Behavioral asymmetry and lateralization in Zebrafish (Cyprinidae: Danio rerio) during escape, exploratory, and inspection behavior



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Texas Tech University


Miklosi et al. (1998) have shown that zebrafish display a cognitive lateralization and this is suggested by their asymmetric perceptual processing of various stimuli. Previous unpublished work with guppies (Poecilia reticulata) in our laboratory has suggested that inspection behavior is asymmetric with respect to sense organs (eyes and acousticolateralis system).

We studied behavioral asymmetries in adult zebrafish {Danio rerio) by comparing directional responses in exploratory, escape, and inspection behaviors. Responses under specific stimuli (those that induce inspection or escape) and non-specific stimuli (exploratory behavior) were videotaped, the path of the fish digitized on a Summagraphics® board; the data are than analyzed using a Matlab® program.

Thirty-three adult fish were randomly tested using fifteen replications for each stimulus.

Results indicate behavioral lateralization at the individual level, rather than at population level. Behavioral responses appear to be stimulus specific, as the degree of lateralization changes according to the stimulus applied. The first repetition seem to be the determinant for behavioral lateralization measurements, as following repetitions tend to result opposite to the first one.

It has been observed that fish during inspection behavior adopt a peculiar mode of swimming, by approaching at an average speed, followed by a slower approach of the object of interest, and a quick retum to a safe distance.

In future study, we intend to compare the responses for each individual to the degree of asymmetry in the whole brain as determined by photographing the brains and measuring the relative sizes of their parts using a digitizing system (TPSDig).



Zebra danio