The syrinx of the male mallard (Anas platyrhynchos): special anatomical features.

The aim of this study was to investigate the special anatomical and topographical features of the syrinx in male adult stock ducks (Anas platyrhynchos). The syrinx of the mallard is a tracheobronchial type, consisting of a tympanum, a pessulus, medial tympaniform membranes, interanular membranes, an interbronchial ligament (bronchidesmus), and bronchosyringeal cartilage semi-rings. Using a frozen sagittal section, it was possible to document the syringeal valve at the right lateral side of the tympanum. In the male stock duck the pessulus was massive and showed a longish oval, transparent area ventrally. The middle part of the pessulus had a nose-shaped process on its left side, on which the left medial tympaniform membrane originated. The left-sided, pear-shaped syringeal bulla was divided into a left major and right minor chamber by a double-walled, semilunar and opaque septum, approximately 5-6 mm in height. The first left and right C-shaped bronchosyringeal cartilage was more prominent than the other ones and showed partial ossification. In addition, the first left bronchosyringeal cartilage was obviously thicker than the right one. In conclusion, it can be stated that the syrinx in male adult mallards shows some notable specific anatomical features that might have an influence on vocalization. However, to understand the complex mechanism of vocalization in mallards, more investigations, especially obtained by sonography and endoscopy, will be needed.