Microstructure of the Primary Remex of Owls (Strigiformes)

Abstract

An electron microscopic study of the microstructure of the primary remiges in owls (Strigiformes) was conducted using 13 species: Nyctea scandiaca, Bubo bubo, Asio otus, Otus scops, O. sunia, Aegolius funereus, Athene noctua, Glaucidium passerinum, Surnia ulula, Strux aluco, S. uralensis, S. nebulosa, and Tyto alba. Owls have a number of species-specific microstructural primary remex characteristics that are taxonomically important. First of all, these are the structural features of the pennaceous barb, which differ markedly not only at the ordinal, but also at the species level: cross-section configuration, pith architectonics in cross- and longitudinal sections, and cuticular barb structures. This work emphasizes that the identified elements are of taxonomic significance only when comparing the specific, strictly analogous sections of the barbs in different bird species. Based on the present study, we conclude that along with the typical elements of feather architectonics characteristic of representatives of other bird orders, the owls show a number of peculiar microstructural features. Thus, as the result of an analysis of the microstructure of the owls primary remex pennaceous barb vanule, the unique features of the distal barbules and the structure of the apical section of the barb with tightly adjacent and elongate proximal and distal barbules could be distinguished. These characteristics are revealed to cause a dense fleecy structure of the vane dorsal surface and the presence of a complex of peculiar “bunches” that form the cleft edge, i.e., the purely specific traits of the owls feather that are not found in representatives of any other bird orders we have investigated.