Isotomurus potapovi sp. nov. Yoosefi Lafooraki & Shayanmehr

Figs 2–3, 11c; Tables 1–3

Type material. Holotype: female on slide, Iran, Golestan province, Kordkuy, forest soil and leaf litter, 36°45′41″N, 54°07′33″E, 96 m a.s.l., 2019.01.01, leg.: E. Yoosefi Lafooraki ; Paratypes: 5 specimens in ethyl alcohol, the same data as the holotype; 1 male on slide, 2 specimens in ethyl alcohol, Guilan province, Roodbar, Rostam–Abad, Oskulak, forest soil and leaf litter, 37°00′45″N, 49°34′58″E, 128 m a.s.l., 2018.03.04, leg.: E. Yoosefi Lafooraki ; 1 male on slide, 10 specimens in ethyl alcohol, Guilan province, Rasht, Falakdeh, Forest park, forest soil and leaf litter, near pool, 37°12′18″N, 49°32′09″E, 26 m a.s.l., 2018.03.05, leg.: E. Yoosefi Lafooraki ; 3 females on slides, 30 specimens in ethyl alcohol, Guilan province, Amlash, Ostad –Kalayeh, forest soil and leaf litter, 37°06′17″N, 50°13′19″E, 426 m a.s.l., 2018.03.08, leg.: E. Yoosefi Lafooraki.

Material examined. Iran, Guilan province, Shaft, conifer forest soil and leaf litter, 7 specimens, 36°59′47″N, 49°19′31″E, 447 m a.s.l., 2018.03.05, leg.: E. Yoosefi Lafooraki ; Mazandaran province, Tonekabon, Dohezar forest, moss, 8 specimens, 36°40′05″N, 50°49′13″E, 590 m a.s.l., 2018.10.26, leg.: E. Yoosefi Lafooraki ; Mazandaran province, Abbas–Abad, moss, 15 specimens , soil and leaf litter, 4 specimens, 36°39′12″N, 51°06′43″E, 298 m a.s.l., 2018.10.26, leg.: E. Yoosefi Lafooraki; Golestan province, Bandar Gaz, Nokandeh forest, moss, 6 specimens, 36°41′19″N, 53°52′39″E, 294 m a.s.l., 2019.01.01, leg.: E. Yoosefi Lafooraki.

Description. Body size 1.35–1.43 mm. Body shape as common for the genus. Background color dark brown. Body diffusely colored, with indistinct dorsomedial band on trunk. No distinct pigmentation on lateral parts of body. Posterior part of head with small dark medial spot. Antennae, legs, and furca dark (Fig. 2). 8+8 ocelli. PAO elliptical, almost as long as the nearest ocellus. Maxillary outer lobe with 4 sublobal hairs and bifurcate palp (Fig. 3b). Labrum with 4 prelabral setae (Fig. 3b), labral edge as common for the genus, with four sharp ridges and ventro-apical ciliation (Fig. 3b). Labium with 6–7 basomedian and about 5 proximal setae (Figs 3b, 11c). Antennae about 1.8 as long as head diagonal. Antennal III organ with two thick inner sensilla and a slender lateral sensillum (Fig. 3a).

Body covered with smooth setae of unequal length. Claw with a pair of small lateral tooth and one inner tooth. Ret. with 4+4 teeth and 6–7 setae. VT with 3+3 or 5+5 laterodistal and lots of anterior and posterior setae. Manubrium densely covered by microsetae on dorsal side and with longer ciliated setae on the ventral side. Manubrial thickening simple, without teeth in medial part. Dens rather slender, continuously narrowed, with a sparse cover of dorsal setae, in basal 1/3 only. Posterior side of dens crenulated (as in I. hyrcanicus, Fig. 11a).Mucro with four teeth, without setae or lamellae. Apical tooth small. Ratio manubrium: dens: macro as 12.6: 30.5: 1. Ratio of mucro to outer edge of claw III as 0.23. Mac. long and ciliated. Modified male setae on Abd. III and IV absent.

Etymology. The new species is named on the honor of Mikhail Potapov (Moscow State Pedagogical University) for his kind help and suggestions.

Ecology. It is usually found in broad leaved forests in leaf litter, soil, and moss and also in conifer forests.

Discussion and remarks. Genetic differences in our molecular analyses confirm the status of studied populations as new species. The genetic divergence between I. potapovi sp. nov. and the other Isotomurus species is ranging from 17.4% to 29.7% (Table 2) which is similar to the divergence found among previously described species (ranging from 22.0% to 33.3%; Table 2). Intraspecific divergences of new species is 0.7% for COI and 0.1 for 28S (Table 2–3).

The new species resembles I. hadriaticus and I. aetnensis by having diffuse color pattern. The differences between them is in the number of basomedian setae on labium (7–9 setae in I. hadriaticus and I. aetnensis and 6–7 setae in new species) and number of setae on Ret. (10-15 setae in I. hadriaticus and I. aetnensis and 6–7 in I. potapovi sp. nov.) (Table 1).