophore, but differs by the collum being the broadest segment, as well as the femora, postfemora and tibiae conspicuously clavate in both sexes.

Description

Length ca 26–27 mm (♂) or 28–29 mm (♀), width of midbody pro- and metazonae 2.0 and 2.5 (♂) or 2.2 and 2.5 mm (♀), respectively. Holotype 26 mm long, 2.0 and 2.5 mm wide on midbody pro- and metazonae, respectively, maximum width on collum 3.5 mm. In width, head < segment 8–16 < 5–7 < 4 < 3 < 2 < collum; starting with segment 17, body gradually tapering towards telson (Fig. 2). Live coloration rather uniformly yellowish to pallid (Fig. 1A–B). Head sparsely setose, epicranial suture distinct (Fig. 2A–B). Antennae long and slender, reaching back until posterior margin of segment 5 (♂) or middle of segment 4 (♀) when stretched dorsally; antennomeres 5 and 6 each with a compact apicodorsal group of bacilliform sensilla.

Figure 1.

In vivo photographs. A–B a mating couple of Desmoxytes laticollis sp. n. C–D ♂ and ♀, Desmoxytes simplipoda sp. n. E–F 2 ♀, Desmoxytes similis sp. n. G ♂, Desmoxytes phasmoides sp. n. H ♂, Desmoxytes variabilis sp. n.

Figure 2.

Desmoxytes laticollis sp. n., ♂ paratype from Cave Yangyan Dong. A–B anterior part of body, dorsal and ventral views, respectively C–D midbody segments, dorsal and ventral views, respectively E–F posterior part of body, dorsal and ventral views, respectively.

Body with 20 segments. Tegument (Fig. 2) very strongly shining, prozonae faintly microalveolate; surface below paraterga of collum and those of segments 2–4 finely microgranulate. Collum (Figs 2A, 3A) with at least 2+2 setae at front margin, another 1+1 setae in the middle, hardly visible; paraterga on collum particularly strongly developed, wing-shaped, lying a little below a rather convex collum; paraterga on segments 2–4 clearly elevated above dorsum, thereafter rather poorly-developed, relatively small and crest-shaped, lying slightly below level of a faintly convex dorsum until segment 18, vestigial and lying far below level of a strongly convex dorsum on segment 19 (Fig. 2A, C, E); paraterga 1–4 with three especially strong denticles at lateral margin, two anterior of the denticles gradually disappearing towards segment 7, but caudalmost tooth persisting until segment 18 (Fig. 2A, C, E). Metaterga 2–4 each with 1+1 setae in anterior row; each of metaterga 5–19 additionally with 1+1 setae in posterior row, mostly poorly visible; paraterga a little more strongly developed in ♂ than in ♀, calluses very thin in poreless segments, slightly thicker in pore-bearing ones. Stricture between pro- and metazonae very narrow and deep. Ozopores entirely lateral, lying on top of caudal tooth on pore-bearing paraterga (Fig. 2A, C, E). Transverse sulcus evident and deep, smooth at bottom, reaching bases of paraterga on segments 7–16, incomplete (not reaching the bases of paraterga) in segments 5–6 and 17–18, vestigial in segment 19 (Fig. 2A, C, E). Epiproct subconical, clearly flattened dorsoventrally, mostly broad, subtruncate at a narrow apex, subapical lateral setae not borne on knobs (Fig. 2E–F). Hypoproct subtrapeziform, clearly emarginate at caudal margin, caudal setae distinctly separated (Fig. 2E–F). Pleurosternal carinae poorly-developed, only visible on segments 2 and 3 both in ♂ and ♀. Axial line missing.

Figure 3.

Desmoxytes laticollis sp. n., ♂ paratype from Cave Yangyan Dong. A collum, dorsal view B sternal processes between coxae 4, ventral view C–D right gonopod, lateral and mesal views, respectively.

Sterna sparsely setose, nearly flat, cross-impressions shallow, axial groove being especially superficial (Fig. 2B, D, F). A pair of paramedian, densely setose, low cones between ♂ coxae 4 (Figs 2B, 3B). Legs 1 short, following ones growing slightly, but increasingly long and slender towards telson, midbody legs ca 2.5 (♂) or 2.0 (♀) times as long as body height; femora, postfemora and tibiae conspicuously clavate distad, neither tarsal brushes nor adenostyles in ♂ and ♀ (Fig. 2).

Gonopods (Fig. 3C–D) suberect. Coxite short, subcylindrical, sparsely setose distodorsally, nearly 1/3 as long as telopodite. Prefemur densely setose, almost half as long as acropodite. Femorite long, slightly curved ventrad. Solenophore (sph) clearly condensed and divided into a large rectangular lobe on lateral side (= lamella lateralis, ll) and a distinct coiled part on mesal side (= lamella medialis, lm). Seminal groove running entirely on mesal side of femorite before entering onto a short, but evident and flagelliform solenomere (sl), the latter lying between ll and lm.

Remark

Because of the pallid tegument and remarkably elongated antennae and legs, this species is most probably a troglobite.

Desmoxytes simplipoda sp. n.

Figs 1C–D, 4, 5

Holotype

♂ (SCAU), China, Guangdong, Qingyuan, Yangshan Xian, Chengjia Xiang, Dabei Cun, Cave Kuangzhanyan, 24°46'28"N, 112°48'16"E, ca 140 m a.s.l., 2014-XII-28, leg. Mingyi Tian, Weixin Liu, Sunbin Huang & Xinhui Wang.

Paratypes

1 ♂, 6 ♀ (SCAU), same locality and collecting data as the holotype.

Name

To emphasize the legs being simple, devoid of modifications; adjective.

Diagnosis

Using the latest key (Liu et al. 2014), this new species keys out to the superficially most similar D. longispina (Loksa, 1960), especially so due to spiniform paraterga and a condensed solenophore, but differs by the legs being devoid of modifications.

Description

All characters as in D. laticollis sp. n., except as follows.

Length ca 28–29 mm (♂) or 31–33 mm (♀), width of midbody pro- and metazonae 1.8 and 4.0 (♂) or 2.5 and 4.5 mm (♀), respectively. Holotype 29 mm long, 1.8 and 4.0 mm wide on midbody pro- and metazonae, respectively. In width, head < segment 2–4 < collum < 5–16. Coloration (Fig. 1C–D) varying from dark brownish to nearly pallid, anterior part of body a little darker than posterior part. In holotype, head, as well as dorsal and both lateral sides of metaterga dark brownish; prozonae, paraterga, sterna, and legs pallid to yellowish (Fig. 4); apices of antennomeres 6 and 7 dark brownish (Fig. 1C–D). Antennae very long and slender, reaching back until posterior margin of segment 6 (♂) or segment 5 (♀) when stretched dorsally.

Figure 4.

Desmoxytes simplipoda sp. n., ♂ holotype from Cave Kuangzhanyan. A–B anterior part of body, ventral and sublateral views, respectively C–D midbody segments, dorsal and lateral views, respectively E–F posterior part of body, dorsal and lateral views, respectively.

Prozonae very delicately microalveolate, metazonae rather finely shagreened and microgranulate (Fig. 4). Collum (Fig. 4A) with 3+3 evident setigerous spinules at fore margin, at least 1+1 much smaller spinules in the middle and 2+2 strongly enlarged spines (paramedian spines being larger than others) at posterior margin; following metaterga 2–18 showing a pattern of smaller 2+2 posterior spinules with invariably obliterated setae (paramedian two spinules a little larger, the other two located at base of each paratergum), while metaterga 19 with 1+1 posterior spinules (Fig. 4C, E). Paraterga (Fig. 4) very strongly developed, spiniform, on collum with four evident anteromarginal denticles; all following paraterga long, straight, also spiniform, about as high as metatergal height in ♂, a little shorter in ♀; paraterga 2–18 with 2–3 evident denticles frontally. Paraterga 2–9 directed more dorsad than laterad, nearly erect above dorsum; following paraterga directed a little caudad, but ending up clearly above dorsum. Ozopores conspicuous, located a little above first denticle from lateral side of pore-bearing paraterga (Fig. 4B–F). Transverse sulcus present on segments 2–19, but complete and reaching bases of paraterga only on segments 6–15 (Fig. 4C, E).

Sterna sparsely setose, cross-impressions evident. A large, median, sparsely setose process with two small pores at base between ♂ coxae 4 (Figs 4B, 5A). Legs devoid of modifications (Fig. 4A–B), ca 2.8–3.0 (♂) or 2.5 (♀) times as long as midbody height.

Figure 5.

Desmoxytes simplipoda sp. n., ♂ holotype from Cave Kuangzhanyan. A sternal process between coxae 4, ventral view B–C entire right gonopod and its distal half, mesal and lateral views, respectively.

Gonopods (Fig. 5B–C) simple. Coxite stout, about 1/3 as long as telopodite. Prefemur short, less than half the length of acropodite. Femorite long, suberect. Solenophore strongly condensed and divided into a large subtriangular lamella lateralis (ll) and a terminally evidently bifid lamella medialis (lm).

Remark

Judging by the extremely elongated antennae and legs, this species seems to be a troglobite.

Desmoxytes similis sp. n.

Figs 1E–F, 6, 7

Holotype

♂ (SCAU), China, Guangdong, Qingyuan, Yingde Shi, Qingkeng Zhen, Bangjiao Cun, Cave Bangjiao Dong, 24°25'09"N, 112°57'16"E, ca 230 m a.s.l., 2014-XII-29, leg. Mingyi Tian, Weixin Liu, Sunbin Huang & Xinhui Wang.

Paratypes

1 ♂, 4 ♀ (SCAU), 1 ♂, 1 ♀ (ZFMK), same locality and collecting data as the holotype.

Name

To emphasize the particular similarities to D. simplipoda sp. n.; adjective.

Diagnosis

This species seems to be especially similar to D. simplipoda sp. n., from Yangshan, Qingyuan, Guangdong, but differs by the setose process between ♂ coxae 4 showing a large pore and the lamella medialis of the gonopod solenophore a small lobule at about midlength.

Description

All characters as in D. simplipoda sp. n., except as follows.

Length ca 25–26 mm (♂) or 27–29 mm (♀), width of midbody pro- and metazonae 1.5 and 4.0 (♂) or 2.5 and 4.5 mm (♀), respectively. Holotype 26 mm long, 1.5 and 4.0 mm wide on midbody pro- and metazonae, respectively. In width, head < collum < segment 2–8 < 9–16. Coloration rather uniformly light brownish to pallid (Figs 1E–F, 6).

Figure 6.

Desmoxytes similis sp. n., ♂ holotype from Cave Bangjiao Dong. A–B anterior part of body, subventral and dorsal views, respectively C–D midbody segments, subventral and dorsal views, respectively E–F posterior part of body, ventral and dorsal views, respectively.

Paraterga of collum (Fig. 6A–B) directed laterad; following paraterga 2–18 directed dorsad and a little caudad; paraterga 19 directed caudad, but all paraterga ending up clearly much above dorsum (Fig. 6). Transverse sulcus very vague, only traceable in segments 3–18 (Fig. 6B, D, F).

A large, median, setose process with a large central pore at bottom between ♂ coxae 4 (Fig. 7A). Legs devoid of modifications, about 2.5 (♂) or 2.0 (♀) times as long as midbody height.

Figure 7.

Desmoxytes similis sp. n., ♂ paratype from Cave Bangjiao Dong. A sternal process between coxae 4, ventral view B–C entire left gonopod and its distal half, mesal and lateral views, respectively.

Gonopods (Fig. 7B–C) short. Coxite less than 1/3 the length of telopodite. Prefemur about half as long as acropodite. Femorite very short, slightly enlarged distad. Solenophore strongly condensed and divided into a large subtriangular lamella lateralis (ll) and a terminally evidently bifid lamella medialis (lm), the latter with a very small lobule (l) at about midlength.

Remarks

This species seems to be very similar to D. simplipoda sp. n., from Yangshan, Qingyuan, Guangdong. The only differences are outlined in the above diagnosis. Because of the nearly pallid tegument and extremely elongated antennae and legs, this species seems to be a troglobite.

Desmoxytes phasmoides sp. n.

Figs 1G, 8, 9

Holotype

♂ (SCAU), China, Guangxi, Baise, Lingyun Xian, Jiayou Zhen, Yangli Cun, Cave Fengliu Dong, 2015-VI-9, leg. Mingyi Tian, Weixin Liu, Xinhui Wang & Mingruo Tang.

Paratypes

1 ♂, 1 ♀ (SCAU), 1 ♂ (ZFMK), same locality and collecting data as the holotype.

Name

To emphasize that superficially this new species somewhat resembles a stick insect, Phasmatodea; noun in apposition.

Diagnosis

Keys out to the superficially most similar D. minutubercula Zhang, 1986 (Liu et al. 2014), especially so due to long spiniform paraterga and a particularly condensed solenophore, but differs by a pair of rounded, setose processes present between ♂ coxae 4 and the gonopod lamella medialis showing a distinct spine.

Description

All characters as in D. laticollis sp. n., except as follows.

Length of both sexes ca 27–29 mm, width of midbody pro- and metazonae 1.3–1.5 and 2.8–3.0 mm, respectively. Holotype 29 mm long, 1.5 and 3.0 mm wide on midbody pro- and metazonae, respectively. In width, segment 2–4 < collum < head < 5–7 < 8–18. Coloration rather uniformly light brownish, some metaterga and bases of paraterga pinkish (Fig. 1G). Antennae very long and slender, reaching back until posterior margin of segment 8 (7) (♂) or 6 (♀) when stretched dorsally.

Tegument shining and smooth, prozonae faintly microalveolate; metazonae finely microgranulate (Fig. 8). Collum (Fig. 8A) with at least 6+6 anterior, 4+4 (5) intermediate and 3+3 posterior setigerous spines; paraterga on collum spiniform, directed dorsolaterad, with a setigeous spine anteriorly at distal 1/3 (Figs 8A, 9A). Metaterga 2–4 each with 4+4 anterior, 3+3 intermediate and 5+5 posterior setigerous tubercles; metaterga 5–19 with a pattern of 5+5 setigerous tubercles anteriorly, these occasionally arranged in two transverse rows, as well as 4+4 between paraterga and at least 5+5 setigerous tubercles at posterior margin. Paraterga 2–18 (Fig. 8) extremely long, straight, spiniform, simple, usually with 2–3 very small setigerous denticles on lateral side; only paraterga 19 directed caudad. Ozopores inconspicuous, lying at base of pore-bearing paraterga on lateral side (Fig. 8D). Transverse sulcus incomplete, present on segments 6–18 (Fig. 8B, D, E).

Figure 8.

Desmoxytes phasmoides sp. n., ♂ paratype from Cave Fengliu Dong. A–B anterior part of body, subventral and dorsal views, respectively C–D midbody segments, ventral and dorsal views, respectively E–F posterior part of body, ventral and dorsal views, respectively.

Sterna modestly setose, cross-impressions very shallow (Fig. 8C, E). A pair of paramedian, rounded, setose processes between ♂ coxae 4 (Fig. 9B). Legs long and slender, midbody legs ca 4.5 (♂) or 3.5 (♀) times as long as body height; ♂ femur 6 with a very evident apophysis at distal 1/4 (Fig. 9C).

Figure 9.

Desmoxytes phasmoides sp. n., ♂ paratype from Cave Fengliu Dong. A collum, dorsal view B sternal processes between coxae 4, ventral view C femur 6, front view D–F entire right gonopod and its distal half, mesal, ventral and lateral views, respectively.

Gonopods (Fig. 9D–F) subfalcate. Coxite very short, less than 1/3 as long as telopodite. Prefemur short, less than half as long as acropodite. Femorite rather long, curved ventrad. Solenophore highly condensed, divided into a small, rectangular lamella lateralis and a simple lamella medialis, the latter with a distinct spine (s) at about midlength; solenomere very short and flagelliform.

Remark

Because of the pallid tegument and extremely elongated antennae and legs, this species may well be a troglobite.

Desmoxytes spiniterga sp. n.

Figs 10, 11

Holotype

♂ (SCAU), China, Guangxi, Hechi, Huanjiang Xian, near Cave Gui Dong II, Secondary forest, litter, Berlese extraction after sifting, 2007-V-18, leg. Louis Deharveng & Anne Bedos (CHIgx07-18-17).

Paratype

1 ♂ (SCAU), same locality and collecting data as the holotype.

Name

To emphasize the metaterga showing very evident, spiniform, setigerous paraterga; adjective.

Diagnosis

Keys out to the superficially most similar D. draco Cook & Loomis, 1924 (Liu et al. 2014), judging from the ornamentation of metaterga, but differs by legs showing no modifications, in the metaterga supplied with more numerous setigerous spines, as well as the rather short femorite of the gonopod and the clearly coiled solenophore (cf. Kraus 2012).

Description

All characters as in D. laticollis sp. n., except as follows.

Length ca 11 mm (holotype) or 12 mm (paratype), width of midbody pro- and metazonae 0.5 and 1.8 mm, respectively. In width, head < collum < segment 2–4 < 5–16. Coloration brownish to yellowish (Fig. 10). Antennae very long and slender, reaching back until posterior margin of segment 6.

Figure 10.

Desmoxytes spiniterga sp. n., ♂ paratype from near Cave Gui Dong II. A–B body, dorsal and ventral views, respectively.

Prozonae faintly microalveolate; metazonae rather microgranulate and shagreened. Collum (Fig. 10A) with 4+4(5) anterior, 2+2 intermediate and 2+2 posterior setigerous spines; following metaterga 2–8 with 3+3 anterior and 3(4)+3(4) posterior setigerous spines; in metaterga 9–18 increasingly more numerous, with a pattern of 3(4)+3(4) anterior, 2–4+2–4 middle (behind transverse sulcus) and 5(4)+5 posterior setigerous spines, in posterior row lateral one or two spines being much larger than others; metatergum 19 with the same spination pattern, but setigerous tubercles smaller and similar in size. Paraterga (Figs 10A, 11A) very strongly developed, antler-shaped, usually three-branched, paraterga on collum with two branches; paraterga 2–8 directed more dorsad than laterad; paraterga 9–18 directed laterad, but clearly ending up above dorsum, each with an additional small denticle at last incision; paraterga 19 directed caudad. Ozopores normal, lying at base of last incision of paraterga (Fig. 11A). Transverse sulcus present on segments 3–18, incomplete (Figs 10A, 11A).

Figure 11.

Desmoxytes spiniterga sp. n., ♂ paratype from near Cave Gui Dong II. A segments 9–10, dorsal view B sternal processes between coxae 4, ventral view C–D entire left gonopod and its distal half, mesal and lateral views, respectively.

Sterna moderately setose, cross-impressions shallow (Fig. 10B). A pair of paramedian processes between ♂ coxae 4 (Figs 10B, 11B). Legs without modifications, midbody legs ca 2.8 times (♂) as long as body height.

Gonopods (Figs 10B, 11C–D) with coxite about 1/3 as long as telopodite. Prefemur almost half as long as acropodite. Femorite short and slender, slightly enlarged distad. Solenophore clearly coiled and divided into a large spiniform lamella lateralis and a very distinct and coiled lamella medialis. Solenomere relatively long.

Remark

Compared to cave-dwelling congeners, this species is much smaller and darker.

Desmoxytes variabilis sp. n.

Figs 1H, 12, 13, 14

Holotype

♂ (SCAU), China, Guangxi, Hechi, Fengshan Xian, Fengcheng Zhen, Cave Huoji Dong, 24°28'32"N, 107°03'28"E, ca 500 m a.s.l., 2015-VIII-3, leg. Jujian Chen, Xinhui Wang & Mingruo Tang.

Paratypes

2 ♂, 3 ♀ (SCAU), same locality and collecting data as the holotype. 2 ♂, 1 ♀ (SCAU), 1 ♂, 1 ♀ (ZFMK), same County, Zhaiya Xiang, Laying Cun, Cave II Dong, 2015-VIII-4, leg. Jujian Chen, Xinhui Wang & Mingruo Tang. 3 ♂, 2 ♀ (SCAU), same County, Jinya Xiang, Hangdong Cun, Cave I Dong, 2014-VI-14, leg. Mingyi Tian, Weixin Liu, Haomin Yin & Xiaozhu Luo. 3 ♂, 2 ♀ (SCAU), Lingyun Xian, Sicheng Zhen, Wuzhishan, Cave Qianlongya, 2015-VI-10, leg. Mingyi Tian, Weixin Liu, Xinhui Wang & Mingruo Tang. 1 ♂, 1 ♀ (SCAU), Bama Xian, Yandong Xiang, Namen Cun, Cave Baiyan Dong, 2015-VIII-3; 3 ♂, 2 ♀ (SCAU), Tian’e Xian, Bala Xiang, Gandong Cun, Cave number VIII Dong, 2015-VIII-8. leg. Jujian Chen, Xinhui Wang & Mingruo Tang. 3 ♂, 3 ♀ (SCAU), China, Guangxi, Hechi, Huanjiang Xian, Mulun, way to Mashan Dong, 2007-V-21, leg. Louis Deharveng & Anne Bedos (CHIgx07-21-02). 2 ♂, 1 ♀ (SCAU), China, Guangxi, Hechi, Huanjiang Xian, near Midong Cun, 2007-V-23, leg. Louis Deharveng & Anne Bedos (CHIgx07-23-05).

Name

To emphasize the metaterga showing a variable pattern of setigerous spines; adjective.

Diagnosis

This species seems to be especially similar to D. nodulosa Liu, Golovatch & Tian, 2014, from Cave II, Xiao’ao Xiang, Du’an Xian, Hechi, Guangxi, because both share very close patterns of metatergal ornamentation and particularly stout gonopods, but differs by the metaterga showing a variable pattern of setigerous spines, and the particularly complex gonopod solenophore.

Description

All characters as in D. laticollis sp. n., except as follows.

Length ca 17–21 (♂) or 20–24 mm (♀), width of midbody pro- and metazonae 1.0–1.2 and 2.8–3.8 (♂) or 1.5–1.8 and 3.0–4.0 mm (♀), respectively. Holotype 19 mm long, 1.0 and 2.8 mm wide on midbody pro- and metazonae, respectively. In width, head < collum < segment 2–4 < segment 5–16. Coloration (Figs 1H, 12, 14–15) varying from dark to light brownish; paraterga and posterior parts of metaterga finely yellow-brownish. Antennae long and slender, reaching back until posterior margin of segment 5 (♂) or segment 4 (♀) when stretched dorsally (Fig. 12A–B).

Figure 12.

Desmoxytes variabilis sp. n., ♂ holotype from Cave Huoji Dong. A–B anterior part of body, lateral and ventral views, respectively C legs 5–7, ventral view D–F midbody segments, lateral, ventral and dorsal views, respectively G–I posterior part of body, lateral, ventral and dorsal views, respectively.

Prozonae faintly microalveolate; metazonae rather microgranulate and shagreened. Collum (Figs 12B, 13B) with 4+4 (or 5+5) anterior and 2+2 (or 3+3) posterior setigerous spines. Metaterga 2–18 (Figs 1213) each with 2+2 (or 3+3) anterior and 2+2 (or 3+3) posterior setigerous spines, lateral spine of posterior row being much larger than others; metatergum 19 with 3+3 anterior and 2+2 posterior, similar, small, setigerous tubercles. Paraterga very strongly developed, antler-shaped, usually three-branched, each tip with an evident lateral seta (Figs 1213). Paraterga of collum stout, two-branched; paraterga 2–5 directed more dorsad than laterad; paraterga 19 directed caudad, horizontal, lying level to dorsum; paraterga 6–18 directed obliquely upwards at ca 45°, in ♂ ending up clearly above dorsum (Figs 1213), but paraterga slightly lower, shorter, subhorizontal and lying level to dorsum in ♀. Ozopores conspicuous, located at last incision of poriferous paraterga (Fig. 14A). Transverse sulcus obscure on collum and metaterga 2–4; more evident, but incomplete on metaterga 5–17 (Figs 1213).

Figure 13.

Desmoxytes variabilis sp. n., ♂ paratype from near Midong Cun. A–B anterior part of body, dorsal and ventral views, respectively C–D midbody segments, dorsal and ventral views, respectively E–F posterior part of body, dorsal and ventral views, respectively.

Sterna sparsely setose, cross-impressions very shallow (Figs 1213). A paramedian pair of separated, short, rounded, poorly setose processes between ♂ coxae 4 (Fig. 14B). Legs long and slender, ca 2.5–2.8 (♂) or 2.0–2.2 (♀) times as long as body height; ♂ femora 5–7 each with a conspicuously densely pilose apophysis ventrally at about midlength (Figs 12C, 13A–B, 14C–E).

Figure 14.

Desmoxytes variabilis sp. n., ♂ paratype from Cave Huoji Dong. A segment 10, dorsal view B sternal processes between coxae 4, ventral view C–E femora 5–7, front view F–G entire right gonopod and its distal half, mesal and lateral views, respectively.

Gonopods (Fig. 14F–G) very short. Coxite less than 1/3 as long as telopodite. Prefemur less than half the length of acropodite. Femorite stout, apically with a distinct sulcus. Solenophore quite complex and compact, divided into two well differentiated lobes, a higher, bipartite and apically acuminate lamina medialis, plus a lower and curved lamina lateralis; solenomere short and flagelliform.

Remark

This obviously troglophilic species is rather eurytopic, occurring both outside and inside caves. It shows a remarkably variable pattern of spination on collum and metaterga (Figs 1213), but the gonopod structure remains stable.

A key to Desmoxytes species currently known to occur in China

(modified after Golovatch et al. 2012; Liu et al. 2014)

1 Paraterga spiniform (Figs 4, 6, 8) 2
Paraterga wing- (Fig. 2) or antler-shaped (Figs 10, 1213) 11
2 ♂ femora unmodified. Gonopod lamella medialis terminally evidently bifid 3
At least a pair of ♂ femora (6–7) humped ventrally 4
3 Lamella medialis devoid of a small midway lobe (Fig. 5B–C) D. simplipoda sp. n.
Lamella medialis supplied with a small lobule at midlength (Fig. 7B–C) D. similis sp. n.
4 At least ♂ femora 7 humped ventrally 5
Only ♂ femora 6 humped ventrally 6
5 Only ♂ femora 7 very evidently humped D. longispina
Both ♂ femora 6 and 7 evidently humped D. spinissima
6 Paraterga spiniform until segment 5, following paraterga very short, coni- to dentiform D. lui
Paraterga spiniform, very long, about as long as body height in ♂ 7
7 Adult body relatively small, length < 20 mm, epigean D. parvula
Adult body much larger, length > 20 mm, mostly troglobites 8
8 Metaterga 2–19 not only with normally arranged setigerous tubercles, but also with a row of similar tubercles along posterior margin 9
Only metaterga 2–4 with several transverse rows of setigerous spines, following metaterga generally smooth, without tubercles along posterior margin 10
9 A pair of rounded setose processes between ♂ coxae 4 (Fig. 9A); gonopod lamella medialis with a distinct spine (Fig. 9D–E) D. phasmoides sp. n.
A pair of square setose processes between ♂ coxae 4 D. minutubercula
10 Gonopod postfemoral part sulcus evident, lamina lateralis with several small lobes; Guangxi D. scutigeroides
Gonopod postfemoral part without sulcus, lamina lateralis simple; Guizhou D. getuhensis
11 Paraterga wing-shaped 12
Paraterga antler-shaped 15
12 Collum the broadest segment (Figs 2A, 3A) D. laticollis sp. n.
Collum narrower than midbody segments 13
13 ♂ femora unmodified. Paraterga long and mostly subfalcate D. eupterygota
♂ femora 5–6 or 6–7 humped. Paraterga stout and suberect 14
14 Metaterga 2–19 with two transverse rows of setigerous spines. Gonopod telopodite suberect D. planata
Metaterga 9–19 with four transverse rows of setigerous spines. Gonopod telopodite subfalcate D. scolopendroides
15 ♂ femora unmodified D. spiniterga sp. n.
At least ♂ femora 6 humped 16
16 Only ♂ femora 6 humped 17
♂ femora 5–7 or 5–6 humped 18
17 A pair of tongue-shaped sternal processes between ♂ coxae 5. Gonopod femorite stout and curved D. lingulata
A pair of divergent sternal processes between ♂ coxae 5. Gonopod femorite elongated and suberect D. cornutus
18 Paraterga strongly and long branched, collum with 4+4 anterior and 1+1 posterior spines; Jiangxi D. draco
Paraterga usually three-branched, collum with at least 4+4 anterior and 2+2 posterior spines, sometimes even more numerous; Guangxi 19
19 Gonopod solenophore simple, solenomere separated at base from solenophore D. nodulosa
Gonopod solenophore complex (Fig. 14F–G), with several lobes, solenomere sheathed by solenophore D. variabilis sp. n.

Conclusion

The family Paradoxosomatidae (Polydesmida) is among the largest in the entire class Diplopoda (nearly 200 genera and >950 species, amounting to about 60% of the total species diversity in the Oriental fauna), but it is highly uncharacteristic of caves. Remarkably, Desmoxytes is the sole genus of Oriental paradoxosomatids that comprises numerous true cavernicoles (Golovatch 2015).

Now that Desmoxytes encompasses 41 described species, of which half derive from mainland China, a few observations seem to be noteworthy. Species group delimitation lies beyond the scope of the present paper, as it focuses only on the Chinese fauna. It also seems somewhat premature given the rapidly growing number of species described lately and certainly many more still to be found across China and Southeast Asia. However, superficially all Desmoxytes spp. that are presumed troglobionts are highly troglomorphic and have only been encountered in the karsts of southern China. Only among such congeners there are several that show remarkably long and spiniform paraterga, obviously an apomorphic troglomorphism.

The diversity of Desmoxytes as currently known may seem biased to cave-dwellers, in part because much of the collecting and taxonomic exploration efforts still focus on cavernicoles alone. Interestingly, however, in contrast to China, not a single troglomorphic species of Desmoxytes has been encountered in the numerous well-explored karsts of Thailand, Laos or Vietnam, even though epigean Desmoxytes are likewise very common and diverse in Indochina.

Acknowledgements

We are very grateful to Thomas Wesener, Zoological Research Museum Alexander Koenig, Bonn, Germany, for his suggestions and help. We also thank Louis Deharveng and Anne Bedos, both Muséum National d’Histoire Naturelle, Paris, France, and members of our team in SCAU for their assistance. This study was sponsored by the China Scholarship Council (CSC2015), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant no. 20134404110026).

Special thanks are due to Robert Mesibov and an anonymous referee for their thorough reviews of the paper.

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