Die postembryonale Entwicklung und die funktionelle Anatomie des Gnathosoma in der Milbenfamilie Erythraeidae (Acarina,Prostigmata)

Zusammenfassung Das Gnathosoma von sieben Arten der Milbenfamilie Erythraeidae wurde untersucht. Die postembryonale Entwicklung der Cuticula-Strukturen, der Muskulatur und der Drüsen wird beschrieben.Das Gnathosoma der Larven weist Cheliceren auf, die aus Grundglied und klauenförmigem Digitus mobilis bestehen. Sie liegen dem Infracapitulum dorsal auf und inserieren an einem Paar Capitular-Apophysen. Bei den Protound Tritonymphen unterliegt das Gnathosoma der Histolyse und wird anschließend jeweils neu ausgebildet. Bei der Deutonymphe und beim Adultus ist es gegenüber der Larve stark abgewandelt: Die Tracheenstämme sind aus den Capitular-Apophysen der Larve abzuleiten. Die Stech-Cheliceren entsprechen dem Grundglied der larvalen Cheliceren, und ihre medialen Protraktoren gehen aus den Levator-Muskeln der Cheliceren der Larve hervor.Der Weg der Sekrete der podocephalischen und infracapitulären Drüsen über die Dorsalfläche des Infracapitulum erfährt mit dem Erwerb schmaler Stech-Cheliceren eine radikale Umstellung des Schutzes gegen Austrocknung. Während bei der Larve die breiten Cheliceren-Grundglieder den Sekretweg überdecken, und der Raum zwischen den Grundgliedern und dem Infracapi-tulum zusätzlich durch das ölartige Sekret der Intercheliceraldrüse ausgefüllt wird, schließen sich bei der Deutonymphe und beim Adultus die Lateralkiele der Genae über den Stech-Cheliceren zusammen, und der hintere Abschnitt des Cervix wird in das Idiosoma eingesenkt. Dadurch wird der Cervix zu einem internen Cervicalkanal umgebildet.Der Mundraum wird bei den aktiven Stadien durch die lipidartigen Sekrete der Buccal- und Labialdrüsen geschützt.Die phylogenetischen Beziehungen der Parasitengona innerhalb der Prostigmata und der Erythraeidae innerhalb der Parasitengona werden diskutiert.

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Postembryonic development and functional anatomy of the gnathosoma in the family Erythraeidae (Acarina, Prostigmata)

Summary The gnathosoma of seven species of the Erythraeidae was investigated. The postembryonic development of the cuticular structures, the musculature and the glands are described.In the larval gnathosoma, the chelicerae consist of a basal segment and a claw. They rest upon the dorsal surface of the infracapitulum. The basal segments are attached to a pair of capitular apophyses (sigmoid pieces). During the two molts larva to protonymph and deutonymph to tritonymph, the gnathosoma is histolysed. Directly afterwards it is rebuilt. Compared to the larva, in the deutonymph and in the adult it undergoes profound changes: The capitular apophyses are transformed to parts of the tracheae, the basal segment of each chelicera to a styliform chelicera, and the levator muscles of the chelicerae to medial protractors of the styliform chelicerae.The secretions of the podocephalic and infracapitular glands proceed along the dorsal surface of the infracapitulum to the buccal cavity. In the larva, the way of the secretions is protected against desiccation by the broad basal segments of the chelicerae, that cover the infracapitulum. In addition the oily secretion of the intercheliceral gland seals the space between the infracapitulum and the chelicerae. By obtaining styliform chelicerae the protection against desiccation undergoes a radical change: The lateral ridges of the infracapitulum join above the chelicerae, and the posterior part of the cervix is transferred back into the idiosoma. Thus the cervix is transformed into an internal canal.In the active instars, the buccal cavity is protected by the lipid-like secretions of the buccal glands and labial glands.The phylogenetic relationships of the Parasitengona within the Prostigmata, and of the Erythraeidae within the Parasitengona are discussed.

     

The affinities of mites and ticks: a review

Mites and ticks can be divided into two well-defined clades, Anactinotrichida and Actinotrichida, for which a recent work formalized a suite of putative autapomorphies and reciprocal differences. Whether they are sister-taxa – forming a monophyletic Acari – is more controversial. Earlier supporters of two independent origins for mites largely failed to demonstrate convincing synapomorphies between either of the two lineages and other arachnid orders; although recent work on reproductive biology revealed explicit characters of this nature. Furthermore, some of the characters proposed in support of a monophyletic Acari do not stand up to detailed scrutiny when compared with Arachnida in general. Effective morphological comparisons between mites and other arachnids are hindered by incompatible nomenclature and long-standing, mite-specific characters which are difficult to score for other arachnids. Furthermore, taxon-specific characters restricted to individual mite groups have sometimes been treated erroneously as 'typical' for all Acari. Here, previous hypotheses of mite affinities are reviewed. Historically, authors have debated whether mites are basal arachnids or highly derived. Excluding weakly supported early hypotheses, mites have been resolved – in whole or in part – as sister-group of all other Arachnida (based on tagmosis), closely related to Opiliones (based mostly on genital morphology), Palpigradi (based on controversial interpretations of limb morphology), Solifugae (based mostly on the mouthparts, but now perhaps also reproductive characters) and Ricinulei (based on hexapodal larvae and perhaps mouthparts). We cannot provide a final resolution here, but we aim to highlight important character sets which should be included in subsequent phylogenetic analyses, as well as useful areas for future investigations: particularly tagmosis and the nature of the gnathosoma.     

Structure and function of the gnathosoma of the mange mite,Psoroptes ovis

Mites of the genus Psoroptes (Acari: Psoroptidae) are obligate, non-burrowing, astigmatid ectoparasites of mammals. A detailed understanding of the morphology of the gnathosoma is an important step towards elucidation of the feeding behaviour of this mite and, hence, the pathology of psoroptic mange. Scanning and transmission electron microscopy were used to examine Psoroptes ovis (Hering) (syn. P. cuniculi). The gnathosoma is composed of an infracapitulum (hypostome), which forms the floor of an extended U-shaped pre-oral trough, bounded by laterally compressed palps and enclosing paired chelicerae. Distally, each palp terminates in a flap-like process and four tapered terminal sensillae. The floor of the infracapitulum is interrupted along its length by a dorsally projecting ridge. At the distal end of the infracapitulum are paired, grooved pseudorutellae and, between them, paired, ungrooved lateral lips. Between the lateral lips is a grooved, elongate labium. Medially, a pair of finger-like projections emanates from the paraxial walls of the palps and project anteriorly. Each chelicera is made up of fixed and mobile digits, with a cheliceral membranous fold articulating the two. The distal ends of both digits are chelated. For much of its length, the mobile cheliceral digit appears to lie within a fold formed by the infracapitular ridge, thereby creating a central channel between the chelicerae. It is suggested that this arrangement of elements may facilitate a two-way flow of liquid, where saliva flows down a central salivary canal and spills out onto the host's skin over the labium at the point where the chelated tips of the chelicerae meet and abrade the skin. Liquid food may move along the grooves of the pseudorutellae and then be sucked up a food canal formed by the paraxial walls of the palps and the outer wall of the chelicerae.     

A new use for synchrotron X‐ray microtomography: three‐dimensional biomechanical modeling of chelicerate mouthparts and calculation of theoretical bite forces

Abstract. We present the first report on the use of the non‐invasive method of synchrotron X‐ray microtomography to model the dynamics and theoretical bite forces of arthropod mouthparts. The nature of the data allowed us to include precise measurements of muscle areas and the spatial geometry of muscle origins and insertions into a biomechanical model of a morphological microstructure. We investigated the functional morphology of the chelicera in the oribatid mite Archegozetes longisetosus (Acari, Oribatida), a model organism for Chelicerata. The chelicera represents a first‐class lever; the intrinsic muscular system consists of a feather‐shaped depressor with six muscle bundles and a bouquet‐shaped levator with 16 bundles. The relative bite forces, as compared with body mass (force/mass^2/3), are 390 N kg^?1 and lie within those known for vertebrates (≤260 N kg^?1) and decapod chelae (≤915 N kg^?1). The dynamics of force transmission and bite forces during the movement of the apotele are calculated. The conserved organization of cheliceral musculature allows broad adaptation of the model to other chelicerate taxa.     

A new species of the genus Pergalumna Grandjean, 1936 from Iran (Acari: Oribatida: Galumnidae)

A new species of galumnid mite (Acari: Oribatida: Galumnidae), Pergalumna persica sp. n., is described from Fars province, southern Iran. The new species is characterised by a pointed rostrum, minute interlamellar setae, medium long, setiform sensilla, with finely barbed, slightly dilated head, complete dorsosejugal suture, large, nearly elongate-triangular areae porosae Aa, absence of median pore, and large body size.     

Ultrastructural investigations of the salivary glands in adults of the microtrombidiid mite Platytrombidium fasciatum (C. L. Koch, 1836) (Acariformes: Microtrombidiidae)

The organization of the salivary glands in ad libitum-fed adult females of the microtrombidiid mite Platytrombidium fasciatum (C. L. Koch, 1836) was observed using transmission electron microscopy. In all, four pairs of large simple alveolar salivary glands were determined, which have been named due to their position as posterior, ventral, medial and dorsal. These glands occupy a body cavity behind, around the base and partly inside the gnathosoma. The posterior glands are largest and possess large nuclei with greatly folded nuclear envelope. Secretory granules are electron-light, containing fine granular material and are partly provided with various lamellar inclusions inside the granules. The latter tend to be placed predominantly in the middle parts of the gland around the central (intra-alveolar) cavity. The remaining glands, conversely, are typically filled with tightly packed electron-dense secretory granules, except for the ventral glands, the granules of which may show a compound organization. The nuclei of all these glands occupy a peripheral position and are mostly pressed between the granules. No prominent endoplasmic reticulum or conspicuous Golgi bodies were observed within the salivary glands. The salivary glands are provided with a complex apparatus of the intra-alveolar cavity (acinar lumen) with the excretory duct base provided by a system of branched special cells producing the duct walls. The ventral glands open by separate ducts into the most posterior part of the subcheliceral space. Ducts of the posterior glands immediately fuse with the ducts of the tubular (coxal) glands. The common duct of each side of the body joins with the ducts of the medial and dorsal glands respectively, and opens into the subcheliceral space far anterior to that of the ventral glands.     

New Species of Oribatid Mites of the Superfamily Oripodoidea Jacot, 1925 (Acari,Oribatida) from Trinidad and Tobago

Two new species of oribatid mites of the superfamily Oripodoidea (Acari, Oribatida) are described from Trinidad and Tobago. Scheloribates (Scheloribates) tobagoensis sp. n. (Scheloribatidae) differs fromS. (Scheloribates) papillaris Tseng, 1984 in the structure of the rostral and lamellar setae and leg solenidia, in the length of the prolamellae, the absence of aggenital setae, and in reduction of setae on tarsi III. Areozetes ryabinini sp. n. (Haplozetidae) differs from A. altimontanus Hammer, 1961 in the structure of the bothridial and notogastral setae and rostrum and in the number of claws on the tarsi.     

拱殖嗜渣螨各发育阶段的体表形态观察

【目的】观察和认识拱殖嗜渣螨Chortoglyphus arcuatus不同发育阶段主要外部形态特征及超微结构。【方法】用啤酒酵母粉纯化饲养拱殖嗜渣螨,选取不同发育阶段个体清洁后,分别利用体视显微镜、光学显微镜以及扫描电子显微镜对螨体颜色、形态特征、局部特征以及超微结构进行观察。【结果】成螨颜色为鲜明的淡棕红色,其他发育阶段均为乳白色。躯体硬,卵圆形。无背横沟划分前足体和后半体。螯肢发达,螯钳剪状,有纵纹,具明显的齿。外顶毛有栉齿。颚体基部腹面有细横纹。体躯刚毛短,光滑。雌螨生殖孔位于Ⅲ和Ⅳ基节之间,覆有骨化的生殖板。生殖板后缘光滑、弓形。雄螨阳茎位于Ⅰ和Ⅱ基节之间,长且弯曲、管状。有肛吸盘,漏斗状。有跗节吸盘。【结论】本研究补充了拱殖嗜渣螨文献未记载的一些特征,如卵、幼螨和若螨体色,螯肢背面和颚体腹面刻纹等,有助于该螨及其近缘种的快速鉴定和分类研究。     

Morphology of locomotor appendages in Arachnida: evolutionary trends and phylogenetic implications

The morphological diversity of locomotor appendages in Arachnida is surveyed lo reconstruct phylogenetic relationships and discover evolutionary trends in form and function. The appendicular skeleton and musculature of representatives from the ten living arachnid orders ate described, and a system of homology is proposed. Character polarities are established through comparison with an outgroup. Limulus polyphemus Xiphosura). Cladistic analysis suggests that Arachnida is monophyletic and that absence of extensor muscles is a primitive condition. Extensors are primitively absent in Araneae. Amblypygi, Uropygi, Palpigradi, Ricinulei and Acari. Most similarities in the appendages of these orders are symplesiomorphic so that phylogenetic relationships among the ‘extensorless’ groups cannot be resolved solely on the basis of appendicular characters. Extensor muscles appear to have evolved once, and their presence is considered a synapomorphic feature of Opiliones, Scorpiones, Pseudoscorpiones and Solifugae. Solifugae lack extensors, but a parsimonious interpretation of other characters indicates that this is a secondary, derived condition. The phylogenetic relationships among these four orders are clarified by modifications of the patellotibial joint. Cladistic analysis indicates that Opiliones may be the sister group of the other three orders and that Scorpiones is the sister group of Pseudoscorpiones and Solifugae. Conclusions concerning phylogenetic relationships and evolutionary morphology presented here differ substantially from those of earlier studies on the locomotor appendages of Arachnida.     

Morphology of locomotor appendages in Arachnida: evolutionary trends and phylogenetic implications

The morphological diversity of locomotor appendages in Arachnida is surveyed lo reconstruct phylogenetic relationships and discover evolutionary trends in form and function. The appendicular skeleton and musculature of representatives from the ten living arachnid orders ate described, and a system of homology is proposed. Character polarities are established through comparison with an outgroup. Limulus polyphemus Xiphosura). Cladistic analysis suggests that Arachnida is monophyletic and that absence of extensor muscles is a primitive condition. Extensors are primitively absent in Araneae. Amblypygi, Uropygi, Palpigradi, Ricinulei and Acari. Most similarities in the appendages of these orders are symplesiomorphic so that phylogenetic relationships among the 'extensorless' groups cannot be resolved solely on the basis of appendicular characters. Extensor muscles appear to have evolved once, and their presence is considered a synapomorphic feature of Opiliones, Scorpiones, Pseudoscorpiones and Solifugae. Solifugae lack extensors, but a parsimonious interpretation of other characters indicates that this is a secondary, derived condition. The phylogenetic relationships among these four orders are clarified by modifications of the patellotibial joint. Cladistic analysis indicates that Opiliones may be the sister group of the other three orders and that Scorpiones is the sister group of Pseudoscorpiones and Solifugae. Conclusions concerning phylogenetic relationships and evolutionary morphology presented here differ substantially from those of earlier studies on the locomotor appendages of Arachnida.     

Repeated convergent evolution of parthenogenesis in Acariformes (Acari)

The existence of old species‐rich parthenogenetic taxa is a conundrum in evolutionary biology. Such taxa point to ancient parthenogenetic radiations resulting in morphologically distinct species. Ancient parthenogenetic taxa have been proposed to exist in bdelloid rotifers, darwinulid ostracods, and in several taxa of acariform mites (Acariformes, Acari), especially in oribatid mites (Oribatida, Acari). Here, we investigate the diversification of Acariformes and their ancestral mode of reproduction using 18S rRNA. Because parthenogenetic taxa tend to be more frequent in phylogenetically old taxa of Acariformes, we sequenced a wide range of members of this taxon, including early‐derivative taxa of Prostigmata, Astigmata, Endeostigmata, and Oribatida. Ancestral character state reconstruction indicated that (a) Acariformes as well as Oribatida evolved from a sexual ancestor, (b) the primary mode of reproduction during evolution of Acariformes was sexual; however, species‐rich parthenogenetic taxa radiated independently at least four times (in Brachychthonioidea (Oribatida), Enarthronota (Oribatida), and twice in Nothrina (Oribatida), (c) parthenogenesis additionally evolved frequently in species‐poor taxa, for example, Tectocepheus, Oppiella, Rostrozetes, Limnozetes, and Atropacarus, and (d) sexual reproduction likely re‐evolved at least three times from species‐rich parthenogenetic clusters, in Crotonia (Nothrina), in Mesoplophora/Apoplophora (Mesoplophoridae, Enarthronota), and in Sphaerochthonius/Prototritia (Protoplophoridae, Enarthronota). We discuss possible reasons that favored the frequent diversification of parthenogenetic taxa including the continuous long‐term availability of dead organic matter resources as well as generalist feeding of species as indicated by natural variations in stable isotope ratios.     

山羊蠕形螨扫描电镜观察

本文通过扫描电镜对寄生虫山羊体的山羊蠕形螨生活史各期颚体,足体和末体的超微结构观察,发现以下超微结构;一个圆锥状须乳突位于雌螨触须第２节背面;叶状背阳茎侧突和腹阳茎侧突竖立于阳茎同一基部,未受精雌螨船形阴门的一对瓣汇成纵线,雌螨交配后阴门半开,产卵后全部敞开,同时描述该螨的背基刺,锥状突,口下板,螯肢,基内叶,口孔,须爪和肛道等的超微结构,文中还讨论了锥状突,口下板,螯肢,基内叶,须爪和须乳突的功     

The idiosomal chaetotaxy of astigmatid mites

Within the Astigmata, setal homologies with the general chaetotaxic systems developed for acariform mites by F. Grandjean have never been convincingly established. This study deals with all body regions, exclusive of legs and gnathosoma, mostly utilizing as models astigmatid species from three different families. Six hypotheses which attempt to explain the ontogeny of segments, setae and cupules in the caudal bend region are compared using three-dimensional views obtained by scanning electron microscopy. The hypotheses are evaluated by in-group comparisons testing their consistency with presumed segmental boundaries, and by out-group comparisons with oribatid mites. The strongest, most parsimonious hypothesis suggests that larval astigmatid mites possess segment F, but not its setae, and the two pairs posterior to segment F are h _l and h ₂, whilst the five setae added in the protonymph are h ₃, f ₂ and ps _1–3. Six pairs of structures on the deutonymphal anal plate are identified as modified setae, and evidence supporting their homologies with setae of other instars is discussed for the first time. A comparison of the principal chaetotaxic systems used for the dorsal and anal regions of the Astigmata is presented. Application of Grandjean's setal signatures to these regions, as well as to the coxisternal and genital regions, is discussed and illustrated by examples.     

Two new species of the family Suctobelbidae (Acari,Oribatida) from Chile

Two new species of the oribatid mite family Suctobelbidae (Acari, Oribatida) are described from southern Chile. Niosuctobelba sphagnicola Ermilov, sp. n. differs from N. ruga Chinone, 2003 in the rostrum with a median incision and one pair of lateral teeth, the heads of bothridial setae rounded distally, the tectopedial fields not fused anteriorly, the notogastral setae barbed, and the body without striate ornamentation. Zeasuctobelba tierradelfuegoensis Ermilov, sp. n. differs from Z. trinodosa Hammer 1966 in a shorter body, the heads of the bothridial setae with thin apices, the tectopedial fields not fused anteriorly, and the notogastral humeral tubercles with longer cristae. An identification key to the known species of Zeasuctobelba is given. The genus Niosuctobelba is recorded for the Neotropical Region for the first time, while Zeasuctobelba is new to the fauna of Chile.     

Oribatid mites of the superfamily Trizetoidea Ewing, 1917 (Acari,Oribatida) from Peru

Two new species of the oribatid mite superfamily Trizetoidea (Acari, Oribatida) are described from Peru. Rhynchoribates (Rhynchoribatodes) rioyuyapichisensis Ermilov, sp. n. differs from the other species of the subgenus by the long flagelliform notogastral setae. Rhynchoppia puertoincaensis Ermilov, sp. n. is morphologically similar to R. capillata (Balogh, 1963), but differs by the shape and in a greater number of rostral teeth, in the number and a smaller length of notogastral setae, and in the number of genital setae. The genus Rhynchoppia (Balogh 1968) is recorded from the Neotropical Region for the first time, while Rhynchoribates (Rhynchoribatodes) brasiliensis Woas 1986 is new to the fauna of Peru.     

The biology of the development of the Oribatid Mite <Emphasis Type="Italic">Carabodes subarcticus</Emphasis> (Acari,Carabodidae)

The development of the oribatid mite Carabodes subarcticus (Oribatida, Carabodidae) was studied in the laboratory. The morphology of all the juvenile stages is described; the duration of post-embryonic development is given. The structure of the gnathosoma, ovipositor and legs of adult mites is described. The life history of C. subarcticus, C. labyrinthicus, and C. willmanni is briefly compared.     

Functional anatomy of scent glands in Paranemastoma quadripunctatum (Opiliones,Dyspnoi, Nemastomatidae)

The morphological organization and functional anatomy of prosomal defensive (scent) glands in Paranemastoma quadripunctatum, a representative of the dyspnoid harvestmen, was investigated by means of histological semithin sections, software‐based 3D‐reconstruction and scanning electron microscopy. Scent glands comprise large, hollow sacs on either side of the prosoma, each of these opening to the outside via one orifice (ozopore) immediately above coxa I. In contrast to the situation known from laniatorean, cyphophthalmid and some eupnoid Opiliones, ozopores are not exposed but hidden in a depression (atrium), formed by a dorsal integumental fold of the carapace and the dorsal parts of coxae I. Glandular sacs are connected to ozopores via a short duct which is equipped with a specific closing mechanism in its distal part: A layer of modified epidermal cells forms a kind of pad‐like tissue, surrounding the duct like a valve. Several muscles attached to the anterior parts of the glandular reservoir and to the epithelial pad may be associated with ozopore‐opening. The actual mechanism of secretion discharge seems to be highly unusual and may be hypothesized on the basis of corroborating data from behavioral observations, scent gland anatomy and secretion chemistry as follows: Enteric fluid is considered to be directed towards the ozopores via cuticular grooves in the surface of the coxapophyses of legs I. Then, the fluid is sucked into the anterior part of the scent gland reservoirs by the action of dorsal dilator muscles that widen the reservoir and produce a short‐term negative pressure. After dilution/solution of the naphthoquinone‐rich scent gland contents, a secretion‐loaded fluid is thought to be discharged with the help of transversal compressor muscles. This is the first detailed study on the functional anatomy of scent glands and the mechanisms of secretion discharge in the Dyspnoi. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.