{"id":{"repo_id":"ghent","oai_identifier":"oai:archive.ugent.be:469133"},"canonical_url":"https://search.dev.ndltd.org/etd/ghent/oai:archive.ugent.be:469133","repository":{"repo_id":"ghent","name":"Ghent University","base_url":"https://biblio.ugent.be/oai"},"display":{"title":"Comparative and phylogenetic analysis of the early embryonic development in the phylum Nematoda","abstract":"Nematodes are excellent models to study early embryonic development, because – at least for many nematodes- eggs are transparent and the development from fertilized egg to hatched juvenile can be visualized directly under the light microscope. In a first part of this thesis a comparative analysis of the early embryonic development was done on 21 nematode species belonging to clade 6 and clades 9-12 (phylogeny of Holterman et al., 2006). Our study revealed prominent differences between nematodes. Variations include differences in cell cycle rhythms, cleavage order of the blastomeres, spatial configuration of the early embryo (based on cell-cell contacts and division angles), establishment of bilateral symmetry and the process of gastrulation. However, this diversity in early embryonic development does not result in a corresponding degree of diversity in the morphology of hatched juveniles. Thus, modifications of these early developmental mechanisms have apparently no impact on the adult morphology and are probably the result of neutral evolution. For most examined characters a large amount of intraspecific variation was observed for all species. This intraspecific variation shows that a “strict invariant” lineage, with a strict timing of cell divisions and stereotyped cell contacts in the early phase of embryonic development, is not a prerequisite to develop into a worm. Besides this intraspecific variation, coding early developmental data proved to be problematic, because of interdependency of the data, since most early developmental characters are linked in time and space. From the comparative analysis five five characters, which are potentially useful to infer phylogenetic information were distilled. In a second part of this thesis ancestral state reconstructions of these characters onto a molecular phylogeny revealed four synapomorphies. Some characters proved to have a biased evolution as they have arisen multiple times in independent lineages. Statistical tests indicate possible relationships with developmental speed and egg shape. However, further analysis on a larger number of species and the inclusion of statistical tests that account for phylogenetic relationships should reveal whether these features are due to directional selection or other constraints, or whether the occurrence of these features is due to common ancestry.","abstract_html":"Nematodes are excellent models to study early embryonic development, because – at least for many nematodes- eggs are transparent and the development from fertilized egg to hatched juvenile can be visualized directly under the light microscope. In a first part of this thesis a comparative analysis of the early embryonic development was done on 21 nematode species belonging to clade 6 and clades 9-12 (phylogeny of Holterman et al., 2006). Our study revealed prominent differences between nematodes. Variations include differences in cell cycle rhythms, cleavage order of the blastomeres, spatial configuration of the early embryo (based on cell-cell contacts and division angles), establishment of bilateral symmetry and the process of gastrulation. However, this diversity in early embryonic development does not result in a corresponding degree of diversity in the morphology of hatched juveniles. Thus, modifications of these early developmental mechanisms have apparently no impact on the adult morphology and are probably the result of neutral evolution. For most examined characters a large amount of intraspecific variation was observed for all species. This intraspecific variation shows that a “strict invariant” lineage, with a strict timing of cell divisions and stereotyped cell contacts in the early phase of embryonic development, is not a prerequisite to develop into a worm. Besides this intraspecific variation, coding early developmental data proved to be problematic, because of interdependency of the data, since most early developmental characters are linked in time and space. From the comparative analysis five five characters, which are potentially useful to infer phylogenetic information were distilled. In a second part of this thesis ancestral state reconstructions of these characters onto a molecular phylogeny revealed four synapomorphies. Some characters proved to have a biased evolution as they have arisen multiple times in independent lineages. Statistical tests indicate possible relationships with developmental speed and egg shape. However, further analysis on a larger number of species and the inclusion of statistical tests that account for phylogenetic relationships should reveal whether these features are due to directional selection or other constraints, or whether the occurrence of these features is due to common ancestry.","abstract_has_math":false,"creators":["Vangestel, Sandra"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Borgonie, G"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2008,"date_issued":"2008","date_published":"2008","updated_at":"2026-07-24T02:23:05Z","subjects":[],"languages":["und"],"rights":["info:eu-repo/semantics/openAccess"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://biblio.ugent.be/publication/469133","http://doi.org/1854/13577","https://biblio.ugent.be/publication/469133/file/4334836"],"render_values":[{"text":"https://biblio.ugent.be/publication/469133","href":"https://biblio.ugent.be/publication/469133","code":true},{"text":"http://doi.org/1854/13577","href":"http://doi.org/1854/13577","code":true},{"text":"https://biblio.ugent.be/publication/469133/file/4334836","href":"https://biblio.ugent.be/publication/469133/file/4334836","code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/1854/LU-469133","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Borgonie, G"]},{"key":"dc:creator","label":"Author","values":["Vangestel, Sandra"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2008"]},{"key":"dc:type","label":"Dc Type","values":["dissertation","info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["und"]},{"key":"dc:rights","label":"Dc Rights","values":["info:eu-repo/semantics/openAccess"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://biblio.ugent.be/publication/469133","http://hdl.handle.net/1854/LU-469133","http://doi.org/1854/13577","https://biblio.ugent.be/publication/469133/file/4334836"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Nematodes are excellent models to study early embryonic development, because – at least for many nematodes- eggs are transparent and the development from fertilized egg to hatched juvenile can be visualized directly under the light microscope. In a first part of this thesis a comparative analysis of the early embryonic development was done on 21 nematode species belonging to clade 6 and clades 9-12 (phylogeny of Holterman et al., 2006). Our study revealed prominent differences between nematodes. Variations include differences in cell cycle rhythms, cleavage order of the blastomeres, spatial configuration of the early embryo (based on cell-cell contacts and division angles), establishment of bilateral symmetry and the process of gastrulation. However, this diversity in early embryonic development does not result in a corresponding degree of diversity in the morphology of hatched juveniles. Thus, modifications of these early developmental mechanisms have apparently no impact on the adult morphology and are probably the result of neutral evolution. For most examined characters a large amount of intraspecific variation was observed for all species. This intraspecific variation shows that a “strict invariant” lineage, with a strict timing of cell divisions and stereotyped cell contacts in the early phase of embryonic development, is not a prerequisite to develop into a worm. Besides this intraspecific variation, coding early developmental data proved to be problematic, because of interdependency of the data, since most early developmental characters are linked in time and space. From the comparative analysis five five characters, which are potentially useful to infer phylogenetic information were distilled. In a second part of this thesis ancestral state reconstructions of these characters onto a molecular phylogeny revealed four synapomorphies. Some characters proved to have a biased evolution as they have arisen multiple times in independent lineages. Statistical tests indicate possible relationships with developmental speed and egg shape. However, further analysis on a larger number of species and the inclusion of statistical tests that account for phylogenetic relationships should reveal whether these features are due to directional selection or other constraints, or whether the occurrence of these features is due to common ancestry."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Comparative and phylogenetic analysis of the early embryonic development in the phylum Nematoda"]}]}],"canonical_facts":{"dc:contributor":["Borgonie, G"],"dc:creator":["Vangestel, Sandra"],"dc:date":["2008"],"dc:description":["Nematodes are excellent models to study early embryonic development, because – at least for many nematodes- eggs are transparent and the development from fertilized egg to hatched juvenile can be visualized directly under the light microscope. In a first part of this thesis a comparative analysis of the early embryonic development was done on 21 nematode species belonging to clade 6 and clades 9-12 (phylogeny of Holterman et al., 2006). Our study revealed prominent differences between nematodes. Variations include differences in cell cycle rhythms, cleavage order of the blastomeres, spatial configuration of the early embryo (based on cell-cell contacts and division angles), establishment of bilateral symmetry and the process of gastrulation. However, this diversity in early embryonic development does not result in a corresponding degree of diversity in the morphology of hatched juveniles. Thus, modifications of these early developmental mechanisms have apparently no impact on the adult morphology and are probably the result of neutral evolution. For most examined characters a large amount of intraspecific variation was observed for all species. This intraspecific variation shows that a “strict invariant” lineage, with a strict timing of cell divisions and stereotyped cell contacts in the early phase of embryonic development, is not a prerequisite to develop into a worm. Besides this intraspecific variation, coding early developmental data proved to be problematic, because of interdependency of the data, since most early developmental characters are linked in time and space. From the comparative analysis five five characters, which are potentially useful to infer phylogenetic information were distilled. In a second part of this thesis ancestral state reconstructions of these characters onto a molecular phylogeny revealed four synapomorphies. Some characters proved to have a biased evolution as they have arisen multiple times in independent lineages. Statistical tests indicate possible relationships with developmental speed and egg shape. However, further analysis on a larger number of species and the inclusion of statistical tests that account for phylogenetic relationships should reveal whether these features are due to directional selection or other constraints, or whether the occurrence of these features is due to common ancestry."],"dc:format":["application/pdf"],"dc:identifier":["https://biblio.ugent.be/publication/469133","http://hdl.handle.net/1854/LU-469133","http://doi.org/1854/13577","https://biblio.ugent.be/publication/469133/file/4334836"],"dc:language":["und"],"dc:rights":["info:eu-repo/semantics/openAccess"],"dc:title":["Comparative and phylogenetic analysis of the early embryonic development in the phylum Nematoda"],"dc:type":["dissertation","info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]},"updated_at":"2026-07-24T02:23:05Z"}