Eueremaeus laticostulatus, 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 : 1592-1595

Eueremaeus laticostulatus sp. nov.

(figure 13)

Diagnosis. Medium to large (584–640 m m) in size; costulae long, thick, closely adjacent, nearly parallel, slightly diverging posteriorly; transcostular ridge absent or rarely very poorly developed; sensilli medium long, expanded distally, with strong barbs; interlamellar setae long, attenuate, barbed; prodorsum without distinct tubercles; 10 pairs of relatively thick, barbed notogastral setae; five pairs of distinctly barbed anal and adanal setae; postanal process relatively large, broadly V-shaped; posteromarginal sclerite subrectangular; genu III with seta d coupled with solenidion s.

Measurements. Body length 584–640 (594) m m; length of notogaster 408–424 (429) m m; width notogaster 298–344 (323) m m. Six specimens were measured.

Integument. Body colour yellowish to reddish brown. Surface of body and basal part of leg segments with relatively thick cerotegument. Microtuberculate on posterior part of prodorsum, 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, 44–48 m m in length, barbed. Lamellar seta barbed, 53–62 m m long. Costula long (62–74 m m), thick, closely adjacent, nearly parallel, slightly diverging posteriorly. Shape of costula not variable. Transcostular ridge absent. Minimum distance between costulae much less than half costular length. Interlamellar seta relatively long (58–64 m m), barbed, directed anterolaterad. Distance between bases of in–in nearly as long as that of le–le. Exobothridial seta 23–30 m m long, thin, smooth. Sensillus 92–109 m m long, expanded distally, with strong barbs. Prodorsal tubercles absent (figure 13A, C).

Notogaster. Oval, about 1.2–1.3 times as long as wide; relatively flat in lateral view and conspicuously flattened anteriorly (figure 13D). Anterior margin almost straight or slightly rounded, posterior margin broadly rounded in dorsal view. Humeral projection poorly developed. Ten pairs of relatively long (88–102 m m), thick, conspicuously barbed notogastral setae; setae of ps series shorter than others (52–56 m m). Opisthosomal gland opening and lyrifissures ia, im, ih, ip and ips well developed. Posteromarginal sclerite subrectangular (figure 13A, B).

Gnathosoma . Infracapitular mentum slightly longer than wide, without noticeable microtubercles. Hypostomal setae a, h and m relatively long, smooth (figure 13B). Chelicera and palp normal for the 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. Epimeral setal formula 3-2-3-3, all setae long, smooth. Discidium rounded distally (figure 13B).

Ano-genital region. Genital aperture relatively small, nearly oval, slightly narrowed posteriorly, about 1.2× as long as wide; anal aperture widened posteriorly, about 1.3× as long as wide. Six pairs of genital, one pair of aggenital, five pairs of anal and five pairs of adanal setae. Setae of genital region smooth, but anal and adanal setae conspicuously barbed. Postanal process broadly V-shaped (figure 13B).

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 (male): Mt Khustai, District Altanbulag, Central Province, litter of birch forest ( Betula platyphylla Sukatchev, 1911 ), 47°42∞N, 106°25∞E, elevation 1680 m, 25 May 1998, Leg. B. Bayartogtokh; five paratypes (three males and two females): 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 laticostulatus sp. nov. can be differentiated from most other species of Eueremaeus by its very long and thick costulae, and the absence of prodorsal tubercles. Most of the known species of Eueremaeus have relatively thin and short costulae, and at least one pair of prodorsal tubercles. Among the known species of this genus, only Eu. foveolatus described by Hammer (1952), Eu. proximus by Berlese (1916) both from North America and Eu. roissi (Piffl, 1965) from South Asia have somewhat long and thick costulae.

However, the North American species Eu. foveolatus is different from Eu. laticostulatus sp. nov. in its short, thick, interlamellar setae; strongly foveate prodorsum, notogaster and ventral plate; more laterally situated rostral setae; presence of small tubercles posterior to bothridia; well-developed humeral projection; relatively small postanal process; and smooth setae of anal region. Another North American species, Eu. proximus , is distinguishable from Eu. laticostulatus sp. nov. by its much shorter interlamellar setae; crenulate outline of costulae; presence of two or three pairs of distinct tubercles posteromediad of bothridia; relatively small and broadly rounded postanal process; crenulated margin of ventral carina of femora I and II; and presence of proximoventral broad cusps on tibiae I and II. The Pakistani species Eu. roissi is different from Eu. laticostulatus sp. nov. in its thin, smooth notogastral and anal setae; relatively poorly expanded sensilli; and presence of setae d on tibiae II and IV.

Etymology. The specific name ‘ laticostulatus ’ refers to the relatively thick and long costulae.