Oribatella pusilla Berlese 1916

Behan-Pelletier, V. M., 2011, Oribatella (Acari, Oribatida, Oribatellidae) of eastern North America, Zootaxa 2973 (1), pp. 1-56 : 38-39

Oribatella pusilla Berlese 1916

Oribatella pusilla Berlese, 1916, p. 308

( Fig. 19E )

Material examined. 2 topotype males, USA, Missouri, Boone Co., Hinkson Creek Recreation Area , Columbia, S.U. 29.iv.1985 FMHD #85–164 (J. Kethley, R.A. Norton) from deciduous litter in rock crevices; compared with type by RAN 19.viii.1988 (see Remarks) ( RNC) .

Diagnosis. Total length 2 topotype males 315, 340 µm; notogastral width about 225 µm. Integument of prodorsum, notogaster, including pteromorph, venter and mentum microtuberculate; coxisternum with fine striae, striae laterally thicker. Rostral margin undulating medially, with pair of small lateral dens. Lamella (including cusp) about 110 µm long, cusp about 83 µm long, about 43 µm wide at level of seta le. Lamellar cusps contiguous anteromedially, leaving prodorsum visible through oval opening, about 12.5 µm wide x 15 µm long ( Fig. 19E ). Medial dens of cusp about 40 µm long, lateral dens about 45 µm long; medial dens without teeth, lateral dens with 4–6 teeth on lateral margin, varying among specimens and on either side of same specimen. Long striae extending longitudinally on outer margin of lamella and cusp; short, fine longitudinal striae on lamella medially ( Fig. 19E ). Translamella without tooth, about 8 µm at greatest width, about 15 µm deep ( Fig. 19E arrow). Setae ro about 80 µm long, strongly barbed along length, acuminate, strongly directly medially. Setae le about 75 µm long, thick, heavily barbed, tapered. Setae in about 120µm long, thick (less so than le), heavily barbed, tapered; mutual distance of pair about 37 µm. Bothridial setae about 91 µm long, with barbed, bacilliform head, rounded distally, stalk short, smooth; head directed slightly anteromedially. Exobothridial setae thin, smooth, about 12 µm. Genal tooth broad, subrectangular, rounded distally, with strong dens ventrodistally, with longitudinal ridge ventrally. Tutorium about 113 µm long of which cusp about 64 µm long, rectangular, distal margin with 5 to 7 dens. Custodium about 30 µm long tapered. Porose area Al about 10 µm in diameter. Notogastral length subequal to width. Anterior margin undulating, convex lateral of bothridium, with 7–8 transverse ridges. Pteromorph with 2–3 small teeth along distal margin. Ten pairs of short, thin, smooth notogastral setae present; 16 to 31 µm long, with c seta longest, setae positioned laterally, lm posteromedial of Aa, lp anterior of A1. Distance setae h 1 –h 1 about 33 µm, almost twice distance p 1 –p 1, about 18 µm. Faint triangular lenticulus present. Epimeral setae mostly 8 µm long, finely barbed 4a about 18 µm, 3b, 3c about 22 µm, 4c about 25 µm long, subequal in shape, but more distinctly barbed than other setae. Genital setae about 8 µm finely barbed, 1+5, 1 seta on anterior margin of plate. Aggenital, anal and adanal setae roughened, about 6 µm long. Postanal porose area oval about 13 x 6 µm. Mentum without transverse carina anteriorly, with small tectum extending over base of gena medially. Axillary saccule about 4 x 2 µm. Leg setation (I to IV): trochanters, 1-1-2-1; femora, 5-5-2-2; genua, 2(1)-2(1)-1(1)-2; tibiae 4(2)-4(1)-3(1)-3(1); tarsi, 20(2)-15(2)- 15-12. Setae l” of genu I about 25 µm, l” of genu II about 37 µm. Tarsi heterotridactylous.

Remarks. Two topotypic males are housed in the RNC, one slide-mounted and one in ethanol. When these males were compared with type material by Roy A. Norton on 19.viii.1988, he considered these specimens conspecific. Subsequently, in 1989, he reversed this decision (according to a note inserted with one male specimen in ethanol) and considered these specimens to represent different species. I have examined these 2 male specimens and consider them conspecific. The differences noted by R. A. Norton, i.e., rostrum not pointed in one specimen and small variation in lamellar bridge, seem attributable to variation between specimens and orientation of the slide mounted specimen. In addition, there is variation in bothridial setal shape between the two specimens.

Distribution and Ecology. This species is known only from the type locality in Missouri.

Figures

FIGURE 19. A–E Oribatella nortoni sp. nov., O. plummeri Jacot, and O. pusilla Berlese, differential interference contrast microscope images of adult: A, B, Oribatella nortoni, A, detail of lamellae; B, detail of tutorium with 2 dens; C, D, O. plummeri, C, dorsal aspect of type female; D, custodium (6 layers combined); E, O. pusilla, prodorsum of topotype female, with arrow to lamellar bridge. Scale bars: A, B, D, E = 50 µm; C = 25 µm.