The Experts below are selected from a list of 363 Experts worldwide ranked by ideXlab platform
Ryuichiro Machida - One of the best experts on this subject based on the ideXlab platform.
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The homology of cephalic muscles and endoskeletal elements between Diplura and Ectognatha (Insecta)
Organisms Diversity & Evolution, 2016Co-Authors: Alexander Blanke, Ryuichiro MachidaAbstract:Diplura (two-pronged bristletails) are key to our understanding of hexapod head evolution. A sister group relationship with Ectognatha (=Insecta), comprising bristletails, silverfish and winged insects, is advocated in most modern studies, however, homologization of head muscles and endoskeletal elements between Diplura and Ectognatha is still lacking. Here, we present the first homologization of a number of head muscles and endoskeletal structures between Diplura and Ectognatha. A homologization of these structures is possible if a range of species, both from Japygidae and Campodeidae, are studied in order to reconstruct the potential groundplan characteristics and account for inner anatomy variations within Diplura. Japygidae and Campodeidae show differences in the origin, insertion, and presence of mandibular and maxillary muscles as well as the shape of the maxillary cardo. Taking into account recent embryological studies on the formation of the endoskeleton in Protura, Collembola and Diplura, we furthermore reconstruct the potential evolution of the endoskeleton in early Hexapoda. The tentorium is a defining feature of dicondylic insects (including Archaeognatha) while anterior and posterior cephalic invaginations (the later tentorial pits of dicondylic insects) are groundplan features of Hexapoda. Additionally, we clarify the composition of the gnathal pouches (i.e. the type of entognathy) in Diplura and Collembola. The pouches in Diplura are posteriorly separated, similar to the state encountered in Collembola. This contrasts to former studies emphasizing the differences in the ellipuran and dipluran type of entognathy.
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Spermiogenesis and sperm ultrastructure of Machilontus sp (Insecta: Archaeognatha) with phylogenetic consideration.
Micron (Oxford England : 1993), 2015Co-Authors: Pietro Paolo Fanciulli, Ryuichiro Machida, David Mercati, Romano DallaiAbstract:The sperm structure of the jumping bristletail Machilontus sp has been described. The species shares several sperm characteristics with other genera of the same order Archaeognatha. During late spermiogenesis the spermatid bends at half of its length with the two limbs closely apposed within the same plasma membrane. The sperm has a helicoidal bi-layered acrosome with a filamentous perforatorium and a long nucleus. The elongated flagellum consists of an axoneme with 9 accessory microtubules external to the 9+2, two rows of conventional mitochondria and two accessory bodies. The accessory bodies are located lateral to the axoneme and are probably responsible for the shifting of the accessory tubules in two opposite groups of 5 and 4 tubules, respectively. These sperm characteristics represent common traits of all Archaeognatha.
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Development of embryonic membranes in the silverfish Lepisma saccharina Linnaeus (Insecta: Zygentoma, Lepismatidae)
Tissue & cell, 2006Co-Authors: M. Masumoto, Ryuichiro MachidaAbstract:Development and fate of embryonic membranes in the silverfish Lepisma saccharina was examined throughout embryogenesis. The amnioserosal folds first arise as serosal folds that are completed by the later addition of the amnion from the embryo's margins as in archaeognaths. The close link between production of the amnion and formation of the folds should not be assigned to Dicondylia but to Pterygota as an autapomorphy. During fold formation, folding of embryonic membranes beneath the embryo is less extensive and the ventral cupping of the embryo plays a larger role comparable to that occurring in archaeognath embryos. In L. saccharina, the embryonic membrane pore (the amniopore) varies in its manner of closure, either by complete fusion of serosal folds or by formation of a serosal cuticular plug between them as in archaeognaths. Although, in many aspects of its embryogenesis, L. saccharina retains the primitiveness of archaeognaths, its amnioserosal folds persist and are well integrated into its embryogenesis as the amnioserosal fold-amniotic cavity system is established and as occurs in many pterygote embryos; this may be thus regarded as an autapomorphy of Dicondylia.
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Serial homology of the mandible and maxilla in the jumping bristletail Pedetontus unimaculatus Machida, based on external embryology (Hexapoda: Archaeognatha, Machilidae).
Journal of morphology, 2000Co-Authors: Ryuichiro MachidaAbstract:The development of the mandible and maxilla is examined with the scanning electron microscope in the Archaeognatha. Serial homology is discussed to elucidate the general construction of the hexapod mandible. The part comparable to the maxillary palp does not develop in the mandible. Thus, the mandible is coxopodal in origin, and not telognathic but coxognathic. The mandible proper is subdivided into two in late embryonic development, and the smaller proximal and larger distal parts are homologized with the maxillary cardo and stipes, respectively, being subcoxal and coxal in nature. The partition into the “mandibular cardo” in which the mandibular monocondyle is formed and the “mandibular stipes” is recognized as a cuticular ridge or the “mandibular basal ridge” in the postembryonic stages including the imaginal. The molar and incisor are comparable in position and homologized with the maxillary lacinia and galea, respectively. The lacinia and galea could be morphologically interpreted as being the endites of the maxillary coxae I and II, respectively, and the molar and incisor might represent the mandibular coxae I and II as their constituents or endites. J. Morphol. 245:19–28, 2000 © 2000 Wiley-Liss, Inc.
Romano Dallai - One of the best experts on this subject based on the ideXlab platform.
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Spermiogenesis and sperm ultrastructure of Machilontus sp (Insecta: Archaeognatha) with phylogenetic consideration.
Micron (Oxford England : 1993), 2015Co-Authors: Pietro Paolo Fanciulli, Ryuichiro Machida, David Mercati, Romano DallaiAbstract:The sperm structure of the jumping bristletail Machilontus sp has been described. The species shares several sperm characteristics with other genera of the same order Archaeognatha. During late spermiogenesis the spermatid bends at half of its length with the two limbs closely apposed within the same plasma membrane. The sperm has a helicoidal bi-layered acrosome with a filamentous perforatorium and a long nucleus. The elongated flagellum consists of an axoneme with 9 accessory microtubules external to the 9+2, two rows of conventional mitochondria and two accessory bodies. The accessory bodies are located lateral to the axoneme and are probably responsible for the shifting of the accessory tubules in two opposite groups of 5 and 4 tubules, respectively. These sperm characteristics represent common traits of all Archaeognatha.
Markus Friedrich - One of the best experts on this subject based on the ideXlab platform.
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molecular phylogenetics at the felsenstein zone approaching the strepsiptera problem using 5 8s and 28s rdna sequences
Molecular Phylogenetics and Evolution, 1998Co-Authors: Ui W Hwang, Diethard Tautz, Markus FriedrichAbstract:Abstract Recent efforts to reconstruct the phylogenetic position of the insect order Strepsiptera have elicited a major controversy in molecular phylogenetics. We sequenced the 5.8S rDNA and major parts of the 28S rDNA 5′ region of the strepsipteran speciesStylops melittae.Their evolutionary dynamics were analyzed together with previously published insect rDNA sequences to identify tree estimation bias risks and to explore additional sources of phylogenetic information. Several major secondary structure changes were found as being autapomorphic for the Diptera, the Strepsiptera, or the Archaeognatha. Besides elevated substitution rates a significant AT bias was present in dipteran and strepsipteran 28S rDNA which, however, was restricted to stem sites in the Diptera while also affecting single-stranded sites in the Strepsiptera. When dipteran taxa were excluded from tree estimation all methods consistently supported the placement of Strepsiptera to within the Holometabola. When dipteran taxa were included maximum likelihood continued to favor a sister-group relationship of Strepsiptera with Mecoptera while remaining methods strongly supported a sister-group relationship with Diptera. Parametric bootstrap analysis revealed maximum likelihood as a consistent estimator if rate heterogeneity across sites was taken into account. Though the position of Strepsiptera within Holometabola remains elusive, we conclude that the evolution of dipteran and strepsipteran rDNA involved similar yet independent changes of substitution parameters.
Aibing Zhang - One of the best experts on this subject based on the ideXlab platform.
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phylogenetic analyses with four new cretaceous bristletails reveal inter relationships of Archaeognatha and gondwana origin of meinertellidae
Cladistics, 2018Co-Authors: Weiting Zhang, Hu Li, Chungkun Shih, Aibing ZhangAbstract:Based on fifteen Archaeognatha (=Microcoryphia) specimens from Myanmar (Burmese) amber, including males, females and immatures, two new genera and four species, Cretaceomachilis longa sp.n., Unimeinertellus abundus gen. et sp.n., U. bellus sp.n. and Nullmeinertellus wenxuani gen. et sp.n., are described. Phylogenetic analyses of taxa in Archaeognatha were conducted using Maximum parsimony and Bayesian inference based on morphological characters and DNA sequence data. Our results confirm the phylogenetic position of the new genera, clarify the monophyly of Meinertellidae and indicate that the ‘paleo-types’ excluding Ditrigoniophthalmus are nested within the Machilidae group, but suggest that the three subfamilies within Machilidae may be artificial. The diversity of meinertellids with derived characters found from the Cretaceous indicate that the divergence time of Machilidae and Meinertellidae is much earlier than the Cretaceous. We propose the possibility that Meinertellidae might have originated on Gondwana.
Chungkun Shih - One of the best experts on this subject based on the ideXlab platform.
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phylogenetic analyses with four new cretaceous bristletails reveal inter relationships of Archaeognatha and gondwana origin of meinertellidae
Cladistics, 2018Co-Authors: Weiting Zhang, Hu Li, Chungkun Shih, Aibing ZhangAbstract:Based on fifteen Archaeognatha (=Microcoryphia) specimens from Myanmar (Burmese) amber, including males, females and immatures, two new genera and four species, Cretaceomachilis longa sp.n., Unimeinertellus abundus gen. et sp.n., U. bellus sp.n. and Nullmeinertellus wenxuani gen. et sp.n., are described. Phylogenetic analyses of taxa in Archaeognatha were conducted using Maximum parsimony and Bayesian inference based on morphological characters and DNA sequence data. Our results confirm the phylogenetic position of the new genera, clarify the monophyly of Meinertellidae and indicate that the ‘paleo-types’ excluding Ditrigoniophthalmus are nested within the Machilidae group, but suggest that the three subfamilies within Machilidae may be artificial. The diversity of meinertellids with derived characters found from the Cretaceous indicate that the divergence time of Machilidae and Meinertellidae is much earlier than the Cretaceous. We propose the possibility that Meinertellidae might have originated on Gondwana.