Two new species of the genus Symphylella (Symphyla, Scolopendrellidae) from Tibet, China

Abstract The Symphyla of Tibet are studied for the first time. Symphylellamacroporasp. n. and Symphylellazhongisp. n. from southeastern Tibet are described and illustrated. Symphylellamacroporasp. n. is characterized by large, elongated oval openings of the Tömösváry organ with its inner margins covered by minute irregular teeth, rudimentary spined sensory organs present on the dorsal side of most antennal segments, and cerci with numerous long and slightly curved setae. Symphylellazhongisp. n. is characterized by a globular Tömösváry organ with a small and roundish opening, mushroom-shaped sensory organs present on apical antennal segments, and by having tergal processes longer than their basal width with ovoid swollen ends. The newly described species are compared to the morphologically closest congeners: S.javanensis, S.asiatica, S.multisetosa, and S.simplex. A key for 43 species of the genus is also provided.


Introduction
Knowledge of the myriapod class Symphyla from China is poor. Only two species have been recorded until now: Hanseniella caldaria  from Zhejiang province and Scolopendrellopsis glabrus  from Zhejiang and Hainan provinces (Zhang and Wang 1992;Bu and Jin 2018;Jin and Bu 2018). There are no records of Symphyla from Tibet so far.
During an investigation of soil arthropods in southeast Tibet in November 2015, plenty of specimens of the family Scolopendrellidae were obtained. Among them, two new species of the genus Symphylella Silvestri, 1902 were identified and are described here.

Materials and methods
Specimens were collected by Berlese-Tullgren funnels and preserved in 80% ethanol. They were mounted under slides using Hoyer's solution and dried in an oven at 60 °C. Observations were performed under a phase-contrast microscope (Leica DM 2500). Photographs were taken by a digital camera installed on the microscope (Leica DMC 4500). Line drawings were done using a drawing tube. All specimens are deposited in the collections of Shanghai Natural History Museum (SNHM), Shanghai, China.

Taxonomy
Family Scolopendrellidae Bagnall, 1913 Genus Symphylella Silvestri, 1902 Type species: Symphylella isabella (Grassi, 1886) Diagnosis. Central rod on head broken and distinct in both anterior and posterior portions. Antennae with 14-22 segments. Trunk with 17 tergites or fewer, with the first tergite vestigial. Triangular processes present on posterior margins of 13 tergites. Belts of longitudinal striae between processes absent. First pair of legs vestigial, as small protuberances with a few setae. Styli rudimentary. Coxal plates with sacs only present on 3 rd -9 th legs. Cerci relatively long, terminal area with transverse stripes, ending in a single long seta (Bagnall 1913;Szucsich and Scheller 2011).
Distribution. The genus Symphylella currently includes 47 extant subcosmopolitan species (Szucsich and Scheller 2011;Jin and Bu 2018). It has previously been recorded from China, but the species have never been identified (Zhang and Wang 1992).
small protuberances which carry one seta each, distal setae thickened; posterior part with sparse setae. Cuticle of maxilla and labium covered with pubescence.
interior setae (23-26 μm) slightly longer than exterior ones (16-19 μm). Chaetotaxy of 3 rd segment like preceding ones. Setae on basal segments slender and on distal segments shorter. Basal segments of antennae with only primary whorl of setae, in middle and subapical segments with several minute setae in secondary whorl. Three kinds of sensory organs on most antenna segments: rso on dorsal side of most segments (Figs 2C, 2E); co on dorsal side of 3 rd -21 th segments; bo on subapical 5-9 segments (Figs 1B, 2C, 2D). Apical segment subspherical, somewhat wider than long (width 28-32 μm, length 24-26 μm), with 13-15 setae on distal half and 2 baculiform organs on apex, 4-7 so consisting of 3-4 curved spines around a central pillar in depressions in distal surface (Figs 2C,2D). All segments covered with short pubescence. Chaetotaxy and sensory organs of antennae are given in table 1.
Trunk with 17 tergites. Most tergites overlap, with intertergal zones present between adjacent tergites, except for borders between 14 th and 15 th , as well as 16 th and 17 th tergite. Tergites 2-13, and 15 each with one pair of triangular processes. Basal distance between processes of 4 th -13 th and 15 th tergites longer than their length from base to tip, and the latter shorter than its basal wide (Table 2). Anterolateral setae of 2 nd , 3 rd , 4 th , 6 th , 7 th , 9 th and10 th tergites distinctly longer than other lateromarginal setae, that of 5 th , 8 th , 11 th -13 th and 15 th subequal or slightly longer than other lateromarginal setae. Triangular processes without ovoid swollen ends (Fig. 1G). One to three inserted setae (setae between inner basal seta and apical seta). All tergites pubescent.
Coxal sacs present at bases of 3 rd -9 th pairs of legs, fully developed, each with 4 setae on its surface (Fig. 1F).
Etymology. The species name macropora is referring to the large opening of the Tömösváry organ.
Distribution. Known only from the type locality.
Remarks. Symphylella macropora sp. n. is most similar to S. javanensis Scheller, 1988 from Java in the shape of tergites and pro cesses, leg 12 and sensory organs on antennae. However, it can be readily distinguished from the latter by the shape of Tömösváry organ (oval, openings large and elongated with inner margins covered by minute irregular teeth Table 3. Measurements of tergites and processes (mean ± se, n = 11) (in μm). vs subspherical, diameter of opening about half of the organ in S. javanensis), central rod (both anterior and posterior portions distinct in S. macropora sp. n. vs anterior half and anterior branches very thin with traces in S. javanensis), and the stylus (with blunt apex in S. macropora sp. n. vs with truncate apex in S. javanensis). It is also closely related to S. asiatica  from Indiaand Sri Lanka in the shape and chaetotaxy of tergites 1-3, leg 12 and the sensory organs on antenna, but easily distinguished by characters of Tömösváry organ (openings very small in S. asiatica), and the cerci (most setae subequal length and slightly curved in S. macropora sp. n. vs long and erect setae on dorsal, ventral and outer sides arranged in one or two rows in S. asiatica). Diagnosis. Symphylella zhongi sp. n. is characterized by a globular Tömösváry organ with small and roundish opening, processes on tergites mostly longer than their basal width, ovoid swollen ends of processes, and mushroom-shaped sensory organs present on apical antennal segments. Material Examined. Holotype, female (slide no. XZ-SY2015049) (SNHM), China, Tibet, Linzhi City, Bomi county, Songzong town, extracted from soil samples from broadleaf forest, alt. 3000 m, 29°76'N, 95°96'E, 7-XI-2015, coll. Y. Bu & G. Yang. Paratypes, 2 females (slides nos. XZ-SY2015047-XZ-SY2015048) (SNHM), same date as holotype. Other materials: 3 juvenile with 8 or 9 pairs of legs (slides nos. XZ-SY2015050-XZ-SY2015052) (SNHM), same date as holotype.
Head length 250-262 μm, width 262-287 μm, with widest part somewhat behind the middle on a level with the points of articulation of mandibles. Central rod distinct in both anterior (65-70 μm) and posterior (75-90 μm) portions, with a middle knot. Anterior branches well developed, median branches vestigial. Dorsal side of head moderately covered with setae of different length, longest setae (27-35 μm) located most anterior on head, at least 3.0 times as long as central ones (8-11 μm). Cuticle at anterolateral part of head with rather coarse granulation. Tömösváry organ surrounded by fine granulation, other area with faint dense granulation (Fig. 3D).
Mouthparts. Mandible with two fused lamellae and 11 teeth in total (Fig. 4A). First maxilla has two lobes, inner lobe with four hook-shaped teeth, palp bud-like with one distal point close to outer lobe (Fig. 4B). Anterior part of second maxilla with many small protuberances which carry one seta each, distal setae more thick and hard; posterior part with sparse setae. Cuticle of maxilla and labium covered with pubescence.
Trunk with 17 dorsal tergites. Most tergites overlap, with intertergal zones present between adjacent tergites, except for borders between 14 th and 15 th , as well as 16 th and 17 th tergite. Tergites 2-13 and 15 each with one pair of triangular processes. Length from base to tip of processes somewhat longer than its basal width except for the 4 th , 7 th , 10 th and 13 th tergites, where processes are broader than long; basal distance between processes of 4 th -13 th and 15 th tergite longer than their length from base to tip (Table 5). Triangular processes with ovoid swollen ends (Fig. 3I). Anterolateral setae of 2 nd , 3 rd , 4 th , 6 th , 7 th , 9 th and10 th tergite dis- tinctly longer than other lateromarginal setae, that of 5 th , 8 th , 11 th -13 th and 15 th subequal or slightly longer than other lateromarginal. One to two inserted setae. All tergites pubescent.
Coxal sacs present at bases of 3 rd -9 th pairs of legs, fully developed, each with 4 setae on surface (Fig. 3G).
Etymology. We dedicate this new species in honor of the late Professor Zhong Yang  who was an eminent botanist from Fudan University, for his great contribution to the knowledge of flora and biodiversity of Tibet.
Distribution. Known only from the type locality. Remarks. Symphylella zhongi sp. n. is most similar to S. multisetosa  in the shape of the Tömösváry organ, as well as the shape and chaetotaxy of the tergites 1-4, 1 st leg, but it deviates distinctly in the shape of the ends of the processes (with ovoid swollen ends in S. zhongi sp. n. vs without ovoid swollen ends in S. multisetosa), chaetotaxy of the cerci (most setae subequal length and slightly curved in S. zhongi sp. n. vs long, straight, erect setae on dorsal, ventral, and outer sides of cerci arranged in one or two rows in S. multisetosa). It is also similar to S. simplex  in the shape and chaetotaxy of first two tergites, sensory organs of antennal segments and 1 st leg, but differs in the shape of 1 st antennal segment (moderate in S. zhongi sp. n. vs very short in S. simplex), chaetatoxy of 3 rd tergite (8 or 9 lateromarginal setae in S. zhongi sp. n. vs 11 or 12 in S. simplex) and 4 th tergite (6 or 7 lateromarginal setae in S. zhongi sp. n. vs 8 in S. simplex), chaetotaxy of cerci (8-10 longish setae protruding, others short and depressed in S. simplex).
The new species is compared with similar species in Table 7.