Different functions for the lateral line in schooling behavior in three fish species

Fish use vision and the lateral line in order to school together. Previous studies suggest that some species rely more than others on the lateral line for schooling, and no clear mechanistic reason for these differences has been identified. To address the question of how species-level differences in the lateral line might impact schooling behavior, we identified three schooling species (giant danios Devario aequipinnatus , cherry barbs Puntius titteya , and neon tetras Paracheirodon innesi ) that come from different environments and have differently structured lateral line systems. We expected to see larger changes in schooling behavior in species of fish with more neuromasts. To test this hypothesis we imaged the lateral lines of these fishes, then quantified schooling behavior before and after lateral line ablation. Giant danios had the lowest density of neuromasts and, as expected, showed little response to ablation. Cherry barbs and neon tetras both had higher densities of neuromasts and schooled differently after ablation, but in opposite ways. Cherry barbs became a less cohesive school while neon tetras formed a more cohesive school. Both of these species had a greater density of neuromasts than giant danios, but the cherry barbs had a greater number of canal neuromasts. This difference in canal neuromasts in cherry barbs may explain the differences in schooling behavior after ablation if they depended more on them for schooling. Overall, these results shed light on the importance of the lateral line, and the diversity of roles it plays in fish schooling.