Oribatula tibialis (Nicolet, 1855)

Ivan, O., 2013, Genus Oribatula S. Str. Berlese, 1896 (Oribatida, Oribatulidae) In Romanian Fauna, Acarologia 7 (2), pp. 175-184 : 176

Oribatula tibialis (Nicolet, 1855)

( Figure 1 )

(= O. venusta Berlese, 1908 )

Literature used for identification — Bulanova- Zachvatkina (1975), Iordansky (1991), Perez-Iaeigo (1993), Weigmann (2006), Wunderle et al. (1990). Material examined: 20 populations (7 – 11 specimens of each population) from different ecosystem types and sampling areas.

Diagnosis (type species of the genus) — Medium sized species, but comparatively, one of the larger representatives of the genus; a considerable variability of size has been observed from one population to another (Table 1). Chestnut in colour, cuticle smooth, without obvious ornamentation. Prodorsum with broad, robust lamella, without cuspis; in some specimens a short prolamella present ( Figure 1c ). Prodorsal setae robust and barbed ( Table 2). Sensillus fusiform elongated, often with a pointed tip ( Figure 1d ). Notogaster with 13 pairs of setae simple and short (p 3 missing), but well discernible. Octotaxic organ represented by 4 pairs of areae porosae, typically placed; Aa oval, larger than A 1, A 2 and A 3 ( Figure 1a, e ). Epimeral region with characteristic configuration, namely the absence of sternal furrow and the circumpedal carina well developed ( Figure 1b ). Epimeral setae according to the formula 3:1:3:3. Genito-anal region with the usual setal formula 4:1:2:3.

Distribution and autecology — Holarctic species; India ( Subias 2004).

Oribatula tibialis is the most common species of the genus, being recorded in all zones of Romania, in various habitats, from the subalpine zone to the plains, and in the Danube Delta. It is tolerant of industrial pollution (heavy metals, cement dust). Nevertheless, it prefers the soil of deciduous forests (reaching densities of 5,300 individuals/m 2) and moist meadows ( Vasiliu et al. 1993).

Figures

FIGURE 1: Oribatula tibialis (Nicolet, 1855): a – dorsal view; b – ventral view; c – variability of lamella; d – variability of sensillus; e – area porosa Aa and la seta in different specimens; scale bar (a, b): 100 µm.