Half-Male, Half-Female Fowl Explain Birds' Sex Determination

Kanan excerpts from a BBC report out of Scotland: "A study of sexually scrambled chickens suggests that sex in birds is determined in a radically different way from that in mammals. Researchers studied three chickens that appeared to be literally half-male and half-female, and found that nearly every cell in their bodies — from wattle to toe — has an inherent sex identity. This cell-by-cell sex orientation contrasts sharply with the situation in mammals, in which organism-wide sex identity is established through hormones." Kanan also supplies this link to some pictures of the mixed-cell birds.

Comments

Interesting

[interkin3tic]

So would one of these hermaphrodite chickens be called a half-cock?

I agree with the section "Clucking confusing."

Re:Interesting

[RCGodward]

I think this story is for the birds... I'm sorry...

Re:Interesting

[c 0xFF]

If two sexually scrambled chickens get together, will one lay scrambled eggs?

Re:Interesting

[ArcherB]

Since this seems to be the "joke" thread, allow me to put in my $0.02

I was on a farm doing research on genetic engineering and kept seeing something zip around at amazing speeds. I asked the farmer what it was and he told me it was chickens.

"See," he said, "the drumstick is everyone's favorite part of the chicken. So we engineered chickens with three legs. For every two chickens we sell, it's like we are selling three, leg-wise. It actually reduces waste since the factories don't find themselves with extra breasts and other crappy parts that they have to throw away or turn into chicken nuggets."

I said, "WOW!!!! That's amazing. How do they taste?"

He replied, "Hell if I know. We haven't been able to catch one yet!"

________________________________________________________

Please, tip your waitress.

Re:Interesting

[icebike]

Also, when a flock of chickens suddenly loses it's rooster, the dominant female will sometimes act as a rooster. That isn't hormonal?

This does happen.

Apparently this is not all that common, that is, not every hen can become a henry, and perhaps TFA suggests the means by which this does happen when it does.

Apparently One in 10,000 hens can change sex, usually in response to a gonad ceasing to function. One professor explained it this way:

  "Yes a type of sex reversal does occur in poultry. Both a right and left ovary start to develop in the embryo but between day 7 and 9 of incubation the right gonad ceases to continue development. If in the adult, the left ovary is removed or fails to function the right gonad hypertrophies to become a testis-organ and thus "a male' instead of what was a hen."

The implication of this is with regard to TFA is that failure of one gonad cease development leads to the double expression of traits documented in the story.

So there is nothing new here that hasn't been known for some time with regard to chicken sex other than that the normal failure to enter stasis can lead to odd birds.

Re:Interesting

[dov_0]

Sex (noun) and gender are two distinct things.

Well, no. Sex and gender identification are two different things.

Have you ever noticed that in same-sex pairings, it is common for one member to act very masculine, and the other act very feminine, regardless of what the pair's actual sex is?

Sometimes, yes, sometimes no. What you are speaking about is quite irrelevant to the discussion and has less to do with gender identification than emotional roles in relationships, which is an entirely different thing.

Re:Interesting

[Darinbob]

What's new is that the DNA of the chicken is different on the left and right sides. It's not just developing new sexual characteristics due to hormones. If you take one of these hens that later became a rooster and checked the DNA, it would show up as female on both sides.

About one in every 10,000 chickens is gynandromorp

[kimvette]

About one in every 10,000 chickens is gynandromorphous, to use the technical term.

That's somewhat close to the rate of intersex conditions in mammals, including humans.

Object-sex-oriented?

[InsertWittyNameHere]

So each cell has it's own this.getSexualOrientation() function.

Whereas mammals have a global static variable where SEXUAL_ORIENTATION = MALE or FEMALE.

This is interesting because I thought we all inherited from a common ancestor. Was sexual orientation not defined in the root class?

Re:Object-sex-oriented?

[Anonymous Coward]

Sex is what you have between your legs.
Gender identity is what you want between you legs.
Sexual orientation is what you want between someone elses legs.

Re:Object-sex-oriented?

[danlip]

No, the common ancestor of all animals almost certainly reproduced asexually (as do many primitive animals today), so it would not be defined by the root class. There are of course more recent common ancestors between birds and mammals, but XY seems unique to mammals.
See ZW sex-determination system and X0 sex-determination system.

Re:Object-sex-oriented?

[FlyingBishop]

In both cases, each cell has its own this.getGender() function.

In both cases, I would imagine the code looks something like this:

class cell {
      int gender; // should really be a bool, need to fix that at some point.
      proteinFactoryBuilder asdf; // find a better naming scheme ... ...

      getGender() { /* I don't really have time to go back and fix this right now, but if I'd known I'd be making multicellular organisms with this shit I wouldn't have put this at the cellular level. Anyway, we're stuck with it, so for now I'm just returning the gender variable and I'll leave it to callers to figure out wtf to do with unexpected output. */
          return gender;
      }
}

Small wonder it's a little more confusing for birds.

Re:Object-sex-oriented?

[reverseengineer]

Mammals actually handle sex inheritance in an inverted arrangement from birds. Whereas mammals use the X/Y system, where males are the heterogametic type (XY) and females are the homogametic type (XX), birds (and some other animals) use a "ZW system" where males are ZZ and females are ZW. A notable feature of ZW determination is that the Z chromosome is more like a full-fledged chromosome with many genes, unlike the mammalian Y chromosome which has been paring down its genes so that it contains the sex-determining gene SRY, some genes necessary for sperm production, and little else.

This might go a long way towards explaining gynandromorphism in birds. In mammals, maleness is handled in a top-down fashion- the Y chromosome does not explicitly specify most aspects of the male phenotype, instead simply encouraging the cells that go on to make androgens, which then go on to produce a cascade of developmental effects throughout the body. In birds, the Z and W chromosomes both may have enough genes that sex determination can be handled from the bottom up, locally in each cell.

Re:Object-sex-oriented?

[GodfatherofSoul]

First-year computer science students rejoice! God doesn't know how to do OOD either!

Re:Object-sex-oriented?

[Chris Burke]

Don't be silly.

Sex is what you want but can never get enough of.

Gender identity is what lets you pick out cross-dressers and transvestites.

Sexual orientation is how you're oriented during sex, i.e. missionary, doggy style, reverse cowgirl, Saskatchewan Swinging Simian power retrograde style, etc.

Re:Object-sex-oriented?

[MikeV]

...unlike the mammalian Y chromosome which has been paring down its genes so that it contains the sex-determining gene SRY, some genes necessary for sperm production, and little else. ...This might go a long way towards explaining gynandromorphism in birds. In mammals, maleness is handled in a top-down fashion- the Y chromosome does not explicitly specify most aspects of the male phenotype, instead simply encouraging the cells that go on to make androgens, which then go on to produce a cascade of developmental effects throughout the body.

Even so, with the XY chromosome - cutting off body parts and taking hormones does not make a man a "woman" any more than flapping one's arms makes one a bird. Mammals sex inheritance isn't as neutered as the interpretation of the article suggests - only that fowls goes a bit deeper into it than mammals.

Re:Object-sex-oriented?

[Hurricane78]

So each cell has it's own this.getSexualOrientation() function.

That’s Java right? Then, wouldn’t that be this.getFactoryFactory().getOrientationDeterminationFactory(this.getFactoryFactory().OrientationDeterminator.SEXUAL).getSexualOrientationDeterminator().execute()?

Re:Object-sex-oriented?

[dimeglio]

Sexual intercourse is what you have been genetically programmed to do with what you have between your legs.

Re:Object-sex-oriented?

[dwye]

Your example code is cute, except that the inheritance system is more like Common LISP (inheritance from an instance) rather than C++ (inheritance from a Platonic Ideal of the class). Please rewrite appropriately.

Re:Object-sex-oriented?

[danlip]

that was meant to be a wikipedia link, something weird happened when I did a preview, edited again, and submitted (I had missed a closing quote before the first preview, but I think that caused slashdot to munge the URL, but I was going quickly). In any case you can search on that in wikipedia.

My point is there are lots of ways to do sex determination. Echidnas and Platypuses are particular weird in this way (and in every other way), even though they are mammal they don't use XY.

And of course, in the most literal real world sense, it is all inherited from instances.

n00bs

[DriedClexler]

They're not the first ones to be checking out a nice-lookin' bird and then see from another angle that "she" is really a man.

silly

[ascari]

It's well known that birds have a completely different sex determination mechanism than mammals. For example, mammals (other than the platypus) use X/Y or X/0 chromosomes to determine sex. Birds on the other hand use Z/W chromosomes for sex determination, as do most fish, some insects and some reptiles. So the big eyed "Ooooh, who would've thunk that birds aren't handling it the way we mammals do?" attitude of the article seems kind of silly considering we've known about this striking difference for a long time. Imagine that it actually mattered... Suspect they just wanted a reason to publish those cool pictures.

Re:silly

[Chris Burke]

Birds on the other hand use Z/W chromosomes for sex determination, as do most fish, some insects and some reptiles. So the big eyed "Ooooh, who would've thunk that birds aren't handling it the way we mammals do?" attitude of the article seems kind of silly considering we've known about this striking difference for a long time.

Okay, but knowing that the nature of the sex chromosomes is different isn't the same as knowing that the overall mechanism by which the sex of the organisms is determined is different. The assumption was that it was still essentially the same -- sex chromosome in the egg cell ends up controlling the formation of male or female gonads, which then release male or female hormones, which then control the sexual characteristics of the organism as a whole. And this is pretty reasonable on its face, since chickens do develop male/female gonads which do release sex hormones. It's largely the same, right up to the point where those hormones are what determine sex for every cell or not.

In mammals that's the case. Every cell in your body could be carrying X/Y chromosomes, but if due to some disorder you aren't producing male hormones but instead female ones, you will acquire female secondary sexual characteristics.

Now we know this isn't the case for birds, that every cell has its own sexual identity independent of hormones, and no we have not known about this striking difference until now.

Re:silly

[Chris Burke]

why should we assume that the implementation on the organism level would be identical? Isn't it more intuitive that there would be differences? But finding the "unexpected" makes for a better article than finding the expected...

Nobody ever thought they'd be identical, and of course there will be differences. That's not the same as expecting it to be completely opposite.

Expecting some kind of difference is not the same as expecting this difference. This difference was unexpected.

You can't say that because a difference of some kind is to be expected, that therefore whatever difference actually shows up was also expected. That's what strikes me as silly.

Hurray!

[clone53421]

Now we can produce twice as many chicken breasts.

I suppose we’d better not be going off half-cocked, though. More grant money!

Re:Changing Sex

[clone53421]

No... I’m thinking those species would have sexes which were entirely hormone-driven.

That’s basically the exact opposite of the chickens, in which sexes apparently have very little to do with hormones, and are entirely based on the genetics of the cells.

Humans would be somewhere in between. A man will grow breasts if you give him enough hormones, but you’ll have to do something surgically to change the penis...

Re:What took so long?

[Chris Burke]

Seriously. What I'm inferring from the article is that you can see the difference in the cells, e.g. male vs. female....

Yeah you can see that their sex chromosomes are different.

So how the hell have they never noticed that female and male birds have these slightly different cells before, and reached the non-hormone driven conclusion before this?

Because to notice this you have to specifically study the birds who have cells that are mixed between male and female, and then notice that the sexual characteristics vary over the same organism in accordance with which cells are male and which female.

Otherwise, you're just observing that a chicken is genetically male or female, and has male or female traits. That doesn't distinguish between a per-cell sexual determination, and mammals' overall hormone-based one.

Dinosaur extinction

[billstewart]

Are you suggesting that the Gay Agenda was what wiped out the dinosaurs?

I suspect the real events that affected their reproduction involved Mass Quantities of Death, and the difficulty in getting Zombie Dinosaurs to reproduce.