Influence of Substrate Orientation on Feeding Kinematics of Algae Grazing Lake Malawi Cichlid Fishes

Lake Malawi cichlids have been studied extensively in an effort to elucidate the mechanisms underlying their adaptive radiation. This divergence is proposed to have happened via processes such as habitat partitioning, trophic specialization, and sexual selection. However, in the rock-dwelling mbuna of Lake Malawi this divergence likely involves how and where species feed on algae within the rocky reefs they exclusively inhabit. For three species of mbuna, we quantified feeding kinematics on substrates at different orientations that mimicked the top, sides, and bottoms of the algae covered boulders these species feed from in the wild. Significant differences in kinematics were found among the species, and several of the kinematic variables were found to differ within species when the same individuals grazed from different surface orientations. In general, it appears that microhabitat divergence linked to differences in feeding kinematics could have played a significant role in the origin and maintenance of the vast diversity of co-occurring Lake Malawi mbuna species.