How Fish and Mammals Use Their Tongues When Chewing

According to the conclusions of a new scientific investigation, it would appear that fish and mammals use their tongues in entirely different ways when chewing. This is what primarily underlies the differences between the two types of creatures.

Researchers at the Brown University say that fish exhibit a preference towards using their tongues to thrust food backwards into their throats. Conversely, mammals tend to use their tongues to position their food better in the mouth, for grinding between the teeth.

Evolutionary biologists say that the two groups parted ways back when amphibians were their last common ancestor. Each of the groups then evolved to meet the demands of the environments it chose to develop in. Fish have no need to grind their food like mammals do.

Details of the new investigation have been published in the latest issue of the esteemed scientific journal Integrative and Comparative Biology. This is one of only a handful of studies assessing the origins and evolution of chewing.

In both fish and mammals, the jaw and tongue work together to achieve the desired result. For fish, the ultimate goal is to funnel food as far back into the mouth as possible. Mammals continuously use their tongue to push food onto powerful teeth, which the jaws then clench to grind the food.

“It’s pretty clear that all of these animals chew, but the involvement of the tongue in chewing differs. And that brings up the question of what the muscles associated with the tongue and the jaw are doing,” says Brown postdoctoral researcher Nicolai Konow, also the lead author on the study.

One of the reasons why fish are so quick to push their food through their mouths is the fact that the tongue also funnels oxygen-rich water to the gills, where the precious chemical is extracted, and used to keep the animal alive.

“That’s why you want to constantly have that inward movement with the tongue,” Konow explains.

In mammals, the tongue serves no such function. In fact, if humans for example, keep their foods in their mouths and chew it, their respiratory pathways are opened, and can function properly. If a fish were to chew at length, it would probably suffocate.

Konow conducted the new investigation with help from the US National Institutes of Health (NIH) and the National Science Foundation (NSF).

Experts from the University of Chicago, the Ohio University, the Johns Hopkins University and the Hofstra University were also a part of the work.