Carotenoides . Eumélanique Phaeomelanine

[Rosa moschata]

What can you share with us about sexual dimorphism?

Generally, there are two bases of sexual dimorphism in birds -- genetic and hormonal. An example of a genetic sexual dimorphism would be Eclectus parrots -- males are green, and females are red. This is apparent from the first feathers grown as nestlings. An example of hormonal sexual dimorphism would be trains in peafowl -- these grow in response to androgens produced by the bird, and birds that are genetically female can produce male plumage if their hormonal balances change, as often happens when they age. Similarly, castrated genetic males will not produce typical male plumage that is based on androgens. I faintly remember an old study that involved transplanting skin grafts between male and female chickens to determine which dimorphic traits were controlled by hormones (which would change when transplanted onto a chicken of the opposite sex, due to different hormones in the recipient) and which were genetic (which would remain the same when transplanted onto a chicken of the opposite sex). It's not necessarily an either-or thing by species -- it could also vary by particular feature. I think I remember that in the chicken study, some dimorphic traits were genetic and some hormonal, i.e. some of the transplanted grafts changed and others remained the same. But it's been a very long time since I read that, so my memory is a bit fuzzy.

 

[MinxFox]

Similarly, castrated genetic males will not produce typical male plumage that is based on androgens.

This is what happens to male lions. They will lose their luxurious mane.

 

[Rosa moschata]

Also, can you please, please tell me where to go to read about "no blue or green pigment in peafowl?" I have looked around online with little success. Where do I find this information?

Off the top of my head, I think only Turacos have green pigment -- virtually all other green feathers are the result of melanin (brownish-black) deposited deep within the feather structure, and the light reflecting back is refracted (i.e. "bent") toward the green wavelengths as it passes through. Same goes for most blue coloration. In species with yellow-red pigments (I don't think this includes peafowl), these colors are deposited closer to the surface of the feathers, functioning like tinted lenses. For example, green parrots have no green pigment. They appear green because their brownish-black pigment deep within the feathers gets refracted to blue wavelengths, which then pass through a sort of veneer of yellow pigments, thus appearing green. Mutations in green parrots that delete the melanin result in yellow parrots. Mutations that delete the yellow result in blue. Of course, there are subtle variations that reduce rather than eliminate either pigment, as well as redistribute their patterns of deposition, giving rise to the many colors you see in budgies (which are green with yellow faces in the wild).

See the Wikipedia page on structural coloration that explains it in greater detail.

 

[Garden Peas]

Generally, there are two bases of sexual dimorphism in birds -- genetic and hormonal. An example of a genetic sexual dimorphism would be Eclectus parrots -- males are green, and females are red. This is apparent from the first feathers grown as nestlings. An example of hormonal sexual dimorphism would be trains in peafowl -- these grow in response to androgens produced by the bird, and birds that are genetically female can produce male plumage if their hormonal balances change, as often happens when they age. Similarly, castrated genetic males will not produce typical male plumage that is based on androgens. I faintly remember an old study that involved transplanting skin grafts between male and female chickens to determine which dimorphic traits were controlled by hormones (which would change when transplanted onto a chicken of the opposite sex, due to different hormones in the recipient) and which were genetic (which would remain the same when transplanted onto a chicken of the opposite sex). It's not necessarily an either-or thing by species -- it could also vary by particular feature. I think I remember that in the chicken study, some dimorphic traits were genetic and some hormonal, i.e. some of the transplanted grafts changed and others remained the same. But it's been a very long time since I read that, so my memory is a bit fuzzy.

I think this is helpful for starting a discussion, thanks! But of course, then so many other questions

Turning specifically to peafowl, we see a variety of differences between the sexes. We have, of course, the lovely train, which you indicate is hormonally controlled. But then we have all these interesting variations in plumage coloration and pattern which are quite different between the sexes. Are those hormonal or genetic?

And if a peahen starts growing whiskers on her hind end... will her body plumage coloration change to male? Or remain somewhere in between? Is the coloration of adult IB hens and males (non-barred & barred) controlled by genetics or hormones? What about the green versus blue necks?

Why do blackshoulder peahens have rust-colored flight feathers, a feature normally found on IB males? Does that relate to a suppression of color? Are the corresponding flight feathers on an IB female actually rust, if you suppress the brown in them? (Interestingly, the rust-colored flight feathers on my IB hen are not completely rust-colored, but still have some darkness to them.)

Are our sex-linked color genes actually some form of genetic sexual dimorphism, or is that mixing apples and oranges?

Give me 10 minutes, I'll think of more questions

 

[Garden Peas]

I should also point out that when I went and looked at the BS hen again this morning, it's striking to notice that her back (which has fresh feathers) has greyish black speckles and lines where the shafts of the feathers lie, which if combined with brown, would probably look pretty much exactly like the color of an IB hen. It just seems to me that the various shades of brown have been "erased" from the BS hen, leaving gray, off white, and rust. There is some brown/rust on her neck and head, along with a few greenish neck feathers, and a couple truly white crest feathers and a white throat latch showing her split to white or pied. And a few white flights too.

 

[Garden Peas]

If you gave an IB BS hen male hormones for a year, what coloration would you see?

 

[Garden Peas]

Looked up photos of BS males, btw, and so far, the photos I found all have black (or dark in the photos) "pants" -- regular IB have tan pants the same color as the wing bars...

So it makes sense if the tan is getting supressed, what you have left is black...

It doesn't seem to me that BS is adding black to the bird, it looks like it is taking brown OUT of the bird.

 

[Jack07]

Merci, Jack, je vien de lire vos postes... tres informants!

Avez-vous finis poster sur cette sujet?

Aussi... je ne suis pas certaine si le couleur qu'on appelle "opal" dans les paons est ce le meme couleur dont on appelle opal dans les autres oiseaux.  Ce couleur est pas trop agee dans les paons, et je ne sais pas comment on a decide sur le nom...

Mon opal SP paon n'a que peu de plumes opal, puis il faut que j'irais les voir tout pres.  Mais mon impression n'est jamais que les plumes soient plus fonces au l'invers...   Je m'inquires si on n'a pas le nomme justement?  Vous avez des opals, n'est-ce pas?  Sont ils renverser comme vous ecrivez dans les postes?

J'aime bien ce que vous avez ecrit!  Merci beaucoup!  Moi aussi, je vais atteindre le baccalauriat degree 2eme

All -- Jacky has provided a link to a series of posts he wrote about color for the French forum, which has lovely diagrams of feather structure and a remarkably good explanation of formation of melanin. 

Thanks, Jacky!

La mutation opale affecte la structure de la plume , elle freine la formation du noir ( mélanine) qui est de plus enfoui dans la plume et concentré sous le canal médullaire
Elle est caractérisée par un effet optique bleu . D'où une couleur laiteuse avec des reflets bleus

Je vais poster 2 schémas pour expliquer

 

[Jack07]

 

[Jack07]

Non, @Dany12
, ça n'a pas raison.

Quand nous disons "liée au sexe", ça veut dire les gènes qui sont place sur les gènes du sexe.  On le voit en patterne heritage, la femmelle ne peut pas les transmettre au poussines.

La gène nigripenne doit etre passer par les deux parents pour que les poussin soient nigripennes, alor la gène ne lie pas sur la gène sexe.

Oui, c'est vrai que le paon s'enfonce, mais quand même la paonne nigripenne devient beaucoup plus claire... 

Ne melangez l'expression phenotype avec la question de genotype!  Tous les couleurs des paons s'expressent different dans les deux sexes!  Cela est le dimorphisme sexuel, ce n'est pas la meme chose que les genes liee au sexe.

Je ne sais d'ou vous avez trouvez cette photo, mais les couleurs ne me semble pas vrai.  Peut etre artifact de la lumière?

No, Dany, that is not correct.  When we say "sex-linked", that refers to genes which are located on the sex gene.  We see this expressed in the pattern of inheritance, the female cannot transmit the gene to female chicks.

The blackshoulder gene must be passed by both parents for the chick to be blackshoulder, therefore the gene does not lie on the sex gene.

Yes, it is true that the male darkens, but the black shoulder hen becomes much lighter in color.

Don't mix the phenotype expression with the question of genotype!  All the colors in peafowl express differently in the two sexes.  That is sexual dimorphism, which is not the same as sex-linked genes.

I don't know where you found this photo, but the colors do not seem to be correct.  Perhaps an artifact of the lighting?

100% d'accord avec Garden Peas il ne faut confondre liée aux sexé et dimorphisme sexuel.
La mutation Nigripenne (pennes noires) ou Blackshoulder (ailes noires) est récessive et libre !!!
Par contre alors que logiquement le "noir" viendrait de plus de mélanine dans les ailes en lieu et place de l'aile barrée !!! Au départ (poussin) est blanc c.est á dire absence de mélanine !!!
Y a t il une explication ??? J'aimerais comprendre