Chickens: Half-Cock, Half-Hen

The medical term is gynandromorphism and about one in every 10,000 chickens suffers from it. The chicks hatch out half-cock and half-hen - literally one half (right or left) is one sex while the other side is the opposite sex.

Researchers now claim they have solved this mystery. As the photo below shows, if you are looking casually at a group of them (or even just one) you may not notice the differences if you are not looking at them straight on.

Three half-and-half chickens.

Now, look at the photo below. The differences in the right and left sides of the chicken are not trick photography - this chicken really is much more developed on the left or white side of the bird than on the right or brown side. This is because the cells on left side are all male; while the cells on the left side are all female.

The left, white, side of this bird is male. The right, brown, side is female.

Half-and-half chickens give a unique insight into how birds; and, perhaps reptiles develop. It used to be thought that hormones instructed cells to develop in either male- or female-specific ways.

That's what happens in mammals, including humans and it's what causes the secondary sexual characteristics like facial hair for men or breasts for women.

But scientists at the Roslin Institute and the University of Edinburgh say they now know that bird cells are not programmed by hormones; but, rather are inherently male or female remaining true to their sexual designation even when mixed-up in the same chicken.

It means a half-and-half chicken will have different plumage, body shape, muscle structure, wattle structures and even leg spurs on the two halves of its body.

Dr. Michael Clinton of the Roslin Institute led the research.

Dr. Michael Clinton of the Roslin Institute, leader of the research, has published his findings in the scientific journal Nature.

He said the findings were a surprise.

Dr. Clinton explained: "We looked at these birds initially expecting them not to be half-male and half-female. We thought there'd be a mutation on one side of the body. But we found that they were half-male and half-female and that's what actually showed us that the system was different in birds and mammals."

"If you put female cells into a male body they'll develop into the normal tissues, but they'll behave as female cells," Dr. Clinton said.

Researchers hope that this knowledge will help them in the poultry industry.

Dr. Clinton said: "If we can understand what the differences between the male and female identities are, then we can imagine making female birds with the same growth characteristics as males. That would increase productivity and food security." (Why does the word "Frankenfood" come to mind?)

Via BBC News