Neural systems that process visual self-motion cues in larval fish: a comparative approach

Animal models are widely used in science, with zebrafish, Danio rerio, occupying a key role in neuroscience.

However, broadening the variety of species studied is essential to test the generalization of findings and explore sources of behavioral diversity. This thesis expands methods used for the study of visual behaviors in larval zebrafish to other species, such as the giant danio, Devario aequipinnatus, and the danionella, Danionella cerebrum.

Using two-photon functional imaging in zebrafish and giant danio, a protocol was developed to assess neural responses to moving gratings and evaluate speed tuning. Zebrafish imaging revealed differing responses to forward and backward motion, but the giant danio showed inconsistent fluorescence, limiting further analysis.

For the study of binocular optomotor response, a stimulus and protocol were designed and tested in all three species. While angular responses were similar across species, linear displacements differed. Zebrafish and danionella showed comparable baseline responses, whereas giant danio exhibited significantly higher responses, with zebrafish and giant danio also showing increased responses for forward-directed motion, a pattern absent in danionella.

Finally, a setup was constructed to capture images of hunting larvae for studying prey capture behavior in zebrafish and giant danio, with the latter demonstrating a higher prey consumption rate. A SLEAP model was trained to add eye and fin tracking to existing tail tracking, which, combined with prey location data, provides a detailed characterization of prey capture behavior sequences.