All of the fish pictured here are in the family Mormyridae and can produce and sense electric fields. In the top group of fish (subfamily Mormyrinae), electric discharges have evolved quickly, resulting in dramatically different pulses of electricity among closely related species. In the bottom group of fish (subfamily Petrocephalinae), all of the species have similar pulses. The difference arises because the top group has the anatomical features needed to exploit the signal space, such as the anatomy needed to make different pulses and the sensory and analytical ability to perceive small differences in pulse shape.
A Brienomyrus brachyistius, commonly known as the black whale. A weakly electric fish native to Africa, B. brachyistius communicate with each other by means of electric discharges whose waveform, or shape, allow it to recognize fish of the same species, including individual fish.
These fish were the subject of research by Bruce Carlson, Ph.D., an assistant professor of biology at Washington University in St. Louis, Mo., who is studying this African family of weakly electric fish. Carlson found that different species in the mormyrid family communicate using different electric signals, which identifies the different species. When seeking a mate they can find partners of their own kind by listening for their preferred electric dialect. To learn more about this research, visit Carlson's website Here. This research was supported by a grant from the National Science Foundation (IOS 08-18390). [See also, Carlson B.A., Hasan S.M., Hollmann M., Miller D.B., Harmon L.J., Arnegard M.E. (2011) Brain evolution triggers increased diversification of electric fishes. Science 332:583-586.]
(Date of Images: 2011)
Credit: Image by Bruce A. Carlson. Photographs by Sebastien Lavoue, Carl Hopkins, John Sullivan and Matthew Arnegard.