Occurrence of the millipede genus Tonkinosoma Jeekel, 1953 in China, with the description of the first presumed troglobitic species of this genus (Diplopoda, Polydesmida, Paradoxosomatidae)
Author
Liu, Weixin
Author
Golovatch, Sergei
text
ZooKeys
2018
742
23
34
http://dx.doi.org/10.3897/zookeys.742.23471
journal article
http://dx.doi.org/10.3897/zookeys.742.23471
1313-2970-742-23
6419AC9558EF4033803DDAC73F347405
6419AC9558EF4033803DDAC73F347405
Tonkinosoma tiani
sp. n.
Figs 4, 5, 6, 7, 8
Type
material.
Holotype ♂ (SCAU), China, Guizhou Province, Qianxinan, Anlong County, Sayu Town, Ganhan Dong Cave,
25°11'25"N
,
105°19'31"E
, 1250 m a.s.l., 12.V.2017, leg. Mingyi Tian, Weixin Liu, Xiaozhu Luo, Pingjing Yang & Yanyi Pu.
Paratypes.
9 ♂, 20 ♀ (SCAU), same data as holotype. 8 ♂ (SCAU), same county, Longguang Town, Fengyan Dong Cave,
25°10'05"N
,
105°13'50"E
, 1400 m a.s.l., 12.V.2017; 13 ♂, 4 ♀ (SCAU), 1 ♂, 1 ♀ (ZMUM), Guizhou, Xingyi City, Wushan Town, Xiaozi Dong Cave, N 25°06'43", E 104°46'32", 1750 m a.s.l., 14.V.2017; all leg. Mingyi Tian, Weixin Liu, Xiaozhu Luo, Pingjing Yang & Yanyi Pu.
Name
.
To honour Prof. Mingyi Tian, one of the collectors from South China Agricultural University.
Diagnosis.
This new species differs from its congeners in showing a largely unpigmented body. It seems to be especially similar to
T. jeekeli
on account of the particularly elongate and subcircular solenophore and solenomere, but differs by the strongly developed pleurosternal
carinae
present until segment 17 in both sexes, by an evident, subtrapeziform process between ♂ coxae 4, and the gonopod with a small and sharp tooth near the base of the solenomere.
Description.
Lengths of both sexes ca 25-27 mm, widths 1.6-1.8 and 2.0-2.2 mm (♂) or 1.8-2.0 and 2.2-2.5 mm (♀) on pro- and metazonae, respectively. Holotype ca 27 mm long, and 1.8 and 2.2 mm wide on midbody pro- and metazonae, respectively.
Live coloration rather uniformly yellowish to pale (Fig. 4).
Body with 20 segments. In width, collum <head = segment 3 <2 = 4 <5-7 <8-16, thereafter body increasingly tapered towards telson.
Head: frons densely pilose, vertex smooth, epicranial suture distinct (Fig. 5
A-B
). Antennae long and slender, reaching behind body segment 4 when extended posteriorly; in length, antennomere 2> 3> 5> 4> 6> 1> 7 (Fig. 5
B-C
).
Collum with 4+4 short setae at anterior margin. Following metaterga with traces of at least 1+1 setae before transverse sulcus, but pattern mostly vague and setae abraded.
Paraterga
of collum small, but evident, rounded. Paraterga 2 well-developed, directed down, with 4-5 clear lateral incisions on each side, frontolateral corner much sharper (Fig. 5A). Paraterga 3-6 each with three small, lateral incisions (Figs 5A), following paratergal incisions indistinct (Figs 5D, G, 6A). Calluses of paraterga 5-18 very thin
in
poreless segments, slightly thicker and sinuate in dorsal view in caudal 1/3 (ozopore position) of pore-bearing ones (Figs 5D, F, 6
A-B
); paraterga 19 nearly suppressed, but its ozopores clear (Fig. 5I).
Integument shining, texture of prozonae finely micro-alveolate. Stricture between pro- and metazonae broad and shallow, clearly ribbed (Figs 5D, 6
A-B
).
Pore formula normal (5, 7, 9, 10, 12, 13, 15-19), ozopores distinct, entirely lateral, lying inside an ovoid groove near caudal paratergal corner (Figs 5F, 6B).
Transverse sulcus incomplete on metaterga 4-7, more evident, complete and reaching bases of paraterga on metaterga 8-18 (Figs 5D, G, 6A). Axial line missing.
Epiproct tip truncated, with four spinnerets (Figs 5
G-I
). Paraproct with two setigerous knobs. Hypoproct roundly subtrapeziform, caudal setae distinctly separated, borne on evident knobs (Fig. 5H).
Pleurosternal carinae very strongly developed, present on segments 2-17 both in ♂ and ♀ (Figs 5C, F, 6B).
Sterna modestly setose, cross-impressions shallow (Fig. 5E). An evident, apically setose, subtrapeziform process between ♂ coxae 4 (Fig. 6C).
Legs long and slender, ca 2.5 (♂) or 2.0 (♀) times as long as midbody height. Tarsal brushes present only on ♂ legs 1-7, following legs normal, unmodified (Fig. 6D).
Gonopods (Figs 6D, 7, 8) simple. Coxite relatively short, about half as long as telopodite, poorly setose both distodorsally and distoventrally. Prefemoral portion densely setose as usual, about as long as coxite. Femorite (fe) long and slender, slightly curved mesally and faintly enlarged distally. An obvious demarcation sulcus (s) both laterally and dorsally between fe and a postfemoral portion (pf). Solenophore (sph) clearly coiled, circular, both lamina medialis (lm) and lamina lateralis (ll) well-developed and nearly entirely sheathing a similarly long and free solenomere (sl). Seminal groove (sg) running entirely on mesal side of femorite before moving onto sl, with a very small, sharp, mesal tooth (t) on pf near sl base.
Remarks.
The karstic Ganhan Dong cave where the holotype was taken is about 300 m long. All material was collected in areas of complete darkness.
Based on the largely unpigmented integument, the long legs (2.5 (♂) or 2.0 (♀) vs. 1.6 (♂) or 1.2 (♀) times as long as midbody height in
T. flexipes
) and the cave habitat, this species seems to be a troglobite.
Figure 4.
Tonkinosoma tiani
sp. n. in nature A, B two different ♂ paratypes.
Figure 5.
Tonkinosoma tiani
sp. n., ♂ paratype from Ganhan Cave.
A-C
anterior part of body, dorsal, ventral and lateral views, respectively
D-F
midbody segments; dorsal, ventral and lateral views, respectively
G-I
posterior part of body, dorsal, ventral and lateral views, respectively. Scale bar: 0.2 mm.
Figure 6.
Tonkinosoma tiani
sp. n., ♂ paratype from Ganhan Cave. A, B segments 6-8, dorsal and lateral views, respectively C sternite V, ventral view D gonopods in situ, ventral view E legs 4 and 9, anterior view. Abbreviations: b = tarsal brush; o = ozopore; pl = pleurosternal carina.
Figure 7.
Tonkinosoma tiani
sp. n., ♂ paratype from Ganhan Cave.
A-C
left gonopod, mesal, anterior and lateral views, respectively. Abbreviations: fe = femorite; ll = lamella lateralis; lm = lamella medialis; pf = postfemur; s = sulcus; sg = seminal groove; sl = solenomere; sph = solenophore; t = tooth.
Figure 8.
Tonkinosoma tiani
sp. n., ♂ paratype from Ganhan Cave. A, B left gonopod, submesal and lateral views, respectively. Abbreviations: s = sulcus; sl = solenomere; sph = solenophore; t = tooth.