Development of sensorimotor responses in larval zebrafish: a comparison between wild-type and GCaMP6s transgenic line.

During early development, zebrafish larvae exhibit stereotypical behaviors, which rapidly become more complex. Thus, generating mutant transgenic lines that maintain transparency throughout their larval stage and that can be used to record brain activity has offered strategic opportunities to investigate the underlying neural correlates of behavior establishment. However, few studies have documented the sensorimotor profile of these lines during larval development. Here, we set up a behavioral characterization using diverse stimuli (light and vibration) throughout larval development to compare the responses of a transgenic strain expressing a pan-neuronal calcium indicator (GCaMP6s) with that of a wild-type strain. Interestingly, we report a drastic switch in behavioral responses to light transitions at 11 days post-fertilization (dpf) and to vibration stimuli at 14 dpf in both lines. These data highlight a specific time window representing an increase in behavioral complexity. Meanwhile, we found some differences in the maturation of sensorimotor responses between GCaMP6s and wild-type strains. Although some of these differences are minor, they highlight the need for careful attention when using mutant/transgenic lines for behavioral studies. Overall, our results support using GCaMP6s strain in investigating the neural mechanisms underlying the developmental maturation of sensorimotor responses.