Functional Morphology of the Tongue in the Nutcracker (Nucifraga caryocatactes)

Abstract

The nutcracker Nucifraga caryocatactes belongs to a group of bird species that use their beak and tongue as tools for obtaining food, such as seeds from hard-to-reach cones or nuts from shells. The aim of the present study, carried out with a scanning electron microscope, was to define the morphological features of the tongue of the nutcracker, which seems to be adapted to its environment through specific methods of obtaining food. One of the characteristic features of the nutcracker's tongue is the unique structure of the anterior part of the tongue, which has two long and highly keratinized processes - a product of the renewable keratinized layer of the epithelium covering the ventral surface of the tongue. These dagger-like processes, which are a modified "lingual nail," take a major role in levering up and shelling seeds, which are transported over the short sulcus-shaped body of the tongue. A unique feature of the nutcracker's tongue is the groove separating the body from the root. Two rows of highly keratinized, mechanical, conical papillae are located at the junction of the body and the root. These papillae are mechanically protective elements for passing food particles in the form of seeds. Among lingual glands, only the posterior lingual glands on the root of the tongue have been observed. Their secretion agglutinates dry food before it is swallowed. Results of the present study indicate that the nutcracker's tongue is an efficient tool resembling a lever that is helpful in shelling seeds.

Anatomical and scanning electron microscopic investigations of the tongue and laryngeal entrance in the long‐legged buzzard (Buteo rufinus, cretzschmar, 1829)

“…The tongue in birds is divided into three parts as apex, lingual body, and radix (Getty,1975; Nickel et al,1977). The median groove located on the dorsal surface of the lingual body is distinguishing mark for white tailed eagle (Jackowiak and Godynicki,2005), black kite (Emura,2008), Egyptian goose (Hassan et al,2010), Middendorff's bean goose (Iwasaki et al,1997), and nutcracker (Jackowiak et al,2010). Similarly, a median groove was observed between apex and radix in long‐legged buzzard like white tailed eagle (Jackowiak and Godynicki,2005).…”

Functional Morphology of the Tongue in the Domestic Goose (Anser Anser f. Domestica)

“…In the chicken, feeding with grains, and in the carnivorous white-tailed eagle, there are numerous conical papillae at the end of the lingual body, pointing backwards to prevent food from moving back before swallowing (Iwasaki and Kobayashi, 1986;Jackowiak and Godynicki, 2006). Special structures observed in the nutcracker are two long keratinized plates, which grow from the ventral surface of the lingual apex and are used for extracting seeds from pine cones (Jackowiak et al, 2010). In the white-tailed eagle, the duck, and the bean goose, the median groove of the tongue is an important instrument to influence the direction of food transport (Iwasaki, 1997;Jackowiak and Godynicki, 2006).…”

Relating form to function in the hummingbird feeding apparatus

“…Avian lingual papillae are involved in manipulation of solid food (e.g., prey apprehension, holding, cutting, filtering, shelling, Iwasaki, Asami & Chiba, 1997; Kobayashi et al, 1998; Jackowiak et al, 2010; Jackowiak et al, 2011; Guimarães et al, 2014; Skieresz-Szewczyk & Jackowiak, 2014) and caudal intraoral transport of solid items (review in Parchami, Dehkordi & Bahadoran, 2010). Hummingbirds have remarkable feeding modes; first, about half of their diet (cf.…”