A macroanatomical and histological study of the uropygial gland in the white stork (Ciconia cicionia) / Un estudio macroanatómico e histológicos de la glándula uropigial de la cigüeña blanca (Ciconia cicionia)

The present study was aimed at the macroanatomical and histological investigation and the demonstration of the structural characteristics of the uropygial gland in the white stork. The uropygial gland of two adult male white storks constituted the material of the study. It was determined that the gland was situated subcutaneously in between the caudal aspect of the lumbosacral bone and the first coccygeal vertebrae. The gland was composed of two lobes, which displayed an oval appearance when viewed from above and resembled a water drop when observed medially. Tuft of feathers were present on the caudal margin of each lobe. The present study revealed that the uropygial gland of the white stork is a simple tubular gland, which discharges its secretion into the lumen by a holocrine mode. Each lobe, possessed centrally located large cavities and a main excretory duct and displayed the presence of externally situated "peripheral tubules" and interiorly situated "central tubules". These secretory tubules, which composed the parenchyma, were separated by connective tissue septa referred to as "trabeculae", and released their secretion into a centrally located lumen. The wall of the secretory tubules was comprised of four layers, referred to as the germinative, intermediary, secretory and degenerative layers. The silver-staining procedure demonstrated that the stroma of the uropygial gland did not contain reticulum fibres. The anatomy and histology of the gland has been examined in few avian species. Up to date, this study is the first to describe the histological and anatomical peculiarities of the uropygial gland in white stork. The results acquired hereby will surely contribute to further studies to be conducted on the related area.

El estudio tuvo como objetivo la investigación anatómica e histológica de la glándula uropigial de la cigüeña blanca, junto con demostrar las características estructurales de ella. El material del estudio estuvo constituido por glándula uropigial de dos cigüeñas blancas adultas macho. Se determinó que la glándula se encuentra vía subcutánea entre la parte caudal del hueso lumbosacro y las primeras vértebras coccígeas. La glándula se compone de dos lóbulos que muestran un aspecto ovalado, vista desde arriba y se asemejan a una gota de agua cuando se observa en sentido medial. Un penacho de plumas estaba presente en el margen caudal de cada lóbulo. El presente estudio reveló que la glándula uropigial de la cigüeña blanca es una glándula tubular simple, que descarga su secreción al lumen de un modo holocrino. Cada lóbulo posee una gran cavidad de ubicación céntrica y un conducto excretor principal, además muestra la presencia de "túbulos periféricos" situados exteriormente y "túbulos centrales "situados interiormente. Estos túbulos secretores que componen el parénquima, estaban separados por tabiques de tejido conectivo denominado "trabéculas", y liberan su secreción en una luz central. La pared de los túbulos secretores se componen de cuatro capas: germinativa, intermedia, secretora y degenerativa. La tinción de plata demostró que el estroma de la glándula uropigial no contienen fibras reticulares. La anatomía e histología de esta glándula se ha examinado en algunas especies de aves. Hasta la fecha, este es el primer estudio en describir las particularidades histológicas y anatómicas de la glándula uropigial de la cigüeña blanca. Los resultados obtenidos contribuirán a llevar a cabo nuevos estudios relacionados en el área.

Physiological and biochemical aspects of the avian uropygial gland / Aspectos fisiológicos e bioquímicos da glândula uropigial das aves

This review discusses different aspects of the uropygial gland of birds. The gland exhibits a striking morphological diversity in size, shape and presence/absence of tufts of feathers. It was shown that acidic mucins, neutral lipids, glycolipids and phospholipids are normal components of secretion. Several morphological and physiological aspects of the gland were studied on Rock Pigeon Columba livia Gmelin, 1879. The amount of the uropygial gland secretion, its lipid content and fatty acids profile were determined. The extracted lipid mixture contained of C14 to C20 fatty acids, mostly unsaturated; the saturated fatty acids were mainly 14:0, 16:0 and 18:0. No correlation was found between the size of the gland and the aquatic/terrestrial nature of the species. Ablation of the gland did not affect survival, body weight, feeding rate and serum cholesterol, total lipids or calcium levels after 32-120 days. The possible role of the gland in the protection against lipophilic compounds was discussed. The function of the gland is still a subject of controversy. It is accepted that its secretion confers water-repellent properties on the feather coat and maintain the suppleness of the feathers. Other physiological roles of the gland secretion may be associated to pheromone production, control of plumage hygiene, thermal insulation and defence against predators. Concerning the endocrine regulation of the uropygial function, there is scarce information presenting evidence for steroid regulated mechanisms.

Esta revisão discute diferentes aspectos da glândula uropigial das aves. A glândula exibe uma chamativa diversidade morfológica de tamanho, forma e presença/ausência de um tufo de penas. A glândula mostrou mucinas ácidas, lipídios neutros, glicolipídios e fosfolipídios como componentes normais de sua secreção. Diversos aspectos morfológicos e fisiológicos da glândula foram estudados na pomba doméstica Columba livia. Foi determinada a quantidade de secreção da glândula uropigial, seu conteúdo lipídico e o perfil de ácidos sebosos. A mistura lipídica extraída contém ácidos graxos C14 a C20, principalmente não saturados; os ácidos graxos saturados foram principalmente 14:0, 16:0 e 18:0. Não se encontrou correlação entre o tamanho da glândula e a natureza aquática/terrestre das espécies. A ablação da glândula não afetou a sobrevivência, peso corporal, alimentação e os níveis séricos de colesterol, lipídios totais ou cálcio depois de 32-120 dias. Discute-se o possível papel da glândula na proteção contra compostos lipofílicos. A função da glândula é ainda tema de controvérsia. Aceita-se que sua secreção confere às penas propriedades repelentes à água e as mantém flexíveis. Outras funções fisiológicas da secreção glandular podem estar associadas com a produção de feromonas, controle da higiene da plumagem, isolamento térmico e defesa contra predadores. Com relação à regulação endócrina da glândula, tem-se escassa informação, apresentando evidência de mecanismos de regulação de esteróides.