Behavioral test batteries induce transient, domain-specific effects while preserving global phenotypic structure in zebrafish
Behavioral test batteries are increasingly used to characterize multiple functional domains in zebrafish, yet the potential impact of test sequence on behavioral outcomes remains poorly defined. Here, we systematically evaluated whether test order influences behavioral responses in a three-assay battery comprising the novel tank test (NTT), mirror-induced aggression (MIA), and social preference (SP) test. Adult zebrafish (Danio rerio) were exposed to all possible permutations of the three assays in a fully counterbalanced design, allowing assessment of order effects across locomotor, anxiety-like, aggression-related, and social behaviors. Test order produced modest and parameter-specific effects, primarily affecting locomotor activity in the NTT and social proximity in the SP assay. Time-course analysis revealed within-test behavioral dynamics, with limited evidence that test order modulates early adaptation or late engagement with the testing environment but does not alter overall temporal response profiles. Sex-dependent effects were assay-specific and most pronounced in the NTT, with no consistent sex differences observed in MIA or SP. To evaluate the global structure of behavioral variation, Principal Component Analysis (PCA) was performed across assays. Despite localized effects of test order, no clear multivariate separation between test sequences was observed, indicating that sequential testing does not produce distinct baseline phenotypes. Together, these findings support the robustness and reproducibility of multidomain behavioral batteries while highlighting the importance of standardized test-order reporting to improve cross-study comparability.