Nanohystrix hammerae, Norton, Roy A. & Fuangarworn, Marut, 2015

Norton, Roy A. & Fuangarworn, Marut, 2015, Nanohystricidae n. fam., an unusual, plesiomorphic enarthronote mite family endemic to New Zealand (Acari, Oribatida), Zootaxa 4027 (2), pp. 151-204 : 154-180

publication ID	https://doi.org/ 10.11646/zootaxa.4027.2.1
publication LSID	lsid:zoobank.org:pub:B2D0A15A-16BE-4311-B9F1-ADC27341D40C
DOI	https://doi.org/10.5281/zenodo.6109402
persistent identifier	https://treatment.plazi.org/id/86B17F71-3C6C-4829-9243-E31B65849341
taxon LSID	lsid:zoobank.org:act:86B17F71-3C6C-4829-9243-E31B65849341
treatment provided by	Plazi
scientific name	Nanohystrix hammerae
status	sp. nov.

Treatment

Nanohystrix hammerae n. sp.

Adult ( Figs 1–17 View FIGURE 1. A – H View FIGURE 2. A – E View FIGURE 3. A – D View FIGURE 4. A – G View FIGURE 5. A – G View FIGURE 6. A – G View FIGURE 7. A – J View FIGURE 8. A – E View FIGURE 9. A – B View FIGURE 10. A – E View FIGURE 11. A – G View FIGURE 12. A – F View FIGURE 13. A – E View FIGURE 14. A – I View FIGURE 15. A – I View FIGURE 16. A – G View FIGURE 17. A – C ). General attributes. Unusually large mites: total length 968–1213 Μm (smallest contracted male, largest distended female, respectively, not including setae). Average total length of females (n = 10) 1095 Μm (range 1029–1213), average maximum width 697 Μm (range 653–774), average maximum height 636 Μm (range 605–677); average total length of males (n = 10) 1036 Μm (range 968–1137), average maximum width 622 Μm (range 593–653), average maximum height 584 Μm (range 532–665). Sejugal band of soft cuticle ca. 100 Μm wide dorsally, ca. 20 Μm ventrally (exposed or hidden according to degree of distention and prodorsal flexing).

Body shiny in reflected light. Cuticle mostly of three types. (a) Sclerotized cuticle conspicuously porose ( Fig. 7A, B View FIGURE 7. A – J ), brownish-orange in recently collected mature adults ( Fig. 1D View FIGURE 1. A – H ) but pale, brownish-yellow and somewhat translucent (eggs and food boluses visible within uncleared females) after long preservation ( Fig. 1A, E–H View FIGURE 1. A – H ); tubercles of notogastral setae appearing slightly darker than surrounding cuticle; legs often slightly paler than body. (b) Soft cuticle of most articulations: colorless, thin, highly flexible, usually with surface granules (probably cerotegument) of various density and shape, in places forming thick vermiform pattern ( Fig. 11A, D, E View FIGURE 11. A – G ). (c) Pale cuticle of apparently intermediate flexibility: with very faint pigmentation, fine and inconspicuous porosity, and in places with fine, dense surface striation ( Figs 10D View FIGURE 10. A – E , 11F, G View FIGURE 11. A – G ).

Setae hyaline, lustrous and glassy in reflected light ( Fig. 1 View FIGURE 1. A – H ), strongly birefringent in polarized transmitted light ( Fig. 8A, E View FIGURE 8. A – E ). Most setae characterized below as: acicular if stiff, straight or slightly curved, tapering to thick point, heavily barbed (unless noted otherwise) almost to end; and attenuate if with long, taper to thin, smooth tip, with at least modest distal curvature and apparent flexibility. Barbs usually strongly developed and birefringent, like setal shafts.

Prodorsum. Outline of main aspis semi-elliptical in dorsal aspect ( Fig. 2B View FIGURE 2. A – E ), seen flat about 1.2 times wider than long (e.g. 430 x 370 Μm). In lateral view, plane of aspis usually at 50–70° angle from horizontal ( Figs 3A View FIGURE 3. A – D , 5A, B View FIGURE 5. A – G ), maximum seen ca. 80°, minimum ca. 10° (great rotation allowed by ventrosejugal articulation and broad soft cuticle of dorsosejugal, disjugal and pleural regions). Aspis cuticle finely porose throughout ( Fig. 7A, B View FIGURE 7. A – J ) and uniformly colored except for eyes (see below); sigilla of cheliceral retractor and subcapitular levator muscles in several pairs of patches occupying most of posterior half ( Fig. 7A View FIGURE 7. A – J ). Aspis dorsally convex ( Fig. 1C View FIGURE 1. A – H ); anteriorly with slightly recurved rostral margin (rm; Fig. 6F View FIGURE 6. A – G ); margin continuing posteriorly on each side as sharply defined carina (ca1), ending at lateral eye, thereby forming outline of aspis in dorsal aspect; with second carina (ca2) descending from eye at right angle ( Figs 3A View FIGURE 3. A – D , 6A View FIGURE 6. A – G ). Lateral region between carinae concave ( Fig. 1C View FIGURE 1. A – H ; presumably relating to motion of leg I), subtriangular in lateral view, with irregular ventral margin merging with soft supracoxal region (i.e., no ‘prodorsal tectum’ present); with long, narrow extension forming supportive strut (str) with distal condyle that articulates with subcapitulum ( Figs 3A View FIGURE 3. A – D , 7D, G View FIGURE 7. A – J ). Rostral tectum very narrow, crescent-shaped; undulating vertically to accommodate chelicerae ( Fig. 6B View FIGURE 6. A – G ); reflected ventral part (rostrophragma) without noticeable solid limb; about 60 Μm deep medially, effacing laterally and ending at level midway between rostral and lamellar setae. Tectum anteromedially with low, well-circumscribed, pale rostral bulge precisely dorsal to median eye, ca. 50 µm wide (rb; Figs 6C View FIGURE 6. A – G , 7H, I View FIGURE 7. A – J ). Prodorsum abruptly constricted posteriorly, forming near-vertical ‘occipital’ wall (ow; Figs 2B View FIGURE 2. A – E , 3A View FIGURE 3. A – D , 5C View FIGURE 5. A – G ), ca. 50 Μm high, edge of constriction bordered by carina ca2 (laterally) and setal pairs in, bo and xs (dorsally); wall with sharp posterior bend to form nuchal constriction (nc) that extends posteriorly for ca. 30 Μm before joining soft sejugal cuticle ( Figs 3A View FIGURE 3. A – D , 5C View FIGURE 5. A – G , 6A View FIGURE 6. A – G ). Nuchal constriction comprising posterior fifth of aspis; hidden in fully contracted specimens, in which occipital wall abuts notogaster, protecting sejugal articulation ( Figs 4B View FIGURE 4. A – G , 5D View FIGURE 5. A – G ).

Median eye (oc.m; Fig. 7H, J View FIGURE 7. A – J ) about 50 µm diameter, located on rostrophragma directly under pale, dome-like rostral bulge (rb); with strongly convex but rather thin-walled cornea. No pigment observed in median eye, but sclerotized cuticle of rostrophragma thick and pigmented posterior to eye (in region of constriction st). Paired lateral eye (oc.l) smaller, about 25 µm diameter, each immediately ventral to seta xi at junction of carinae ca1, ca2; dark pigmentation visible beneath hemispherical cuticular cornea ( Fig. 7D View FIGURE 7. A – J ), lost with clearing of specimens ( Fig. 7A, C, G View FIGURE 7. A – J ).

Prodorsal setae of various forms ( Figs 2B View FIGURE 2. A – E , 3A View FIGURE 3. A – D , 4B View FIGURE 4. A – G , 6A View FIGURE 6. A – G ), larger ones inserting on conspicuous tubercles. Rostral seta (ro) very thin, attenuate, ca. 170 Μm long, straight except for fine tip, projecting anteriorly, with only several inconspicuous barbs; pair slightly divergent, inserted close together (ca. 25–30 Μm mutual distance) on rostral bulge. Lamellar seta (le) inserted slightly proximal to mid-length of prodorsum, erect but moderately curved; relatively thick, attenuate, ca. 420 Μm long, with strong barbs in three longitudinal rows for much of length; pair widely spaced (ca. 255 Μm mutual distance). Remaining four pairs of prodorsal setae aligned at edge of occipital wall; all nearly erect, with slight posterior direction. Interlamellar (in) and upper bothridial setae (xs) larger than le and bearing up to five rows of barbs in proximal region: in about 570 Μm long, moderately attenuate; xs about 480 Μm, acicular, with strong barbs along whole length. Lower exobothridial seta (xi) small (about 50 Μm); acicular, with minute barbs visible only at high magnification. Bothridial seta (bo, = ‘sensillus’) thinner than setae on either side (in, xs); about 500 Μm long, tapering to thin flexible tip, with 2–4 rows of barbs along whole length. Bothridium ( Figs 6D View FIGURE 6. A – G , 7E, F View FIGURE 7. A – J ) with simple conical form, no proximal curvature; outer half lined with approximately 20 concentric closely-spaced, fine circular ridges (some merging), which separate even finer honeycomb pattern; inner half abruptly narrower, with coarser ridges directed internally. Bothridial rim projecting slightly from surface; posterolaterally with tongue-like flange (fl; Fig. 6D View FIGURE 6. A – G ).

Notogaster. Length about three times that of prodorsal aspis (excluding nuchal constriction); anterior width similar to that of prodorsum, about half that of maximum. Strongly but unevenly convex in both dorsal and lateral aspects ( Figs 1 View FIGURE 1. A – H , 2B View FIGURE 2. A – E , 3A View FIGURE 3. A – D ); maximum width and height at about level of setal row f; curvature steeper in posterior third (more marked in fully distended individuals). Notogaster without marginal tectum; weakly folded laterally in anterior third (humeral crease; h.cr), forming pleural concavity (more defined in contracted individuals; Figs 1D View FIGURE 1. A – H , 4D View FIGURE 4. A – G ); concavity effaces posterior to setal row e, pleural region becoming slightly convex posteriorly. General cuticle rather uniform and featureless, except as noted below; sclerotized cuticle with pores finer and less conspicuous than those of prodorsum. Well-spaced, minute surface granules in soft bordering cuticle, continuing onto anterior ( Fig. 6A View FIGURE 6. A – G , arrow) and lateral notogastral surface, becoming less dense in middle region of notogaster and absent posteriorly. Narrow transverse band of fine reticulation present in region of setal pairs c1 and c2 ( Fig. 6E View FIGURE 6. A – G , arrow). Notogaster and adanal plates fused posterolaterally, commencing at about level of seta ad2 ( Fig. 3A View FIGURE 3. A – D ; see Remark 9); narrow separating cuticle anterior to ad2 pale, finely porose, hidden in fold in contracted individuals ( Fig. 10B View FIGURE 10. A – E ).

Dorsal curvature interrupted by five transverse formations ( Figs 2–5 View FIGURE 2. A – E View FIGURE 3. A – D View FIGURE 4. A – G View FIGURE 5. A – G ). (a) Shallow, simple transverse groove (t.gr.) immediately posterior to setal pairs c1 and c2. (b) Deeper, broader transverse sulcus (t.sul) immediately posterior to setal row d. (c) Transverse type-S scissure bearing setal pairs e1 and e2. (d) Transverse type-S scissure bearing setal pairs f1, f2 and h2. (e) Transverse type-S scissure bearing setal pair h1. Setae of row d on modest tubercles within narrowly elliptical, irregularly-bordered region of lighter-colored cuticle ( Figs 1D View FIGURE 1. A – H , 2B View FIGURE 2. A – E ); central region of ellipse (around pair d1) pale, lateral regions around pair d2 intermediate in color. Edges of pale cuticle of type-S scissures generally regular anteriorly but irregular posteriorly. Erectile setae of type-S scissures each on large tubercle with associated muscles (see Discussion). Scissures differ in: setal spacing, presence and form of side extensions from posterior slope of tubercle, presence of incursions (from sclerite behind scissure) or excursions (of pale cuticle into posterior sclerite). Anterior scissure ( Fig. 2C View FIGURE 2. A – E ) with setae of row e almost evenly spaced; tubercles of pair e1 with medial extensions fusing to form narrow bridge; with small incursion of sclerotization between e1 and e2 (*), sometimes appearing like separate, intercalary sclerite. Middle scissure ( Fig. 2D View FIGURE 2. A – E ) with mixed setation, including two pairs of row f setae and seta h2; pair f1 widely separated; central third of scissure narrow, without setae or noticeable incursions or intercalary sclerites; tubercles of f1 and f2 each with basal extensions, separated by narrow articulation; tubercle of f2 also extended laterally, reaching near tubercle of h2; tubercle of h2 without extension; scissure with irregular triangular region of pale cuticle extending posteriorly from near setae f1 and f2. Posterior type-S scissure ( Fig. 2E View FIGURE 2. A – E ) with only setal pair h1; each tubercle with short medial extension.

With 19 pairs of glassy notogastral setae (including row ad); some (e1, e2, h2) extremely long, some (f1, f2, h1, p1) merging posteriorly in brush-like effect when held horizontally ( Figs 1A View FIGURE 1. A – H , 4A View FIGURE 4. A – G ). Long setae of various forms: acicular setae and proximal regions of large attenuate setae with four (sometimes five) straight rows of dense barbs, equally spaced around seta ( Fig. 4E View FIGURE 4. A – G ), forming imbricate ridges where barbs long and closely spaced ( Fig. 4G View FIGURE 4. A – G ); attenuate setae usually with two or three rows of more widely spaced barbs, at least in distal half ( Fig. 4F View FIGURE 4. A – G ). Setal shapes and representative lengths (to show relativity in average female; all significantly variable) as follows: c1 (170 Μm) finely attenuate; c2 (230 Μm) narrowly acicular; c3 (750 Μm) attenuate); cp (950 Μm) attenuate; d1 (970 Μm) attenuate; d2 (320 Μm) narrowly acicular, but curved; e1 (1900 Μm) attenuate; e2 (1750 Μm) attenuate; f1 (1200 Μm) acicular; f2 (1000 Μm) acicular; h1 (880 Μm) acicular; h2 (1350 Μm) attenuate; h3 (430 Μm) narrowly acicular; p1 (790 Μm) acicular; p2 (1300 Μm) attenuate; p3 (330 Μm) narrowly acicular; ad1 (1250 Μm) attenuate; ad2 (370 Μm) attenuate; ad3 (200 Μm) attenuate. Six large pairs, including e1, e2, f1, f2, h1 and h2, inserting on intercalary sclerites within scissures (described above), apparently erectile. Several setal pairs with unusual locations ( Figs 2B View FIGURE 2. A – E , 3A View FIGURE 3. A – D , 9B View FIGURE 9. A – B ): c3 high on pleural surface, aligned with setal row d and immediately anterior to cp; f1 somewhat displaced laterally; h2 uniquely incorporated as third erectile setal pair in middle transverse scissure; h3 more anterior and dorsal than usual in oribatid mites; p2 dorsoventrally aligned with p3 or even anterior to it.

Typical five pairs of notogastral proprioceptors present, but in unusual locations ( Fig. 3A View FIGURE 3. A – D ); each minute, ca. 6– 7 µm, cupular in form, round or slightly elliptical when seen face-on ( Fig. 11G View FIGURE 11. A – G ). Two pairs located within scissures: im in pale or intermediately pigmented cuticle at lateral extreme of anterior scissure, closely posterodorsal to seta cp; ip within middle scissure, between setae f2 and h2, anterior to lateral extension of f2. Three pairs in lateral region: ia and im on sclerotized cuticle ca. 30–50 µm from ventral edge of notogaster, ia about at level of cp or c3, ih at level of middle scissure; ips in pale cuticle near anterior end of separation between main notogaster and adanal region ( Fig. 11F, G View FIGURE 11. A – G ).

Five pairs of conspicuous cuticular disks present, two large, three small ( Figs 2B View FIGURE 2. A – E , 3A View FIGURE 3. A – D ; see Remark 2), discernable in both transmitted and reflected light by lack of color ( Figs 1D View FIGURE 1. A – H , 8B, C View FIGURE 8. A – E ); cuticle finely porose. Small disks all in anterodorsal region, usually slightly elliptical: cd1 smallest (ca. 15 µm length), about 30 µm posterior to seta c1; cd2 (ca. 30 µm) about 40–50 µm ventral to seta c2; cd3 (ca. 25 µm) about 60–70 µm posterior to seta c2. Larger two disks circular to slightly elliptical (ca. 55–60 µm); cd4 located midway between erectile setae f2 and h1 at end of pale triangular extension from middle scissure; cd5 immediately posterolateral to seta h1. Two linear files of tendon insertions present anterolaterally (ti; Figs 2B View FIGURE 2. A – E , 3A View FIGURE 3. A – D ). One file of 6–10 minute, uniform, darkly sclerotized, closely spaced internal projections directed posteriorly from near disk cd3, each projection serving as insertion for one thin tendon ( Fig. 8C View FIGURE 8. A – E ). Second, less distinct row of insertions, perpendicular to first, directed dorsomedially in transverse sulcus behind seta d2; only most lateral few insertions of second row with internal projections.

Venter. Coxisternum comprising about one-third of ventral surface ( Figs 9B View FIGURE 9. A – B , 10B, C View FIGURE 10. A – E ); nearly quadrate overall, with trochanter of each leg articulating at about same distance from midline. Muscle sigilla weakly defined in transmitted light. Paired plates of epimeres I and II strongly convex and independent both from other member of pair and from adjacent epimeral plates; soft cuticle medially separating plates of epimere I very broad, that of epimere II very narrow ( Fig. 11A View FIGURE 11. A – G ). By contrast, epimeres III and IV without soft medial cuticle (but with line of cuticular weakness visible in transmitted light; Fig. 9B View FIGURE 9. A – B ); epimeres fused to each other in medial half, forming single unit. Central fused region of unit relatively flat, but lateral half of each epimere discrete, cylindrical. Epimere III articulating with epimere II through narrow ventrosejugal articulation having weak transverse striation; posterior edge of epimere IV strongly curved, sharply defined, slightly overhanging genital plates and hiding broad articulation. Without coxisternal apodemes; epimere IV laterally with thickened internal ridge supporting articulation with leg trochanter. Coxisternal setation 3-1-3-4; no variation noted. Setae 1a, 2a, 3a and 4a straight, tapered only distally, conspicuously barbed ( Fig. 10E View FIGURE 10. A – E ); others attenuate to various degrees, with fewer barbs or nearly glabrous. Setae range in size from about 85 Μm (3a) to 150 Μm (1b).

Supracoxal seta eI ( Fig. 11B View FIGURE 11. A – G ) minute, spiniform (ca. 13 Μm), apparently immobile (no clear alveolus); inconspicuously located on dorsal face of epimere I at edge of sclerotization. Anterodorsal corner of epimere II with sharp spine or cluster of up to four smaller spines ( Fig. 11C View FIGURE 11. A – G ). Podocephalic canal (cpc; Figs 3A View FIGURE 3. A – D , 7D View FIGURE 7. A – J ) typical in form, running from supracoxal region of epimere I across soft pleural cuticle, then onto subcapitulum near articulation with prodorsum; often hidden in cuticular fold ( Fig. 7G View FIGURE 7. A – J ).

Genital plates about 1.2 times longer than broad (seen flat), with gently curving outer margin; pale inner margin often reflexed ( Fig. 10A View FIGURE 10. A – E ); cuticle connecting genital and anal plates mostly soft, sharply folded, reminiscent of shirt-collar, medially with small patch of sclerotized cuticle (not illustrated) observed only with dissection. With nine pairs of smooth, attenuate genital setae (ca. 70–85 Μm long) arranged in two longitudinal rows: six setae aligned with medial margin, anterior pair directed ventromedially and others sharply posteroventrally; three other pairs near lateral margin of plate. Aggenital region soft, without evidence of plate or aggenital setae. Cuticle of genital vestibule soft, granulate; genital papillae of simple form (ca. 50 Μm diameter), all three pairs similar ( Figs 3B View FIGURE 3. A – D , 9B View FIGURE 9. A – B ), with lightly pigmented cap.

Ovipositor with typical, double-walled tubular form and plicate cuticle ( Figs 3B, C View FIGURE 3. A – D , 12A, B View FIGURE 12. A – F ); about 500–650 Μm when fully extended, half that when folded inside body. Distal lobes normal in form: paired anterior (dorsal) lobes and larger single posterior (ventral) lobe, the latter with convex, slightly sclerotized inner face that coapts with anterior lobes in retracted ovipositors (cf. Fig. 12A, B View FIGURE 12. A – F ). With normal complement of nine pairs of simple, eupathidial setae, but with unusual distribution (see Remark 6). Three pairs of coronal setae (k; 40–50 Μm); two pairs within primary fold constriction, one well below on anterior side. Each anterior lobe with three setae: τ1 (ca. 70 Μm) largest and most distal; τa (ca. 40 Μm) most proximal, at limit of plicate cuticle; τb (ca. 40 Μm) at intermediate level and more laterally positioned. Posterior lobe with three pairs of setae: ψ1 (ca. 75 Μm) most distal; ψa and ψb (each ca. 35 Μm) at same level, near limit of plicate cuticle.

Spermatopositor ( Figs 3D View FIGURE 3. A – D , 12C View FIGURE 12. A – F ) very short (ca. 50–60 Μm), conical, but with weakly striate lobes discernable; ovate in cross-section at base (ca. 50 x 60 Μm). With eight pairs of small eupathidial setae (20–25 Μm), all tapered but blunt-ended; each anterior lobe with three at base (k) and three distally (τ); posterior lobe with two pairs of setae (ψ).

Plates of anal region collectively forming vague trapezoid in contracted individuals, widest posteriorly ( Fig. 10A, B View FIGURE 10. A – E ). Seen in distended individuals, anal plates widely separated from peranal plates and adanal region of notogaster ( Fig. 9B View FIGURE 9. A – B ), mostly by pale, porose cuticle with inconspicuously linear pattern. Each plate about four times longer than wide (ca. 280 x 70 Μm); tapered anteriorly to about one-third maximum width. Anal setae aligned along midline of plate; all attenuate, barbed, increasing in size posteriorly (an3 157 Μm, an2 270 Μm, an1 970 Μm); an2 closer to an3 than to an1. Peranal plates extremely narrow, strap-like (ca. 300 x 15 Μm); medial edge soft, unpigmented, often flared outward. Plate pair fused anteriorly to form small ‘preanal’ apodeme for muscle attachment ( Fig.11 View FIGURE 11. A – G H, I); similar small ‘postanal’ apodeme posteriorly for attachment of suspensor muscles (see Discussion). Single pair of peranal setae small (pa, ca. 60 Μm; Fig. 10D View FIGURE 10. A – E ), attenuate, weakly barbed; inserted on lateral edge near anterior end of plate.

Gnathosoma ( Figs 13–15 View FIGURE 13. A – E View FIGURE 14. A – I View FIGURE 15. A – I ). Subcapitulum and chelicerae usually oriented vertically or nearly so ( Figs 3A View FIGURE 3. A – D , 5A View FIGURE 5. A – G ), even slightly posteroventrally in some individuals. Subcapitulum relatively small but unusually wide at base (ca. 1.2 times wider than long), abruptly narrowed by almost 50% at level of palp insertion ( Fig. 15A View FIGURE 15. A – I ). Stenarthric, ( Fig. 13A View FIGURE 13. A – E ): triangular mentum well delineated by pair of oblique labiogenal articulations (lg) closely approaching each other anteromedially, near base of lateral lips. Mentum (H) paler than genae; with one pair of attenuate, sparsely barbed setae (h, ca. 80 Μm). Gena (G) without dorsal rasp-like region of denticles; each gena with three weakly barbed ventral setae: posterior two (n, ca. 90 Μm; m, 80 Μm) nearly aligned with h, distal seta (a, 90 Μm) about at level with anterior corner of mentum. Lateral lips (LL) relatively large, fully exposed in ventral aspect, each clearly separated from gena by postadoral articulation (d); distal halves tapering to narrow adjacent tips. Each lip with triangular sclerite on ventral face and three pairs of adoral setae, each having few, minute barbs; distal seta or1 (ca. 30 Μm) inserted in soft cuticle immediately distal to tip of sclerite, setal base distinctly flared, without normal alveolus; setae or2 and or3 (ca. 55 Μm) inserted on sclerite, at mid-length of lip, on small tubercles and in normal alveoli, in nearly transverse row. Dorsal surface with several longitudinal rows of extremely minute cilia or denticles, close to medial edge in distal half of lip. Rutellum (Ru) atelobasic; no rutellar brush; narrow, nearly uniform in width; distally rather chisel-like, with three aligned distal teeth. Rutellum basally incorporated smoothly with elongated manubrial zone (Mn) of gena; manubrial-rutellar unit angled rather sharply anteromediad, with rutellar tips nearly meeting just anterior to lateral lips ( Fig. 14B, D, E View FIGURE 14. A – I ); distal limit of manubrium (c) well-marked in transmitted polarized light due to strong birefringence of rutellum ( Fig. 15B View FIGURE 15. A – I ); abaxial fissure (αf) marking base of manubrium visible in both SEM ( Fig. 14B View FIGURE 14. A – I ) and transmitted light ( Fig. 15B View FIGURE 15. A – I ). Dorsal face of subcapitulum without capitular apodeme; posterior margin supported by pair of narrow transverse bands of sclerotization interrupted by U-shaped medial notch (m.no; Fig. 15A View FIGURE 15. A – I , insert). With flattened, sometimes pointed tubercle (sub.t) on each dorsolateral corner of subcapitulum, at articulation with prodorsal condyle pK ( Fig. 7G View FIGURE 7. A – J ). Postpalpal seta (ep; ca. 8–10 Μm) spiniform, erect, inserted without alveolus (apparently immobile) just anterior to tubercle ( Fig. 15D View FIGURE 15. A – I ). Labrum (Ls; Fig 15B, C View FIGURE 15. A – I ) broad, with slightly raised medial ridge; distally rounded, extending almost to level of rutellar tips (if not elevated). Distal quarter of labrum with complex but slightly variable structure: with three transverse rows of dense spicules spanning plane of symmetry on dorsal face and fourth, most ventral row usually interrupted medially by larger distal spines, usually one pair ( Figs 14F View FIGURE 14. A – I , 15C View FIGURE 15. A – I ); ventral surface usually with several nipple-like lobes and proximal folds ( Fig. 14E View FIGURE 14. A – I ).

Palp relatively large and conspicuous ( Figs 4B View FIGURE 4. A – G , 14A View FIGURE 14. A – I , 15A View FIGURE 15. A – I . Simple in form ( Fig. 13B View FIGURE 13. A – E ); five freely articulating segments with typical proportions: trochanter, genu and tibia short; femur about twice length of genu; tarsus elongated, about equal to femur and genu combined. Tarsus finely striated distally; with dorsal lyrifissure proximally. Setal formula (trochanter to tarsus) 0- 2 -1-3-13 (solenidion not included; tarsus count includes fused distal eupathidia as two); probable homologies indicated on Fig. 13B, C View FIGURE 13. A – E . All setae of femur, genu and tibia, and several proximal setae of tarsus, attenuate and noticeably barbed; more distal setae with fewer barbs, or none. Tarsal solenidion ω finely tapered, flexible; inserted unusually far distally, in terminal quarter of segment, extending slightly beyond most distal tarsal setae when straight. Homology of tarsal setation incompletely known (see Remark 10); most tarsal setae with soft cuticle of alveolus teardrop-shaped, pointed distally. Six distal tarsal setae eupathidial, including probable acm and ultimal (ul) pair ( Figs 13C View FIGURE 13. A – E , 14G View FIGURE 14. A – I ); ul' and su fused in basal 2/3, but individual setae distinguishable, spread noticeably in distal third. Variations: one specimen with femoral seta sup absent; another with seta inf doubled (represented by two closely-spaced, unusually small setae).

Chelicera usually oriented vertically; chelate-dentate in form, with typical outline in lateral view ( Fig. 13D, E View FIGURE 13. A – E ). Cheliceral frame not encroaching onto principal segment; cuticle of latter distinctly porose proximal to chela. Trochanter (Tr) distinct, relatively large, well sclerotized ventrally; soft dorsally, merging with and losing distinctness from soft granular cuticle of cheliceral frame. Trochanter with tongue-like, well sclerotized tectum (tr.t; Fig. 15E–G View FIGURE 15. A – I ) ventrally, overhanging articulation with principal segment. Tectum with hyaline cuticular coating, extending distally as thin, colorless fringe with minute cilia; several large spines more basally on abaxial edge of tectum, distal to articulation with principal segment. Principal segment strongly asymmetrical, giving broad, flat-faced appearance to anterior of mite ( Fig. 6B, C, G View FIGURE 6. A – G ). Adaxial face almost flat, forming coaptive surface when chelicerae close together ( Fig. 6B View FIGURE 6. A – G ), accentuated dorsally by carina (dc; Fig. 6C View FIGURE 6. A – G ) bearing several short spines; abaxial face strongly convex, increasingly so as chelicera broadens proximally to maximum width, close to proximal end ( Fig. 15E View FIGURE 15. A – I ). Abaxial face of principal segment with few features: proximal third with about dozen minute, sharp spicules, many at end of fine, sharply defined carinae angling posterodorsad ( Figs 7J View FIGURE 7. A – J , 13E View FIGURE 13. A – E , 15H View FIGURE 15. A – I ); fixed digit with low carina (c.fd.) near middle ( Figs 13E View FIGURE 13. A – E , 14B View FIGURE 14. A – I ); movable digit with short carina (c.md) proximally, which coapts to edge of fixed digit if chela closed. Adaxial face of principal segment ( Fig. 13D View FIGURE 13. A – E ) deeply excavated in proximal half, accommodating asymmetrical insertion of trochanter; with about half-dozen spicules in distal half. Without Trägårdh’s organ, but with attached, irregular, ‘puffy’ (perhaps inflatable; Fig. 15E View FIGURE 15. A – I ) vesicular band of soft cuticle (vb) running distally from trochanter to end at strong spine (ca. 15 Μm) on mid-face of fixed digit. Small, freely projecting scale-like flap (sc) present, with ciliate margin, arising at about level of articulation between segments. Lamellated organ (l.or.; Fig. 15F View FIGURE 15. A – I , insert) present close to flap (see Remark 5). Fixed digit of chela strongly birefringent distal to seta chb; with five teeth (including terminal tooth and small tooth high on adaxial face). Movable digit birefringent in distal half; with four teeth (including terminal and very weak subterminal tooth). Principal segment with two attenuate setae, both aligned near midline, just abaxial to dorsal carina ( Fig. 13D, E View FIGURE 13. A – E ): cha (ca. 65 Μm) clearly barbed, inserted at base of fixed digit; chb (ca. 40 Μm) nearly smooth, inserted at mid-level of fixed digit. Pronounced, often pigmented tendon (ts; Fig. 15I View FIGURE 15. A – I ) present, attaching bands of massive levator muscle to movable digit; articulation of digit with distinct onchophysis op' ( Fig. 13D View FIGURE 13. A – E ).

Legs. ( Figs 16 View FIGURE 16. A – G , 17 View FIGURE 17. A – C ). Relatively long: leg IV longest, about as long as body (varies with degree of body distension); approximate proportions of others (relative to IV): 0.8 (I), 0.7 (II), 0.8 (III). Legs III and IV with normal, posterolateral direction in all specimens. Legs I and II unusually mobile (inferred from highly variable positions in preserved specimens); with normal anterolateral orientation in some specimens ( Fig. 1D, F View FIGURE 1. A – H ) but in others directed laterally, posterolaterally, or even posterodorsally (at nearly same angle as legs III and IV; Figs 1A, B, G View FIGURE 1. A – H , 10B View FIGURE 10. A – E ). Leg I, and to small extent leg II, rotatable crab-like; i.e. ventral surface twisted forward in some specimens ( Fig. 4B View FIGURE 4. A – G ). Surface of most leg segments nearly smooth, but tarsi finely striated distally ( Fig. 14H View FIGURE 14. A – I ); cuticle finely porose but without regions of larger pores (porose areas) or other surface patterns. Each tarsus with small proximodorsal lyrifissure. Pretarsus of all legs similar, tridactylous with empodial claw slightly longer and about twice width of lateral claws (14H); claws without denticles; ambulacrum without separate condylophores. Except for trochanters I and II and all tarsi, leg segments roughly tubular and similar in size ( Figs 10B View FIGURE 10. A – E , 16 View FIGURE 16. A – G , 17 View FIGURE 17. A – C ). Trochanters I and II relatively short, less than half length of respective femur. Tarsi much elongated; tarsus I about 6–7 times longer than proximal width, tapering gradually from base to tip; tarsus IV about 11–12 times longer than proximal width, with most tapering in proximal quarter, distal to which segment almost isodiametric, very thin and somewhat flexible (based on variations in preservation; Fig. 12F View FIGURE 12. A – F ); form of tarsi II and III progressively intermediate between that of I and IV.

Leg setation, expressed as formula (I-II-III-IV; famuli and minute setae d included, solenidia excluded): trochanters (1-1-2-2); femora (6-6-4-4); genua (5-5-4-4); tibiae (6-6-4-4); tarsi (20-18-17-15). Setal homologies given in Figs 16 View FIGURE 16. A – G , 17 View FIGURE 17. A – C and Table 1. Noted variations include two tarsi I lacking seta it' and one tarsus II lacking seta tc ' (20 of each leg examined). Most setae moderately to strongly barbed, exceptions being distal setae of tarsi, on which barbs usually small and sparse as illustrated, and smooth eupathidial setae and regressive seta d of genu and tibia I (see below). As in body setae, with birefringent core extending into all barbs. Alveoli of tarsal setae dropshaped, pointed distally. Six setae eupathidial on tarsus I, including s, m" and pairs (it) and (p). Famulus (e) of tarsus I small (ca. 20 Μm) but conspicuous, being most proximodorsal setiform organ of segment and erect on small tubercle ( Figs 14I View FIGURE 14. A – I , 16C View FIGURE 16. A – G ); with attenuate main tip and usually three simple or forked barbs clustered near mid-length (rarely fourth barb present); tip and barbs all open distally ( Fig. 14I View FIGURE 14. A – I , insert). Famulus of tarsus II more distal, usually about mid-length on tarsus, smaller (ca. 10–12 Μm), strongly angled toward surface; variable in formattenuate to spiniform, sometimes with one small distal barb giving forked appearance ( Fig. 16F, G View FIGURE 16. A – G ).

TABLE 1. Ontogeny of setae (Roman letters) and solenidia (Greek letters) in Nanohystrix hammerae n. sp. 1 1Setae and solenidia are first added at the indicated instar (La, Pn, Dn, Tn, Ad = larva, protonymph, deutonymph, tritonymph, adult, respectively) and remain present in subsequent instars; dash indicates no addition. Setae in parentheses represent pseudosymmetrical pairs, brackets indicate physical change; for seta d, subscripts m, n indicate that the seta is minute or normally formed, respectively.

* Setae in these rows are present in the tritonymph, but as no deutonymphs were studied they may have been added in either the deuto- or tritonymph.

Disjunctions of tarsal setae as follows (' = anterior member more distal; " = posterior member more distal; null = without noticeable disjunction): pair (ft) slightly ' on I, null on II, slightly " on III, IV; (tc) strongly ' on I, II, weakly ' on III, weakly " on IV; (it) ' on I, II, almost null on III; (p) null on all legs; (u) null on I–III, " on IV; (a) strongly ' on I, weakly ' or null on II, null to strongly " on III, IV; (pl) strongly ' on I–IV; (pv) strongly " on I–IV; (m) strongly " on I. See Remark 16 for variation in disjunctions and Remark 17 for setal pair (m).

Solenidial formulas: genua (3-1-1-1); tibiae (1-1-1-1); tarsi (3-2-0-0). Solenidia of tarsus I and all genua long, finely tapered (‘piliform’ in terminology of Grandjean 1935b), similar in length to most leg setae. Solenidia of tibia and tarsus II distally tapered, but not finely so (‘ceratiform’). Tibia I solenidion φ longest ( Fig. 16D View FIGURE 16. A – G ), flagellate (‘tactile’), about 2/3 length of leg I. Seta d and respective solenidia with various relationships on genua and tibiae ( Figs 16 View FIGURE 16. A – G , 17 View FIGURE 17. A – C ): seta d of genu I immediately adaxial to σ3, coupled in partially merged alveoli, minute (ca. 30–35 Μm), finely attenuate ( Fig. 12D View FIGURE 12. A – F ); d present but distantly proximal to solenidion on genua II–IV; d of tibia I similar to that of genu, closely coupled adaxial to flagellate φ ( Figs 12E View FIGURE 12. A – F , 16D View FIGURE 16. A – G ); d of tibia II well posterior to φ; d of tibiae III and IV closely coupled to φ but proximal to solenidion and in separate alveolus ( Fig. 17A, C View FIGURE 17. A – C ). Solenidia ω1 and ω3 of tarsus I inserted near dorsal midline, ω1 loosely grouped with famulus and seta ft" in basal quarter and ω3 located at about one-third segment length; ω2 with unusual distal position near level of iteral setae, almost ventral on abaxial face of segment.

Ontogeny ( Figs 18–20 View FIGURE 18. A – K View FIGURE 19. A – E View FIGURE 20. A – I ). Facies, size. All juvenile instars with general appearance of adult, including almost vertically oriented prodorsum, similar proportions of body regions, and presence of extremely long notogastral setae having proportions mostly similar to those of adult ( Fig. 20A–E View FIGURE 20. A – I ). Differ from adult in being mostly pale, with soft cuticle covered in fine granules; sclerotization and pigmentation more localized and more weakly developed than in adult, but still with fine pores. Body length (n = 1; not including setae or chelicerae) of larva 335 µm, protonymph 560 µm, tritonymph 900 µm (deutonymph not measured).

Prodorsum. Aspis pale, sclerotization hardly discernable in early instars, gradually becoming more noticeable and lightly pigmented in deuto- and tritonymph (cf. Fig. 20A, C, E View FIGURE 20. A – I ). Structured as in adult, except vertical occipital region gradually decreasing in degree of sclerotization from top, and without nuchal constriction ( Fig. 19A, C View FIGURE 19. A – E ). Without lateral carina ca2; sclerotization in region below ca1 hardly discernable, except for strut (st = ‘lateral nervure’) ending in strong condyle pK ( Fig. 20E View FIGURE 20. A – I , insert). Eyes as in adult except pigmentation not observed in lateral eyes (possibly lost in specimen preparation). Prodorsal setae generally similar in form and distribution to those of adult.

Gastronotic region. Simple in structure, without general sclerotization or transverse scissures; noticeable sclerotization limited to tubercles at base of individual setae ( Fig. 19A–C View FIGURE 19. A – E ); in nymphs only setae c3 and cp on same sclerite (not examined in larva). Soft cuticle expansive and finely granulate. Cuticular disks well delineated: in tritonymph similar in size and distribution to those of adult; not studied in other instars, except posterior two large disks present in larva with same relative position as in adult. Distribution and form of setae generally similar to those of adult, except f1, h2, h3, p2 with more normal positions relative to surrounding setae (not laterally or anteriorly displaced; cf. Figs 2B View FIGURE 2. A – E , 3A View FIGURE 3. A – D ); seta e1 proportionally longer in larva ( Fig. 20A View FIGURE 20. A – I ) than adult (2 times vs. 1.6 times body length, respectively). Setae e1, e2, f1, f2, h1, h2 apparently erectile (held horizontally in larva but erect in studied nymphs; cf. Fig 20A, E View FIGURE 20. A – I ); tritonymph with muscles attaching to tubercles of presumed erectile setae in same pattern as in adults ( Fig. 20D View FIGURE 20. A – I ; see Discussion). Files of sclerotized tendon insertions absent.

Coxisternal region. Incompletely studied. Larva ( Fig. 18A View FIGURE 18. A – K ) with weakly defined epimeral plates I–III similar in form to those of adult: epimere I with wide separation between paired plates, epimere II with narrow separation, epimere III without clear separation. Vestige of leg IV (t.e.) present posterior to epimere III, in form of dome-like swelling (see Remark 12). Coxisternal setation (I to III) 3-1-2; seta 1c modified as scale covering Claparède’s organ; 1a and 3a shortest, 3b longest; most with noticeable barbs, those of 3a minute. Tritonymph ( Fig. 19E View FIGURE 19. A – E ) with epimeres structured as in adult but more weakly sclerotized; setation as in adult (3-1-3-4). Supracoxal region as in adult, except seta eI proportionally larger in larva ( Fig. 18B View FIGURE 18. A – K ); spine of epimere 2 present in tritonymph (sp2; Fig. 19D View FIGURE 19. A – E ; not studied in other instars).

Anogenital region. Ontogeny of genital papillae normal; larva without features in presumptive genital region; protonymph with single pair of genital setae on valves; tritonymph ( Fig. 19E View FIGURE 19. A – E ) with seven pairs, three in lateral row, four in medial row (posterior two absent); not examined in deutonymph. Larva ( Fig. 18A View FIGURE 18. A – K ) with four pairs of pseudanal setae: p2–p4 similar to epimeral setae in size but with fewer barbs, p4 shortest; p1 large, diverging distally, longer than pseudanal valves; seta p4 (inguinal seta) lost in protonymph. Larva without inguinal seta of h - row; h3 well formed. Cupule ih close to pseudanal valve in larva. Anal region of tritonymph similar to adult except for lack of noticeable sclerotization; peranal segment fully formed as well-delineated paraproctal valves; with small seta pa and small preanal and postanal apodemes extending inward from ends of peranal valves and with similar attached muscles.

Gnathosoma. Subcapitulum stenarthric in all juvenile instars; seta n of gena added in deuto- or tritonymph; adoral seta or3 added in protonymph. Palp seta inf added in deuto- or tritonymph; setation of other segments similar in all post-larval instars, except in protonymph (and probably larva) terminal eupathidia ul', su not fused as far distad as in adult. Chelicera as in adult except for generally lesser sclerotization.

Legs. Pretarsi of all legs monodactylous in larva and protonymph ( Figs 18 View FIGURE 18. A – K , 20G, I View FIGURE 20. A – I ), tridactylous in tritonymph ( Fig. 20H View FIGURE 20. A – I ), not recorded for deutonymph (see Remark 13). Setal ontogeny (unknown for deutonymph) given in Table 1. Larva with femur II seta bx' present (see Remark 21); famulus I with single barb. Genu ontogeny unusual (see Remarks 23–25): seta d absent from genu I of larva ( Fig. 18D View FIGURE 18. A – K ), forming as minute seta in protonymph ( Fig. 18J View FIGURE 18. A – K ), but distant from any solenidion until formation of σ 3 in deuto- or tritonymph; d of genua II and III minute in larva (Fig, 18F), becoming normal, barbed in protonymph ( Fig. 18K View FIGURE 18. A – K ) but proportionally smaller than in adult, reaching full adult proportion by tritonymph. Only proral setae (p) eupathidial in larva; s becoming eupathidial in protonymph; m" and iteral pair (it) normal in protonymph, becoming eupathidial in deuto- or tritonymph. Leg IV of protonymph ( Fig. 20I View FIGURE 20. A – I ) with lyrifissure absent (otherwise present on all tarsi), tibia with v" present, tarsus with typical set of seven setae: (p), (u), (pv) and ft"; other segments glabrous (see Remark 22). On leg I, solenidion ω2 of tarsus appearing in protonymph at same distal location as in adult; genu solenidion σ3 forming in deuto- or tritonymph, coupled to seta d. Observed variations all on leg II of tritonymph (n = 3 specimens): (1) seta l" absent unilaterally from tibia of one specimen; (2) famulus proximal to setae (ft) in one specimen.

Material examined. Type series. Holotype: adult female, deposited in NZAC; New Zealand, North Island, Waikato District, nr. Limestone Downs, ~ 37°27'S, 174°46'E (Waikato Wind Farm, C-block); C.H. Watts, col., 28- I-2010, ex: pitfall trap on floor of native forest. Paratypes: 51 adults with same collection data as holotype except dates 21-XII-2009 through 28-I-2010 (13 deposited in NZAC, four in ANIC, four in CNC, 15 in CUMNH, 15 in RAN). Preserved in alcohol, except 10 paratypes dissected on slides (in RAN).

Other studied material. Northland Region. Four adults (in NZAC) from Te Paki Ecological District; Radar Bush, ~ 9.5km, SE of Cape Reinga, ca. 34°28'S, 172°46'E; O. Ball, col., IX-2006 to III-2007, ex: pitfall traps in native shrubland. Three adults (in FM), one tritonymph (partly studied, lost), one deutonymph (lost), one protonymph and one larva (partly studied, lost) from Waipoua Forest (Toronui Track), 150 m a.s.l.; A. Newton and M. Thayer, col., 13-IV-1980, ex: decaying nikau palm leaf bases and litter. One adult (in CNC) from Waipoua Kauri Forest; L. Masner, col., 12-XII-1983, ex: sweeping low vegetation in kauri forest. Auckland Region. Twentysix adults (21 in NZAC, five in RAN) from vicinity of Laingholm, ~ 36°57'S, 174°38'E; J.T. Pusateri col., dates ranging from 19-V-2007 to 23-I-2008, ex: pitfall traps in semi-native forest. One adult from Huapai Scientific Reserve; 6-XI-2009, S.E. Thorpe, col.; ex: leaf litter in native forest. Waikato Region. Three tritonymphs from type locality (one in CUMNH, two in RAN); 28-I-2010. Fourteen adults from Te Akau, Waikato Wind Farm H-block (11 in NZAC, three in RAN), ~ 37°40'S, 174°50'E; C.H. Watts, col., 21-VII-09 and 13-I-2010, ex: pitfall traps in native forest.

Etymology. The genitive species name honors the memory of Dutch soil biologist Marie Hammer (1907– 2002). Her pioneering studies greatly expanded the geographic and taxonomic horizons of our knowledge of oribatid mites, especially those of the southern hemisphere ( Balogh 1985). In particular, her three large publications on New Zealand oribatid mites ( Hammer 1966, 1967, 1968) provide a firm foundation for continuing studies of this interesting fauna.