Oribatella mediocris Berlese, 1916

Behan-Pelletier, V. M., 2011, Oribatella (Acari, Oribatida, Oribatellidae) of eastern North America, Zootaxa 2973 (1), pp. 1-56 : 20

Oribatella mediocris Berlese, 1916

Oribatella mediocris Berlese, 1916, p. 307

( Fig. 9A–D )

Material examined. Topotypes: male and 3 females; USA, Missouri, Boone Co., Hinkson Creek , Columbia, S.U. Mo. Campus, 25.iv.1985 FMHD #85–127 (J. Kethley, R.A. Norton) from mixed deciduous litter on dry ridgetop ( RNC) .

Other material examined. Arkansas, Montgomery Co., Little Missouri Falls Recreation Area, along trail SW of River, 19.vi.1992 (Carlton & HWR) 3 from beech and maple litter; Polk Co., N slope Rich Mountain , below 272–82 intersection, 25.iii.1992 ( HWR) 4 from old-growth .

Diagnosis. Total length 440–475 µm. Notogastral width 310–336 µm. Integument of prodorsum, notogaster, venter and mentum micropunctate, micropuncta widely spaced, about 2–4 µm apart ( Fig. 9D ). Rostrum rounded in dorsal aspect, with 2 small lateral dens. Lamella (including cusp) about 144 µm long, cusp about 127 µm long, about 55 µm wide at level of insertion of seta le. Cusps contiguous or overlapping anteromedially, separated posteromedially, leaving prodorsum visible through oval opening, about 19 µm long and 12 µm wide ( Fig. 9B ). Medial and lateral dens on lamellar cusp subequal, about 62 µm long. Medial dens without teeth; lateral dens with 3–4 teeth on lateral margin ( Fig. 9B ), varying among specimens and on either side of same specimen. Longitudinal striae on lamella laterally, lamellar integument smooth medially ( Fig. 9B ). Translamella without tooth, about 10 µm at greatest width, 5 µm deep. Setae ro about 110µm long, strongly barbed along length, acuminate, strongly directly medially. Setae le about 106 µm long, thick, heavily barbed, tapered. Setae in about 173 µm long, thick (less so than le), heavily barbed, tapered; mutual distance of pair about 48 µm. Bothridial setae about 102 µm long, with barbed, fusiform to clavate head, rounded distally, stalk short, smooth; head directed anteriorly ( Fig. 9A, B ). Exobothridial setae about 43 µm long, thin, barbed tapered. Genal tooth broad, subrectangular, rounded distally, without dens anteroventrally; with longitudinal ridge ventrally. Tutorium about 133–160 µm long, of which cusp about 65–80 µm long, rectangular, distal margin with 1 to 5 dens. Custodium about 38 µm long, tapered. Porose area Al about 10 µm in diameter. Notogastral length subequal to width. Anterior margin undulating, convex lateral of bothridium, with about 12 transverse ridges. Pteromorph with short ridges at anterior margin; with dens on anteroventral margin. Porose areas present, about 10–12 µm in diameter. Ten pairs of long, barbed, tapered notogastral setae present; 67–110 µm long, with c seta longest; lm medial of Aa, lp medial and slightly anterior of A1 ( Fig. 9A ). Distance setae h 1 –h 1 about 35–48 µm, wider than distance p 1 –p 1 about 25–29 µm. Subtriangular lenticulus present. Coxisternum with longitudinal striae. Epimeral seta 22–26 µm long, weakly barbed, other than 4a, 4b 42–44 µm, 3c, 4c 62 µm long, strongly barbed, 3c subequal in shape and width to other epimeral setae, 4c thickest seta. Genital setae 1+5, 1 pair of genital setae on anterior margin of plates, about 15 µm long. Aggenital setae about 30 µm long, anal and adanal setae about 38 µm long, strongly barbed. Postanal porose area oval 19 x 12 µm. Mentum with transverse carina anteriorly, without tectum. Axillary saccule about 4 x 2 µm. Legs setation (I to IV): trochanters, 1-1-2-1; femora, 5-5-3-2; genua, 3(1)-3(1)-1(1)-2; tibiae 4(2)-4(1)-3(1)-3(1); tarsi, 20(2)-15(2)-15-12. Setae l” of genua I and II about 53 µm. Tarsi heterotridactylous.

Remarks. Like O. gigantea (see above), this species was described by Berlese (1916) based on specimens from “Columbia (N.A.)”, which caused consistent problems in the literature until their provenance was clarified as Columbia, Missouri by Norton and Kethley (1989, p. 422). These authors subsequently collected topotypes from this locality, which were examined (see above).

Distribution and Ecology. This species is known from deciduous litter from Missouri and Arkansas.

Figures

FIGURE 9. A–D Oribatella mediocris Berlese, differential interference contrast microscope images of adults. A, habitus of topotype female (7 layers combined); B, prodorsum of topotype female, arrow to porose area Aj; C, humerosejugal porose area Ah; D, notogaster in region of porose area Aa. Scale bars: A = 100 µm; B = 50 µm; C, D = 25 µm.