Eueremaeus crassisetosus, 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: 1590-1592

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Eueremaeus crassisetosus

sp. nov.

Eueremaeus crassisetosus   sp. nov.

(figure 12)

Diagnosis. Medium in size (576–600 m m); costulae long, closely adjacent, nearly parallel or slightly diverging posteriorly; transcostular ridge absent; sensilli medium long, expanded distally, with strong barbs; interlamellar setae long, strongly expanded distally, barbed; tubercles La absent; one pair of relatively large or a few pairs of very small tubercles present posteromediad of each bothridium; 10 pairs of relatively thick, barbed notogastral setae; five pairs of anal and adanal setae; all ventral setae distinctly barbed; postanal process V-shaped; posteromarginal sclerite subrectangular; genu III with seta d coupled with solenidion s.

Measurements. Body length 576–600 (586) m m; length of notogaster 416–428 (423) m m; width of notogaster 301–308 (304) m m. Four specimens were measured.

Integument. Body colour light yellowish brown. Surface of body and leg segments with very thin granular cerotegument. Microtuberculate in interlamellar region, lateral part of costulae and around leg acetabula. Notogaster and ventral plate weakly foveate.

Prodorsum. Rostrum rounded in dorsal view, but distinctly projecting anteroventrally in lateral view. Rostral seta thin, 42–50 m m long, barbed. Lamellar seta barbed, 52–58 m m in length, thicker than ro. Costula about 58–66 m m long, closely adjacent, nearly parallel, slightly diverging posteriorly. Shape of costula constant. Transcostular ridge absent. Minimum distance between costulae less than half costular length. Interlamellar seta 50–53 m m long, expanded distally, strongly barbed, directed anterolaterad. Distance between bases of in–in slightly greater than that of le–le. Exobothridial seta 18–22 m m long, thin, smooth. Sensillus medium long (92–110 m m), expanded distally, with strong barbs. Tubercles La absent; one pair of relatively large or a few pairs of very small tubercles present posteromediad of each bothridium (figure 12A).

Notogaster. Oval, slightly narrowed posteriorly, about 1.3–1.4 times as long as wide; relatively flat in lateral view and conspicuously flattened anteriorly (figure 12C). Anterior margin broadly rounded, posterior margin narrowly rounded. Humeral projection well developed. Ten pairs of medium long (72–82 m m), barbed notogastral setae; posterior setae of ps series about 48–50 m m. Opisthosomal gland opening (gla) and lyrifissures ia, im, ip and ips well developed, ih not evident. Posteromarginal sclerite subrectangular (figure 12).

Gnathosoma   . Infracapitular mentum slightly longer than wide, without noticeable microtubercles. Hypostomal seta a relatively short, setae h and m long, all barbed (figure 12B). Chelicera and palp normal for family, similar to those of E. hepaticus   ; palpal setation: 0-2-1-3-9(1).

Epimeral region. Sejugal, II and III apodemes well developed, aligned obliquely and nearly parallel to each other. Epimeral setal formula 3-2-3-3, all setae distinctly barbed. Discidium rounded distally (figure 12B).

Ano-genital region. Genital aperture relatively long, narrow, slightly widened anteriorly, about 1.3× as long as wide; anal aperture widened posteriorly, about 1.5× as long as wide. Six pairs of genital, one pair of aggenital, five pairs of anal and adanal setae; all ano-genital setae barbed. Postanal process V-shaped (figure 12B).

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 Zorgol Khairkhan, District Bayan- Unjuul, Central Province, mountain steppe ( Stipa grandis   + Cleistogenes soongorica   ), organic layer of soils, 46°40∞N, 105°20∞E, elevation 1740 m, 8 September 1991; one paratype (female): same data as holotype; two paratypes (males): Mt Ikh Gazryn Chuluu , District Gobi-Ugtaal, Middle Gobi Province , desert steppe ( Caragana microphylla   + Stipa glareosa   ), organic debris accumulated between rocks, 45°50∞N, 107°10∞E, elevation 1700 m, 15 September 1991, Leg. B. Bayartogtokh. The holotype and two paratypes are deposited in the collection of the Department of Zoology , National University of Mongolia, Ulaanbaatar, Mongolia, and one paratype in the collection of the National Science Museum, Tokyo, Japan. All specimens are preserved in alcohol.  

Remarks. Eueremaeus crassisetosus   sp. nov. can be easily distinguished from most other species of Eueremaeus   by the distally thickened and heavily barbed interlamellar setae. Most of the known species of Eueremaeus   have distally distinctly tapered or acuminate interlamellar setae. Among them only Eueremaeus roissi   described by Piffl (1965) from Pakistan and Eu. alvordensis   , Eu. masinasin   and Eu. osoyoosensis   by Behan-Pelletier (1993) from North America have distally somewhat expanded and heavily barbed interlamellar setae.

However, the Pakistani species, Eu. roissi   is different from Eu. crassisetosus   sp. nov. in the smooth epimeral, genital and anal setae; relatively thin and more finely barbed sensilli; and presence of setae d on tibiae II and IV. The North American species, Eu. masinasin   is distinguishable from Eu. crassisetosus   sp. nov. by its much shorter costulae; relatively short interlamellar setae; and presence of prodorsal tubercles La. Two other Nearctic species, Eu. alvordensis   and Eu. osoyoosensis   , differ from Eu. crassisetosus   sp. nov. in the widely spaced and almost straight costulae; presence of only one pair of setae on epimeral region II; and presence of four pairs of adanal setae.

Etymology. The specific name ‘ crassisetosus   ’ refers to the distally expanded and strongly barbed interlamellar setae.