Tetracanthella orientalis Martynova, 1977 in Martynova et al. 1977

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 : 47-50

Tetracanthella orientalis Martynova, 1977 in Martynova et al. 1977 Figs 40, 47-50, 57, 58

Material.

Magadanskaya region: vicinities of Magadan, Snow Valley, 18.09.1974. It is the type locality of the species although the type specimens were not seen by us and are probably lost.

Chukotski AO: Anadyrski district, vicinities of Anadyr, Observatsii Cape, tundra, 27.06.1974, leg. E. Bondarenko, Anadyrski district, Ugolnaya Bay, tundra, leg. M. Chernyakhovski.

Kamchatka: Yuzhno-Kamchatski Reserve, Elizovski district (south), Kambalnoye Lake, pine elfin wood, 14.09.2005, leg. L. Lobkova; Elizovski district (north), Kronotski reserve, caldera of Uzon, moss-lichen tundra, 20.08.2005, leg. L. Lobkova; Kronotski reserve, Vachkazhets Volcano, 1000 ma lt., tundra, gopher burrow, leg. L. Lobkova; Bystrinski district, vicinities of Anavgai and Esso, 3-5.07.2012, tundra at lake (Ledum, Empetrum ), leg. M.P.

Description.

Body length 1.2-1.6 mm. Body slender, continuously narrowing (Fig. 40). Coloration dark, including antennae. Polygons large, canals between polygons well marked. Smooth fields usually present on all tergites of body (Fig. 49, 50). Posterior edge of head with smooth fields in lateral position (Fig. 50) or two groups of larger polygons (Fig. 57) in associated places. Area between ASi often with small smooth field. Dorsal mesochaetae short, slightly shortened in axial part of tergites (Fig. 49), in posterior row of Abd. IV not longer than on other parts of body (Md:p1 = 3.7-5.7). Abd. IV with p3 much longer than p1 (p3: p1 = 2.3-4.4). Macrochaetae long.

8+8 ocelli, G and H reduced (dA: dH = ~1.5). PAO 2.5-4.0 as long as the diameter of ocellus A. Chaeta s’ of ant.III in males present. Two prelabral chaetae. Outer maxillary lobe with three sublobal hairs and simple maxillary palp. Labium with three proximal and four basomedian chaetae, labial palp with reduced set of guards [A(1) B (3)C(0)D(3)E(4)] (as in Fig. 2). Postlabial chaetae 3+3. With 4-5 chaetae between medial line and pc3 on head. Frontal chaeta ap absent.

Chaetotaxy scarce (Figs 49, 50). Axial chaetotaxy 12-10,8/4,4,4,4. Macrochaetotaxy: 3(W),3(W)/2,2,3. Mdl macrochaetae in p-row on Th. II and III, sometimes weakly developed. Number of s-chaetae: 3,3/2,2,2,2,4 (s), 1,0/1,0,0 (ms) (Fig. 47). S- chaetae short, medial ones on Abd. I–III arranged behind Mdl macrochaetae. Sternite of Th. III without chaeta.

Legs as in T. tardoki sp. nov. Tibiotarsi I, II, III with 21, 21, 22 chaetae. Claw without teeth. Empodial appendage short, 0.2-0.3 as long as inner edge of claw. Ventral tube with 3+3 lateral and four posterior chaetae.

Retinaculum and furca absent. Retinacular field with 3-5 chaetae. Anterior furcal subcoxa with three (rarely four) chaetae, posterior one with four chaetae. Manubrial field with eight (rarely seven) chaetae (Fig. 48). Anal spines parallel, large, on high papillae. Papillae of inner pair sclerotised. Medial mesochaetae (a1) of Abd. V anterior to medial macrochaetae (a2) (Fig. 49). Arrangement of chaetae and spines on dorsum of Abd V as a2-a2/a1-a1 = 1.7-1.8; a2-a2/a2-eAS = 1.3-1.7. Males present.

Distribution.

Tetracanthella orientalis is widely distributed in northern part of the Far East of Russia (Fig. 58). In Magadanskaya region and Kamchatka it is the only known species of the genus. In Chukotka, T. orientalis can be recorded together with T. sibirica which has the similar appearance but belongs to another group of species.

Discussion.

See the remarks to T. tardoki sp. nov.