Baculentulus xizangensis sp. nov. from Tibet Autonomous Region, China is described. The new species is characterized by the presence of sensillum b' on foretarsus, short sensillum a' , one pair of A-setae (AS) on tergite VII, one pair of P-setae (P1) on sternite I, and comb with few teeth and straight hind margin. It is similar to Baculentulus ogawai (Imadaté, 1965) from Thailand, but differs in the length of sensilla a' and b' shape of maxillary gland and comb, and in the chaetotaxy on sternite I. The key to the group of Baculentulus spp. with foretarsal sensillum b' present is provided.
The genus Baculentulus Tuxen, 1977 including 38 species distributed all over the world (Szeptycki 2007; Wu & Yin 2008; Nakamura & Likhitrakarn 2009; Shrubovych 2010; Rusek et al. 2012). Among them, 9 species have been reported from China (Yin 1999; Wu & Yin 2008). It is characterized by baculiform sensillum t1 on foretarsus, sensillum b' present (in 9 species) or absent (in 29 species), calyx of maxillary gland smooth, heart-shaped, the reduced striate band on abdominal segment VIII, and sternite VIII has 4 setae.
The Protura fauna of Tibet Autonomous Region of China have been studied by Yin (1981, 1982, 1983a, 1983b, 1990). Twelve species belong to the families Protentomidae, Berberentulidae, Eosentomidae and Antelientomidae have been recorded in this region so far (Yin 1999). In 2009, we investigated this region again and many proturan specimens were obtained. Among them, one new species of Baculentulus was found and described in the present paper. The key to the Baculentu- lus species with foretarsal sensillum b' was also provided.
MATERIALS AND METHODS
Specimens were extracted by means of the Tullgren funnels from soil samples. They were mounted on the slides using Hoyer's solution and dried up in an oven at 45 °C. Specimens were identified and drawn with the aid of NIKON E600 phase contrast microscopes.
HOLOTYPE female (no. XZ-P09030) collected from bush forest, Sangduo town, Leiwuqi County, Changdu District, Tibet Autonomous Region (Xizang), CHINA, N 31° 12′ 21″ E 96° 35′ 10″, 3,964 m asl, 14-VIII-2009, coll. W. J. Chen. Paratype. 1 male (no. XZ-P09028), collected from the soil sample between the rock beside the road, Tuoba town, Jiangda County, Changdu District, Tibet Autonomous Region (Xizang), China, 31° 17′ 42″ N 97° 30′ 24″ E, 3926 m elev., 12-VIII-2009, coll. W. J. Chen. Type specimens are deposited at Shanghai Entomological Museum (SEM).
Adult body length 1050 µm (n = 2), pale yellow in color (Fig. 1).
Head. Elliptic, length 100 µm, width 75 µm. Setae sd4 and sd5 short and sensilliform, sd6 absent (Fig. 2). Pseudoculus length 8 µm, PR = 12.5 (Fig. 3). Maxillary gland with smooth, heartshaped calyx. Posterior filament of maxillary gland length 16 µm, CF = 6.4 (Fig. 4). Maxillary palps with 2 subequal sensilla (Fig. 5). Labial palps with 3 setae and one short, slender sensillum (Fig. 6). Frontal pore (fp) present on dorsal side of head (Fig. 2).
Foretarsus. Length 76 µm, claw length 16 µm, TR = 5.4; empodium length 5 µm, EU = 0.38. Dorsal sensillum t1 baculiform, t2 thin and long, t3 short and lanceolate, BS = 0.50. All other sensilla slender, parallel sided, with exception of broad sensillum a. Exterior sensillum a long, its apex reaching base of d, b and c on same level, b longer than c and surpassing base of β4, d closer to c than to e, e slender, f and g reaching base of claw. Interior sensillum a' broad, short, close to t1, not reaching base of b' (Fig. 9), b' short, its apex surpassing base of δ55, and c' short, its apex reaching base of δ6. (Figs. 7 and 8). Relative length of sensilla: t3 < t1 < a' < b' < (g = c') < t2 < (a = d) < e < (c = f) < b. Seta δ1 and δ4 setiform, 5 µm and 12 µm in length respectively. Pores present on exterior part of foretarsi near bases of seta α3 and sensillum g. Claw slender, without inner flap. Empodial appendage 5 µm in length. Length of middle tarsus 35 µm, claw length 15 µm. Length of hind tarsus 37 µm, claw length 16 µm.
Thorax. Thoracic chaetotaxy formula given in Table 1. On pronotum, length ratio of 1:2 as 1.5:1. On meso- and metanotum, A2 subequal to M, 8 µm in length. Accessory setae P1a and P2a on meso- and metanotum short and sensilliform (Fig. 11). Length ratio of P1: P1a: P2 on mesonotum as 4.3: 1: 5.0. Seta P5 on mesonotum pin-shaped, on metanotum rudimentary (Fig. 10). Setae A2 and M2 on prosternum, A2 on meso- and metasternum sensilliform (Figs. 12–14). Mesonotum with pores al and sl, metanotum with pore sl only (Fig. 10). Pro-, meso- and metasternum without pores. (Figs. 12 and 13).
Abdomen. Abdominal chaetotaxy given in Table 1. Tergites I–VI with 3 pairs of anterior setae (Figs. 15 and 16), VII with one pair of anterior setae (Fig. 17). Seta P3 on tergites II–VI anterior to other P-row setae (Fig. 16), and the same level with other P-row setae on tergites I and VII (Figs. 15 and 17). Sternite I with one pair of P-setae (Fig. 19). Accessory setae on tergites and sternites I–VII short, sensilliform (Figs. 18 and 21), 4– 5 µm in length.
Tergite I with pores psm (Fig. 15). Tergites IIVI with pores psm and al (Fig. 16), VII with pores psm, ps1 and al (Figs. 17 and 24). Pore psm on tergite VIII with several surrounding teeth (Fig. 26). Tergites IX-XI without pores, XII with single median pore on serrate line (Fig. 26). Sternites IIV without pores (Figs. 19, 20 and 22). Membrane between tergites and sternites IV-VI each with 1+1 anteromembranal (amb) pore (Figs. 22 and 23). Sternites V–VI with a pair of pores close to P1 (Fig. 23), sternite VII with single asymmetrically pore close to one of P1 (Fig. 24), sternites VIII–XI without pores (Fig. 25). Sternite XII with 1+1 anterolateral pores (Fig. 25).
Abdominal appendages with 4, 2, 2 setae, 2 glands and 2 pores present on each of abdominal appendage I (Figs. 19 and 20). Length ratio of subapical and apical seta of second and third appendages as 1.9:1 (Figs. 20). Striate band on abdominal segment VIII reduced (Figs. 25 and 26). Comb on abdomen VIII rectangular, with 6 short teeth (Fig. 29). Lateral and posterior margins of tergites and sternites VIII-XI smooth. Hind margin of tergite XII with few teeth. Seta 1 and la on tergite IX length 15 and 22 µm respectively..
The species name was derived from Tibet Autonomous Region (Xizang) where the species were collected.
China (Tibet Autonomous Region).
Baculentulus xizangensis sp. nov. is characterized by the presence of sensillum b' on foretarsus, short sensillum a', one pair of A-setae (AS) on tergite VII, one pair of P-setae (P1) on sternite I, and comb with few teeth and straight hind margin.
Baculentulus xizangensis sp. nov. is similar to B. ogawai (Imadaté 1965) from Thailand, B. numatai (Imadaté 1965) from Nepal, B. africanus (Nosek 1976), B. evansi (Condé 1961) and B. nyinabitabuensis (Condé 1961) from Africa in having foretarsal sensilla b' present and only one pair of A-setae on tergite VII. It differs from B. ogawai in having one pair P-setae on sternite I (2 pairs in B. ogawai respectively), in the short sensillum a', not reaching base of b' (a' surpassing base of 6' in B. ogawai), in the length of sensillum b', not reaching base of c' (b' surpassing base of c' in B. ogawai), and in the comb with few teeth and straight hind margin (comb with 14 teeth and hind margin oblique in B. ogawai). It differs from B. numatai in one pair of P-setae on tergie I and 8 pairs of P-setae on tergites II–VI (2 and 9 pairs in B. numatai respectively), in the presence of A1 seta on tergite VIII (A1 absent in B. numatai ). It differs from B. africanus, B. evansi and B. nyinabitabuensis in having 3 pairs of A-seta on tergite VIII (2 pairs in those 3 species), and in the 7 pairs of setae on tergite IX (6 pairs in those 3 species). It also differs from B. africanus in the short sensillum a', not reaching base of b' (a' reaching base of b' in B. africanus), from B. evansi and B. nyinabitabuensis in the short posterior filament of maxillary gland (posterior filament of maxillary gland long in B. evansi and B. nyinabitabuensis), and in the sensillum a' situated at same level to t1 (posterior to t1 in B. evansi, anterior to t1 in B. nyinabitabuensis ).
Except those 5 species mentioned above, B. celisi (Condé, 1955) from Congo, B. tuxeni (Nosek & Hüther 1974) and B. becki (Tuxen 1976) from Brazil, and B. chiangmaiensis Nakamura & Likhitrakarn, 2009 from Thailand also have foretarsal sensilla b' present. The 10 species of Baculentulus with sensillum b' on foretarsus can be distinguished by the following key.
ADULT CHAETOTAXY OF BACULENTULUS XIZANGENSIS SP. NOV.
KEY TO BACULENTULUS SPP. WITH FORETARSAL SENSILLUM B'
1. Tergite VII with one pair of A-setae 2
—. Tergite VII with 2 to 4 pairs of A-setae 7
2. Tergites I–VI with seta P1a B. numatai (Imadaté, 1965); Nepal
—. Tergites I–VI without seta P1a' 3
3. Tergite VIII with 3 pairs of A-setae 4
—. Tergite VIII with 2 pairs of A-setae 5
4. Sternite I with one pair of P-setae, sensillum a' not reaching base of b' B. xizangensis sp. nov.; China (Tibet)
–—. Sternite I with 2 pairs of P-setae, sensillum a' surpassing base of b' B. ogawai (Imadaté, 1965); Thailand
5. Foretarsal sensillum a reaching base of seta y3 B. africanus (Nosek, 1976); Rwanda
—. Foretarsal sensillum a not reaching base of seta y3 6
6. Small body size (800 µm), accessory setae on tergites about 1/4 length of principal setae B. evansi (Condé, 1961); Uganda
—. Large body size (1050 – 1400 µ), accessory setae on tergites about 1/9 length of principal setae B. nyinabitabuensis (Condé, 1961); Uganda
7. Tergite I–VI with seta P1a' B. chiangmaiensis Nakamura & Likhitrakarn, 2009; Thailand
—. Tergite I–VI without seta P1a 8
8. Tergite VII with 4 pairs of A-setae B. tuxeni (Nosek & Huther,1974); Brazil
—. Tergite VII with 3 pairs of A-setae 9
9. Foretarsal sensillum b short, not reaching base of seta y2 B. becki (Tuxen, 1976); Brazil
—. Foretarsal sensillum b long, surpassing base of f B. celisi (Condé, 1955); Congo
We give our cordial gratitude to Osami Nakamura (Japan) and Julia Shrubovych (Ukraine) for generously providing some important references. We thank Dr. Wan-Jun Chen for the collection of specimens. This study was supported by the National Natural Sciences Foundation of China (no: 31071887, 31201706) and the Innovative Program for The Excellent Youth Talents of Shanghai Institutes for Biological Sciences (no: 2011KIP305).