Tooth Microwear in Fishes

The scratches found on teeth as a result of processing food items, referred to as tooth microwear, can provide evidence of many aspects of an animal’s feeding ecology. This thesis asks fundamental questions concerning quantitative tooth microwear techniques in living and fossil fish. Previous work has shown that different niches produce contrasting microwear patterns that we can recognise and interpret in threespine stickleback (Gasterosteus aculeatus). To test how rapidly microwear is formed an investigation of sticklebacks revealed that the pattern can be changed with an altered feeding regime within two days. The rate of tooth replacement is less rapid with teeth having a potential functional lifespan of 126 days for sticklebacks and 91 days for bowfin (Amia calva). In sticklebacks no significant difference was found in microwear between different feeding treatments that varied in prey size and toughness. Fish may still overwhelmingly express wild-type microwear and this highlights the problems in using animals from the wild. To test seasonal variation a nine months study of wild stickleback provided the opportunity to discover if microwear varied with seasonal dietary changes. Microwear did vary over the course of the study and this change was correlated with changes in diet. To test whether the same techniques are applicable to other fish, perch (Perca fluviatilis) revealed some differences in microwear between trophic niches but these differences were restricted to smaller individuals. Diet changed with age and the amount of microwear became less. Microwear was used to reconstruct feeding behaviour in fossil Gyrodus planidens. The latest image capture techniques were used to determine jaw movement. Instead of vertical crushing, the jaw must have moved in propalinal shearing motion. This thesis has demonstrated that quantitative tooth microwear can be used widely in fish studies.