Feeding experiments with Senegal bichir Polypterus senegalus provide evidence for diet-related tooth damage and dental microwear

Dental microwear is a useful tool for reconstructing jaw movements and diet in toothed vertebrates, but its application to fishes (Actinopterygii and Chondrichthyes) remains limited. This is partly due to the lack of experiments directly linking diet and microwear in these groups; only one highly-derived teleost (Actinopterygii, or ray-finned fishes) species of recent origins, the three-spined stickleback Gasterosteus aculeatus, has been subject to controlled feeding experiments. As sticklebacks are suction or ram feeders that live on macroplankton and insect larvae and do not use their dentitions for prey processing, the absence of experimental data from other fish species limits our ability to interpret dental microwear and infer diet and feeding style in a wider range of fossil and living species with various ecologies. Here we present the results of a second feeding experiment involving fishes using the basally-branching, biting, often-piscivorous ray-finned fish Senegal bichir Polypterus senegalus to evaluate whether controlled diet differences can generate detectable tooth damage and dental microwear patterns. Individuals were fed four different food items - loaches, shrimp, pellets, and mealworms - for one, two, and three months. We then examined tooth tip damage and linear microwear (scratches). Shrimp and mealworm feeding produced short scratches, whereas pellet and loach feeding produced long scratches. Most teeth exhibited apical tip damage despite the presence of a solid enameloid acrodin cap (a characteristic of ray-finned fishes), with damage being larger in loach-fed individuals and smaller in those fed with mealworms. Our results suggest a possible relationship between diet, tooth damage, and dental microwear in non-durophagous fishes which never-the-less use teeth for prey capture and processing, offering a framework for inferring diet in extinct forms with similar ecomorphology to Polypterus.