Abstract
Scale-eating cichlid fish, Perissodus microlepis, from Lake Tanganyika display handed (lateralized) foraging behavior, where an asymmetric ‘left’ mouth morph preferentially feeds on the scales of the right side of its victim fish and a ‘right’ morph bites the scales of the left side. This species has therefore become a textbook example of the astonishing degree of ecological specialization and negative frequency-dependent selection. We investigated the strength of handedness of foraging behavior as well as its interaction with morphological mouth laterality in P. microlepis. In wild-caught adult fish we found that mouth laterality is, as expected, a strong predictor of their preferred attack orientation. Also laboratory-reared juvenile fish exhibited a strong laterality in behavioral preference to feed on scales, even at an early age, although the initial level of mouth asymmetry appeared to be small. This suggests that pronounced mouth asymmetry is not a prerequisite for handed foraging behavior in juvenile scale-eating cichlid fish and might suggest that behavioral preference to attack a particular side of the prey plays a role in facilitating morphological asymmetry of this species.
Highlights
The same clear pattern was found in the 13 pools with one pair of P. microlepis each as predators (Figure 2 C, D): seven RL pairs fed from both flanks with similar frequencies and produced similar amount of damage onto both flanks
How and probability of left attack when lateralized foraging behavior manifests itself during ontogeny, and whether its association with mouth asymmetry is already apparent in juvenile individual fish had remained untested
We report on the strength and individual variation of lateralized foraging behavior as well as its relationship with mouth asymmetry in P. microlepis during its juvenile as well as adult life stages
Summary
One interesting case is handed (lateralized) behavior, where individuals exhibit a behavioral bias towards either one or the other side. Behavioral lateralization can frequently be observed in other species; for example, hand-use preference in Chimpanzees [2] and in some birds like Australian parrots [3], and foraging preference in the Japanese snail-eating snakes [4,5]. This lateralized behavior, in mammals and birds, is thought to be linked to lateralized brain functions and neuro-anatomical asymmetries (reviewed in [6]). From an ecological perspective, handed behavior is suggested to have evolved because it might provide organisms with a selective advantage (e.g. in terms of foraging efficiency in the snail-eating snake, Pareas iwasakii [4]; escape performance from predator attacks in the shiner perch, Cymatogaster aggregata [7]; predation success in the scale-eating cichlid, Perissodus microlepis [8])
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