The tooth, the whole tooth and nothing but the tooth: tooth shape and ontogenetic shift dynamics in the white shark Carcharodon carcharias.

Abstract

Ontogenetic dietary shifts are widespread across the animal kingdom, and often involve associated morphological changes in foraging phenotype. These changes may differ between sexes or vary between individuals, and are important factors in the ecology of species. While such factors have received much attention in terrestrial systems, they are much less well understood in marine taxa. The white shark Carcharodon carcharias is a marine apex predator that is accepted to provide a classic example of an ontogenetic dietary shift, with an associated change in tooth morphology from cuspidate to broad. Our results however, which include measurements obtained using a novel photographic method, reveal significant differences between the sexes in the relationship between tooth cuspidity and shark total length (TL), and a novel ontogenetic change in male tooth shape. Males exhibit broader upper first teeth and increased distal inclination of upper third teeth with increasing length, while females do not present a consistent morphological change. Substantial individual variation, with implications for pace of life syndrome, was present in males, and tooth polymorphism was suggested in females. Sexual differences and individual variation may play major roles in ontogenetic changes in tooth morphology in white sharks, with potential implications for their foraging biology. Such individual and sexual differences should be included in studies of ontogenetic shift dynamics in other species and systems.