Planet Earth

In which I set up a collaboration between a biologist, a farmer and a chimeric chicken

Not Exactly Rocket ScienceBy Ed YongSep 11, 2010 9:00 PM


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I get a lot of emails. Most can be casually filed away, but among the spam and fluff from PR agencies, there are occasionally some absolute gems. And so it was that on August 21^st, one Paul Sanders saw fit to send me four photos of a chicken. Several months back, I wrote a piece about chickens that caught Paul’s eye. In a new paper, Mike Clinton’s group at the University of Edinburgh had found that these everyday birds have an amazing secret - every single cell in their bodies is either male or female. Each one has its own sexual identity, which is very different from the way that sex is determined in mammals. You’ll have to read the original post for a full explanation of how this works, but the important bit is that Clinton’s discovery came about through studying three very unusual chickens called gynandromorphs. Each bird looks like it has been sown together from two different chickens down the midline; one half is clearly a cockerel and the other is clearly a hen. And that’s exactly what Paul Sanders found in his coop. Sanders grew up on a farm in rural Missouri. Aside from a stint in a law firm, a spell at university, and a tour in Vietnam, he has always kept chickens (no colonel jokes, please). He contacted me after reading my piece on chimeric chickens, and wanted to know if his bird fit the bill. He sent photos (above) and a video (below), where you can clearly see the different plumage and features on the right and left sides. The poor creature’s head feathers are missing in the photos because he/she was “nearly scalped” by some other chickens and needed stitches. [Update - the bird in the video is not Sanders' bird; it's a video he found from someone in New Zealand. Perhaps another collaboration! - Ed] Sanders asked whether the bird “should be donated to a university,” saying that “it would be a shame for him/her not to be shared.” I concurred. Clinton had contacted me after my original post and knowing that he was friendly and approachable, I suggested that Sanders contact him. Two nights ago, Sanders got back to me. Within days, Mike Clinton had replied to his email and the two men have enjoyed a productive exchange, which they were kind enough to share with me. It’s a wonderful series of messages that reveals a scientific collaboration in the making. It charts a conversation between two specialists – one in develomental biology and one in developing poultry - both trading knowledge, testing ideas, and speaking in simple language that the other less knowledgeable partner can understand (Clinton chuckled about this when I spoke to him). Clinton says that his first thought when he got Sanders's email was, "Hey another lucky break, you jammy beggar!" Many people had got in touch with him about the topic, "from schoolkids to retired scientists," and he even had a chat to a guy who had a collection of gynandromorph butterflies. But this was the first message he had recevied from someone who actually had an example of a chicken chimera. Clinton said that the bird is “almost certainly a gynandromorph.” He wrote to Sanders:

“We can be absolutely certain that your bird is not the result of any unusual treatment that the egg received… This condition occurs in a variety of different birds – chickens, zebra finches, cardinals and parrots have been reported (there are some very striking pictures on the internet). I suspect that it happens in all birds and possibly other species – but is only noticed in instances where the males and females are distinctly different (and in species where the body midline is established early in embryonic development). From a scientific point of view, the outstanding question to be resolved regarding gynandromorphs is “how do these birds arise”? There are currently two main theories; a) an unusual fertilisation event involving two different sperm, or b) the fusion of two separate embryos in a double-yolked egg. We strongly believe that gynandromorphs result from an unusual fertilisation event and that the two-embryo theory is extremely unlikely. Your observations on the size of the egg would suggest that it was unlikely to be double-yolked? If, in the future, material was available from the bird and the (prospective) parents, we may be able to resolve this issue using modern genotyping techniques.”

As it happens, that was something that Paul was very much up for:

“It is very exciting that this bird might help you to resolve the issue of how they occur. I still have the prospective parents and I could provide you with whatever genetic material you would need. In answer to your questions about the egg that it hatched from: it was not much larger than what is called a "fart" or "wind" egg in poultry keeper's terms. These tiny eggs generally have no yolk at all (though there are rare exceptions) as they result from some tissue within the oviduct that tricks the hen into thinking there is a yolk, and a shell forms around it. This was probably not the case here but it definitely had a single, not a double yolk. I had candled it a number of times and noted nothing unusual about it. Please feel free to ask any further question that might help you with your research. I am six hours behind you and I do not usually get to check my e-mail until after I feed my animals which is around noon time.”

A collaboration! But how to proceed? Clinton responded:

Thank you very much for your enthusiastic message – it’s gratifying to find others that share an interest in these unusual animals. We think that there are four possible mechanisms that could generate these birds:

There may well be others that are beyond the limits of my knowledge and imagination. Some of my colleagues here at Roslin are very interested in the details of avian genomes, and I think that if we apply their techniques we will be able to, at least partially, resolve this issue. They use an approach called genotyping – which essentially monitors genetic markers that vary between individuals. This is the sort of thing that you hear about on TV when celebrities have to undergo ‘paternity testing’ to prove (or not) that they are the father of the child involved. There are genotyping markers available for the chicken sex-chromosomes and if we applied them to material from these birds we should be able to show which mechanism is correct (and, of course, determine which of the male birds is the ‘father’). The only thing we would not be able to do is distinguish between mechanisms 2 and 3. I guess that if we are both interested in doing this, the big question is “how”? These procedures are normally carried out on material extracted from blood samples and if it is possible to get blood samples, I think that we should start there. I think that the only practical way to achieve this would be to get a “vet” to collect blood samples (in anticoagulant) and ship the samples to us by ‘Fed-Ex’. Of course, this would mean that you would not only have to be willing to permit blood samples to be taken – you would also have to go to the bother of organising it! I appreciate that this would be a tremendous nuisance for you and I would understand if your interest did not extend this far.

Uninterested? Not at all. Paul was in it to win it:

  1. A genetic defect early in oocyte (egg) development followed by fertilisation by one sperm.

  2. A genetic defect late in oocyte development followed by fertilisation by two sperm.

  3. The fusion of two normal embryos.

  4. The fusion of a normal oocyte and three sperm (from one or more males).

This is indeed very exciting. I took the time today to photo the mother and prospective fathers of the gynandromorph bird so that you can get an idea of all the birds that would be involved and have their photos "on record" if you wish. Please feel free to use them in any way you wish. It should not be too much trouble for me to coordinate the collecting of blood samples, which I am sure would need to be shipped immediately and overnight... I will be sending you updated photos of the gynandromorph bird soon. I am already seeing some changes to it that reflects male and female sides. Particularly the widening of the skull on the male side and heavy pin feather growth around the right side of the neck.

And now, data! What scientist could resist?

Thanks very much for the photographs – very impressive looking birds. It’s great that you will permit blood sampling and that you are willing to consider coordinating collection. My next step is to make sure that my budget will cover the costs of what we would like to do… I have spoken to some of my colleagues here and they were very positive and will get back to me with an estimate of what it is likely to cost for us to genotype these birds… I was very interested to hear about the changes occurring in the gynandromorph – these are such fascinating animals. Actually this is a real opportunity – there are no recorded examples of the changes that occur during the development from a young bird to an adult. If it isn’t too much of a hassle for you, it would be great if you could take pictures and notes of the changes and record when they occur.

And so it continues. I love this. Science can spring from the most serendipitous of circumstances and I’m proud to have played a trivial role as a conduit in this instance. Indeed, this story is laced with serendipity, right from its beginning. "This chimera was against incredible odds," says Sanders. "It all started when I found a tiny egg in the middle of the chicken house that somehow had managed to avoid getting trampled and broken. I picked it up and brought it to the house with the eggs I had gathered to eat, but this one proved to be too small to bother with. I was curious to see what kind of a chick might hatch out of it, so on a whim, I set it in the incubator... With such a small group of chicks that hatched, I was able to spot the odd coloring fairly early. This was the same day I contacted you!" How did Sanders find me? "My search brought up several related blogs and articles but yours was the only one that was easy to read yet contained enough technical information (and diagrams) to answer my questions," he says. "You also were the easiest to contact." I’ve written and spoken before about the power of blogs to connect people directly with scientists, and their ability to have a real impact in the non-pixellated world. I think this is a lovely case study of just such a connection, and just such an impact. Acknowledgments: I am indebted to Paul for sharing his story and providing photos and videos, and to both he and Mike for giving me permission to reprint their private emails. //

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