Research Article |
Corresponding author: Weixin Liu ( da2000wei@163.com ) Academic editor: Robert Mesibov
© 2018 Weixin Liu, Sergei Golovatch.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Liu W, Golovatch S (2018) 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). ZooKeys 742: 23-34. https://doi.org/10.3897/zookeys.742.23471
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The genus Tonkinosoma Jeekel, 1953 has hitherto been known to contain only two species, both from northern Vietnam. T. flexipes Jeekel, 1953, the type species of the genus, is recorded from Guangxi, southern China, for the first time. T. tiani sp. n., a presumed troglobite, is described from caves in Guizhou, southwestern China. A key is presented to all three species of the genus.
Guangxi, Guizhou, key, new record, new species, Tonkinosoma , troglobite
The millipede genus Tonkinosoma Jeekel, 1953 was originally proposed to encompass only a single species, T. flexipes Jeekel, 1953, from northern Vietnam (
At present, Tonkinosoma can be diagnosed as a genus of the Himalayan and southeast Asian tribe Chamberliniini characterized by the gonopods which show a postfemoral part demarcated basally by an indistinct (T. flexipes) or distinct (T. jeekeli) geniculation cingulum and distally at least by a lateral sulcus. Unlike the other contribal genera, the femorite is long and slender and, like the postfemoral part, it is devoid of outgrowths, the seminal groove runs all along the mesal face of the femorite, the solenomere is long and flagelliform, and the solenophore is a long, hyaline, folded lobe that shows a lamina medialis and a lamina lateralis, both sheathing the solenomere. As in most Chamberliniini, both solenomere and solenophore are usually subcircular (
Prompted by the discovery of both T. flexipes and a third, new species of Tonkinosoma in southern China, the latter species the first to be found in caves, their descriptions are provided below. We also provide a key to all three presently known species of this genus.
All specimens used in this study were collected in southern China and preserved in 95% ethanol. Most of the type and non-type material is deposited in the Zoological Collection of the South China Agricultural University, Guangzhou, China (
Observation and dissections were performed using a Leica S8 APO stereo microscope. The line drawings were prepared with a Leica MZ125 microscope and a camera lucida attached to the microscope.
Photographs were taken with a Keyence VHX-5000 digital microscope, and further edited using Adobe Photoshop CS5.
1 | Body with a distinct colour pattern, yellowish brown to reddish brown (Figs |
2 |
– | Body uniformly yellowish to pallid (Fig. |
T. tiani sp. n. |
2 | A large, median, subquadrate process between ♂ coxae 4 and two small, independent tuberculations between ♂ coxae 5 (Fig. |
T. flexipes |
– | Only two small and independent processes between ♂ coxae 4, without any modifications between ♂ coxae 5 | T. jeekeli |
Tonkinosoma flexipes Jeekel, 1953: 1, figs 1–4.
Tonkinosoma
flexipes
–
9 ♂, 1 ♀ (
This is the type species of Tonkinosoma hitherto known only from a highly detailed original description, based on the male holotype and two paratypes, one male and one female, all from Mt Manson, Langson Province, northern Vietnam (
Tonkinosoma flexipes Jeekel, 1953, ♂. A–C anterior part of body, dorsal, ventral and lateral views, respectively D, E midbody segments; dorsal and subventral views, respectively F sternite V, ventral view G, H posterior part of body, dorsal and ventrolateral views, respectively I legs 3, 9, 16, anterior views. Scale bar: 0.2 mm.
Holotype ♂ (
9 ♂, 20 ♀ (
To honour Prof. Mingyi Tian, one of the collectors from South China Agricultural University.
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.
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.
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.
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.
Integument shining, texture of prozonae finely micro-alveolate. Stricture between pro- and metazonae broad and shallow, clearly ribbed (Figs
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
Transverse sulcus incomplete on metaterga 4–7, more evident, complete and reaching bases of paraterga on metaterga 8–18 (Figs
Epiproct tip truncated, with four spinnerets (Figs
Pleurosternal carinae very strongly developed, present on segments 2–17 both in ♂ and ♀ (Figs
Sterna modestly setose, cross-impressions shallow (Fig.
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.
Gonopods (Figs
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.
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.
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.
The above record of T. tiani sp. n. in caves in southern China is remarkable at least in two ways. Firstly, the huge family Paradoxosomatidae only rarely occurs in caves, with only few presumably troglobitic species. The only exceptions are in the large genus Desmoxytes Chamberlin, 1923, which is very common both in epigean and subterranean environments across southeast Asia and China, and in the small genus Piccola Attems, 1953, with a few epigean species in Vietnam and Laos, and a single troglobitic one from Guangxi, China (
Further research on cave millipedes of China will definitely reveal not only new interesting taxa, but more cases of remarkable distribution patterns.
We are particularly grateful Prof. Yuanhai Zhang (Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin) for his invitation and arrangements. We would like to thank “Xiongda” (Dr. Philip John Rowsell, Hongmeigui Cave Exploration Society), “Dudou”, “Jiuyao” and “Laocai” (Jinzhou Cave Exploration Club, Xingyi, Guizhou) for their invaluable assistance during our survey in the Qianxinan Autonomous Prefecture. Thanks also go to the caving team of the South China Agricultural University, Guangzhou, China, for their assistance in the field. We heartily thank three reviewers, R. Mesibov, D. VandenSpiegel, and P. Decker, for their help in critically reading and improving the paper.