Abstract
Behavioral lateralization has been documented in many vertebrates. The scale-eating cichlid fish Perissodus microlepis is well known for exhibiting lateral dimorphism in its mouth morphology and lateralized behavior in robbing scales from prey fish. A previous field study indicated that this mouth asymmetry closely correlates with the side on which prey is attacked, but details of this species' predation behavior have not been previously analyzed because of the rapidity of the movements. Here, we studied scale-eating behavior in cichlids in a tank through high-speed video monitoring and quantitative assessment of behavioral laterality and kinematics. The fish observed showed a clear bias toward striking on one side, which closely correlated with their asymmetric mouth morphologies. Furthermore, the maximum angular velocity and amplitude of body flexion were significantly larger during attacks on the preferred side compared to those on the nonpreferred side, permitting increased predation success. In contrast, no such lateral difference in movement elements was observed in acoustically evoked flexion during the escape response, which is similar to flexion during scale eating and suggests that they share a common motor control pathway. Thus the neuronal circuits controlling body flexion during scale eating may be functionally lateralized upstream of this common motor pathway.
Highlights
Anatomical brain lateralization, e.g., the asymmetric organization of the left and right hemispheres, has been widely documented among vertebrates from fish to mammals [1,2]
Monitoring P. microlepis scale-eating behavior in a tank revealed a remarkable laterality in the side and direction of attack and kinematics of the behavior
The preferred side of attack corresponded to the asymmetric mouth morphology, and higher predation success was achieved when direction of attack corresponded to asymmetric mouth morphology
Summary
Anatomical brain lateralization, e.g., the asymmetric organization of the left and right hemispheres, has been widely documented among vertebrates from fish to mammals [1,2]. Brain lateralization may give rise to an increase in cognitive abilities, behavioral complexity, or behavioral laterality, leading to advantages in brain function (see [3] for a review). Chicks with lateralized brains were found to detect a raptor stimulus with shorter latency than were nonlateralized chicks [4], and lateralization enhances the ability of chicks to perform two tasks simultaneously [5]. Despite many documented examples of behavioral laterality in various organisms [1,7], there is little direct evidence of the neuronal basis for behavioral laterality in vertebrates. The complexity of the neuronal basis and the subtlety of the differences in morphological asymmetry increase the difficulty of analysis. Few attempts have been made to link lateralized behaviors to their underlying neuronal mechanisms
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