A quantitative analysis of pharyngeal tooth shape in the zebrafish (Danio rerio, Teleostei, Cyprinidae)

To test whether successive replacement cycles in the pharyngeal dentition o f the zebrafish, a polyphyodont vertebrate model organism, entail overall s hape changes in the teeth, a qualitative and quantitative analysis was made of size and share variables in the five ventral teeth. The following measu rements were defined: tooth length, tooth height, neck-crown angle, cusp de pth, and crown curvature. Ontogenetic changes in fish, ranging between 6 an d 29 mm standard length (SL), were analysed by linear regressions on to SL. The teeth became significantly larger with growth of the fish, through suc cessive replacements and cusp depth also increased over lime. Neck-crown an gle and crown curvature did not change over time. Position-dependent differ ences were analysed by Friedman ANOVA and Kendall concordance tests. Measur ements differed significantly according to tooth position in the pharyngeal jaws. Tooth 1V was always the smallest, 3V the largest. The neck-crown ang le and curvature of the crown increased from 1V to 5V. Cusp depth increased from 1V to 3V, and then decreased again. These results indicate that succe ssive replacement cycles entail a size increase accompanied by shape change s apparently restricted to the crown. These quantitative data lay the basis for further descriptive and experimental studies of tooth shape in this mo del-species. (C) 2000 Elsevier Science Ltd. All rights reserved.