Researchers sequenced the genome of the electric eel for the first time, revealing how aquatic creatures with electric organs evolved.
The team found fish with electric organs evolved six different times in history to produce electricity outside of their bodies, a Michigan State University news release reported.
"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," Jason Gallant, MSU zoologist and co-lead author of the paper, said in the news release. "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.
"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.
