Hi Saud,
1 . About expresion of psitacine within one feather in turquoise birds: I think that the best way to verify is to look at feathers of creamino birds to avoid interactions with melanin. As far as I know the psitacine pigment is not present in patches within one feather.
2. About genetics of the hypothetical double layer of psitacine: the fact of turquoise, acqua and blue as being alleles of the same gen does not disturb me that much. There are many possibilities of regulation:
a) The gen coding for psitacine could in fact be a master gen regulating two others gens (one regulating the homogeneous layer and the other regulating the "restricted" layer). It does not mean that aqua or turquoise mutations depend on mutation of the regulated genes, but that the master gen would regulate one and/or the other depending of which allele is present. With this possibility I join your above statement.
b) Another possibility would be that the threshold of activation of metabolic pathways for one or another layer could be different ...
In fact genetics provide the theoretical basis for understanding reality.
Let's develop further the hypothesis of the double psitacine layer (trying to approach the reality):
1 . About the
homogeneous layer: it should have been the first to appear, providing the birds of a great selectiv advantage as they would appear green. This should be a
very stable layer since it would be related to the chances of survival of birds in the wild. This layer would be present throughout the different species of parrots. I think this layer is very stable, I mean not "prone" to mutations.
2 . About the
restricted layer: to me this layer would be more
recent and has allowed different psitacula species to
evolve. This layer would not be as stable as the above one and more
prone to mutations: reasons:
a) Variation in surface area: turquoise expresion is very variable (20-80%) between strains or birds. In fact I think that instead of defining turquoise by its action (patched psitacine in the restristed areas) it should be defined by its "non action": never colouring flight feathers of wings and tail. In this sens it is to remark that lutino flight feathers are light yellow, exactly like acquaino flight feathers. From a mathematical point of view we could say:
lutino phenotype = creamino phenotype + aquaino phenotype.
b) Variation in intensity of colouring and in psitacine type:
b.1 : Males reaching maturity show a brighter green colouring in the restricted areas (head and wings), or a deeper yellow in lutinos, when compared to youngs or females. If the hypothesis is true we should not find these features in aqua or aquaino males. Does anybody have pictures of these birds to compare?
b.2 : Males reaching maturity display a black-red ring. Red colouring depends on psitacine production, and thus, we can asume that it is controlled by the same system than the restricted area. Far more, intensity of the restricted area (as stated above) and ring developement are both
depending on sexual hormones. So, birds not displaying the restricted area (aqua and aquaino) should not show any red colour in the ring, and birds not displaying the homogeneous layer (turquoise and creamino) should display the red coloured ring. I have just look in
http://home.wanadoo.nl/psittaculaworld/ ... rameri.htm and ... IT IS TRUE. THEORY WORKS !!!!
So, we could conclude saying that the homogeneous layer would be quite stable throughout the time and the species (in fact the evolution) and that the "restricted" layer would be more "prone" to mutations, facilitating speciation, and would be regulated by sexual hormones.
![Idea :idea:](./images/smilies/icon_idea.gif)
: If trying to obtain a red mutation breeders should work on turquoise mutation.
What do you think about the two layer hypothesis? Could it become a theory? Waiting for comments and data for and against the idea.
Cheers
Recio