A QUANTITATIVE-ANALYSIS OF PASSIVE ELECTROLOCATION BEHAVIOR IN ELECTRIC FISH

Weakly electric fish of the families Gymnotidae and Hypopomidae (Gymno tiformes) are able to locate the electric discharges from conspecifics or from dipole electrodes, and they demonstrate this by making rapid, well-directed approaches toward these electrical sources. A video tra cking system was used to follow the movements of electric fish in a la rge tank and an analytic method was used for computing the direction a nd magnitude of the electric field anywhere within the cylindrical tes t tank. Using a static analysis method, we describe the posture of tes t fish relative to the electric fields during their approaches to stat ionary or moving electrical stimuli. Using a dynamic analysis, we exam ine the movements of the fish including the sign and magnitude of velo city and bending in response to electric fields. Electric fish seek to maintain a zero error angle between their body orientation and the lo cal electric field. They do so by bending their body in the direction of the local electric held. The response has a delay of approximately 0.5 s. Swimming in reverse inverts the direction of the bend. These fi sh also use 'V-turns' to redirect their swim directions when encounter ing rapidly-changing electric fields.