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Alien Teeth

Mar 05, 2010

Grass Carp 1I recently received some interesting photos of a “jawbone with teeth” found by a Missourian who was out searching for shed deer antlers. The e-mailer was seeking identification of the animal that produced such odd-looking teeth. Not only did the spacing and shape of the teeth look odd but there were a series of parallel grooves on the back side of each one. The teeth were as much a mystery to me as they were to the sender but luckily there are a number of biologists here who I can tap for information. Several indicated that the “jawbone” looked more like the bony parts of a fish than that of a mammal. When I showed them to a biologist in our Fisheries Division, he identified them immediately as the pharyngeal teeth of a grass carp.

Grass Carp 2The grass carp (Ctenopharyngodon idella) is an alien, or exotic, fish species whose native range is coastal rivers of Siberia and China. The genus name is Greek for “comb-like throat-teeth,” so those unusual teeth at the back of its throat gave rise to its Latin name. The species has been widely introduced into North America and is common in the Mississippi, Missouri and St. Francis rivers in Missouri. It has also been introduced into many ponds and lakes for bio-control of vegetation. It is a very large member of the minnow family that, in its native range, can reach a length of 4 feet and a weight of 100 pounds.

Grass Carp 3The adult fish has a preference for aquatic vegetation and has been reported to consume more than its own weight in vegetation in a day. The grooved pharyngeal teeth function to grind the vegetation prior to swallowing. One reason the teeth look so odd to us is that our first inclination is to think of teeth being found only in the mouth area, and those teeth don’t look like any we’ve seen in an animal’s mouth. Now that I know what they are, I don’t think I’ll ever forget them.

Photos by Patrick Winkler, Overland, Mo.

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