Oribatella pawnee, Behan-Pelletier & Walter, 2012

Behan-Pelletier, Valerie M. & Walter, David E., 2012, 3432, Zootaxa 3432, pp. 1-62 : 37-43

Oribatella pawnee sp. nov.

( Figs. 18D, 19–21, 29C, 30G, H)

Material examined. Holotype: male, USA, Colorado, Weld Co., Central Plains Experimental Range , Rd. 37, 8.vi.1988 (D. E. Walter), deposited in the CNC, type number 24044 . Paratypes: 10 males 10 females with same data as holotype; Canada, Alberta, ABMI-OG-1122-1 (53.1648407, -111.919342), along Township road 484 E of Bruce, 30.v.2011, from upper soil organic layers on untreed site with shrubby vegetation , 2 females; ABMI-1125 (53.07548141, -111.074829), E of juncture Routes 619 and 881, 27.v.2011, from upper soil organic layers on untreed site , 6 females; ABMI-OG-1192-1 (52.66613007, -110.693031), north of Wainwright Dunes Ecological Reserve , 19.vi.2008, from upper soil organic layers in dry grassland , 5 females, 2 males; ABMI-1224 (52.50389099, -110.730148), W of juncture Highways 41 and 13, 20.vi.2008, from upper soil organic layers in rich fen with shrubs (dwarf birch, willow), sedge, and grass understory , 3 females; ABMI-1247 (52.51489258, - 112.811302), SE of juncture Highways 53 and 56 near Buffalo Lake , 15.vi.2011, from upper soil organic layers on untreed site , 1 female; ABMI-1556 (50.07164764, -112.112526), near Vauxhall , 10.vi.2009, from upper soil organic layers on open, disturbed area with grasses and sedges , 1 female, 1 male; ABMI-1558 ne (50.00374222, - 111.578972), south of Ronalane , 12.vi.2010, dry grassland , 1 male. Paratypes deposited in the CNC, PMAE . IZ, RNC , and USNM.

Diagnosis. Total length of adults 420–470 µm. Rostrum projecting ventrally, margin rounded, without medial or lateral dens. Lamella touching medially, diverging anteromedially and separated posteromedially leaving prodorsum visible through oval opening, 16–18 µm wide and about 28 µm long; translamella with tooth. Medial and lateral dens of lamellar cusp narrow along length. Medial dens on lamellar cusp 60–64 µm long, without teeth, longer than lateral dens 53–61 µm long with 0–2 teeth on lateral margin. Bothridial seta about 95 µm long, with barbed, fusiform head, flattened distally, stalk short, smooth; head directed slightly anterodorsally. Custodium about 58 µm long, thick along full length. Notogastral porose areas small, with constricted pore canals; Aa about 6 µm in diameter. Ten pairs of weakly barbed notogastral setae present, 30–62 µm long, with seta c longest, lm posterior of Aa, and lp anterior of A1; distance p 1 –p 1 about 21 µm, less than distance h 1 –h 1 30–36 µm. Tarsi heterotridactylous.

Description. Adult. Dimensions: Mean total length: female (n = 9) 452 µm (range 445–470); male (n = 10) 434 µm (range 420–450). Mean notogastral width: female (n =8) 299 µm (range 290–310); male (n =10) 285 µm (range 260–300).

Integument: Prodorsum, notogaster, anal plates, genital plates and venter micropunctate, mentum punctate; striae on tutorium, coxisternum, genital plates, pedotectum I and anteriorly on pteromorph, those on pedotectum I forming irregular reticulate pattern. Lamellae with irregular strong, longitudinal striae laterally, fine striae medially.

Prodorsum: Rostrum projecting ventrally, margin rounded, without medial or lateral dens ( Figs 21E, F). Lamella 136–148 µm long, of which cusp 97–105 µm long, 46–50 µm wide at level of insertion of seta le; lamellar cusps touching medially, diverging anteromedially and posteromedially, leaving prodorsum visible posteriorly through oval opening, 16–18 µm wide and about 28 µm long; translamella with tooth, about 5 µm at greatest width, 5 µm in depth ( Figs 19, 21A, D). Medial and lateral dens of lamellar cusp narrow along full length ( Figs 19, 21A). Medial dens of cusp 60–64 µm long, without teeth, longer than lateral dens 53–61 µm long with 0–2 teeth on lateral margin. Seta ro 94–97 µm long, strongly barbed along full length, acuminate, curved anteromedially. Seta le 103–109 µm long, thick, heavily barbed, tapered. Seta in 125–148 µm long, thick (less so than le), heavily barbed, tapered; mutual distance of pair about 42 µm. Bothridial seta about 95 µm long, with barbed, fusiform head, flattened distally, stalk short, smooth; head directed slightly anterodorsally ( Figs 19, 21A, B, D). Exobothridial seta about 14 µm long, thin, weakly barbed.

Lateral region of podosoma: Genal tooth broad, subrectangular, with dens ventrodistally, with longitudinal ridge ventrolaterally ( Figs 21E, F). Tutorium broad, rectangular, 142–148 µm long, of which cusp 74–81 µm long, distal margin with 5–8 teeth ( Figs 21E, F). Custodium about 58 µm long, thick along length ( Fig. 29C). Porose area Al about 6 µm in diameter.

Notogaster: Length subequal to width. Anterior margin undulating, convex region lateral of bothridium with 5–8 transverse ridges. Pteromorph with or without small dens on anteroventral margin ( Fig. 21B). Octotaxic system in form of relatively small porose areas, with constricted pore canals, Aa about 6 µm in diameter ( Figs 21C, 30G, H). Ten pairs of weakly barbed notogastral setae present, 30–62 µm long, with c seta longest; lm posterior of Aa, and lp anterior of A1 ( Fig. 19); distance p 1 –p 1 about 21 µm, less than distance h 1 –h 1 30–36 µm. Small triangular lenticulus present (not illustrated).

Ventral Region: Epimeral setae mostly about 19–69 µm long, weakly barbed, 4c weakly barbed, about 41 µm long, 3c longest seta, 56–69 µm, equal to other epimeral setae in shape ( Fig. 29C). Genital, aggenital, anal and adanal setae weakly barbed, genital setae 1+5 or 2+4, about 10 µm long; anal and adanal setae 6–10 µm long. Lyrifissure iad anterolateral and almost parallel to anal plate. Postanal porose area oval 29 x 5 µm.

Gnathosoma : Anterior border of mentum without tectum; with short ridge ( Figs 21E, F). Axillary saccule about 5 x 3 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. Seta l” on genua I and II about 40 and 43 µm, respectively; l” on tibiae I and II about 36 µm. Tarsi heterotridactylous.

Immatures. Dimensions: Mean length: larva (n = 3) 207 µm (202–215); protonymph (n = 1) 264 µm.

Larva. Integument of hysterosoma with weakly sclerotized plates (as indicated in Figs 18D, 20), sclerotization independent of gastronotal setae.

Prodorsum: Setae ro, le, in and ex long, barbed, tapered, about 31, 51–72, 80 and 49–62 µm long, respectively. Mutual distance of pair ro about 9 µm, of pair le about 14 µm and of pair in about 21 µm. Seta ex directed laterally, other prodorsal setae directed anteriorly or anterolaterally ( Fig. 20). Bothridial seta fusiform, rounded distally, barbed, 77–82 µm long ( Fig. 20).

Gastronotic region: Margin carinate except anteriorly; outline uneven, caused by weak swelling around setal tubercles. Twelve pairs of setae, long, barbed, tapered, other than setae h 2, h 3. Setal lengths (in µm) approximate (due to some terminal breakage and difficulty in measurement): c 1 (130), c 2 (136), c 3 (72–90), da (125–138), dm (125), dp (87), la (102), lm (88–97), lp (67–76), h 1 (52), h 2 (15), h 3 (9). Distance (in µm) da–da, dm–dm and dp–dp about 29, 32 and 27, respectively ( Fig. 20).

Ventral region: Epimeral setation 3-1-2; seta; all smooth, about 5 µm, except 1c scaliform, covering Claparèdes organ.

Protonymph: Sclerotization as for larva.

Prodorsum: Setae ro, le, in and ex barbed, tapered, about 37, 59, 82 and 50 µm long, respectively. Mutual distance of setae ro about 10 µm, of setae le about 15 µm and of setae in about 21 µm. Seta ex directed laterally, other prodorsal setae directed anteriorly or anterolaterally. Bothridial seta fusiform, rounded distally, barbed, about 78 µm long.

Gastronotic region: Margin carinate except anteriorly; outline slightly uneven, caused by weak swelling around setal tubercles. Setae barbed, tapered. Setal lengths (in µm) approximate (due to some terminal breakage and difficulty in measurement): c 1 (64), c 2 (145), c 3 (89), da (broken), dm (78), dp (67), la (90), lm (84), lp (78), h 1 (102), h 2 (54), h 3 (93), p 1 (37), p 2 (28), p 3 (21). Distance (in µm) da–da, dm–dm and dp–dp about 16, 35 and 51, respectively.

Ventral region: Epimeres sclerotized laterally. Epimeral setation 3-1-2-1; all smooth, about 6 µm. Genital and aggenital setae occluded by legs. Axillary saccule present, about 4 x 2 µm.

Legs: Leg setation for larva, protonymph and adult given in Table 2.

TABLE 2. Setiform organs in larva, protonymph and adult of Oribatella pawnee sp. nov. Setae (Roman) and solenidia

(Greek) are listed opposite the instar in which they first appear for larva and protonymph; parentheses indicate pairs of setae.

Etymology. The species name is a noun used in apposition, reflecting the Pawnee National Grasslands of Weld Co., Colorado, where the type material was collected. In turn, this National Grassland is named in honour of the Pawnee Native Americans.

Remarks. This species is only the second known from North America with a translamellar tooth. It differs from the first, O. quadricornuta ( Michael, 1880) in the following character states (those of O. quadricornuta in parentheses): rostrum projecting ventrally, margin rounded, without medial or lateral dens (rostrum not strongly projecting ventrally, rostral margin undulating with dens; Bernini 1975 TAV. V, 2 and Figs. 9a–d); rostrum without medial crest (with distinct medial crest; Bernini 1975 Figs. 9o–q); notogastral setae h 1 curved (h 1 projecting posteriorly; Bernini 1975 Fig. 9r); epimeral seta 4c shorter and slightly thicker than seta 3c (epimeral seta 4c much thicker and longer than 3c; Bernini 1975 TAV. IV, 5).

Walter et al. (2011) considered this species to be similar to the European O. similesuperbula Weigmann, 2001 . They differ in the following characters (those of similesuperbula in parentheses, taken from Weigmann 2001): body length 420–470 mm (340–380 mm), seta 4c thin, weakly barbed (4c thick and strongly barbed), genu I without tooth (genu I with ventral tooth).

Distribution and Ecology. This species is known primarily from soils of dry grasslands or untreed sites with shrubby vegetation, from the shortgrass prairie in Colorado to mixed grasslands in southeastern Alberta. Gravid females have been observed to carry up to 3 eggs; gut contents contain dark and hyaline fungal spores and hyphae.