Fig. 9. Regional contribution of the fish body to the electromotive force during development. The contribution of regions corresponding to 1% of the fish length was estimated by plotting the regional electromotive force normalized by the length of the fish region in which it is generated (electromotive force per 1% of fish length) as a function of the position of the center of the region along the fish body (distance from the jaw expressed as percentage of fish length). The early negativity shows two components of different spatial origin and maturation times. In larvae (A,B), the generated electromotive force is largest at the rostral portions of the generating electric organs and shows a slow decay as a function of the distance from the jaw. Note that the peak of the curve moves rostrally as the fish grows (arrows in B). This coincides with the smooth wave observed in time-based recordings and therefore should be classified as V₁ (light gray box). (C) A second component appears in juveniles of about 47–52 mm length and (D) is clearly defined beyond 55 mm of fish length. This component corresponds to the fast component generated at the center of the fish body, V₂ (dark gray box).