Добірка наукової літератури з теми "Scolecophidia"

The suborder Serpentes is divided into 2 infraorders, Scolecophidia and Alethinophidia, which diverged at an early stage of snake diversification. In this study, we examined karyotypes of 4 scolecophidian species (Letheobia simonii, Xerotyphlops vermicularis, Indotyphlops braminus, and Myriopholis macrorhyncha) and performed FISH with 18S-28S rDNA as well as microchromosomal and Z chromosome-linked genes of Elaphe quadrivirgata (Alethinophidia) to investigate the karyotype evolution in the scolecophidian lineage. Diploid chromosome numbers of X. vermicularis and L. simonii were 30 (16 macrochromosomes and 14 microchromosomes) and 32 (16 macrochromosomes and 16 microchromosomes), respectively. The karyotype of a female M. macrorhyncha consisted of 15 macrochromosomes and 19 microchromosomes, including a heterochromatic microchromosome, indicating the presence of a heteromorphic chromosome pair. E. quadrivirgata Z-linked genes mapped to chromosome 4 of M. macrorhyncha, not to the heteromorphic pair. Therefore, M. macrorhyncha may have differentiated ZW sex chromosomes which are not homologous to those of E. quadrivirgata. One of the E. quadrivirgata microchromosomal genes mapped to the terminal region of chromosome 4q in X. vermicularis, suggesting that fusions between microchromosomes and macrochromosomes occurred in this species. rDNA was localized in different macrochromosomal pairs in the 2 diploid scolecophidian snakes examined here, whereas the gene location in a microchromosomal pair was conserved in 5 alethinophidian species examined. These results might imply the occurrence of chromosome fusions in the scolecophidian lineages. In I. braminus, a unique parthenogenetic snake with a triploid karyotype (21 macrochromosomes and 21 microchromosomes), morphological heteromorphisms were identified in chromosomes 1 and 7. Such heteromorphisms in 2 chromosomes were also observed in individuals from distant locations in the broad distribution range of this species, suggesting that the heteromorphisms were fixed in the genome at an early stage of its speciation.

Se estudian los restos de ofidios del Mioceno terminal (MN 13) de Algora (Guadalajara, España). Se han detectado las siguientes formas, Scolecophidia indet., Elaphe algorensis sp. nov. e Hispanophis coronelloideus gen. sp, nov. (Colubridae), Naja iberica sp. nov. (Elapidae), y Viperidae indet. Esta asociación faunística no es comparable a las restantes faunas de ofidios conocidas de otras localidades europeas, e incluye tanto formas endémicas (Colubridae), como especies evolutivamente emparentadas con formas norteafricanas (Naja iberica sp. nov., quizás también las víboras).

Les scolécophidiens (Scolecophidia) ont longtemps été négligés des systématiciens, les rares études moléculaires ont montré le manque de fiabilité des caractères morphologiques en phylogénie et une importante diversité génétique au sein d'espèces morphologiques (potentielles espèces cryptiques). Nous nous sommes focalisés sur les espèces australiennes du genre Ramphotyphlops. Des approches de taxonomie intégrative ont montré que leur diversité spécifique était largement sous-estimée, en moyenne deux espèces nouvelles pour chaque décrite. La comparaison et l'analyse critique de méthodes d'estimation des temps de divergence ont été menées. Ces méthodes ont montré que des lignées tropicales et humides des scolécophidiens se sont adaptées et diversifiées suite à la formation d'une zone aride au centre de l'Australie qui a débuté il y a 20 millions d'années. Les lignées arides ont émergé plus tard, il y a 5,6 à 2,4 millions d'années, une fois que la zone aride était bien établie
The scolecophidians (Scolecophidia) have long been neglected by taxonomists and the few molecular studies have highlighted the unreliability of morphological characters in phylogenetic reconstructions and an important genetic diversity within morphological species (potential cryptic species). We focused on the Australian species of the genus Ramphotyphlops. Approaches of integrative taxonomy have shown that their species diversity was largely underestimated, around three times the number of species currently described. A comparison and critical analysis oh the main methods for estimating divergence times were conducted. These methods have shown that tropical and humid scolecophidians lineages have adapted and diversified following the differentiation of the arid zone in central Australia that began 20 millions years ago. Arid lineages emerged later, between 5,6 and 2,4 million years ago, when the arid zone was well established

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
A diversidade das serpentes é ampla, com aproximadamente três mil espécies descritas. Esta diversidade é agrupada, tanto por evidências morfológicas como moleculares, em dois clados: Alethinophidia (~2660 espécies) e Scolecophidia (~400 espécies). Comparativamente aos Alethinophidia, poucos estudos foram realizados até o momento com Scolecophidia, estudos estes dificultados tanto pelos hábitos furtivos como pela raridade destas serpentes. O clado Scolecophidia é reconhecido por agrupar serpentes pequenas, com olhos vestigiais e hábito subterrâneo. Atualmente são reconhecidas cinco famílias: Anomalepididae, Gerrhopilidae, Leptotyphlopidae, Xenotyphlopidade e Typhlopidae. A família Typhlopidae possui ampla distribuição, ocorrendo em todos os continentes incluindo diversas formações insulares. Dos cinco gêneros que compõem a família, o genêro Typhlops é o mais especioso, com aproximadamente 145 espécies descritas que ocupam uma variedade de hábitats, desde desertos até florestas tropicais. Na América do Sul são reconhecidas oito espécies, sendo Typhlops brongersmianus a espécie que apresenta a maior distribuição, ocorrendo em diversos domínios morfoclimáticos. Em geral, vertebrados com estilo de vida subterrâneo são de difícil observação, e muitos aspectos de sua biologia evolutiva são mal compreendidos, incluindo o modo prevalente de especiação e os padrões de diversificação, bem como a estrutura geográfica da variabilidade genética e morfológica. Sendo assim, este trabalho visa dirimir estas lacunas tendo por objetivo estudar os padrões filogeográficos e demográficos, tentando contribuir para a elucidação da história evolutiva e taxonômica de T. brongersmianus bem como compreender as relações filogenéticas desta espécie com outras congêneres que ocorrem em...
The diversity of snakes is vast, with approximately three thousand described species. This diversity is grouped by both morphological and molecular evidence, in two clades: Alethinophidia (~2660 species) and Scolecophidia (~400 species). Compared to Alethinophidia, few studies have been conducted so far with Scolecophidia, these studies hampered both by furtive habits as the rarity of these snakes. The clade Scolecophidia group is recognized by small snakes with vestigial eyes and subterranean. Currently, five families are recognized: Anomalepididae, Gerrhopilidae, Leptotyphlopidae, and Xenotyphlopidade Typhlopidae. The family Typhlopidae has a wide distribution, occurring in all continents including several island formations. Of the five genera in the family, the genre is the most specious Typhlops, with about 145 described species that occupy a variety of habitats, from deserts to tropical rainforests. In South America are recognized eight species, Typhlops brongersmianus the species with the widest distribution, occurring in various areas morphoclimatic. In general, vertebrates with underground lifestyle are difficult to observe, and many aspects of their evolutionary biology are poorly understood, including the prevalent mode of speciation and diversification patterns and the geographical structure of genetic and morphological variability. Thus, this study aims to resolve these shortcomings have been studying the phylogeographic and demographic patterns, trying to contribute to the elucidation of evolutionary history and taxonomic T. brongersmianus well as understand the phylogenetic relationships of this species with other congeners that occur in sympatry in South America To do this, we performed an extensive analysis of morphological revision through a survey of meristic and morphometric characters, totaling... (Complete abstract click electronic access below)

Orientador: Hussam El Dine Zaher
Coorientador: Sandro Luis Bonatto
Banca: Giovanna Gondim Montingelli
Banca: Nelson Jurandi da Rosa Fagundes
Resumo: A diversidade das serpentes é ampla, com aproximadamente três mil espécies descritas. Esta diversidade é agrupada, tanto por evidências morfológicas como moleculares, em dois clados: Alethinophidia (~2660 espécies) e Scolecophidia (~400 espécies). Comparativamente aos Alethinophidia, poucos estudos foram realizados até o momento com Scolecophidia, estudos estes dificultados tanto pelos hábitos furtivos como pela raridade destas serpentes. O clado Scolecophidia é reconhecido por agrupar serpentes pequenas, com olhos vestigiais e hábito subterrâneo. Atualmente são reconhecidas cinco famílias: Anomalepididae, Gerrhopilidae, Leptotyphlopidae, Xenotyphlopidade e Typhlopidae. A família Typhlopidae possui ampla distribuição, ocorrendo em todos os continentes incluindo diversas formações insulares. Dos cinco gêneros que compõem a família, o genêro Typhlops é o mais especioso, com aproximadamente 145 espécies descritas que ocupam uma variedade de hábitats, desde desertos até florestas tropicais. Na América do Sul são reconhecidas oito espécies, sendo Typhlops brongersmianus a espécie que apresenta a maior distribuição, ocorrendo em diversos domínios morfoclimáticos. Em geral, vertebrados com estilo de vida subterrâneo são de difícil observação, e muitos aspectos de sua biologia evolutiva são mal compreendidos, incluindo o modo prevalente de especiação e os padrões de diversificação, bem como a estrutura geográfica da variabilidade genética e morfológica. Sendo assim, este trabalho visa dirimir estas lacunas tendo por objetivo estudar os padrões filogeográficos e demográficos, tentando contribuir para a elucidação da história evolutiva e taxonômica de T. brongersmianus bem como compreender as relações filogenéticas desta espécie com outras congêneres que ocorrem em... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The diversity of snakes is vast, with approximately three thousand described species. This diversity is grouped by both morphological and molecular evidence, in two clades: Alethinophidia (~2660 species) and Scolecophidia (~400 species). Compared to Alethinophidia, few studies have been conducted so far with Scolecophidia, these studies hampered both by furtive habits as the rarity of these snakes. The clade Scolecophidia group is recognized by small snakes with vestigial eyes and subterranean. Currently, five families are recognized: Anomalepididae, Gerrhopilidae, Leptotyphlopidae, and Xenotyphlopidade Typhlopidae. The family Typhlopidae has a wide distribution, occurring in all continents including several island formations. Of the five genera in the family, the genre is the most specious Typhlops, with about 145 described species that occupy a variety of habitats, from deserts to tropical rainforests. In South America are recognized eight species, Typhlops brongersmianus the species with the widest distribution, occurring in various areas morphoclimatic. In general, vertebrates with underground lifestyle are difficult to observe, and many aspects of their evolutionary biology are poorly understood, including the prevalent mode of speciation and diversification patterns and the geographical structure of genetic and morphological variability. Thus, this study aims to resolve these shortcomings have been studying the phylogeographic and demographic patterns, trying to contribute to the elucidation of evolutionary history and taxonomic T. brongersmianus well as understand the phylogenetic relationships of this species with other congeners that occur in sympatry in South America To do this, we performed an extensive analysis of morphological revision through a survey of meristic and morphometric characters, totaling... (Complete abstract click electronic access below)
Mestre

Most recent phylogenetic analyses of snakes have recognized two major clades within Serpentes: Alethinophidia and Scolecophidia. Alethinophidians feed predominantly on relatively large vertebrate prey, which they transport into and through the mouth via reciprocating ratcheting movements of the toothed palatopterygoid jaw arches. In contrast, scolecophidians are small-prey specialists, feeding almost exclusively on small arthropods. In addition, these diminutive, fossorial snakes lack many of the key morphological features which underlie the feeding mechanisms of alethinophidians, such as toothed palatopterygoid jaw arches and a distensible lower jaw. However, the functional significance of these morphological differences has remained poorly understood because there have been no detailed descriptions of feeding behavior in Scolecophidia. I used magnified high-speed videography, videofluoroscopy, and standard histological and gross morphological preparations to study the functional morphology of the feeding apparatus in representatives of two families of Scolecophidia, Leptotyphlopidae and Typhlopidae. In Leptotyphlops (Leptotyphlopidae), a mandibular raking mechanism is used to capture, ingest and transport prey. In this mechanism, the toothed anterior portions of the mandibular rami are rotated medially about the intramandibular joints in a bilaterally synchronous fashion. In contrast, Typhlops and Rhinotyphlops (Typhlopidae) feed via a maxillary raking mechanism, in which asynchronous rotations of the toothed maxillae are used to drag prey into and through the mouth. Both mandibular raking and maxillary raking involve exceptionally rapid (3–5 Hz) movements of the tooth-bearing elements of the jaws, thereby facilitating the ingestion of large numbers of small prey within relatively brief periods of time.

Much of systematics done in the past was based on morphological data. One of the drawbacks of using morphological data is that in groups with conserved morphology, the diversity is often underestimated and relationships difficult to infer. One such group are the fossorial blindsnakes (superfamily Typhlopoidea, infraorder Scolecophidia). The diversity, life histories and ecology of such groups remain unexplored due to their sub-terranean and secretive habit. India has around 17 species, spanning four genera and two families. However, many of these species have not been discovered since their first descriptions, and many are suspected to be synonyms. For my PhD, I studied the diversity of the four typhlopoid genera in India, from a phylogenetic and biogeographical perspective, and attempted to understand diversification patterns within one species group, which gave rise to the Indotyphlops braminus, a blindsnake with a surprisingly cosmopolitan distribution. In the first chapter, I explore the phylogenetic positions of the four genera- Gerrhopilus, Indotyphlops, Grypotyphlops and Argyrophis, in the global phylogeny. I use a concatenated dataset of five nuclear markers to reconstruct the phylogenies using maximum likelihood and Bayesian methods. The results show that Indian typhlopoids have very diverse affiliations. Gerrhopilus is retrieved as sister to all other typhlopoids. Grypotyphlops is nested with the African genera, which corroborates its classification based on morphology. Indotyphlops was shown to be polyphyletic, with Indotyphlops porrectus being sister to all southeast Asian typhlopoids, and thus requiring a taxonomic revision. We also find an Indian radiation of Indotyphlops. Argyrophis from India is sister to the Argyrophis from southeast Asia. The second chapter looks at the biogeographic origins of the four genera. The divergence times were estimated using the concatenated five gene dataset used in the first chapter, with nine fossils used to calibrate the time-tree. The time-tree was then used for ancestral area estimation in BioGeoBEARS, implemented in R. I carried out a time stratified analysis to accommodate the dramatic changes in the position of the Indian landmass over geological time and model fitting to compare multiple dispersal and vicariance hypotheses. The best fit model invokes both dispersal and vicariance as the explanations for the current distribution of typhlopoids in India. India harbours an ancient Gondwanan group of typhlopoids as well as comparatively younger dispersals from Africa and Asia. The third chapter looks at more fine scale diversification of blindsnakes in peninsular India, particularly Indotyphlops braminus. Indotyphlops braminus is an enigmatic blindsnake that has a pan-tropical distribution, most probably due to human mediated dispersal. It is also proposed to be the only obligate parthenogenetic snake as of now. Karyotyping studies have shown Indotyphlops braminus to be triploid, which has been proposed to be a result of hybridization, and a possible cause of the parthenogenetic reproduction. I investigated the discordance between mitochondrial and nuclear phylogenies to understand whether Indotyphlops braminus is a result of hybridization between two Indian species. I also explored additional lines of evidence by looking at the discordance between gene trees and species trees and a statistical test for hybridization. The results strongly suggest that this cosmopolitan, triploid, parthenogenetic taxon is indeed a hybrid of two Indotyphlops species found in India, but it is not the true Indotyphlops braminus. This new, hybrid species, therefore, merits a taxonomic revision. The underlying theme of my thesis is understanding the origins and diversification patterns in the Indian typhlopoids at broad and fine taxonomic scales, from phylogenetic and biogeographical perspectives.