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Research Article
The oribatid mite genus Macrogena (Acari, Oribatida, Ceratozetidae), with description of two new species from New Zealand
expand article infoSergey Ermilov, Maria Minor§
‡ Tyumen State University, Tyumen, Russia
§ Massey University, Palmerston North, New Zealand
Open Access

Abstract

Two new species of oribatid mites of the genus Macrogena (Oribatida, Ceratozetidae) are described from alpine soils of the South Island of New Zealand. Macrogena brevisensilla sp. n. and M. abbreviata sp. n. differ from all species of this genus by the tridactylous legs and by the comparatively short interlamellar setae, respectively. New generic diagnosis and an identification key to the known species of Macrogena are provided.

Keywords

Oribatid mites, Macrogena, new species, generic diagnosis, key, New Zealand

Introduction

Macrogena is an oribatid mite genus of the family Ceratozetidae (Acari, Oribatida) which was proposed by Wallwork (1966) with Macrogena monodactyla Wallwork, 1966 as type species. At present, three species are known1: M. crassa Hammer, 1967, M. rudentiger Hammer, 1967 (both from New Zealand) and M. monodactyla Wallwork, 1966 (from the Antarctic region).

During the recent study of oribatid mite fauna of the high alpine zone of several mountain ranges in New Zealand (Central Otago, South Island), we discovered two new species of the genus Macrogena; both species were common and abundant in the collected material. Additionally, we propose a new generic diagnosis for Macrogena, and provide an identification key for all known species of this genus.

Materials and methods

The collection locality and habitat for each new species are given in the respective “Material examined” sections.

Specimens were mounted in lactic acid on temporary cavity slides for measurement and illustration. The body length was measured in lateral view, from the tip of the rostrum to the posterior edge of the ventral plate. Notogastral width refers to the maximum width in dorsal aspect. Lengths of body setae were measured in lateral aspect. All body measurements are presented in micrometers. Formulas for leg setation are given in parentheses according to the sequence trochanter–femur–genu–tibia–tarsus (famulus included). Formulas for leg solenidia are given in square brackets according to the sequence genu–tibia–tarsus. General terminology used in this paper follows that of Grandjean (summarized by Norton and Behan-Pelletier 2009). Drawings were made with a drawing tube using a Carl Zeiss transmission light microscope “Axioskop-2 Plus”. Images were obtained with an AxioCam ICc3 camera using a Carl Zeiss transmission light microscope “Axio Lab.A1”.

Taxonomy

Macrogena Wallwork, 1966

Type species

Macrogena monodactyla Wallwork, 1966

Diagnosis

(partially based on data from Wallwork 1966; Hammer 1967). Ceratozetidae with rostrum with medial rectangular ledge formed by two lateral incisions; rostral setae inserted dorsally or dorso-laterally on prodorsum; lamellar and interlamellar setae strong, straight; bothridial setae fusiform or globular; lamellae large, with short cusps, connected by translamella; tutoria and genal teeth long, reach the level of insertions of rostral setae; dorsophragmata fused medially; notogaster with three or four pairs of porose areas; ten pairs of short and thin notogastral setae; five pairs of genital, one pair of aggenital, two pair of anal, and three pairs of adanal setae; legs mono- or tridactylous.

Macrogena brevisensilla sp. n.

Figs 1–4, 5–9, 10–13, 14–22

Diagnosis

Body size: 315–332 × 182–199. Lamellar cusps without teeth. Translamella broad. Rostral setae dilated in medio-distal parts, ciliated. Lamellar and interlamellar setae long, thickened, densely barbed. Bothridial setae globular. Tutoria broadly triangular. Four pairs of notogastral porose areas present. Notogastral setae short, thin. Epimeral setae 1c thickened, barbed. Tridactylous.

Description

Measurements. Body length: 332 (holotype: female), 315–332 (six paratypes: three females, three males); notogaster width: 182 (holotype), 182–199 (six paratypes).

Integument. Body color light brown to brown. Body surface punctate (visible under high magnification). Lamellae, epimeral region, pedotecta I and subcapitular mentum with striae.

Prodorsum. Anterior edge of medial ledge of rostrum slightly wavy, lateral incisions very narrow. Lamellae shorter than half of prodorsum. Lamellar cusps without teeth. Translamella straight, broad. Rostral setae (ro, 32–41) dilated in medio-distal parts, ciliated. Lamellar (le, 49–57) and interlamellar (in, 82–90) setae thickened, densely barbed. Lamellar setae sometimes slightly dilated medio-distally. Bothridial setae (ss, 22–26) globular, with short stalk (4–6) and longer, indistinctly barbed head (18–20). Tutoria (tu) broadly triangular distally. Exobothridial setae (ex, 4) thin, smooth.

Notogaster. Anterior margin convex medially. Pteromorphs broadly rounded laterally. Porose areas Am elongate oval. Dorsophragmata (D) of medium size. Four pairs of porose areas present, all rounded: Aa (8), A1, A2 and A3 (6). Notogastral setae thin, smooth, c (12) little longer than other nine pairs (6–8). Lyrifissures ia, im, ip, ih and ips distinct. Opisthonotal gland openings (gla) located posteriorly to im.

Gnathosoma. Subcapitulum longer than wide (86 × 61–65). Subcapitular setae h (4–6) thin, smooth; a (12–16) and m (18–20) setiform, slightly barbed. Adoral setae (or1, or2, 8–10) simple, densely barbed. Palps (53–61) with setation 0–2–1–3–9(+ω). Solenidion attached to eupathidium, both located on dorsal tubercle. Chelicerae (90–94) with two simple, barbed setae; cha (28–32) longer than chb (16–20). Trägårdh’s organ (Tg) long, tapered.

Epimeral and lateral podosomal regions. Pedotecta I (Pd I) large, concave in dorsal view. Pedotecta II (Pd II) of medium size, triangular, rounded distally in ventral view. All pedotecta scale-like in lateral view. Genal teeth (gt) elongate narrowly triangular. Apodemes 1, 2, sejugal and 3 distinctly developed. Epimeral setal formula 3–1–2–2. Epimeral setae 1c (10) thickened, barbed; other setae (4–6) thin, smooth. Custodia (cus) with long, pointed tips. Discidia (dis) triangular. Circumpedal carinae (cp) distinct.

Anogenital region. Genital (g1g5, 4–6), aggenital (ag, 4–6), anal (an1, an2, 4–6) and adanal (ad1ad3, 6–8) setae thin, smooth. Lyrifissures iad located close to anal aperture, in paraanal position. Ovipositor elongated (102–110 × 28), blades (45–49) shorter than length of distal section (beyond middle fold; 57–61). Each of three blades with four straight, smooth setae, ψ1 ≈ τ1 (32) longer than ψ2 ≈ τa ≈ τb ≈ τc (14–16). Six coronal simple setae (k, 8) present.

Legs. Tridactylous. Medial claw thicker than two laterals; all indistinctly serrate dorsally. Genua I and II, and femora II with antero-ventral tooth (t). Formulae of leg setation and solenidia: I (1–5–3–3–18) [1–2–2], II (1–5–3–4–15) [1–1–2], III (2–2–1–3–15) [1–1–0], IV (1–2–2–3–12) [0–1–0]; homology of setae and solenidia as indicated in Table 1. Famulus (ε) short, blunted. Setae l’’ on tibiae and genua I, II thick.

Leg setation and solenidia of adult Macrogena brevisensilla sp. n.

Leg Trochanter Femur Genu Tibia Tarsus
I v d, (l), bv’’, v’’ (l), v’, σ (l), v’, φ1, φ2 (ft), (tc), (it), (p), (u), (a), s, (pv), (pl), ε, ω1, ω2
II v d, (l), bv’’, v’’ (l), v’, σ (l), (v), φ (ft), (tc), (it), (p), (u), (a), s, (pv), ω1, ω2
III l’, v d, ev l’, σ l’, (v), φ (ft), (tc), (it), (p), (u), (a), s, (pv)
IV v d, ev d, l l’, (v), φ ft’’, (tc), (p), (u), (a), s, (pv)

Material examined

Holotype (female) and six paratypes (three females and three males): New Zealand, South Island, Central Otago, The Remarkables, 45°3'38"S, 168°48'43"E, 1867 m a.s.l., in the soil and debris under Raoulia sp. cushion, 19 February 2014, collected by M. Minor.

Type deposition

The holotype and two paratypes are deposited in the New Zealand National Arthropod Collection, Auckland, New Zealand; two paratypes are deposited in the collection of the Senckenberg Institution, Frankfurt, Germany; two paratypes are deposited in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.

Etymology

The specific name brevisensilla refers to the short bothridial setae (sensilla).

Remarks

Macrogena brevisensilla sp. n. differs from all species of this genus by the tridactylous legs.

Wallwork (1966) considered monodactylous legs as the generic character of Macrogena. The new species has tridactylous legs, however, all other morphological traits correspond to the other species of this genus. Thus, we included M. brevisensilla sp. n. in Macrogena, and included alternatively tridactylous legs in the revised generic diagnosis.

Figures 1–4.

Macrogena brevisensilla sp. n., adult: 1 dorsal view 2 ventral view (legs not shown) 3 lateral view of anterior part of body (leg I not shown) 4 lateral view of posterior part of body. Scale bars 100 µm (1, 2), 50 µm (3, 4).

Figures 5–9.

Macrogena brevisensilla sp. n., adult: 5 frontal view of prodorsum 6 posterior view 7 subcapitulum, ventral view 8 palp 9 chelicera. Scale bars 50 µm (5, 6), 20 µm (7–9).

Figures 10–13.

Macrogena brevisensilla sp. n., adult: 10 leg I, right, antiaxial view 11 tibia, genu, femur and trochanter of leg II, right, antiaxial view 12 genu, femur and trochanter of leg III, right, antiaxial view 13 leg IV, left, antiaxial view. Scale bar 20 µm.

Figures 14–22.

Macrogena brevisensilla sp. n., dissected adult, microscope images: 14 rostrum, dorsal view 15 medio-basal part of prodorsum and medio-anterior part of notogaster 16 notogastral porose area Aa and seta la 17 microporose in medial part of notogaster 18 right parts of subcapitular mentum and epimere I 19 rostral and lamellar setae 20 custodium and discidium 21 genital plates 22 ventral teeth on leg II (left, antiaxial view). Scale bar 20 µm.

Macrogena abbreviata sp. n.

Figs 23–25, 26–30, 31–34, 35–44

Diagnosis

Body size: 254–291 × 143–151. Lamellar cusps without teeth. Translamella of medium thickness. Rostral setae setiform, ciliated. Lamellar and interlamellar setae of medium size, thickened, barbed. Bothridial setae fusiform. Three pairs of notogastral porose areas present. Notogastral setae short, thin. Monodactylous.

Description

Measurements. Body length: 270 (holotype: female), 254–291 (six paratypes: three females, three males); notogaster width: 143 (holotype), 143–151 (six paratypes).

Integument. Body color light brown to brown. Body surface punctate (visible under high magnification). Lamellae and pedotecta I striate; epimeral region also with longitudinal striae, however it is visible only in dissected specimens.

Prodorsum. Medial ledge of rostrum truncated, lateral incisions well visible. Lamellae shorter than half of prodorsum. Lamellar cusps without teeth. Translamella straight, thickened. Rostral setae (24–28) setiform, ciliated. Lamellar (18–20) and interlamellar (32–36) setae thickened, usually indistinctly barbed (rarely with sparse, strong barbs). Bothridial setae (22–26) fusiform, with short stalk (6) and longer, indistinctly barbed head (16–20). Tutoria narrowly triangular distally, slightly rounded, sometimes pointed. Exobothridial setae (4) thin, smooth.

Notogaster. Anterior margin convex medially. Pteromorphs broadly rounded laterally. Porose areas Am elongate oval. Dorsophragmata of medium size. Three pairs of porose areas present, all rounded: Aa (6–8), A2 and A3 (4–6). Notogastral setae (12–14) thin, smooth. Lyrifissures distinct. Opisthonotal gland openings located posteriorly to im.

Gnathosoma. Subcapitulum longer than wide (65–69 × 45–53). Subcapitular setae thin, slightly barbed; m (18–20) longer than a (12–16) and h (8–10). Adoral setae (8) simple, densely barbed. Palps (45) with setation 0–2–1–3–9(+ω). Solenidion attached to eupathidium, both located on dorsal tubercle. Chelicerae (73–77) with two simple, barbed setae; cha (28) longer than chb (14–16). Trägårdh’s organ long, tapered.

Epimeral and lateral podosomal regions. Pedotecta I large, concave in dorsal view. Pedotecta II of medium size, triangular, rounded distally in ventral view. All pedotecta scale-like in lateral view. Genal teeth elongate narrowly triangular. Apodemes 1, 2, sejugal and 3 distinctly developed. Epimeral setal formula 3–1–2–2. Epimeral setae (8) thin, smooth. Custodia with long, pointed tips. Discidia triangular. Circumpedal carinae distinct.

Anogenital region. Genital (8–12), aggenital (8–12), anal (8–12) and adanal (12–14) setae thin, smooth. Lyrifissures iad located close to anal aperture, in inverse apoanal position. Ovipositor elongated (106–110 × 28), blades (45–49) shorter than length of distal section (beyond middle fold; 57–61). Each of three blades with four straight, smooth setae, ψ1 ≈ τ1 (24–28) longer than ψ2 ≈ τa ≈ τb ≈ τc (12–16). Six coronal simple setae (8) present.

Legs. Monodactylous. Claws indistinctly serrate dorsally. Femora II with antero-ventral tooth (t). Formulae of leg setation and solenidia: I (1–4–3–4–18) [1–2–2], II (1–5–3–4–15) [1–1–2], III (2–2–1–3–15) [1–1–0], IV (1–2–2–2–12) [0–1–0]; homology of setae and solenidia as indicated in Table 2. Famulus (ε) short, blunted. Setae l’’ on genua I, II thick.

Leg setation and solenidia of adult Macrogena abbreviata sp. n.

Leg Trochanter Femur Genu Tibia Tarsus
I v d, (l), bv’’ (l), v’, σ (l), (v), φ1, φ2 (ft), (tc), (it), (p), (u), (a), s, (pv), (pl), ε, ω1, ω2
II v d, (l), bv’’, v’’ (l), v’, σ (l), (v), φ (ft), (tc), (it), (p), (u), (a), s, (pv), ω1, ω2
III l’, v d, ev l’, σ l’, (v), φ (ft), (tc), (it), (p), (u), (a), s, (pv)
IV v d, ev d, l (v), φ ft’’, (tc), (p), (u), (a), s, (pv)

Material examined

Holotype (female) and six paratypes (three females and three males): New Zealand, South Island, Central Otago, Old Man’s Range, 45°19'24"S, 169°12'28"E, 1655 m a.s.l., in the bare soil with some lichen outside of Dracophyllum muscoides cushion, 17 February 2014, collected by M. Minor.

Type deposition

The holotype and two paratypes are deposited in the New Zealand National Arthropod Collection, Auckland, New Zealand; two paratypes are deposited in the collection of the Senckenberg Institution, Frankfurt, Germany; two paratypes are deposited in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.

Etymology

The specific name abbreviata refers to the comparatively short interlamellar setae of this species.

Remarks

Macrogena abbreviata sp. n. differs from all other species of this genus by the short interlamellar setae, which do not reach the lamellar cusps.

Figures 23–25.

Macrogena abbreviata sp. n., adult: 23 dorsal view 24 ventral view (legs not shown) 25 lateral view (leg I not shown). Scale bar 100 µm.

Figures 26–30.

Macrogena abbreviata sp. n., adult: 26 frontal view of prodorsum 27 posterior view 28 subcapitulum, ventral view 29 chelicera 30 ovipositor. Scale bars 50 µm (26, 27), 20 µm (28–30).

Figures 31–34.

Macrogena abbreviata sp. n., adult: 31 tibia, genu and femur of leg I, right, paraxial view 32 tibia, genu and femur of leg II, right, antiaxial view 33 tibia, genu, femur and trochanter of leg III, left, antiaxial view 34 tibia, genu, femur and trochanter of leg IV, left, paraxial view. Scale bar 20 µm.

Figures 35–44.

Macrogena abbreviata sp. n., dissected adult, microscope images: 35 medio-basal part of prodorsum and medio-anterior part of notogaster 36 rostral seta and medio-anterior part of tutorium 37 genal tooth and rostral incision 38 microporose in medial part of notogaster 39 notogastral porose area Aa, seta h3, lyrifissure im and opisthonotal gland opening 40 chelicera 41 custodium and discidium 42 anal seta an2, adanal seta ad3 and lyrifissure iad 43 leg I (except anterior part of tarsus), right, paraxial view 44 ventral tooth on leg II (right, antiaxial view). Scale bar 20 µm.

Key to known species Macrogena

1 Legs tridactylous; four pairs of porose areas present; body size: 315–332 × 182–199 Macrogena brevisensilla sp. n. Distribution: New Zealand.
Legs monodactylous; three pairs of porose areas present 2
2 Bothridial setae with a short stalk (half or less than the length of head) 3
Bothridial setae with a long stalk (similar or longer than the length of head) 4
3 Lamellar cusps without teeth; interlamellar setae of medium size, not reaching the lamellar cusps; body size: 254–291 × 143–151 Macrogena abbreviata sp. n. Distribution: New Zealand.
Lamellar cusps with lateral teeth; interlamellar setae long, reaching the lamellar cusps; body size: 308–330 × 198–213 Macrogena monodactyla Wallwork, 1966. Distribution: Antarctic region.
4 Lamellar cusps with lateral teeth; interlamellar setae not reaching the rostrum; body length: 240 Macrogena rudentiger Hammer, 1967. Distribution: New Zealand.
Lamellar cusps without teeth; interlamellar setae reaching the rostrum; body length: 280 Macrogena crassa Hammer, 1967. Distribution: New Zealand.

Acknowledgements

We cordially thank Prof. Dr. Badamdorj Bayartogtokh (National University of Mongolia, Ulaanbaatar, Mongolia) and one anonymous reviewer for the valuable comments, Dr. Alastair Robertson (Institute of Agriculture & Environment, Massey University, NZ) for help with fieldwork, and the New Zealand Department of Conservation for sampling permit (national authorization # 38116-GEO). The project was supported by the Massey University Research Fund.

References

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  • Hammer M (1967) Investigations on the oribatid fauna of New Zealand. Part II. Det Kong. Dansk. Vidensk. Selsk. Biol. Skr. 15(4): 1–60.
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  • Norton RA, Behan-Pelletier VM (2009) Chapter 15: Oribatida. In: Krantz GW, Walter DE (Eds) A Manual of Acarology. Texas Tech University Press, Lubbock, 430–564.
  • Subías LS, Kahwash MAM, Ruiz E (1990) Un nuevas género y tres nuevas especies de ceratozetoideos del sur de (Acari, Oribatida, Ceratozetoidea). Bol. Asoc. Esp. Ent. 14: 105–113.
  • Subías LS (2004) Listado sistemático, sinonímico y biogeográfico de los ácaros oribátidos (Acariformes: Oribatida) del mundo (excepto fósiles). Graellsia 60 (número extraordinario): 3–305. http://www.ucm.es/info/zoo/Artropodos/Catalogo.pdf [accessed in March 2015]
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Subías (2004, updated 2015) included in Macrogena the following three species: Mycobates minor Subías, Kahwash & Ruiz, 1990 from the Mediterranean, Lophozetes truncatus Balogh, 1985 from Australia and Safrobates miniporus Mahunka, 1989 from Tasmania. However, M. minor has rostral setae inserted laterally on prodorsum, dorsophragmata separated medially and six pairs of genital setae; L. truncatus and S. miniporus have lamellar cusps fused medially. Hence, the morphological characters of these species do not correspond absolutely to the generic diagnosis of Macrogena, therefore their systematic position need further investigations.