Worth a Thousand Words: Handedness in Fish

If you look closely at the image above, you’ll see that the mouths of these cichlid fish, Perissodus microlepis, curve in opposite directions. Similar to left or right handedness in humans, many animals exhibit handedness in behavior or morphology. Whether handed behavior is expressed early in development and produces mouth asymmetry or the opposite, that mouth asymmetry produces handed behavior, however, is not well known. The authors of the study “Handed Foraging Behavior in Scale-Eating Cichlid Fish: Its Potential Role in Shaping Morphological Asymmetry” set out to investigate this question and more. The image above is Figure 1 of the article.

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.

Citation: Lee HJ, Kusche H, Meyer A (2012) Handed Foraging Behavior in Scale-Eating Cichlid Fish: Its Potential Role in Shaping Morphological Asymmetry. PLoS ONE 7(9): e44670. doi:10.1371/journal.pone.0044670