Preen gland of the laughing dove (Streptopelia senegalensis aegyptiaca): Light and electron microscopic analysis.

This work reviews the microscopic anatomy of the preen gland in laughing dove (Streptopelia senegalensis aegyptiaca) using light, scanning, and transmission electron microscopes. The gland possessed two large pea-shaped lobes. The glandular lobules of each lobe were huddled in elliptical, triangle, round shapes, connected with each other by strands of connective tissue septae. The lobule was composed of glandular follicles, each follicle folded and enclosed by a sheath of connective tissue connected with the neighboring ones by interfollicular septae. The gland's parenchyma was coated with a dense connective tissue capsule composed of collagen, elastic, and reticular fibers. The secretory tubules were divided into peripheral tubules and central tubules. The central ones were located close to the major cavity and lined with thin epithelium, whereas the peripheral tubules were adjacent to the capsule and characterized by taller epithelium. The central secretory tubules were lined with four cell layers: flattened basal, large-sized polyhedral intermediate, and secretory cell layers, as well as a degenerative cells layer that formed of small cells with pale cytoplasm and pyknotic nuclei. Variable sizes and shapes of Herbst corpuscles were detected alongside the papillary duct and near the glandular lobe. Transmission electron microscopy view revealed that the cytoplasm of the intermediate cells contained a dense population of mitochondria, while the secretory and degenerative cells contained fewer mitochondria. In conclusion, these structures will be beneficial for understanding the habitat differences of laughing doves. RESEARCH HIGHLIGHTS: Grossly, the preen gland (PG) of the laughing dove formed of two large pea-shaped lobes. The glandular lobule was composed of glandular follicles, each follicle was folded and enclosed by a sheath of connective tissue connected with the neighboring ones by interfollicular septae. The central secretory tubules were lined with four cell layers: basal, intermediate, secretory, and degenerative cell layers. Variable sizes and shapes of Herbst corpuscles were detected alongside the papillary duct and near the glandular lobe of the PG. In transmission electron microscopic analysis, the cytoplasm of the intermediate cells contained a dense population of mitochondria, while the secretory and degenerative cells contained fewer mitochondria.