The Importance of Holding Water: Salinity and Chemosensory Cues Affect Zebrafish Behavior

Abstract

The zebrafish is becoming a popular model organism for studying numerous biological phenomena. Among these are brain function and behavior, including social behavior. Although usually neglected, few studies have already demonstrated that even trivial factors, such as features of the holding water may alter zebrafish behavior. In this study, we employed a 2 × 2 between-subject experimental design, exposing zebrafish to water of either high or low salinity and with chemosensory/olfactory cues of conspecifics either present or absent (while maintaining pH, temperature, nitrate, nitrite, and ammonia levels constant). We presented moving images of conspecifics to experimental zebrafish and analyzed their behavioral responses using video tracking. We found significant interaction between salinity and olfactory cues. For example, zebrafish exposed to their home tank water (high salinity with chemosensory/olfactory cues present) stayed significantly closer to the bottom of their tank compared with fish exposed to the other water conditions, and fish exposed to water with chemosensory/olfactory cues significantly reduced their turns compared with fish exposed to water without chemosensory/olfactory cues. These differences signify the impact environmental factors, for example, fluctuations in salinity level and presence or absence of chemosensory/olfactory cues, may have on zebrafish behavior. We conclude that maintaining stable environmental conditions and specifying and reporting them precisely are important for reducing error variation and for making results across independent studies more comparable.

Keywords: chemosensory and olfactory cues; fear and anxiety; replicability; social behavior; water salinity; zebrafish.