Lateralized behavior in the attacks of largemouth bass on Rhinogobius gobies corresponding to their morphological antisymmetry.

Vertebrates show left-right biases in turning direction, limb usage, predator-escape response and use of sensory organs. In particular, some fishes are known to have lateral biases in predatory behaviors corresponding to their morphological antisymmetry. To reveal the effects of these laterally biased behaviors on predator-prey interaction, we conducted behavioral tests of predatory events between largemouth bass, Micropterus salmoides, and freshwater gobies, Rhinogobius sp., both of which have individuals with a well-developed left side and individuals with a well-developed right side. The left-developed bass tended to approach the goby clockwise from behind, whereas right-developed individuals tended to approach counterclockwise. Congruently, left-developed gobies began their escape maneuvers at a longer distance from bass when they were approached clockwise than when they were approached counterclockwise, whereas right-developed gobies showed the reverse tendency. The longer the distance between bass and gobies at the start of goby escape, the more the subsequent bass strike or dash was delayed. Under these conditions, predation should be more successful when a left (right)-developed bass meets a right (left)-developed goby, and less successful when a left (right)-developed bass meets a left (right)-developed goby. This prediction was consistent with the difference in predation success in our test and in field data from Lake Biwa, Japan. We conclude that lateral biases in the behavioral direction of each morphological type will generate bias in predation success between different combinations of predator and prey types, leading to the maintenance of antisymmetric dimorphism through negative frequency-dependent natural selection.