Symmetric feather loss
genecutl at mendel.berkeley.edu
Fri Jun 17 07:48:03 EST 1994
In article <1994Jun17.111816.1 at opal.tufts.edu>, skrishna at opal.tufts.edu
> I have recently observed a strange and wonderful phenomenon on my pet
> cockatiel. He is an unusual color mutation called a "pearl;" the mutation is
> sex-linked so when a male pearl molts (loses feathers) for the first time, he
> also changes color from pearl to plain grey (more or less). So I'm watching
> him change color. This process is heralded by appearance of grey blobs on his
> body where old feathers have fallen out and the new grey ones have come in.
> So, here's the cool thing: the grey patches -- even tiny ones on the
> head and the front of the wings -- appear _perfectly symmetrically_ down the
> body line. That is, when the bird loses a particular feather on its left wing,
> the same one will be lost and replaced at more or less the same time on its
> right wing. This must be accomplished by quite a feat of developmental
> regulation! I've watched a lot of pet birds molt before but only noticed the
> pattern of molting on this bird because of the color change.
> Of course, it makes evolutionary sense. The bird doesn't want to have
> all new feathers on one side and old, ratty ones on the other (or worse, be
> losing all the feathers on one side only), as that would impair its flight.
> But the genetic process culminating in the periodic, symmetric loss of feathers
> must be quite elaborate. Does anyone know of any research on this process?
> Thanks in advance for any ideas,
> Sanjay Krishnaswamy
> skrishna at opal.tufts.edu
I would say that this molting pattern was probably not selected
for but is only a consequence of selection for other things, that
being bilateral symmetry which goes back a lot further than parrots,
evolution-wise. Bilateral symmetry is established early on in
emryonic development. That's where the answer to your question
--g(actively being selected against)c
More information about the Bioforum