A new species of the genus Stygothrombium, representing a newly recorded superfamily Stygothrombioidea Mullen & Vercammen-Grandjean, 1980 (Acari: Stygothrombiae) from China Author Li, Haitao Author Jin, Daochao Author Guo, Jianjun text Zoological Systematics 2021 46 4 281 288 http://zoobank.org/e29e0326-f45f-4749-b930-0dd9062fccbc journal article 10.11865/zs.2021402 322fcc8b-1bb1-4dbe-9607-d803273e26eb 2095-6827 7175787 E29E0326-F45F-4749-B930-0DD9062FCCBC Stygothrombium garzensis Li & Guo , sp. nov. ( Figs 1–5 ) Habitat. Interstitial waters. Material examined. Holotype female, Chaqingsongduo National Nature Reserve , Sichuan , China (31°00′88′′N, 99°24′71′′E, elev. 3523 m ), water depth 30–40 cm , located at the hillside, running water with organic detritus, dead wood and leaves on the bottom, collected by Boyan Li , 30.VIII.2020 , Slides No. SC-ST-2020080101. Etymology. “ garze -” is derived from the name of the Garze Tibetan Autonomous Prefecture, Sichuan Province , China , where the specimen was collected. Diagnosis. Soft and papillate idiosoma vermiform; eyes completely absent; infracapitulum base approximately 3.5 times as long as rostrum; P-A with two stout subventrodistal harpagones, above harpago seta thicker than other one; on one side of P-B, tibia with one four-pronged odontus claws bulging above tarsus; se about half length of posterior portion of prodorsal plate; one seta and two rather long setae at lateral margin of Cx-I; stalked Ac-1–3 arranging in an almost straight line, glv- 2 between Ac-3 and inner posterior angle of Cx-IV, located at one-third of interval near Ac-3 approximately; empodium considerably smaller than lateral claws. Figure 1. Stygothrombium garzensis Li & Guo , sp. nov. , ♀, holotype (SC-ST-20200801). A. Ventral view. B. Gll -1. C. Gll -2. D. I-L-4, stomatoid lyrifissures. Scale bars: A = 500 μm; B–D = 10 μm. Description. Female (SC-ST-2020080101). Soft and papillate idiosoma vermiform ( Fig. 1A ); eyes completely absent ( Fig. 2A ); with eight pairs of gld and seven pairs of gll ( gld- 1–8, gll- 1–7 in Fig. 2A ), six pairs of glv ( glv- 1–6 in Fig. 2B ); idiosomal glandularia (or modified stomatoid lyrifissures) without sclerite platelets but surrounded by unpapillate cuticle, a long seta and short seta associated with glandularia except gll -1 with only a short seta ( Figs 1B–C ); excretory pore placed near posterior end of ventral surface and between glv -5 ( Fig. 2B ). Gnathosoma retractable into idiosoma; infracapitulum base approximately 3.5 times as long as rostrum; two pairs of setae on rostrum, posterior one longer than anterior one ( Fig. 3A ); chelicera two-segmented, basal segment expanded and long ( Fig. 3B ); fused pedipalp two-segmented: first segment including trochanter + femur + genu (P-A); P-A with numerous dorsal setae, a thin ventrodistal seta, two stout subventrodistal harpagones (above harpago seta thicker than other one) and two ventroproximal setae (one normal seta and one long curved seta); tibia + tarsus fused into short second segment (P-B); on one side of P-B, tibia with one four-pronged odontus claws bulging above tarsus, one stout gladius seta, one thick and short lancea seta, one parodontus, and two normal setae on tarsus; P-B with six normal setae on another side, single solenidion on dorsum and alantoid seta with rounded tip at terminus ( Figs 3C–D ). Figure 2. Stygothrombium garzensis Li & Guo , sp. nov. , ♀, holotype (SC-ST-20200801). A. Dorsal view. B. Ventral view. Scale bars = 500 μm. Prodorsal plate bearing vi , si , ve and se ; long and narrow posterior portion of prodorsal plate approximately six times as long as short and wide anterior portion; se about half length of posterior portion, longer than vi , si and ve ( Fig. 3E ). Coxal plates in four groups; two ACG not fused but close, two PCG widely separated; Cx-I trapezoidal, with numerous setae near inner apical angles and three setae (one seta and two rather long setae) at lateral margin; Cx-II trapezoidal, with one seta near outer posterior angles ( Fig. 4A ); Cx-III and Cx-IV nearly triangular, with some setae respectively ( Fig. 4B ). Genital field with about twenty tiny setae; stalked Ac-1–3 arranging in an almost straight line, interval from Ac-1 to Ac-2 and Ac-2 to Ac-3 almost equal; gonopore surrounded by three or four setae on each side; glv- 2 between Ac-3 and inner posterior angle of Cx-IV, located at one-third of interval near Ac-3 approximately ( Fig. 4B ). Figure 3. Stygothrombium garzensis Li & Guo , sp. nov. , ♀, holotype (SC-ST-20200801). A. Infracapitulum, dorsal view. B. Chelicera. C. Pedipalp, one lateral view. D. Pedipalp, another lateral view. E. Prodorsal plate. Scale bar= 200 μm. Legs without swimming setae but numerous setae present; I-L thicker than other pairs of legs, I-L-3–5 with stomatoid lyrifissures on one side ( Figs 5A–D ); tarsus of I–IV-L with two pectinate lateral claws and one smooth middle empodium, empodium considerably smaller than lateral claws ( Fig. 1D ). Male. Unknown. Measurements ( holotype ). Idiosoma L 3857 (from peak of protrusible integument to bottom), W 1114; excretory pore L 108; Infracapitulum L 783, base L 607, rostrum 176; Chelicera base segment L 477, claw L 102; P-A dL 253, P-B dL 97, alantoid seta L 60, above harpago seta L 64, nether harpago seta L 66; prodorsal plate L 478, anterior portion L 73, posterior portion L 405; ACG L 274; PCG L 346; gonopore L 119, Ac-1 L 76, Ac-2 L 66, Ac-3 L 80; Legs segments dL: Ⅰ-L-1 100, Ⅰ- L-2 164, Ⅰ-L-3 173, Ⅰ-L-4 182, Ⅰ-L-5 189, Ⅰ-L-6 159, claw dL 88; II-L-1 88, II-L-2 134, II-L-3 136, II-L-4 166, II-L-5 190, II-L-6 140, claw dL 84; III-L-1 123, III-L-2 134, III-L-3 139, III-L-4 186, III-L-5 205, III-L-6 153, claw dL 78; IV-L-1 101, IV-L-2 173, IV-L-3 213, IV-L-4 259, IV-L-5 280, IV-L-6 191, claw dL 81. Remarks. The present new species is similar to S. monotrichum Nagasawa & Abé, 2014 from Japan in quantity and location of idiosomal glandularia and pedipalp structures. The new species differs from the latter in the following aspects: (1) idiosoma L 3857 in S. garzensis Li & Guo , sp. nov. , but 1560–1830 in S. monotrichum ; (2) glv -1 between ACG and PCG in S. garzensis Li & Guo , sp. nov. , while absent in S. monotrichum ; (3) glv- 2 between Ac-3 and inner posterior angle of CxIV in S. garzensis Li & Guo , sp. nov. , but located posteromedially to the posterior acetabula in S. monotrichum ; (4) setae on ACG and pedipalp much more multiple than S. monotrichum ; (5) P-A dL 253 in S. garzensis Li & Guo , sp. nov. , while P-A dL 88 in S. monotrichum . (Nagasawa & Abé 2014) Figure 4. Stygothrombium garzensis Li & Guo , sp. nov. , ♀, holotype (SC-ST-20200801). A. Anterior coxal group (Cx-I+Cx-II). B. Posterior coxal group (Cx-III+Cx-IV), genital field. Scale bar =200 μm. Figure 5. Stygothrombium garzensis Li & Guo , sp. nov. , ♀, holotype (SC-ST-20200801). A. I-L-1–6. B. II-L-1–6. C. III-L-1–6. D. IV-L-1–6. Scale bar= 200 μm. Funding This research was supported by National Natural Science Foundation of China (31772421, 31750002), Guizhou Science and Technology Project (Qiankehe Pingtai Rencai [2017] 5788) and National Key R & D Program of China (2017YFD0201000). Acknowledgements We are grateful to Boyan Li ( Institute of Entomology , Guizhou University, P. R . China ) for collecting the specimen and processing the photos. Furthermore, we are thankful to Zhuhui Ding ( Institute of Entomology , Guizhou University, P. R . China ) for helping to take photos of specimen .