For the first time, the genome of the electric eel has been sequenced. This discovery has revealed the secret of how fishes with electric organs have evolved six times in the history of life to produce electricity outside of their bodies. The research published in the current issue of Science sheds light on the genetic blueprint used to evolve these complex, novel organs.
It was co-led by Michigan State University, University of Wisconsin-Madison, University of Texas-Austin and the Systemix Institute.
“It’s truly exciting to find that complex structures like the electric organ which evolved completely independently in six groups of fish seem to share the same genetic toolkit,” said Jason Gallant, MSU zoologist and co-lead author of the paper. “Biologists are starting to learn, using genomics that evolution makes similar structures from the same starting materials even if the organisms aren’t even that closely related.”
There are so many species that have this ability that Darwin said electric fish were an example of convergent evolution where unrelated animals independently develop the same traits. All muscle and nerve cells can potentially be electric, muscle contractions release a small amount of voltage. Some fish started to amplify this potential between 100 and 200 million years ago.
Although all muscle cells demonstrate electrical potential, groups of electric fish have evolved specialized muscle cells called electrocytes. Developing over millions of years, these electrocytes are capable of generating electric fields that have a much higher voltage than typical muscle cells. The electric eel, for example, is capable of producing an electric field of up to 600 volts.
“The electric organ is used by fish to communicate with potential mates, navigate murky environments, mark territory, stun prey and evade predation. These electric fish use electric fields to navigate in much the same way that bats use echolocation to sense their environment,” says James Albert, a professor of biology at the University of Louisiana.
“Evolution has removed the ability of muscle cells to contract and changed the distribution of proteins in the cell membrane, now all electrocytes do is push ions across a membrane to create a massive flow of positive charge,” Lindsay Traeger, U-W graduate student and co-author of the study said in the news release.
“Both the in-series alignment of the electrolytes and the unique polarity of each cell allows for the summation of voltages, much like batteries stacked in series in a flashlight,” Michael Sussman, U-W biochemist said in the news release.
The additional current comes from millions of these ‘batteries’ in the eel’s body that work together to fire electricity at the same time.
The new work provides the first electric fish genome sequence assembly, it also identifies the developmental pathways that animals use to develop organs.
The work provides the first electric fish genome sequence assembly.
The research was funded by the National Science Foundation, the W.M. Keck Foundation and the National Institutes of Health.