Modelling internal flows in juvenile Euprymna scolopes during symbiosis formation

The Hawaiian bobtail squid (Euprymna scolopes) is a model organism for studying symbiosis. It partners with the bioluminescent bacteria Vibrio fischeri, which provide the squid with light for counterillumination. This active camouflage is crucial for the squid's survival during nocturnal hunting. Squid are born without their symbionts and must acquire them from their environment. One critical aspect of the colonisation process in juvenile squid is getting their bacterial partners from the wider oceanic environment to the correct location internally. To aid in this, the squid utilises a ciliated light organ, a specialised internal organ that houses its symbiont. The cilia generate local flows, which, alongside the ventilatory flows generated by the squid, enable fluid through their interval cavity, directing it toward the light organ's surface. Here, the bacteria can pass inside the light organ. To study the role of flows in the process, we have implemented Computational Fluid Dynamics modelling using the Method of Regularised Stokeslets. Our ongoing work has sought to expand the model's complexity to encompass additional features of the squid's internal cavity. Additionally, these models have allowed us to capture the motion of particles advected within the squid. Motivated by experimental observations, we have selected several parameters within our model, generating particle trajectories that allow us to explore potential impacts on the colonisation process when breathing or ciliary dynamics are disrupted.