Ophidiotrichus exastus Higgins

Ophidiotrichus exastus Higgins

(Figs. 8B, 10–12)

Ophidiotrichus exastus Higgins 1965, p. 57

Material examined. Holotype: adult male, USA, North Carolina, 4 mi N Cherokee, 29 May 1957, W. Mason (FMNH). USA: Alabama, De Kalb Co., De Soto State Park, Rhododendron Trail, 28.IX.1992 (VBP) 1 from rhododendron and magnolia litter; Missouri, Roaring Rocks State Park, Trail to lookout tower, 13.v.1999 (VBP) 2 from oak litter on NE slope; Lake of Ozarks State Park, Grande Glaize Beach, 14.v.1999 (VBP) 1 female from juniper litter along trail; Tennessee, Elkmont, 2.ix.1986 (G. Baker) 3 females, 1 male; Georgia, Horseshoe Bend, (D. A. Crossley) 3 females.

Diagnosis. Total length of adults 247–278 μm; length of holotype male, 247 μm (Higgins 1965). Coxisternal region with 3–4 striae extending transversely on anterior of epimere I, continuing longitudinally along coxisternum to level of acetabulum IV (Figs. 12 A, B, D). Distinct longitudinal striae laterally on lamella. Rostral margin rounded, or with small medial indentation. Lamella 96–108 μm long; cusps 59 μm long. Lamellar cusps fused for third to half length, 32–46 μm, free portion of cusps contiguous anteromedially, leaving prodorsum visible through narrow long opening about 3 μm wide x 32 μm long (Fig. 10). Medial dens on lamellar cusp about 14 μm long, rounded distally, with 1–2 teeth; lateral dens about 11 μm long with 2–3 teeth (Fig. 10). Seta ro 72–79 µm long, strongly barbed along length, acuminate, curved anteromedially. Seta le 37–40 µm long, short, thick, heavily barbed, tapered (Fig. 10). Seta in about 56 µm long, barbed, tapered; mutual distance of pair about 19 µm. Bothridial seta 80–115 µm long, narrow, setiform unilaterally, tapered, pointed distally (Figs. 8B, 10).

Exobothridial seta thin, smooth, about 20 μm (Fig. 8B). Genal tooth broad, subrectangular, with dens ventrodistally, with longitudinal ridge ventrolaterally (Fig. 8B). Tutorium narrow, tapered triangular, 64–86 μm long, of which cusp 32–35 μm (Fig. 8B). Custodium 14–16 μm long (Figs. 11, 12B). Porose area Al about 7 μm in diameter (not illustrated on Fig. 8B). Notogaster very slightly wider than long, 0.95:1. Anterior margin almost straight in interlamellar region, convex region lateral of bothridium with about 6 transverse ridges (Fig. 10). Pteromorph punctate, anteroventral margin minutely serrate, with dens anteroventrally (Fig. 12B). Octotaxic system developed as porose areas, about 8 μm in diameter. Notogastral setae present, 15–34 μm long, with seta c longest; mutual distance p1–p1 about 14 μm, slightly narrower than distance h1–h1 about 19 μm. Lenticulus absent. Epimeral setae mostly 6–10 μm long, weakly barbed acuminate, 3c and 4c longest setae, more distinctly barbed, about 21 μm long (Fig. 11). Genital, anal and adanal setae small, smooth, about 4 μm long; genital setae 2 + 4 or 3+3. Aggenital setae about 4 μm. Lyrifissure iad anterolaterad to anal plate. Postanal porose area about 13 x 4 μm (not illustrated). Anterior margin of subcapitular mentum with distinct tectum, without thickened transverse ridge (Fig. 11). Axillary saccule about 4 x 2 Μm. Chelicera large relative to body length, about 96 Μm long. Leg 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. Seta l” of genu and tibia I about 12 and 9 Μm, respectively; l” of genu and tibia II about 12 and 8 Μm long respectively. Leg monodactylous.

Remarks. The holotype male was examined, and the diagnosis given above conforms. The notogaster was dissected from this specimen, and the rest of the specimen is flattened so I am unable to confirm the length given by Higgins (1965).

The chelicera of O. exastus is about 0.36 times the body length, a proportion that is relatively large: for A. punctata it is about 0.27, for F. tessellata about 0.24, and for J. appalachia about 0.23. The relevance of this is unknown at present, as this character has not been examined in other species of Ophidiotrichus, or members of Oribatella.

Distribution and Ecology. This species appears restricted to rich litter habitats in the southern Appalachians of eastern USA. This is an area with a geological history to the Palaeozoic, a mild climate and rich topography with mountains in north-south alignment. The region has never been glaciated and today has some of the richest biodiversity in North America (Pickering et al. 2006). This region is rich in species of carabodoid mites (Reeves 1998), ceratozetoid mites (Behan-Pelletier & Schatz 2010), Damaeidae (e.g., Bayarogtokh & Norton 2007) and other invertebrates (Pickering et al. 2006). Part of this region is encompassed in the Great Smoky Mountains National Park, the subject of an All Taxon Biodiversity Inventory (http://www.dlia.org/atbi/).