Ingestion in Reptiles and Amphibians

Abstract

The feeding stages of prey capture, ingestion, processing, intraoral transport and swallowing are accomplished in different ways in different species of amphibians (caecilians, salamanders and frogs) and reptiles (crocodilians, turtles, tuatara, lizards, amphisbaeneans and snakes – birds have diverged so much from other reptile groups that they can be considered separately). The structural and ecological diversity of amphibians and reptiles is reflected in the diversity of their feeding systems.

Keywords: anatomy; biomechanics; caecilians; crocodilians; evolution; frogs; ingestion; lizards; prey capture; snakes; salamanders; swallowing; turtles; skull; tuatara

Figure 1.

Evolutionaryrelationships among terrestrial vertebrates (tetrapods). The ancestors oftetrapods were a now‐extinct group of fish that probably used suction tocapture and manipulate prey. Feeding form and function of the variousamphibian and reptile groups are discussed in the text. Scientific names forthe amphibian and reptile groups shown in the figure are as follows: frogs(Anura); caecilians (Gymnophiona); salamanders (Urodela);turtles (Testudines); alligators and crocodiles (Crocodylia); birds(Aves); tuatara (Rhynchocephalia); lizards and snakes (Squamata).

Figure 2.

Themechanics of suction feeding in an aquatic larval salamander. The generationof suction requires very rapid expansion of the mouth and throat (pharynx)cavities by retraction and depression of the hyobranchial skeleton (shaded).This creates a negative pressure within the mouth. When water rushes in toequilibrate inside and outside pressures, small prey items are drawn in alongwith it. After capture, the mouth is closed and the pharynx compressed so thatwater is expelled either posteriorly through open gill slits, or anteriorlythrough the teeth. A very similar system is used by all suction feedingtetrapods. (a) The skull and hyobranchial apparatus in lateral view, at reston the left and retracted on the right; (b) the skull and hyobranchialapparatus shown as mechanical units connected and moved by muscles (blacklines); (c) oblique view from below showing the movements of thehyobranchial apparatus in three dimensions. Reproduced with permission fromDeban and Wake (2000), copyright Academic Press/Harcourt, Inc.

Figure 3.

Hyolingualprojection in a salamander, Hydromantes supramontis(Plethodontidae). The projectile includes the tongue pad (enveloping a fly onthe rock) as well as the hyobranchial apparatus and retractor musculature.Tongue projection has evolved several times independently in salamanders andin frogs and also in chamaeleonid lizards. In chameleons, the tongue isprojected off an extended hyobranchial skeleton and in frogs the tongue isattached at the front and flipped over the lower jaw; the hyobranchialapparatus does not participate directly in projection. Photograph by StephenM. Deban. Reproduced with permission from Wake and Deban (2000), copyrightAcademic Press/Harcourt, Inc.

Figure 4.

Threestages of feeding in a small crocodile, Caimancrocodilus, based on X‐ray movies. The prey item is shown as astippled oval and the hyolingual apparatus (tongue plus hyobranchial skeleton)is shaded. Frames 1 to 4 for each sequence show the slow‐opening phase, frame5 is maximum gape, and frame 6 is the following jaws closed position. Frame 7shows the crushing phase in the killing/crushing sequence and thebeginning of the next jaw‐opening cycle in the other two sequences. Thenumbers represent elapsed time in milliseconds. Note that all stages offeeding require coordination of jaw and hyolingual movements, as is typicalfor most tetrapod feeding. Reproduced with permission from Cleuren and De Vree(2000), copyright Academic Press/Harcourt, Inc.

Figure 5.

Tongueprotrusion and lingual prey capture in an iguanian lizard (Pogonabarbata, Agamidae). During prey capture (ingestion), the tongueis protruded beyond the lower jaw and curled downward so that its dorsal (top)surface is presented toward the prey item. Long, sticky papillae provide anadhesive surface to which the prey adheres for rapid retraction into themouth. Reproduced with permission from Schwenk (2000b), copyright AcademicPress/Harcourt, Inc.

Figure 6.

A python(snake) skull showing adaptations for swallowing large prey. Most important isthe ability of the mandibles to separate at the front. Unlike most tetrapodsin which each half of the mandible is fused to the other by a tight jointcalled a symphysis, in snakes the halves remain unfused and joined only bysoft, elastic tissue (Sim). The effective length of the mandibles,and therefore the size of the gape, is also increased by adding to it mobileand elongate bones of the upper jaw, the quadrate (Qu) and supratemporal (St).These traits permit the jaws of ‘advanced’ snakes to spread verywide, enabling them to swallow large‐diameter prey (Dp). Inaddition, left and right upper jaw bones are independently mobile, so that thesnake can literally ‘walk’ its head over the prey item (a formof cranial kinesis). Reproduced with permission from Cundall and Greene(2000), copyright Academic Press/Harcourt, Inc.

close

Further Reading

Bels VL, Chardon M and Vandewalle P (1994) Advances in Comparative Environmental Physiology, vol. 18. Biomechanics of Feeding in Vertebrates. Berlin: Springer‐Verlag.

Bramble DM and Wake DB (1985) Feeding mechanisms of lower tetrapods. In: Hildebrand M, Bramble DM, Liem KF and Wake DB (eds) Functional Vertebrate Morphology, pp. 230–261. Cambridge, MA: Harvard University Press.

Cleuren J and De Vree F (2000) Feeding in crocodilians. In: Schwenk K (ed.) Feeding: Form, Function and Evolution in Tetrapod Vertebrates, pp. 337–358. San Diego: Academic Press.

Cundall D and Greene HW (2000) Feeding in snakes. In: Schwenk K (ed.) Feeding: Form, Function and Evolution in Tetrapod Vertebrates, pp. 293–334. San Diego: Academic Press.

Deban SM and Wake DB (2000) Aquatic feeding in salamanders. In: Schwenk K (ed.) Feeding: Form, Function and Evolution in Tetrapod Vertebrates, pp. 65–94. San Diego: Academic Press.

Lauder GV (1985) Aquatic feeding in lower vertebrates. In: Hildebrand M, Bramble DM, Liem KF and Wake DB (eds) Functional Vertebrate Morphology, pp. 210–229. Cambridge, MA: Harvard University Press.

Nishikawa KC (2000) Feeding in frogs. In: Schwenk K (ed.) Feeding: Form, Function and Evolution in Tetrapod Vertebrates, pp. 117–147. San Diego: Academic Press.

O’Reilly JC (2000) Feeding in caecilians. In: Schwenk K (ed.) Feeding: Form, Function and Evolution in Tetrapod Vertebrates, pp. 149–166. San Diego: Academic Press.

Schwenk K (2000a) An introduction to tetrapod feeding. In: Schwenk K (ed.) Feeding: Form, Function and Evolution in Tetrapod Vertebrates, pp. 21–61. San Diego: Academic Press.

Schwenk K (2000b) Feeding in lepidosaurs. In: Schwenk K (ed.) Feeding: Form, Function and Evolution in Tetrapod Vertebrates, pp. 173–291. San Diego: Academic Press.

Summers AP, Darouian KF, Richmond AM and Brainerd EL (1998) Kinematics of aquatic and terrestrial prey capture in Terrapene carolina, with implications for the evolution of feeding in cryptodire turtles. Journal of Experimental Zoology 281: 280–287.

Van Damme J and Aerts P (1997) Kinematics and functional morphology of aquatic feeding in Australian snake‐necked turtles (Pleurodira; Chelodina). Journal of Morphology 233: 113–125.

Wake DB and Deban SM (2000) Terrestrial feeding in salamanders. In: Schwenk K (ed.) Feeding: Form, Function and Evolution in Tetrapod Vertebrates, pp. 95–116. San Diego: Academic Press.

Wochesländer R, Hilgers H and Weisgram J (1999) Feeding mechanism of Testudo hermanni boettgeri (Chelonia, Cryptodira). Netherlands Journal of Zoology 49: 1–13.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Nishikawa, Kiisa, and Schwenk, Kurt(Jun 2001) Ingestion in Reptiles and Amphibians. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0001835]