Chicken With Teeth


Have you ever seen a chicken with teeth? Well, if you haven’t it’s time to check out this animated short film that goes beyond the limits of animation. This project was produced for Maximum Fun which is a network of podcasts. The music required a lot of writing especially for this style because of its repetition but also because the pacing is so off from the song so it was fun to figure out how to make things move along and fit just right. I actually love making music videos because unlike commercials where you are given a song and have to figure out what fits with it, here you are given music and a story to work with which is really fun for me as an original music composer.

Mutant Chicken Grows Alligatorlike Teeth

Working late in the developmental biology lab one night, Matthew Harris of the University of Wisconsin noticed that the beak of a mutant chicken embryo he was examining had fallen off. Upon closer examination of the snubbed beak, he found tiny bumps and protuberances along its edge that looked like teeth–alligator teeth to be specific. The accidental discovery revealed that chickens retain the ability to grow teeth, even though birds lost this feature long ago. The finding also resurrected the controversial theory of one of the founders of comparative anatomy, Etienne Geoffroy Saint-Hillaire.

In the early 19th century, Saint-Hillaire observed that developing parrots have tiny bumps on their beaks that resemble teeth, something he ascribed to modern animals deriving from more basic primitive forms. But due to his developing battles with Georges Cuvier over evolution, the finding was forgotten until Harris, a graduate student, rediscovered it nearly 200 years later.

The mutant chickens Harris studied bear a recessive trait dubbed talpid2. This trait is lethal, meaning that such mutants are never born, but some incubate in eggs as long as 18 days. During that time, the same two tissues from which teeth develop in mammals come together in the jaw of the mutant embryo–and this leads to nascent teeth, a structure birds have lacked for at least 70 million years. “They don’t make a molar,” explains development biologist John Fallon, who oversaw Harris’s work. “What they make is this conical, saber-shaped structure that is clearly a tooth. The other animal that has a tooth like that is an alligator.”ADVERTISEMENT

Previous efforts to produce teeth in chickens had relied on introducing genetic information from mice, resulting in chickens growing mammalian molars. But a chicken’s underlying ability to grow teeth derives from a common ancestor with alligators–archosaurs–that is more recent than the one linking birds and mammals. Nevertheless, the underlying genetic mechanism that produces teeth in mice, alligators and mutant chickens remains the same.

Exactly how the mutation causes the chickens to sprout teeth is unknown, Fallon notes, but a similar effect can be produced in normal chickens. Harris proved this by engineering a virus to mimic the molecular signals of the mutation and caused normal chickens to briefly develop teeth that were then reabsorbed into the beak. The finding of such an atavism–presented in yesterday’s issue of Current Biology–opens a new avenue of exploration in the quest to understand how particular structures like teeth are lost in different evolutionary lineages. It also vindicates the long ago observations of one of the early fathers of comparative anatomy.

Surprise: Chickens Can Grow Teeth

Normal chick on the left, the talpid2 is on the right. The mutant jaw clearly shows teeth. (Image credit: John F. Fallon and Matthew P. Harris)

Chicken will grow teeth when pigs can fly.

Well, better start searching the skies for flying pork—scientists have discovered a mutant chicken with a full set of crocodile-like chompers.

The mutant chick, called Talpid, also had severe limb defects and died before hatching. It was discovered 50 years ago, but no one had ever examined its mouth until now.

The researchers recently created more Talpids by tweaking the genes of normal chickens to grow teeth.




“What we discovered were teeth similar to those of crocodiles—not surprising as birds are the closest living relatives of the reptile,” said Mark Ferguson of the University of Manchester.

What happened

Around 300 million years ago, the ancestor of all modern vertebrates gave rise to two lineages, the mammals and the reptiles/birds. The oldest reptiles, such as crocodiles and alligators, had cone-shaped teeth. So did the earliest birds, called archosaurs.

Then, around 80 million years ago, modern birds emerged without teeth.

“So what would you expect bird teeth to look like? You would expect them to have teeth like their ancestors and their most closely related living relative,” study co-author John Fallon of the University of Wisconsin told Live Science.

Indeed, Talpid’s teeth are conical, much like an archosaur’s and closely resembling the teeth of a baby alligator or crocodile, Fallon said. If the chick survived, the teeth would most likely reabsorb into the mouth.

The archosaurs had mouths similar in shape to a reptile’s. It turns out that developing a beak caused birds to lose their teeth.

“The reason that birds lost their teeth is that in forming a beak, the two tissues that ‘talk’ to each other to make a tooth become separated,” Fallon said. “They can’t have the conversation to make a tooth. In the mutant, these tissues are brought back together.”

Make more mutants

The finding made scientists curious whether healthy chickens still possessed the 80-million-year-old genetic pathway for producing teeth.

By making a few changes to the expression of certain molecules in the pathway, the researchers were able to induce tooth growth in normal developing chickens. These teeth also looked like reptilian teeth and shared many of the same genetic traits, supporting the scientists’ hypothesis. None of these chickens were allowed to hatch.

This is all good news for hockey players. A direct application of this research, Ferguson said, could be re-growing teeth in people who have lost them through accident or disease.

Mutant Chickens Grow Teeth

Reptilelike choppers may resemble those seen in early birds

Warning: Mutant chickens may bite. Researchers have identified a genetic mutation that creates incipient teeth in bird embryos. The discovery provides a modern day glimpse of a feature that hasn’t been seen in avians for millions of years.

Birds lost their choppers 70 million to 80 million years ago. That’s what made an experiment in 1980 so surprising: After scientists grafted oral tissue from mice onto a chicken’s gums, the birds grew round, mouselike teeth. But because avians and mammals are not closely related, scientists doubted whether the experiment proved that birds had truly retained a genetic vestige of their forbearers’ bite.

Now a group of developmental biologists has found a strain of birds that don’t need outside help to grow teeth. While investigating a gene mutation known to affect organ development in chickens, Matthew Harris of the Max Planck Institute in Tübingen, Germany, noticed sharp protrusions on the jaw of a 16-day-old embryo. Scientists had never suspected a connection between tooth formation and the gene–known as talpid2–because embryos with the mutation rarely survive past 12 days. Further investigation by Harris and colleague John Fallon at the University of Wisconsin, Madison, indicated that the teeth were conical and saber-shaped, resembling those of an alligator or crocodile.

To see how tooth formation in these chickens compares to that of other animals, the team looked at the expression pattern of a gene called sonic hedgehog (shh), which is essential for tooth production in vertebrates. In normal chicks, shh was expressed in a region analogous to the sides of the gums, but in alligators and talpid2 mutants, shh appeared in the center of the gums. The mutant version of talpid2 thus appears to turn shh on in the right place for growing teeth. Over time, changes in the gene may have disrupted this ability, resulting in tooth loss, the researchers report 21 February in Current Biology.

The finding is a great example of how altering the location of gene expression can cause changes in body types over time, says biologist Scott Gilbert of Swarthmore College near Philadelphia, Pennsylvania. “The real wow here,” adds Paul Sharpe, a biochemist at the Department of Craniofacial Development at Kings College London, “is that these guys essentially show a glimpse of what the teeth probably looked like in the first birds.”

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