The genome of the electric eel has been sequenced for the first time, leading to some shocking findings.
Fish with the ability to generate significant electric fields outside their bodies have evolved at least six times in the history of the Earth, paleontologists believe. This latest study examines how this rare ability is coded in the genetic structure of life. Researchers from Michigan State University, the University of Texas-Austin, University of Wisconsin-Madison and the Systemix Institute collaborated in the study.
"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," Jason Gallant, a zoologist with Michigan State University, said.
All muscle and skin cells have electrical potential, which help drive muscles and produce motion. Electric eels have developed special cells called electrocytes; modified muscle cells that help amplify the voltage of the signals. They are stacked in series (positive to negative) like batteries in a flashlight. This ability evolved between 100 and 200 million years ago.
Cellular pathways used by the electrical signals, identified by the researchers, were similar to our own bodies.
"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," Harold Zakon of The University of Texas at Austin, said.
Hundreds of species of electric eels have evolved worldwide, a fact which caught the attention of one of the grandfathers of modern biology, Charles Darwin. He cited the animals as an example of convergent evolution, where different species develop similar adaptations to environmental conditions.
Zakon investigated how genetic instruction to create the electrocytes is managed by DNA. This work details the underlying mechanisms for this ability, found only in fish.
Electric eels are not true eels, but long, thin fish, that grow up to six feet long. They can deliver shocks as powerful as 600 volts. Electric fish are found in diverse environments from flooded forests in the Amazon to turbid waters thousands of miles away. In these dark environments, the electrical fields can help the animals communicate and navigate. The ability can also be used for offense or defense, stunning prey, or fighting off attackers.
Ancient Egyptians use the torpedo, a type or electric ray to treat epilepsy. Scientists from the Renaissance to the 19th century learned much of what they knew about electricity from the fish.
"A six-foot eel is a top predator in the water and is in essence a frog with a built-in five-and-a-half-foot cattle prod," Zakon said.
