Light and Scanning Electron Microscopic Study of the Structure of the Ostrich (Strutio camelus) Tongue

Abstract

The ostrich's tongue is situated in the posterior part of the oropharyngeal cavity and its length is only about a quarter of the beak cavity. The triangular shortened tongue has retained the usual division into the apex, the body and the root. There are no conical papillae between the body and the root of the tongue, and the presence of the flat fold with lateral processes sliding over the tongue root in the posterior part of the lingual body is a unique morphological feature. All lingual mucosa covers non-keratinised stratified epithelium, and the lamina propria of the mucosa is filled with mucous glands whose round or semilunar openings are found on both the dorsal and ventral surface of the tongue. The complex glands found in the lingual body are composed of alveoli and/or tubules. Moreover, simple tubular glands seen in the posterior part of the tongue root are an exception. Numerous observations have shown that the ostrich's tongue is a modified structure, though not a rudimentary one, whose main function is to produce the secretion moisturising the beak cavity surface and the ingested semidry plant food in this savannah species.

Gross anatomical features of the tongue, lingual skeleton and laryngeal mound of Rhea americana (Palaeognathae, Aves): morpho-functional considerations

“…A renewed interest has recently been shown in the morphology of the upper digestive tract of commercially important ratite species, particularly Struthio camelus (Linnaeus, 1758) (Tivane et al 2006;Porchescu 2007;Jackowiak and Ludwig 2008;Tadjalli et al 2008, Tivane 2008Guimarães et al 2009) and Dromaius novaehollandiae (Latham, 1790) (Crole and Soley 2009a, b, 2010a, b, 2011, as well as in the feeding mechanism employed by this group of birds (Bonga Tomlinson 2000;Gussekloo and Bout 2005).…”

“…These studies vary from gross morphological descriptions of the tongue of Rhea pennata (Orbigny, 1834) (Cho et al 1984), Casuarius casuarius (Linnaeus, 1758) (Gadow 1879;Pycraft 1900), S. camelus and D. novaehollandiae (Faraggiana 1933;Cho et al 1984;Bonga Tomlinson 2000) to macroscopic and microscopic studies of the tongue of S. camelus (Porchescu 2007;Jackowiak and Ludwig 2008;Tivane 2008;Guimarães et al 2009) and detailed studies (including light and scanning electron microscopy) of the tongue of D. novaehollandiae Soley 2009a, b, 2010b). In contrast, only minimal information on the morphology and function of the tongue (Owen 1835;Faraggiana 1933;Feder 1972;Bonga Tomlinson 2000;Gussekloo and Bout 2005;Santos et al 2011) and laryngeal mound (Owen 1835;Faraggiana 1933;Bonga Tomlinson 2000;Gussekloo and Bout 2005) of Rhea americana (Linnaeus, 1758) has been published.…”

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

“…For instance in the cormorant, the tongue has been reduced to a small, connective tissue structure and can be regarded as rudimentary (Jackowiak and Godynicki, 2006). In the ostrich, the short tongue has no mechanical papillae but contains numerous mucous glands for moistening the beak cavity, which may be an adaptation to semi-arid climatic conditions (Jackowiak and Ludwig, 2008).…”

Contrasting morphological evidence for the presence of taste buds in Dromaius novaehollandiae and Struthio camelus (Palaeognathae, Aves)

“…Evidence of a sense of taste in S. camelus has been addressed in a number of studies (Anon 1922;Brand and Gous 2006;Jackowiak and Ludwig 2008;Tivane 2008) and yielded only negative results (including the present study). However, the presence of chemoreception in the oropharynx of S. camelus, through mechanisms other than taste buds, has not been ruled out in the present study.…”

“…Various investigations have yielded negative results in both Struthio camelus (Linnaeus 1758) (Brand and Gous 2006;Jackowiak and Ludwig 2008;Tivane 2008) and Rhea americana (Linnaeus 1758) (Feder 1972;Santos et al 2011). However, in Dromaius novaehollandiae (Latham 1790), a structure resembling a taste bud was identified in the tongue root (Crole and Soley 2009) and, although not positively confirmed as such, was suggestive of a sense of taste in ratite species.…”