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Research Article
Two new Oribatid mites from Costa Rica, Mixacarus turialbaiensis sp. n. and Paulianacarus costaricensis sp. n. (Acari, Oribatida, Lohmanniidae)
expand article infoNestor Fernandez§, Pieter Theron§, Sergio Leiva|, Louwrens Tiedt§
‡ Misiones National University, Posadas Misiones, Argentina
§ North-West University, Potchefstroom, South Africa
| Experimental Rural Agency, La Rioja, Argentina
Open Access

Abstract

In this paper we describe two new species belonging to the family Lohmanniidae: Mixacarus turialbaiensis sp. n. and Paulianacarus costaricensis sp. n. from Costa Rica.

Keywords

Acari, Oribatida, Lohmanniidae, Costa Rica, Mixacarus turialbaiensis sp. n., Paulianacarus costaricensis sp. n.

Introduction

Approximately three years ago, the authors commenced the study of materials housed at the Museum d’Histoire Naturelles de Genève (MHNG), which was collected from the Turrialba forest in Costa Rica. In this initial paper, we describe two new species belonging to genera Mixacarus and Paulianacarus of the family Lohmanniidae. The taxonomy of the first species, Mixacarus turialbaiensis sp. n., was problematic as taxonomically important characters of related species were not adequately described in most prior studies. For the second species, Paulianacarus costaricensis sp. n., the situation is similar, but with seemingly misinterpreted original descriptions an aggravating factor.

Material and methods

Specimens studied by means of light microscopy were macerated in lactic acid, and observed in the same medium using the open-mount technique (cavity slide and cover slip) as described by Grandjean (1949), Krantz and Walter (2009). Drawings were made using a Zeizz GFL (Germany) compound microscope equipped with a drawing tube. Specimens preserved in ethanol, studied under Scanning Electron Microscope (SEM), were carefully rinsed by sucking them several times into a Pasteur pipette, after which they were transferred to buffered glutaraldehyde (2,5%) in Sörensen phosphate buffer: pH 7,4; 0,1 m for two hours. After postfixation for 2hr. in buffered 2% OsO4 solution and being rinsed in buffer solution; all specimens were dehydrated in a series of graded ethanol and dried in a critical point apparatus. After mounting on Al-stubs with double sided sticky tape, specimens were gold coated in a sputter apparatus (Alberti and Fernandez 1988, 1990a, 1990b; Alberti et al. 1991, 1997, 2007; Fernandez et al. 1991). For SEM observations, a FEI-Quanta Feg 250 Scanning Electron Microscope; with 10 Kv and working distant (WD) variable was used.

Measurements taken: total length (tip of rostrum to posterior edge of notogaster); width (widest part of notogaster) in micrometers (μm). Setal formulae of the legs include the number of solenidia (in parentheses); tarsal setal formulae include the famulus (ε).

Morphological terminology and abbreviations

Morphological terms and abbreviations used are those developed by Grandjean (1928–1974) (cf. Travé and Vachon, 1975; Norton and Behan-Pelletier (in Krantzand Walter 2009);); Norton and Behan-Pelletier (2009); Fernandez et al. (2013a–c).

Institutions

MHNG (Muséum d‘Histoire Naturelles, Genève, Switzerland).

New taxa descriptions

Family Lohmanniidae Berlese, 1916

Genus Mixacarus Balogh, 1958

Mixacarus turialbaiensis sp. n.

Figs 1–8, 9–11, 12–15, 16–18, 19–23, 24–28; Table 1

Etymology

The specific epithet is dedicated to the Turrialba forest of Costa Rica, where the specimens were collected.

Mixacarus turrialbai sp. n.: setae and solenidia.

Femur Genu Tibia Tarsus Claw
Leg I
setae l”,d,v l”,d l”,v (p),(u),(a),σ,(it),(tc),(ft),(pv),e 1
solenidia σ, σ φ ω1 , ω2
Leg II
setae la,lp,vb,v d,l”, d,l”,v (p),(u),(a),σ,(tc),(ft),(pv) 1
solenidia σ φ ω
Leg III
setae l’,v d,l’,v d,l’,v (p),(u),(a),σ,(tc),(ft),(pv) 1
solenidia σ φ
Leg IV
setae d,l’,v d,l d,l’v (p),(u),(a),σ,(tc),(ft),(pv) 1
solenidia σ

Type material

Holotype. Label details: “CCR 0978 Tu 11 Costa Rica Turrialba forêt naturelle du catie alt. 560 m. Triage d’humus cote est surface nid d’Atta au pied de Castilla elastica 1.IX. 1978. LEG P.WERNER 10.140744, alt. 120 m” conserved in 70% ethanol, deposited in MHNG.

Paratypes. same data, 2 ♀♀ deposited in MHNG; preserved in 70% ethanol.

Diagnosis

(adult female). Setae ro inserted anteriorly on transversal cuticular ridge; le, in setae erect; setae ro, le, in more or less similar length. Several ribbon-like bands near ro, le, exa, exp setae; sensillus pectinate (6–9 pectines); clearly visible superior cornea of naso (CSO).

Sixteen pairs of setae: c1, c2, c3, d1, d2, d3, e1, e2, f1, f2, h1 , h2, h3, p1, p2, p3; eight transversal bands: S2, S3, S4; S5, S6, S7, S8, S9. Bands S2, S6, S8, S9 cross medial notogastral plane transversally; S3, S4, S5, S7 not crossing medial notogastral plane. Five pairs of lyrifissures: ia, ip, ips, im, ih.

Adoral setae: or1 spoon-shaped, largest; or2 elongate, tip beak-shaped; or3 large, rounded apex. Epimeral setal formula 3–1–3–(3–4), epimere IV with either three or four pairs of setae; genital plate undivided, rounded elevated central zone bearing nine or ten pairs of setae; six or seven pairs of simple setae aligned paraxially,

Description

(female). Measurements. 525 (485–560) × 233 (224–245) (ten specimens measured).

Shape. Oval (Figures 1, 9, 10, 12).

Colour. Yellow to light brown; slightly shiny when observed in reflected light.

Cerotegument. Almost nonexistent; or disappeared during extensive period of conservation in ethanol.

Integument. Smooth: prodorsum, notogaster, ventral region (Figures 1, 12); depressed areas of variable size with polyhedral microsculpture (Figure 7): sb (ribbon-like prodorsal bands) (Figure 1); lateral prodorsal zone (Figures 5, 6); zone of l.d (Figures 8, 13, 14); notogastral band S2, S3, S4, S5, S6, S7, S8, S9 (Figures 1, 2, 9, 11, 12, 19); notogastral marginal zone (Figures 12, 19); subcapitular zone around setae h, m1, m2, a (Figure 20); epimeral zone (Figures 16, 17, 21, 23); anogenital zone (Figure 18); ventral zone external to anogenital zone (Figures 16, 18); legs (Figures 24–28).

Setation (legs not included). Two types: simple, smooth: genital, anal (Figures 1, 2, 18); simple, barbed: prodorsum, notogaster, epimeral, subcapitular (Figures 3, 4, 5, 14, 21, 23). Barbs are small, difficult to observe.

Prodorsum. Shape: triangular, rounded apex in dorsal view (Figures 1, 9); triangular in lateral view (Figures 12, 14). Rostrum broadly rounded (Figures 1, 9); elevated chitinous ridge present on either side of prodorsal area, externally to exa, exp, le setae, derived from margins of leg depressions (Figures 12, 14); ro setae inserted anteriorly on transversal cuticular ridge, generally directing forward (Figures 1, 9, 12); le, in setae erect (Figure 12); setae ro, le, in more or less similar length. Several ribbon-like bands near ro, le, exa, exp setae, extending laterally to elevated lateral ridge (Figures 5, 6, 12, 13). Bo rounded, slightly elevated from the cuticular surface (Figure 15), laterally tilted (Figures 1, 9, 12). Sensillus pectinate (6–9 pectines) (Figures 9, 11, 12). Postbothridial transverse band sb clearly discernible, situated posterior to bo and in setae (Figures 1, 9, 11). On anterior zone near apex, in front of ro setal insertion and between cuticular elevations of l.d, CSO clearly visible (Figures 1, 12, 14).

Notogaster. Sixteen pairs of primary notogastral setae: c1, c2, c3, d1, d2, d3, e1, e2, f1, f2, h1, h2, h3, p1, p2, p3 clearly discernible (Figures 1, 9, 11, 12). Nine transversal bands: S2, S3, S4, S5, S6, S7, S8, S9 (Figures 1, 9, 11, 12); S2 crossing transverse medial notogastral plane, exceeding slightly beyond c2 setae, terminating near c3 in a large rectilinear tip (Figures 11, 12); S3 situated behind c setal alignment and in front of d setal alignment, not crossing medial notogastral plane; laterally stopping above c3, d3 setal insertion level (Figures 11, 12); S4 observed anterior to d setal alignment, not crossing medial notogastral plane, running obliquely, exceeding d1 setal insertion level, terminating in rounded end (Figures 1, 9); S4 extending to unsclerotized lateral longitudinal line (Figures 11, 12); S5 thin (Figures 1, 9), not crossing medial notogastral plane, laterally terminating before d3 setal insertion level (Figures 11, 12); S6 situated behind e1, crossing medial notogastral plane (Figures 1, 9), laterally reaching unsclerotized lateral longitudinal line (Figures 1, 9, 11, 12); S7 situated behind f1 setal insertion, not crossing medial notogastral plane, extending to unsclerotized lateral longitudinal line (Figures 1, 9, 11, 12); S8, S9 crossing medial notogastral plane and unsclerotized lateral longitudinal line (Figure 11).

Five pairs of lyrifissures present: ia, ip situated below the unsclerotized lateral longitudinal line (see Lateral region); ips situated on the adanal fold band (BPDA) (Figures 9, 10, 11); im near e2 setae and ih behind h3.

Lateral region. Prodorsal margin present on either side of cavities housing legs I-IV when retracted. Anterior notogastral zone presenting conspicuous tectum and clearly defined unsclerotized lateral longitudinal line, terminating almost posterior to level of ip lyrifissure and delimiting unpaired dorsal notaspis and pleuraspis (paired narrow lateral zones) (Figure 11). In posterior notogastral zone, when unsclerotized line does not exist, notaspis and pleuraspis not delimited (Figure 11). Each pleuraspis presenting an anterior rounded lobe between legs II and III, where lyrifissure ia is observed. Posteriorly, at level of d3 and e2 setae, well delimited edges form canopies over cavities in which legs III and IV are housed when retracted, with a protruding angle between them.

Ventral region. Anterior zone of subcapitulum more or less triangular, posterior zone ovoid. Four pairs of subcapitular setae (Figure 10) h, m1, m2, a. Characteristic adoral setae: or1 largest, spoon shaped; or2 elongate, terminating in beak-shape; or3 large, rounded apex (Figure 20).

Coxisternal region divided into two parts by ventrosejugal groove (Figures 10, 16, 17). Apodemes short and clearly visible; epimeral setal formulae 3-1-3-(3-4), epimere IV with three or four pairs of setae; all setae similarly shaped, but vary in length (Figures 21, 22, 23). Genital plate undivided, elevated central zone rounded with ten pairs of setae, sometimes with only nine pairs; (Figures 10, 16, 18); six or seven simple setae aligned paraxially, and three antiaxially. Preanal plate more or less triangular, rounded central zone.

Anal and adanal plates with four pairs of adanal and two pairs anal setae (Figures 16, 18). Band BPAD clearly visible in specimens immersed in lactic acid for lengthy period; lyrifissure ips present near margin of this band (Figure 10).

Legs. Two types of femora can be distinguished. Femora of legs I and II displaying large ventral blade (Figures 24, 25), femora of legs III and IV lacking ventral blade (Figures 26, 27).

Setal formulae I (0–3–2–2–16–1) (2–1–2); II (0–4–2–3–13–1) (1–1–1); III (2–3–2–2–13–1) (1–1–0); IV (2–3–2-3–13–1(1–0–0). See Table 1.

Figures 1–8. 

Mixacarus turialbaiensis sp. n. Adult with cerotegumental layer. SEM. 1 dorsal view 2 notogastral setae d3 3 ro setae 4 in setae 5 exa setae 6 exp setae 7 detail of cuticular microsculpture 8 polyhedral microsculpture from porose area. Abbreviations: See Material and methods. Scale bars: 1 = 100 μm; 2 = 20 μm; 3 = 10 μm; 4 = 20 μm; 5 = 5 μm; 6 = 10 μm; 7 = 2 μm; 8 = 5 μm.

Figures 9–11. 

Mixacarus turialbaiensis sp. n. Adult, optical microscopy. 9 dorsal view 10 ventral view 11 lateral view. Abbreviations: See Material and methods. Scale bars: 9, 10 = 300 μm; 11 = 200 μm.

Figures 12–15. 

Mixacarus turialbaiensis sp. n. Adult with cerotegumental layer. SEM. 12 lateral view 13 microsculpture lateral zone 14 anterior prodorsal zone 15 bothridial zone. Abbreviations: See Material and methods. Scale bars: 12 = 100 μm; 13 = 20 μm., 14 μm = 20 μm; 15 = 10 μm.

Figures 16–18. 

Mixacarus turialbaiensis sp. n. Adult with cerotegumental layer. SEM. 16 ventral zone 17 Epimeral zone 18 anogenital region. Abbreviations: See Material and methods. Scale bars: 16=100 μm; 17, 18= 50 μm.

Figures 19–23. 

Mixacarus turialbaiensis sp. n. Adult with cerotegumental layer. SEM. 19 lateral notogastral zone 20 adoral setae 21 epimeral zone, 2a setae 22 epimeral zone, 3a setae 23 epimeral zone, 3b setae. Abbreviations: See Material and methods. Scale bars: 19 = 20 μm; 20 = 10 μm; 21, 22 = 2 μm; 23 = 5 μm.

Figures 24–28. 

Mixacarus turialbaiensis sp. n. Adult with cerotegumental layer. SEM. 24 leg I antiaxial view 25 leg II antiaxial view 26 leg IV antiaxial view 27 leg III antiaxial view 28 tarsus I, famulus zone. Abbreviations: See Material and methods. Scale bar: 23 = 50 μm; 24 = 20 μm; 25 = 20 μm; 26 = 20 μm; 27 = 20 μm; 28 = 5 μm.

Genus Paulianacarus Balogh, 1960

Paulianacarus costaricensis sp. n.

Figs 29–30, 31–32, 33–35, 36–41, 42–47, 48–51, 52–55; Table 2

Etymology

The specific epithet is dedicated to Costa Rica costaricensis (Latin = from Costa Rica), the country where the specimens were collected.

Paulianacarus costaricensis sp. n.: setae and solenidia.

Femur Genu Tibia Tarsus Claw
Leg I
setae (l),d,v (l),d (l),v (p),(u),(a),σ,(it),(tc),(ft),(pv), ε 1
solenidia σ’, σ’’ φ ω1 , ω2
Leg II
setae d,la”lp”,l’,vb, v d,l”,xt d,(l),v,xt (p),(u),(a),σ,(tc),(ft),(pv) 1
solenidia σ φ ω
Leg III
setae l’,v d,l’,v d,l’,v (p),(u),(a),σ,(tc),(ft),(pv) 1
solenidia σ φ
Leg IV
setae d,l’,v d l’,v d,l (p),(u),(a),σ,(tc),(ft),(pv) 1
solenidia σ

Type material

Holotype. Label details: “♀ CR 0978 Tu 18a. Costa Rica Turrialba forêt naturelle du catie alt. 560 m. Racines d’epiphytes sur branche tombe 1 mois avant. 24. IX. 1978 LEG P.WERNER”. MHNG, preserved in 70% ethanol. Paratypes: same data and locality 2 ♀♀. MHNG, preserved in 70% ethanol.

Diagnosis

Prodorsum. Triangular to slightly polyhedral; rostrum rectilinear; ro setae inserted far from rostrum; si pectinate (5-8 pectines). Notogaster. Sixteen pairs of setae: c1, c2, c3, d1, d2, d3, e1, e2, f1, f2, h1, h2, h3, p1, p2, p3. Cuticular surface with nine elevated transversal thickenings; 1-5 complete, crossing medial notogastral plane; 6-9 not crossing medial notogastral plane; elevated transversal thickening, nine transverse bands present; 3, 4, 7 smooth, others with promontories.

Description

(Adult female). Measurements. Length 960 (1100–890) ×535 (526–540) (three specimens).

Shape. Elongate ovoid (Figures 29, 30, 31, 32).

Colour. Dark to light brown; slightly shiny when observed in reflected light.

Cerotegument. Nonexistent.

Integument. Complex microsculpture. Rounded promontories (Figures 29, 30, 38, 40, 41); elevated transversal thickening (tr.e.t) (Figures 29, 30, 31, 33); polyhedral microsculpture (0.7–0.8) (Figures 42, 43, 44, 45, 46 indicated by arrow) in depressed areas (Figure 46, under large magnification), this type of microsculpture observed on cuticular structures on various areas of body and legs (Figures 42, 43, 44, 45 indicated by u), principally on transverse bands.

Setation (legs not included). Two types: simple, smooth: prodorsum: le, ro length 163 (140–180); exp, exa length 153 (140–160); notogaster: 167 (140–180); epimeral (40–53); genital 53 (40–52); aggenital 59.5 (45–72); anal 74 (63–81); adanal 119 (100–136); subcapitular (h, m) 51.5 (50–54); a 39.5 (36–41) (Figures 49, 50); simple barbate: in setae 142 (130–150) (Figures 38, 41).

Prodorsum. Triangular to slightly polyhedral in dorsal view (Figures 30, 31); triangular in lateral view (Figures 29, 34).

Rostrum rectilinear (Figures 33–35). Prodorsal margin dentate (Figures 34, 39). Depression housing legs l.d (for legs I and II) (Figure 36) clearly observed as laterally situated concave arc-shaped zone; ro setae inserted far from rostrum, in some instances situated slightly anterior to tr.l.t (transversal elevated thickening) (Figures 29, 30, 31); margins of l.d formed by elevated cuticular thickening (indicated by arrows ¿ Figures 33, 34). Medial prodorsal zone, situated between sb (transverse postbothridial band), transversal linear thickening (tr.l.t) and setae exp, exa, le, with prominent elevated round promontories (Figure 33); smooth polyhedral area situated between l.d elevated margins, tr.l.t and rostrum; with an interior rectangular zone (Figures 33, 34 indicated by s); le setal insertion anterior to tr.l.t (Figure 33), situated near l.d elevated margin (Figure 33, indicated by arrows ¿); bo cup-shaped, dorsally open (Figures 36, 38); si pectinate, with 5–8 large pectines (Figures 33, 38, 41); in setae inserted at level of bo, situated internally to bo and in front of sb (Figures 30, 31); exa and exp well visible, situated marginally on a smooth area (Figure 43); sb clearly discernible, situated behind in setal insertions (Figures 30, 31).

Frontal view. Rostrum rectilinear, situated in medial zone between l.d elevated cuticular thickening (Figures 33, 34, indicated by arrows ¿); prodorsal border at first concave and becoming convex towards the posterior; in boundary zone between concave and convex, a series of dentate projections (Figures 34, 39). Anterior subcapitular zone (Figures 32, 34, 35), adoral setae clearly visible: or3 sigmoid; or2 very complex, leaf-shaped in ventral view (Figure 35), in lateral view (Figure 46) resembling a bird’s head and beak; or1 very complex, resembling a leaf with edges eaten by a caterpillar (Figures 35, 46).

Notogaster. Sixteen pairs of notogastral setae: c1, c2, c3, d1, d2, d3, e1, e2, f1, f2, h1, h2, h3, p1, p2, p3, clearly discernible and directing backward (Figures 29, 30, 31).

Cuticular surface with elevated transversal thickenings (tr.e.t); tr.e.t.1 with rounded promontories, situated in front of c setal alignment, externally to c1 setae; smooth zone between c1 setal pair (Figure 29). Transverse bands: S2 clearly visible (Figures 29, 30, 31), situated behind c setal alignment. Thickenings tr.e.t.2 and tr.e.t.3 between c and d setal alignment; tr.e.t.2 with rounded promontories, close to c alignment; tr.e.t.3 smoothly surfaced, close to d setal alignment; longitudinal furrow running between d1 setal insertions. Transverse band S3 observed between tr.e.t.2 and tr.e.t.3 (Figures 29, 30, 31). S4 situated posterior to d setal alignment. Transverse thickenings tr.e.t.4 and tr.e.t.5 between d and e setal alignment; tr.e.t.4 smooth, with deep central furrow (Figure 30, indicated by¿) running along tr.e.t4; tr.e.t5 with rounded promontories. S5 situated between tr.e.t4 and tr.e.t5. U-shaped S6, with rounded promontories, observed between e and f setal alignment, situated on either side of tr.e.t.6. Posterior to f setal alignment, in oblique position, with central zone not corssing longitudinal medial plane, smooth tr.e.t. 7. S7 situated behind tr.e.t.7; tr.e.t8 in oblique position, not crossing medial longitudinal plane, surface with rounded promontories. S8 behind tr.e.t8; tr.e.t.9 in oblique position, not crossing medial longitudinal plane, smooth; S9 situated behind tr.e.t. A series of more or less triangular posterior promontories (p.p) observed in posterior medial zone (Figures 29, 30, 31). Only lyrifissure ia discernible anteriorly on frontal lobe of pleuraspis.

Lateral region. Bothridium (bo): margin elevated, ovoid, clearly visible (Figures 36, 38); sb depressed zone situated close to and behind bo and in (Figures 30, 31, 38); polyhedral microsculpture (Figure 45); small depressed marginal zone situated above longitudinal unsclerotized line (Figure 37). Rounded promontories easily visible (Figures 36, 38, 40). Prodorsal margin presenting conspicuous depression l.d (Figure 36), housing legs I–IV during leg folding. Polyhedral lobe with lyrifissure ia and rounded promontories (Figure 37) on anterior zone of pleuraspis. Conspicuous tectum on anterior notogastral zone. Unsclerotized longitudinal line easily discernible, exceeding level of f2 setal insertions and clearly delimiting notaspis and pleuraspis (Figure 36).

Ventral region. Four pairs of subcapitular setae (Figure 49); setae h, m2 and a clearly visible (more or less similar length); setae m1 situated marginally and hardly discernible (Figures 32, 37, 49). Infracapitulum: complex microsculpture. Triangular microsculpture with rounded promontories in central zone between setae h, surrounded by smooth zone. Several areas with polyhedral microsculpture (Figure 49, indicated by ¿).

Epimeral zone: only epimere I with rounded promontories, easily observed in insertion zones of setae 1a, 1b, 1c (Figure 47). Other epimeres smooth; epimeral setae variable on epimeres 3, 4 with formulae: 3–1–[3 (2)]–[4 (3)] (Figure 32 indicated by l). All setae similarly shaped (Figure 47). Genital plate undivided with nine to ten pairs of setae (Figures 32, 49); six or seven aligned paraxially and three or four antiaxially. Preanal plate typically shaped, characteristic of the genus (Figures 4748). Anal plate fused with adanal, delimiting single plate with six pairs of setae (Figures 47, 48). BPAD clearly visible after lengthy soaking in lactic acid (Figure 32); lyrifissures ia, ip, ih, ip observed (Figures 32, 37).

Legs. Setal formulae I (0–4–3–3–16–1) (2–1–2); II (0–6–3–5–13–1 (1–1–1); III (2–2–3–3–13–1 (1–1–0); IV (2–3–3–2–13–1(1–0–0). See Table 2 and Figures 52–55.

Remarks

Polyhedral microsculpture observed in several areas. Porous areas are very difficult to observe, as in most cases they are situated in the same zone as the microsculpture. On legs this microsculpture is present on all segments.

Figures 29–30. 

Paulianacarus costaricensis sp. n. Adult with cerotegumental layer. SEM. 29 lateral inclined view 30 dorsal with slight lateral tilt. Abbreviations: See Material and methods. Scale bars: 29, 30 = 200 μm.

Figures 31–32. 

Paulianacarus costaricensis sp. n. Adult, optical microscopy. 31 dorsal view 32 ventral view. Abbreviations: See Material and methods. Scale bar: 31, 32 = 400 μm.

Figures 33–35. 

Paulianacarus costaricensis sp. n. Adult with cerotegumental layer. SEM. 33 frontal view 34 prodorsum, laterally inclined 35 apical zone, infracapitulum. Abbreviations: See Material and methods. Scale bars: 33 = 100 μm; 34 = 50 μm; 35 = 20 μm.

Figures 36–41. 

Paulianacarus costaricensis sp. n. Adult with cerotegumental layer. SEM. 36 lateral view 37 anterior lateral notogastral zone 38 bothridial zone 39 prodorsal marginal zone 40 promontories 41 lateral view, sensillus zone. Abbreviations: See Material and methods. Scale bars: 36 = 200 μm; 37 = 20 μm; 38 = 50 μm; 39 = 10 μm; 40 = 10 μm; 41 = 50 μm.

Figures 42–47. 

Paulianacarus costaricensis sp. n. Adult with cerotegumental layer. SEM. 42 lateral view, notogastral promontories 43 Frontal prodorsum detail promontories 44 epimeral posterior zone 45 notogastral setae and microsculpture, “porose area” 46 depressed area microsculpture, notogastral zone 47 adoral setae, frontal view. Abbreviations: See Material and methods. Scale bars: 42 = 20 μm; 43 = 50 μm; 44 = 20 μm; 45 = 10 μm; 46 = 2 μm; 47 = 10 μm.

Figures 48–51. 

Paulianacarus costaricensis sp. n. Adult with cerotegumental layer. SEM. 48 ventral view 49 anogenital region 50 infracapitulum 51 apical infracapitular zone. Abbreviations: See Material and methods. Scale bars: 48 = 200 μm; 49 = 100 μm; 50 = 50μm; 51 = 20μm.

Figures 52–55. 

Paulianacarus costaricensis sp. n. Adult with cerotegumental layer. SEM. 52 leg I, antiaxial 53 leg III, antiaxial 54 leg II, antiaxial 55 leg IV, antiaxial. Abbreviations: See Material and methods. Scale bars: 52 = 20 μm; 53 = 50 μm; 54 = 50 μm; 55 = 50 μm.

Discussion

The genus Mixacarus was proposed by Balogh (1958); but later Balogh and Balogh (1987) proposed another new genus, Phyllolohmannia. Currently Mixacarus is divided into two sub-genera, Mixacarus and Phyllolohmannia, and includes 22 species (Subias 2017).

A comparison between Mixacarus turialbaiensis sp. n. and Mixacarus exilis Aoki 1970 is quite complex, as some aspects of the initial description is detailed and others are deficient, for example: lateral observations are ignored and for the ventral region, drawings are referred to, but in a preceding paper by Wallwork 1962. Other problematic aspects include the absence of any reference to the porose areas of M. exilis. Making use of different study methods and technology, the authors were able to observe structures evidently not previously observed, such as the particular microsculpture in depressed areas (Figure 7), and transversal bands on notogaster (Figures 2, 5, 6, 13, 14, 16, 17, 19, 21, 23). Porose areas (Figure 8) were discernible on transversal notogastral band in the zone of this microsculpture.

Mixacarus turialbaiensis sp. n. is close to Mixacarus exilis Aoki 1970, but is differentiated by the depressed areas with particular microsculpture; all prodorsal setae have similar characteristics and length; ribbon-like bands on prodorsum distributed very differently; notogastral setae slightly barbate; nine transversal bands; epimeres with large number of depressed areas; variable chaetotaxy in genital and epimeral zone.

Paulianacarus was proposed by Balogh (1960) from Madagascar. Subias (2004) considered Millotacarus to be a subgenus of Paulianacarus. At present there are 15 species allocated to Paulianacarus and Millotacarus. The taxonomy of these genera are complex, and considering one a subgenus of the other is complicated by the lack of a detailed comparative study of type materials. Several authors have expressed their opinions (Mahunka 1985; Coetzee 2001; Chen et al. 2012, Fernandez et al. 2014), and these considerations highlight the incongruences in the descriptions, indicating that some do not consider that these are different genera, or do not consider one to be a subgenus of the other, while other researchers accept both subgenera. An analysis of these opinions is not repeated here in order to avoid redundancy. The only way to solve the problem is the study and comparison of type material, which was not possible in this instance.

The new species Paulianacarus costaricensis sp. n. was described using optical and SEM microscopy. These techniques allowed us to understand some of the complex structures also observed in Paulianacarus rugosus Balogh, 1961, a species close to the newly described species.

P. costaricensis displays the following characters: elevated transversal thickening (tr.e.t) with transverse bands: 1) some cross the transverse medial notogastral plane, others do not; 2) some are rectilinear, others oblique; 3) some present superficial rounded protuberances, others are smooth; 4) smooth thickenings either with complete furrow running the entire length, or partial furrow; 5) tr.e.t are associated with transversal furrows (S); 6) transversal furrows are related to one or both sides of the elevated transversal thickenings. Variable number and disposition of genital and epimeral setae, difficulty in observing lyrifissures. These are only some of the characteristics of this species, but they emphasize the need for detailed studies.

P. rugosus Balogh 1961 is close to P. costaricensis, but is differentiated by the presence of prodorsal transversal band; barbate in setae; elevated transversal thickening, transverse medial notogastral plane tr.e.t 1, 2, 3, 4, 5; tr.e.t 6, 7, 8, 9 not crossing medial notogastral plane; elevated transversal thickening with rounded protuberances: tr.e.t 1, 2 ,5, 6, 8, 9; with smooth surface: tr.e.t 3, 4, 7; epimeral chaetotaxy: (3–1–[3 (2)]–[4 (3)]); porose area rounded, very difficult to observe as it is situated in polyhedral microsculpture zone; genital setae variable with 9–10 pairs, of which 6–7 are aligned paraxially and 3-4 antiaxially.

Acknowledgements

Our gratitude is expressed towards Peter Schwendinger of NHNG, Switzerland, for valuable assistance in obtaining study material. This work is based on research supported in part by the National Research Foundation of South Africa (UID) 85288. Any opinion, findings and conclusions or recommendations expressed in the material are those of the authors and therefore the NRF does not accept any liability in regard thereto.

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