How a fish can fry: scientists uncover evolutionary clues behind electric fish.

Take a muscle cell, modify it over millions of years, and you end up with an exciting and literally shocking evolutionary result: The electric fish. Two groups of electric fish, one in Africa (Mormyroids) and one in South America (Gymnotiforms), have independently evolved sophisticated communication systems using these cells. Both groups of fish are incredibly diverse; one species, the famous electric eel of South America, even evolved such strong and intense electric signals that it can electrocute its prey. During an ancestral gene duplication event, the voltagegated sodium channel of muscle, Scn4a, duplicated to Scn4aa and Scn4ab. Thompson et al. (2014) showed that the Scn4aa sodium channel gene may have an evolutionary bias over its twin to take part in novel cell types derived from muscle cells. They speculate that the down-regulation of the Scn4aa gene leads to quicker evolution and adaptation. Also, in an exciting discovery, they found this same Scn4aa gene expression pattern in a species of fish that uses sound to communicate, showing another extraordinary evolutionary adaption from the ancient gene duplication. The results provide a compelling hypothesis that gene duplications and gene “expression drift” may be a more common evolutionary phenomenon in the development of new organ systems. “By peering into the evolutionary history of these genes we’re starting to understand why the same gene plays a role in the repeated evolution of these unusual organs,” said Thompson.