Active flow sensing during helical swimming in a ciliary microswimmer

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This fundamental research project will develop a new systems-level understanding of a miniature nervous system in a marine larva and how it functions in aquatic habitats with dynamic fluid flows. It proposes an interdisciplinary research framework that tightly integrates biological and physical thinking and approaches. The ability for aquatic animals to sense and respond to the movement of water around them can be important for survival. For example, fish can detect flows generated by the movement of other fish, and this sense allows them to form large schools. Other aquatic animals are able to evade approaching predators such as jellyfish by sensing the flow perturbations generated by the predator. Fish and other marine plankton can also sense the flow direction and reorient themselves to swim against the flow. This upstream swimming is known as rheotaxis, and is also the mechanism by which sperm cells navigate towards the egg for internal fertilization. How animals sense and respond to flow is incompletely understood. Organisms rely on an intricate coupling between the environmental stimulus, and their own self-movement. Our aim is to understand the neuronal and behavioural control of flow responses in a marine organism. We will study flow sensation in the larvae of a marine ragworm called Platynereis. Platynereis can be cultured in the laboratory and our team has established this animal for the experimental study of the neural mechanisms of zooplankton behaviour. We have recently discovered that the larvae of this ragworm have neurons that respond specifically to fluid flow. In this project, we will use advanced microscopy techniques to uncover how these neurons connect to the rest of the nervous system and data-driven computer modelling to reveal how flow sensation alters the larva's helical swimming behaviour. We will create custom chambers and arenas to test how single larvae respond to controlled fluid flows and microenvironments. Ragworm larvae measure only one fifth of a millimetre and this small size will allow us to investigate flow sensation at a level of detail that is not yet feasible for larger animals. Since Platynereis shows many neuronal and molecular characteristics that are similar to those found in vertebrates, our study will uncover general principles of flow sensation in animals.