Symphylella minuta Jin & Bu, 2020

Jin, Ya-Li & Bu, Yun, 2020, Two new species of the genus Symphylella (Symphyla, Scolopendrellidae) from East China, ZooKeys 1003, pp. 1-18 : 1

Symphylella minuta Jin & Bu sp. nov. Figures 1 , 2 , 3 , Tables 1, 2, 3

Diagnosis.

Symphylella minuta sp. nov. is characterized by the delicate and minute body, well-developed but thin central rod with a vestige of a transverse suture in the middle, eight setae on first tergite, pointed processes on tergites, and short cerci with sparse setae.

Material examined.

Holotype, female (slide no. JS-WX-SY2017020) (SNHM), China, Jiangsu Province, Wuxi City, Daji Mountain, extracted from soil samples of broad-leaf forest, alt. 5 m, 31°32'N, 120°12'E, 9-X-2017, coll. Y. Bu. Paratypes, 1 female (slide no. JS-WX-SY2017031) (SNHM), same data as holotype; 2 females (slides no. JS-WX-SY2020001, JS-WX-SY2020002) (SNHM), ibidem, 14-VII-2020, coll. Y. Bu; 3 females (slides no. SH-DJS-SY2015112, SH-DJS-SY2015114) (SNHM), China, Shanghai, Dajinshan Island, extracted from soil samples of broad-leaf forest, alt. 103 m, 30°41'N, 121°26'E, 22-IX-2015, coll. Y. Bu & Y. L. Jin; 3 females (slides no. ZJ-JLS-SY2019001, ZJ-JLS-SY2019002) (SNHM), China, Zhejiang, Lishui City, Suichang County, Jiulongshan National Nature Reserve, extracted from soil samples of broad-leaf forest, alt. 703 m, 28°13'N, 118°31'E, 27-V-2019, coll. Y. Bu & J. Y. Li. 1 female (slide no. ZJ-GTS-SY2012005) (SNHM), China, Zhejiang, Gutian Mountain, extracted from soil samples of broad-leaf forest, alt. 800 m, 29°15'N, 118°06'E, 11-IV-2012, coll. Y. Bu et al.; Non-type specimens: 7 juveniles with 8-10 pairs of legs, China, Shanghai, Dajinshan Island, extracted from soil samples of broad-leaf forest, alt. 103 m, 30°41'N, 121°26'E, 22-IX-2015, coll. Y. Bu & Y. L. Jin; 1 juvenile with 10 pairs of legs, China, Zhejiang, Lishui City, Suichang County, Jiulongshan National Nature Reserve, extracted from soil samples of broad-leaf forest, alt. 703 m, 28°13'N, 118°31'E, 27-V-2019, coll. Y. Bu & J. Y. Li; 3 juveniles with 9-10 pairs of legs, China, Zhejiang, Gutian Mountain, extracted from soil samples of broad-leaf forest, alt. 800 m, 29°15'N, 118°06'E, 11-IV-2012, coll. Y. Bu et al.; 1 juvenile with 10 pairs of legs, ibidem, 24-IV-2013; 1 juvenile with 10 pairs of legs, ibidem, 16-V-2012; 1 juvenile with 9 pairs of legs, ibidem, 19-VI-2012; 1 juvenile with 7 pairs of legs, ibidem, 15-VII-2012; 2 juveniles with 7 and 9 pairs of legs, ibidem, 14-X-2012; 2 juveniles with 9-10 pairs of legs, ibidem, 17-XI-2012, coll. Y. Bu et al.

Description.

Adult body 1.5 mm long in average (1.2-2.2 mm, n = 8), holotype 1.4 mm (Fig. 1A ).

Head length 150-170 μm, width 133-158 μm, with widest part somewhat behind the middle on a level with the points of articulation of mandibles. Central rod well developed but thin, with a vestige of a transverse suture in the middle. Anterior branches normally developed, without median branches. Dorsal side of head moderately covered with setae of different length, longest setae (18-25 μm) located most anterior on head, at least 3.0 times as long as central ones (4-6 μm). Cuticle of anterolateral part of head with rather coarse granules, around Tömösváry organ with moderate granules, other area with fine and faint granulation (Fig. 1F ).

Tömösváry organ globular, diameter 11-14 μm, about half of greatest diameter of third antennomere (24-27 μm), opening small and round (5-8 μm), with distinct vertical inner striate (Fig. 1F ).

Mouthparts. Mandible with two fused lamellae and 12 teeth in total (Fig. 3A ). First maxilla has two lobes, inner lobe with four hooked teeth, palp bud-like and pointed (Fig. 3D ). Anterior part of second maxilla with many small protuberances each carries one seta, distal setae thicker and spiniform; posterior part with sparse setae. Cuticle of maxilla and labium covered with dense pubescence (Fig. 1G ).

Antennae with 14-19 antennomeres (holotype with 19 on left, 14 on right), length 320-380 μm (350 μm in holotype), about 0.2 of body length. First antennomere cylindrical, greatest diameter almost two times wider than long (23-27 μm, 14-16 μm), with three or four setae on inner side, longest inner seta 8-10 μm, outer side without seta. Second antennomere wider (22-29 μm) than long (16-19 μm), with six to eight setae evenly inserted around the antennal wall with interior setae (10-18 μm) slightly longer than exterior ones (6-7 μm). Chaetotaxy of third antennomere similar to preceding ones. Setae on proximal antennomeres longer than on distal ones. Proximal antennomeres with only primary whorl of setae, middle and subapical antennomeres with secondary whorl setae present. Three kinds of sensory organs observed on antenna: rudimentary spined sensory organs on dorsal side of middle antennomeres (Figs 1C , 3C ); cavity-shaped organs on antennomeres 5-19 (Figs 1C , 3C ); bladder-shaped organs on antennomeres 7-14 next to apical one increasing in number on subapical antennomeres to a maximum of 12 (Figs 1D, E , 3C ). Apical antennomere subspherical, somewhat wider than long (width 22 μm, length 13-17 μm), with 10-13 setae on distal half; three or four spined sensory organs consisting of three or four curved spines around a central pillar in depressions on distal surface (Figs 1E , 3B ). All antennomeres covered with short pubescence. Chaetotaxy and sensory organs of antennae of holotype are given in Table 1 .

Trunk with 17 dorsal tergites. Tergites 2-13 and 15 each with one pair of sharp triangular processes. Length from base to tip of processes distinctly longer than its basal width except for the tergites 4, 7, 10 and 13, in which processes are almost as broad as long; basal distance between processes of tergites distinctly longer than their length from base to tip (Table 2 ). All processes with end-swellings. Anterolateral setae on all tergites longer than other lateromarginal setae, about 0.6-0.7 of the length of processes on same tergite. Inserted setae (setae between inner basal seta and apical setae) absent. All tergites pubescent (Fig. 2A-H ).

Tergites. Tergite 1 reduced, with eight short setae in a row. Tergite 2 complete, with two triangular posterior processes, four lateromarginal setae, one central seta, anterolateral setae 0.6-0.7 of length of process, longer than other lateromarginal ones, processes 1.1 or 1.2 times as long as broad, basal distance between processes 1.2-1.7 times as long as their length (Fig. 2A ). Tergite 3 complete, broader and longer than preceding one with ratios of 0.6-0.8, 1.2-2, and 1.2-1.5 respectively, four or five lateromarginal setae (Fig. 2B ). Tergite 4 broader than tergite 3, with ratios 0.7-0.9, 0.9-1, and 1.7-2.2 respectively, four lateromarginal setae (Fig. 2C ). Chaetotaxy of tergites 5-7, 8-10, and 11-13 similar as tergites 2-4 (Fig. 2D, E ). Pattern of alternating tergite lengths of two short tergites followed by a long tergite only disrupted at the caudal end (Table 2 ). Tergites 14 and 16 without processes, with 5-14 and 4-13 setae respectively (Fig. 2F, H ). Tergite 17 with 6-17 setae. Chaetotaxy and measurements of tergites are given in Tables 2 , 3 .

Legs. First pair of legs reduced to two small hairy cupules, each with two long setae (Fig. 1H ). Basal areas of legs 2-12 each with four to six setae (Figs 1H, I , 2I ). Leg 12 about 0.1 of the body (Fig. 3G ). Trochanter 1.1-1.7 times longer than wide (30-46 μm, 24-35 μm), with six subequal setae totally. Femur almost as long as wide (19-25 μm, 20-23 μm), with four setae, three dorsal ones (9-12 μm) distinctly longer than ventral one (5-6 μm); femur pubescent dorsally, laterally with cuticular thickenings in pattern of scales. Tibia nearly 1.2-2.3 times longer than wide (20-26 μm, 11-18 μm), with four or five dorsal setae and one or two ventral setae, longest one 10-12 μm. Tarsus subcylindrical, 2.3-3.0 times as long as wide (16-30 μm, 10-12 μm) with four dorsal setae: two straight and protruding, two slightly curved and depressed; longest setae (20-22 μm) about same length of greatest width of podomere; one to three ventral setae close to claw and distinctly shorter than dorsal ones. Claws curved, anterior one somewhat longer than posterior one, the latter more curved than the former. All legs covered with dense pubescences except areas with cuticular thickenings.

Coxal sacs present at bases of legs 3-9, fully developed, each with three to five setae on surface (Fig. 1I ). Relevant area of leg 2, 11 and 12 replaced by two, two or three, and one to three setae respectively (Figs 1H , 2I ).

Styli present at base of legs 3-12, subconical (length 2-4 μm, width 2-3 μm), basal part with straight hairs; with a distal blunt apex (2-3 μm) (Figs 1I , 2I , 3F ).

Sense calicles with smooth margin to pit, about same length as outer diameter. Sensory seta inserted in cup center, extremely long (90-100 μm).

Cerci short and stout (Figs 1A , 2J , 3E ), about one-third of head and one-half of length of leg 12, 2.5 times as long as its greatest width (48-55 μm, 20-22 μm), inserted with sparse subequal setae, six to eight dorsal, five or six ventral, one or two outer, most setae straight, a whorl of six distal setae slightly curved, longest outer seta (14-16 μm) slightly longer than greatest width of cerci, terminal area (8-17 μm) short, 0.3-0.6 time as long as greatest width of cerci, circled by six to eight layers of curved ridges, terminal seta (20-23 μm) long, distinctly longer than terminal area.

Etymology.

The species name " minuta " refers to the delicate and minute body of the species.

Distribution.

China (Jiangsu, Shanghai, Zhejiang).

Remarks.

Symphylella minuta sp. nov. is similar to S. oligosetosa Scheller, 1971 from India and Sri Lanka in the shape of the central rod on head and the shape and chaetotaxy of the tergites. They can be distinguished by the chaetotaxy of the first tergite (eight setae in S. minuta sp. nov. vs six in S. oligosetosa ), shape of the processes (pointed and with swollen ends in S. minuta sp. nov. vs strongly pointed and without swollen ends in S. oligosetosa ), shape and chaetotaxy of cerci (short and stout, about 2.5 times as long as wide in S. minuta sp. nov. vs slender, 3.5-3.6 times as long as wide in S. oligosetosa ). It is also similar to S. abbreviata Scheller, 1971 from Sri Lanka in the chaetotaxy of the tergites and shape of the processes, but can be easily separated by the chaetotaxy of the first tergite (with eight setae in S. minuta sp. nov. vs six setae in S. abbreviata ), shape of the third tergite (without indentation in S. minuta sp. nov. vs with a distinct middle lateromarginal indentation in S. abbreviata ), shape of cerci (tapering in S. minuta sp. nov. vs with outer side strongly bulging in S. abbreviata ).

Figures

Figure 1. Symphylella minuta sp. nov. A habitus B left antenna, 1 st- 6 th antennomeres, dorsal view C distal five antennomeres, dorsal view D distal five antennomeres, ventral view E distal five antennomeres, show lateral organs F head, right side, dorsal view G head, ventral view H first pair of legs (arrows indicate the reduced legs) and coxa of leg 2 I styli, and coxal sacs on base of 3 rd leg (arrows indicate styli). Scale bars: 100 μm (A); 20 μm (B-I).

Figure 2. Symphylella minuta sp. nov. A 1 st and 2 nd tergites (als-anterolateral seta, as-apical seta, cs-central seta, ibs-inner basal seta, lms-lateromarginal seta) B 3 rd tergite C 4 th tergite D 5 th tergite E 13 th tergite F 14 th tergite G 15 th tergite H 16 th tergite I styli and base of 4 th leg (arrows indicate styli) J cerci, dorsal view. Scale bars: 20 μm.

Figure 3. Symphylella minuta sp. nov. A mandible B right apical antennomere, dorsal view C right 14 th antennomere, dorsal view D first maxilla E right cercus, dorsal view F stylus on base of 4 th leg, right side G 12 th leg. Scale bars: 20 μm (A-E, G); 5 μm (F).