Cytological differentiation in the uropygial gland.

Ultrastructural changes were studied in the cells undergoing secretory differentiation in zone I of the tubules of the uropygial gland of White Plymouth Rock chickens. A layer of basal cells and four secretory stages are recognized as the cells migrate from the periphery to the lumen of tubules and progressively elaborate a secretion product. Basal cells, containing rough endoplasmic reticulum and free ribosomes, rest on the basement membrane and are the source from which secretory cells arise. Dilated perinuclear cisternae and the proliferation of smooth endoplasmic reticulum in the form of vesicles, invaginated sacs and cusp-shaped cisternae indicate the onset of lipgenesis in stage I cells. The perinuclear cisternae are more dilated and the endoplasmic reticulum is composed on saccules and cisternae in stage II cells. Stage III cells are characterized by concentric lamellae of endoplasmic reticulum surrounding secretory droplets. Dilated cisternae of endoplasmic reticulum and secretory droplets both contain a reticular substance. The perinuclear cisternae of stage III cells have returned to normal dimensions. Large mature lucent secretory droplets, lined with electron-dense material, fill the cytoplasm ostage IV cells which degenerate and release their secretory product into the tubule lumen. Spherical membrane-bound compartments containing a mottled substance of moderate electron density occur in basal cells and all subsequent secretory stages. These mottled bodies are surrounded by saccules of endoplasmic reticulum in stage II cells and are intimately associated with secretory droplets in stage III cells, but there is no evidence that they give rise to secretory droplets and their role in secretory differentiation is unknown.     

Chemical composition of uropygial gland secretions of owls

The compositions of the uropygial gland secretions of the long-eared owl, eagle owl, and barn owl have been determined. The waxes of the first two owls, which are closely related, are composed of 2-alkyl-substituted fatty acids and n- or monomethyl-branched alcohols with even-numbered branching positions. In addition, some dimethyl-substituted alkanols were observed. In contrast to these waxes, the secretion of the barn owl is composed of 3-methyl- and 3,5-, 3,7-, 3,9-, 3,11-, 3,13-, and 3,15-dimethyl-branched fatty acids and n- as well as monomethyl-substituted alkanols branched at positions 2, 3, and 4. The mass spectra of esters of 2-alkyl-substituted fatty acids are discussed.     

Testosterone metabolism in the uropygial gland of the quail

The metabolism of testosterone in the uropygial gland of the quail principally results in the production of 17 alpha, 5 beta derivatives. Moreover, an unusually small amount of testosterone is converted to 5 alpha-dihydrotestosterone. These results question the role played by intracellular 5 alpha-reduction in the response of the gland to testosterone stimulation.     

Recessive inherited doubling of the chicken's uropygial gland papilla

A new mutation that causes doubling of the uropygial gland (oil gland) papilla is described, and data that demonstrate its inherited basis are presented. This condition, which has been given the name "double oil gland papilla," varies in its expression: some individuals show only an indention of the papilla tip, while others exhibit a complete cleavage of the papilla such that two completely separate papillae project from a single oil gland. The data presented show that a single autosomal recessive gene, dgp, is the main determinant of this trait, but that its expression may also be influenced by background genetic factors as well as sex. Males more frequently are of the extreme doubling expression while females more frequently express the milder indented phenotype. Approximately 4% of mutant females are classified as normal. A linkage test with the rose comb gene showed independent segregation.     

The chemical composition of uropygial gland secretions from ralliformes

The uropygial gland wax from rails contains ester waxes, triester waxes and triglycerides. The ester waxes are composed of mainly methyl-substituted fatty acids with predominantly n-alkanols. Methyl-branched alcohols are only found in minor amounts. The occurrence of 2,6,10- and 4,8,12-trimethyl-substituted acids can be used as chemotaxonomie markers. The triester waxes contain n-fatty acids, n-alkanols and alkyl-hydroxymalonic acids.     

Biochemical composition of secretions from uropygial glands of steamer-ducks

Study of the secretions of the uropygial glands of the four species of steamer-duck (Tachyeres) revealed significant interspecific differences in the biochemical composition of the lipids and constituent fatty acids and alcohols. A canonical analysis of the fatty acids from monoester waxes provided an estimate of interspecific biochemical differentiation, but sexual differences in biochemistry, great intraspecific variation, and a lack of information concerning homologies and polarities of biochemical structures prevent confident chemophylogenetic inferences for the present.     

The uropygial gland secretions of birds of the family sylviidae

The preen gland secretions from eight species of the genera Acrocephalus and Sylvia (Sylviidae, Passeriformes) mainly consist of monoester waxes. The fatty acids and alcohols are methyl-substituted at even numbered positions only. One of the methyl groups of the fatty acids is always located in the 2-position. Two patterns of methyl substitution are found for the alkanols: $\text{2-}\text{mono-}$, $\text{2,6-di-}$, and $\text{2,6,x-}\text{trimethyl}$ on the one hand, and 4-mono-, 4,8-di-, and 4,8,$\text{y-}\text{trimethyl}$ on the other. There is, however, no doubt in the uniformity of the family Sylviidae from the chemotaxonomical point of view; the waxes of the species investigated can be arranged in a gradual succession of substitution patterns. The monoester waxes of Sylviidae are similar to those found for the closely related family Turdidae.     

Action of estriol on the uropygial gland activity in pigeon

Administration of estriol (Sigma Chemical Co., U.S.A.) in the female young-adult pigeons at a dose of 50 micrograms/bird/day for 7 consecutive days caused atrophy of the uropygial gland, associated with increased cytopycnosis and drastic cell loss within the holocrine alveoli and reduction in the content of the glandular lipids. Probable mode of action of this steroid upon the uropygial gland has been suggested in the light of the recent data on its anti-estradiol property manifested in rat uterus.     

Ectoparasites, uropygial glands and hatching success in birds

The uropygial gland of birds secretes wax that is applied to the plumage, where the secretions are hypothesized to eliminate fungi and bacteria, thereby potentially providing important benefits in terms of plumage maintenance. We analyzed variation in size of the uropygial gland in 212 species of birds to determine the function and the ecological correlates of variation in gland size. Bird species with larger uropygial glands had more genera of chewing lice of the sub-order Amblycera, but not of the sub-order Ischnocera, and more feather mites. There was a fitness advantage associated with relatively large uropygial glands because such species had higher hatching success. These findings are consistent with the hypothesis that the uropygial gland functions to manage the community of microorganisms, and that certain taxa of chewing lice have diverged as a consequence of these defenses.     

Plumage brightness and uropygial gland secretions in barn swallows

The uropygial gland has been hypothesized to play a role in sexual signaling through a "make-up" function derived from the effects of secretions from the gland on the appearanee of the plumage and bare parts of the body. Here we show that plumage brightness of dorsal feathers of individual barn swallows Hirundo rustica was greater in mated than in unmated individuals. In addition, plumage brightness in creased with colony size. Furthermore, plumage bright ness was positively correlated with the amount of wax in the uropygial gland, negatively correlated with time of sampling of uropygial wax (perhaps because more wax is present early in the morning after an entire night of wax production without any preening), and negatively correlated with the number of chewing lice that degrade the plumage. Experimentally preventing barn swallows from access to the uropygial gland reduced plumage brightness, showing a causal link between secretions from the uropygial gland and plumage brightness. These findings provide evidence consistent with a role of uropygial secretions in signaling plumage brightness.     

Sources of variation in uropygial gland size in European birds

Defence mechanisms against parasites and pathogens are some of the most elaborate biological systems in animals. The oily secretion of the avian uropygial gland has been suggested to serve as a chemical defence against feather and eggshell bacteria. Yet, the traits associated with uropygial gland oil production are not well understood. We conducted a phylogenetic analysis comprising 132 European bird species aiming to test: (1) whether life‐history and ecological traits drive gland size evolution by potentially promoting microbial infestation and (2) how these traits affects change in the gland size throughout the annual cycle. We show that the size of the uropygial gland is dynamic (i.e. increasing from the nonbreeding to the breeding season, independent of sex). Furthermore, we found that the year‐round size of the gland was similar between sexes and was correlated with different ecological and life‐history traits promoting microbial infection throughout the annual cycle. During the breeding season, the total eggshell surface area in a clutch correlated significantly and positively with the gland size, suggesting the importance of oil in protecting eggs from microbes. Social species exhibited a larger gland size increase during the breeding season compared to nonsocials; a change that was also predicted by the total eggshell surface area. Aquatic, riparian and non‐migratory species had larger glands than terrestrials and migrants, respectively. The findings of the present study suggest that aquatic environments may promote the production of gland oil, through either the need of waterproofing the plumage and/or defending it against the intensified feather degradation in these moist conditions. Finally, we found a negative effect of the incubation period on uropygial gland size, which may suggest an energetic constraint imposed by other development‐connected costly activities. Our results show that the role of the uropygial gland dynamically varies during the annual cycle, potentially in response to seasonal variation in parasitic infection risk. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 543–563.