Three new cavernicolous species of the millipede genus Trichopeltis Pocock, 1894 from southern China (Diplopoda, Polydesmida, Cryptodesmidae)

Abstract Three new species of Trichopeltis are described from caves in southern China: T. bellus sp. n., T. intricatus sp. n., and T. reflexus sp. n., all presumed troglobites. The former two come from Yunnan Province, the latter one from Hunan Province. An updated key to all eleven currently known species of Trichopeltis is provided.


Introduction
The Cryptodesmidae is a relatively small millipede family that globally encompasses approximately 40 genera and 130 species. It is distributed from Mexico to Argentina in the Americas, occurring also in tropical Africa and tropical to subtropical Asia to Papua New Guinea and Japan in the East (Enghoff et al. 2015). In tropical or subtropical Asia and Australasia, Cryptodesmidae currently comprise only 12 genera (including two that remain dubious) and 36 species.
Rather recently, Trichopeltis has been reviewed and a key provided to five of its species (Golovatch et al. 2010, Golovatch andAkkari 2016, and the references therein). The present paper records an additional three new species of Trichopeltis, all three of which are presumed to be troglobites from southern China.

Materials and methods
All specimens used in this study were collected by hand from caves in southern China and are preserved in 95% ethanol. The type material is deposited in the zoological collection of the South China Agricultural University, Guangzhou, China (SCAU).
Observations and dissections were performed using a Leica S8 APO stereo microscope. The line drawings were prepared with a Zeiss Imager Axioskop40 microscope and a camera lucida attached for the scope. Photographs were taken with a Canon EOS 40D camera, then focus-stacked with Z-stack software, or Keyence VHX-5000 digital microscope, and further edited using Adobe Photoshop CS5 and Illustrator CC software.
Remark. Based on the unpigmented body and long legs, this species is probably a troglobite. Etymology. To emphasize the complex gonopods; adjective. Diagnosis. Differs from all congeners except T. bellus sp. n. by the unusually densely setose gonopodal coxa, and from all species by the particularly complex gonopod which shows a number of peculiar processes and lobules (Fig. 4). See also the Key below. Description. Length of holotype ca. 10 mm, width of midbody pro-and metazonae 1.5 and 2.5 mm, respectively. Coloration in alcohol nearly pallid. Body with 20 segments (Fig. 4). All characters as in the previous species (Figs 1-3), except as follows. In width, head < collum < segment 2 < 3-4 < 5 < 6 < 7; thereafter body increasingly tapered towards telson (Fig. 4).
Remark. Based on the pallid body, this species may be a troglobite.  (Golovatch et al. 2010) strongly resembles T. reflexus sp. n. in showing a similarly condensed apical third of the gonopodal telopodite, but that in the latter species is less strongly curved, untwisted and more elaborate. See also Key below.
Remark. Based on the pallid body and slender legs, this seems to be a troglobite.

Conclusions and discussion
The family Cryptodesmidae was hitherto known to encompass three presumed troglobiont species: Peridontodesmella alba Schubart, 1957, from Brazil (Trajano et al. 2000); Trichopeltis latellai, from two caves in Guizhou, China (Golovatch et al. 2010); and T. cavernicola, from two caves in Laos (Golovatch 2016, Golovatch andVandenSpiegel 2017). The three new species described above show clear traits of troglomorphism, thereby considerably increasing the number of presumably troglobiont cryptodesmids known globally. Almost all of southern China is blanketed by Earth's most extensive karsts (Deharveng and Bedos 2012). Some of them are known to be especially rich in biodiversity, while the Mulun and surrounding karsts in Guangxi Province host some of the richest cave fauna of China (Deharveng et al. 2008). This fauna encompasses millipedes as well (Golovatch 2015).
At present, most of the species of Trichopeltis, including both epigean and cavernicolous taxa, occur in Indo-Burma and Indochina. With the description of the above three new taxa, and with further explorations of southern China karst region, the southern part of the country will certainly become an important hotspot of Trichopeltis diversity. Due to a rapid discovery of new species, the previous key (Golovatch et al. 2010), which is only a few years old, is already out of date. The same is likely to occur with the new key provided above, as there is little doubt that new taxa will be found in the near future at least in southern China.