Weakly Electric Fish as Models for Underwater Robots: The Use of Active Electrolocation for the Perception of 3-Dimensional Objects in Complex Environments

Introduction Since the early 1950s it is known that so-called weakly electric fish generate electrical signals with a special electric organ in their tail (Lissmann, 1951). During each electric organ discharge (EOD) an electric field builds up around the fish (Lissmann, 1958). The animal perceives its own electric emissions with epidermal electroreceptor organs (Szabo, 1967). Each object near the fish changes the electric field in a specific way and this projects an ‘electric image’ onto the skin surface (Caputi, 1998; Rasnow, 1996; von der Emde 1999). Even in complete darkness fish can detect and discriminate between objects by analysing their electric images a process called active electrolocation (Bastian, 1986). It is known that the African mormyrid Gnathonemus petersii can electrically detect object features, such as material, size, shape and distance (von der Emde 2004, von der Emde 2006, von der Emde 2010). The active electrolocation system of weakly electric fish might serve as a model for designing sensory systems of underwater robots. Thus, studying the perceptional capabilities of the animals might provide important insights towards the potential performance of a technical electrolocation system.