Symphylella longispina Jin & Bu, 2023

Jin, Ya-Li & Bu, Yun, 2023, Two new species of the genus Symphylella (Symphyla, Scolopendrellidae) from China and the significance of the frons chaetotaxy, ZooKeys 1138, pp. 143-160 : 143

Symphylella longispina Jin & Bu sp. nov.

Figs 4 , 5

Diagnosis.

Symphylella longispina sp. nov. is characterized by apparently thickened labrum, distinctly long proximal spines on the pars molaris of the mandible, eight macrosetae arranged as 4/2/2 on the frons, 3+3 setae on the first tergite and narrow triangular processes on tergites.

Material examined.

Holotype: female (slide no. XJ-SY20160003) (SNHM), China, Xinjiang, Bole City, Hariturege National Forest Park, extracted from soil samples from the forest of Populus euphratica , alt. 1125 m, 40°08'N, 81°46'E, 31-VIII-2016, coll. C. W. Huang.

Paratypes: 5 females (slides no. XJ-SY20160001, XJ-SY20160002, XJ-SY20160004, XJ-SY20160005, XJ-SY20160006) (SNHM), same data as holotype .

Description.

Adult body 2.4 mm long in average (1.8-2.6 mm, n = 6), holotype 2.4 mm (Fig. 4A ).

Head length 210-225 μm, width 190-225 μm, with widest part on equal level of points of articulation of mandibles. Central rod well developed but thin, divided into 2 portions by node-like sub-median interruption, with anterior 48-50 μm and posterior 60-70 μm. (Fig. 4B ). Dorsal side of head moderately covered with setae of different lengths. Frons with 5+5 lateral setae, 8 macrosetae (23-28 μm) arranged as 4/2/2 and 2.8-3.7 times as long as antero-central seta (a0) (Fig. 5H ), and 16 moderate setae (14-17 μm) (Figs 4B , 5H ). Cuticle on anterolateral part of head with coarse granules (Fig. 4B ).

Tömösváry organ globular, diameter 12-16 μm, shorter than half of greatest diameter of third antennomere (33-35 μm), opening small and round (4-6 μm), with distinct vertical inner striae (Fig. 4B, E ).

Mouthparts. Labrum apparently thickened and protruding (Figs 4C , 5H ). Mandible similar to S. macrochaeta sp. nov., but pars molaris with extremely long proximal spines (Figs 4C , 5A ). First maxilla has 2 lobes, inner lobe with 6 hook-shaped teeth and pubescent apically, palp pointed and slightly incurved (Fig. 5B ). Anterior part of second maxilla with many small protuberances, each carrying 1 seta, distal setae thick; posterior part with sparse setae. Cuticle of second maxilla covered with dense pubescence.

Antennae with 16-20 antennomeres (holotype with 18), about 0.2 of body length. First antennomere cylindrical, almost same as wide as long (width 24-28 μm, length 25-28 μm), with 5-7 setae in 1 whorl, longest inner seta 14-15 μm (Figs 4E , 5C ). Second antennomere wider (29-33 μm) than long (24-25 μm), with 8 setae evenly inserted around antennal wall with interior setae (15 μm) slightly longer than exterior ones (11 μm) (Figs 4E , 5C ). Chaetotaxy of third antennomere similar to preceding ones. Setae on proximal antennomeres longer and on distal antennomeres shorter. Proximal antennomeres with only primary whorl of setae, in middle and subapical antennomeres with several minute setae in secondary whorl. Four kinds of sensory organs observed on antenna: rudimentary spined sensory organs on dorsal side of most antennomeres except first antennomere (Fig. 5C, D ); spined sensory organs only present on terminal antennomere (Fig. 5D, E ); cavity-shaped organs on antennomeres 10 and 11 next to apical one, increasing in number to 4 in maximum (Fig. 5D ); bladder-shaped organs irregular, round, oval or curved, present on antennomeres 5 and 6 next to apical one increasing in number on subdistal antennomeres to 13 in maximum (Fig. 5D, E ). Apical antennomere subspherical, somewhat wider than long (width 25-28 μm, length 15-20 μm), five spined sensory organs consisting of 3 or 4 curved spines around a central pillar and 13-17 setae on distal half (Fig. 5D, E ). All antennomeres covered with short pubescence. Chaetotaxy and sensory organs of antennae of holotype are given in Table 4 .

Trunk with 17 tergites. Tergites 2-13 and 15 each with 1 pair of triangular processes. Length from base to tip of processes slightly longer than its basal width except for tergites 4, 7, 10 and 13, in which processes almost as broad as long; basal distance between processes of tergites distinctly longer than their length from base to tip (Table 5 ). All processes with distinct rounded end-swellings (Fig. 4D, F, G ). Anterolateral setae of tergites 2, 3, 4, 6, 7, 9 and 10 distinctly longer than other lateromarginal setae, that of tergites 5, 8, 11-13 and 15 subequal or slightly shorter than longest ones of other lateromarginal (Fig. 4D, F, G ). Anterolateral setae of tergites shorter than or subequal to process of same tergite. Processes with 1 inserted seta (is) (Fig. 4F ). All tergites pubescent (Fig. 4F ).

Tergites. Tergite 1 reduced, with 3+3 subequal setae (Fig. 4D ). Tergite 2 complete, with 2 triangular posterior processes, 5 or 6 lateromarginal setae, 1 inserted seta, 1 central seta (Table 5 ), anterolateral setae 0.7-0.8 of length of process, processes 1.1-1.2 times as long as broad, basal distance between processes 1-1.2 times as long as their length (Fig. 4D, F ). Tergite 3 complete, broader and longer than preceding one with ratios of 0.7-0.9, 1.1-1.3, and 1.1-1.3 respectively, 7 or 8 lateromarginal setae (Fig. 4D ). Tergite 4 broader than tergite 3, with ratios 1-1.2, 0.9-1, and 1.3-1.9 respectively, 5 lateromarginal setae (Fig. 4G ). Chaetotaxy of tergites 5-7, 8-10, and 11-13 similar as tergites 2-4. Pattern of alternating tergite lengths of 2 short tergites followed by 1 long tergite only disrupted at caudal end (Table 6 ). Tergites 14 and 16 without processes and with 15-18 and 10-14 setae respectively. Tergite 17 with 10-14 setae. Chaetotaxy and measurements of tergites are given in Tables 5 and 6 .

Legs. First pair of legs reduced to 2 small hairy cupules, each with 1 long seta (9-11 μm) (Fig. 4H ). Basal areas of legs 2-12 each with 3-5 setae. Leg 12 about 0.6-0.8 of head length (Fig. 5I ), trochanter 1.3-1.6 times longer than wide (45-50 μm, 32-36 μm), with 6 or 7 subequal setae in total; femur almost as long as wide (25-33 μm, 25-30 μm), with 5 setae, longest dorsal seta 17-20 μm in length, pubescent dorsally, laterally with cuticular thickenings in pattern of scales; tibia nearly 1.3-1.9 times longer than wide (28-40 μm, 21-23 μm), with 6 or 7 setae, longest dorsal one 14-18 μm; tarsus subcylindrical, 3-3.5 times as long as wide (45-48 μm, 13-16 μm) with 6 dorsal setae: 4 straight and protruding, 2 slightly curved and depressed, longest setae (14-17 μm) about same length of greatest width of podomere, 2 ventral setae close to claw and distinctly shorter than dorsal ones. Claws curved, anterior one broader than posterior one. All legs covered with dense pubescence except areas with cuticular thickenings.

Coxal sacs present at bases of legs 3-9, fully developed, each with 4 setae on surface. Corresponding area of leg 2, 10, 11 and 12 replaced by 1-3 setae (Fig. 4I ).

Styli present at base of legs 3-12, subconical (length 5 μm, width 3 μm), basal part with straight hairs; distal quarter hairless and with blunt apex (3 μm) (Fig. 4I ).

Sense calicles with smooth margin around pit. Sensory seta inserted in cup center, extremely long (115-120 μm).

Cerci about half length of head, 3.3-3.8 times as long as its greatest width (108-115 μm, 30-34 μm), sparsely covered with 33-39 subequal setae (Fig. 5F, G ). Two types of setae inserted on cercus: 4 or 5 long and erect setae located in outer side, and others slightly curved and depressed. Longest outer seta (20 μm) 0.6-0.7 of greatest width of cerci, terminal area short (16-18 μm), circled by 6-8 layers of curved ridges. Terminal setae (15-16 μm) slightly shorter than terminal area (Fig. 5F, G ).

Etymology.

The species name is derived from the Latin words " longus " and " spina " meaning "long spine". It is feminine and refers to the extremely long proximal spines on the pars molaris of the mandible.

Distribution.

Known only from the type locality.

Remarks.

Symphylella longispina sp. nov. has a thickened and prominent labrum and irregular bladder-shaped organs on antennae, which separate it from all other congeners. It is most similar to S. asiatica Scheller, 1971 from India and Sri Lanka in the shape and chaetotaxy of the tergites, but the new species differs in the distal part of the processes (distinctly swollen in S. longispina sp. nov. vs small and slender in S. asiatica ), in the shape and chaetotaxy of cerci (subcylindrical and with sparse setae in S. longispina sp. nov. vs conical and with dense setae in S. asiatica ), and in the shape of the palp of the first maxilla (slightly curved in S. longispina sp. nov. vs straight in S. asiatica ). The new species is also similar to S. brincki Scheller, 1971 from Sri Lanka in the chaetotaxy of the tergites, but they can be easily separated by the central rod (with a middle node-like interruption in S. longispina sp. nov. vs with a narrow transverse interruption in S. brincki ), by the end of the processes (with round end-swellings in S. longispina sp. nov. vs spatulate end-swellings in S. brincki ), and by the shape and chaetotaxy of cerci (3.3-3.8 times as long as wide and with sparse setae in S. longispina sp. nov. vs 2.3 times as long as wide and with dense setae in S. brincki ).

Figures

Figure 4. Symphylella longispina sp. nov. A habitus, dorsal view B head, dorsal view C labrum and mandible D tergites 1 - 3 E Toemoesvary organ and antennomeres 1 - 4 F tergite 2, right side (als - anterolateral seta, lms - lateromarginl setae, as - apical seta, is - inserted seta, ibs - inner basal seta) G tergites 4 - 5 H first pair of legs (arrows indicate the reduced legs) I styli and coxal sacs on base of leg 12 (arrows indicate styli). Scale bars: 100 μm (A); 20 μm (B-I).

Figure 5. Symphylella longispina sp. nov. A mandible, lateral view (pi - pars incisivus, pm - pars molaris, lm - lacinia mobilis) B first maxilla C left 1 - 3 antennomeres, dorsal view D terminal three antennomeres, dorsal view (bo - bladder-shaped organ, co - cavity-shaped organ, rso - rudimentary spined sensory organ, so - spined sensory organ) E terminal three antennomeres, ventral view F left cercus, dorsal view (arrows indicate long and erect outer setae) G left cercus, ventral view H frons (L 1 - L 5 - lateral setae, a 0 - antero-central seta, arrows indicate macrosetae) I leg 12, dorso-lateral view. Scale bars: 20 μm.