Scototaxis as anxiety-like behavior in fish.

The scototaxis (dark/light preference) protocol is a behavioral model for fish that is being validated to assess the antianxiety effects of pharmacological agents and the behavioral effects of toxic substances, and to investigate the (epi)genetic bases of anxiety-related behavior. Briefly, a fish is placed in a central compartment of a half-black, half-white tank; following habituation, the fish is allowed to explore the tank for 15 min; the number and duration of entries in each compartment (white or black) are recorded by the observer for the whole session. Zebrafish, goldfish, guppies and tilapias (all species that are important in behavioral neurosciences and neuroethology) have been shown to demonstrate a marked preference for the dark compartment. An increase in white compartment activity (duration and/or entries) should reflect antianxiety behavior, whereas an increase in dark compartment activity should reflect anxiety-promoting behavior. When individual animals are exposed to the apparatus on only one occasion, results can be obtained in 20 min per fish.