Two new species of the millipede family Cambalopsidae from Myanmar (Diplopoda, Spirostreptida)

Abstract Two new species of cave-dwelling millipedes are described from Myanmar, one each in the genera Plusioglyphiulus Silvestri, 1923 and Trachyjulus Peters, 1864. Plusioglyphiulus digitiformis sp. n. joins the small peculiar group of congeners from Thailand which is characterized by such plesiomorphies as the tergal crests on the collum and following metaterga being transversely divided into two, not three parts, as in species of the genus Glyphiulus Gervais, 1847. However, this new species differs by the 3-segmented telopodites of ♂ legs 1, the anterior gonopodal coxosternum showing higher and nearly straight apicomesal processes and very evident apicolateral teeth, as well as the higher and acuminate paramedian coxal processes of the posterior gonopods, the latter’s telopodites demonstrating an apical fovea bearing a group of microsetae at the bottom. Trachyjulus bifidus sp. n. is primarily distinguished by the telopodites of their anterior gonopods being strikingly and deeply bifid. A key to the five species of Cambalopsidae currently known to occur in Myanmar is presented, and a map showing their distributions given.


Introduction
Myanmar is globally recognized as a highly important hotspot of biodiversity, supporting a great number of species and abundant forest resources (Myers et al. 2000). Unfortunately, by 2010 the deforested areas in Myanmar totalled 21,178.8 km 2 , with an annual deforestation rate of 0.81% between 1990 and 2010 (Wang and Myint 2016). Yet some regions, especially montane ones, remain rich in woodlands, including primary tropical forest.
Cambalopsidae is the largest family in the suborder Cambalidea, order Spirostreptida, and it currently contains > 100 species in 7-8 genera, all in Southeast Asia and Indo-Australia, up to central China in the north and Borneo in the east (Hoffman 1980, Mauriès 1983. Only a couple of anthropochore species have attained particularly vast pantropical distributions. Pocock (1893) was the first to describe cambalopsids from Myanmar, three new species currently referred to as Trachyjulus calvus (Pocock, 1893), Podoglyphiulus doriae (Pocock, 1893) and P. feae (Pocock, 1893). According to the latest catalogue of the Diplopoda of Myanmar (Likhitrakarn et al. 2017), the fauna of that country currently amounts to 92 species, including those first three cambalopsids of Pocock.
After more than 120 years of complete inactivity in this respect, the present paper puts on record another two new species of Cambalopsidae from Myanmar. It also provides a key to all five species of this family in that country, as well as a map showing their distributions. The two new species described below are also the first to come from caves in Myanmar.

Material and methods
The material was collected in Myanmar in 2015-2016 by Somsak Panha and members of the Animal Systematics Research Unit, Chulalongkorn University, as well as by a French collecting team headed by Louis Deharveng, of the Muséum National d'Histoire Naturelle, Paris, France. Photographs of live animals were taken in the laboratory using a Nikon 700D digital camera with a Nikon AF-S VR 105 mm macro lens. Specimens were preserved in 75% ethanol, and morphological observations made under an Olympus SZX7 stereo microscope.
Scanning electron micrographs (SEM) were taken applying a JEOL, JSM-5410 LV microscope, and the material returned to alcohol upon examination. Pictures of the gonopods of the holotypes were taken in the laboratory and assembled using "Cell D " automontage software of the Olympus Soft Imaging Solution package. The key below is primarily based on the descriptions by Golovatch et al. (2007aGolovatch et al. ( , 2007bGolovatch et al. ( , 2009Golovatch et al. ( , 2011. One of the holotypes, as well as most of the paratypes are housed in the Museum of Zoology, Chulalongkorn University (CUMZ), Bangkok, Thailand. The other holotype and several paratypes are stored in the Muséum national d'Histoire naturelle (MNHN), Paris, France, while a few paratypes are deposited in the collection of the Zoological Museum, State University of Moscow (ZMUM), Russia, as indicated in the text.
Diagnosis. This new species is apparently most similar to P. antiquior Golovatch, Geoffroy, Mauriès & VandenSpiegel, 2011, from a cave in Kanchanaburi Province, Thailand (Golovatch et al. 2011), in sharing the special the carinotaxic formulae of the collum and postcollum rings ( Fig  3K, L, 4H, I). However, the new species differs from P. antiquior in the more clearly divided crests on metaterga, the lateral ones being somewhat higher, coupled with the 3-segmented telopodites of ♂ legs 1, the anterior gonopodal coxosternum showing higher and nearly straight apicomesal coxoternal processes (acp) and very evident basolateral coxosternal processes (bcp), as well as the higher and acuminate anterior coxal processes (ap) of the posterior gonopods, the latter's telopodite (te) demonstrating an apical fovea that bears a group of microsetae at the bottom (Figs 3K, L, 4H, I).
Colouration of live animals light red-brown ( Fig. 1) with lighter anterior and posterior parts of body; antennae, venter and legs light yellowish; coloration in alcohol, after two years of preservation, uniformly light red brownish to dark castaneous brown,   dorsal crests and porosteles usually dark brownish. Antennae and venter yellow brownish to brownish. Ommatidia brown to blackish.
Legs nearly as long as body diameter (Fig. 2K), claw at base with a strong accessory claw almost half as long as claw itself (Fig. 4F).
Anterior gonopods (Figs 3G-I, 4G) with a typical shield-like coxosternum, the latter modestly setose on caudal face and provided with a concave notch separating a pair of high, nearly straight, terminally rounded, apicomesal, coxosternal processes (acp) and a much lower basolateral coxosternal processes (bcp), these being rounded at tip; telopodite (te) typical, rather stout, movable, 1-segmented, lateral in position, with several strong apical setae and a field of small microsetae at base, slightly longer than adjacent bcp.
Remarks. The genus Plusioglyphiulus Silvestri, 1923 has recently been reviewed (Golovatch et al. 2009(Golovatch et al. , 2011 and shown to comprise 27 species ranging from northern Thailand and Laos in the west to Borneo in the east and southeast. This new species is the first Plusioglyphiulus to be recorded from Myanmar. Based on the pigmented body and eye patches, and like most if not all other cave-dwelling congeners known to date, P. digitiformis sp. n. seems to be hardly more than a troglophile. Most species of this genus show particularly enlarged colla with the tergal crests both on the collum and following segments being clearly divided transversely into three parts. Only two species, P. antiquior and P. panhai Golovatch, Geoffroy, Mauriès & VandenSpiegel, 2011, both from caves in Thailand and both found quite close to the frontier to Myanmar, are remarkable in still showing the pattern of carinotaxy observed in the genus Glyphiulus Gervais, 1847 (Golovatch et al. 2011).
In particular, while their gonopods are relatively complex and unequivocally the same as in typical Plusioglyphiulus, the carinotaxic pattern is simple and typical of Glyphiulus, i.e., the crests on their colla and following metaterga are divided transversely into two, not three, parts. In this respect, P. digitiformis sp. n. clearly joins the above duet, showing the closest similarities, both morphologically and geographically, to P. antiquior.
Non-type material shows all characters of the type series, but their localities lie very far from the others (ca. 470 km) (Fig. 8). We hope that future molecular studies will answer the question of the conspecificity (or not) of all above populations.
Interestingly, the famous Burmese amber, 99-100 Mya, appears to contain a typical Plusioglyphiulus yet to be described (Wesener in litt.). This is evidence both of the very old age of this genus and its long presence in situ. Etymology. To emphasize the strongly bifid telopodites of the anterior gonopods; adjective.

Genus
Diagnosis. Differs from other Trachyjulus species based primarily on the following combination characters: the strongly elongated and bifid telopodites (te) of the anterior gonopods, coupled with the absence of flagella and the presence of deeply bipartite posterior gonopods, in which the telopodites (te) are much shorter than the massive, paramedian, coxal processes (cp).
Coloration of adults in alcohol light grey-brown to dark castaneous brown, without a clear-cut pattern. Head, antennae and venter light yellowish to brownish. Ommatidia brown to blackish.
Ventral flaps behind gonopod aperture on ♂ segment 7 evident swellings, forming a marked transverse ridge.
Legs nearly as long as body diameter (Fig. 5N), claw with an evident and long accessory claw near base (Fig. 5P), the latter up to ca. 2/3 rd s the length of claw itself (Fig. 5P).
♂ legs 1 highly characteristic (Figs 6A, B, 7C) in being very strongly reduced, with large 1-segmented telopodites and a pair of large, hook-shaped, medially contiguous, sternal processes with groups of long and strong setae at base on caudal face.
Remarks. The genus Trachyjulus Peters, 1864 is currently known to comprise 31 species ranging from Nepal, India, and Sri Lanka in the west, through Bangladesh and Myanmar to Vietnam, Thailand, Malay Peninsula, Singapore, and Indonesia (Sumatra and Java) in the east (Golovatch et al. 2012). Only one species, the pantropical anthropochore T. calvus, has hitherto been documented from Myanmar (Likhitrakarn et al. 2017). This species (cf. Golovatch et al. 2012) is similar to T. bifidus sp. n., but the latter is clearly distinguished by the bifid telopodites of the anterior and posterior gonopods.
Based on the pigmented body and eye patches, and like most if not all other cavedwelling congeners known to date, T. bifidus sp. n. seems to be hardly more than a troglophile.
No special key to relevant genera involved seems to be needed, as the one given below to Myanmar species contains the necessary information.

Key to Cambalopsidae species currently known to occur in Myanmar, chiefly based on male characters:
1 Collum smooth, without strong longitudinal crests ( Fig. 5A-C)

Conclusions
There are 94 millipede species currently known to occur in Myanmar, including both new ones described above. The new material comes from some of the 27 caves located within a radius of ca. 70 km around the town of Kalaw, Shan State, northeastern Myanmar (Piccini et al. 2009). Studies on the cave fauna of that country have just begun and there can hardly be any doubt that many more interesting discoveries are ahead. These will certainly concern Diplopoda as well. Because Cambalopsidae are especially diverse and common in karsts of the adjacent parts of China, Laos, Thailand and Malaysia, where they are usually associated with bat guano in caves (Golovatch 2015), the same presumption can easily be extended to the karsts of Myanmar, too.