In this case we may note that this gene has lost all its power;
it evidences that the notion of dominance is not absolute but related:
it depends on the circumstances.
In the black European goldfinch, the depositing of an abundant black melanin,
is generally due to endocrine troubles concerning the hypophysis,
a very important gland, whose takes part not only in the melanization process
but also in the reproduction and the development phases.
A mutation could be at the origin of a black European goldfinch but that
has few probability because the greater part of mutations have as effect
to dilute or suppress a pigment rather than to extend or to remark it".
Reading the two hypotheses formulated by Maurice Pomarède on the two
different melanic European goldfinches, both with happened inhibition of
lipochrome, one of which in a partial mode (only on the head), the other one
in a full mode (on all the body), I have found an evident contradiction:
in the first case a mutation is assumed, in the second one an aberration
putting in argument the dominant factors, considered relative dominant
as function of the circumstances.
In order to better understand the matter, I have telephoned directly to
professor Marcel Rouelle, asking him clarifications about the affirmations
of Maurice Pomarède (published on his books) and his opinion about
the melanic European goldfinches of my friend Luigi.
We have had a long and pleasant telephone conversation and
him agreed with me on the fact that the two hypotheses made by
Maurice Pomaréde were in contradiction each other,
but as it said It is the exception that confirms the rule.
However, about the melanic European goldfinches of my friend Luigi,
Ruelle has found very interesting the fact that the melanism was already
visible at the birth time, with black dark skin and black featheriness,
he has also confirmed me that, in order to overcoming the more or less
techniques disquisitions, the only way from is made was to do
is to pair them each other and/or with their parents in order to verify the
possible mutation.
I would want to end this article with a consideration:
in our case the melanism is not appeared during the increase or during the molt
or in senile age, but it was already present and evidently manifest since
the birth time and therefore I would exclude the alimentary factor
(melanic aberration caused by metabolic troubles of alimentary origin).
Therefore, in the worse hypotheses, it remains the thesis of melanic aberration
due to endocrine troubles. In such case it could be assumed that such subjects
could have chronic endocrine troubles since the birth time,
than have been maintained in a constant mode both, during the development
and the mold phase.
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Foto 6 - Cardellino melanico pubblicato su "Uccelli" di Aprile 1992
Or, in the opposite case, the best hypotheses, it is a genetic mutation of
melanic type.
Probably the question could, perhaps, be solved next year, both analyzing the
pairing results of the parents and those of the melanic subjects pairing each other, with parents and with normal subjects.
In fact (if all will go for the best and my friend Luigi will have the luck
to have the subjects in a good health at the beginning of the next
breeding season) we are planning to still pairing the parents each other
(considering that all the three youngsters born this year were of melanic type,
we are curious to see if also those of the next year will be) and to pairing
the two siblings (male and female) each other to the aim to verify if such
melanism is hereditary, that is transmissible to the progeny.
We will also try to pair the young melanic male with one or more normal
females to the aim to verify, if the melanism is hereditary, if it is
of sex-linked factor, recessive factor or free dominant one.
Probably, we need some years of work and a lot of luck in order to
verify, without any doubts, if it is a soap bubble or, as I wish to
my fiend Luigi, it is a changed factor that can be transmitted to the progeny,
in such a case we could have, in the future, a new color mutation
in the domestic European goldfinch.
If anybody has already had experiences or results like ours, or
you want to carry contribution to the discussion to the aim to formulate
other possible hypotheses, or simply to express your own related opinion,
you can directly contact us via internet:
E-mail: angelo_fumagalli@yahoo.com
WEB site: http://carduelis.too.it/Carduelis
Thank you very much in advance for your attention and for your contribution that you
will carry to the discussion.
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