On the other hand, Stercorarius typically have very narrow, or much less expanded, pigmented nodes, and these nodes are visible throughout the entire length of the barbule
(as opposed to mainly at the proximal portion, as in Larus).
The formation of the extended cavities in the medulla of rami derives from the degeneration of the central group of barb cells (medullary) that instead of accumulate the resistant feather keratin like the other barb cells (cortical) and barbule
cells undergo a process of vacuolization (Matulionis, 1970; Alibardi, 2005a).
Barbs and barbules
were sturdy and intact, color patterns were present, and feathers were durable and comparable to modern-day specimens.
For that, they examined the fossilized barbules
- tiny, rib-like appendages that overlap and interlock like zippers to give a feather rigidity and strength.
A separate, striking amber specimen shows a birdlike feather branching into secondary twigs, or barbules
, with hook-lets like those in modern bird feathers that zip together side-by-side barbules
to make a tight, interlocked surface.
The bluebird's blue is called a "structural color," caused when light is scattered and reflected by tiny structures within each feather's myriad microscopic barbules
. In the bluebird's case, the feathers reflect short-wavelength blue light, creating the lovely hue that inspired Thoreau to say bluebirds carry the sky on their backs.
Ages later I let out that breath and the bird was still working, his dagger beak zipping up barbules
, oiling his sheen, completely unperturbed by us watchers or the noisy baptism.
15E), relatively short labium, widely darkened base and apex of the antennal segment II, subhyaline but always spotted hemelytron, ventral longitudinal keel on the male genital segment, barbules
on apical spine of the endosoma, 9-10 notches subtending the secondary gonopore (Fig.
Structural origin of the brown color of barbules
in male peacock tail feathers.
Perianth bristles 6, some of them longer than the achene, reddish or stramineous at the base, curved, finely and irregularly ciliatebarbate, the barbules
divergent to slightly ascendant on the upper part of the bristle and slightly retrorse at the lower part.
Cell structure of developing barbs and barbules
in down feathers of the chick: Central role of barb ridge morphogenesis for the evolution of feathers.