Tetracanthella dorsoduplex

Xie, Zhijing, Potapov, Mikhail & Sun, Xin, 2019, Two new species of the genus Tetracanthella (Collembola; Isotomidae) from China, Zootaxa 4585 (3), pp. 573-580: 574-576

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Tetracanthella dorsoduplex

sp. nov.

Tetracanthella dorsoduplex  sp. nov.

Figs 1View FIGURES 1–2, 3–10View FIGURES 3–7View FIGURES 8–11, 21View FIGURES 21–23

Type material. Holotype: subadult female, E China. Zhejiang province. Lin’an city. Near Gongchen Mts. , 220 m alt., N 30°13.779', E 119°43.716'. Mosses on large rock among agricultural lands, northern exposition, 10.IV.2008, leg. M.Potapov, 15 paratypes: from the same placeGoogleMaps  . Holotype and 6 paratypes are deposited in the Shanghai Entomological Museum, CAS (Shanghai, China), 9 paratypes––in Moscow State Pedagogical University (Moscow, Russia)  .

Description. Body length from 1.2 mm (adult male) to 1.5 mm (the largest subadult female). Body cylindrical ( Fig. 1View FIGURES 1–2). Coloration bluish, not very dark, antennae with or without pigment. Polygons of cuticular reticulation well developed. The biggest polygons located at posterior edge of head and on Abd. IV and V ( Fig. 21View FIGURES 21–23), often elongated and much larger than mesochaeta socket. Canals between polygons well marked. No smooth fields. Dorsal mesochaetae long, not shortened in axial part of tergites, in posterior row of Abd. IV equal to other parts of body (Md: p1 = 1.5–1.9). Abd. IV with p3 longer than p1 (1.2–1.6) ( Fig. 8View FIGURES 8–11). Macrochaetae not very long, acuminate or slightly blunt apically.

8+8 ocelli, G and H reduced (dA: dH = 1.6–2.0). PAO 2.0–2.5 times longer than ocellus A. Chaeta s’ of Ant. III in males absent. 4 prelabral chaetae. Outer maxillary lobe with 4 sublobal hairs and simple maxillary palp. Labium with complete set of guards [A(1)B(4)C(0)D(4)E(7)], 3 proximal and 4 basomedian chaetae. 4+4 postlabial chaetae. 5–6 pp-chaetae between medial line and p3 on head. Frontal chaeta ap present.

Body chaetotaxy rather abundant ( Fig. 4View FIGURES 3–7). Axial chaetotaxy 12–14,10/8(6),8(6),8,6(8), often asymmetric. Macrochaetotaxy: 1,1/1,1,2 (see Remarks) ( Figs 3, 4View FIGURES 3–7). Corner mesochaetae on Th. II and III not stronger than other mesochaetae of p-row. Number of s-chaetae: 3,3/2,2,2,2,4 (s), 1,1/1,1,1 (ms) ( Fig. 3View FIGURES 3–7). S-chaetae of medium size, medial ones on Abd. III arranged lateral to Mdl macrochaetae. Lateral s-chaetae on Abd. IV between p3 chaetae and Mp macrochaetae ( Figs 3View FIGURES 3–7, 8View FIGURES 8–11). Sternite of Th. III without chaetae.

Coxa I without an external chaeta. Tibiotarsi with 1,2,2 long and slightly clavate dorsal tenent hairs and 1,1,0 enlarged ventral tenent hairs. In fully adult males (ejaculatory duct well visible) chaeta B5 and X on tibiotarsi III thickened and considerably expanded in proximal half ( Fig. 9View FIGURES 8–11). Tibiotarsi I and II with 21 chaetae each, III with 25 chaetae ( Fig. 10View FIGURES 8–11). Claw without teeth. Empodial appendage about half of inner edge of claw in length (0.5–0.6).

Ventral tube with 3+3 lateral and 4 posterior chaetae. Retinaculum with 4+4 teeth and 1 chaeta. Anterior furcal subcoxa with 8–9 chaetae, posterior one with 6–7 chaetae. Manubrium with 14–16+14–16 dorsal chaetae, including 3+3 basal. With a pair of chaetae on lateral sides (sometimes absent on one side) ( Fig. 7View FIGURES 3–7). Mucro bidentate. Dens with 1 anterior and 7 posterior chaetae, with clear humps on posterior side ( Figs 5, 6View FIGURES 3–7). Dens: claw III = 2.9–3.3. Manubrium: dens: mucro = 8–11: 6–8: 1.

Anal spines parallel, large, on normal papillae. Medial mesochaetae (a1) of Abd. V slightly anterior to medial macrochaetae (a2) ( Fig. 8View FIGURES 8–11). Arrangement of chaetae and spines on dorsum of Abd. V as a2-a2: a1-a1 = ~2.3; a2-a2/ a2-ASe = ~1.9. Males present.

Remarks. The new species belongs to ' sylvatica ' group and differs from all species of the genus by complete absence of both Md and Mdl macrochaetae on Th. II–III and Abd. I–II (formula 1,1/1,1,...). The specific position of lateral s-chaetae on Abd. IV ( Fig. 8View FIGURES 8–11) is especially remarkable in T. dorsoduplex  sp. nov. It seems likely that these schaetae are positioned posterior to Ml and lateral to Mp in all other species of Tetracanthella, this pattern can be inferred from the descriptions in which this character is pictured, e. g., after the illustrations of the monograph of Deharveng (1987). In T. dorsoduplex  sp. nov. lateral s-chaetae are placed between p3 chaetae and Mp macrochaetae and so both medial and lateral s-chaetae are set on dorsal side of tergite. In other characters (mouth parts, furca, cuticle reticulation, tibiotarsi) the new species is closely related to T. sylvatica Yosii, 1939. After redescription of the species by Deharveng (1987) and our observations of specimens from Japan (Honshu, Kyoto, leg. S. Fujii), T. sylvatica has Md and Mdl macrochaetae on Th. II, III and Abd. I, II, respectively (formula 2,2/ 2,2,...) and normal position of lateral s-chaetae on Abd. IV ( Fig. 11View FIGURES 8–11).

Distribution. T. dorsoduplex  sp. nov. is known only from type locality which is the most southern record for the genus in Asia.

Derivatio nominis. The species is characterized with doublet (duplex) of dorsal s-chaetae on each side of Abd. IV.


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