New research has been published demonstrating that the six electric fish lineages, all of which evolved independently, used basically the same genes and developmental and cellular pathways to make an electricity-generating organ for defense, navigation, predation, and communication.
Research was published in the journal Science this week. The study was led by Michael Sussman of The University of Wisconsin-Madison, Harold Zakon of The University of Texas at Austin and Manoj Samanta of the Systemix Institute in Redmond, Wash.
Fish evolved an electric organ independently half a dozen times in environments that range from the forests of the Amazon to marine environments, according to a University of Wisconsin-Madison press release.
Charles Darwin once called electric fish prime examples of convergent evolution, where unrelated animals independently evolve similar traits to adapt to a specific environment.
"The surprising result of our study is that electric fish seem to use the same 'genetic toolbox' to build their electric organ," despite the fact that they evolved independently, says Jason Gallant, an assistant professor at Michigan State University and co-lead author of the study, according to the release.
To conduct their study, the researchers gathered complete genomes of the most potent electric eel, electric fish, and the genetic sequences involved in constructing electric organs and skeletal muscles from three fish lineages that evolved electric organs independently.
Zakon, professor of biology and neuroscience in The University of Texas at Austin's College of Natural Sciences, determined that some of the genes, depending on how they are regulated, can turn simple muscle tissue into an electric organ.
"An exciting result of this work is that it pinpoints steps in various cellular pathways that are the most likely to evolve in other animals as well," says Zakon, according to the release. "For example, the pathways that transmit electrical pulses in the vertebrate heart, including our own heart, derive from muscles. We find that electric organs in fish and these pathways in our hearts share some of the same regulatory genes."
The electric organ is used by fish in "murky environments" in order to navigate, stun prey, and communicate with mates. The electric eel produces a jolting electric field of up to 600 volts, about 100 volts per foot of fish.
The "in-series" alignment of the electrolytes and polarity of each cell allows for the "summation of voltages, much like batteries stacked in series in a flashlight," said Sussman, according to the release.
An electric eel body contains millions of such "flashlights," which work together and fire their electrical discharge at the same time.
"Our study demonstrates nature's creative powers and its parsimony, using the same genetic and developmental tools to invent an adaptive trait time and again in widely disparate environments," said Susmann, a professor of biochemistry and director of the UW-Madison Biotechnology Center, according to the release. "By learning how nature does this, we may be able to manipulate the process with muscle in other organisms, and in the near future, perhaps use the tools of synthetic biology to create electrolytes for generating electrical power in bionic devices within the human body or for uses we have not thought of yet."
The study was funded by the National Science Foundation, the W.M. Keck Foundation and the National Institutes of Health.
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