A quantitative comparison of osteoclasts in the teeth of the anuran amphibian Xenopus laevis.

An image-analysing computer was used to measure transectional areas of osteoclast cytoplasm and nuclei, the number of nuclei per osteoclast transection, odontoblast height and dentine thickness on serial sections of resorbing, erupting and ankylosed teeth from 3 groups of female frogs of different snout-vent lengths. All parameters except nuclear size were increased significantly between the small and large frogs, suggesting that larger teeth are resorbed by larger osteoclasts. Because more time is required for resorption of the thicker dentine of large frogs, the increased size and nuclear number of the osteoclasts in large specimens may be related to the increased time available for fusion of mononuclear precursor cells. However, in large frogs the proportional increase in cytoplasmic area of osteoclasts was greater than the increase in number of nuclei. This may be related to osteoclast activity, as the height of the odontoblasts also increased with dentine thickness.