Quantitative Responses of Adult Zebrafish to Changes in Ambient Illumination

The use of zebrafish models to study central nervous system aging and late-onset neurological diseases will be facilitated by assays allowing rapid evaluation of neurological phenotypes in adult zebrafish. We analyzed groups of 12 adult zebrafish swimming simultaneously in single-animal arenas, and quantified their responses to changes in ambient illumination. Under these conditions, stereotypical locomotor patterns were observed and readily quantified using open source software. Continuous, low-velocity movements were observed during 10-min periods of darkness, whereas intermittent high-velocity movements occurred in bright light. At 80%-90% of abrupt light-to-dark or dark-to-light transitions, adult zebrafish produced a synchronous short-latency (20-22 ms) turn, followed by a propulsive movement with a high transient maximum velocity (400-500 mm/s). Between 5 and 35 months of age, latency increased by ∼10%, and peak velocity decreased by ∼30%, suggesting that the response declines in aged adults. Light transition responses can be measured rapidly and automatically in multiple adult zebrafish simultaneously, providing a convenient quantitative method for evaluating sensorimotor function in adult zebrafish models of neurological disease.