Evolution of Electric Fish

The African mormyrids and South American gymnotids appear to have no common ancestors, yet have developed remarkable similarities through convergent evolution. Most of the common phylogenetic relationships are in morphological characteristics; however, relationships have also been shown on the physioloical and molecular levels. The gymnotids have been shown to be a sister group to a family of electroreceptive catfish (Alves-Gomes, et al. 1995). The electrorecptive ability of the catfish allows them to percieve the low frequency of pulse type weakly electric fish. It has been hypothesized that the South American hummers may have evolved from the clickers because the catfish can not detect the hummer's higher frequency EOD's (Hagedorn, unpublished). Many hummers have also evolved a neuronally-derived electric organ in place of the more primitive myogenic organ, allowing them to further increase the frequency of EOD emmision.