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Keratinization and lipogenesis in epidermal derivatives of the zebrafinch, taeniopygia guttata castanotis (aves, passeriformes, ploecidae) during embryonic development
Author(s) -
Alibardi Lorenzo
Publication year - 2002
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1090
Subject(s) - keratin , biology , feather , beak , epidermis (zoology) , anatomy , taeniopygia , microbiology and biotechnology , zebra finch , genetics , neuroscience , ecology , paleontology
Little is known of the lipid content of β‐keratin‐producing cells such as those of feathers, scutate scales, and beak. The sequence of epidermal layers in some apteria and in interfollicular epidermis in the zebrafinch embryo ( Taeniopygia guttata castanotis ) was studied. Also, the production of β‐keratin in natal down feathers and beak was ultrastructurally analyzed in embryos from 3–4 to 17–18 days postdeposition, before hatching. Two layers of periderm initially cover the embryo, but there are eventually 6–8 over the epidermis of the beak. In the beak and sheath cells of feathers, peridermal granules are numerous at 12–14 days postdeposition but they are less frequent in apteria. These granules swell and disappear during sheath or peridermal degeneration at 15–17 days postdeposition. A thin β‐keratin layer forms under the periderm among feather germs of pterylous areas but is discontinuous or disappears in apteria. In differentiating cells of barbs, barbules, and calamus cells of natal down, electron‐dense β‐keratin filaments form bundles oriented along the main axis of these cells. Cells of the pulp epidermis and collar, at the base of the follicle, contain lipids and bundles of α‐keratin filaments. Degenerating pulp cells show vacuolization and nuclear pycnosis. During β‐keratin packing, keratin bundles turn electron‐pale, perhaps due to the addition of lipids to produce the final, homogenous β‐keratin matrix. In contrast to the situation in feathers, in the cells of beak β‐keratin packets are irregularly oriented. In both feather and beak epidermal cells the Golgi apparatus and smooth endoplasmic reticulum produce vesicles containing lipid‐like material which is also found among forming β‐keratin. The contribution of lipids or lipoprotein to the initial aggregation of β‐keratin molecules is discussed. J. Morphol. 251:294–308, 2002. © 2002 Wiley‐Liss, Inc.