Eueremaeus tenuisensillatus, Badamdorj, 2003

Badamdorj, 2003, The soil mite family Eremaeidae (Acari: Oribatida) in Mongolia, with remarks on distribution and diversity of known genera, Journal of Natural History 37, pp. 1571-1610 : 1586-1590

Eueremaeus tenuisensillatus sp. nov.

(figures 9–11)

Diagnosis. Medium in size (544–580 m m); costulae short to medium long, relatively thick, nearly parallel or distinctly diverging anteriorly and posteriorly, transcostular ridge generally present, but rarely absent; sensilli medium long, slender, fusiform, smooth or with very fine and sparse barbs on its margin; interlamellar setae medium long, attenuate, very finely barbed; tubercle La large, one to three pairs of small tubercles situated just mediad of each tubercle La; 10 pairs of thin, finely barbed notogastral setae; five pairs of anal and adanal setae; postanal process U-shaped; posteromarginal sclerite subtriangular; genu III with seta d coupled with solenidion s.

Measurements. Body length 544–580 (563) m m; length of notogaster 360–384 (370) m m; width of notogaster 296–332 (309) m m. Six specimens were measured.

Integument. Body colour yellowish brown. Surface of body and leg segments with relatively thin granular cerotegument. Microtuberculate on prodorsal tubercles, lateral part of prodorsum and around leg acetabula. Notogaster and ventral plate weakly foveate, lateral part of prodorsum and pedotecta I and II more distinctly foveate.

Prodorsum. Rostrum rounded in dorsal view, but distinctly projecting anteroventrally in lateral view. Rostral seta thin, barbed, 40–50 m m long. Lamellar seta barbed, 62–68 m m long. Costula about 52–60 m m long, relatively thick, nearly parallel or distinctly diverging anteriorly and posteriorly. Transcostular ridge generally present, but rarely absent, minimum distance between costulae variable, shorter or longer than half costular length. Shape of costula variable (figures 9A, 10A, 11A). Interlamellar setae 32–34 m m long, attenuate, very finely barbed, directed anterolaterad. Distance between bases of in–in greater than that of ro–ro. Exobothridial seta 28–32 m m in length, smooth, directed anterolaterad. Sensillus medium long (78–86 m m), slender, fusiform, smooth or with very fine and sparse barbs on its margin. Tubercle La large, situated posterior to bothridium. One to three pairs of small tubercles situated just mediad of each tubercle La (figures 9A, 10A, 11A, C).

Notogaster. Oval, distinctly widened posteriorly and narrowed toward anterior; about 1.2 times as long as wide; relatively flat in lateral view and slightly flattened anteriorly (figure 10B). Anterior margin almost straight to slightly concave, posterior margin very broadly rounded in dorsal view. Humeral projection well developed. Ten pairs of medium long (70–80 m m), finely barbed notogastral setae; setae of ps series slightly shorter (55–60 m m) than others. One specimen with distinct alveoli of notogastral setae c, situated symmetrically between setae c. Opisthosomal gland

1 2 opening (gla) and lyrifissures ia, im, ih and ip well developed, ips not evident. Posteromarginal sclerite subtriangular (figures 9A, 10A, B, 11A, D).

Gnathosoma . Infracapitular mentum slightly longer than wide, with a few microtubercles. Hypostomal setae h, a and m medium long, thin, smooth (figures 9B, 11B). Chelicera and palp normal for family, similar to those of E. hepaticus ; palpal setation: 0-2-1-3-9(1).

Epimeral region. Sejugal and II apodemes well developed, aligned obliquely and nearly parallel; apodeme III poorly developed or hardly evident. Epimeral setal formula 3-2-3-3, all setae smooth. Discidium rounded distally (figures 9B, 11B).

Ano-genital region. Genital aperture widened anteriorly, longer than wide; anal aperture widened posteriorly. Six pairs of genital, one pair of aggenital, five pairs of anal and adanal setae. Adanal setae slightly longer and thicker than anal setae and conspicuously barbed. Postanal process U-shaped (figures 9B, 11B, D).

Legs. Seta d present on genu III coupled with solenidion s; genua I, II and tibiae I–IV without setae d. Formula of leg setation (including famulus) I (1-5-3-4-19), II (1-5-3-4-17), III (2-3-3-3-15); IV (1-2-2-3-12); formula of solenidia: I (1-2-2); II (1- 1-2); III (1-1-0); IV (0-1-0). Structure and setation of legs typical for genus and similar to those of Eu. oblongus .

Material examined. Holotype (female): Mt Ikh Ereen, Nature Reserve ‘Gorhi Terelj’, District Erdene, Central Province, decaying wood in larch forest ( Larix sibiricus Ledebour, 1833 ), 48°10∞N, 107°30∞E, elevation 1820 m, 17 July 1996, Leg. B. Bayartogtokh; five paratypes (three females and two males) same data as holotype. The holotype and three paratypes are deposited in the collection of the Department of Zoology , National University of Mongolia, Ulaanbaatar, Mongolia and two paratypes in the collection of the National Science Museum , Tokyo, Japan. All specimens are preserved in alcohol.

Remarks. Eueremaeus tenuisensillatus sp. nov. is easily distinguishable from other species of Eueremaeus by the fusiform, slender and smooth or marginally very sparsely barbed sensilli. Most of the known species of Eueremaeus have sensilli that are distally distinctly expanded and densely barbed. Only Eu. granulatus described by Mihelčič (1955) from Spain, Eu. proximus by Berlese (1916) and Eu. michaeli by Behan-Pelletier (1993) from North America have slender or narrowly clavate sensilli. However, the clavate part of the sensilli of all these species has very dense and strong barbs in comparison with the smooth or marginally sparsely barbed sensilli in Eu. tenuisensillatus sp. nov. Moreover, all of these compared species differ from Eu. tenuisensillatus sp. nov. in the structure of costulae, prodorsal tubercles, anal and adanal regions.

Etymology. The specific name ‘ tenuisensillatus ’ refers to the slender, fusiform and smooth or marginally very weakly barbed sensilli.