Tetracanthella dorsoduplex, Xie & Potapov & Sun, 2019

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

Tetracanthella dorsoduplex sp. nov.

Figs 1 , 3–10 , 21

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 place . 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. 1 ). 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. 21 ), 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. 8 ). 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. 4 ). Axial chaetotaxy 12–14,10/8(6),8(6),8,6(8), often asymmetric. Macrochaetotaxy: 1,1/1,1,2 (see Remarks) ( Figs 3, 4 ). 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. 3 ). 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 3 , 8 ). 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. 9 ). Tibiotarsi I and II with 21 chaetae each, III with 25 chaetae ( Fig. 10 ). 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. 7 ). Mucro bidentate. Dens with 1 anterior and 7 posterior chaetae, with clear humps on posterior side ( Figs 5, 6 ). 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. 8 ). 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. 8 ) 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. 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.

Figures

FIGURES 1–2. Appearance and macrochaetotaxy of Tetracanthella dorsoduplex sp. nov. (1), and T. wui sp. nov. (2)

FIGURES 3–7. T. dorsoduplex sp. nov.: 3, position of macrochaetae, s-chaetae and ms-chaetae on thorax and abdomen; 4, dorsal chaetotaxy of Th. II–Abd. III, lateral view; 5–6, dens, lateral (5) and posterior (6) views; 7, furca, posterior view.

FIGURES 8–11. T. dorsoduplex sp. nov. (8–10) and T. sylvatica (11): dorsal chaetotaxy of Abd. IV–VI (8) and Abd. IV (11); 9, spur of leg III in adult male; 10, distal part of leg III in female.

FIGURES 21–23. Reticulation of cuticle in Tetracanthella (21–22) and appearance of young individual of T. wui sp. nov. (23): 21, T. dorsoduplex sp. nov., Abd. V, area near external anal spines; 22, T. wui sp. nov., posterior edge of Abd. IV, axial part. p1, p1'––chaetae of p-row, ASp-e––external anal spines.