Fig. 3.

Oral and pharyngeal tooth replacement histology in stickleback. In all panels, dotted circles mark the general location of erupted tooth dislodgement adjacent to a presumed replacement tooth germ, arrows mark tooth germs, and carets indicate likely osteoclasts. All panels show sagittal (a, b) or transverse (c, d) sections and are oriented with the dorsal side facing upwards. a, b Oral tooth fields on the premaxilla and dentary bones were only observed as replacing via a 1-for-1 mechanism. c Pharyngeal replacement tooth germs were typically observed as dislodging only one other erupted pharyngeal tooth in 74.6% of cases (n = 50/67, see Methods). d By contrast, some pharyngeal replacement tooth germs appeared to be dislodging two erupted teeth simultaneously in 25.4% of cases (n = 17/67, see Methods). All scale bars = 20 μm