Featured Research

from universities, journals, and other organizations

Tongue makes the difference in how fish and mammals chew

Date:
July 3, 2011
Source:
Brown University
Summary:
New research shows that fish and mammals chew differently. Fish use tongue muscles to thrust food backward, while mammals use tongue muscles to position food for grinding. The evolutionary divergence is believed to have occurred with amphibians, though further research is needed to identify which species and when.

Chewing styles for different purposes. Fish use tongue muscles to thrust food backward, while mammals use tongue muscles to position food for grinding.
Credit: Image courtesy of Brown University

New research from Brown University shows that fish and mammals chew differently. Fish use tongue muscles to thrust food backward, while mammals use tongue muscles to position food for grinding. The evolutionary divergence is believed to have occurred with amphibians, though further research is needed to identify which species and when. Results are published in Integrative and Comparative Biology.

Evolution has made its marks -- large and small -- in innumerable patterns of life. New research from Brown University shows chewing has evolved too.

Researchers looked at muscles that control the movement of the jaw and tongue in fish and in mammals. They learned that fish use tongue muscles primarily to funnel the food farther into the mouth for processing, as if the morsel were an object in an assembly line. Mammals use tongue muscles to position the food, so that jaw muscles can best use teeth to chew the food.

Chewing styles for different purposes

Fish use tongue muscles to thrust food backward, while mammals use tongue muscles to position food for grinding.The difference in chewing shows that animals have changed the way they chew and digest their food and that evolution must have played a role.

"It's pretty clear that all of these animals chew, but the involvement of the tongue in chewing differs," said Nicolai Konow, a postdoctoral researcher at Brown and the lead author on the study, published in the journal of Integrative and Comparative Biology. "And that brings up the question of what the muscles associated with the tongue and the jaw are doing."

In 2008 and last year, Konow and colleagues published papers showing the chewing technique of bowfin, pike, and fish with tiny teeth on their tongues such as salmon and osteoglossomorphs (fish with bony tongues). In some of these species, the researchers showed that chewing begins with the tongue positioned in the upper mouth. Then the fish fires the muscle, called the sternohyoid, downward, retracting the tongue inward, before moving it forward again, and upward, to its original position in the upper mouth. With the fish facing left, the chewing cycle looks like an ellipse tilted at an angle, with the tongue moving in a clockwise direction.

The finding was bolstered by earlier research by other scientists that showed the same chewing pattern in other fish, including bichir (a freshwater fish in Africa), gar, and, importantly, lungfish, which is believed to represent an early stage in the transition of some species from exclusively water- to land-dwelling.

In this paper, Konow and his team studied how the muscles of three mammals acted during chewing: alpacas, goats, and pigs. They outfitted each with electrodes planted in the jaw and tongue muscles to pinpoint the activity of each set of muscles during chewing. The analysis indicated that the animals' tongues thrust forward, and upward, as they began to chew and then fell back, or retracted, to their original position. With the animals facing left, the tongue traces an ellipse in a counter-clockwise direction for each cycle.

The distinction between fish and mammal chewing is likely there for a reason, Konow said. With fish, the tongue's function is to transport the food quickly into and through the mouth, where, in many species, an extra set (or sets) of jaws will grind the food. In addition, the tongue moves oxygenated water through the mouth to the gills, helping the fish to breathe.

"That's why you want to constantly have that inward movement with the tongue," Konow explained.

Mammals, on the other hand, use their tongues to set the food in the right spot in the mouth to maximize chewing. But even among closely related species, there is a surprising difference: Herbivores, such as alpacas and goats, were less coordinated during chewing than omnivores, represented by the pigs. Cud-chewing animals were not as monotonously rhythmic in their chewing as many would believe.

"It is a puzzling finding," Konow said. "We think the herbivore needs the bolus (the soft mass of chewed food) to be in a precise place between each chew. So the tongue may be constantly moving around to make sure the bolus is in the right place between chews."

Next came the task of figuring out where, when and with what species the divergence in chewing emerged. Previous research by Anthony Herrel, a Belgian biologist now based at the Museum National D'Histoire Naturelle in Paris, showed that lizards fire their tongues forward and upward as they begin chewing, just like mammals. The thinking is that the transition likely occurred among amphibians. That makes sense, Konow said, and he plans to look next at amphibian chewing. "They're still locked to the water for reproduction," he said. "But you have some that become all terrestrial. And that's the next step on the evolutionary ladder."

Contributing authors include Herrel; Callum Ross from the University of Chicago; Susan Williams from Ohio University; Rebecca German from Johns Hopkins University; and Christopher Sanford and Chris Gintof from Hofstra University.

The U.S. National Institutes of Health and the U.S. National Science Foundation funded the research.


Story Source:

The above story is based on materials provided by Brown University. Note: Materials may be edited for content and length.


Journal Reference:

  1. N. Konow, A. Herrel, C. F. Ross, S. H. Williams, R. Z. German, C. P. J. Sanford, C. Gintof. Evolution of Muscle Activity Patterns Driving Motions of the Jaw and Hyoid during Chewing in Gnathostomes. Integrative and Comparative Biology, 2011; DOI: 10.1093/icb/icr040

Cite This Page:

Brown University. "Tongue makes the difference in how fish and mammals chew." ScienceDaily. ScienceDaily, 3 July 2011. <www.sciencedaily.com/releases/2011/06/110627123136.htm>.
Brown University. (2011, July 3). Tongue makes the difference in how fish and mammals chew. ScienceDaily. Retrieved April 16, 2014 from www.sciencedaily.com/releases/2011/06/110627123136.htm
Brown University. "Tongue makes the difference in how fish and mammals chew." ScienceDaily. www.sciencedaily.com/releases/2011/06/110627123136.htm (accessed April 16, 2014).

Share This



More Plants & Animals News

Wednesday, April 16, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Ebola Outbreak Now Linked To 121 Deaths

Ebola Outbreak Now Linked To 121 Deaths

Newsy (Apr. 15, 2014) The ebola virus outbreak in West Africa is now linked to 121 deaths. Health officials fear the virus will continue to spread in urban areas. Video provided by Newsy
Powered by NewsLook.com
In Washington, a Push to Sterilize Stray Cats

In Washington, a Push to Sterilize Stray Cats

AFP (Apr. 14, 2014) To curb the growing numbers of feral cats in the US capital, the Washington Humane Society is encouraging residents to set traps and bring the animals to a sterilization clinic, after which they are released.. Duration: 02:29 Video provided by AFP
Powered by NewsLook.com
After Attack, Officials Kill 5 Bears in Florida

After Attack, Officials Kill 5 Bears in Florida

AP (Apr. 14, 2014) Florida wildlife officials say they have killed five bears following an attack on a woman in a suburban subdivision in central Florida. Forty-five year-old Terri Frana was attacked by a large bear in her driveway Saturday. (April 14) Video provided by AP
Powered by NewsLook.com
Uruguay Opens Its First Cannabis Library

Uruguay Opens Its First Cannabis Library

AFP (Apr. 13, 2014) Uruguay opened its first Cannabis Library in Montevideo on Saturday, where people can come and read books on cannabis or take classes on how to grow the plant or even how to cook with it. Duration: 01:20 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins