Description of Oromurcia magadanensis sp. nov. (Acari, Oribatida, Ceratozetidae) from Russia, with remarks on biogeography of the genus Oromurcia Thor, 1930.

Species of the genus Oromurcia Thor, 1930 (Oribatida, Ceratozetidae) mainly have an arctic or alpine distribution in the Western Palaearctic region and Greenland. We describe a new species of Oromurcia from Northeast Asia (Magadan Region, Russia) based on adult and juvenile instars. Numerous populations of Oromurcia magadanensis sp. nov. were found under arctic-alpine plants in a narrow stream gully with large snow accumulation on the Ola Plateau (1023 m a.s.l.). Adults of Oromurcia magadanensis sp. nov. differ from those of Oromurcia bicuspidata and O. sudetica by their smaller size, the presence of clavate, distally broadly rounded bothridial seta, tutorium with several teeth distally, and the absence of striations on the lamella. Juvenile instars of the new species differ from those of O. bicuspidata and O. sudetica by the presence of medium-sized gastronotic setae in the larva, and long lateral and posterior gastronotic setae in nymphs. We compare adult and juveniles of Oromurcia magadanensis sp. nov. with those of other members of the ceratozetid subfamily Trichoribatinae Shaldybina, 1966 from arctic or alpine regions, for which ontogeny is known, and provide revised diagnoses for adult and juvenile members of Trichoribatinae. All Oromurcia species are associated with cold wet places (periglacial habitats, bogs and fens, alpine meadows, snowbeds, and, less frequently, montane coniferous forests) in Eastern and Western Palaearctic, but they are absent from High Arctic and Siberian regions that are ultra-cold in winter. This spatial disjunction argues for a former Trans-Palaearctic range that was possibly subdivided by reсurrent cryo-arid Pleistocene episodes.

Distribution, habitats, and redescription of the rare mite species emIphidonopsis/em emsculptus/em Gwiazdowicz, 2004 (Mesostigmata: Ascidae).

Iphidonopsis sculptus Gwiazdowicz, 2004, is currently known only from the type locality in eastern Poland and a record in southwestern Finland (Huhta, 2016). Here, we record this species from twelve localities elsewhere (Europe, Siberia, Far East of Russia, Canada) indicating its broadly Holarctic geographical range. Another genus member, Iphidonopsis magnanalis (Ma Yin, 1999), is known only from China. About half of Iphidonopsis sculptus records are associated with litter of coniferous or mixed forests, but the others, including samples with juveniles (deutonymphs), were found in bracket fungi or under tree bark. The finding of two adult females on a bark beetle, Dryocoetes affaber (Mannerheim) (Coleoptera: Curculionidae: Scolytinae), suggests a phoretic association, though members of the closely related genus Zerconopsis Hull, 1918 as well as of all of the subfamily Arctoseiinae are known only from phoretic dispersal by nematoceran dipterans. The morphology of adults and an immature instar (deutonymph) of I. sculptus is redescribed and newly described, respectively, and illustrated in detail. A subdivision of the subfamily Arctoseiinae Evans, 1963 into three tribes is proposed-Arctoseiini Evans, 1963 (including Arctoseius Thor, 1930 and Iphidozercon Berlese, 1903), Zerconopsini tribe n. (Zerconopsis Hull, 1918; Xenoseius Lindquist Evans, 1965; and Iphidonopsis Gwiazdowicz, 2004), and Maxiniini tribe n. (Maxinia Lindquist Makarova, 2012).

North Pacific versus North Atlantic: a case with species of the amphiboreal littoral mite genus Thalassogamasus gen. nov. (Parasitifomes, Mesostigmata, Parasitidae).

A new amphiboreal gamasid mite genus, Thalassogamasus gen. n. is described, characterised by two distinct dorsal shields (opisthonotum hypotrichous, usually with ten pairs of setae); peritrematal shield reduced and posteriorly free; setae al1, al2 on palp genu and al on palp femur entire; dorsal chaetome homogenous; opisthosoma laterocaudally hypertrichous; in female, epigynium whip-like anteriorly, endogynium with two thick sclerotic masss; in male, tritosternum fully lost, hypostome deeply cleft, cheliceral arthrodial membrane fringelike. The new genus includes T. sidortschukae sp. nov. (Chukotka and Okhotsk coast), T. kurilensis sp. nov. (Kuril Islands) and T. lindrothi (Sellnick, 1974) (Iceland) comb. nov. The female of T. lindrothi (Sellnick, 1974) is considered conspecific with the male of Parasitus (Neogamasus) anderssoni Sellnick, 1974, comb. nov., syn. nov. All three Thalassogamasus species are seaside dwellers, inhabiting sandy beaches, salt marshes, and seaweed accumulations. Keys to the species (females and males) are presented. Peculiar morphological aspects of the dorsal shields, peritremes, and leg tarsi of the new genus are discussed. For another littoral species of Parasitidae, Parasitus kempersi Oudemans, 1902, a new combination is established, Phorytocarpais kempersi (Oudemans, 1902) comb. nov. Three littoral species of Uropoda (Phaulodinychus) Berlese, 1903 are first recorded from Russia: U. (P.) japanorepleta Hiramatsu, 1980 (northern and eastern Chukotka, Magadan Region, Kuril Islands), U. (P.) maritima Hiramatsu, 1977, and U. (P.) marihirschmanni Hiramatsu, 1977 (Kuril Islands).

Morphological development, distribution and ecology of the arctic oribatid mite Hermannia scabra (Acari: Oribatida: Hermanniidae) and synonymy of Hermannia gigantea.

The topotypes (adult and juvenile instars) of the arctic oribatid mite Hermannia scabra (L. Koch, 1879) (Oribatida, Hermanniidae) from Vaygach Island (easternmost arctic Europe) were investigated and compared with those of Hermannia gigantea Sitnikova, 1975 collected from southwest Taymyr Peninsula, northern Middle Siberia, resulting in the following new taxonomic proposal: Hermannia scabra (L. Koch, 1879) (= Hermannia gigantea Sitnikova, 1975, syn. nov.). The morphology of its all instars is described and illustrated in detail on the base of specimens collected from the northern West Siberia (Shokalsky Island). The main morphological traits are summarized. Two northern species of Hermannia with granulate notogaster, namely H. scabra and H. nodosa Michael, 1988, were regularly mixed up in the literature. Their differential diagnosis is provided after elaboration of spacious materials. The morphological differences of juvenile instars of five species of Hermannia (H. gibba (C.L. Koch, 1839), H. jesti Travé, 1977, H. nodosa, H. reticulata Thörell, 1871, and H. scabra) are given. The biotopic preferences of arctic members of Hermannia are briefly observed.

A new species of Arctoseius Thor, 1930 (Acari: Ascidae) from taiga regions of the Palaearctic, with a key to Arctoseius species of Fennoscandia, NW Europe.

A new mesostigmatid mite species belonging to the genus Arctoseius Thor, 1930, is described based on material from subarctic coniferous forests, Finland, and Altai highlands, Russia. Arctoseius ambiguus sp. nov. is similar to Arctoseius venustulus (Berlese, 1916), but can be distinguished from the latter by its larger size, wider dorsal shield, weakly sclerotized presternal platelets, pronounced differences in the length of opisthonotal setae, and distinct punctation of the anal shield. A key for 15 Arctoseius species recorded in continental North-Western Europe (Fennoscandia) is given. The Fennoscandian fauna of Arctoseius species is rather specialised. It includes four European temperate species and five cryobiontic (arctic, arcto-montane, arcto-boreo-montane) ones.

A new species of the gamasid mite genus Arctoseius Thor, 1930 (Parasitiformes, Mesostigmata, Ascidae) from Russia with a key to the multidentatus species-group.

A new gamasid mite species belonging to the genus Arctoseius Thor, 1930 is described from Russia. Arctoseius koltschaki sp. n. is distributed in the plain and mountain tundras from Khibiny Mountains to Chukotka on the north and to West Sayan Mountains on the south. A diagnosis and a key for identification of species comprising the multidentatus species-group (Arctoseius multidentatus Evans, 1955; Arctoseius wisniewskii Gwiazdowicz & Kamczyc, 2009; Arctoseius sexsetus Lindquist & Makarova, 2011; Arctoseius haarlovi Lindquist & Makarova, 2011; and Arctoseius koltschaki sp. n.) are given.

Review of the mite subfamily Arctoseiinae Evans with a key to its genera and description of a new genus and species from Siberia (Parasitiformes, Mesostigmata, Ascidae).

We redefine the subfamily Arctoseiinae of the family Ascidae, and describe a new genus, Maxiniagen. n., based on a new species, Maxinia arctomontanasp. n., whose adults display a combination of attri-butes uniquely different from other genera of the subfamily. The geographical range of Maxinia arctomontana is limited by arctic and mountain landscapes of Siberia. This description provides furtherdata on the arctic distribution and morphological diversity of the subfamily Arctoseiinae, which is unusually well represented in that region (26-83% in local gamasid mite faunas). Conceptual problems with the genus Iphidonopsis Gwiazdowicz, 2004 are reviewed, and a new combination, Iphidonopsis magnanalis (Ma & Yin, 1999) comb. n., is presented for Iphidozercon magnanalis Ma & Yin, 1999 from China. The genus Diseius Lindquist & Evans, 1965 is provisionally moved from the family Ascidae to the Digamasellidae. A new key to the genera of Arctoseiinae is presented.