The uropygial glands of birds are sebaceous organs that contribute to the water-repellent properties of the feather coat. We studied the histological and histochemical characteristics of the uropygial gland of chimango caracara using hematoxylin and eosin (H & E), Gomori´s trichrome, orcein, Gomori´s reticulin, periodic acid-Schiff (PAS), Alcian blue (AB) and a variety of lectins. The gland is composed of two lobes and a papilla with 20 downy feathers. It is surrounded by a capsule of dense connective tissue that contains elastic, reticular and smooth muscle fibers. The papilla is delicate and has two excretory ducts. The gland mass relative to body mass was 0.143%. Both adenomer cells and their secretions were stained with Sudan IV, PAS and AB, and were positive for numerous lectins that indicated the presence of lipids and carbohydrates. Immunohistochemical techniques to detect PCNA confirmed cell proliferation in the basal stratum of the adenomer cells. The lipids and glycoconjugates secreted by the uropygial gland serve numerous functions including protection against microorganisms.

The uropygial gland is morphologically different in diverse bird species. This gland was macroscopically and microscopically examined in penguins, storm petrels and skuas. In all the studied species, the gland showed a connective tissue capsule and one papilla. A negative relationship was observed between the relative glandular mass and the body mass, being highest in petrels (small glands) and lowest in penguins (large glands). Birds that spend much time in water (penguins) have gland characteristics related to a continuous, but not stored, secretion, such as straight adenomers, the presence of abundant elastic fibres in the connective tissue and the absence of a primary storage chamber. Instead, birds that have less contact with water (storm petrels) have a gland with much more tortuous adenomers and a small primary storage chamber. The secretory cells showed a positive PAS reaction in all the glandular zones. Therefore, no differences could be seen between the sebaceous and glucogenic zones, as proposed in other birds. These results allow the conclusion that, in aquatic birds, there is no connection between the relative mass of the uropygial gland and the time in contact with water, though the differences found in the histological structure could be related to a different contact with the aquatic environment.

Chiale, M.C., Montalti, D., Flamini, A. and Barbeito, C.G. 2017. The uropygial gland of the Southern Caracara (Caracara plancus; Falconidae: Falconinae): histological and histochemical aspects. -Acta Zoologica (Stockholm) 98: 245-251.

The uropygial (preen) gland is a holocrine organ unique of Aves. Although several studies have been performed on the uropygial gland of different bird species, knowledge about this gland in Columbiformes is scarce. In order to fill this gap, we analysed in detail the external morphology and the histological and histochemical features of the uropygial gland of the Eared Dove (Zenaida auriculata) in a comparative context. The uropygial gland of the Eared Dove is characterized by its pear-like shape composed of two lobes, conical and naked papilla, tubule-alveolar adenomers, a large primary storage chamber (a feature also present in other terrestrial avian species), and reticular and elastic fibres in the capsule and connective tissue surrounding the adenomers. The histochemistry showed a positive reaction to periodic acid-Schiff, Alcian Blue 2.5 and several lectins, evidencing the presence of diverse glycoconjugates in this organ. Since the uropygial gland may be independently present or absent within Columbiformes, we also used character mapping on a molecular phylogeny to infer the character states of this gland at ancestral nodes to understand its evolutionary history. The analysis shows that the presence of the uropygial gland is the ancestral state for Columbiformes and that its loss occurred more than once independently. Keywords Preen gland • Zenaida auriculata • Histology • Histochemistry • Lectin • Ancestral state reconstruction ZusammenfassungDie Bürzeldrüse der Ohrflecktaube (Zenaida auriculata) und ihre evolutionsbiologische Geschichte innerhalb der Taubenvögel Die Bürzeldrüse ist eine nur bei Vögeln vorkommende holokrine Drüse. Obwohl es einige Untersuchungen dieser Drüse bei unterschiedlichen Vogelarten gibt, wissen wir nicht viel über sie bei Tauben. Um diese Lücke zu schließen, analysierten wir vergleichend und im Detail die äußerlichen morphologischen sowie die histologischen und histochemischen Eigenschaften der Bürzeldrüse von Ohrflecktauben (Zenaida auriculata). Ihre Bürzeldrüse ist durch ihre Birnenform charakterisiert und setzt sich zusammen aus zwei Lappen, einer konischen und nackten Papille, tubulealveolaren Adenomen, einer großen primären Speicherkapsel (die es auch bei anderen Landvögeln gibt), retikulären und elastischen Fasern in der Kapsel und Bindegewebe um die Adenomen herum. Die Histochemie zeigte positive Reaktionen auf PAS, Alcian-Blau 2,5 und mehrere Lektine, was auf das Vorhandensein von diversen Glykokonjugaten in diesem Organ hinweist. Da die Bürzeldrüse bei Tauben unabhängig voneinander vorhanden sein oder fehlen kann, betrachteten wir ihr Vorhandensein innerhalb des molekularen Stammbaums der Tauben, um die evolutionsbiologische Geschichte der Drüse zu verstehen. Die Analyse zeigt, dass das Vorhandensein der Bürzeldrüse bei Tauben entwicklungsgeschichtlich der Normalfall war und sie mehr als einmal unabhängig voneinander verlorenging.Communicated by L. Fusani.

We describe the morphology, histology, and histochemical characteristics of the uropygial gland (UG) of the monk parakeet Myiopsitta monachus. The UG has a heart-shape external appearance and adenomers extensively branched with a convoluted path, covered by a stratified epithelium formed by different cellular strata and divided into three zones (based on the epithelial height and lumen width), a cylindrical papilla with an internal structure of delicate type and two excretory pores surrounded by a feather tuft. Histochemical and lectinhistochemical techniques performed showed positivity against PAS, AB pH 2.5, AB-PAS, and some lectines, likely related to the granivorous feeding habits.Also, we describe the morphogenesis of the UG of the monk parakeet, which appears at embryological stage 34 as a pair of ectodermal invaginations.Heterochronic events in the onset development of the UG when compared with other birds could be recognized. Finally, to examine the phylogenetic occurrence of the UG within the Psittaciformes and infer its evolutionary history, we mapped its presence/absence over a molecular phylogeny. The reconstruction of the characters states at ancestral nodes revealed that the presence of the UG was the plesiomorphic feature for Psittaciformes and its loss evolved independently more than once. K E Y W O R D Sancestral state reconstruction, evo-devo, heterochrony, histochemistry

Greater flamingos use cosmetic coloration by spreading uropygial secretions pigmented with carotenoids over their feathers, which makes the plumage redder.Because flamingos inhabit open environments that receive direct solar radiation during daytime, and carotenoids bleach when exposed to solar radiation, we expected that the plumage color would fade if there is no maintenance for cosmetic purposes.Here, we show that the concentrations of pigments inside feathers and on the surface of feathers were correlated, as well as that there was a correlation between the concentrations of pigments in the uropygial secretions and on the surface of feathers. There was fading in color (becoming less red) in feathers that received direct solar radiation when there was no plumage maintenance, but not so in others maintained in darkness. When we controlled for the initial color of feathers, the feathers of those individuals with higher concentration of pigments on the feather surfaces were those that lost less coloration after experimental exposure of feathers to sunny conditions. These results indicate that exposure to sunlight is correlated with the fading of feather color, which suggests that individuals need to regularly apply makeup to be more colorful. These results also reinforce the view that these birds use cosmetic coloration as a signal amplifier of plumage color. This may be important in species using highly variable habitats, such as wetlands, since the conditions experienced when molting may differ from those when the signal should be functional, usually months after molting.

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En Argentina, el Flamenco Austral (Phoenicopterus chilensis) se reproduce desde Santa Cruz hasta el extremo norte en la provincia de Jujuy. En el presente trabajo aportamos observaciones sobre nuevos registros de nidificación en las provincias de Buenos Aires y Santa Cruz. También proporcionamos datos de conteos realizados en ambas zonas y describimos posibles amenazas. Estos registros son de gran importancia ya que contribuyen al conocimiento del estatus del Flamenco Austral en la Argentina.