Tongue Cuts Through Fish Scales

meet and mouth of a sea lamprey with a blurry background

Biological Strategy

Lampreys

AskNature Team

Image: T. Lawrence/Great Lakes Fishery Commission / Flickr / CC BY - Creative Commons Attribution alone

Physically Break Down Living Materials

Living materials are those that are part of living systems (whether currently or formerly alive). For example, a fallen log, although dead, is considered a living material. Breaking down or breaking up living materials is important for living systems that feed on them, as well as in facilitating the decomposition of organic matter. Breakdown increases the material’s surface area exposed to moisture, fungi, bacteria, and other living systems, many of which use enzymes and other chemicals to further break it down. But living materials can be difficult to break down because, for their own survival, their composition must provide support and protection. Therefore, living systems require mechanical means (such as grinding, tearing, or chewing) to manipulate these materials, as well as strong materials that can overcome resistance. For example, small beetles that chew through wood have large, strong jaws that enable them to cut through this tough material.

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Fish

Class Agnatha (“without jaws”), Class Chondrichthyes (“cartilage fish”), Superclass Osteichthyes (“bone fish”): Sharks, eels, snapper, hagfish

The fish are a diverse group, comprising multiple classes within Phylum Animalia. The most well-known classes are Chondrichthyes, which has sharks and rays, and superclass Osteichthyes, which has all bony fish like cod and tuna. Unlike other vertebrates, fish only live in water. They use special adaptations like fins, gills, and swim bladders to survive. Most are ectothermic, meaning their body temperature depends on the water temperature around them. Over half of all vertebrates are fish. They’re found from the bottom of the sea to high mountain lakes.

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The tongue of a lamprey can cut through fish scales and skin due to its abrasiveness.

“The lamprey uses a sucker-like jawless mouth to cling to the trout, and has a vicious abrasive tongue with which to gorge a hole in its host’s body. There it laps up the body fluids oozing from the wound.” (Foy and Oxford Scientific Films 1982:50)

“In some respects, the mechanics of feeding have not been adequately explained, although the part played by the tongue is better understood. This structure is supported by a lingual cartilage, which can be moved slightly in a forward direction by paired basilariglossus muscles, originating in the basilaris and inserted on to the cartilage. The cutting lobes of the tongue are supported by an apical cartilage to which they are attached by tendons. Both Dawson (1905) and Lanzing (1959) agree that a rasping effect is largely responsible for the initial destruction of host tissue, through a rocking motion of the apical part of the tongue, produced by the protractor and retractor systems. In addition to this rasping effect, Lanzing considered that the retraction of the tongue brings together the longitudinal laminae in a scissors-like action which would be effective in cutting the host tissues.” (Hardisty and Potter 1971:158)

Foy S, Oxford Scientific Films. The Grand Design: Form and Colour in Animals. Lingfield, Surrey, U.K.: BLA Publishing Limited for J. M. Dent & Sons Ltd, London; 1982. 238 p.
Hardisty MW; Potter IC. 1971. The biology of lampreys. Vol. 1 London: Academic Press. 423p.