Oribatella metzi, Behan-Pelletier, 2011

Behan-Pelletier, V. M., 2011, Oribatella (Acari, Oribatida, Oribatellidae) of eastern North America, Zootaxa 2973 (1), pp. 1-56 : 21-27

Oribatella metzi sp. nov.

( Figs. 10–13 )

Material examined. Holotype: female USA: North Carolina, Durham Co., Duke Forest , 4.v.1979 (L. Metz), deposited in the CNC, type number 23956 . Paratypes: 7 (5 males, 2 females) with same data as holotype ; North Carolina, Buncombe Co., Bent Creek Experimental forest (A.P. Jacot) ( RNC) (2 males) (“montum” of Jacot, see Remarks) ; West Virginia, Mercer Co., 1.5 mi N on Brushcock Falls Trail, 13.vi.1971 (W. Sheer) 1 female from deep litter near cliff ( RNC) ; Missouri, Boone Co., Hinkson Creek, Columbia, S.U. Mo. Campus , 25.iv.1985 FMHD #85–127 (J. Kethley, R.A. Norton) 1 female from mixed deciduous litter on dry ridgetop ( FM) ; Alabama, DeKalb Co., De Soto State Park, Lost Falls Trail 26.ix.1992 ( VBP) 1 female from moist maple litter by Lost Falls ; same data except, 27.ix.1992, Rhodendron Trail, 1 male from moss at base of hemlock .

Diagnosis. Total length of adult 275–290 µm. Rostral margin rounded, undulating in ventral aspect with 2 small lateral dens. Microtubercles aligned on striae on posterior of notogaster, on coxisternum, on genital plates and on ventral plate laterally and posteriorly of anal plates. Translamella without tooth. Lamella (including cusp) 105–109 µm long, cusp 72–77 µm long, about 38 µm wide at level of insertion of seta le. Medial dens on cusp about 31 µm long, without teeth; lateral dens about 37 µm long with at most 1 tooth on lateral margin. Bothridial seta 90–111 µm long, with barbed, fusiform head, tapered distally. Notogastral porose areas small, about 5 µm in diameter. Ten pairs of short, smooth notogastral setae present, 16–27 µm long, with c seta longest, setae positioned laterally; lm posterior of Aa, and directed laterally, lp anterior of A1. Mutual distance p 1 –p 1 about 19 µm, subequal to distance h 1 –h 1. Aggenital setae absent. Tarsi monodactylous.

Description. Adult. Dimensions: Mean total length: female (n = 3) 288 µm (range 285–290); male (n = 5) 279 µm (range 275–280). Mean notogastral width: female (n =3) 198 µm (range 195–200); male (n =5) 188 µm (range 180–190).

Integument: Prodorsum, notogaster, anal plates, genital plates, venter and mentum microtuberculate, microtubercles aligned on striae on posterior of notogaster, coxisternum, genital plates and on ventral plate laterally and posterior of anal plates ( Fig. 10 ). With striae on tutorium, pteromorph and pedotectum I. Lamellae smooth medially, with longitudinal striae laterally ( Fig. 10 ).

Prodorsum: Rostrum rounded triangle in dorsal aspect; margin rounded, undulating in ventral aspect with 2 small lateral dens. ( Fig. 11 ). Lamella (including cusp) 105–109 µm long, cusp 72–77 µm long, about 38 µm wide at level of insertion of seta le. Lamellar cusps contiguous anteromedially; separated posteromedially, leaving prodorsum visible through oval opening, about 14 µm wide x 21 µm long; translamella without tooth, about 11 µm at greatest width, 6 µm depth ( Fig. 10 ). Medial dens on lamellar cusp about 31 µm long, without teeth; lateral dens about 37 µm long with at most 1 tooth on lateral margin. Long striae extending longitudinally along outer margin of lamella and cusp; lamella without striae medially ( Fig. 10 ). Setae ro about 73 µm long, strongly barbed along length, acuminate, curved anteromedially ( Fig. 11 ). Setae le about 57–66 µm long, thick, heavily barbed, tapered. Setae in 113–124 µm long, thick (less so than le), heavily barbed, tapered; mutual distance of pair 52–54 µm. Bothridial setae about 90–111 µm long, with barbed, fusiform head, tapered distally, stalk short, smooth; head directed slightly anterodorsally ( Fig. 10 ). Exobothridial setae about 11 µm long, thin, smooth.

Lateral aspect of podosoma: Genal tooth broad, subrectangular, with dens ventrodistally, with longitudinal ridge ventrally. Tutorium broad, rectangular about 97 µm long of which cusp about 54 µm long, rectangular, distal margin with 5–6 dens. Custodium about 26 µm long, extending to middle of pedotectum II ( Fig. 11 ). Porose area Al about 10 µm in diameter.

Notogaster: Length subequal to width. Anterior margin undulating, convex lateral of bothridium, with 5–9 transverse ridges. Pteromorph with striae; with or without small dens on anteroventral margin ( Fig. 11 ). Octotaxic system in form of relatively small porose areas, about 5 µm in diameter. Ten pairs of short, smooth notogastral setae present, 16–27 µm long, with c seta longest, setae positioned laterally, so that lm posterior of Aa, and directed laterally, and lp anterior of A1 ( Fig. 10 ); distance p 1 –p 1 about 19 µm, subequal to distance h 1 –h 1 about 19 µm. Diffuse subtriangular lenticulus present (not illustrated).

Ventral region: Epimeral setae mostly about 6–8 µm long, smooth, 4c about 32 µm long, thick and heavily barbed. Genital, anal and adanal setae smooth, about 6–8 µm long; genital setae 3 + 3, 3 setae on anterior margin of plate. Aggenital setae absent. Lyrifissure iad anterolateral and almost parallel to anal plate. Postanal porose area oval 11 x 5 µm.

Gnathosoma: Mentum with transverse carina anteriorly, with short tectum ( Fig. 11 ). Axillary saccule about 4 x 2 µm.

Legs: Setation (I to IV): trochanters, 1-1-2-1; femora, 5-5-2/3-2; 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” on genua I and II 21 µm; l” on tibiae I and II 14 µm. Tarsi monodactylous.

Description. Immatures. Dimensions: Mean length: larva (n = 1) 200 µm; deutonymph (n = 1) 209 µm; tritonymph (n = 7) 282 µm (range 275–290).

Larva. Integument weakly microtuberculate.

Prodorsum: Setae ro le, in and ex long, barbed, tapered, about 50, 70, 80 and 70 µm long, respectively. Mutual distance of pair ro about 9 µm, of pair le about 10 µm and of pair in about 30 µm. Setae ex directed laterally, other prodorsal setae directed anteriorly or anterolaterally ( Fig. 12 ). Bothridial seta fusiform, heavily barbed, about 80 µm long, tapered distally ( Fig. 12 ).

Gastronotic region: Margin carinate except anteriorly; outline uneven, caused by weak swelling around setal tubercles. Twelve pairs of setae, long, barbed, tapered, subequal in shape. Setal lengths (in µm) approximate (due to some terminal breakage and difficulty in measurement): c 1 (92), c 2 (90), c 3 (90), da (100), dm (90), dp (70), la (80), lm (80), lp (60), h 1 (?), h 2 (?), h 3 (27).

Tritonymph: Integument of gastronotal region weakly microtuberculate medially, with short striae laterally. Integument of prodorsum weakly microtuberculate.

Prodorsum: Setae ro le, in and ex barbed, tapered, about 38, 59, 66 and 45 µm long, respectively. Mutual distance of setae ro about 15 µm, of setae le about 16 µm and of setae in about 33 µm. Setae ex directed laterally, other prodorsal setae directed anteriorly or anterolaterally ( Fig. 13 ). Bothridial seta bacilliform, heavily barbed, about 76 µm long, blunt distally ( Fig. 13 ).

Gastronotic region: Margin carinate except anteriorly; outline slightly uneven, caused by weak swelling around setal tubercles ( Fig. 13 ). Setae barbed, tapered, with c 1 thinnest seta and da thickest seta; dm and dp absent ( Fig. 13 ). Setae c 1, c 2, da, directed posteriorly; c 1 generally lying beneath scalps of previous instars. Setae c 3 la, lm, lp, h 3, h 2 directed posterolaterally. Setal lengths (in µm) approximate (due to some terminal breakage and difficulty in measurement): c 1 (23), c 2 (36), c 3 (41), da (30), la (42), lm (40), lp (37), h 1 (30), h 2 (32), h 3 (34), p 1 (26), p 2 (22), p 3 (22). Ventral surface of scalps with pair of setiform, sheathlike callosities, accommodating seta da of preceding instar; sheaths browner, more sclerotized than rest of scalp.

Ventral region: Epimeral plates contiguous medially. Epimeral setation 3-1-3-3; all smooth, about 6 µm. Five pairs of genital setae, about 6 µm, aligned in longitudinal row. Aggenital seta absent. Three pairs of adanal setae barbed, about 9–13 µm; two pairs of anal setae barbed, about 9µm; cupule iad present. Axillary saccule present, about 4 x 2 µm.

Other nymphal instars: Similar to tritonymph in form and proportions, except as follows. Setae of d series of deutonymph as for tritonymph, i.e., setae dm and dp absent. Setae of d series of protonymph (observation from protonymphal scalp; no specimen available) represented by da, similar in shape to that of tritonymph, about 24 µm long and dp, similar in shape to l series, about 38 µm long; setae dm absent; distance setal bases da and dp about 74 µm, three times length da.

Legs: Ontogeny of leg setae and solenidia for known nymphs and adult given in Table 2.

Etymology. This species in named in honour of the late Dr. Louis J. Metz, who contributed extensively to oribatid mite research and soil faunal studies in North America.

Remarks. This species made it necessary to modify the diagnosis of Oribatella (see above) for characters relating to the ontogeny of gastronotic setae. In other species the protonymph, deutonymph and tritonymph have 15 pairs of gastronotal setae (adult loses at least c 1). Oribatella metzi is unique among Oribatella , and among all known brachypyline Oribatida , in that deutonymphal and tritonymphal gastronotal setal loss differs from that of the protonymph, the protonymph having 14 pairs of gastronotal setae (seta dm lost) and the deutonymph and tritonymph with 13 pairs of gastronotal setae (setae dm and dp lost).

The development of leg setae is similar to that given for Oribatella canadensis ( Behan-Pelletier & Eamer 2010) , which is the only species of Oribatella for which this is known. The only clear exception is that seta l’ is deutonymphal on tibia III and tritonymphal on tibia IV (both form in adult in O. canadensis ). In 1 tritonymph, femur III on 1 side bears seta l’.

Jacot frequently labeled slides with names that were used in internal USDA reports, but which were never published, such as ‘montum’ noted in the Material Examined Section.

Distribution and Ecology. This species is known only from litter in mideastern states of the USA ( Table 1).

Figures

FIGURE 10 Oribatella metzi sp. nov., adult male, dorsal aspect, lenticulus and legs not illustrated other than proximal segments of leg II. Scale bar = 50 µm.

FIGURE 11 Oribatella metzi sp. nov., adult male, ventral aspect, legs not illustrated. Scale bar = 50 µm.

FIGURE 12 Oribatella metzi sp. nov., larva, dorsal aspect, legs not illustrated. Scale bar = 50 µm.

FIGURE 13 Oribatella metzi sp. nov., tritonymph, dorsal aspect, legs not illustrated; arrow to humeral organ; scalps removed. Scale bar = 50 µm.