Research Article |
Corresponding author: Nestor Fernandez ( nestorfernand51@yahoo.fr ) Academic editor: Vladimir Pesic
© 2016 Nestor Fernandez, Pieter Theron.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Fernandez N, Theron P (2016) Two new oribatid mites from the Republic of Rwanda. Plasmobates zarae sp. n. (Acari, Plasmobatidae) and Basilobelba spasmenosi sp. n. (Acari, Basilobelbidae). ZooKeys 598: 1-25. https://doi.org/10.3897/zookeys.598.8972
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Two new species of oribatid mites, Plasmobates zarae sp. n. and Basilobelba spasmenosi sp. n. are described from the Republic of Rwanda. They can easily be differentiated from other species by a number of characters.
Plasmobates zarae sp. n. is differentiated the following characters. four types of particular cerotegumental layers. Integument slightly foveate to smooth on prodorsum; foveate on notogaster; ventral region rugose to smooth.Large rostral setae inserted on protuberance, whip-shaped, with longitudinal pucker; interlamellar setae rod-shaped with triangular scales; interlamellar setae small. Medial band on prodorsum extending to anterior of central part, but not reaching rostrum. Bothridium horn-shaped; opening basally incised with rectilinear wall, internal bothridial rings dentate. Sensillus whip-like, with minute triangular scales. Variably distributed circumgastric macropores. Opisthosomal gland apophysis flat, triangular in lateral view and cylindrical in posterolateral view. Six pairs of notogastral setae, all situated posterior to opisthosomal gland level. Aggenital setae not detected; three pairs of adanal setae; two pairs of anal setae present. Nymphal scalps simple without anterior tuft or filaments, with dentate peripheral ridge. Larval scalp shaped like Chinese hat.
Basilobelba spasmenosi sp. n. is characterized by the combination of the following characters: Cerotegument: thick basal layer with amorphous coat and cavities of different sizes, as well as structures resembling small cauliflowers. Setation: simple: notogastral, epimeral, genital, anal; simple long, basally barbate: le, ro setae; simple, whip-shaped: ex setae; medium length, sharpened tip with thorns on surface: in setae, leg setae; Flabellate: setae situated in ventral neotrichous zone. Thorn-like barbs and more or less parallel longitudinal grooves present on body surface of le, ro, in and leg setae. Prodorsum: rostrum finger-shaped, relative sizes of setae: le > ro > in > ex. Prodorsal cuticular surface smooth with shallow transversal furrow and two oblique furrows determining two triangular structures. Large humpbacked CSO situated anterior to and in medial line with in setal insertion, dorsal bothridial opening. Notogaster swollen, hemispheric; nine pairs of minute setae, only h1, h2, h3 easily identifiable, cuticular wart and dimple clearly visible. Humeral apophysis with longitudinal furrow dorsally. Elongate chelicera with cha, chb setae, behind them a series of scales directed dorsoventrally. Epimeral setation 3-1-3-3, adanal-aggenital neotrichy with between 8-10 setae. Nymphal scalps with very particular bean-shaped structure on either side of the decoupage zone, surrounding horn-like structure. Scalps with cuticular polyhedral reticulate to ovoid structure, often forming a cavity, either completely perforated or with a thin cuticular layer resembling an interior membrane.
Republic of Rwanda, Plasmobates zarae sp. n., Basilobelba spasmenosi sp. n., Afrotropic Ecozone
This paper is the second on material collected in Rwanda, housed at the Natural History Museum in Geneva, Switzerland. Two new species, Plasmobates zarae sp. n. and Basilobelba spasmenosi sp. n. are described. At present the family Plasmobatidae consists of four genera: Orbiculobates Grandjean, 1961; Malgachebates Fernández, Cleva, Theron, 2011; Plasmobates Grandjean, 1929 and Solenozetes Grandjean, 1931. Over the course of many years the authors have studied members of the family Plasmobatidae, principally those collected from the Afrotropic ecozone (formerly known as Ethiopian zone). This resulted in the description of the genus Malgachebates and included a summary of the principal characteristics of each genus of the family (
The taxonomy of the family Plasmobatidae is problematic due to succinct original descriptions lacking in detail, or in which important characteristics were neglected.
Plasmobates (sensu Subías 2015) consists of the following species: P. pagoda Grandjean, 1929, P. carboneli Pérez-Íñigo & Sarasola, 1998, P. hyalinus Hammer, 1971, P. asiaticus Aoki, 1973, P. africanus Balogh, 1958 “sp. inq.”, P. foveolatus Ermilov, Sidorchuk & Rybalov, 2010, P. machadoi Balogh, 1958 “sp. inq.”, P. minor Balogh, 1958 “sp. inq.”. The last four species are from the Afrotropic ecozone, and three of the four species are “species inquerendae” (sensu Subías 2015) (see Discussion). We continue the study of this group by providing a description of Plasmobates zarae sp. n. Despite more than forty years in alcohol, material was in an excellent state of preservation, conserved to the point that adequate SEM studies could be conducted.
The family Basilobelbidae contains two genera: Basilobelba Balogh, 1958 and Xiphobelba Csiszár, 1961. The taxonomy of Basilobelbidae is not clear, principally relating to the problematic original description of Xiphobelba (Csiszar 1961 page: 353) which indicates: “Rostrum pointed, chelicerae attenuated to a point, chela very small reduced” and “The new genus is an ally of Basilobelba Bal.1958, differing from it by the peculiar oral organs, resembling those of Eupelops”. The oral organs were not illustrated, and other characteristics, such as the cerotegumental layer were neither described nor figured. Only two figures were given, one dorsal with scalps and the other dorsal without scalps. In the description of a second species of the genus, X. setosa Aoki, 1968, the chelicera are partly illustrated with the rest of the infracapitulum (
More recently
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
Specimens were also studied under a Scanning Electron Microscope (SEM). Specimens preserved in ethanol 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 (
Measurements: total length (tip of rostrum to posterior edge of notogaster); width (widest part of notogaster) in micrometers (μm). Leg setation was studied using standard, polarized and phase contrast microscopes are provisional, due to the fact that only adult specimens were available for study. Setal formulae of the legs include the number of solenidia (in parentheses); tarsal setal formulae include the famulus (ε). For Plasmobates zarae we added SEM images of leg setae as detail in order to clarify a number of particularities.
Morphological terms and abbreviations used herein are those developed by F. Grandjean (1928–1974) (cf.
The specific epithet “zarae” is derived from (ζάρα, Grec=pucker, English) due to longitudinal pucker present on ro setae.
Holotype: Female and two paratypes (adult females): “73/2. Kayove-Rwanda; 2100 mts. 15/V/1973” Leg. P.Werner; deposited in the Collection of the Natural History Museum of Geneva (M.H.N.G), Switzerland; preserved in 70% ethanol. Material studied for SEM: three specimens, not deposited.
Cerotegumental layer. Amorphous: bothridial zone, tubercle of seta in, ro setae insertion, lateral gland, epimeral zone, genital plate and surrounding zone, anal plate and surrounding zone. Layer with small tubercles: internal bothridial zone. Mixed-layer (mushroom-like microtubercles associated with irregular cauliflower-like microtubercles): infracapitulum, epimeral zone, lateral body zone, basal zone lateral gland. Integument: prodorsum, small foveate to smooth; notogaster, foveate; ventral region rugose to smooth.
Setation: simple: lamellar, notogastral, exostigmatal, epimeral, genital, aggenital anal; whip-shaped, with longitudinal pucker: rostral setae; rod-shaped with triangular scales: interlamellar setae; simple, basally inflated: subcapitular a; simple spur: m.
Prodorsum: medial band extension on central part towards anterior, not extending to rostrum. Interlamellar setae inserted on large protuberances, lamellar setae small, rostral setae large, with longitudinal cuticular puckers, inserted on protuberances. Large horn-shaped bothridium, directing laterally, rectilinear wall with basally incised opening. Internal bothridial rings dentate. Whip-shaped sensillus with minute, triangular scales; exostigmatal seta small. Rostrum medially incised, posterior of incision rounded. Notogaster: fovea situated in smooth zone with circumgastrically distributed macropores on fovea margins or inside fovea. Opisthosomal gland apophysis flat, triangular in lateral view, cylindrical in posterolateral view. Six pairs of notogastral setae, all situated posterior to level of opistosomal gland. Lateral region: opening of podocephalic canal on large promontories.
Ventral region: epimeral setal formula (3-1-2-2). Seven pairs of genital setae; aggenital setae not detected. Three pairs of adanal setae, two pairs of anal setae. Scalps multilayered, medial band extending anteriorly from each scalp. Medial band covers central zone, firmly adhered to prodorsal surface. Nymphal scalps with dentate peripheral ridge. Setae hardly discernible, scalps simple without anterior tuft of filaments. Chinese hat-shaped larval scalp differing greatly from nymphal scalps
Measurements.SEM: total length with scalps 580–615 μm × 600 μm (measurements on three specimens). Total length without scalps 433–438 μm × 435μm (measurements on three specimens). Notogastral width without scalps 248–253 μm × 250 μm. Light microscopy: 612–656 μm × 639 μm (measurements on three specimens). Specimens with scalps ovoid, elongate in dorsal view. (Figures
Plasmobates zarae sp. n. Adult; 1–5 optical microscopy image 6–8SEM1 dorsal view 2 lateral view 3 frontal view 4 lamellar setae 5 promontories podocephalic canal 6 dentate peripheral ridge (p.d.r), lateral inclined view 7 cerotegumental layer and cuticular microsculpture 8 dentate peripheral ridge (p.d.r), frontal view. Abbreviations: see Materials and methods. Scale: 1 = 100 μm; 2 = 200 μm; 3 = 70 μm; 8 = 50 μm; 6 = 30 μm; 7 = 10 μm; 4, 5 = 5 μm.
Plasmobates zarae sp. n. Adult; SEM micrographs. 9 dorsal view with scalp and cerotegument layer 10 rostral setae, detail 11 rostral setae, general view 12 interlamellar seta 13 medial band detail, dorsal view. Abbreviations: see Materials and methods. Scale: 9 = 100 μm; 11, 13 = 20 μm; 12 = 5 μm; 10 = 2 μm.
Plasmobates zarae sp. n. Adult; SEM. 14 lateral view with scalp and cerotegumental layer 15 bothridium and interlamellar seta, lateral view 16 bothridium, internal structures 17 sensillus, superficial scales (high magnification) 18 lateral gland 19 sensillus detail. Abbreviations: See Materials and methods. Scale: 14 = 100 μm; 15 = 20 μm; 18 = 10 μm; 16, 19 = 5 μm; 17 = 1 μm.
Colour. Specimens without cerotegument and scalps dark yellowish to medium brown.
Cerotegument (scalps not considered). Thick complex layer with elaborate pattern, composed of wax layer and amorphous cement layer covering entire body and legs. Amorphous layer (Figure
Plasmobates zarae sp. n. Adult; SEM. 25 epimeral zone 26 subcapitular seta h27 subcapitular seta a28 cerotegumental layer 29 detail cerotegumental “cauliflower” (cau) 30 detail cerotegumental “mushroom” (mus) 31 prodorsum with m.b. 32 anogenital region 33 detail cerotegumental layer. Abbreviations: see Materials and methods. Scale: 25 = 50 μm; 26 = 5 μm; 27 = 5 μm; 28 = 1 μm; 29 = 0.5 μm; 30 = 0.5 μm; 31 = 20 μm; 32 = 50 μm; 33 = 5 μm.
Plasmobates zarae sp. n. Adult; Optical and SEM observations. 34 leg I, antiaxial 35 detail with SEM; solenidium s genu I 36 detail with SEM, solenidia j1, j2 and setae d, femur I 37 leg II, antiaxial 38 apical zone, tarsus II (detail with SEM) 39 solenidium j1, dorsal setae d and complementary seta indicated byl, tibia I (detail SEM observation) 40 leg III, antiaxial 41 leg IV, antiaxial 42 tibia I, solenidium j and setae d (detail SEM observation). Abbreviations: see Materials and methods. Scale: 34–42 = 70 μm.
Integument. lateral microsculpture of prodorsum faintly foveate to smooth (Figures
Setation. Lamellar (Figure
Prodorsum. Medial band extension (m.b) observed on central part towards anterior, not extending to rostrum, terminating anterior to le setal insertion level on specimens with scalps (Figures
Whip-shaped filiform sensillus (si) (80-106 μm) with minute triangular scales, height 196 nm, length 603-987 nm (Figure
Notogaster. Circumgastrically distributed macropores (mp) of varying diameter (0.3–1 μm) situated in small foveae on smooth zone, either on periphery or internally to foveated notogastral pattern (Figures
Distribution of mp: a) single line in anterior notogastral zone; b) linear in anterior lateral zone near gla; c) irregularly distributed on posterior notogastral zone (setal zone) (Figure
In dorsal view opisthosomal gland (gla) apophysis observed as flat triangle, but appears cylindrical in lateral and lateroposterior views, directing slightly obliquely forward (Figures
Lateral region. Exobothridial seta (ex) small but clearly discernible (Figure
Ventral region. Specimens with cerotegument: plate-like cerotegumental structures on epimeres resulting in irregular levels on upper surface, epimeral furrows easily discernible with mus, cau and amorphous cerotegumental layer (Figure
Gnathosoma. Subcapitulum suctorial with short tube. Subcapitular setae large, especially a, m (Figure
Legs (Table
Femur | Genu | Tibia | Tarsus | Observations | |
---|---|---|---|---|---|
Leg I | |||||
Setae | da,(l),va,vp, vp1 | (l),v,d | d,(l),(v) | pl’,(l),(v),(ft),(tc),(p),(u),(a),S,(v),e | Crispinate (socket-like) dorsal femur, solenidium s clavate, d seta positioned near j2, usually near j1 |
Solenidium | - | s | j1, j2 | w1, w2 | |
Leg II | |||||
Setae | l”,d,va,vp | d,(l),(v) | d,l,(l)(v) | (ft),(l),(p)(u),S,(a),pv’ | crispinate (socket-like) dorsal femur, solenidium s clavate, genu with one d seta near j, also another associated minute seta indicated by l |
Solenidium | s | j | w1, w2 | ||
Leg III | |||||
Setae | d,l’,v, | d,l”, v | d,l”,(v) | (ft),(p),(u),S,(a),(l) | |
Solenidion | s | j | ----------------- | ||
Leg IV | |||||
Setae | (l),v | d,l”,v | d,(l),(l) | (ft),pv’,(a),S,(u),(p) | |
Solenidion | --------- | j | --------------------- |
Scalps. Exuviae of immature stases adhering one on top of the other, creating a multilayered structure. Each scalp extending anteriorly into a medial band (m.b) (Figures
Cerotegumental layer: medial band covered by thick amorphous layer with a network of round to polygonal depressions (Figure
SEM is vital in order to observe aspects such as: 1) dorsal seta d associated with solenidium hardly discernible (detailed drawings are included to facilitate understanding) 2) clavate shape of small solenidia is problematic, as doubt regarding the exact shape remains if using only optical microscopy 3) the position of dorsal seta d relative to j1 and j2 on tibia II differs from Solenozetes makokouensis and Malgachebates peyrierasi. Changed angles of observation and rotation of specimens in SEM clarified the situation. 4) accessories available in SEM facilitated measurements of minute triangular scales of the sensillus with great precision 5) protuberances situated around the opening of the lateral gland also had to be observed from different angles. See Discussion for comparison with congeners.
The specific epithet “spasmenosi” is derived from (Σπασμένος, Grec = broken, English), due to characteristics of scalps with cavities or perforations.
Holotype: Female and two paratypes (adult females):. “73/2. Kayove-Rwanda; 2100 mts.15/V/1973” Leg. P.Werner; material deposited in the Collection of the Natural History Museum of Geneva (M.H.N.G), Switzerland; preserved in 70% ethanol. Material studied for SEM: three specimens, not deposited.
Cerotegument. Thick basal layer with amorphous coat, perforations of various sizes, and structures resembling small cauliflowers. Setation. Simple: notogastral, epimeral, genital, anal; simple, long, basal barbs: le, ro setae; simple, whip-shaped: ex setae; medium length, sharpened tip with thorn-like barbs on surface: in setae, leg setae; flabellate: setae situated in ventral neotrichy zone. Thorn-like barbs and more or less parallel longitudinal grooves on body of le, ro, in and leg setae. Prodorsum. Rostrum finger-shaped, relative sizes of setae: le > ro > in > ex. Prodorsal cuticular surface smooth, with shallow transversal furrow and two oblique furrows delineating two triangular structures. Large humpbacked CSO situated anterior to and in medial line with in setal insertion, dorsal bothridial opening. Notogaster. Swollen, hemispheric, with nine pairs of minute setae. Only h1, h2, h3 easily identifiable. Cuticular wart and dimple clearly visible. Humeral apophysis with longitudinal furrow dorsally. Chelicera elongate, series of dorsoventrally directing scales behind setae cha, chb. Epimeral setation 3-1-3-3, adanal-aggenital neotrichy with 8-10 setae. Nymphal Scalps. Particular bean-shaped structure on either side of the decoupage zone around horn-like structure. Scalps with polyhedral reticulate to ovoid cuticular structure. Polyhedral reticulate cuticular structure often appears either completely perforated or with a thin cuticular layer resembling an interior membrane.
Measurements.SEM: total length without scalps 618–598 × 605 μm; width without scalps 310–290 × 303 μm (measurements on three specimens). Light microscopy: 660–632μm × 643 μm; width 325–315 × 320 μm (measurements on three specimens).
Shape. Elongated oval (Figures
Basilobelba spasmenosi sp. n. Adult; SEM. 43 dorsal view with scalps 44 dorsal view with scalp 45 posterior zone of scalps 46 prodorsum anterior zone 47 arched tritonymphal buckle. Abbreviations: see Materials and Methods. Scale bars: 43 = 200 μm; 44 = 50 μm; 45 = 20 μm; 46 = 50 μm; 47 = 2 μm.
Basilobelba spasmenosi sp. n. Adult; Optical microscopy. 48 anterior zone prodorsum 49 ventral zone without subcapitulum 50 ventral setae 51 Chelicera, lateral view 52 notogaster posterior view. Abbreviations: see Materials and methods. Scale bars: 52 = 100 μm; 49 = 70 μm; 50 = 25 μm; 48, 51 = 20 μm.
Colour. Specimens without cerotegument brown, slightly shiny when observed in reflected light.
Cerotegument. Present only on prodorsum, notogastral anterior zone, ventral region and legs. Thick basal layer with amorphous coat and perforations of various sizes (indicated by¿ Figure
Setation. Simple: notogastral, epimeral, genital, anal (Figures
Integument. Smooth
Prodorsum. Rostrum finger-shaped (Figures
Prodorsal cuticular surface smooth with a shallow transversal furrow situated anterior to in setal insertion (Figure
Ovoid bothridial opening dorsally (Figures
Frontal view. Beak-shaped rostral margin (Figure
Notogaster. Swollen, hemispheric (Figure
Lateral region. Only pedotectum I present (Figure
Ventral region. Subcapitulum diarthric, cerotegumental layer observed only behind h setal insertions (Figure
Epimeres I, II typical morphology, ventrosejugal furrow easily discernible, other epimeres not visible. Epimeral setation 3-1-3-3 (Figures
Legs (Figures
Basilobelba spasmenosi sp. n. Adult; SEM. 63 posterior view deutonymphal and tritonymphal scalps 64 posterior zone deutonymphal scalps, detail 65 dorso-posterior view deuto and tritonymphal scalps 66 tritonymphal scalps, posterior view 67 deutonymphal scalp, detail, anterior zone 68 detail s.r.s and c1 seta, deutonymphal scalp 69 interior view, tritonymphal scalp. Abbreviations: see Materials and methods. Scale bars: 63 = 100 μm; 64 = 20 μm; 65 = 50 μm; 66 = 100 μm; 67 = 20 μm; 68 =5 μm; 69 = 20 μm.
Femur | Genu | Tibia | Tarsus | |
---|---|---|---|---|
Leg I | ||||
Setae | d,(l),(v),bv | (l),d,v | d,(l),(v) | (ft),l”,(pl),v,(pv),(tc),(it),(p),(u),s,(a),e |
Solenidium | -------- | s | j1 , j 2 | w1, w2 |
Leg II | ||||
Setae | d,v” | d,(l),v | d,(l),v | (ft),(pv),S,(a),(u),(it),(tc),l’ |
Solenidium | s | j | w1, w2 | |
Leg III | ||||
Setae | d,l’,v | d,v,l’ | d,l’(v) | ft’,(pv),(tc),(it,)(u),(a),S |
Solenidium | ||||
Leg IV | ||||
Setae | d,l’,v | d,l’ | d,l’(v) | (tc),ft”,(pv)s,(a)(u) |
Solenidium | ----- | j | ------- |
Setal formulae: I(1-6-4-5-20-1) (1-2-2); II(1-2-4-4-14-1) (1-1-2); III(2- 3-3-4-12-1) (1-1-0); IV(1-3-2-4-10-1) (0-1-0). Setae d present on all femurs, genua and tibiae. On tibia I (Figure
Nymphal Scalps. Limited number of specimens and the necessity of dissection impeded comprehensive study of scalps, for this reason our study was limited to deutonymphal and tritonymphal scalps. Observed particularities: Very particular bean-shaped structures are found on either side of the decoupage zone around the horn-like structure (Figures
Scalps present polyhedral reticulate to ovoid cuticular structure (s.r.s), most visible on internal side (Figure
Tritonymphal scalps (Figures
Deutonymphal scalps (Figures
The remarkable perforated structures are not observed in other congeners. At present we are studying another species from Rwanda with bean-shaped structures on scalps, similar to those in Basilobelba spasmenosi sp. n.
The taxonomy of the genus Plasmobates in the Afrotropic ecozone is very complex. Species of the genus Plasmobates Grandjean, 1929 recorded in this region are: P. africanus Balogh, 1958; P. foveolatus Ermilov et al., 2010; P. machadoi Balogh, 1958; P. minor Balogh, 1958; and P. zarae sp. n. Subías (2015) considers P. africanus Balogh, 1958; P. machadoi Balogh, 1958 and P. minor Balogh, 1958 as “sp. inq.”, without providing reasons. We analyzed the work of
In our opinion the following characteristics permit easy differentiation of species of Plasmobates from other congeners, not only those from the Afrotropic ecozone: the cerotegumental layer, shape and insertion type of ro and in setae, sensillus with scales, promontories of podocephalic canal, distribution of macropores, type of lateral gland, number and distribution of notogastral setae, positions of setae d of tibia I and particular setae found on tibia II.
The taxonomy of Basilobelba Balogh, 1958 and Xiphobelba Csiszár, 1961 were discussed in preceding work (
Our sincere gratitude to Dr Louwrens Tiedt, Laboratory for Electron Microscopy, North-West University, South Africa, for assistance with SEM-studies. 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 manuscript are those of the authors and therefore the NRF does not accept any liability in regard thereto.