How Evolution Gave Some Fish Their Electric Powers

Electric eels are usually 6.5 long and weigh about 45 pounds. Jason Gallant

The electric eel is one of the many creatures Charles Darwin sliced up and examined in his years aboard the H.M.S. Beagle. When he cut it open, he found that 80 percent of the fish’s body was taken up by three organs made of what looked like muscle tissue, but not quite. This is where the animal makes electricity.

After finding similar organs in other fish, Darwin correctly deduced that the lineages—six in all—came to the same adaptive conclusion independent of one another. Until now, though, no one has known how similar they were. According to a paper published today in Science, at least three of the six lineages evolved their electric organs through the same genetic pathways.

Taxonomically, these lineages were too distantly related to have inherited the organ from a common ancestor. In Origin of Species Darwin wrote that “Natural selection, working for the good of each being and taking advantage of analogous variations, has sometimes modified in very nearly the same manner two parts in two organic beings.” Biologists call this convergent evolution.

“Imagine houses in built different parts of the country. The house in New Mexico may look different from a house in New England, but they’re built using the same basic structural parts,” said co-author Jason Gallant, a biologist at Michigan State University.

The team started with the electric eel—not actually an eel, but a type of knifefish. They took took DNA samples from cells in its electric organ—called electrocytes—and compared it to the DNA from other tissue, including its muscle, kidney, and nerve cells. From about 25,000 genes, about 100 stood out. In muscle cells, which electrocytes evolved from, these genes control the ability to contract. In the eel, these genes were highly suppressed. ”We think these are the ones that turn off the ‘muscleness’ of a muscle cell and turn on the current-generating ability,” said co-author Michael Sussman, a geneticist from the University of Wisconsin-Madison.

The electric organ discharge starts when the fish’s brain sends signals that release a neurotransmitter onto the electrocytes. This opens tiny molecular doors that allow positively-charged sodium ions to rush in, creating an electric current. Our brain cells operate by moving ions around in a similar way.

After they’d isolated the genes in electric eels, the researchers looked at the RNA—the acid that encodes genes from DNA—of two other lineages of electric fishes. They found that the same genes were similarly manipulated, all with the same effect: Tweaking the muscle cell genetic code as a blueprint for a little organic battery. 

The researchers studied species of fish from the three lineages with black fish icons: elephantfish, catfish, and electric eels. Jason Gallant et al

Each electrocyte only turns out about 50 millivolts of electricity, but they are stacked end-to-end in the organ, so their charges accumulate like batteries in a Maglite. The eel’s electric organs (which take up about four-fifths of its body) can generate up to 600 volts. “There’s enough power in the eel’s electric organ to kill anything it wants,” said Sussman.

In each of the six electric fish lineages, there are several to hundreds of species. In Africa, there are over 200 species of electric elephantfish, and Gallant says that number has grown a lot in relatively recent evolutionary history. This is because they use their electric charge to communicate, in addition to helping them navigate the roots and rocks in their murky, river habitats. (Using electricity for predation, like the electric eel does, is a rarity among electric fish species.)

Each species of African elephantfish has its own specific frequency or pattern, a niche that helps it distinguish its own kind from the crowded, muddy water.

“What’s really interesting is that this diversity of electric discharges—really, the invention of new electric discharges—might be driving new species,” said Gallant.

The recording below is the amplified sound of the electrical frequency that the Brienomyrus brachyistus elephantfish uses during courtship.

Sussman believes this research might have practical applications. Someday, he says, scientists might be able to create electrocytes from human stem cells, which could power biomedical devices like pacemakers or insulin pumps. But this, he says, is probably years away.

“I’m not promising people that you’ll have electric organs and be able to charge your cell phones right away,” he said, “but I’m hoping that this paper might inspire research that will be able to create electrocytes.”

However, the air we live in doesn’t conduct electricity like water does, so you probably don’t have to worry about getting shocked by a bio-engineered super villain.

ORIGINAL: Wired

By Nick Stockton
06.26.14 |

This is the oldest fragment of Earth ever found

You're looking at the oldest fragment of Earth ever found: a zircon 4.375 billion years old, something that has deep implications in our understanding of the planet's formation. While some scientists said other samples weren't genuine, new research just published in the journal Nature Geoscience proves that this is the real McCoy.

John Valley—a geochemist at the University of Wisconsin, Madison—and his colleagues, used a new technique called atom-probe tomography. This technology allowed the scientists to count individual lead atoms within the zircons found in Jack Hills, a range in the midwest of Western Australia.

The previous method—which counted the number of lead isotopes—was imperfect because the radioactive uranium trapped inside the zircons moves lead isotopes around as it decays. According to Valley, "if there's a process by where lead can move from one part of the crystal to another place, then the place where lead is concentrated will have an older apparent age and the place from where it moves will have a younger apparent age."

Valley claims that atom-probe tomography doesn't suffer from this defect, something that has allowed them to obtain the definitive age: "We've proved that the chemical record inside these zircons is trustworthy."

Their research demonstrates that these zircons were formed only 100 million years after the massive cosmic impact that smashed Earth to create the Moon as we know it today. Since they think the crystals formed from granodiorite or tonalite—materials that are rich in water—this means that Earth cooled down really quickly. So fast, in fact, that it's possible there was water on its surface, says Valley:

The zircons show us the earliest Earth was more like the Earth we know today. It wasn't an inhospitable place.

ORIGINAL: Sploid

Cervical Cancer and Pre-Cancer Cervical Growths Require Single HPV Protein

ORIGINAL: ScienceDaily

ScienceDaily (Sep. 14, 2012) — Human papillomavirus (HPV) has long been implicated in cervical cancer, but details of how it happens have remained a mystery. Now researchers at the University of Wisconsin-Madison have found that a single HPV protein is required for cervical cancer and even pre-cancer growths in the cervix to survive.

In anticipation of a clinical trial in humans, the scientists and their collaborators are moving quickly to test if a gene-silencing technique could cripple the protein and eliminate cervical cancer and pre-cancerous growths in specially-bred mice.

The study, appearing online in Cancer Research, is the first to show that the protein works in living animals and in pre-cancerous growths as well as full-blown cervical cancer.

Cervical cancer is relatively rare in the United States, thanks to the widespread use of Pap smears as a screening tool. But pre-cancer lesions in the cervix, called cervical inter-epithelial neoplasias, or CINs, are common.

Low-grade CINs are typically left alone because most will shrink and pose no problem. But women with high-grade CINs have a 10 percent chance of getting cervical cancer, says Dr. Paul Lambert, senior author on the paper. In addition, surgical treatment of high-grade CINs carries a risk of excessive bleeding and even infertility.

Scientists know that two HPV cancer-causing proteins, or oncoproteins -- E6 and E7 -- are always expressed in cervical cancer. Lambert and his team at UW's McArdle Laboratory of Cancer Research conducted experiments in cultured cell lines that suggested that the oncoproteins caused cervical cancer as well as anal and head and neck cancers. The researchers also learned that E7 had a much greater ability than E6 to cause cancer.

Other studies in different types of cancers suggested that when oncoproteins were involved, they needed to work together--blocking the expression of both often led to a more effective reduction of tumors than blocking either one alone.

But Lambert, a member of the UW Carbone Cancer Center, was intrigued with E7's power.

"In thinking of treatments, we wondered in this case if we could target just one oncoprotein, the most potent one, rather than two, which could be much more complicated," he says.

Dr. Sean Jabbar and Soyeong Park in the Lambert laboratory created and bred mice in which they could control the expression of both E7 and E6. They found that when he turned off E7 but left E6 on, the cervical cancers and CINs melted away.

"This told us that E7 should be an excellent therapeutic target for HPV-associated cancers, including pre-cancerous CINs," Lambert says.

If the gene-silencing experiments that are expected to take place soon prove effective, there's a good chance that the blocking approach could be used to control the disease without surgery.

Women in developing countries might benefit greatly, Lambert adds.

"Cervical cancer is prevalent around the world in places where screening does not exist and surgery is not available," he says.