A major challenge for comparative biology is understanding what aspects of an animal’s
locomotor repertoire represent general features of motor organization, versus specialized
adaptations for its anatomy and ecological niche. In this thesis I investigate the Giant
Danio larvae (Devario aequipinnatus) as a potential model for comparative studies with
Zebrafish, a well-established animal model in neuroscience. To this end, I study the locomotor
behavior of both species and how its differences are reflected in the underlying
neural circuit structure. Initially, I compare the anatomy of the descending pathways
controlling locomotion in Giant Danio to Zebrafish using retrograde labelling of reticulospinal
neurons. I see a striking resemblance of the circuit in both species, with a roughly
similar organization and the general division and number of cell clusters being very well
conserved. Following, I compare visually guided behaviours in Giant Danio to different
Zebrafish strains. Giant Danio show a stronger optomotor response than Zebrafish.
The optomotor response of Giant Danio first appear around 4 days post fertilization and
can be consistently and reliably evoked. During optomotor tracking Giant Danio show
shorter interbout intervals and are able to track motion at higher speeds than Zebrafish.
I also observe that the higher manoeuvrability of Giant Danio is also reflected during
prey capture. Interestingly, Zebrafish strains derived from more recently wild-caught
fish show more robust optomotor behaviour, closer to Giant Danio. Lastly, I demonstrate
the suitability of using Giant Danio in a head-restrained preparation with a 3D virtual
reality environment.
Combined with the potential for comparative approaches with Zebrafish, the faster
development, larger neurons, and the rich behavioural repertoire of Giant Danio make it
a promising model for neuroscience
