Eueremaeus oblongus (C. L. Koch)

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 : 1578-1583

Eueremaeus oblongus (C. L. Koch)

(figures 5–7)

Eremaeus oblongus C. L. Koch, 1836 : Vol. 3(24).

Notaspis oblonga (C. L. Koch) : Michael, 1887: 374, pl. 30, figures 6–11; 1898: 48.

Eremaeus major Mihelčič, 1953: 105 ; 1963: 596.

Eremaeus oblongus: Nicolet, 1855: 451 , pl. 10, figure 1; Berlese, 1884: fasc. 15, no. 10, tav. 47; Sellnick, 1928: 37; Willmann, 1931: 135, figures 159–160; Balogh, 1943: 56, pl. 10, figures 13, 14; Hammen, 1952: 61; Strenzke, 1955: 40, figure 7; Schweizer, 1956: 274, figure 192; Bulanova-Zachvatkina, 1967: 172, pl. 11, figure 165; 1975: 160, figure 306.

Eueremaeus oblongus (C. L. Koch) : Mihelčič, 1963: 583, figure 2; Rajski, 1967: 153; Marshall et al., 1987: 159.

Eremaeus hepaticus: sensu Beck and Woas, 1991: 46 , figure 2.

Diagnosis. Medium-sized (488–584 m m) species with typical characters of Eueremaeus . Costulae medium long, nearly parallel or slightly diverging posteriorly, transcostular ridge absent; distinct transverse ridge present anterior to costulae; sensilli short, weakly clavate distally, distinctly expanded in their barbed portion; interlamellar setae short, smooth or very finely barbed, attenuate; tubercles La large, situated posterior to each bothridium; another pair of large tubercles situated posteromediad of bothridia; a pair of small tubercles present or absent between the latter pair of tubercles; 10 pairs of thin, finely barbed notogastral setae; five pairs of barbed anal and adanal setae; postanal process broadly V-shaped; posteromarginal sclerite subtriangular; genu III with seta d coupled with solenidion s.

Measurements. Body length 488–584 (544) m m; length of notogaster 328–384 (350) m m; width of notogaster 240–312 (287) m m. In total 16 specimens were measured.

Integument. Body colour yellowish brown. Surface of body and leg segments with relatively thin granular cerotegument. Microtuberculate in interlamellar region, lateral part of costulae and around leg acetabula. Dorsal and ventral plates weakly foveate, pedotecta I and II distinctly foveate.

Prodorsum. Rostrum rounded in dorsal view, but distinctly projecting anteroventrally in lateral view. Rostral seta thin, 30–32 m m long, barbed. Lamellar seta thin, longer than ro (42–50 m m), barbed. Costula about 52–60 m m long, nearly parallel or slightly diverging posteriorly, transcostular ridge absent, minimum distance between costulae about half costular length. Shape of costula very slightly variable (figures 5A, 6A, 7C). Distinct transverse ridge present anterior to costulae. Interlamellar seta short (28–34 m m), attenuate, smooth or very finely barbed, directed upward or slightly posteriorly. Distance between bases of in–in about twice as greater as that of ro–ro. Exobothridial seta 22–24 m m long, smooth, directed anterolaterad. Sensillus relatively short, 72–78 m m, weakly clavate distally, distinctly expanded in its barbed portion. Tubercle La large, situated posterior to bothridium. Another pair of relatively large tubercles present posteromediad of bothridia, i.e. between La–La. In some specimens one more pair of small tubercles present between latter tubercles (figures 5A, C, 6A, 7A, C).

Notogaster. Oval, about 1.2–1.4 times as long as wide; relatively flat in lateral view and slightly flattened anteriorly (figure 5A). In males notogaster relatively narrower than in females (figures 5A, 6A). Anterior margin almost straight or slightly rounded, posterior margin broadly rounded in dorsal view. Humeral projection well developed. Ten pairs of medium long (62–70 m m), thin, finely barbed notogastral setae; setae of ps series slightly shorter (52–56 m m) than others. Opisthosomal gland opening (gla) and lyrifissures ia, im, ih, ips and ip well developed. Posteromarginal sclerite subtriangular (figures 5A, B, 7A, B).

Gnathosoma . Infracapitular mentum slightly longer than wide, without noticeable microtubercles. Hypostomal setae h and a medium long, seta m about twice their length, all finely barbed (figures 5B, 7D). Chelicera relatively large, about 132 m m in length; palp about 78 m m in length; chelicera and palp similar to those of E. hepaticus ; palpal setation: 0-2-1-3-9(1).

Epimeral region. With many muscle sigillae. Sejugal, II and III apodemes well developed, aligned obliquely and nearly parallel. Epimeral setal formula 3-2-3-3, all setae smooth. Discidium rounded distally. Pedotectum I distinctly projected, pedotectum II bifurcate distally in dorso-ventral view (figures 5B, 7B).

Ano-genital region. Genital aperture nearly pentagonal, slightly widened anteriorly; anal aperture widened posteriorly. Six pairs of genital, one pair of aggenital, five pairs of anal and adanal setae. Only one specimen varied, having six setae on one side of anal plate. Adanal setae much longer and thicker than anals, both anal and adanal setae conspicuously barbed. Postanal process broadly V-shaped (figures 5B, 7B).

Legs. Measurements of leg segments given in table 2. Femora I and II with very large porose areas; trochanters III and IV with medium-sized porose areas anterodorsally. Femora III and IV with small porose areas. Tarsi and tibiae I–IV with relatively small porose areas. Trochanters III and IV with very strongly developed dorsodistal projections; ventrodistal part of trochanter III without incision, evenly rounded. 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 I–IV as shown in figure 6B–E.

Material examined. Sixteen specimens (eight females and 10 males): Mt Bogd Khan, Central Province , 6 km south of Ulaanbaatar, litter of larch forest ( Larix sibiricus Ledebour, 1833 ), 47°55∞N, 106°30∞E, elevation 1780 m, 4 June 1990 ; two specimens: Mt Ikh Ereen, Nature Reserve ‘ Gorhi Terelj’ , District Erdene , Central Province , litter of larch forest ( Larix sibiricus Ledebour, 1833 ), 48°10∞N, 107°30∞E, elevation 1820 m, 17 July 1996 ; one specimen: Mt Zaan Terelj, Nature Reserve ‘ Gorhi Terelj’ , District Erdene , Central Province , litter of larch forest ( Larix sibiricus Ledebour, 1833 ), 48°10∞N, 107°40∞E, elevation 1950 m, 23 June 1990 ; one specimen: Mt Bulgan, District Erdenebulgan, Province Arkhangai, litter of birch forest ( Betula platyphylla Sukatchev, 1911 ), 48°20∞N, 101°25∞E, elevation 1850 m, 18 May 1996 ; Leg. B. Bayartogtokh .

Remarks. The certain character states of Mongolian specimens are well in accord with those of European material redescribed by Berlese (1884), Willmann (1931), Balogh (1943), Bulanova-Zachvatkina (1967, 1975), Beck and Woas (1991), and some supplementary characters are provided in the present redescription. Body size and the shape of notogaster are somewhat variable in this species. Males are smaller and distinctly narrower than females.

Some redescriptions do not correspond well to the Mongolian material. Costulae in the specimens examined by Mihelčič (1963) from Europe are shorter and thinner, situated farther apart than those in the specimens examined herein. The notogaster of specimens redescribed by Schweizer (1956) is strongly narrowed posteriorly in comparison with the broadly rounded posterior outline in the Mongolian specimens.

Recently, Beck and Woas (1991) considered E. hepaticus and E. oblongus as conspecific, but Behan-Pelletier (1993) did not recognize the synonymy. I agree with her opinion, and according to the character states of the Mongolian material, these are apparently independent species. They can easily be distinguished by the number of notogastral setae, the incised or evenly rounded trochanters III and the development of the postanal process.

Distribution. This is a very widely distributed common species in the Palaearctic region. Ewing (1910), Jacot (1936), Hammer (1944, 1946, 1952) and Sengbusch (1957) recorded this species in North America, but Behan-Pelletier (1993) considered that these records might have been based on misidentifications.