(Press-News.org) In animals that reproduce by internal fertilization, as humans do, you'd think a penis would be an organ you couldn't really do without, evolutionarily speaking. Surprisingly, though, most birds do exactly that, and now researchers reporting in the Cell Press journal Current Biology on June 6 have figured out where, developmentally speaking, birds' penises have gone.
It turns out that land fowl, which have only rudimentary penises as adults, have normally developing penises as early embryos. Later in development, however, the birds turn on a genetic program that leads their budding penises to stop growing and then wither away.
"Regulation of the balance between cell proliferation and cell death is essential for controlled growth and development," said Martin Cohn of the Howard Hughes Medical Institute and University of Florida, Gainesville. "Too much cell division or too little cell death can lead to overgrowth or mis-regulated growth, as in cancer. If the balance is tipped in the other direction, deficient cell division or excess cell death can lead to underdevelopment or even absence of a tissue or organ.
"Our discovery shows that reduction of the penis during bird evolution occurred by activation of a normal mechanism of programmed cell death in a new location, the tip of the emerging penis."
A critical gene in the process is one called Bmp4. In chicken development, Bmp4 switches on and the birds' developing genitals shrink away. In more well-endowed ducks and emus, that gene stays off and their penises continue to grow.
It's not entirely clear why chickens and other birds would have lost their penises, said graduate student Ana Herrera, lead author of the study, but it may be that the loss leaves hens with greater control over their reproductive lives.
The findings could have implications for understanding evolutionary loss more broadly. (Think of snakes and their lost limbs, as another example.) They might yield some answers to medical questions as well.
"Genitalia are one of the fastest-evolving organs in animals, from mollusks to mammals," Cohn said. "It is also the case that genitalia are affected by birth defects more than almost any other organ. Dissecting the molecular basis of the naturally occurring variation generated by evolution can lead to discoveries of new mechanisms of embryonic development, some of which are totally unexpected. This allows us to not only understand how evolution works but also gain new insights into possible causes of malformations."
INFORMATION:
Current Biology, Herrera et al.: "Developmental Basis of Phallus Reduction During Bird Evolution."
How birds lost their penises
2013-06-06
ELSE PRESS RELEASES FROM THIS DATE:
Superb lyrebirds move to the music
2013-06-06
VIDEO:
When male superb lyrebirds sing, they often move their bodies to the music in a choreographed way, say researchers who report their findings in the Cell Press journal Current Biology...
Click here for more information.
When male superb lyrebirds sing, they often move their bodies to the music in a choreographed way, say researchers who report their findings in the Cell Press journal Current Biology on June 6. The findings add to evidence from human cultures around ...
Brain imaging study eliminates differences in visual function as a cause of dyslexia
2013-06-06
WASHINGTON — A new brain imaging study of dyslexia shows that differences in the visual system do not cause the disorder, but instead are likely a consequence. The findings, published today in the journal Neuron, provide important insights into the cause of this common reading disorder and address a long-standing debate about the role of visual symptoms observed in developmental dyslexia.
Dyslexia is the most prevalent of all learning disabilities, affecting about 12 percent of the U.S. population. Beyond the primarily observed reading deficits, individuals with dyslexia ...
Nuclear testing from the 1960s helps scientist determine whether adult brains generate new neurons
2013-06-06
The birth of new neurons in the adult brain sharpens memory in rodents, but whether the same holds true for humans has long been debated. A study published by Cell Press June 6th in the journal Cell reveals that a significant number of new neurons in the hippocampus—a brain region crucial for memory and learning—are generated in adult humans. The researchers used a unique strategy based on the amount of carbon-14 found in humans as a result of above-ground nuclear testing more than half a century ago. The findings suggest that new neurons are born daily in the human hippocampus, ...
Studies showing how bird flu viruses could adapt to humans offer surveillance and vaccine strategies
2013-06-06
Bird flu viruses are potentially highly lethal and pose a global threat, but relatively little is known about why certain strains spread more easily to humans than others. Two studies published by Cell Press June 6th in the journal Cell identify mutations that increase the infectivity of H5N1 and H7N9 viruses through improved binding to receptors in the human respiratory tract. The findings offer much-needed strategies for monitoring the emergence of dangerous bird flu strains capable of infecting humans and for developing more effective vaccines.
"Avian influenza viruses ...
Parents with heavy TV viewing more likely to feed children junk food
2013-06-06
Washington, DC (June 3, 2013) – If your preschooler thinks a cheeseburger is healthy, you may want to reconsider how you watch TV. A recent study by researchers at the University of Michigan found commercial TV viewing, as opposed to commercial-free digitally recorded TV or other media without food advertising, in the home was related to greater junk food consumption.
Kristen Harrison and Mericarmen Peralta, both of the University of Michigan, will present their findings at the 63rd Annual International Communication Association conference in London. Harrison and Peralta ...
Scientists coax brain to regenerate cells lost in Huntington's disease
2013-06-06
Researchers have been able to mobilize the brain's native stem cells to replenish a type of neuron lost in Huntington's disease. In the study, which appears today in the journal Cell Stem Cell, the scientists were able to both trigger the production of new neurons in mice with the disease and show that the new cells successfully integrated into the brain's existing neural networks, dramatically extending the survival of the treated mice.
"This study demonstrates the feasibility of a completely new concept to treat Huntington's disease, by recruiting the brain's endogenous ...
Spanish researchers writing in cell describe the 9 hallmarks of aging
2013-06-06
For some species, living twice as long in good health depends on no more than a few genes. When this fact was revealed by studies on worms three decades ago, it ushered in a golden age of ageing studies that has delivered numerous results, but also sown some confusion. The prestigious journal Cell is now publishing an exhaustive review of the subject that aims to set things straight and "serve as a framework for future studies." All the molecular indicators of ageing in mammals – the nine signatures that mark the advance of time – are set out in its pages. And the authors ...
Rutgers findings may predict the future of coral reefs in a changing world
2013-06-06
NEW BRUNSWICK, N.J. – Rutgers scientists have described for the first time the biological process of how corals create their skeletons – destined to become limestones – which form massive and ecologically vital coral reefs in the world's oceans.
In a publication in Current Biology, Tali Mass and her colleagues at the Rutgers Institute of Marine and Coastal Sciences show that specific proteins produced by corals can form limestones in test tubes. These proteins, secreted by corals, precipitate carbonate that forms the corals' characteristic skeleton.
"This is a first ...
Tumors disable immune cells by using up sugar
2013-06-06
Cancer cells' appetite for sugar may have serious consequences for immune cell function, researchers at Washington University School of Medicine in St. Louis have learned.
The scientists found that when they kept sugar away from critical immune cells called T cells, the cells no longer produced interferon gamma, an inflammatory compound important for fighting tumors and some kinds of infection.
"T cells can get into tumors, but unfortunately they are often ineffective at killing the cancer cells," said Erika Pearce, PhD, assistant professor of pathology and immunology. ...
Living fossils? Actually, sturgeon are evolutionary speedsters
2013-06-06
ANN ARBOR—Efforts to restore sturgeon in the Great Lakes region have received a lot of attention in recent years, and many of the news stories note that the prehistoric-looking fish are "living fossils" virtually unchanged for millions of years.
But a new study by University of Michigan researchers and their colleagues reveals that in at least one measure of evolutionary change—changes in body size over time—sturgeon have been one of the fastest-evolving fish on the planet.
"Sturgeon are thought of as a living fossil group that has undergone relatively slow rates of ...