The shocking truth about electric cá 

The shocking truth about electric fish: Genomic basis for the convergent evolution of electric organs

Scientists have found how the electric fish\'s jolt evolved. Biologists identified the regulatory molecules involved in the genetic and developmental pathways that electric fish have used to convert a simple muscle into an organ capable of generating a potent electrical field.

New research by a team led by UW-Madison biochemistry Professor Michael Sussman shows that electric fish, including the electric eel, evolved their electric organ six times independently over the course of evolutionary history. Sussman\'s team identified the molecular levers and developmental pathways that all six lineages of electric fish worldwide have in common, resolving a longstanding mystery of what scientists call convergent evolution, a problem Darwin himself pondered.

Credit: Jason Gallant, Michigan State University

, a team of researchers 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, Washington identifies the regulatory molecules involved in the genetic and developmental pathways that electric fish have used to convert a simple muscle into an organ capable of generating a potent electrical field.

The work establishes the genetic basis for the electric organ, an anatomical feature found only in fish and that evolved independently half a dozen times in environments ranging from the flooded forests of the Amazon to murky marine environments.

"These fish have converted a muscle to an electric organ," explains Sussman, a professor of biochemistry and director of the UW-Madison Biotechnology Center, who first undertook the exploration of the electric organ almost a decade ago. The study published in

provides evidence to support the idea that the six electric fish lineages, all of which evolved independently, used essentially the same genes and developmental and cellular pathways to make an electric organ, needed for defense, predation, navigation and communication.

"What is amazing is that the electric organ arose independently six times in the course of evolutionary history," says Lindsay Traeger, a UW-Madison graduate student in genetics and a co-lead author of the new report along with Jason Gallant, an assistant professor of zoology at Michigan State University.

Adds Gallant: "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.

Worldwide, there are hundreds of electric fish in six broad lineages. Their taxonomic diversity is so great that Darwin himself cited electric fishes as critical examples of convergent evolution, where unrelated animals independently evolve similar traits to adapt to a particular environment or ecological niche. The new work, which includes the first draft assembly of the complete genome of an electric fish, the South American electric eel, identifies the genetic factors and developmental paths the animals used to create an organ that, in some instances, can deliver a jolt several times more powerful than the current from a standard household electrical outlet.

Electric fish have long fascinated humans. The ancient Egyptians used the torpedo, an electric marine ray, in an early form of electrotherapy to treat epilepsy. Much of what Benjamin Franklin and other pioneering scientists learned about electricity came from studies of electric fish. In Victorian times, parties were organized where guests would form a chain to experience the shock of an electric fish.

"Only vertebrates have evolved this and only among fishes," notes James Albert, a professor of biology at the University of Louisiana and a co-author of the new study. "You need water as a conductor."

The electric organ is used by fish in murky environments to communicate with mates, navigate, stun prey and as a shocking defense, probably a reason why the muddy Amazon and its tributaries teem with electric fish, including the electric eel, the most potent of them. Not really an eel but a fish more closely related to the catfish, the electric eel produces a jolting electric field of up to 600 volts, about 100 volts per foot of fish, notes Albert.

"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," says Sussman. "Since all of the visceral organs are near the face, the remaining 90 percent of the fish is almost all electric organ."

As a means of communication and navigation in the dark, the generation of electric fields by fish works much the same as echolocation does for bats, says Albert. "These fish are nocturnal and the vast majority of them live at the bottom of a very muddy river, the Amazon."

All muscle cells have electrical potential. Simple contraction of a muscle will release a small amount of voltage. But at least 100 million years ago some fish began to amplify that potential by evolving from muscle cells another type of cell called an electrocyte -- larger cells, organized in sequence and capable of generating much higher voltages than those used to make muscles work.

"If you remove the ability of the muscle cell to contract and change the distribution of proteins in the cell membrane, now all they do is push ions across a membrane to create a massive flow of positive charge," explains Traeger.

The "in-series alignment" of the electrocytes and unique polarity of each cell allows for the "summation of voltages, much like batteries stacked in series in a flashlight," says Sussman.

The additional current required for the power comes from the fact that an eel body contains many millions of such "flashlights" working together and firing their electrical discharge simultaneously.

In addition to sequencing and assembling DNA from the electric eel genome, the team produced protein sequences from the cells of the electric organs and skeletal muscles of three other electric fish lineages using RNA sequencing and analysis. A computationally intense comparative study of the sequences showed that electric organs in fish worldwide used the same genetic tools and cellular and developmental pathways to independently create the electric organ.

"I consider \'exotic\' organisms such as the electric fish to be one of nature\'s wonders and an important \'gift\' to humanity," says Sussman. "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. 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 electrocytes for generating electrical power in bionic devices within the human body or for uses we have not thought of yet."

The above story is based on materials provided by University of Wisconsin-Madison.

J. R. Gallant, L. L. Traeger, J. D. Volkening, H. Moffett, P.-H. Chen, C. D. Novina, G. N. Phillips, R. Anand, G. B. Wells, M. Pinch, R. Guth, G. A. Unguez, J. S. Albert, H. H. Zakon, M. P. Samanta, M. R. Sussman. Genomic basis for the convergent evolution of electric organs.

University of Wisconsin-Madison. "The shocking truth about electric fish: Genomic basis for the convergent evolution of electric organs." ScienceDaily. ScienceDaily, 26 June 2014. <www.sciencedaily.com/releases/2014/06/140626141652.htm>.

University of Wisconsin-Madison. (2014, June 26). The shocking truth about electric fish: Genomic basis for the convergent evolution of electric organs. ScienceDaily. Retrieved July 1, 2014 from www.sciencedaily.com/releases/2014/06/140626141652.htm

University of Wisconsin-Madison. "The shocking truth about electric fish: Genomic basis for the convergent evolution of electric organs." ScienceDaily. www.sciencedaily.com/releases/2014/06/140626141652.htm (accessed July 1, 2014).

July 1, 2014 � A new generation of miniature biological robots is flexing its muscle. Engineers have demonstrated a class of walking \'bio-bots\' powered by muscle cells and controlled with electrical pulses, giving ...

Biochemistry; Artificial Intelligence; Biology; Biotechnology and Bioengineering

Tags Reveal Chilean Devil Rays Are Among Ocean\'s Deepest Divers

July 1, 2014 � Thought to dwell mostly near the ocean\'s surface, Chilean devil rays (Mobula tarapacana) are most often seen gliding through shallow, warm waters. But a new study reveals that these large and ...

Marine Biology; Fish; Oceanography; Earth Science

Bringing the Bling to Antibacterials: New Way to Combat Bacterial Biofilm Formation With Titanium Encrusted With Gold Nanoparticles

July 1, 2014 � Bacteria love to colonize surfaces inside your body, but they have a hard time getting past your skin. Surgeries to implant medical devices give such bacteria the opportunity needed to gain entry ...

Insect Diet Helped Early Humans Build Bigger Brains: Quest for Elusive Bugs Spurred Primate Tool Use, Problem-Solving Skills

July 1, 2014 � Figuring out how to survive on a lean-season diet of hard-to-reach ants, slugs and other bugs may have spurred the development of bigger brains and higher-level cognitive functions in the ancestors ...

Monkeys; Animal Learning and Intelligence; Nutrition Research; Evolutionary Biology

Reducing Deer Populations May Reduce Risk of Lyme Disease

July 1, 2014 � Reduced deer populations can lead to a reduction in Lyme disease cases, researchers in Connecticut have found that after a 13-year study was conducted. White-tailed deer serve as the primary host for ...

Lyme Disease; Joint Pain; Spiders and Ticks; Pain Control

Key to Adaptation Limits of Ocean Dwellers: Simpler Organisms Better Suited for Climate Change

July 1, 2014 � The simpler a marine organism is structured, the better it is suited for survival during climate change, researchers have discovered this in a new meta-study. For the first time biologists studied ...

Marine Biology; Nature; Global Warming; Environmental Awareness

New Analysis of \'Swine Flu\' Pandemic Conflicts With Accepted Views on How Diseases Spread

July 1, 2014 � New analysis of the 2009 H1N1 influenza pandemic in the US shows that the pandemic wave was surprisingly slow, and that its spread was likely accelerated by school-age ...

Bird Flu; Influenza; Bird Flu Research; Public Health

Foodborne Bacteria Can Cause Disease in Some Breeds of Chickens After All

July 1, 2014 � Contrary to popular belief, the foodborne pathogen Campylobacter jejuni is not a harmless commensal in chickens but can cause disease in some breeds of poultry according to research. Campylobacter ...

It\'s a Girl! Gene Silencing Technology Alters Sex of Prawns

June 30, 2014 � Scientists have developed a novel method for generating single-sex populations of prawns. This could be used to boost the productivity of aquaculture farms and even as a biocontrol measure against ...

Mating and Breeding; Genetics; Agriculture and Food; Ecology Research

DNA Analysis Reveals That Queen Bumblebees Disperse Far from Their Birthplace Before Setting Up Home

June 30, 2014 � Researchers are closer to understanding patterns of family relatedness and genetic diversity in bumblebees. The findings could help farmers, land managers and policy makers develop more effective ...

New Species; Mating and Breeding; Evolutionary Biology; Biology

Chilean Devil Rays Among Ocean\'s Deepest Divers

Insect Diet Gave Early Humans Bigger Brains

Reducing Deer May Reduce Risk of Lyme Disease

Climate Change: Simpler Animals Better Suited?

School Kids Accelerated Spread of 2009 H1N1 Flu

Queen Bumblebees Move Far from Their Birthplace

from AP, Reuters, AFP, and other news services

Newsy (July 1, 2014) � Kendall Jones has hunted big game for years. Now people are outraged by photos in which she poses with animals she\'s killed, including an elephant. Video provided by Newsy

AP (July 1, 2014) � A Wisconsin woman who lost her diamond wedding ring five years ago had given up all hope of finding it. But it turns out her dog had it all along. (July 1) Video provided by AP

Kids With ADHD More Likely To Abuse Drugs: Study

Newsy (June 30, 2014) � Researchers don\'t know what causes this link but note those with ADHD and those with substance abuse problems tend to have some behaviors in common. Video provided by Newsy

AP (June 29, 2014) � Tourists and surfers saw a Southern Right Whale near Sydney Beach, Australia. The massive mammal rested for a few hours about 500 feet offshore before heading off to sea. (June 29) Video provided by AP

Hubble Finds Two Kuiper Belt Objects to Probe

Electronic Switch Just Three Atoms Thick?

Human Embryonic Stem Cells Coaxed to Organize

All Oceans Have Plastic Debris On Their Surface

How a Fish Can Fry: Scientists Uncover Evolutionary Clues Behind Electric Fish

Apr. 29, 2014 � Take a muscle cell, modify it over millions of years, and you end up with an exciting and literally shocking evolutionary result: the electric fish. The authors of a new study speculate that the ...

New Electric Fish Genus, Species Discovered in Brazil\'s Rio Negro

Apr. 22, 2014 � Discovery of a new species of electric knife fish in the Amazon Basin in Brazil is leading to a new interpretation of classifications and interrelationships among closely related groups. As the ...

New Genus of Electric Fish Discovered in \'Lost World\' of South America

Sep. 25, 2013 � A previously unknown genus of electric fish has been identified in a remote region of South America by team of international researchers. The Akawaio penak, a thin, eel-like electric fish, was ...

AC or DC? Two Newly Described Electric Fish from the Amazon Are Wired Differently

Aug. 28, 2013 � Two new species of weakly electric fishes from the Amazon with some unusual characteristics. Often collected together and so similar in many respects that they have been mistaken for a single ...

Sep. 28, 2009 � Just as people plug in to computers, smart phones and electric outlets to communicate, electric fish communicate by quickly plugging special channels into their cells to generate electrical impulses, ...

AIDS scientist pleads not guilty to faking study

Unapproved device buys time for new pair of lungs

US ship arrives in Italy port for Syria weapons

Officials clash over beach contamination warnings

Johns Hopkins resumes talks with union over wages

Obamacare exchanges not properly verifying applicant data: watchdog

Death toll in W.African Ebola outbreak rises to 467: WHO

Frozen testicle tissue yields healthy baby mice

Devil ray\'s lazy reputation takes a dive

Norwegian energy groups to build new British wind farm

Lost for 60 years, ring turns up in dry Texas lake

Google buys Songza streaming music service

Bitcoin auction had one winner: U.S. Marshals Service

Google buys music streaming service Songza

U.S. sues T-Mobile USA, alleges cramming of bogus charges on bills

Get the latest science news with ScienceDaily\'s free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?

About ScienceDaily �|� Editorial Staff �|� Awards & Reviews �|� Contribute News �|� Advertise with Us �|� Privacy Policy �|� Terms of Use

Content on this website is for informational purposes only. It is not intended to provide medical or other professional advice.

Views expressed here do not necessarily reflect those of ScienceDaily, its staff, its contributors, or its partners.

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.

Read ScienceDaily\'s top medical sciences and health stories, or browse by topic:

Read ScienceDaily\'s top physical sciences and technology stories, or browse by topic:

Read ScienceDaily\'s top biological sciences and environment stories, or browse by topic:

Read ScienceDaily\'s strange and offbeat stories, or browse by topic:

Read ScienceDaily\'s top society and education stories, or browse by topic:

Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins