Oribatella Banks, 1895

Behan-Pelletier, V. M., 2011, Oribatella (Acari, Oribatida, Oribatellidae) of eastern North America, Zootaxa 2973 (1), pp. 1-56 : 3-4

Oribatella Banks, 1895

Type species: Oribatella quadridentata Banks, 1895, p. 8 .

Diagnosis. Adult. Species comprising this genus are unique among Oribatellidae ( Grandjean 1953b, Bernini 1978) in having the following combination of character states. Notogaster with immovable pteromorphs. Octotaxic system as 4 pairs of porose areas or saccules; usually without sexual dimorphism, when present that of male modified. Notogaster with 10 to 14 pairs of short to very long setae. Lamellae long, broad, with large cusps, medially converging or contiguous; cusps usually with large medial and lateral dens; translamella ( Fig. 4B arrow) variable in width and depth, with or without medial tooth. Bothridial wall distally expanded. Genal tooth with longitudinal ridge ventrally, either broad, subtriangular to subrectangular in shape, with dens ventrodistally ( Fig. 1B arrow), or broad, subrectangular, rounded distally, without dens ventrodistally ( Fig. 2E arrow). Tutorium broad, lamelliform, cusp rectangular or subrectangular, with dens distally, lying parallel to dorsal contour of prodorsum in lateral aspect, extending well anterior to insertion of rostral seta. Custodium usually present, with short to long, free distal point. Axillary saccule present at base of palp. Chelicera chelate-dentate, elongated in one species. Mentum with or without tectum, with or without recurved ridge distally ( Fig. 2D ). Palp setal formula 0–2–1–3–9(1) or 0–2–1–3– 8(1); eupathidium acm subequal in length to solenidion, forming double horn with solenidion along length or distally; in one species solenidion almost 2.5x length of acm ( Fig. 20E ). Humerosejugal porose organ Ah expressed as porose area ( Fig. 9C ) or saccule; porose area Al present or absent, when present expressed as porose area or saccule. Legs monodactylous, heterobidactylous or heterotridactylous. Femur III with seta l’ present or absent; seta v' of genua I and II present or absent. Setae l” of genua and tibiae I and II thicker, more heavily barbed and longer than setae l’ on these segments. Setae l' on genu and tibia IV thicker, more heavily barbed and longer than other setae on these segments. One or two anterodorsal spines may be present on tibia I close to, or between, solenidia φ 1 and φ 2 ( Fig. 2F arrow).

Immatures. Apopheredermous, with scalps of preceding instar maintained away from dorsal integument by modified setae da and dorsally directed h 1. Body colorless, cuticle without plicae. All or most gastronotic setae long; setation usually unideficient; larva with 11 or 12 pairs, protonymph with 15 pairs (adult loses at least c 1), deutonymph and tritonymph with 13 to 15 pairs. Setae dm and dp subequal in length to da in all immatures, or much shorter than da in deutonymph and tritonymph, or dm and dp absent from deutonymph and tritonymph. Hysterosomal sclerites absent. Pair of humeral organs present laterally in sejugal region. Without apodemato-acetabular tracheal system or porose homologues. Paraprocts atrichous in larva, protonymph and deutonymph. Genital setal formula (larva to adult): 0–1–3–5–6. Aggenital setal formula 0–0–1–1–1, or aggenital seta absent. Opisthonotal gland present in all instars. Cupule development normal. Bothridium and bothridial seta fully formed in all instars. Setation of protonymphal leg IV normal (0–0–0–0–7). Larva to deutonymph with circular line of dehiscence, such that dorsal scalp separates from ventral piece at ecdysis.

Figures

FIGURE 1 A–F Oribatella arctica Thor, differential interference contrast microscope images of adult females: A, prodorsum; B, detail of rostrum, with arrow to anteroventral dens on genal tooth; C, detail of lamellar cusps; D, micropunctate pattern on notogaster; E, pteromorph and custodium, with arrow to custodium; F, mentum of subcapitulum. Scale bars: A, C = 50µm; B, D–F = 25µm.

FIGURE 2 A–F Oribatella brevicornuta Jacot, adult female; scanning electron microscope images: A, habitus dorsal (la [left], lp [right] missing); B, habitus lateral; C, lateral of prodorsum; D, ventral from rostrum to aggenital setae; arrow to thickened, reflected ridge on mentum; E, lateral of prodorsum; arrow to distally rounded genal tooth; F, anterodorsal of prodorsum and rostrum; arrows to rostral margin and spines at base of tibia I solenidia. Scale bars: A, B, D, E = 100µm; C, F = 50µm.

FIGURE 4. A–E Oribatella dentaticuspis Ewing and Oribatella gigantea Berlese, differential interference contrast microscope images of adults. O. dentaticuspis: A. prodorsum (7 layers combined), with insert of leg I; B, lamellae, with arrow to translamella. O. gigantea, topotypic female, C, prodorsum (9 layers combined); D, lamellae; E, coxisternal region (6 layers combined). Scale bars: A, B = 50µm; C–E = 100µm.

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.

FIGURE 20. A–E Oribatella quadridentata Banks, differential interference contrast microscope images of adult: A, notogaster (5 layers combined); B, detail of pteromorph (3 layers combined); C, postanal organ, genital region to right (4 layers combined); D, chelicera; E, palp, larger arrow to solenidion ω, smaller arrow to eupathidium acm. Scale bars: A = 100 µm; B, D, E = 50 µm, C = 25 µm.