Oribatella canadensis, Behan-Pelletier, Valerie M. & Eamer, Barbara, 2010

Behan-Pelletier, Valerie M. & Eamer, Barbara, 2010, The first sexually dimorphic species of Oribatella (Acari, Oribatida, Oribatellidae) and a review of sexual dimorphism in the Brachypylina, Zootaxa 2332, pp. 1-20 : 3-11

Oribatella canadensis sp. nov.

( Figs. 1 –25)

Material examined. Holotype: adult female. Alberta: Writing-on-Stone Provincial Park, 11.x.1990 (V. Behan-Pelletier) from litter under hawthorn, deposited in the CNC, type number 23900. Paratypes: 20 (15 females, 5 males) with same data as holotype; British Columbia: Cathedral Provincial Park, Glacier Lake, 2210m, 5.vii.1986, (V. Behan-Pelletier) 5 from snow-covered dry litter of Larix lyallii ; deposited in the CNC, RNC and the USNM.

Diagnosis. Total length of adults 365–417 μm; rostrum with medial crest extending posteriorly from distinct medial indentation; posteriorly fused region of lamellae without tooth, about 6 μm at greatest width; medial dens on cusp about 24–32 μm long, without teeth; lateral dens 38–43 μm long with 3–4 teeth; setae in 112–122 µm long; bothridial setae 90–104 µm long, with barbed, bacilliform head; tutorium about 128μm long, tutorial cusp about 58μm long, distal margin with 3 to 5 dens; custodium about 27–32 μm long; notogastral porose areas small, female with four well defined pairs, male with three pairs; Aa and A 1 in same position as in female, A2 and A3 fused, medially positioned at lateral edges of unpaired concavity in posterior midline; 10 pairs of short, weakly barbed notogastral setae 27 to 40 μm long, positioned laterally, so that lm posteriad Aa.

Description. Adults. Dimensions: Mean total length: female (n = 10) 397 µm (range 379–417); male (n = 10) 383 µm (range 365–403). Mean notogastral width: female (n =10) 272 µm (range 254–288); male (n =10) 264 µm (range 254–278).

Integument: Integument of prodorsum, notogaster, venter and mentum micropunctate ( Fig. 12 ). Integument of coxisternum, lamellae and pedotectum I with fine to very fine ridges forming irregular reticulate pattern ( Figs. 8, 9 ). Cerotegument microtuberculate, often masking micropunctate nature of integument.

Prodorsum: Rostrum with medial crest extending posteriorly from distinct medial indentation ( Fig. 8 ). Medial margins of indentation with blunt teeth, giving rostrum appearance of being flattened and toothed in flattened, slide-mounted specimens ( Fig. 14 ). Lamella (including cusp) 104–123 μm long, cusp 72–77 μm long, about 43 μm wide at level of insertion of lamellar seta. Lamellar cusps contiguous, or not, anteromedially; separated posteromedially, leaving prodorsum visible through long oval opening; posteriorly fused region of lamellae without tooth, about 6 μm at greatest width ( Figs. 1 , 7 , 17 ). Medial dens on cusp about 24–32 μm long, without teeth; lateral dens 38–43 μm long with 3–4 teeth ( Fig. 1 ). Number of secondary dens on lateral margin of cusp varying among specimens and on either side of same specimen. Long striae extending longitudinally along outer margin of lamella and cusp; short, longitudinal striae on lamella medially; remainder of lamella and cusp with short striae directed anteromedially ( Figs. 7 , 17 ). Setae ro 83–86 µm long, strongly barbed along length, acuminate, curved anteromedially, mutual distance at base about 64 µm. Setae le about 74–80 µm long, thick, heavily barbed, tapered, parallel to midline. Setae in 112–122 µm long, thick (less so than le), heavily barbed, tapered, parallel; mutual distance of pair 35–40 µm. Bothridial setae 90–104 µm long, with barbed, bacilliform head, rounded distally, stalk short, smooth; head directed slightly anterodorsally ( Fig. 1 , 9 , 17 ). Exobothridial setae about 32 µm long, thin, barbed tapered. Porose area Ad oval, positioned lateral of seta in and medial of bothridium.

Lateral aspect of podosoma. Genal tooth broad, subrectangular, with dens anteroventrally, without dens anterodorsally; with longitudinal ridge basally ( Fig. 8 ). Tutorium about 128μm long, with ridge present dorsally, tutorium curving ventrad around insertion of seta ro ( Fig. 9 ); tutorial cusp about 58μm long, rectangular, distal margin with 3 to 5 dens. Pedotectum I covering acetabulum I and part of porose area Al.

Custodium about 27–32 μm long ( Figs. 2 , 15 ), apex directed anteroventrally ( Fig. 2 ). Porose areas Al about 10 μm in diameter.

Notogaster. Length subequal to width. Anterior margin with small projection lateral of bothridium, with 5–7 transverse ridges. Pteromorph with short ridges at anterior margin; with or without small dens on anteroventral margin. Octotaxic system in form of relatively small porose areas. Female with four well defined pairs arranged as in Fig. 1 . Male with three pairs; Aa and A 1 in same position as in female, A2 and A3 fused, medially positioned at lateral edges of unpaired concavity in posterior midline, just anterior of setae h1 ( Figs. 3, 4 , 12 , 16 ). Concavity with raised medial region of variable shape ( Figs. 3 , 12, 13 ). Ten pairs of short, weakly barbed notogastral setae present; 27 to 40 μm long, with c seta longest, positioned laterally, so that lm posteriad Aa, and directed laterally ( Fig. 1 ). Subtriangular lenticulus present, not illustrated in Fig. 1 .

Ventral Region. Epimeral setae 3-1-3-3; most setae 12–19 μm long, weakly barbed, 3b, 3c and 4c 37–40 μm long, slightly thicker and more heavily barbed that other epimeral setae. Genital, aggenital, anal and adanal setae smooth, about 10–14 μm long. Postanal porose area oval 25 x 12 μm, indicated by arrow on Fig. 4 .

Gnathosoma . Chelicera chelate-dentate. Mentum with thickened transverse ridge anteriorly ( Fig. 8 ). Axillary saccule about 4 x 2 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. Small, paraxial and dorsal spines present dorsodistally on tibia I ( Fig. 9 ). Anterodorsal tubercle absent from tibia I. Seta l" on genua and tibiae I and II thicker, more heavily barbed and longer than seta l' ( Fig. 5 ); seta l' on tibiae III and IV thicker, more heavily barbed and longer than seta l" ( Fig. 6 ); seta l' on genu III, and l' on genu IV, thick and heavily barbed. Tarsi heterotridactylous.

Description. Immatures. Dimensions: Mean length: protonymph (n = 3) 252 µm (range 240–275); deutonymph (n = 2) 340 µm (330, 350); tritonymph (n = 2) 395 µm (390, 400).

Tritonymph. Integument: weakly sclerotized; weakly microtuberculate.

Prodorsum: Setae ro le, in and ex barbed, tapered, about 118, 109, 128 and 96 Μm long, respectively. Mutual distance of setae ro about 16 Μm, of setae le about 14 Μm and of setae in about 40 Μm. Setae ex directed laterally, other prodorsal setae directed anteriorly or anterolaterally ( Fig. 19 ). Bothridial seta bacilliform, heavily barbed, about 112 Μm long ( Figs. 19 , 20).

Gastronotic region: Carinate; outline slightly uneven, caused by weak swelling around setal tubercles (Fig. 21). Small, oval porose region closely medial to each seta h2, about 16 Μm at widest dimension ( Fig. 19 ). Opisthonotal gland disk-shaped, ca. 72Μm diameter, contents clear; opening ventromedial to seta lp. With normal complement of five pairs of cupules: humeral organ present ventral to seta c3. (Fig. 24). Setae long, barbed, tapered, except dm and dp short, smooth, strongly tapered (Fig. 21). Setae c1, c2, da, directed posteriorly; c1 generally lying beneath scalp of previous instar (Fig. 22). Setae c3 la, lm, lp, h3, h2 directed posterolaterally; setae h1 erect (Fig. 21). Setal lengths (in Μm) approximate (due to some terminal breakage and difficulty in measurement): c1 (70), c2 (136), c3 (96), da (98), dm (5), dp (5), la (125), lm (112), lp (96), h1 (96), h2 (96), h3 (96), p1 (64), p2 (40), p3 (40). Ventral surface of scalps with pair of setiform, sheathlike callosities, accommodating seta da of following instar (Figs. 23, 25; see Remarks); sheaths browner, more sclerotized than rest of scalp. Scalp without distinct depression at anterior end of sheath.

Ventral region: Epimeral plates contiguous medially. Epimeral setation 3-1-3-3; all smooth, about 11 Μm, 3c and 4c, barbed, about 17 Μm. Five pairs of genital setae, about 10 Μm, aligned in longitudinal row. Aggenital seta smooth, about 8 Μm. Three pairs of adanal setae barbed, about 22 Μm; two pairs of anal setae barbed, about 11Μm; 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. Setae of d series of larva (observation from larval scalp) and protonymph subequal in length, heavily barbed, tapered, directly posteriorly. In larva da about 63–69 Μm, dm and dp about 60 m; dp thicker than da and dm. In protonymph da about 69 Μm, dm and dp about 56 Μm; dp thicker than da and dm. Epimeral setation 3-1-2- 1 in protonymph, 3-1-2- 2 in deutonymph. Aggenital setae appearing in deutonymph. Paraprocts atrichous in protonymph and deutonymph. Scalps of larva, protonymph and deutonymph with molded integument to accommodate setae da of next instar, as for tritonymph.

Legs. Ontogeny of leg setae and solenidia for nymphs and adult given in Table 1 .

listed opposite the instar in which they first appear; parentheses indicate pairs of setae. Trochanter Femur Genu Tibia Tarsus

Leg I

FIGURES 20–25. Oribatella canadensis , tritonymph: 20, lateral aspect, with scalps; 21, dorsal aspect, scalps removed, seta dm indicated by arrow; 22, detail of anterior of hysterosoma, showing position of seta c1 (arrow); 23, ventral surface of scalp set, arrow indicates sheath on tritonymphal scalp to accomodate seta da; 24, detail of lateral aspect without scalps with arrow to humeral organ; 25, detail of sheaths (arrow) for setae da. Scale bars: 20, 21, 100 µm; 22, 50 µm; 23– 25, 20 µm.

Etymology. The specific epithet is for Canada, where this species has been found.

Remarks. Identification. Adults of Oribatella canadensis sp. nov. are distinguished from all North American congenerics by the character states given in the diagnosis. Based on material in the CNC, at least 50% of the North American Oribatella fauna is undescribed, and described species need redescription, thus, a key to species is premature.

Immatures—gastronotal setation

Of the over 100 species of Oribatella previously described, immatures are known for only Oribatella calcarata (Koch) ( Grandjean 1953) , O. berlesei Michael and O sexdentata Berlese ( Chistyakov 1984a, 1984b). Other than for O. sexdentata , seta c1 is subequal in shape to other c setae in nymphs. In O. sexdentata it is subequal in shape to other setae in the larva, but is smooth in the nymphs whereas other c setae are barbed ( Chistyakov 1984b). For all previously described nymphs (and the protonymph of O. canadensis ) setae dm and dp are subequal in shape and length to seta da, as illustrated for O. calcarata by Grandjean (1953; his figure 2A). In contrast, in O. canadensis sp. nov. dm and dp of the deutonymph and tritonymph become short, inconspicuous setae, whereas da remains long and barbed. A distinct change in setal morphology between nymphal instars, rather than between larva and protonymph, is unknown elsewhere in brachypyline Oribatida . The deutonymphal and tritonymphal scalps do not appear to be more closely adpressed in O. canadensis as a result of the minute nature of setae dm and dp. In contrast, in eupheredermal taxa loss of dorsocentral setae in the nymphs is associated with closely adpressed scalps.

Grandjean (1953) described in detail the form of the callosities on the scalp to accommodate da of the next instar. He indicated that this is formed during the moult process.

Figures

FIGURE 19. Oribatella canadensis, tritonymph, dorsal aspect, legs removed.

FIGURES 1 – 4. Oribatella canadensis: 1, adult female, dorsal aspect, legs removed other than proximal segments of leg I; 2, adult female, ventral aspect (legs removed); 3, adult male, notogaster; 4, adult male, detail of posterior of notogaster in posterodorsal view.

FIGURES 7 – 13. Oribatella canadensis, scanning electron micrographs. 7, adult female, frontal aspect; 8, adult female, ventral aspect anterior to pedotectum II; 9, adult female, lateral aspect, anterior of seta la, teeth on anterior of tibia I indicated by arrow; 10, adult female, posterior aspect of notogaster; 11, adult male, posterior of notogaster, dorsal aspect, medial tubercle indicated by arrow; 12, adult male, detail of tubercle and environs, fused porose areas indicated by arrows; 13, adult male, posterior of notogaster, in dorsolateral aspect. Scale bars: 7, 100 µm; 8, 9, 12, 13, 50 µm; 10, 20 µm; 12, 10 µm.

FIGURES 14 – 18. Oribatella canadensis, interference contrast micrographs from slide preparations. 14, adult female, rostrum, anterior at top; 15, custodium and seta 3 c; 16, adult male, detail of porose region, with porose area A 3 indicated by arrow; 17, adult female, interlamellar region; 18, food bolus, with arrow to hyphal fragment.

FIGURES 5, 6. Oribatella canadensis, adult female: 5, left leg II, abaxial aspect, trochanter removed; 6, right leg IV, abaxial aspect, trochanter removed.

Tables

TABLE 1. Development of setiform organs in Oribatella canadensis sp. nov. Setae (Roman) and solenidia (Greek) are

Larva - Protonymph - Deutonymph - Tritonymph v’ Adult - Leg II	d bv” - l’ l” v’	(l) σ - - - v’	(l) v’ φ1 (ft) (tc) (p) (u) s (a) (pv) (pl) e ω1 - ω2 φ2 - - (it) v” -
Larva - Protonymph - Deutonymph -	d bv” -	(l) σ - -	(l) φ (p) (tc) (ft) (u) s (a) (pv) ω1 - ω2 - -
Tritonymph v’ Adult -	(l) v’	- v’	v’ (it) v”
Leg III
Larva - Protonymph - Deutonymph v’ Tritonymph l’ Adult - Leg IV	d ev” - - l’ -	l’ σ - - - -	v’ φ (p) (tc) (ft) (u) s (a) (pv) - - - - - (it) (l) -
Protonymph - Deutonymph - Tritonymph v’	- d ev” -	- d’ l’	- (p) ft” (u) (pv) v’ φ (tc) (a) s -
Adult -	-	-	(l) -