{"id":{"repo_id":"exeter","oai_identifier":"oai:figshare.com:article/31942320"},"canonical_url":"https://search.dev.ndltd.org/etd/exeter/oai:figshare.com:article/31942320","repository":{"repo_id":"exeter","name":"University of Exeter","base_url":"https://api.figshare.com/v2/oai"},"display":{"title":"Dynamic and structural basis of complex behaviour in a ciliated unicellular organism","abstract":"The complexity in the behaviour of life’s smallest organisms is typically overlooked. Despite their small size and relative simplicity, eukaryotic microorganisms routinely perform remarkably sophisticated actions, from directional sensing and tactic navigation to prey capture, feeding, and even mating. The underlying motility repertoires we observe these organisms perform are a function of the physical environment in which they live, the dynamics and arrangement of their motility apparatus, as well as the overall cell morphology. In this thesis, we explore these aspects of organism behaviour with a focus on the marine quadriflagellate alga Pterosperma sp. We take a primarily experimental approach, combined with innovative, highly quantitative analyses to provide a more nuanced picture of microorganism behaviour such that the experimentally observed dynamics can better guide theoretical modelling. We first perform a multi-spatial and temporal scale analysis of Pterosperma’s behaviour. Classical analysis, comprising low resolution tracking of cell populations, reveals a tripartite navigation strategy. However, detailed tracking and highly time resolved analysis of the ciliary dynamics exposes far more continuous evolution through the organism’s behaviours than such a discrete representation would suggest. Capturing the ciliary dynamics across all states, we map the entire spectrum of ciliary beating performed by a living microorganism. Despite the complexity present, we find that the behavioural space is low dimensional and that the observed ciliary dynamics follow certain dispersion relations, the microscopic readout of constraints on the mechanism of ciliary actuation. Turning to the interaction of Pterosperma with its fluid environment, we simultaneously capture the changing organism morphology and fluid flows experimentally. Combining this with a method to accurately average across similar ciliary shapes enables measurements of the induced flows with unprecedented time resolution in freely swimming microorganisms. We present a minimal model based on the superposition of four stokeslets which captures the key features of the fluid profile while remaining computationally scalable. We then investigate how the presence of a nearby boundary alters this organism’s behaviour. Leveraging electron and expansion microscopy techniques, we proceed to reconstruct, in three dimensions, the internal architecture surrounding the bases of Pterosperma’s four cilia. We focus on characterising the arrangement of the calcium sensitive, contractile fibres that interconnect the cilia in diverse microorganisms. A potential role for this observed ultrastructure during one of Pterosperma’s behaviours is explored. Finally, we develop a macroscopic robotic model of the cilium. Taking inspiration from theoretical models of dynein coordination, our two filament design incorporates actuation along the robo-cilium length and relies purely on mechanical coupling to organise the shape dynamics. We discuss how such physical models can be used to develop our intuition for the functional role of structural components within the cilium.<p></p>","abstract_html":"The complexity in the behaviour of life’s smallest organisms is typically overlooked. Despite their small size and relative simplicity, eukaryotic microorganisms routinely perform remarkably sophisticated actions, from directional sensing and tactic navigation to prey capture, feeding, and even mating. The underlying motility repertoires we observe these organisms perform are a function of the physical environment in which they live, the dynamics and arrangement of their motility apparatus, as well as the overall cell morphology. In this thesis, we explore these aspects of organism behaviour with a focus on the marine quadriflagellate alga Pterosperma sp. We take a primarily experimental approach, combined with innovative, highly quantitative analyses to provide a more nuanced picture of microorganism behaviour such that the experimentally observed dynamics can better guide theoretical modelling. We first perform a multi-spatial and temporal scale analysis of Pterosperma’s behaviour. Classical analysis, comprising low resolution tracking of cell populations, reveals a tripartite navigation strategy. However, detailed tracking and highly time resolved analysis of the ciliary dynamics exposes far more continuous evolution through the organism’s behaviours than such a discrete representation would suggest. Capturing the ciliary dynamics across all states, we map the entire spectrum of ciliary beating performed by a living microorganism. Despite the complexity present, we find that the behavioural space is low dimensional and that the observed ciliary dynamics follow certain dispersion relations, the microscopic readout of constraints on the mechanism of ciliary actuation. Turning to the interaction of Pterosperma with its fluid environment, we simultaneously capture the changing organism morphology and fluid flows experimentally. Combining this with a method to accurately average across similar ciliary shapes enables measurements of the induced flows with unprecedented time resolution in freely swimming microorganisms. We present a minimal model based on the superposition of four stokeslets which captures the key features of the fluid profile while remaining computationally scalable. We then investigate how the presence of a nearby boundary alters this organism’s behaviour. Leveraging electron and expansion microscopy techniques, we proceed to reconstruct, in three dimensions, the internal architecture surrounding the bases of Pterosperma’s four cilia. We focus on characterising the arrangement of the calcium sensitive, contractile fibres that interconnect the cilia in diverse microorganisms. A potential role for this observed ultrastructure during one of Pterosperma’s behaviours is explored. Finally, we develop a macroscopic robotic model of the cilium. Taking inspiration from theoretical models of dynein coordination, our two filament design incorporates actuation along the robo-cilium length and relies purely on mechanical coupling to organise the shape dynamics. We discuss how such physical models can be used to develop our intuition for the functional role of structural components within the cilium.&lt;p&gt;&lt;/p&gt;","abstract_has_math":false,"creators":["Alexander Boggon (21058346)"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2026,"date_issued":"2026-03-17T00:00:00Z","date_published":"2026-03-17T00:00:00Z","updated_at":"2026-07-27T19:33:33Z","subjects":["Physics of living systems","Cilia","Microalgae","Microswimmers"],"languages":[],"rights":["CC BY","Open Access after 2027-09-16"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["10779/exe.31942320.v1"],"render_values":[{"text":"10779/exe.31942320.v1","href":null,"code":true}]}]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Alexander Boggon (21058346)"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2026-03-17T00:00:00Z"]},{"key":"dc:relation","label":"Dc Relation","values":["https://figshare.com/articles/thesis/Dynamic_and_structural_basis_of_complex_behaviour_in_a_ciliated_unicellular_organism/31942320"]},{"key":"dc:type","label":"Dc Type","values":["Text","Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Physics of living systems","Cilia","Microalgae","Microswimmers"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["CC BY","Open Access after 2027-09-16"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["10779/exe.31942320.v1"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["The complexity in the behaviour of life’s smallest organisms is typically overlooked. Despite their small size and relative simplicity, eukaryotic microorganisms routinely perform remarkably sophisticated actions, from directional sensing and tactic navigation to prey capture, feeding, and even mating. The underlying motility repertoires we observe these organisms perform are a function of the physical environment in which they live, the dynamics and arrangement of their motility apparatus, as well as the overall cell morphology. In this thesis, we explore these aspects of organism behaviour with a focus on the marine quadriflagellate alga Pterosperma sp. We take a primarily experimental approach, combined with innovative, highly quantitative analyses to provide a more nuanced picture of microorganism behaviour such that the experimentally observed dynamics can better guide theoretical modelling. We first perform a multi-spatial and temporal scale analysis of Pterosperma’s behaviour. Classical analysis, comprising low resolution tracking of cell populations, reveals a tripartite navigation strategy. However, detailed tracking and highly time resolved analysis of the ciliary dynamics exposes far more continuous evolution through the organism’s behaviours than such a discrete representation would suggest. Capturing the ciliary dynamics across all states, we map the entire spectrum of ciliary beating performed by a living microorganism. Despite the complexity present, we find that the behavioural space is low dimensional and that the observed ciliary dynamics follow certain dispersion relations, the microscopic readout of constraints on the mechanism of ciliary actuation. Turning to the interaction of Pterosperma with its fluid environment, we simultaneously capture the changing organism morphology and fluid flows experimentally. Combining this with a method to accurately average across similar ciliary shapes enables measurements of the induced flows with unprecedented time resolution in freely swimming microorganisms. We present a minimal model based on the superposition of four stokeslets which captures the key features of the fluid profile while remaining computationally scalable. We then investigate how the presence of a nearby boundary alters this organism’s behaviour. Leveraging electron and expansion microscopy techniques, we proceed to reconstruct, in three dimensions, the internal architecture surrounding the bases of Pterosperma’s four cilia. We focus on characterising the arrangement of the calcium sensitive, contractile fibres that interconnect the cilia in diverse microorganisms. A potential role for this observed ultrastructure during one of Pterosperma’s behaviours is explored. Finally, we develop a macroscopic robotic model of the cilium. Taking inspiration from theoretical models of dynein coordination, our two filament design incorporates actuation along the robo-cilium length and relies purely on mechanical coupling to organise the shape dynamics. We discuss how such physical models can be used to develop our intuition for the functional role of structural components within the cilium.<p></p>"]},{"key":"dc:title","label":"Title","values":["Dynamic and structural basis of complex behaviour in a ciliated unicellular organism"]}]}],"canonical_facts":{"dc:creator":["Alexander Boggon (21058346)"],"dc:date":["2026-03-17T00:00:00Z"],"dc:description":["The complexity in the behaviour of life’s smallest organisms is typically overlooked. Despite their small size and relative simplicity, eukaryotic microorganisms routinely perform remarkably sophisticated actions, from directional sensing and tactic navigation to prey capture, feeding, and even mating. The underlying motility repertoires we observe these organisms perform are a function of the physical environment in which they live, the dynamics and arrangement of their motility apparatus, as well as the overall cell morphology. In this thesis, we explore these aspects of organism behaviour with a focus on the marine quadriflagellate alga Pterosperma sp. We take a primarily experimental approach, combined with innovative, highly quantitative analyses to provide a more nuanced picture of microorganism behaviour such that the experimentally observed dynamics can better guide theoretical modelling. We first perform a multi-spatial and temporal scale analysis of Pterosperma’s behaviour. Classical analysis, comprising low resolution tracking of cell populations, reveals a tripartite navigation strategy. However, detailed tracking and highly time resolved analysis of the ciliary dynamics exposes far more continuous evolution through the organism’s behaviours than such a discrete representation would suggest. Capturing the ciliary dynamics across all states, we map the entire spectrum of ciliary beating performed by a living microorganism. Despite the complexity present, we find that the behavioural space is low dimensional and that the observed ciliary dynamics follow certain dispersion relations, the microscopic readout of constraints on the mechanism of ciliary actuation. Turning to the interaction of Pterosperma with its fluid environment, we simultaneously capture the changing organism morphology and fluid flows experimentally. Combining this with a method to accurately average across similar ciliary shapes enables measurements of the induced flows with unprecedented time resolution in freely swimming microorganisms. We present a minimal model based on the superposition of four stokeslets which captures the key features of the fluid profile while remaining computationally scalable. We then investigate how the presence of a nearby boundary alters this organism’s behaviour. Leveraging electron and expansion microscopy techniques, we proceed to reconstruct, in three dimensions, the internal architecture surrounding the bases of Pterosperma’s four cilia. We focus on characterising the arrangement of the calcium sensitive, contractile fibres that interconnect the cilia in diverse microorganisms. A potential role for this observed ultrastructure during one of Pterosperma’s behaviours is explored. Finally, we develop a macroscopic robotic model of the cilium. Taking inspiration from theoretical models of dynein coordination, our two filament design incorporates actuation along the robo-cilium length and relies purely on mechanical coupling to organise the shape dynamics. We discuss how such physical models can be used to develop our intuition for the functional role of structural components within the cilium.<p></p>"],"dc:identifier":["10779/exe.31942320.v1"],"dc:relation":["https://figshare.com/articles/thesis/Dynamic_and_structural_basis_of_complex_behaviour_in_a_ciliated_unicellular_organism/31942320"],"dc:rights":["CC BY","Open Access after 2027-09-16"],"dc:subject":["Physics of living systems","Cilia","Microalgae","Microswimmers"],"dc:title":["Dynamic and structural basis of complex behaviour in a ciliated unicellular organism"],"dc:type":["Text","Thesis"]},"updated_at":"2026-07-27T19:33:33Z"}