Study on the Pauropoda from Tibet, China. Part I. The genera Decapauropus and Hemipauropus (Myriapoda)

Abstract Three new species of family Pauropodidae: Decapauropus biconjugarus Qian & Bu, sp. n., D. tibeticus Qian & Bu, sp. n. and Hemipauropus quadrangulus Qian & Bu, sp. n. are described and illustrated from southeastern Tibet, China. The genus Hemipauropus is recorded for the first time from China. This is the second report of pauropods from Tibet.


Introduction
To date, there is only one species of Pauropoda reported in Tibet (Zhang and Chen 1988). Since only a single specimen was obtained and was tentatively identified as Sphaeropauropus sp. of the family Sphaeropauropodidae, Silvestri, 1930. For the last thirty years, this remained the only record of Pauropoda from Tibet. In November 2015, a short expedition to Motuo and Bomi counties, southeastern Tibet of China was carried out. In total, 50 specimens of Pauropoda were obtained during the expedition. In the present study, we describe and illustrate three new species of the family Pauropodidae Lubbock, 1867, including one species belonging to the genus Hemipauropus, which is recorded for the first time from China. The other two species belong to the genus Decapauropus. This is the second report of pauropods from the territory of Tibet.

Materials and methods
Sampling was made in three areas of southeastern Tibet in 2015: Dexing town, Motuo County; Beibeng town, Motuo County, and Songzong town, Bomi County. Pauropods were collected by means of Tullgren's funnel. Specimens were sorted under a stereo dissection microscope and preserved in 80% alcohol. Each specimen was mounted with Hoyer's solution and identified under a phase contrast microscope (Nikon ECLIPSE Ni, objective lens 100X / 1.30 Oil, ∞/ 0.17 WD 0.20 (0.16)). All specimens were deposited in the collection maintained by the Shanghai Natural History Museum (SNHM) and the Shanghai Entomological Museum (SEM).
Abbreviations used in the descriptions: Head. a 1 -a submedian pair of setae on tergal side of head, a 2 -an intermediate pair of setae on tergal side of head, a 3 -a sublateral pair of setae on tergal side of head, a 4 -a posterolateral pair of setae on head.
Antenna. bs -base segment of antennal flagellum, F 1 -flagellum of tergal antennal branch; F 2 -anterior flagellum of sternal antennal branch, F 3 -posterior flagellum of sternal antennal branch, g -globulus of sternal antennal branch, p -a tergal seta on fourth antennal segment, p' -an anterior seta on fourth antennal segment, p" -a sternal seta on fourth antennal segment, q -a seta on sternal side of sternal antennal branch, r -a posterior seta on fourth antennal segment, s -sternal antennal branch, t -tergal antennal branch.
Measurements are provided as length of body in mm; the range of variation in adult paratypes is given in brackets. Absolute lengths of all other body parts are given in μm. Otherwise, the text refers relative lengths. XZ-PA2015019 (SNHM), XZ-PA2015026 (SEM)), 2 subadults, with 8 pairs of legs (slides no. XZ-PA2015027 (SNHM), XZ-PA2015031 (SEM)), same data as holotype.

Taxonomy
Etymology. From the Latin biconjugarus referring to the anal plate with two pairs of clavate appendages.
Diagnosis. Decapauropus biconjugarus sp. n. is distinguished from the other species in the genus by the shape of the anal plate: subquadrate, with obvious U-shape and concave lateral margins; distal part with 4 posteriorly directed clavate appendages, dorsal ones thickest, straight, annulate, those protruding from sternal side shorter and thinner, straight, glabrous. Posterior part of the pygidial sternum evenly rounded.
Pygidum. Tergum (Figs 1G, 2H). Posterior margin evenly rounded but with small median triangular lobe between a 1 and st, the lobe granulated distally. Relative lengths of setae: a 1 = 100, a 2 = 82.4, a 3 = 117.6, st = 58.8. All setae subcylindrical, blunt, striate; st convergent; Distance a 1 -a 1 0.64 of length of a 1 ; distance a 1 -a 2 3.3 times as long as a 2 -a 3 ; distance st-st 1.5 times as long as st and 1.4 times as long as distance a 1 -a 1 . Sternum (Figs 1H, 2I). Posterior margin evenly rounded and smooth between b 1 . Relative lengths of setae (a 1 =100) Anal plate subquadrate, with obvious U shape concave lateral margins; distal part with four posteriorly directed clavate appendages, tergal ones thickest, straight, annulate, those protruding from sternal side shorter and thinner, straight, glabrous. Tergal and sternal appendages 0.9 and 0.5 times as long as plate respectively. Plate and sternum glabrous.
Remarks. This new species seems to be a very close relative of D. bedosae Scheller from north-western Thailand (Scheller 1995) and D. cibodasensis Scheller from Singapore (Scheller 2007). They can be distinguished by the shape of the posterior part of the pygidial sternum (margin evenly rounded in the new species vs. straight in D. cibodasensis; with broad indentation in D. bedosae) and by the shape of the anal plate (plate short with medium appendages in D. biconjugarus; plate short with long appendages in D. cibodasensis; plate longer with sort appendages, especially the sternal ones in D. bedosae).  Etymology. The species is named after Tibet. Diagnosis. Decapauropus tibeticus sp. n. is distinguished from the other species in the genus by the shape of the anal plate bearing comma shaped appendages with pubescence. This in combination with st expanded and annulate distally is a very peculiar character for members of this genus.
Remarks. The species differs significantly from the other congeners. The comma shaped appendages of the anal plate with a pair of little stubs are characters unknown in other members of the genus.

Genus Hemipauropus Silvestri, 1902, new record to China
Type species. Hemipauropus leptoproctus Silvestri, 1902 Diagnosis. Preanal segment much narrower than other body segments, cuticles of tergites with reticulations, particularly on most anterior and posterior parts; pygidial sternum with one pair of seta, b 1 . Distribution. Palaearctic region; Neotropical region; Ethiopian region; Oriental region; Australian region. Etymology. From Latin quadrangulus meaning four angles and referring to the shape of the base of the anal plate.

Hemipauropus quadrangulus
Diagnosis. Hemipauropus quadrangulus sp. n. is distinguished from the other species in the genus by the shape of the anal plate, which has a peculiar small Shuriken base and 6+6 setae on tergite IV.
Antennae (Figs 5A, 6H). Setae on segments 1-3 folioform. Segment 4 with four setae, p and p' subcylidrical, p" leaf-shaped, r very thin, p' and p" striate; relative lengths of setae: p = 10, p' = 9.3, p" = 3.3, r = 4. Tergal branch t somewhat fusiform, 3.8 times as long as greatest diameter and 0.95 of the length of sternal branch s; that branch 2.9 times as long as greatest diameter; anterodistal corner truncated. Seta q 1.3 times as long as seta p' of segment 4, 0.95 of the length of s. Relative lengths of flagella (base segments included) and base segments: F 1 = 100, bs 1 = 17.3; F 2 = 46.7, bs 2 = 14.7; F 3 = 101.3, bs 3 = 14.7. F 1 3.3 times as long as t, F 2 and F 3 1.2 and 2.5 times as long as s respectively. Distal organ of F 1 and F 2 consisting of densely arranged pubescent bracts around sessile capsule, F 3 with flat calyx; flagella axes below distal organs not widened in F 1 and F 2 , slightly in F 3 . Globulus g pyriform, 0.2 of the length of s, diameter 0.8 of greatest diameter of t; 8-10 bracts; capsule subspherical. Antennae almost glabrous.
Genital papillae (Figs 5F, 6I). Longish, conical with narrowing and extended distal half, 1.6 times as long as wide, seta short, 0.3 of the length of papilla. Coxal seta of leg II as on leg I, length 10 μm (Fig. 6I).
Anal plate simple and glabrous, with a little base, the base like a Shuriken; posterior median forked part 5.8 times as long as broadest basal part.

Discussion
Pauropoda is a group of tiny soil myriapods, usually less than 2 mm, with unique branched antennae, having 11 (or 12) body segments and 9 (or 10 or 11) pairs of legs (Scheller 2011b). All species lack eyes and most of them also lack a tracheal system. More than 900 species grouped in 12 families have been found in the world (Qian et al. 2015). However, pauropods are still poorly known in China. Up to now, only 42 species belonging to 12 genera and 4 families have been recorded in China, as most of them were found in southeast and east China (Qian et al. 2015). This study increased our knowledge of pauropod diversity in Tibet.
As one of the most ecologically diverse landscapes on earth, the Tibetan Plateau is home to numerous rare and endangered species, and has attracted so many taxonomists to explore the biodiversity, although it is a remote area at a high altitude. However, there is only one report on the pauropods in Tibet (Zhang and Chen 1988) before our study, probably due to their small size, cryptic behavior, and the difficulties in identification.
Two of three new species reported in this study were collected from Motuo County (northern latitude 27°33' to 29°55', east longitude 93°45' to 96°05'), in the Linzhi area of southeastern Tibet. Standing 1,000 meters above the sea level on average, Motuo is surrounded by snow-capped mountains. Meanwhile, located in the lower reaches of the Yarlung Zangbo River, Motuo has a typical sub-tropical climate, warm and rainy all year round. The diversity of plants and animals in Motuo is rich in tropical species, with many endemic species (Wu et al. 2005, Zhang 2011). In this study, a similar situation in soil-dwelling pauropods was found, especially for the genus Hemipauropus, which is recorded for the first time in China. This genus has been found in all main zoogeographical regions, but rarely in temperate areas (Scheller 2011b). The morphology of the Hemipauropus species are very close to some genera of the Pauropoda distributed in the tropics.
Since our collecting sites in Tibet are still very sparse, we have not found the species of Sphaeropauropus sp. reported by Zhang and Chen (1988) and further investigations should be made in the future so as to reveal the diversity of Pauropoda in this area.