Folsomia imparis Potapov & Hasegawa

Potapov, Mikhail, Hasegawa, Motohiro, Kuznetsova, Natalia, Babenko, Anatoly & Kuprin, Alexander, 2018, Isotomidae of Japan and the Asiatic part of Russia. I. Folsomia ' inoculata' group, ZooKeys 750, pp. 1-40 : 11-15

Folsomia imparis Potapov & Hasegawa sp. n. Figs 32, 40-46, 90

Type material.

Holotype, female, Japan, Hokkaido Island, Shiretoko Peninsula, trail to Mont. Rausu, deciduous forest ( Acer , Quercus , Sorbus , Magnolia , Daphniphillum macropodium ), litter, 19.viii.2016, 354 m alt., 44.1083°N, 145.0893°E, coll. M. Potapov and N. Kuznetsova. Paratypes, 12 specimens from the same location; three specimens from Russia, Far East, S Primorye, Ussuriysky Reserve, Komarovskoye Forest District, Turova Nipple, Khripunovsky Pass, mixed forest with Pinus koraiensis on slope, rotten wood, 22.vii.2016, coll. M. Potapov and N. Kuznetsova; four specimens from same region, but Shkotovsky District, trail to Mont. Khualaza, deciduous forest, rotten wood and litter, 21.vii.2016, coll. M. Potapov and N. Kuznetsova. The material from Japan and Russia is deposited in TPM and MSPU, respectively.

Other material.

Far East of Russia, Primorsky Krai, Bikin River near confluence to Amba River, mixed forest litter, 29.ix.2009, coll. O. Smirnova; Ussuriyski District, Ussuriyski Reserve, decaying wood, 5.x.2004, coll. M. Potapov, L. Deharveng, R. Pomorski, and A. Bedos; Shkotovsky District, trail to Khualaza Mount, rotten wood, 21.vii.2016, coll. M. Potapov and N. Kuznetsova; Partizansky District, vicinities of Ekaterinovka, Chondalaz (= Lazovy) Range, oak litter, 26.ix.2004, coll. M. Potapov, L. Deharveng, R. Pomorski, and A. Bedos; Khasansky District, vicinities of Barabash, oak litter, 200-400 m alt., 27.ix.2004, coll. M. Potapov; Sakhalin, Kholmsky District, South Kamysh Ridge, Spamberg Mt., moss in mixed and coniferous forests, 14-15.vi.2017, coll. A. Kuprin; Korsakovsky District, vicinities of Korsakov, forest litter, 16.vi.2017, coll. A. Kuprin; Khabarovsky Krai, suburbs of Khabarovsk, Voronez highlands, leaf litter near river bank. 26.iv.2010, coll. M.Potapov; Verkhnebureinsky District, western part of Badjal Range, upper flow of Irungda River (tributory of Amgun’ River), 1900 m alt., subalpine litter and moss, 23.vi.2014, coll. A. Brinev.

North Korea. Hamgyong-namdo Province (= South Hamgyong), SW from Tanchon, 30.v.1987, coll. A. Szeptycki; Yanggang-do Province, Rimjong-su Waterfall, litter, 7.vii.1985, coll. A. Szeptycki.

Material of F. sp. aff. imparis . Khabarovsky Krai (western part), Bureyskoye Reservoir, Nizny Mel’gin Bay, 50.5539°N, 131.3970°E, 12.ix.2009, coll. M. Babykina; Amurskaya Region, ~3 km N Zeya, oak litter, 22.viii.2014, coll. M. Potapov and N. Kuznetsova.

Diagnosis.

Blind. Dorsal macrosetae (Md) present on both Th.II and Th.III. Sensillary formula complete (43/22235; 10/100). Medial s-setae on body tergites long, set in p-row. Ventral setae on Th.III present. Manubrium on anterior side with 3 –5+3– 5 paired and 2-3 unpaired axial setae, dens with 23-27 anterior setae. Mucro bidentate.

Description.

Body size from 0.9 to 1.4 mm. Body without pigmentation, its shape as in F. amurica sp. n. Cuticle with fine hexagonal primary granulation ( “smooth”). Ocelli absent. PAO slender, constricted, 1.4-1.7 as long as width of Ant.I and 1.7-1.9 as long as inner unguis length. Labium with five usual papillae ( A–E), guard setae e7 absent, three proximal and four basomedian setae. Ventral side of a head with 4+4 postlabial setae. Ant.I with 15-17 common setae, two ventral s-setae (s) and three bms, one long (inseparable from common setae) and two short, Ant.II with three bms and one latero-distal s, Ant.III with one bms and with five distal s (including one lateral), without additional s-setae (Fig. 46). Several tubular s-setae on Ant.IV. Organite stick-like, small.

Common setae long and sparse. Sensillary formula as 43/22235 (s), 10/100 (ms). Tergal s-setae thin and long. Medial s-setae on Th. II–Abd.III situated in posterior position, on Abd. I–III between Md and Mdl. Abd.V with five s-setae arranged as four ones (as, accp1, accp2, accp3), long and slender, and one latero-ventral, short ( ‘4+1’ pattern) (Figs 32, 40), accp3 s-setae almost as long as accp2 (accp2: accp3 = 1.0-1.2). p1-setae on Abd.V short (see also the Discussion and Table 2). Macrosetae smooth and long, 2,2/3,3,3 in number, medial ones on Abd.V 1.5-2.0 times shorter than dens and 4.8-7.7 times longer than mucro. Metathorax with 3+3 (rarely, 4+3) ventral setae, as in F. amurica sp. n.

Unguis of normal shape, without lateral and inner teeth. Empodial appendage as long as 0.4-0.5 unguis. Tibiotarsi with 26-28 setae on legs I–II and 33-37 on leg III. Upper and lower subcoxae of legs I–III with 0,1/3,~7/5 –6,7– 8 setae, respectively. Coxae of leg I with three front setae. Tibiotarsal tenent setae pointed, some setae on distal half of tibiotarsi thickened. Ventral tube with 4+4 latero-distal and seven posterior setae (four in distal transversal row and three in more proximal position), anteriorly without setae. Tenaculum with 4+4 teeth and a seta. Anterior furcal subcoxae with 10-12, posterior one with five setae. Anterior side of manubrium with 3 –5+3– 5 pair setae, and 2-3 (rarely one) axial unpaired setae (Figs 43-45). Posterior side of manubrium with 4+4 latero-basal, two apical setae (ap), 3+3 setae in distal transversal row (M1, ml1, L1), two pairs of lateral setae, and 3 –4+3– 4 in central part (Fig. 41). Dens with 23-27 anterior setae (Figs 41, 42). Posterior side of dens crenulated and with six normal setae (four basal and two at the middle) and one rudimentary seta at the base of mucro. Mucro bidentate. Ratio of manubrium: dens: mucro = 5.2-6.6: 9.4-11.7: 1. Males present.

Remarks.

Folsomia imparis sp. n. is well defined by the presence of unpaired setae on anterior side of manubrium shared only with F. hidakana (belongs to another subgroup) and F. setifrontalis (has anterior setae on ventral tube). Main differences from the other species of the subgroup ' macrochaetosa ' are shown in Table 2.

A typical form, called preliminary as f. 1 (Fig. 32) has short p1-setae on Abd.I. In Japan and Primorsky Krai we often recorded specimens with long p1, as long as a1 (f. 2 in Table 2) which was not mixed with f. 1 by samples even if reported in the same areas.

Additionally, a closely related form was also recorded in two more eastern localities (see the Material part, F. sp. aff. imparis ). It differs from all species listed in Table 2 having much more setae on body tergites: particularly, posterior row of Abd.IV has seven (vs. 3-4) p-setae between medial s-setae. The final decision on the status of these polychaetotic specimens was not made by us and calls for more information on their ecology and distribution.

Distribution and ecology.

The species is widely distributed in Far East of Russia, Korea and in the most northern part of Japan (Fig. 90). We suppose some records of F. fimetaria in Hokkaido refer to this species. F. imparis sp. n. is rather common in different forest litter, often in rotten wood.

Derivatio nominis.

The species has unpaired setae on anterior side of manubrium.