Academic literature on the topic 'Gnathostomes'
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Journal articles on the topic "Gnathostomes"
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Sansom, Robert S., Sarah E. Gabbott, and M. A. Purnell. "Unusual anal fin in a Devonian jawless vertebrate reveals complex origins of paired appendages." Biology Letters 9, no. 3 (2013): 20130002. http://dx.doi.org/10.1098/rsbl.2013.0002.
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Jawed vertebrates (gnathostomes) have undergone radical anatomical and developmental changes in comparison with their jawless cousins (cyclostomes). Key among these is paired appendages (fins, legs and wings), which first evolved at some point on the gnathostome stem. The anatomy of fossil stem gnathostomes is, therefore, fundamental to our understanding of the nature and timing of the origin of this complex innovation. Here, we show that Euphanerops , a fossil jawless fish from the Devonian, possessed paired anal-fin radials, but no pectoral or pelvic fins. This unique condition occurs at an early stage on the stem-gnathostome lineage. This condition, and comparison with the varied condition of paired fins in other ostracoderms, indicates that there was a large amount of developmental plasticity during this episode—rather than a gradual evolution of this complex feature. Apparently, a number of different clades were exploring morphospace or undergoing multiple losses.
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Chai, Jong-Yil, Bong-Kwang Jung, Keon Hoon Lee, et al. "Infection Status of Gnathostoma spinigerum Larvae in Asian Swamp Eels, Monopterus albus, Purchased from Local Markets in Cambodia." Korean Journal of Parasitology 58, no. 6 (2020): 695–99. http://dx.doi.org/10.3347/kjp.2020.58.6.695.
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Present study was performed to know the infection status of <i>Gnathostoma</i> sp. larvae in swamp eels from Cambodia. We purchased total 30 Asian swamp eels, <i>Monopterus albus</i>, from local markets in Pursat and Takeo Provinces and Phnom Penh on May and November 2017 and May 2018. All collected eels were transferred to our laboratory with ice and each of them was examined by artificial digestion method. A total of 15 larval gnathostomes (1-5 larvae) were detected from 55.6% (5/9) swamp eels in Pursat Province. No larval gnathostomes were found in 21 swamp eels in Takeo Province and Phnom Penh. The advanced third-stage larvae (AdL<sub>3</sub>) detected were 2.575-3.825 (3.250) mm in length and 0.375-0.425 (0.386) mm in width. They had the characteristic head bulb (av. 0.104×0.218 mm) with 4 rows of hooklets, long muscular esophagus (1.048 mm), and 2 pairs of cervical sacs (0.615 mm). The number of hooklets in 4 rows on the head bulb was 41, 44, 47, and 50. In scanning electron microscopy, characteristic features were 4 rows of hooklets on the head bulb, cervical papillae, tegumental spines regularly arranged in transverse striations, and anus. The larval gnathostomes were identified as AdL<sub>3</sub> of <i>Gnathostoma spinigerum</i> based on the morphological characters. By the present study, it has been confirmed that <i>G. spinigerum</i> larvae are infected in Asian swamp eels, <i>M. albus</i>, in Pursat Province, Cambodia.
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Maisey, John G. "Gnathostomes (Jawed Vertebrates)." Short Courses in Paleontology 7 (1994): 38–56. http://dx.doi.org/10.1017/s2475263000001252.
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All living organisms possess mechanisms for obtaining nutrition. Many invertebrates also possess movable mouthparts capable of capturing prey or particulate food (e.g., polychaetes, cephalopods, arthropods and echinoderms). All living vertebrates have specialized mouthparts, and as far as we know all fossil agnathans had them also, but movable jaws supported by an internal skeleton are absent in living and fossil agnathans.
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Chai, Jong-Yil, Bong-Kwang Jung, Jin-Youp Ryu, et al. "Larval Gnathostomes and Spargana in Chinese Edible Frogs, Hoplobatrachus rugulosus, from Myanmar: Potential Risk of Human Infection." Korean Journal of Parasitology 58, no. 4 (2020): 467–73. http://dx.doi.org/10.3347/kjp.2020.58.4.467.
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Chinese edible frogs, Hoplobatrachus rugulosus, were examined to estimate the potential risks of human gnathostomiasis and sparganosis in Myanmar. A total of 20 frogs were purchased in a local market of Yangon and examined with naked eyes and the artificial digestion method after skin peeling in June 2018 and June 2019. Larvae of gnathostomes and Spirometra (=spargana) were detected in 15 (75.0%) and 15 (75.0%) frogs with average intensities of 10.5 and 6.3 larvae per infected frog, respectively. Gnathostome larvae were 2.75-3.80 (av. 3.30) mm long and 0.29-0.36 (0.33) mm wide. They had a characteristic head bulb with 4 rows of hooklets, a muscular long esophagus, and 2 pairs of cervical sac. The mean number of hooklets were 41, 44, 47, and 50 on the 1st, 2nd, 3rd, and 4th row, respectively. Collected spargana were actively moving, particularly with the scolex part, and have ivory-white color and variable in size. Conclusively, it has been first confirmed that Chinese edible frogs, H. rugulosus, are highly infected with larval gnathostomes and spargana in this study. Consuming these frogs is considered a potential risk of human gnathostomiasis and sparganosis in Myanmar.
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Zhu, Min, Xiaobo Yu, Brian Choo, Junqing Wang, and Liantao Jia. "An antiarch placoderm shows that pelvic girdles arose at the root of jawed vertebrates." Biology Letters 8, no. 3 (2012): 453–56. http://dx.doi.org/10.1098/rsbl.2011.1033.
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Almost all gnathostomes or jawed vertebrates (including osteichthyans, chondrichthyans, ‘acanthodians’ and most placoderms) possess paired pectoral and pelvic fins. To date, it has generally been believed that antiarch placoderms (extinct armoured jawed fishes from the Silurian–Devonian periods) lacked pelvic fins. The putative absence of pelvic fins is a key character bearing on the monophyly or paraphyly of placoderms. It also has far-reaching implications for studying the sequence of origin of pelvic girdles versus that of movable jaws in the course of vertebrate evolution. Parayunnanolepis xitunensis represents the only example of a primitive antiarch with extensive post-thoracic preservation, and its original description has been cited as confirming the primitive lack of pelvic fins in early antiarchs. Here, we present a revised description of Parayunnanolepis and offer the first unambiguous evidence for the presence of pelvic girdles in antiarchs. As antiarchs are placed at the base of the gnathostome radiation in several recent studies, our finding shows that all jawed vertebrates (including antiarch placoderms) primitively possess both pectoral and pelvic fins and that the pelvic fins did not arise within gnathostomes at a point subsequent to the origin of jaws.
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Kuratani, Shigeru, Yoshiaki Nobusada, Naoto Horigome, and Yasuyo Shigetani. "Embryology of the lamprey and evolution of the vertebrate jaw: insights from molecular and developmental perspectives." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 356, no. 1414 (2001): 1615–32. http://dx.doi.org/10.1098/rstb.2001.0976.
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Evolution of the vertebrate jaw has been reviewed and discussed based on the developmental pattern of the Japanese marine lamprey, Lampetra japonica . Though it never forms a jointed jaw apparatus, the L. japonica embryo exhibits the typical embryonic structure as well as the conserved regulatory gene expression patterns of vertebrates. The lamprey therefore shares the phylotype of vertebrates, the conserved embryonic pattern that appears at pharyngula stage, rather than representing an intermediate evolutionary state. Both gnathostomes and lampreys exhibit a tripartite configuration of the rostral–most crest–derived ectomesenchyme, each part occupying an anatomically equivalent site. Differentiated oral structure becomes apparent in post–pharyngula development. Due to the solid nasohypophyseal plate, the post–optic ectomesenchyme of the lamprey fails to grow rostromedially to form the medial nasal septum as in gnathostomes, but forms the upper lip instead. The gnathostome jaw may thus have arisen through a process of ontogenetic repatterning, in which a heterotopic shift of mesenchyme–epithelial relationships would have been involved. Further identification of shifts in tissue interaction and expression of regulatory genes are necessary to describe the evolution of the jaw fully from the standpoint of evolutionary developmental biology.
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Pose-Méndez, Sol, Isabel Rodríguez-Moldes, Eva Candal, Sylvie Mazan, and Ramón Anadón. "A Developmental Study of the Cerebellar Nucleus in the Catshark, a Basal Gnathostome." Brain, Behavior and Evolution 89, no. 1 (2017): 1–14. http://dx.doi.org/10.1159/000453654.
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The output of the cerebellar cortex is mainly released via cerebellar nuclei which vary in number and complexity among gnathostomes, extant vertebrates with a cerebellum. Cartilaginous fishes, a basal gnathostome lineage, show a conspicuous, well-organized cerebellar nucleus, unlike ray-finned fishes. To gain insight into the evolution and development of the cerebellar nucleus, we analyzed in the shark Scyliorhinus canicula (a chondrichthyan model species) the developmental expression of several genes coding for transcription factors (ScLhx5,ScLhx9,ScTbr1, and ScEn2) and the distribution of the protein calbindin, since all appear to be involved in cerebellar nuclei patterning in other gnathostomes. Three regions (subventricular, medial or central, and lateral or superficial) became recognizable in the cerebellar nucleus of this shark during development. Present genoarchitectonic and neurochemical data in embryos provide insight into the origin of the cerebellar nucleus in chondrichthyans and support a tripartite mediolateral organization of the cerebellar nucleus, as previously described in adult sharks. Furthermore, the expression pattern of ScLhx5,ScLhx9, and ScTbr1 in this shark, together with that of markers of proliferation, migration, and early differentiation of neurons, is compatible with the hypothesis that, as in mammals, different subsets of cerebellar nucleus neurons are originated from progenitors of 2 different sources: the ventricular zone of the cerebellar plate and the rhombic lip. We also present suggestive evidence that Lhx9 expression is involved in cerebellar nuclei patterning early on in gnathostome evolution, rather than representing an evolutionary innovation of the dentate nucleus in mammals, as previously hypothesized.
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Gutierrez-Mazariegos, Juliana, Eswar Kumar Nadendla, Romain A. Studer, et al. "Evolutionary diversification of retinoic acid receptor ligand-binding pocket structure by molecular tinkering." Royal Society Open Science 3, no. 3 (2016): 150484. http://dx.doi.org/10.1098/rsos.150484.
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Whole genome duplications (WGDs) have been classically associated with the origin of evolutionary novelties and the so-called duplication–degeneration–complementation model describes the possible fates of genes after duplication. However, how sequence divergence effectively allows functional changes between gene duplicates is still unclear. In the vertebrate lineage, two rounds of WGDs took place, giving rise to paralogous gene copies observed for many gene families. For the retinoic acid receptors (RARs), for example, which are members of the nuclear hormone receptor (NR) superfamily, a unique ancestral gene has been duplicated resulting in three vertebrate paralogues: RARα, RARβ and RARγ. It has previously been shown that this single ancestral RAR was neofunctionalized to give rise to a larger substrate specificity range in the RARs of extant jawed vertebrates (also called gnathostomes). To understand RAR diversification, the members of the cyclostomes (lamprey and hagfish), jawless vertebrates representing the extant sister group of gnathostomes, provide an intermediate situation and thus allow the characterization of the evolutionary steps that shaped RAR ligand-binding properties following the WGDs. In this study, we assessed the ligand-binding specificity of cyclostome RARs and found that their ligand-binding pockets resemble those of gnathostome RARα and RARβ. In contrast, none of the cyclostome receptors studied showed any RARγ-like specificity. Together, our results suggest that cyclostome RARs cover only a portion of the specificity repertoire of the ancestral gnathostome RARs and indicate that the establishment of ligand-binding specificity was a stepwise event. This iterative process thus provides a rare example for the diversification of receptor–ligand interactions of NRs following WGDs.
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Root, Zachary D., Claire Gould, Margaux Brewer, David Jandzik, and Daniel M. Medeiros. "Comparative Approaches in Vertebrate Cartilage Histogenesis and Regulation: Insights from Lampreys and Hagfishes." Diversity 13, no. 9 (2021): 435. http://dx.doi.org/10.3390/d13090435.
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Jawed vertebrates (gnathostomes) have been the dominant lineage of deuterostomes for nearly three hundred fifty million years. Only a few lineages of jawless vertebrates remain in comparison. Composed of lampreys and hagfishes (cyclostomes), these jawless survivors are important systems for understanding the evolution of vertebrates. One focus of cyclostome research has been head skeleton development, as its evolution has been a driver of vertebrate morphological diversification. Recent work has identified hyaline-like cartilage in the oral cirri of the invertebrate chordate amphioxus, making cyclostomes critical for understanding the stepwise acquisition of vertebrate chondroid tissues. Our knowledge of cyclostome skeletogenesis, however, has lagged behind gnathostomes due to the difficulty of manipulating lamprey and hagfish embryos. In this review, we discuss and compare the regulation and histogenesis of cyclostome and gnathostome skeletal tissues. We also survey differences in skeletal morphology that we see amongst cyclostomes, as few elements can be confidently homologized between them. A recurring theme is the heterogeneity of skeletal morphology amongst living vertebrates, despite conserved genetic regulation. Based on these comparisons, we suggest a model through which these mesenchymal connective tissues acquired distinct histologies and that histological flexibility in cartilage existed in the last common ancestor of modern vertebrates.
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Zakon, Harold H., Weiming Li, Nisha E. Pillai, et al. "Voltage-gated sodium channel gene repertoire of lampreys: gene duplications, tissue-specific expression and discovery of a long-lost gene." Proceedings of the Royal Society B: Biological Sciences 284, no. 1863 (2017): 20170824. http://dx.doi.org/10.1098/rspb.2017.0824.
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Studies of the voltage-gated sodium (Nav) channels of extant gnathostomes have made it possible to deduce that ancestral gnathostomes possessed four voltage-gated sodium channel genes derived from a single ancestral chordate gene following two rounds of genome duplication early in vertebrates. We investigated the Nav gene family in two species of lampreys (the Japanese lamprey Lethenteron japonicum and sea lamprey Petromyzon marinus ) (jawless vertebrates—agnatha) and compared them with those of basal vertebrates to better understand the origin of Nav genes in vertebrates. We noted six Nav genes in both lamprey species, but orthology with gnathostome (jawed vertebrate) channels was inconclusive. Surprisingly, the Nav2 gene, ubiquitously found in invertebrates and believed to have been lost in vertebrates, is present in lampreys, elephant shark ( Callorhinchus milii ) and coelacanth ( Latimeria chalumnae ). Despite repeated duplication of the Nav1 family in vertebrates, Nav2 is only in single copy in those vertebrates in which it is retained, and was independently lost in ray-finned fishes and tetrapods. Of the other five Nav channel genes, most were expressed in brain, one in brain and heart, and one exclusively in skeletal muscle. Invertebrates do not express Nav channel genes in muscle. Thus, early in the vertebrate lineage Nav channels began to diversify and different genes began to express in heart and muscle.
Dissertations / Theses on the topic "Gnathostomes"
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Hill, Jennifer Janet. "Evolution of the lower jaw of gnathostomes." Thesis, University of Bristol, 2018. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.743051.
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Brazeau, Martin D. "Endocranial Morphology and Phylogeny of Palaeozoic Gnathostomes (Jawed Vertebrates)." Doctoral thesis, Uppsala universitet, Evolutionär organismbiologi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9360.
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Gnathostomes, or jawed vertebrates, make up the overwhelming majority of modern vertebrate diversity. Among living vertebrates, they comprise the chondrichthyans (“cartilaginous fishes” such as sharks, skates, rays, chimaeras) and the osteichthyans (“bony fishes” or bony vertebrates, inclusive of tetrapods). Gnathostomes appear to have originated in the early Palaeozoic Era, but their early fossil record is fairly scant. The best fossils appear first in the Late Silurian and Devonian periods. Much of gnathostome diversity owes to unique adaptations in the internal skeleton of their head (the endocranium). The endocranium is composed of the braincase, jaws, hyoid arch, and branchial arches, which sometimes fossilise when they are composed of bone or calcified cartilage. The purpose of this thesis is to describe and compare the fossilised cranial endoskeletons of a variety of different Palaeozoic gnathostomes. The objective is to test current conceptions of gnathostome interrelationships (i.e. phylogeny) and infer aspects of key morphological transformations that took place during the evolution of Palaeozoic members of this group. Two key areas are examined: the morphology and interrelationships of Palaeozoic gnathostomes and the morphology of the visceral arches in sarcopterygian fishes. New data on the visceral arches are described from the stem tetrapods Panderichthys and rhizodontids. These provide insight into the sequence of character acquisition leading to the tetrapod middle ear. Panderichthys shows key features of the tetrapod middle ear chamber were established prior to the origin fo digited limbs. New morphological data are described from the “acanthodian” fish Ptomacanthus. Ptomacanthus provides only the second example of a well-preserved braincase from any member of this group. It shows dramatic differences from that of its counterpart, Acanthodes, providing new evidence for acanthodian paraphyly. New interpretations of basal gnathostome and osteichthyan phylogeny are presented, challenging or enriching existing views of these problems.
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Pradel, Alan. "Relations phylogénétiques des groupes majeurs de chondrichthyens paléozoïques et radiation des premiers gnathostomes : étude par microtomographie de l'anatomie interne du neurocrâne." Paris, Muséum national d'histoire naturelle, 2009. http://www.theses.fr/2009MNHN0011.
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Les gnathostomes actuels comprennent deux clades majeurs, les chondrichthyens, ou “poissons cartilagineux”, et les ostéichthyens, ou poissons osseux et tétrapodes. Les chondrichthyens sont représentés par deux clades, les Elasmobranchii (requins, raies) et les Holocephali (chimères). Les holocéphales actuels ne représentent qu’environ 4% des espèces de chondrichthyens, mais au Carbonifère (entre 360 et 300 Ma environ), une forte radiation des chondrichthyens a conduit à une diversité plus importante de taxa dont on suppose qu’ils leur sont proches. Les relations de parenté entre ces formes et les deux clades actuels de chondrichthyens, ainsi qu’entre les groupes majeurs de gnathostomes paléozoïques (acanthodiens, placodermes, chondrichthyens et ostéichthyens) demeurent cependant conflictuelles. Les caractères neurocrâniens des chondrichthyens actuels et fossiles n’ont été que peu étudiés jusqu’à présent, et les différentes récentes analyses phylogénétiques n’en considèrent qu’un faible nombre. Le matériel d’étude de cette thèse comporte des neurocrânes extraordinairement bien conservés en trois dimensions de deux taxa très différents du Carbonifère supérieur du Kansas et de l’Oklahoma (USA). Ces fossiles ont été étudiés grâce à des techniques d’acquisition par microtomographie assistée par ordinateur, notamment en utilisant le rayonnement synchrotron avec contraste de phase (holotomographie). Une analyse phylogénétique se fondant uniquement sur des caractères neurocrâniens et incluant plusieurs chondrichthyens paléozoïques et actuels, un acanthodien, un placoderme et un osteichthyen paléozoïques a été réalisée. Il ressort de ces études qu’un des deux taxa, les Sibyrhynchidae, représente une famille d’inioptérygiens proche des holocéphales actuels, pour lesquels il n’existait pas jusqu’à présent de représentant paléozoïques aussi bien conservés, contrairement aux élasmobranches. Ceci permet donc d’avoir à disposition des éléments permettant des études comparatives de l’anatomie du neurocrâne pour les représentants paléozoïques des deux principaux clades de chondrichthyens. L’autre taxon d’étude est représenté par un neurocrâne morphologiquement proche de celui des Symmoriiformes. Cependant, plusieurs caractéristiques rappellent celles qui sont présentes dans une autre famille d’inioptérygiens, les Iniopterygidae, et les relations de parenté entre les inioptérygiens, les Symmoriiformes et les holocéphales sont donc discutées. Les nouvelles techniques de microtomographie assistée par ordinateur se révèlent être de puissant outils afin d’étudier ces taxa. Grâce à elles, et notamment grâce à l’holotomographie, un possible cas de conservation exceptionnelle par phosphatisation authigénique microbienne du cerveau d’un des inioptérygiens a été décrit, et ceci ouvre la voie à de futurs travaux paléoneuroanatomiques<br>Recent gnathostomes are comprised of two major clades, the chondrichthyans, or cartilaginous fishes, and osteichthyans, or bony fishes and tetrapods. The chondrichthyans are represented by two clades, the Elasmobranchii (sharks, rays and skates) and Holocephali (chimaeroids). Modern holocephalans only represent about 4% of the total chondrichthyan species, but an important radiation of chondrichthyans took place in the Carboniferous (360-300 Ma), and generated an important diversity of taxa that are considered as related to extant holocephalans. Nevertheless, the relationships between these taxa and the two extant chondrichthyan clades, and even to other major extinct or extant Palaeozoic gnathostome taxa (acanthodians, placoderms, chondrichthyans, and osteichthyans), are still controversed. The neurocranial characters of extant and fossil chondrichthyans have been poorly studied until now, and recent phylogenetic analyses only consider few of them, because of their anatomical complexity, their a priori presumed evolutionary conservatism, the absence of clear landmarks for defining them, and their generally poor preservation in fossils. The material studied here, from the Upper Carboniferous of Kansas and Oklahoma (USA), consists of neurocrania, which are remarkably well preserved in three dimensions, and belong to two widely different taxa. These fossils were studied by means of computed microtomography scanning using X ray and synchrotron radiation X ray with phase contrast. A phylogenetic analysis, based on neurocranial characters only and including some other paleozoic and modern chondrichthyans taxa, and Palaeozoic acanthodian, placoderm and osteichthyan species, was performed. The result is that one of the two taxa studied here belongs to the iniopterygian family Sibyrhynchidae and is most closely related to the extant holocephalans. No other three-dimensionally preserved skull of any fossil holocephalan was known to date, contrary to fossil elasmobranchs. This provides means for a comparative study of skull anatomy in Palaeozoic representatives of the main two chondrichthyan clades. The other taxon studied here possesses a neurocranium which is morphologically closest to that of the Symmoriiformes. Nevertheless, many of its features also recall those of the Iniopterygidae, the other iniopterygian family, and the relationship between the iniopterygians, Symmoriiformes, and holocephalans are therefore discussed. The neurocranium appears as providing significant phylogenetic signals that are relevant to the characterization of the major chondrichthyan clades, even in the Paleozoic. Yet the deep relationships between the major clades of gnathostomes are still relatively controversial, and further investigation of three-dimensionally preserved braincases of various early gnathostomes, notably placoderms and acanthodians is needed for providing a clear-cut pattern of the morphotypic gnathostome braincase. The new techniques of computed microtomography scanning appears as powerful tools for studying these taxa. Thanks to these new techniques, notably Synchrotron Radiation holotomography, a probable case of exceptional preservation of the brain due to microbially induced authigenic phosphatization is described in one of the iniopterygian specimens, and points to future paleo-neuroanatomical investigations
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Sauka-Spengler, Tatjana. "Évolution structurale et fonctionnelle des homéogènes de la classe orthodenticle chez les gnathostomes." Paris 7, 2002. http://www.theses.fr/2002PA077173.
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Castiello, Marco. "Neurocranial anatomy of three unusual placoderms revealed by computed tomography scanning, and their implications for early gnathostomes evolution." Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/62621.
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Placoderms are the only known stem-group jawed vertebrates with jaws and their phylogenetic relationships have become central to the question of how gnathostomes evolved. Among placoderms, petalichthyids and "acanthothoracids" have taken a pivotal position in the debate on placoderm paraphyly, owing to their similarities with the jawless outgroups of jawed vertebrates. Nevertheless, their endocranial anatomy is still poorly known, preventing a thorough comparative analysis with the other early gnathostomes. In this thesis, I present the neurocranial anatomy of three exceptionally preserved placoderms, the petalichthyids Shearsbyaspis and Ellopetalichthys, and the "acanthothoracid" Kolymaspis. Using X-ray computed microtomography, I generated three-dimensional reconstructions of their endocranial surfaces, orbital walls, and cranial endocavity. The investigation of the endocranial anatomy of Shearsbyaspis revealed a combination of both derived and plesiomorphic characters never observed before in a placoderm, particularly in its orbital morphology and palatal architecture. Ellopetalichthys provided new evidence to help understanding the functional morphology and evolution of the inner ear and neck articulation in petalichthyids and early jawed vertebrates. Kolymaspis is revealed as an intermediate morphology between long- and short-nosed "acanthothoracids", suggesting that placoderms with similar orbitonasal anatomy might represent a highly specialized morphology rather than being plesiomorphic for jawed gnathostomes. With the aim of testing competing hypothesis on placoderm relationships, I performed different phylogenetic analyses on a new dataset comprising a wide range of early gnathostomes. Parsimony and Bayesian analyses resulted in competing hypotheses regarding placoderm monophyly and we compared the strengths and weaknesses of competing scenarios of placoderm relationships. Placoderms monophyly may indicate new scenarios for the early evolution of jawed vertebrates, implying a primitive architecture similar to those of early arthrodires, maxillate "placoderms" and bony fishes. Similarities between jawless fishes and certain placoderms may instead represent convergent adaptations.
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Véran, Monette. "Apports des Actinoptérygiens du Trias inférieur du Spitsberg à la connaissance de l'endosquelette de la région buccale des poissons Gnathostomes." Paris 7, 1989. http://www.theses.fr/1989PA077122.
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On etudie l'evolution des relations machoires-endocrane chez les gnathostomes d'apres la decouverte chez les chondrosteens fossiles d'un os labial jouant le role d'une poulie pour le muscle adducteur de la mandibule. Une analyse cladistique est effectuee pour situer la position phyletique de plusieurs groupes d'actinopterygiens
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Barere, Brigitte. "La gnathostomose oculaire." Bordeaux 2, 1989. http://www.theses.fr/1989BOR25087.
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Plouhinec, Jean-Louis. "Etude de l'évolution de familles de gènes à homéodomaine chez les vertébrés : Analyse comparative des familles de gènes à homéodomaine Otx et Emx chez les gnathostomes, mise en place d'approches phylogénomiques et application à la recherche du gène divergent Not chez les mammifères." Paris 11, 2005. http://www.theses.fr/2005PA11T017.
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CAUCHY, ANNE. "Un cas de gnathostomose humaine revelee par un syndrome de larva migrans cutanee : revue de la litterature." Angers, 1988. http://www.theses.fr/1988ANGE1088.
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Vaz, Pato Osorio Joana. "Evolution du cerveau antérieur: "patterning" et regionalisation du cerveau de lamproie en développement." Paris 11, 2007. http://www.theses.fr/2007PA112121.
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Ce travail porte sur l’étude des mécanismes de spécification et d’organisation génétique du cerveau chez la lamproie. Les résultats principaux sont les suivants : (1) l’expression des gènes Lhx et Pax chez l’embryon de lamproie révèle un grand degré de conservation des mécanismes de « patterning » du cerveau entre cyclostomes et gnathostomes. Néanmoins, quelques différences importantes ont été observées, particulièrement au niveau du télencéphale. Ces différences sont probablement corrélées avec les changements majeurs subis par cette région au moment de la transition cyclostome/gnathostome ; (2) l'analyse de l’expression des gènes Lhx et son interprétation montrent que le cerveau antérieur de lamproie présente une organisation prosomérique évidente. Cette organisation est ainsi un caractère propre aux vertébrés ; (3) l'analyse de l'expression du gène LfHh met en évidence une possible origine moléculaire de cette organisation neuromérique du cerveau ; (4) en outre, l'expression d’au moins un de ces gènes Lhx persiste tout au long de la période larvaire (non-embryonnaire), ce qui montre l’utilité de ces gènes comme marqueurs pour suivre le développement et la morphogénèse du cerveau au cours du temps. Nous avons ensuite criblé une librairie d'ADN génomique de lamproie, visant à identifier des cosmides contenant le gène Hh. Les résultats mettent en évidence la possibilité de l'existence de deux gènes Hedgehog chez la lamproie. Ces résultats ouvrent une nouvelle vision sur l'évolution de cette famille de gènes chez les chordés<br>This work was focused on the study of the genetic specification and organisation of the developing lamprey brain. By RT-PCR cloning and in situ hybridisation we were able to isolate and study the expression pattern of genes from the LIM-homeobox (Lhx), Pax and Hedgehog families in the embryonic lamprey brain. The main results are as follows: (1) Lhx and Pax genes reveal strikingly similar forebrain and hindbrain patterning between agnathans and gnathostomes. Some important differences are nevertheless observed, especially at the level of the telencephalon, a region where major changes took place at the cyclostome/gnathostome transition; (2) Expression analysis of Lhx genes and its interpretation shows that the lamprey forebrain presents a clear prosomeric organisation, which is thus a truly vertebrate character; (3) Analysis of the LfHh gene expression reveals the possible molecular origin of this neuromeric brain pattern; (4) Finally, Lhx gene expression persists through the larval (non-embryonic) period, making these genes useful markers to follow brain development and morphogenesis. We have screened a cosmid genomic DNA library aiming at identifying cosmids containing the Hh gene. The results raise the possibility of the existence of two Hedgehog genes in lamprey. A preliminary phylogenetic analysis suggests an independent duplication of the lamprey Hedgehog genes within the Sonic/Indian group. These findings open a new vision on the evolution of this gene family within chordates. Keywords Brain; Evolution; Agnathan; Gnathostome; Lamprey; Dogfish; Gene expression; Patterning; Neuromere; Forebrain; LIM-homeobox; Pax; Hedgehog; Gene duplication; Enhancer
Books on the topic "Gnathostomes"
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Kiefer, F. Crustacea Copepoda, 2: Cyclopoida Gnathostoma. de Gruyter GmbH, Walter, 2020.
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Lamprey-like gills in a gnathostome-related Devonian jawless vertebrate. Nature 440, 1183-1185, 2006.
Find full textBook chapters on the topic "Gnathostomes"
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Lingham-Soliar, Theagarten. "The Earliest Jawed Vertebrates, the Gnathostomes." In The Vertebrate Integument Volume 1. Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-53748-6_3.
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Sanpool, O., P. M. Intapan, David Blair, Yukifumi Nawa, and W. Maleewong. "Gnathostoma." In Handbook of Foodborne Diseases. CRC Press, 2018. http://dx.doi.org/10.1201/b22030-80.
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Ringelmann, R., and Beate Heym. "Gnathostoma spinigerum." In Parasiten des Menschen. Steinkopff, 1991. http://dx.doi.org/10.1007/978-3-642-85397-5_47.
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Mehlhorn, Heinz. "Gnathostoma Species." In Encyclopedia of Parasitology. Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-43978-4_3916.
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Mehlhorn, Heinz. "Gnathostoma Species." In Encyclopedia of Parasitology. Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-642-27769-6_3916-1.
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Epple, August, and Jack E. Brinn. "Ontogeny of the Gnathostome Pancreas Tissues." In The Comparative Physiology of the Pancreatic Islets. Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-83182-9_3.
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Mehlhorn, Heinz. "Gnathostoma Species in Comparison, Rare Human Cases." In Encyclopedia of Parasitology. Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-43978-4_4981.
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Mehlhorn, Heinz. "Gnathostoma Species in Comparison, Rare Human Cases." In Encyclopedia of Parasitology. Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-642-27769-6_4981-1.
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"30. Vertebrates (Agnathans and Gnathostomes)." In The Great Ordovician Biodiversification Event. Columbia University Press, 2004. http://dx.doi.org/10.7312/webb12678-031.
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Striedter, Georg F., and R. Glenn Northcutt. "The Origin of Jaws and Paired Fins." In Brains Through Time. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780195125689.003.0003.
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Between 450 and 500 million years ago, some vertebrates evolved paired fins and jaws, which made them more efficient swimmers and fiercer predators. These jawed vertebrates (i.e., gnathostomes) diversified in the Devonian period, but most died out during the end-Devonian mass extinction. The surviving gnathostomes had a more complex vestibular apparatus than their jawless ancestors, an expanded set of olfactory receptor genes, and vomeronasal receptors. A major innovation in the brains of gnathostomes was the emergence of a cerebellum that is distinct from the cerebellum-like areas found in all vertebrates. The telencephalon of early vertebrates processed primarily olfactory information, but this olfactory dominance was independently reduced in three later lineages, namely in cartilaginous fishes, ray-finned fishes, and tetrapods. In concert with the reduction in olfactory dominance, these lineages enlarged their telencephalon, relative to other brain regions, and evolved a telencephalic “dorsal pallium” that receives non-olfactory sensory information from the diencephalon.