A fish that uses its hydrodynamic tongue to feed on land

• Published in: Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2015-04, Vol.282 (1805), p.1-7
• Main Authors: Michel, Krijn B., Heiss, Egon, Aerts, Peter, Van Wassenbergh, Sam
• Format: Article
• Language: English
• ISSN: 0962-8452; 1471-2954

To capture and swallow food on land, a sticky tongue supported by the hyoid and gill arch skeleton has evolved in land vertebrates from aquatic ancestors that used mouth-cavity-expanding actions of the hyoid to suck food into the mouth. However, the evolutionary pathway bridging this drastic shift in feeding machanism and associated hyoid motions remains unknown. Modern fish that feed on land may help to unravel the physical constraints and biomachanical solutions that led to terrestrialization of fish-feeding systems. Here, we show that the mudskipper emerges onto land with its mouth cavity filled with water, which it uses as a protruding and retracting 'hydrodynamic tongue' during the initial capture and subsequent intra-oral water to a sequence of compressive and expansive cranial motions that diverge from the general pattern known for suction feeding in fishes. However, the hyoid motion pattern showed a remarkable resemblance to newts during tongue prehension. Consequently, although alternative scenarios cannot be excluded, hydrodynamic tongue usage may be a transitional step onto which the evolution of adhesive mucosa and intrinsic lingual muscles can be added to gain further independence from water for terrestrial foraging.