Fig. 9

Schematic illustration of chaetogenesis and the interaction between the chaetoblast and the follicle cells as a series of sagittal sections of subsequent representative stages of the chaetal formation. Topological position of corresponding development stages are marked in the 3D model in Fig. 5. a Earliest stage of chaetogenesis; formation of the rostrum. b–c formation of the teeth. d–e formation of the chaetal socket. f–g Formation of the adrostral rod and the short rostral rod. h–j Final step of chaetogenesis; formation of the long rostral rod