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Abstract

Gymnarchus niloticus, one of the less-well-known electroreceptive teleost fishes, is the only African mormyriform fish with a wavelike or tone electric organ discharge. For Gymnarchus, this is the first detailed description of the lateral line lobe, vestibulolateral lobe, cerebellum, and midbrain torus semicircularis—central electrosensory structures. Brain organization in Gymnarchus closely resembles that of mormyrids. In particular, the lateral line lobe is a bilateral structure with three cortical zones—ventral, dorsal, medial—and a fourth central zone of large cells. The convergent evolution of the electric sense of mormyriform and gymnotoid fish, and its central representation, is discussed.