|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
|
Fig. 6. Examples of melanin pigment patterns produced by experimental manipulation
(A–D) and computer simulation (E,F). (A,B) Ornamental feather from the
neck region of a male Brown Leghorn chicken receiving 1.5 mg of a subcutaneous
injection of thyroxin every sixth day during growth of the feather
(Lillie, 1932) (A); (B)
control feather from the same region. (C,D) Normal feather from the wing
covert of a short eared owl (C), and (D) a feather from the same covert
induced to grow after removal of the thyroid gland [from Voitkevich
(Voitkevich, 1966), p.183].
(E,F) Two patterns produced in computer simulations of diffusion and
interactions between two molecules (`activator' and `inhibitor') on a growing
feather (Prum and Williamson,
2002). The activator stimulates production of both activator and
inhibitor. Inhibitor diffuses faster than, and inhibits, activator. Dark areas
are locations where the activator is above a certain concentration. One
important difference between the two simulations is that the diffusion rate of
inhibitor is higher when the longitudinal patch is produced. Both these
patterns are commonly observed across feather tracts of different species of
birds (Prum and Williamson,
2002).
|
