Folsomia trisensilla Potapov

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 : 19-20

Folsomia trisensilla Potapov sp. n. Figs 50, 53, 58-64, 90

Type material.

Holotype, female, Far East of Russia, Khabarovsky Krai, Vaninsky District, 10 km N Vysokogorny, valley of Mulinka River, closed Picea and Abies forest on NE slope, litter, ~ 750 m alt., 29.ix.2011, coll. M. Potapov. Ten paratypes from the same location and six paratypes from the nearly same location, in litter of coniferous forests at different altitudes (600 and 900 m alt.), 29.ix.2011, coll. M. Potapov. Deposited in MSPU.

Other material.

Far East of Russia, Khabarovsky Krai. Different sites of type locality, litter and rotten wood, 29.ix.2011, coll. M. Potapov; Kamchatka. Nearby Anavgai and Esso settlements, different larch forests, litter and rotten wood, ~ 500 m alt., 4.vii.2012, coll. M. Potapov; Primorsky Krai. Terneysky District, Sikhote-Alimski Reserve, Kabany station, forest litter, 08.viii.2017, coll. N. Kuznetsova, A. Geras’kina, A. Kuprin; East Siberia: Chitinskaya Region, near foothills of Daursky Range, valley of Ilya River, ~ three km station Ara-Ilya, 50.9253°N, 113.1783°E, 887 m alt., mixed forest with Betula and Larix , 11.vii.2014, coll. A. Gulgenova.

Diagnosis.

Blind. Dorsal macrosetae (Md) present on both Th.II and Th.III. Sensillary formula incomplete (33/22224; 10/000). Medial s-setae on body tergites long, set in p-row. Ventral setae on Th.III present. Anterior side of manubrium with 3+3 paired setae, no unpaired axial setae present. Dens with 12-16 anterior setae, its posterior side with four setae in basal part. Mucro bidentate.

Description.

Body size from 1.0 to 1.3 mm, rather tubular (Fig. 50). Without pigmentation. Cuticle “smooth”. PAO slender, slightly constricted, 1.5-1.7 as long as width of Ant.I and 1.7-2.0 as long as inner unguis length (Fig. 62). Labium complete, guard setae e7 present, three proximal and four basomedian setae. Ventral side of head with 4+4 postlabial setae. Ant.I with 15-16 common setae, two ventral s-setae (s) and three basal micro s-setae (bms): two dorsal (short and long) and one ventral. 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. Several s-setae on Ant.IV tubular. Organite middle-sized, roundish.

Common setae long. Sensillary formula as 33/22224 (s), three s-setae lost (as described for the ' laconica ' subgroup (Figs 58, 59). Corner s-setae on Th.II absent (Fig. 60). Micro s-setae as 10/000 (ms). Tergal s-setae thin and long, lateral s-setae on abdomen shorter. Medial s-setae on Th. II–Abd.III situated in posterior position, on Abd. I–III between Md and Mdl. Abd.V with four s-setae arranged as three long and slender (accp1, accp2, accp3) and one latero-ventral, short ( ‘3+1’ pattern) (Figs 53, 61), accp3 s-setae as long as accp2 (0.9-1.1). Macrosetae smooth and long, 2,2/3,3,3 in number, medial ones on Abd.V slightly shorter than dens (1.0-1.3) and 3.5-4.6 times longer than mucro. Metathorax with 3+3 ventral setae.

Empodial appendage as long as 0.5-0.6 of unguis. All tibiotarsi with additional setae: 24-26 on legs I–II and 30-35 on leg III. Upper and lower subcoxae of legs I–III with 0,1/3,7 –8/6–7,7– 8 setae, respectively. Coxae of leg I with three (rarely two on one side) front setae. Tibiotarsal tenent setae pointed, some setae of distal whorl of tibiotarsi thickened. Ventral tube with 4+4 latero-distal and 7-8 posterior setae (four in distal transversal row and 3-4 in more proximal position), anteriorly without setae. Tenaculum with 4+4 teeth and a seta. Anterior furcal subcoxae with 8-10, posterior one with four setae. Anterior side of manubrium with 3+3 setae (rarely 2+3) (Fig. 63). Posterior side of manubrium with 5(4)+5(4) latero-basal, two apical setae (ap), 2+2 setae in distal transversal row (M1, ml1), two pairs of lateral setae, and 4 –6+4– 6 in central part (Fig. 63). Dens with 12-16 anterior setae. Posterior side of dens crenulated and with five setae (4 basal and one shorter one at the base of mucro), two setae at the middle present or absent (Figs 63, 64, see also the Discussion part). Mucro bidentate. Ratio of manubrium: dens: mucro = 4.1-5.0: 3.9-5.2: 1.

Remarks.

Two setae at the middle of posterior side of dens are always absent in the type populations (Fig. 63, Khabarovsky Krai). Specimens from Kamchatka possess these setae (always rudimentary and one sometimes asymmetrically lost) (Fig. 67). We accept a wide diagnosis of the new species considering both variants.

An odd population was found near Uril (Amurskaya Region) differing from the typical ones by having 4+4 (vs 3+3) anterior setae on manubrium (left out of diagnosis of the new species so far).

For difference between F. trisensilla sp. n. and F. laconica sp. n. see Remarks to the latter.

Distribution and ecology.

Known from forest litter in three localities in Eastern Asia (Fig. 90).

Derivatio nominis.

The new species name reflects the presence of three (vs four, as common for the genus) s-setae on dorsal side of Abd.V that is characteristic of the ' laconica ' subgroup.