Wild zebrafish exhibit a wide range of behavior. We found abundant wild zebrafish in flowing rivers and still water, in large, tightly-knit groups of hundreds of individuals, as well as in small, loose shoals. In two still-water populations, zebrafish were quite small in body size, common, and in tight groups of up to 22 fish. As in earlier laboratory studies, these zebrafish exhibited very low levels of aggression. In slowly flowing water in central India, zebrafish were relatively rare and gathered in small shoals (4-12 fish), often with other small fish, such as Rasbora daniconius. These stream zebrafish were larger in body size (27 mm TL) and much more aggressive than those in still water. In a second river population with much faster flowing water, zebrafish were abundant and again relatively large (21 mm TL). These zebrafish occurred in very large (up to 300 individuals) and tightly-knit (nearest-neighbor distances up to 21 mm) groups that exhibited collective rheotaxis and almost no aggression. This remarkable variation in social behavior of wild zebrafish offers an opportunity for future studies of behavioral genetics, development, and neuroscience.

Animals may exhibit preference for colors that match their environment or the resources in the environment. These preferences may impact ability to learn associations with these colors and revert the associations when the reward contingency is modified. We used zebrafish Danio rerio from four populations to test if color preferences impact associative and reversal learning ability. First, we tested if preference for blue or green impact associative ability. We subjected individual fish through eight trials to associate a social stimulus with blue or green. Next, we tested if preference for red or green impact associative reversal learning ability. We trained fish in groups of three to associate a social stimulus with red or green over three trials, and reversed the reward contingency during the following session. Results showed that zebrafish preferred green over blue and domesticated fish chose green more than blue when there was a reward attached. Zebrafish also preferred red over green. Fish from one wild population learned with both colors and reversed learning only from green to red and not vice-versa. Fish from another population showed an overwhelming preference for red irrespective of what was rewarded. Domesticated fish did not show reversal learning ability.

No abstract

No abstract