Tetracanthella annulata, Potapov, Mikhail, Brinev, Alexey & Sun, Xin, 2019

Potapov, Mikhail, Brinev, Alexey & Sun, Xin, 2019, Isotomidae of Japan and Asiatic part of Russia. II. The genus Tetracanthella of the Far East, ZooKeys 855, pp. 31-54: 35-38

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Tetracanthella annulata

sp. nov.

Tetracanthella annulata  sp. nov. Figs 6, 8-13, 14-20, 51, 58

Type material.

Holotype: subadult female, Russia, Far East, Primorye, Terneyski District, Sikhote-Alinski Reserve, Kabani station, 900 m alt., 45.14122°N, 135.87759°E, coniferous forest with Rhododendron fauriei  , rotten wood, 8.08.2017, leg. N.K., A.G., A.K. Three paratypes: nearly the same place, 932 m alt., 45.13840°N, 135.88702°E, leg. N.K., A.G., A.K.; seven paratypes: Sikhote-Alinski Reserve, Blagodatny station, 95 m alt., 44.96670°N, 136.53410°E, oak forest, rotten wood, 7.08.2017, leg. N.K., A.G., A.K.

Other material

(all from the Far East of Russia): Primorski Krai: Shkotovski district, Livadiysky Range, Pidan Mt., rotten wood, ~800 m alt., 20.09.2004, leg. M.Potapov; ibidem, trail to Falaza Mt., ~600 m alt., mosses on rotten wood, 08.09.2018, leg. M.P., A.K.; Primorski Krai, Khasanski district, "Kedrovaya Pad " Reserve, valley of Kedrovaya River, cedar litter of mixed forest, 29.09.2004, leg. M.P.; ibidem, 5 km of trail to Central shelter, valley mixed forest, rotten wood, 29.07.2016, leg. N.K., M.P.; ibidem, right bank of Kedrovaya River, 2nd Zolotisti Spring, coniferous litter, 14.07.2013, leg. S. Spiridonov; Primorski Krai, Lazovsky district, in mountains nearby Preobrazheniye, Sredni stream (tributary of Maralovaya (valley of Sokolovka River), mixed forest, rotten wood, 21.09.2011, leg. M.P.; Primorski Krai, Terneyski district, Ostraya Mt., litter, 02.06-04.06.2018, leg. A.K.; Sikhote-Alinski Reserve, Kabani station, 900 m alt., 45.14122°N, 135.87759°E, coniferous wood with Rhododendron fauriei  , rotten wood, 8.08.2017, leg. N.K., A.G., A.K.; ibidem, 932 m alt., 45.13840°N, 135.88702°E; Sikhote-Alinski Reserve, Blagodatny station, oak wood, rotten wood, 7.08.2017. 95m alt., 44.96670°N, 136.53410°E; leg. N.K., A.G., A.K. Primorski Krai, Partyzanski district, Olkhovaya Mt., 540 m alt., 43.3058°N, 133.6679°E, rotten wood in mixed forest, 20.08.2018, leg. M.P., A.K.

Khabarovski Krai, Nanaiski District, Anyuiski National Park, Tormasu River, mixed forest, rotten wood, 204 m alt., 49.30332°N, 137.57004°E, 07.08.2018, leg. N.K., A.G., A.K.; ibidem, Anyuiski National Park, Anyui River, mixed forest, rotten wood, 205 m alt., 49.36350°N, 137.70227°E; Komsomolsk-Khabarovsk road, 270 km, cedarn-large-leaved valley forest, litter, 42 m alt., 048.93659°N, 136.33167°E, leg. N.K., A.G., A.K.; Khabarovski Krai, Komsomolski District, Komsomolski Reserve, foothills of Sergol Mt., aspen-oak forest, rotten wood, 259 m alt., 50.73823°N, 137.40182°E, 11.08.2018, leg. N.K., A.G., A.K.; ibidem, Komsomolski Reserve, Sergol Mt., mixed forest with cedar, rotten wood, 228 m alt., 50.73710°N, 137.39772°E, 11.08.2018, leg. N.K., A.G., A.K.; Komsomolski District, Komsomolsk–Khabarovsk road, 85 km, 1,5 km from Gorely Klyuch Stream, mixed forest, rotten wood, 50.21810°N, 137.33202°E, 12.08.2018, leg. N.K., A.G., A.K.

Amurskaya Region, Arkharinski district, Khinganski Reserve, 10 km E Uril, coniferous forest, litter, 07.10.2009, leg M.Babykina.


Coloration spotty, from dark to light grey. Coxa I without an external chaeta. Macrochaetotaxy: 2,2/2,2,2. Dens long, with clear crenulations, without anterior and normally with seven posterior chaetae.


Body length 0.9-1.5 mm. Body cylindrical, not narrowing (Fig. 6). Coloration spotty, from dark to light grey, ventral side of corpus paler, often not pigmented. Pigmentation of antennae vary, paler than other parts of the body, sometimes colorless. Largest polygons much larger than mesochaeta sockets, canals between polygons broad, clearly marked (Fig. 51). No smooth fields. Dorsal mesochaetae long, not shortened in axial part of tergites, in posterior row of Abd. IV not longer than on other parts of body (Md : p1 = 1.8-2.5). Abd. IV with p3 longer than p1 (p3 : p1 = 1.2-1.8) (Fig. 10). Macrochaetae usually blunt and plain at tip.

8+8 ocelli, G and H reduced (dA : dH = 1.5-2.0). PAO 1.9-2.7 times as long as the diameter of ocellus A (Fig. 16). Chaeta s’ of Ant.III in males absent. Four prelabral chaetae. Outer maxillary lobe with four sublobal hairs and simple maxillary palp. Labium with with complete set of guards [A(1)B(4)C(0)D(4)E(7)], three proximal and four basomedian chaetae. Postlabial chaetae 4+4 (Fig. 11). Five chaetae between medial line and pc3 on head. Frontal chaeta ap present.

Axial chaetotaxy: 12-14,10/6,6,6,6 (without chaetae in Md-position on Abd. I–III and p1' chaetae on Abd.IV) (Figs 9, 10). Macrochaetotaxy: 2,2/2,2,2. Md macrochae tae on Th.II and III and Mdl macrochaetae on Abd.I and II short (Figs 8, 14, 15). 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. 8). S-chaetae of medium size, medial ones on Abd. I–III arranged lateral to Mdl macrochaetae. Sternite of Th. III without chaeta.

Coxa I without an external chaeta. Tibiotarsi with 1,2,2 clavate dorsal tenent hairs (Fig. 13) and 1,1,0 ventral pointed long hairs. Males with chaeta B5 and X on tibiotarsi III expanded, spatula-like (Fig. 12), these chaetae thin in females. Tibiotarsi I, II, III with 21, 21, 25 chaetae. Claw untoothed, empodial appendage long, 0.6-0.8 as long as inner edge of claw, with long apical filament (Fig. 13). Ventral tube with 3+3 latero-distal and four posterior chaetae.

Retinaculum with a chaeta and 4+4 teeth, basal tooth smaller. Anterior furcal subcoxa with 8-9 (rarely seven or ten) chaetae, posterior one with 5-6 (rarely four or seven) chaetae. Dorsal side of manubrium with 3+3 laterobasal chaetae and 11+11 (sometimes ten or 12 on one side) chaetae on main part (14+14 at whole), besides with a chaeta on each lateral side (Fig. 20). Mucro bidentate, small. Dens long, always with clear crenulations, without anterior and with 6-8 (normally 7, rarely 9) posterior chaetae (Figs 17-19). Dens : claw III = 3.5-4.3. Manubrium : dens : mucro = 8-12 : 8-12 : 1.

Anal spines parallel, large, on moderate papillae. Medial mesochaetae (a1) of Abd. V slightly in front of medial macrochaetae (a2). Arrangement of chaetae and spines on dorsum of Abd V as a2-a2/a1-a1 =2.1-2.3; a2-a2/a2-eAS = 1.7-1.8 (Fig. 10). Males present.


The species is characterized by annulated posterior side of dens.

Distribution and ecology.

The species is widely distributed in southern areas of the Far East of Russia (Primorsky Krai, Khabarovsky Krai and Amurskaya District), both in flatland and in the mountains (Fig. 58). It prefers rotten wood although occurs in forest litter.


The new species belongs to ' sylvatica  ' group and differs from all species of the group by absence of chaetae on anterior side of dens. The disproportion of anterior and posterior number of chaetae on dens (0 vs. ~7), clear humps on posterior side of dens and grey coloration make T. annulata  sp. nov. unmistakable in the area of its distribution.