Archive for the ‘penguin’ Category

Duck_chicken_penisRooster

Researchers have now unraveled the genetics behind why most male birds don’t have penises, just published in Current Biology.
[Ana Herrera et al, Developmental Basis of Phallus Reduction During Bird Evolution]

There are almost 10,000 species of birds and only around 3 percent of them have a penis. These include ducks, geese and swans, and large flightless birds like ostriches and emus. In fact, some ducks have helical penises that are longer than their entire bodies. But eagles, flamingos, penguins and albatrosses have completely lost their penises. So have wrens, gulls, cranes, owls, pigeons, hummingbirds and woodpeckers. Chickens still have penises, but barely—they’re tiny nubs that are no good for penetrating anything.

In all of these species, males still fertilise a female’s eggs by sending sperm into her body, but without any penetration. Instead, males and females just mush their genital openings together and he transfers sperm into her in a maneuver called the cloacal kiss.

To get to the root of this puzzle, researchers compared the embryos of chickens and ducks. Both types of birds start to develop a penis. But in chickens, the genital tubercle shrinks before the little guys hatch. And it’s because of a gene called Bmp4.

“There are lots of examples of animal groups that evolved penises, but I can think of only a bare handful that subsequently lost them,” says Diane Kelly from the University of Massachusetts in Amherst. “Ornithologists have tied themselves in knots trying to explain why an organ that gives males an obvious selective advantage in so many different animal species disappeared in most birds. But it’s hard to address a question on why something happens when you don’t know much about how it happens.”

That’s where Martin Cohn came in. He wanted to know the how. His team at the University of Florida studies how limbs and genitals develop across the animal kingdom, from the loss of legs in pythons to genital deformities in humans. “In a lab that thinks about genital development, one takes notice when a species that reproduces by internal fertilization lacks a penis,” says graduate student Ana Herrera.

By comparing the embryos of a Pekin duck and a domestic chicken, Herrera and other team members showed that their genitals start developing in the same way. A couple of small swellings fuse together into a stub called the genital tubercle, which gradually gets bigger over the first week or so. (The same process produces a mammal’s penis.)

In ducks, the genital tubercle keeps on growing into a long coiled penis, but in the chicken, it stops around day 9, while it’s still small. Why? Cohn expected to find that chickens are missing some critical molecule. Instead, his team found that all the right penis-growing genes are switched on in the chicken’s tubercle, and its cells are certainly capable of growing.

It never develops a full-blown penis because, at a certain point, its cells start committing mass suicide. This type of ‘programmed cell death’ occurs throughout the living world and helps to carve away unwanted body parts—for example, our hands have fingers because the cells between them die when we’re embryos. For the chicken, it means no penis. “It was surprising to learn that outgrowth fails not due to absence of a critical growth factor, but due to presence of a cell death factor,” says Cohn.

His team confirmed this pattern in other species, including an alligator (crocodilians are the closest living relatives of birds). In the greylag goose, emu and alligator, the tubercle continues growing into a penis, with very little cell death. In the quail, a member of the same order as chickens, the tubercle’s cells also experience a wave of death before the organ can get big.

This wave is driven by a protein called Bmp4, which is produced along the entire length of the chicken’s tubercle, but over much less of the duck’s. When Cohn’s team soaked up this protein, the tubercle’s cells stopped dying and carried on growing. So, it’s entirely possible for a chicken to grow a penis; it’s just that Bmp4 stops this from happening. Conversely, adding extra Bmp protein to a duck tubercle could stop it from growing into its full spiralling glory, forever fixing it as a chicken-esque stub.

Bmp proteins help to control the shape and size of many body parts. They’re behind the loss of wings in soldier ants and teeth of birds. Meanwhile, bats blocked these proteins to expand the membranes between their fingers and evolve wings.

They also affect the genitals of many animals. In ducks and geese, they create the urethra, a groove in the penis that sperm travels down (“If you think about it, that’s like having your urethra melt your penis,” says Kelly.) In mice, getting rid of the proteins that keep Bmp in check leads to tiny penises. Conversely, getting rid of the Bmp proteins leads to a grossly enlarged (and almost tumour-like) penis.

Penises have been lost several times in the evolution of birds. Cohn’s team have only compared two groups—the penis-less galliforms (chickens, quails and pheasants) and the penis-equipped anseriforms (swans, ducks and geese). What about the oldest group of birds—the ratites, like ostriches or emus? All of them have penises except for the kiwis, which lost theirs. And what about the largest bird group, the neoaves, which includes the vast majority of bird species? All of them are penis-less.

Maybe, all of these groups lost their penis in different ways. To find out, Herrera is now looking at how genitals develop in the neoaves. Other teams will no doubt follow suit. “The study will now allow us to more deeply explore other instances of penis loss and reduction in birds, to see whether there is more than one way to lose a penis,” says Patricia Brennan from the University of Massachussetts in Amherst.

And in at least one case, what was lost might have been regained. The cracids—an group of obscure South American galliforms—have penises unlike their chicken relatives. It might have been easy for them to re-evolve these body parts, since the galliforms still have all the genetic machinery for making a penis.

We now know how chickens lost their penises, but we don’t know why a male animal that needs to put sperm inside a female would lose the organ that makes this possible. Cohn’s study hints at one possibility—it could just be a side effect of other bodily changes. Bmp4 and other related proteins are involved in the evolution of many bird body parts, including the transition from scales to feathers, the loss of teeth, and variations in beak size. Perhaps one of these transformations changed the way Bmp4 is used in the genitals and led to shrinking penises.

There are many other possible explanations. Maybe a penis-less bird finds it easier to fly, runs a smaller risk of passing on sexually-transmitted infections, or is better at avoiding predators because he mates more quickly. Females might even be responsible. Male ducks often force themselves upon their females but birds without an obvious phallus can’t do that. They need the female’s cooperation in order to mate. So perhaps females started preferring males with smaller penises, so that they could exert more choice over whom fathered their chicks. Combinations of these explanations may be right, and different answers may apply to different groups.

Thanks to Dr. Lutter for bringing this to the It’s Interesting community.

http://www.oddly-even.com/2013/06/06/how-chickens-lost-their-penises-and-ducks-kept-theirs_/

http://news.yahoo.com/why-did-chicken-lose-penis-165408163.html

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Handout of an Adelie penguin carrying a video camera on its back stands in Langhovde
An Adelie penguin carrying a video camera on its back stands in Langhovde, Antarctica January 7, 2012, in this handout photo released by Japan’s National Institute of Polar Research’s Assistant Professor Yuuki Watanabe on January 23, 2013. REUTERS/Yuuki Watanabe/National Institute of Polar Research/Handout

Fish of the Antarctic, be very afraid. There’s an unlikely stealth predator on the loose – Adelie penguins.

Forget their ungainly waddling on land or comical bobbing at the ocean’s surface. As soon as these penguins dive into the icy Antarctic ocean, they become calculating, efficient killing machines, say Japanese researchers.

“You could say the penguins have an amazing stealth mode,” said Yuuki Watanabe, a researcher at Japan’s National Institute of Polar Research. “They’re great at sneaking up on their prey and taking them unaware.”

Watanabe this week released footage recorded in December 2010 showing a bird’s eye view of a hunt for fish and small crustaceans called krill, captured using a small video camera strapped to the backs of more than a dozen penguins.

“The krill wiggle their bodies about, they clearly make an attempt to swim off at full speed and escape,” Watanabe said of his findings, published in the U.S.-based Proceedings of the National Academy of Sciences this week.

“But that doesn’t make the slightest difference to the penguins. They just gobble up the krill that are trying to get away and swallow them whole.”

Using the “penguin cams,” which were set to automatically switch on when a penguin entered the water and shoot for 90 minutes, Watanabe and his team were able to capture the secrets of penguins on the hunt.

Additional information came from two accelerometers strapped to each bird that measured its head and body movements to calculate how fast it devoured its prey.

“We didn’t really know if the penguins caught krill one-by-one. I’d thought that maybe they just got into their stomachs when they were after some other prey,” Watanabe said. “But when we saw the footage it turned out the penguins were doing just that, eating these tiny little creatures one after the other.”

Not only that, the penguins didn’t swim randomly but hung poised on the edge of the ice until a thick swarm neared, then swooped into the water. Footage showed a penguin zooming under the ice and then deeper, its head snapping rapidly up as it fed.

The krill killing-rate was both fast and efficient. The penguins gobbled an average of two krill per second when the krill were clustered in swarms, a much faster rate than under general hunting conditions when the penguins consumed about 244 krill in roughly 90 minutes.

“I was so happy when I got the footage of a penguin going straight into a swarm of krill and gorging itself,” Watanabe said.

Penguin research completed, Watanabe now aims to repeat the same exercise with sharks.

http://www.newsdaily.com/stories/bre90n04i-us-japan-penguins-stealth/

 

Paleontologists working at Argentina’s Natural Sciences Museum of La Plata province found the fossil remains of an ancient penguin taller than most men. The bird stood six and half feet tall, and lived roughly 34 million years ago. The team’s lead researcher, Marcelo Reguero said the newly discovered species will “allow for a more intensive and complex study of the ancestors of modern penguins.”

“This is the largest penguin known to date in terms of height and body mass,” said team member Carolina Acosta. She also noted that the modern emperor penguin, which grows to about 4 feet tall had been the previous record holder.

The fossil was located on the icy continent of Antarctica; the team plans to return during the region’s summer to attempt to uncover more fossils from the ancient bird as well as study how it would have moved. Notably, past studies of other prehistoric penguins suggested that they were not black and white like the bird of today, but instead sported reddish brown and gray plumage.

http://www.examiner.com/article/6-5-foot-tall-prehistoric-penguin-fossil-uncovered-antarctica