Assessing memory in zebrafish using the one-trial test

•We observed adult zebrafish in the one-trial memory test.•Zebrafish tend to explore a new object, can memorize the characteristics of this object and use this information when a second object was presented.•Zebrafish are capable of distinguishing the two objects irrespective of the delay (2, 6 or 24 h) that separated the two phases.

Zebrafish represents a very promising model to study memory function and impairment in vertebrates. The one-trial memory test has proven to be a reliable method to assess memory in mammals without the need for an extensive training procedure or the learning of a rule. To investigate whether such a test is suitable for zebrafish we observed adult fish in a modification of the original one-trial memory test developed for rats. Subjects were allowed to familiarize themselves with a new object for 25 min (exposure phase) and were then required to discriminate between the familiar object and a novel object that differed in shape and color (test phase). In both phases zebrafish showed a clear tendency to explore a new object, can memorize the characteristics of this object and use this information when a second object was presented irrespective of the delay (2, 6 or 24 h) that separated the two phases. These results suggest that memory performance in fish could be also assessed using this very simple test.