Fig. 2. High-speed microscopy was used to track the position of the glass fiber used for stiffness measurements. (A) Individual larvae were inserted into a bed of agar with their tails pinned beneath a dull probe (triangle) under the objective lens of a fixed-stage compound microscope. When held in this position, the tip of a glass fiber was pressed against the middle of an individual neuromast (inset). (B) During experiments, the position of the fiber was recorded with a high-speed video camera mounted on the microscope. Video recordings were analyzed to track the movement of the edge of the glass fiber. A single video frame from one of these recordings is shown with the edge (purple line) that was found for the prescribed pixel stripe. (C) The pixel intensity along this stripe is shown with a curve fit (green line). (D) The first derivative of the fitted line with respect to position was used to find the position of maximum change in pixel intensity. This point was interpreted as the edge of the glass fiber.