Fig. 6. Variation in morphology and mechanics along the height of the cupula. (A) A schematic illustration showing the major morphological differences along the height of a cupula. (B) Photographs of cross-sections of a typical neuromast at three different heights. (C) The diameter of the cupula decreases with height, as shown by mean values (points and heavy line, ±1s.d. shown by thin lines, numbers indicate sample size). (D) The number of kinocilia in a cross-section decreases with height. Data for individual cupulae (gray lines) and mean values (points and heavy line, ±1s.d. shown by thin lines) are shown. (E) The mean values of the morphological data in D, along with our measurements of flexural stiffness (EI, Fig. 4), provide the basis for calculations of cupular flexural stiffness versus height. The total flexural stiffness of the cupula (gray line) is dominated by the stiffness provided by the kinocilia (green line) in the proximal region. The stiffness of the cupular matrix provides a substantially more flexible structure in the distal region, where kinocilia are absent.